Survey of Microbes Part I: Important prokaryotes

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Survey of MicrobesPart I Important prokaryotes
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But first a word on shape, arrangement and size

• SHAPES
• ____________ spherical, ball shaped
• ____________ - rod
• _________________ helical, comma (vibrio),
  twisted rod (spirillum, rigid with lophotrichous
  flagella), spirochete (flexible with periplasmic
  flagella)
• Also
• intermediate shapes like coccobacillus
• cells can be thin (filamentous)
• Cells can be pleomorphic (species can have gt1
  form such as Corynebacterium diphtheriae)

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arrangements of bacteria

• Pairs (2 like diplococci, diplobacilli)
• Tetrads (4 cells in packet)
• Sarcinae (balls or blocks of 8, 16, 32 cells)
• Chains (streptococci streptobacilli)
• Clusters (Micrococcus, Staphylococcus)
• Palisades arrangement (Corynebacteria)

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streptococci
diplobacillus
spirochete
spirillum
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size
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Bacterial Taxonomy Based on Bergeys Manual

• Bergeys Manual of Determinative Bacteriology
  five volume resource covering all known
  prokaryotes
• Classification based on genetic information
  phylogenetic
• Two domains Archaea and Bacteria
• Five major subgroups with 25 different phyla

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Major Taxonomic Groups of Bacteria

• Domain ____________ primitive, adapted to
  extreme habitats and modes of nutrition
• Domain Bacteria
• Phylum Proteobacteria Gram-negative cell walls
• Phylum Firmicutes mainly gram-positive with low
  G C content
• Phylum Actinobacteria Gram-positive with high G
  C content

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Figure 4.27 Universal phylogenetic tree
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IMPORTANT GRAM POSITIVE BACTERIA
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Important Gram positive bacteria

• Soil bacteria
• Bacillus
• Clostridium (some pathogens)
• Lactic acid bacteria Lactococcus, Lactobacillus,
  Acidophilus
• Several human pathogens
• Staphylococcus (S. aureus)
• Streptococcus (S. pyogenes, S. pneumoniae)
• Mycobacterium (M. leprae and M. tuberculosis)
• Corynebacterium
• Listeria monocytogenes
• Others
• Propionibacterium
• Streptomyces
• Mycoplasma! (no cell wall, but its grouped with
  G)

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Staphylococcus
1a.) Gram cocci

• Genus staphylogrape clusters
• S. epidermidis opportunistic pathogen no
  virulence factors natural flora
• S. aureus hemolytic, coagulase, invasive flora
  of the nose but still a pathogen
• Many diseases endocarditis, pneumonia,
  meningitis, arthritis, intoxications such as
  ______________________ and food poisoning more
  often cuteneous
• pimples/boils/abscesses/carbuncles, pink eye
• scalded skin syndrome,
• impetigo.

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CARBUNCLE
Endocarditis
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Virulence factors of Staph
1a.) Gram cocci --Staph
Pathogenic effects mostly associated with
________________________
Prevents bacteria from being cleared from host

• Diagnostic marker
• localized clotting

• Kills leukocytes so
• that bacteria are
• not phagocytosed
• Form pus and acne

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Current estimate gt60 of hospital acquired S.
aureus infections are MRSA Many strains are MDR!!
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Percentage of Staphylococcus aureus isolates
resistant to methicillin in national surveys,
United States, 19992004.
TSN, The Surveillance Network (data include
hospital infections) NNIS, National Nosocomial
Infections Surveillance System (data include only
intensive care units) SENTRY, includes only skin
and soft tissue infections.
(source Klein et al. 2007. EID)
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Hospitalizations and Deaths Caused by
Methicillin-Resistant Staphylococcus aureus,
United States, 19992005
Figure 1. Estimated methicillin-resistant
Staphylococcus aureus (MRSA)related
hospitalization rates, United States, 19992005.
Rates are no. MRSA-related discharges/1,000
hospitalizations. Error bars represent 95
confidence intervals. (source Klein et al. 2007.
EID)
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Streptococcus
1a.) Gram cocci

• Group A Strep ____________
• Strep throat, pharyngitis
• Secondary Scarlet fever (systemic rash)
  Rheumatic fever (heart valves, arthritis)
• Cuteneous infections Impetigo (older children),
  pyoderma, acne, Erysipelas AKA St. Anthonys
  Fire Toxic shock syndrome
• ____________ ____________ flesh eating
  bacteria
• All are mediated by various virulence factors
  esp. ____________

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1a.) Gram cocci --Strep
Strep throat
Strawberry tongue Scarlet fever
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Streptococcus
1a.) Gram cocci --Strep

• Streptococcal toxic shock syndrome (STSS), causes
  blood pressure to drop rapidly and various organs
  to fail. About 20 of patients with necrotizing
  fasciitis and more than half of those with STSS
  will die. Generally, the mortality rate for other
  forms of invasive group A streptococcal disease
  is 10-15.

