Dr. Manal El Said

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Brucella Species (B. abortus, B. suis, B.
melitensis)
Dr. Manal El Said
Head of Medical Microbiology Department

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Brucella Species (B. abortus, B. suis, B.
melitensis)
Diseases
Brucellosis (undulant fever).

• Incubation period of 1 to 3 weeks onset acute
  or gradual
• Nonspecific symptoms fever, chills, fatigue,
  malaise, anorexia, weight loss occur.
• Undulating (rising-and-falling) fever pattern.
• Enlarged lymph nodes, liver spleen are
  frequently found.
• Pancytopenia occurs.
• B. melitensis infections more severe prolonged
  whereas B. abortus are more self-limited.
• Osteomyelitis is the most frequent complication.
• Secondary spread from person to person is rare.

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Brucella Species (B. abortus, B. suis, B.
melitensis)
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Brucella Species (B. abortus, B. suis, B.
melitensis)
Characteristics
Small gram-negative rods.
Habitat and Transmission

• Reservoir is domestic livestock.
• Transmission is via
• - Unpasteurized milk cheese
• - Direct contact with infected animal.

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Brucella Species (B. abortus, B. suis, B.
melitensis)
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Brucella Species (B. abortus, B. suis, B.
melitensis)
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Brucella Species (B. abortus, B. suis, B.
melitensis)
Pathogenesis

• Organisms localize in reticuloendothelial cells,
  especially liver spleen.
• Able to survive and replicate intracellularly.
• Predisposing factors include consuming
  unpasteurized dairy products working in
  abattoir.

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Brucella Species (B. abortus, B. suis, B.
melitensis)
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Brucella Species (B. abortus, B. suis, B.
melitensis)
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Brucella Species (B. abortus, B. suis, B.
melitensis)
Laboratory Diagnosis

• Gram-stained smear plus culture on blood agar
  plate.
• Identified by biochemical reactions by
  agglutination with known antiserum.
• Serologically by detecting antibodies in
  patient's serum.

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Brucella Species (B. abortus, B. suis, B.
melitensis)
Treatment
Tetracycline plus rifampin.
Prevention

• Pasteurize milk vaccinate cattle.
• No human vaccine is available

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Francisella tularensis
Dr. Manal El Said
Head of Medical Microbiology Department

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Francisella tularensis
Diseases
Tularemia.

• Presentation can vary from sudden onset of
  influenzalike syndrome to prolonged onset of
  low-grade fever adenopathy.
• Approximately 75 of cases are "ulceroglandular"
  type, in which site of entry ulcerates regional
  lymph nodes are swollen painful.
• Less frequent forms of tularemia include
  glandular, oculoglandular, typhoidal,
  gastrointestinal, pulmonary.
• Disease usually confers lifelong immunity.

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Francisella tularensis
Characteristics
Small gram-negative rods.
Habitat and Transmission

• Reservoir is many species of wild animals,
  especially rabbits, deer rodents.
• Transmission is by ticks , aerosols, contact
  ingestion.

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Francisella tularensis
Pathogenesis

• Organisms localize in reticuloendothelial cells.

Francisella tularensis enters respiratory tract
(2) lamina propria of respiratory bronchioles
via M cells (3) Digested antigen is taken up by
dendritic cells dendritic cells travel to
regional lymph nodes present F. tularensis
antigens to T-helper 1 cells (4) T-helper 1
cells proliferate they may return to site of
initial infection (5) restimulation by local
antigen presenting cells results in interferon-?
production macrophage activation (6) Failure
to clear F. tularensis results in granuloma
formation.
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Francisella tularensis
Laboratory Diagnosis

• Culture is rarely done because special media are
  required there is high risk of infection of
  laboratory personnel.
• Serologic tests detect antibodies in patient's
  serum.

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Francisella tularensis
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Francisella tularensis
Colonization of Francisella tularensis on various
media, namely (A) buffered charcoal yeast
extract (B) chocolate agar medium (C) sheeps
blood agar (D) cysteine heart agar.
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Francisella tularensis
Treatment
Streptomycin.
Prevention

• Live, attenuated vaccine for persons in high-risk
  occupations.
• Protect against tick bites.

