Title: Salmonella
1Salmonella
Praveen Rao, Sophia W. Riccardi, Danielle
Birrer Seminar in Nucleic Acids-Spring 2004 Prof.
Zubay
2Salmonella
- Overview
- History and Epidemiology
- Molecular Biology
- Clinical
- Weaponization
3Overview
- Salmonella is a rod-shaped, gram-negative,
facultative anaerobe in the family
Enterobacteriaceae
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5Salmonella Taxonomy
- The genus Salmonella is divided into two species,
S. enterica and S. bongori (CDC). - Over 2000 strains are grouped into S. enterica.
This species is further divided into six
subgroups based on host range specificity, which
also involves immunoreactivity of three surface
antigens, O, H and Vi. - All strains that are pathogenic to humans are in
species S. enterica, subgroup 1 (also called
enterica). - For example, the correct taxonomic name for
the organism that causes typhoid fever is
Salmonella enterica ssp. enterica, serovar typhi.
The simplified version Salmonella typhi. - Taxonomy has been revised several times, due to
the degree of DNA similarity between genomes. - For example, In the U.S., another legitimate
species name for enterica is choleraesuis.
6Other Facts
- Bacterium of 2501 identified strains, as of 2001.
Many different diseases are caused by more than
1,400 serotypes of this bacteria genus. - Salmonella derived from Dr. Salmon, a U.S.
veterinary surgeon, who discovered and isolated
the strain enterica or choleraesuis from the
intestine of a pig in 1885. - They are ingested orally by contaminated food or
water. Refrigeration prevents growth but does not
kill bacteria. Heating at 57-60C or 134-140F
has shown to be effective in killing the
bacteria. - Optimal growth 37C or 98.6F
7Disease-associated facts
- Salmonellosis Any of several bacterial
infections caused by species of Salmonella,
ranging from mild to serious infections. - Two main kinds in humans enteric fever
(typhoid and paratyphoid) and gastroenteritis
(non-typhoidal). - The main feature for S. diseases is the Type III
Secretion System, a needle-like multi-protein
complex that is associated with transferring
toxic proteins to host cells.
8Principal habitats in different types of
Salmonella
- Their principal habitat is the intestinal tracts
and bloodstream of humans, and in the intestinal
tracts of a wide variety of animals. - The WHO groups Salmonella into 3 types
- - Typhoidal (enteric) Salmonella
- (example S. typhi)
- ?causes typhoid and paratyphoid fever
- ?restricted to growth in human hosts
- ?principal habitat is in intestinal
tracts and the bloodstream
9- - Nontyphoidal Salmonella (example S.
enteritidis, S. typhimurium) -
- ?prevalent in gastrointestinal tracts of a
broad range of animals, including mammals,
reptiles, birds and insects. -
- ?cause a whole range of diseases in animals and
humans, mainly gastroenteritis. -
- ?usually transferred animal-to-person, through
certain food products fresh meat, poultry, eggs
and milk - - fruits, vegetables, seafood
-
- ?house and exotic pets, contamination through
contact with their feces
10 - Salmonella mostly restricted to certain
animals, such as cattle and pigs
infrequently in humans if these strains
do cause disease in humans, it is often
invasive and life-threatening.
11Salmonella
- Overview
- History and Epidemiology
- Molecular Biology
- Clinical
- Weaponization
12History of Salmonella
- Some historical figures are believed to have
been killed by - Salmonella
- Alexander the Great died mysteriously in 323
B.C. In 2001, a group of doctors at the
University of Maryland suggested that S. was the
cause of death, based on a description of
Alexanders symptoms written by the Greek author
Arrian of Nicomedia. - Prince Albert, the consort of Queen Victoria,
died of a Salmonella infection in 1861. During
the Victorian era, an estimated 50,000 cases per
year occurred in England.
13History
- Scholars working on the history of Jamestown,
Virginia, believe that a typhoid outbreak was
responsible for deaths of over 6000 settlers
between 1607 and 1624. - Typhoid Epidemic in the Spanish-American War
(1898) - - In all, 20,738 recruits contracted the
disease (82 of all sick soldiers), 1,590 died
(yielding a mortality rate of 7.7) - - It accounted for 87 of the total deaths
from disease. - - A significant number of these deaths
actually occurred at training areas in the
southeastern United States.
