Pyogenic Cocci I: Staphylococcus & Micrococcus
Staphylococcus: Gram (+), Catalase (+), skin/mucous membranes, endogenous infections.
- Lab Diagnostic
• MSA (Mannitol Salt Agar): high salt inhibits most but staph. Fermentation of
Mannitol turns it pinkyellow
• TG agar: Tellurite reduction forms shiny black colonies
• Coagulase: Formation of clots
• Agglutination Test (Staphytex): Antigens on latex beads clump if S. aureus is
- Staph Species: S. aureus, S. epidermidis, S. saprophyticus, S. lugdunensis. S.
Cytotoxins: Destroys cells
Surface Adhesin Virulence Factor
Exfoliating Toxin (ETA & ETB): serine proteases, causes skin to slough off,
staphylococcal scalded skin syndrome (SSSS).
Enterotoxins: Food poisoning
Toxic Shock Syndrome (Toxin-1)
Staphylococcal Exoenzymesd • Staphylococcal Disease:
Cutaneous infections: Impetigo (pus pockets on face), Folliculitis (Inflam. of hair
follicle), Carbuncle (localized boil goes deeper into tissue)
Systemic Infections: Pneumonia, meningitis, osteomyelitis, septic arthritis, acute
Staphylococcus epidermidis: Frequent contaminant of blood cultures
Staphylococcus saprophyticus: 2 leading cause of UTI’s. Distinguishing: Resistance
Staphylococcus lugdunensis: Most common cause of valve endocarditis in native hearts
- Clinical ID of Staph
Coagulase Mannitol Trehalose PO4-ase Novobiocin
S. aureus + A A + Sens
S. epi - - - + Sens
S. sap - A A - resist
- Treatment of S. aureus: less than 10% are susceptible to penicillin.
MecA gene: codes for PBP. Normal penicillin binding protein is targeted by antibiotics
but this one has a much lower affinity.
Pyogenic Cocci II: Streptococcus and Enterococcus
Streptococcus: Gram (+), Catalase (-), Oxidase (-), non-motile, (-) for nitrate
reduction, Microaerophiles and fac anaerobe
- Rebecca Lancefield (1895-1981): antibodies vs. strep. A-W
- Group A: Streptococcus Pyogenes
Small clearish colonies, Beta-hemolytic. Sensitive to bacitracin. DISTINGUISHING:
hemolysis, PYR (+), NO VACCINE
• Immune Evasion:
1. Prevent Phagocytosis
Capsule- hyaluronic acid looks like host HA.
M-protein- Dimer that sticks out. Used for adherence/stopping phag/Ag-
variability. All strains have it. Prevents C3b binding
2. Avoid Complement
M-protein- stops C3b binding, preventing MAC attack 3. Ag-Variability
M-protein: different for different strains. This is how you can get strep over
• Adherence/Invasion of S. Pyogenes
F-protein- Bind fibronectin (especially in respiratory epithelium)
Capsule- sticking to cells
F-protein- get past epithelial barrier
• Toxins Produced by S. pyogenes
1. Streptococcal pyogenic exotoxins
Spe A, B, C, F
All Super Ag- pathological amplification of normal T-cell responses
Heat labile and cause Scarlet fever, rash, necro fasciitis, and TSSS in systemic
2. Streptolysin S
Cause Beta-hemolytic lysis RBC & WBC.
Kills phagocytes by causing them to release its toxins. We have no immune
response to this guy
3. Streptolysin O
We make Abs (antibodies) against this guy: ASO- anti-streptolysin O
Distinguish longer term Strep glomerular nephritis, rheumatic fever
4. Streptokinase, hyaluronidase: Important for deeper invasion
Helps w/ systemic spread, cleanse connective tissue.
• Suppurative (pus-producing) Diseases caused by S. pyogenes
Scarlet Fever-comes from strep throat. Rash comes from strains w/ Spe toxin
Skin-infections: Folliculitis, Cellulitis, Impetigo, Necrotizing fasciitis/bacterial
gangrene • Delayed Abs Mediated Diseases caused by S. pyogenes (nonsuppurative)
1. Rheumatic fever: M-protein strains, cross rxn abs w/ heart tissue, elevated
2. Glomerulonephritis: throat and skin
- Group B: Streptococcus agalactiae
Beta-hemolytic, smaller and lightly colored. Bacteremia in newborn meningitis.