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Pasteurella multocida
Dr. Manal El Said
Head of Microbiology Department

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Pasteurella multocida
Diseases
Wound infection, e.g., cellulitis

• Rapidly spreading cellulitis at site of animal
  bite is indicative of P. multocida infection.
• Incubation period is brief, less than 24 hours.
• Osteomyelitis can complicate cat bites, because
  cats' sharp, pointed teeth can implant organism
  under periosteum.

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Pasteurella multocida
Characteristics
Small gram-negative rods.
Habitat and Transmission

• Reservoir is mouth of many animals, especially
  cats dogs.
• Transmission is by animal bites.

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Pasteurella multocida
Pathogenesis

• Spreads rapidly in skin subcutaneous tissue.

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Pasteurella multocida
Laboratory Diagnosis
Gram-stained smear and culture.
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Pasteurella multocida
Treatment
Penicillin G..
Prevention

• Ampicillin should be given to individuals with
  cat bites.
• There is no vaccine.

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Capnocytophaga

• Capnocytophaga gingivalis
• It is gram-negative fusiform rod that is
  associated with periodontal disease
• It can be opportunistic pathogen, causing sepsis
  in immunocompromised patients.

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Capnocytophaga

• Capnocytophaga canimorsus
• It is a member of the oral flora of dogs and
  causes infections following dog bites.
• It cause sepsis in immunocompromised patients,
  especially those without spleen.

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HACEK Group

• This is group of small gram-negative rods that
  have in common the following
• Slow growth in culture,
• Requirement for high CO2 levels to grow in
  culture
• Ability to cause endocarditis.
• -They are members of the human oropharyngeal
  flora and can enter the bloodstream from that
  site.
• -The name "HACEK" is an acronym of the first
  letters of the genera of the following bacteria
  Haemophilus aphrophilus and Haemophilus
  paraphrophilus, Actinobacillus actinomycetemcomita
  ns, Cardiobacterium hominis, Eikenella corrodens,
  and Kingella kingae.

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Vibrio cholerae
Diseases
Cholera.

• Watery diarrhea (Rice-water stool) in large
  volumes.
• There are no red blood cells or white blood cells
  in stool.
• There is no abdominal pain subsequent symptoms
  are referable to marked dehydration.
• Loss of fluid electrolytes leads to cardiac
  renal failure.
• Acidosis hypokalemia occur as result of loss
  of bicarbonate potassium in stool.

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Vibrio cholerae
Diseases
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Vibrio cholerae
Characteristics

• Comma-shaped gram-negative rods.
• Oxidase-positive

Habitat and Transmission

• Habitat is human colon.
• Transmission is by fecaloral route.

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Vibrio cholerae
Pathogenesis

• Massive, watery diarrhea caused by enterotoxin
  that activates adenylate cyclase by adding
  ADP-ribose to stimulatory G protein.
• Increase in cyclic AMP causes outflow of chloride
  ions water.
• Toxin has two components
• - Subunit A ADP-ribosylating activity
• - Subunit B binds toxin to cell surface
  receptors.

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Vibrio cholerae
Pathogenesis

• Organism produces mucinase, which enhances
  attachment to intestinal mucosa.
• Infectious dose is high (gt107 organisms).
• Carrier state rare

string test
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Vibrio cholerae
Laboratory Diagnosis

• Gram-stained smear and culture. (During
  epidemics, cultures not necessary.)
• Agglutination of the isolate with known antisera
  confirms the identification.

string test
Vibrio cholerae on TCBS agar
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Vibrio cholerae
Treatment

• Treatment of choice is fluid and electrolyte
  replacement.
• Tetracycline is not necessary but shortens
  duration and reduces carriage.

Prevention

• Public health measures, e.g., sewage disposal,
  chlorination of the water supply, stool cultures
  for food handlers, and handwashing prior to food
  handling.
• Vaccine containing killed cells has limited
  effectiveness.
• Tetracycline used for close contacts.