14History
- Typhoid outbreak in British camps during the
South African War (1899-1902) - - more soldiers suffered from typhoid fever
than from battle wounds. - - British troops lost 13,000 men to
typhoid, as compared to 8,000 battle deaths. - - outbreak was largely due to unsanitary towns
and farms throughout Africa, and polluted soil
was washed into the network of streams and rivers
during the rainy season. - Epidemic potential during a war prominent because
of the disposal problems of mens discharges. -
15History
- Similar problems of sanitation occurred in urban
areas. Many historic documents report about
typhoid outbreaks in England -
- - Most outbreaks that were reported could be
traced back to unsanitary water supplies or
polluted milk supplies. - - Dr. William Budd (1811-1880) documented his
observations, published them in the Lancet It
was known then that polluted water can spread the
disease. Budd urged for more disinfection and
water treatment -
- - reports show that in the nineteenth century,
population seemed powerless against this disease
even though they knew it was perfectly
preventable. -
- - with the introduction of piped and filtered
water supplies in most urban areas, its
prominence as a cause of death had diminished. -
16Salmonella vaccine
- First preventive measure against Salmonella was
discovered in 1896, as an antityphoid vaccine was
developed by the British surgeon Almroth Wright. - Vaccine consisted of heat-denatured, rudimentary
killed whole-cell bacteria said to be highly
effective. - Early wars -Immunization known, but new
- -the minimum dosage had not been clearly
refined - British War Office
authorized it on a voluntary basis only
- most soldiers refused to be
immunized because of - violent reaction
following injection possible contraction -
- Urban outbreaks opposition to any type of
vaccination a way around the problem of
sanitation and cleanliness. It was seen as a
disease of defective civilization due to
defective sanitation.
17Salmonella vaccine
- Between 1904-1914, the vaccine had become
respectable, in the scientific as well as
military world. - Vaccine was successfully used during World War I
to reduce the number of soldiers who died of
enteric fever (S. typhi).
18- Bottling typhoid vaccine, 1944
- Division of Biologic Products, U.S. Army of
Medical Department Professional Service Schools
- First typhoid inoculation, 1909 United States
Army Medical School
19History in the U.S.
- Typhoid Mary Mallon was the first famous
carrier of typhoid fever in the U.S. - Some individuals have natural immunity to
Salmonella. Known as chronic carriers, they
contract only mild or asymptomatic disease, but
still carry the bacteria in their body for a long
time. These cases serve as natural reservoir for
the disease. - Approximately 3 of persons infected with S.
typhi and 0.1 of those infected with
non-typhoidal salmonellae become chronic carriers
which may last for a few weeks to years. - One such case was Mary Mallon, who was hired as a
cook at several private homes in the new York
area in the early 1900s.
20History Mary Mallon
- Mary Mallon caused several typhoid outbreaks,
moving from household to household, always
disappearing before an epidemic could be traced
back to the particular household Mary was working
in. All together, she had worked for 7 families,
with 22 cases of typhoid and one death. - She was finally overtaken by the authorities in
1907 and committed to an isolation center on
North Brother Island, NY. There she stayed until
she was released in 1910, on the condition that
she never accept employment involving food
handling. - But She was found to work as a cook and to cause
typhoid outbreaks again. She was admitted back
to North Brother Island, where she lived until
her death in 1938.
21 Recent outbreaks
- More recently reported outbreaks in the U.S.
involve different kinds of Salmonella strains,
predominantly S. enteritidis and S. typhimurium. - In 1985, a salmonellosis (S. typhimurium)
outbreak involving 16,000 confirmed cases in 6
states by low fat milk and whole milk from one
Chicago dairy. - Largest outbreak of food-borne salmonellosis
in the U.S. Investigations discovered that raw
and pasteurized milk had been accidentally mixed.
22Oregon Intentional Contaminationof Restaurant
Salad Bars
In September of 1984, 10 area restaurants in The
Dalles, Oregon, were involved with outbreaks of
S. typhimurium
23Outbreaks
- January 2000 infant aged 1 month visited a
clinic with fever and diarrhea. A stool specimen
yielded Salmonella serotype Tennessee. One week
before illness onset, the infant's family moved
into a household that contained a bearded dragon
(i.e., Pogona vitticeps). - During June 2002, a child aged 21 months was
admitted to a hospital with fever, abdominal
cramps, and bloody diarrhea. Blood and stool
cultures yielded Salmonella serotype Poona (from
pet Iguana).
24Foodborne diseases
- WHO in 2000 that globally about 2.1 million
people died of foodborne illness - in industrialized countries, about 30 of people
suffer from foodborne diseases each year around
76 million cases occur each year, of which
325,000 result in hospitalization and 5,000 in
death. - (WHO, 2002)
25Why do foodborne diseases emerge ?
- Globalization of food supply for example,
multistate outbreaks of S. Poona infections
associated with eating Cantaloupe from Mexico
(2000-2002) - Unavoidable introduction of pathogens into new
geographic areas for example, vibrio cholerae
introduced into waters off the coast of southern
U.S. by cargo ship (1991). - Travelers, refugees and immigrants exposed to
unfamiliar foodborne hazards. - Changes in microorganisms evolution of new
pathogens, development of antibiotic resistance,
changes in the ability to survive in adverse
environmental conditions.
26Why do foodborne diseases emerge ?
- Changes in human population population of highly
susceptible people is expanding more likely to
succumb to bacterial infections. - Changes in lifestyle Great amount of people eat
prepared meals. In many countries, the boom in
food service establishments is not matched by
effective food safety education and control.
27Relative Frequency of the disease in the U.S.