DISTINGUISHING: Hippurate hydrolysis, resistant to bacitracin, CAMP (+)
• Disease of Group B Strep
Carried~ 10-30% + Urogenital tract (passed to newborn 60%)
Newborn meningitis: Through vaginal birth. Early onset-in utero/birth. Late
onset- 3 week old infant. Defining virulence capsule. Symptoms-sometimes
fever, constant fussiness. Treatment-penicillin, vancomycin etc. WBC or bacteria
in cerebrospinal fluid are signs of infection (Gram + cocci). Can only stain
anthrax from blood
- Viridans Streptococi
Urogenital tract. Don’t have any Lancefield serotypes. Cause cavities & endocarditiss. Go from
oral cavity to heart to cause endocarditis. There IS a vaccine
- Streptococcus pneumoniae “pneumococcus”
No Lancefield. Capsule: very big required to be virulent because they have sensitive walls
2. Sinus infections. Otitis media
3. Meningitis (non-infant): Kids (pre-vaccine/unvaccinated)/ Many different
serotypesAbs bind to capsule polysaccharide. Pneumococcal vaccine:
original was 7 valent, recently 13 valent for kids, 23 valent for adults.
• Lab Diagnosis of Streptococcus pneumoniae
Gram (+), sensitive to optochin, slimy green colonies, S. pneumoniae lysed by
bile. Quelling Reaction: capsule swelling w/ addition of abx. Hemolysin,
pneumonia associated w/ aspiration.
- Enterococcus (old group D): Enterococcus faecalis, faecium Nosocomial infections abx resistant. Gamma w/ some alpha. Super bugs: VRE-Vancomycin
- Group D: Streptococcus bovis
Prescence associated w/ colon cancer. Optochin resistant, non-bile soluable, PYR (+), grow in
6.5% NaCl, broad temp range (10-45 C)
Pyogenic Cocci III: Neisseria & Others
Only true Gram (-) cocci, pussiest of bacteria, super inflammatory, rely on asymptomatic
carriers. Catalase/motility/nitrate (-), oxidase (+). Oxidizes glucose and maltose
• Species: Neisseria gonorrhoeae (STD), meningitides (strict human pathogens),
sica, & mucosa (commensals)
- Neisseria meningitides
• Invasion: crosses endothelium. Blood blood brain barrier meningitis
• Virulence factors
1. Polysaccharide capsule: 13 defined serotypes based on capsule. B most
Group B: low immunogicity; hard to make antibodies/immune response
(Abs). Potential cross-protection in vaccine for B
2. Bind human Transferrin & Lactoferrin: protein that bind human transferrin
and lactoferrin which helps bacteria compete w/ host for Iron. HIGHLY
HOST SPECIFIC strictly host pathogen.
3. IgA protease: Cleave human IgA (abs in mucosal sites). Helps with carrage
4. Rmp protein: outer membrane protein complexes with lipid A endotoxin.
Abx made are not effective, and bing harmlessly to bacteria. Lets them avoid
effective abs binding.
5. Lipoligosaccharide (LOS): Low immunity, blebs out and causes big
6. Pili protein: span bacterial membrane. Important for attachment to
nasopharynx. Anti-phagocytic and undergo antigenic variation.
7. Opa suppress T-helper Opc cross endothelium • Clinical Diseases of G. meningitides
1. Meningitis – Child (5=> and in daycare. 6-24 months very susceptible) &
young adults. Close to 100% mortality when not treated. Neurologic sequel
sometimes. Droplet spread
2. Meningococcemmia – disseminated septicemia, characterized by petechial
skin lesions, Waterhouse Friderchsoon syndrome (septic shock).
3. Meningococcal pneumonia- usually complication of prior respiratory
• Lab Diagnostics: Gram stain of cerebral spinal fluid. O sugar test for
differentiate from gonocci. Ferment glucose & mannitol.