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Vibrio parahaemolyticus

• Comma-shaped gram-negative rod found in warm sea
  water.
• Causes watery diarrhea
• Acquired by eating contaminated raw seafood.
• Outbreaks have occurred on cruise ships in
  Caribbean.
• Diarrhea is mediated by enterotoxin similar to
  cholera toxin.
• .

Forms GREEN non-sucrose fermenting agars
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Vibrio vulnificus

• Comma-shaped gram-negative rod found in warm sea
  water.
• Causes cellulitis life-threatening sepsis with
  hemorrhagic bullae.
• Acquired either by trauma to skin, especially in
  shellfish handlers, or by ingestion of raw
  shellfish, especially in patients who are
  immunocompromised or have liver damage.

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Campylobacter jejuni
Dr. Manal El Said
Head of Medical Microbiology Department

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Campylobacter jejuni
Diseases
Enterocolitis.
Characteristics

• Comma-shaped gram-negative rods.
• Microaerophilic.
• Grows well at 42C

Habitat and Transmission

• Habitat is human animal feces.
• Transmission is by fecaloral route.

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Campylobacter jejuni
Pathogenesis

• Invades mucosa of colon but does not penetrate
• Sepsis rarely occurs.

Laboratory Diagnosis

• Gram-stained smear plus culture on special agar,
  e.g., Skirrow's agar, at 42C in high-CO2, low-O2
  atmosphere.

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Campylobacter jejuni
Treatment
Usually symptomatic treatment only erythromycin
for severe disease.
Prevention

• Public health measures, e.g., sewage disposal,
  chlorination of the water supply, stool cultures
  for food handlers, and handwashing prior to food
  handling.
• No preventive vaccine or drug is available.

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Helicobacter pylori
Dr. Manal El Said
Head of Medical Microbiology Department

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Helicobacter pylori
Diseases

• Gastritis peptic ulcer.
• Risk factor for gastric carcinoma.

Characteristics
Curved gram-negative rod.
Habitat and Transmission

• Habitat is the human stomach.
• Transmission is by ingestion.

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Helicobacter pylori
Pathogenesis

• Organisms synthesize urease, which produces
  ammonia damages gastric mucosa.
• Ammonia neutralizes acid pH in stomach, which
  allows the organism to live in gastric mucosa.

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Helicobacter pylori
Laboratory Diagnosis

• Gram stain and culture.
• Urease-positive.
• Serologic tests for antibody
• "urea breath" test are useful.

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Helicobacter pylori
Treatment
Amoxicillin, metronidazole bismuth
(Pepto-Bismol).
Prevention
No vaccine or drug is available.
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Bacteroides fragilis
Dr. Manal El Said
Head of Medical Microbiology Department

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Bacteroides fragilis
Diseases
Sepsis, peritonitis, and abdominal abscess.
Characteristics
Anaerobic, gram-negative rods
Habitat and Transmission

• Habitat is the human colon, where it is the
  predominant anaerobe.
• Transmission occurs by spread from the colon to
  the blood or peritoneum.

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Bacteroides fragilis
Pathogenesis

• Lipopolysaccharide in cell wall is chemically
  different from less potent than typical
  endotoxin.
• No exotoxins known.
• Capsule is antiphagocytic.
• Predisposing factors to infection include bowel
  surgery and penetrating abdominal wounds.

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Bacteroides fragilis
Laboratory Diagnosis

• Gram-stained smear plus anaerobic culture
• Identification based on biochemical reactions and
  gas chromatography.
• Serologic tests not useful.

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Bacteroides fragilis
Treatment

• Metronidazole, clindamycin cefoxitin are
  effective
• Abscesses should be surgically drained.
• Resistance to penicillin G, some cephalosporins,
  and aminoglycosides is common.
• Plasmid-encoded  ß  -lactamase mediates
  resistance to penicillin.

Prevention

• In bowel surgery, perioperative cefoxitin can
  reduce the frequency of postoperative infections.
• No vaccine is available.