- Estimate 2 to 4 million cases of salmonellosis
occur in the U.S. annually (reported and
unreported). Salmonella accounts for the
majority of food poisoning cases in the U.S - Latest numbers
- In 2002, a total of 32,308 cases were
reported from health laboratories in 50 states. - The national rate of reported isolates was
11.5 per 100,000 population. Shows decrease of
7 compared to 1992, slight increase of 2 from
2001.
28Epidemiology
- The most commonly reported serotypes, in history
and present - - S. typhi
- - S. enteritides and S. typhimurium
-
- The top 20 serotypes accounted for 80 of all
isolates reported in the U.S. in 2001.
29Top 15 Salmonella Serotype list in the U.S., 2001
Country, Institution, Biological origin Total Serot ped Rank Serotype Count of Total Serotyped
U.S.A., Centers of Disease Control, Control and Prevention-FDDB Epi, 2001, Human 31,675 1 Typhimurium 6,999 22.1
  2 Enteridites 5,614 17.7
  3 Newport 3,158 10
  4 Heidelberg 1,884 5.9
  5 Javiana 1,067 3.4
  6 Montevideo 626 2
  7 Oranienburg 595 1.9
  8 Muenchen 583 1.8
  9 Thompson 514 1.6
  10 Saintpaul 469 1.5
  11 Paratyphi B tartrate positive 466 1.5
  12 Infantis 440 1.4
  13 Braenderup 388 1.2
  14 Agona 370 1.2
  15 Typhi 343 1.1
30EpidemiologyS. typhi (typhoidal Samonella)
- Causes enteric fever
- Have no known hosts other than humans.
- Transmission through close contact with infected
or chronic carriers. While direct
person-to-person transmission through the
fecal-oral route is rare, most cases of disease
result from digestion of contaminated food or
water. - Since improvements in food handling, piped and
filtered water supplies as well as water/sewage
treatment have been made, enteric fever has
become relatively rare in developed countries.
31- However, typhoid fever is still a big
health-problem in developing countries. - The WHO estimates that there are worldwide about
16 million of clinical cases annually, of which
about 600,000 result in death. In comparison,
about 400 cases occur each year in the U.S., and
70 of these cases are acquired while traveling
internationally.
32Salmonella typhi in developing countries
- Contaminated water is a common cause in the
spread of typhoid fever. At the time of rain,
the contaminated surface water further
contaminates water supplies. - Severity, Morbidity and complication rate is much
higher than in Europe and North America due to
lack of antibiotics supply, water filtration and
treatment, sterilization of water and sanitation.
33S. Typhi in the U.S.
- Almost 30 of reported cases in the U.S. are
domestically acquired. - Although most cases are sporadic, large outbreaks
do occur. - For example, outbreak linked to contaminated
orange juice in N. Y.,
caused by a previously unknown chronic carrier
(1991). - Multi-drug resistance
- recent trend toward an increased incidence of
multi-drug resistant S. typhi in developing
countries is reflected by increase in the
proportion of U.S. cases 0.6 in 1985-1989 to
1.2 in 1990-1994.
34Epidemiology
- S. enteriditis and typhimurium (non-typhoidal
S.) -
- - are the 2 top serotypes in the U.S. since
1980s -
- - cause gastroenteritis following ingestion of
the bacteria on or in food or on fingers and
other objects -
- - cause the majority of cases of zoonotic
salmonellosis in many countries. -
35Salmonella Enteritidis
- Humpty Dumpty
- by R. Wayne Edwards January 1999
-
- Humpty Dumpty lay on the groundA crushed and
broken fella.No one wanted to put him
together'Cause he had salmonella.
- transmitted to humans by contaminated foods of
animal origin, predominantly eggs. Raw eaten or
undercooked eggs that have been infected in the
hens ovaries can cause gastroenteritis
36Salmonella Enteritidis Infections, United States,
19851999
- During the 1980s, illness related to contaminated
eggs occurred most frequently in the northeastern
United States, but now it is increasing in other
parts of the country as well.
37- CDC, 2002 In the Northeast, approximately one in
10,000 eggs may be internally contaminated one
in 50 average consumers could be exposed to a
contaminated egg each year. - In 1995 high of 3.9 per 100,000 population,
- In 1999 1.98 per 100,000, rate still
decreasing due to prevention and control efforts
by the government.
38S. typhimurium
- has been reported increasingly frequently as the
cause of human and animal salmonellosis since
1990, due to antibiotic resistance - Predominant multi-drug resistant strain DT 104,
which initially emerged in cattle in England,
1988 - In 1997, the WHO stated that some countries in
Europe had a staggering 20-fold increase in
incidences between 1980 and 1997, and a 5-fold
increase in the U.S. between 1974 and 1994, due
to antibiotic resistant strains - intensive animal maintenance.
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40Epidemic measures
- Salmonellosis is a reportable disease.
- An intensive search should be conducted for
the source of an infection and for the means
(food or water) by which the infection was
transmitted. - Samples of blood can be taken immediately for
confirmation and for testing for antibiotic
sensitivity. - Samples of stool or urine may be taken after
one week of onset for effective confirmation. - Food and water samples should be taken from
suspected sources of the outbreak. It is
recommended to organize temporary water
purification and sanitation facilities until
longer term measures can be implemented.