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PYODERMA (S. aureus or S. pyogenes)
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Virulence factors of Strep
1a.) Gram cocci --Strep

• ____________ due to secretion of many enzymes
  and toxins including
• ____________ lyse red blood cells
• ____________ breaks down collagen (cement of
  connective tissue helps organism spread)

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Other pathogenic Streptococci
1a.) Gram cocci --Strep

• ________________________ causes dental caries
  (cavities)
• ____________________________ (often called
  pneumococcus)
• carried in upper respiratory tract and
  nasopharynx of humans
• 15 of children and 5 of adults are carriers
  
• grow in pairs (NOT in long chains)
• most common cause of pneumonia and otitis media
  (middle ear infection)

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Clostridium
1b.) Gram rods --Clostridium

• ____________ ____________ (cannot grow in oxygen)
  
• rod shaped bacteria
• contain ____________ resistant to heat and
  chemicals spores are introduced into injury or
  anaerobic wound or ingested (botulism)
• spores germinate and active bacteria multiply

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Medically important species
1b.) Gram rods --Clostridium

• C. tetani ____________
• neurotoxin called tetanospasmin (a dot the size
  of a period-kills 30!)
• blocks muscles relaxation muscles spasm and
  contract
• contractions tear muscles/cause compression
  fraction of vertebrae
• death from spasms of respiratory muscles
• vaccine (DPT) inactivated toxin used to
  stimulate antibodies
• C. difficile ____________ ____________
• often caused when antibiotic therapy alters
  microflora in intestines
• and allows for growth of this organism
• C. perfringens causes ______________________
  (severe tissue death) also foodborne diarrhea

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Medically important species

• C. botulinum ____________________ .
• grows in anaerobic environments (canned foods)
  discard bulging cans!
• Produces toxin MOST potent of ALL toxins
  specific for nerve endings (synapses)
• Blocks acetylcholine (neurotransmitter) nerve
  impulses blocked!
• Botulism disease progression
• Initial symptom blurred vision and nausea
  flaccid paralysis respiratory and cardiac
  failure
• slow recovery nerve endings regenerate
  respiratory support antibiotics are of no use!
• Prevention Toxin is destroyed by boiling and
  nitrites in food prevent bacterial growth
• A word about commercial use of BOTOX
• prevent wrinkles maybe, BUT
• strasbismus crossed eyes
• blephorospasm inability to keep eyelids open

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Bacillus

• commonly found in soil
• produces ____________

Medically important species of Bacillus

• ____________________ anthrax disease of
  cattle, sheep and humans Two forms of anthrax
• ____________(skin) transmitted through a break
  in the skin
• cause pustule or lesions tissue dies, crusts
  and falls off
• systemic (bloodstream) shock/ collapse
• ____________(pulmonary) transmitted by inhaling
  anthrax spores
• starts as pneumonia, high fever then septicemia,
  respiratory distress, death
• biowarfare agent spores can be spread in
  aerosols
• no spread from person to person!
• penicillin effective if given early

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Cutaneous anthrax note BLACK lesions
Anthrax sepsis due to inhalation anthrax (now
involving eye) Woman was exposed to animal hides
Pennsylvania 2006
Inhalation anthrax on x-ray Patient died next
day.
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Bacillus (contd)
1b.) Gram rods --Bacillus

• Bacillus ____________ food poisoning often from
  starchy food especially rice
• Bacillus thuringiensis insect pathogen produces
  delta endotoxin in crystal form insect eats toxin
  crystals and dies
• sold for plant treatment as pesticide
• transgenic plants engineered to produce toxin
• Bacillus subtilis produces bacitracin
• Bacillus polymyxa produce polymixin

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Mycobacterium
1b.) Gram rods Mycobacterium

• ____________________________________
• Acid-fast stain mycolic acid Slow growing
• Leprosy mainly affects the skin, peripheral
  nerves, upper respiratory tract.
• discovered by G.A. Hansen in 1873 first
  bacterium to be identified as causing disease in
  man.
• contagious, but not widespread because 95 of the
  population have competent immune systems.
• TB causes tubercles in lungs, bones poor
  health, crowding plays a role (communicable)
• leading cause of death in the world from a single
  infectious disease!
• affects 1.7 billion people/year which is equal
  to one-third of the entire world population!

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TB cavitation, and calcified tubercle
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Other pathogens
1b.) Gram rods --others

• ___________________ - C. diphtheriae causes
  diphtheria DPT vaccine
• -pseudomembrane on tonsils
• -strong toxin can destroy heart
• ______________________ food poisoning outbreak
  in hot dogs intracellular pathogen

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Pseudomembrane necrosis, plasma, fibrin and
bacteria
Pallisades arrangement of Corynebacterium Can be
pleiomorphic
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Nonpathogenic, but important!

• Propionibacterium, Brevibacterium - swiss cheese,
  bacterial acne, stinky feet propionic acid and
  sulfur compounds
• Streptomyces - antibiotic production
• erythromycin, neomycin, streptomycin,
  tetracycline
• ____________ normal flora in gut and vagina
• found in yogurt, cheeses
• (mozzarella, cheddar, provolone)

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____________

• naturally lack a cell wall
• stabilized by sterols,
• resistant to lysis
• extremely small (0.1 0.5 µm)
• range in shape from filamentous to coccus or
  doughnut shaped
• ____________ ____________
• Mycoplasma ____________ atypical pneumonia in
  humans (walking pneumonia)