• Treatment: Susceptible to penicillin and cephalosporin. VACCINE: available for
strains (polysaccharide capsule) A, C, Y, W and one coming for B
- Neisseria gonorrhoeae
• Virulence attachment/invasion
1. Opa proteins
2. Pili- attachment
3. Por B (porin protein)-very w/ strains. Reduce degranulation of neutrophils
(phagocytes), inhibits complement. Inhibits neutrophils
4. IgA protease
5. Invades/Multiplies w/in cells
6. Pili C- Ag variation
• Pathogenesis of N. gonorrhoeae: Induce (TNFalpha-proinflamm cytokine can
go to TSSS if it goes systemic. Cause of most of the symptoms) Invade
intracellular phagocyte (inhibits killing in granules) • Clinical Diseases
1. Gonorrhea: Disease in young adults. Females (20-50%) with complications
of (10-20 %).
2. Conjunctivitis- Newborns. Othalmia neonatorum conjunctivitis.
3. Gonococcemia- disseminated septicemia, skin, and joint infection, leading
cause of purulent arthritis. 1-3% of infection in Females.
• Lab Diagnosis of N. gonorrhoeae: Chocolate and MTM media
• Treatment: Resistant to penicillin, ciprolfaxin. Ceftriaxone. No Vaccine.
Chemoprophylaxin for newborn eye infections only.
Others Gram (-) cocci
- Moraxella catarrhalis: Respiratory tract infections, otitis media, sinusitis, pneumonia,
inert on sugars, DNAse (+)
- Eikenella corrodens: opportunistic pathogens, hard to grow, endocarditis
- Kingella kingae: arthritis in kids
Corynebacterium, Listeria & Erysipelothrix
Gram (+) bacilli. Weakly Beta-hemolytic. CAMP (+), motility
• Infection Cycle of Listeria: (a) Internalin protein-binds to cadherin. (b) Vesicle has
decreased pH which activates Listeriolysin O. (c) Listeriolysin O will lyse vesicle and
move to cytosol (d) Listeria replicates in cytosol and makes Act-A which polymerizes
actin in a polar direction, pushing bacteria to the membrane. Spread through basal
membrane helps it possibly get into a macrophage.
• Clinical Diseases
1. Listeriosis-food poisoning (fecal-oral). Neonatal can be early or late onset. Early in
utuero can lead to still birth, abortion, defects. Late passed through birth canal, and
can lead to meningitis in 2-3 weeks. 2. Meningitis (Adults) - In immune compromised adults.
3. Bacteremia- Replicates in blood
• Listeria Immune Response: Cellular Immunity (T & mhcrophages)
• Lab Diagnosis of L. monocytogenes: OCLA, CAMP (+), parasol motility, Esculin
Erysipelothrix rhusiopathiae: Long chains, found in veterinarians/zookeepers/farmers
- Erysipeloid: Skin infection, hint: zoonosis
- Corynebacterium diptheriae
First toxoid pediatric vaccine. Would disproportionally affect poor in tightly packed housing.
Found on skin, UT.
• Clinical Disease
1. Diptheria- membrane forms in throat and chokes host to death
2. Cutaneous diphtheria- shankers
• Immune Response to C. diphtheria
Humoral Immunity: Abs vs toxin
Antitoxin: purified horse Abs. Passive immunity, would not work 2 time because we
make Abs against horse Abs.
• Pathogenesis of C. diphtheria Diphtheria toxin inhibits protein synthesis
AB toxin. (a) B part bind to EGF (b) A gets into cell (c) inactivates elongation factor-2,
prevents protein synthesis.
• Clinical Diagnosis: Tinsdale Medium, Pyrazinamidase (-), catalase (+), nonmotile,
granules, Elek test for toxigenic C. diph
• Treatment of Diphtheria: Maintain open airway. Treat with penicillin/erythromycin. - Corynebacterium jeikeium: Hospital found
- Corynebacterium urealyticum: Urogenital opportunist, kidney stones, very urease (+)
Gram (-), non-sporeforming, catalase (+), oxidase (-), Facultative anaerobes. 30% bacteremia,
70% o UTI’s, lots of gastroenteritis.