41Cost Estimates
- The cost per reported case of human salmonellosis
range from US 100 to 1300 in North America and
Europe. - The costs associated with individual outbreaks in
North America and Europe range from around - 60,000 to more than 20 Million.
- The total annual cost in the U.S. is estimated a
total of almost 400 Million.
42Salmonella
- Overview
- History and Epidemiology
- Molecular Biology
- Clinical
- Weaponization
43Salmonella Microbiology
44Classification
- Enterobacteria
- Gram-negative
- Facultative anaerobes
- Glucose-fermenting
- Straight, rod
- 2-3 µm in length
- Flagellated
- Many serovars
- Typhi
- Typhimurium
- Enteriditis
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46LPS on Surface
- Lipopolysaccharide
- Protective outer layer of most strains
- (not S. typhi)
- Coded for by rfb locus on chromosome
- Lipid core of LPS highly conserved across
serovars, but polysaccharide side chains are
highly polymorphic (nature of rfb gene)
47LPS (cont.)
- Memory immune response and antibodies directed
against LPS - Polymorphic nature of side chains is advantageous
for bacteria - Since Typhi has outer capsule, this infection is
worse.
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49Infection
- Ingestion of contaminated food or water
- Passes through mucosa of intestine to epithelial
cells - Causes membrane ruffling
- Releases effector proteins through Type III
Secretion system - Endocytosis
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51Salmonella Entry
52Membrane Ruffling
53Virulence Factors
- Genes for virulence factors cluster in
pathogenicity islands (PI) - Genes acquired through lateral transfer
- Bacteriophage and transposon insertion sequences
flank PI - Maybe vehicles for transfer of PI to Salmonella
at one time - Acquisition of PI enhances virulence of bacteria
54Horizontal Transfer
- Transformation
- Uptake of naked DNA
- Mediates exchange of any part of DNA
- Conjugation
- F to F-
- Requires cell to cell contact conjugation
bridge - Transduction
- Transfer of DNA by a phage
- New phage viral coat with bacterial DNA
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56Salmonella Pathogenicity Islands
- Salmonella Pathogenicity Island 1 (SPI-1)
- entry into intestinal epithelium
- Enables pathogen to exploit host intestinal
environment
- Salmonella Pathogenicity Island 2 (SPI-2)
- intracellular bacterial replication and
initiation of systemic infection - Do not influence enteropathogenesis to any great
extent
57Type III Secretion System (TTSS)
- Main way Salmonella delivers virulence factors to
host - Made up of 20 proteins
- Assemble in step-wise order
- PrgI is a needle structure extended by protein
base, forms a channel to host
PrgI
58Salmonella-host Interaction
- Two forms of TTSS
- One encoded on SPI-1, other on SPI-2
- SPI-1 TTSS probably causes initial interaction
- Starts bacteria-mediated endocytosis
- Entry activates SPI-2 TTSS to cause thorough
infection
59Membrane Ruffling
- Cytoskeleton-associated proteins relocate to site
of bacterial entry - Bacterial effector proteins trigger cytoskeleton
rearrangements - Apical membrane surface undergoes structural
changes, resembling ruffling - This triggers endocytosis into vesicles
- Slightly different from receptor-mediated
endocytosis
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61Salmonella Containing Vesicle
- After ingestion, Salmonella enters a SCV through
bacteria-mediated endocytosis - Lives and multiplies in SCV
- Very little known about SCV or how bacteria exist
inside - A method to avoid host immune response
- Phagosome maturing SCV
62SPI-1 Effector Proteins
- SipA
- Binds actin and stabilizes filaments
- Allows actin to polymerize more easily
- Maximizes efficiency of Salmonella invasion
- SipC
- Aides in entry of other SPI-1 effector proteins
- Activtes G-actin to form F-actin, then polymerize
- Aides in cytoskeleton rearrangements in membrane
ruffling
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64SopB
- Main virulence factor
- Encoded by SPI-5
- An enterotoxin associated with SPI-1 TTSS
- Induces an increase in concentration of cellular
inositol polyphosphate - Increased chloride secretion into lumen
- Na follows to balance charge
- Water follow to balance osmolarity
diarrhea
65SPI-2 TTSS
- Activated once bacteria enters cell
- Necessary for systemic infection
- SPI-2 TTSS secretes effector proteins from
phagosome into cytosol - Interfere with maturation of phagosome
- No fusion with lysosome
- How Salmonella avoids degredation in cell
66Flagella
- Another antigen
- Host cytotoxic T-cell response directed against
flagellar epitopes - N- and C- termini are highly conserved
- Middle of flagellum is variable
67Phase I / II Flagella
- Operon encoding Phase I flagella also encodes for
a protein that represses trascription of Phase II - The switch mediated by an enzyme that inhibits
Phase I, allowing Phase II - May help Salmonella avoid cell-mediated immune
response
68Tumor Necrosis Factor-a
- Flagella from S. Typhimurium induces expression
of TNF-a through cell-mediated reponse - Phase II flagella are less-potent inducers
- Switching mechanism may provide bacteria with a
way to down-regulate inflammatory response within
host
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70Immune Response
- White blood cells recognize trigger T cells, B
cells - Two types of B cells one to attack now, one for
memory - Macrophages and neutrophils attack bacteria,
secrete interleukins, causing cell-mediated
response by T-cells - Antibodies from B cells attach to bacteria,
allowing cytotoxic T cells, macrophages, and
neutrophils to kill the organism
71Inside Macrophages
- SPI-2 TTSS works in macrophages as well
- Bacterium produces enzymes that inactivte toxic
macrophage compounds - Homocysteine (Nitric Oxide antagonist)
- Superoxide dismutase (inactivates reactive
peroxides) - Salmonella must produce additional factors to
survive limited nutrient base - Allows bacteria to travel throughout body,
causing systemic infection (only in S. typhi)
72Septicemia
- Invasion of bloodstream
- spv genes causes detachment of cells to ECM and
apoptosis - Spreads infection
- Bacteria can enter bloodstream and lymphatic
system - Main cause of death by Salmonella
73How do we respond?
- Microbiological view
- Vaccines
- Dam
- Antibiotics
74Salmonella Vaccine Strategy
- Delete chromosomal regions that code for
independent and essential functions. This results
in - - low probability of acquiring both traits
- - both traits
- aro genes aromatic compound biosynthesis
- pur genes purine metabolism biosynthesis
- Deletion strains
- - can be grown on complete medium in lab
- - in vivo, growth is reduced
- - only a low level of infection is established
- - immune system can mount a response
- Vaccine suitable for humans and mice, chickens,
sheep, cattle
75DNA adenine methylase (Dam)
- Enzyme that methylates specific adenine residues
in Salmonella genome - Disrupts regulation of DNA replication and repair
- Regulates expression of about 20 bacterial genes
active during infection - Dam (-) mutants are not virulent
- Good antimicrobial potential
- Current hot topic of research
76Antibiotics
- Antibiotics are selective poisons
- Do not harm body cells
- Target different aspects of bacteria, such as
ability to synthesize cell wall, or metabolism - MIC Minimum Inhibitory Concentration
- the minimum amount of agent needed to inhibit the
growth of an organism
77Antibiotic Resistance
- Bacteria can counteract antibiotics by
- Preventing antibiotic from getting to target
- Changing the target
- Destroy the antibiotic
- Bacteria can acquire resistance
- Horizontal transfer from another bacteria
- Vertical transfer due to natural selection
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80Salmonella
- Overview
- History and Epidemiology
- Molecular Biology
- Clinical
- Weaponization
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82How Do You Catch Salmonella?
- Food borne
- Transmitted via improperly prepared, previously
contaminated food or water - - Meat poultry, wild birds, pork
- - Dairy eggs
- Pet turtles and lizards
83How does Salmonella affect the body?
- Three clinical forms of salmonellosis
- - Gastroenteritis (S. typhimurium)
- - Septicemia (S. Choleraesius)
- - Enteric Fevers (i.e. S. typhi Typhoid Fever)
84Who Can Be Infected?
- Everyone
- Especially the elderly, infants,
immunocompromised patients (AIDS, sickle cell
anemia)
85Factors Increasing Susceptibility
86Identification I
- Laboratory identification of genus Salmonella
biochemical serological tests - HOW?
- - stool or blood specimens are plated on agar
media (bismuth sulfite, green agars, MacConkey) - Suspect colonies further analyzed by triple sugar
iron agar/ or lysine-iron agar - - confirmed by antigenic analysis of O (somatic)
and H (flagellar) antigens Test for antigens
87Identification II
- Use phenol red test
- - testing for lactic acid production
- - if negative, diagnose (presence of red
spots surrounded by a bright red zone)
Salmonella typhimurium
88Nontyphoidal Salmonella
- General Incubation 6 hrs-10 days Duration 2-7
days - Infective Dose usually millions to billions of
cells - Transmission occurs via contaminated food and
water - Reservoir
- a) multiple animal reservoirs
- b) mainly from poultry and eggs (80 cases from
eggs) - c) fresh produce and exotic pets are also a
source of contamination (gt 90 of reptile stool
contain salmonella bacterium) small turtles ban.
- General Symptoms diarrhea with fever, abdominal
cramps, nausea and sometimes vomiting
89Nontyphoidal Salmonella
- Caused by S. typhimurium and S. enteritidis
- Rainy season of tropical climates Warm season of
temperate climates - Growing rapidly in the U.S. five-fold increase
between 1974-1994 - Centralization of food processing makes
nontyphoidal salmonellosis particularly prevalent
in developing countries - Resistance is a concern, especially with
multi-drug resistant S. Typhimurium known as
Definitive Type 104 (DT 104)
90Nontyphoidal Salmonella Gastroenteritis
- Incubation 8-48 hrs Duration 3-7 days for
diarrhea 72 hrs. for fever - Inoculum large
- Limited to GI tract
- Symptoms include diarrhea, nausea, abdominal
cramps and fevers of 100.5-102.2ºF. Also
accompanied by loose, bloody stool
Pseudoappendicitis (rare) - Stool culture will remain positive for 4-5 weeks
- lt 1 will become carriers
91Nontyphoidal SalmonellaBacteremia and
Endovascular Infections
- 5 develop septicemia 5-10 of septicemia
patients develop localized infections - Endocarditis Salmonella often infect vascular
sites preexisting heart valve disease risk
factor - Arteritis Elderly patients with a history of
back/chest prolonged fever or abdominal pain
proceeding gastroenteritis are particularly at
risk. - - Both are rare, but can cause complications
that may lead - to death
92Septicemia
- Serotype S. choleraesius causes septicemia
- - prolonged state of fever, chills, anorexia,
and anemia - - lesions in other tissues
- - septic chock, death
93Incidence of S. Enteritidis
94Nontyphoidal SalmonellosisLocalized Infections
- INTRAABDOMINAL INFECTIONS
- Rare, usually manifested as liver or spleen
abscesses - Risk factors hepatobiliary, abdominal
abnormalities, sickle cell disease - Treatment surgery to correct anatomic damages
and drain abscesses - CENTRAL NERVOUS SYSTEM INFECTIONS
- Usually meningitis (in neonates, present with
severe symptoms e.g. seizures, hydrocephalous,
mental retardation, paralysis) or cerebral
abscesses - PULMONARY INFECTIONS
- Usually lobar pneumonia
- Risk factors preexisting lung abnormalities,
sickle cell disease, glucocorticoid usage
95Typhoidal Salmonellosis Enteric Fever
- Incubation 7-14 days after ingestion Duration
several days - Infective Dose 105 organisms
- Symptoms
- a) 1st week slowly increasing fever, headache,
malaise, bronchitis - b) 2nd week Apathy, Anorexia, confusion, stupor
- c) 3rd week rose spots (1-2 mm diameter on the
skin) duration 2-5 days, variable GI symptoms,
such as abdominal tenderness (majority),
abdominal pain (20-40 of cases) and diarrhea
enlargement of the spleen/liver, nose bleeds, and
bradycardia - neuropsychiatric symptoms delirium and mental
confusion - Long term effects arthritis
96Typhoidal Salmonellosis
- Late stage complications include intestinal
perforation and gastrointestinal hemorrhage - Immediate care such as increase antibacterial
medications or surgical resection of bowel - Other rare complications include inflammation of
the pancreas, endocardium, perocardium,
myocardium, testes, liver, meninges, kidneys,
joints, bones, lungs and parotid gland and
hepatic/splenic abscesses - In general, symptoms of paratyphoid fever are
similar to typhoid fever, but milder with a lower
mortality rate - Majority of bacteria gone from stool in 8 weeks
However, 1-5 become asymptomatic chronic
carriers gallbladder is the primary source of
bacterium
97Typhoidal Salmonella
Chest PA view shows pleural effusion, left lower
pulmonary lobe atelectasis, medial and downward
shift of bowel gas, and an increase in the
air-fluid level in the abdomen
98Pictures
(A)
(B)
(A) In sub-acute infections, multiple white to
yellow foci occur in the liver, spleen is
enlarged, and mesenteric lymph nodes may be
enlarged (B) Histopathological examination may
reveal necrotizing splenitis and hepatitis, with
necrotic foci often accompanied by colonies of
bacteria (arrow in right photo).
99Treatment of Typhoidal Salmonellosis
- Third generation cephalosporins or quinolones is
the current treatment - IV or IM ceftriaxone (1-2g) is also prescribed
usually 10-14 days (5-7 days for uncomplicated
cases) - Multi Drug Resistant (MDR) strains of S. typhi
quinolones are the only effective oral treatment - Nalidixic acid resistant S. typhi (NARST) must be
tested for sensitivity to determine course of
treatment - Sever typhoid fever (altered consciousness,
septic shock) dexamethasone treatment - Chronic carriers 6 weeks of treatment with
either oral amoxicillin, ciprofloxacin,
norfloxacin - Surgical intervention to remove damaged cells
100Prevention
- Typhoidal S.
- - Generally treated with antibiotics
- - vaccinations available the CDC currently
recommends vaccination for persons traveling to
developing countries - - Education of general public, especially in
developing countries identification of all
carriers and sources of contamination of water
supplies - - avoid risky foods drinks
- buy bottled water or boil water for at least
1 minute - COOK and CLEAN food thoroughly, avoid raw
vegetables and fruits - - WASH YOUR HANDS WITH SOAP AND WATER!!!
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102- Preventive measures for non-typhoidal S.
-
- - pasteurization of milk-products Eggs from
known infected commercial flocks will be
pasteurized instead of being sold as grade A
shell eggs. -
- - tracebacks, on-farm testing, quality assurance
programs, regulations regarding refrigeration,
educational messages for safe handling and
cooking of eggs - - Cross-contamination uncooked contaminated
foods kept separate from cooked, ready-to-eat
foods.
103Salmonella Vaccines I
- Poultry vaccine MeganVac 1
-
- - applied to baby chicks via drinking water and
cattle. It stimulates immunity in the chickens,
preventing Salmonella infection during the
growing period which may result in contamination
and subsequent food borne infection of humans - - targets S. Enteritidis
- - Salmonella infection is stopped at lower
levels of the food chain will mean increased
productivity for the farmer and a break in the
cycle of Salmonella transmission from animals Ã
humans
104Salmonella Vaccines II
- Today, three types of Typhoid Vaccines are
available -
- (1) inactivated whole-cell vaccine 2 doses/
4wks. Apart single booster dose recommended
every 3 years -
- (2) Ty21a a live, attenuated S. typhi vaccine.
Administered orally (4 doses). Efficacy 7 years -
- (3) Vi polysaccharide vaccine from purified Vi
polysaccharide from S. typhi. Administered
subcutaneously or intramuscularly. To maintain
protection, revaccination recommended every 3
years. - These vaccines have been shown be 70-90
effective.
105Salmonella
- Overview
- History and Epidemiology
- Molecular Biology
- Clinical
- Weaponization
106Salmonella as A Bioweapon?
107CDC classification
- Category B agent includes microorganisms that
are moderately easy to disseminate, have moderate
morbidity (i.e., ability to cause disease) and
low mortality, but require enhanced disease
surveillance. - Biosafety Level 2
- Risk Level 2 associated with human disease that
is rarely serious and prophylactic intervention
is often available. - 9 different species Salmonella arizonae,
cholerasuis, enteritidis, gallinarum-pullorum,
meleagridis, paratyphi (Type A,B,C), spp., typhi,
and typhimurium - Salmonella typhi is the only species that
requires import and/or export permit from CDC
and/or Department of Commerce has high droplet
or aerosol production potential
108WHO Global Salm Surv (GSS)
- GSS is an international Salmonella surveillance
program initiated in January 2002. It collects
annual summary data from member institutions all
over the world. - The goal is to enhance the quality of Salmonella
surveillance, serotyping and antimicrobial
resistance testing and leading local
interventions that reduce the human health burden
of Salmonella. - A total of 138 laboratories were enrolled in the
GSS in September 2003.
109Salmonella as a Bioterrorist Weapon What states
are most at risk?
- The states most vulnerable to terrorist attack on
the agricultural sector are those with several or
most of the following attributes - High density, large agricultural area
- heavy reliance on monoculture of a restricted
range of genotypes - major agricultural exporter, or heavily dependent
on a few domestic agricultural products - suffering serious domestic unrest, or the target
of international terrorism, or unfriendly
neighbor of states likely to be developing BW
programs
110First Use of Salmonella as a Bioterrorist Weapon
- From 1932-1945, Japan conducted biological
warfare experiments in Manchuria - At Unit 731, a biological warfare research
facility, prisoners were infected with Salmonella
typhosa among other biological agents - Additionally, a number of Chinese cities were
attacked. The Japanese contaminated water
supplies and food items with Salmonella. Cultures
were also tossed into homes and sprayed from
aircraft - Due to inadequate preparation, training, and/or
lack of proper equipment, the Chekiang Campaign
in 1942 led to about 10,000 biological casualties
and 1,700 deaths among the Japanese troops.
111- Oregon 1984 a religious cult known as the
Rajneeshees, a Buddhist cult sought to run - the whole country by wining the local election in
1984 using salmonella bacteria. They - brewed a "salsa" of salmonella and sprinkled it
on the town's restaurant salad bars. Ten - restaurants were hit and more than 700 people got
sick. - First large scale bioterrorism attack on
American soil - A communitywide outbreak of salmonellosis
resulted at least 751 cases were - documented in a county that typically reports
fewer than five cases per year. - Health officials soon pinned down salmonella as
the cause of the sudden outbreak, but - put the blame on food handlers. In 1984, who
could have imagined bioterrorism? Â - caused by S. typhimurium as this type
112 Salmonella as a Bioterrorist Weapon
- Wide distribution of food contaminated food
produced in one country can cause illness in
other countries - Traceability
- Antimicrobial resistance strains of
- Salmonella are being found that have
- multiple drug resistance
- Capacity building Salm-gene project
- used to enhance outbreak detection by
- routinely sub-typing certain salmonellas
- using molecular methods
113Salmonella as a Bioterrorist Weapon
- Contaminating unguarded food supplies
- Some terrorist acts may be designed purely to
spread panic contaminating the food supply could
bring economic and agricultural production to a
standstill - EX. If numerous food-borne outbreaks occurred
across the country, people would soon fear their
meals - Unfortunately, people have reason to worry all
these contaminations have occurred naturally
every year. If Mother Nature can do this
repeatedly, then a terrorist should have no
problem recreating these outbreaks over and over
in any number of American cities.
114Salmonella as a Bioterrorist Weapon
- readily accessible and easy to grow or make
- Centralized food production largely unmonitored
food supply food that is tampered with can be
widely quickly distributed - Terrorist groups could use infectious disease
agents to confuse public health officials into
believing that outbreaks are naturally occurring
it is estimated that 1.4 million salmonella
infections occur each year, but the CDC gets
reports of only about 38,000 annually - According to the Centers for Disease Control
(CDC), only 32 of the reported outbreaks have a
known etiology.
115Salmonella as a Bioterrorist Weapon
- No food product is safe vegetables and fruits
are the easiest to contaminate. Fresh-produce
wholesalers and distributors are notorious for
employing illegal immigrants and not checking
their background information. - Even processed foods arent safe Terrorists
could use heat-stable toxins that would survive
the packaging process. - As more of our food becomes imported, especially
hard-to-clean off-season fruits and vegetables,
bioterrorists dont even have to be inside the
United States to do damage
116Salmonella as a Bioterrorist Weapon Who might be
tempted to initiate an attack on the agricultural
sector?
- Terrorist groups might be interested in
agricultural bioweapons for a variety of reasons
-
- 1. international terrorist organizations cause
harm/injury to enemy states or peoples - - in an ideologically-motivated terrorist
attack there would be willing assumption of
responsibility by the perpetrator OR an attempt
to disguise the outbreak as natural. -
- 2. Extreme activist groups
- - EX. anti-GMO groups for their potential value
in deterring farmers from the use of genetically
engineered crops or animals
117Salmonella as a Bioterrorist Weapon What goals
might an attack on the agricultural sector serve?
- Food attack by a terrorist group initiate
point-source epidemics using available Salmonella
strains - Destabilize a government by initiating food
shortages/unemployment the potential for immense
economic damage due to contamination of the food
supply - Alter supply and demand patterns for a commodity
an outbreak can trigger the imposition of trade
restrictions. This is turn would open up or close
markets for others.
118Salmonella as a Bioterrorist Weapon What are the
special features of an attack on the agricultural
sector?
- Salmonella is not hazardous to perpetrators
easy to produce, stockpile, and disseminate - Few technical obstacles to weaponization it
would not be difficult to obtain Salmonella
strains on the open market. - Low security of vulnerable targets Fields,
supermarkets, restaurants have essentially no
security at all. - Point source to mimic natural introduction
Because of the high incidence of
naturally-occurring diseases, a deliberately
instigated outbreak could be mistaken for a
natural one - Multiple point source outbreaks can be initiated
by contaminating imported feed or fertilizer,
without even entering the country allows the
possibility of initiating multiple outbreaks over
a large geographic area, in a way that mimics a
natural event
119Salmonella Dilemma
- Dissemination of genomic knowledge of salmonella
can facilitate bio-weapons development - Alternative 1 Restrict dissemination of genomic
knowledge - - short term hinders development of a
super-Salmonella terror weapon - - long run leaves us at the mercy of multi-drug
resistant salmonella strains ranging from
incapacitating to lethal - Alternative 2 Disseminate genomic knowledge, but
support development of salmonella specific-drugs - - knowledge may provide a terrorist org. with
the ability to develop super-Salmonella terror
weapons, but it provides us with the opportunity
to defend against all salmonella infection.
120Combating Salmonella Bioterrorism
- Establish a national disease surveillance system
that could not only help uncover a terrorist
attack but also recognize naturally occurring
outbreaks that now go undetected - New technology creating a diagnostic gene chip
covering all major diseases could give the health
care provider instant diagnoses. Similar gene
chips could monitor the health of livestock,
poultry, and crops. Chips could be used during
various steps of food processing to ensure
quality control and food safety.
121Lines of Defense
- Food processors should limit access to their
production, storage and packaging areas
rerouting traffic, installing locks - Randomized safety checkpoints will increase fear
of detection - COSTS
- Increase work force
- Sampling and test costs
- Record keeping
122Government Action
- CDC monitors the frequency of Salmonella
infections in the country and assists the local
and State Health Departments to investigate
outbreaks and devise control measures - FDA inspects imported foods, milk pasteurization
plants, promotes better food preparation
techniques in restaurants and food processing
plants, and regulates the sale of turtles and it
also regulates the use of specific antibiotics as
growth promotants in food animals - USDA monitors the health of food animals,
inspects egg pasteurization plants, and is
responsible for the quality of slaughtered and
processed meat. - EPA regulates and monitors the safety of our
drinking water supplies.
123Biological Weapon Prevention
- BTWC (Biological and Toxin Weapons Convention)
drafted in 1972 - - intended to prevent the development,
production and stockpiling of biological weapons - - pathogens or toxins in quantities that have no
justification for protective or peaceful services
are to be eliminated - - today, 159 countries have signed the
convention and 141 have ratified it - - however, more can be done Factories in the
former Eastern Europe supply viruses that cause
fatal diseases, such as E-Coli and Salmonella,
without checking the identities of the
purchasers (from the trials of the largest
fundamentalist org. in Egypt, Abu-al-Dahab)
124Acknowledgements
- Dr. Geoffrey Zubay
- Salwa Touma
- Kathleen Kehoe
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