Pathogenic Enterobacteriacae: Salmonella, Shigella, Yersinia, E. coli (depends on strain)
Opportunists Enterobacteriacae: E. coli, Klebsiella, Proteus, Citrobacter, Serratia.
Opportunistic in either in a new location, or in immune compromised.
• Serological Classification
1. Flagella H. antigen, spreading through host
2. LPS Lipopolysaccharide or endotoxin [O polysaccharide, polysacch, core &
exotoxin] Changes among species
3. Capsule K antigen, heat labile
4. Pili conjugation & adherence
• Gastroenteritis caused by Enterobacteriacae
1. Non-Invasive- Due to toxin produced & not the bacteria invading & destroying
epithelial barrier (Vibrio cholera, ETEC)
2. Invasive- Invade epithelial barrier (Shigella, Salmonella)
3. Systemic – (Salmonella typhi, Campylobacter jeikeium)
• Common Virulence Factors
1. Endotoxin-lipid A
2. Capsule- Immune evasive
3. Antigenic Variation- K & H Ag
4. Type III Secretion System- Protein syringe spans membrane 20 proteins form
pseudo syringe. Allows, delivery of contents into host. Only found in Gram (-). Salmonella
- Salmonella enterica, serovar Typhi: Facultative intracellular pathogens, cause
membrane ruffling to internalize the bacteria.
• Virulence of S. Typhi TTSS 1: injects Sip A (Stabilize host actin, induces ruffling,
cause endocytosis). TTSS 2: injects SspH (activated in vacuoles prevent phagolysosome
fusion w/ endosome. Allows survival in cell).
• Clinical Disease of Salmonella
1. Gastroenteritis- Get it from chicken, eggs, dairy. S. Typhermurium: High infection
dose, person to person spread. S. Typhi: Low infectious dose, aslo person to person.
Diarrhea, not bloody, but induces vomiting.
2. Septicemia- S. Typhi, S. Paratyphi, S. Cholerasuis
3. Typhoid Fever: S. Typhi. Gest engulfed by macrophage under epithelial barrier.
Replicates in macrophage & goes to liver, spleen, and bone marrow. Fever and then
more gastroenteritis. Can lead to septic shock and organ failure. 1-5% chronic
colonization of gallbladder (untreated). Typhoid Mary was the 1 associated carrier
Big virulence plasmid with TTSS. Uses actin polymerization to move. Similar to Listeria.
Humans are the only reservoir.
• Species: dysenteriae, flexneri, boydii, sonnei. Can only use serological kits and
sequencing to distinguish.
• Pathogenesis of Shigella: (a) Adhesioninvasion via M-cell. (b) Phagocytosis by
macrophage and inhibition of phagolysosome. Make proinflammitory cytokines and
macrophage apoptosis occurs. (c) IL-1 induces transcytosis (movement across a barrier).
(d) spread to other epithelial cells (intracellular). (e) Transmission
NOTE: Shigella is solely in humans because only we express the appropriate receptor.
This receptor is also up regulated in the kidneys which is how HUS can occur.
• Shiga Toxin (Stx) of S. dysenteriae- AB exotoxin. B-pentamer binds host cell
glycolipids. A-binds host 60s and inhibits protein synthesis. Leads to severe
gastroenteritis with blood painful diarrhea. Can cause hemolytic uremic syndrome (HUS)
in kidneys. Escherichia coli
- Enterotoxigenic E. coli (ETEC) - Traveler’s Diarrhea (noninvasive, secretory similar to
High infectious dose and usually spread through contaminated food/water
LT-1: AB toxin that binds to host and upregulates adenylate cyclase, increases [ATP],
which causes efflux of ions and water.
- Enteropathogenic E. coli (EPEC) – Infant secretory diarrhea. Low infections dose
BFP (bundle forming protein) attaches, TTSS injects Tir. Tir causes actin polymerization,
cell death and destruction of vili.
- Enteroaggregative E. coli (EAEC) – Infant & Travelers Diarrhea. Can cause chronic
AAF (aggregative adherence factor): fimbriae allow biofilm formation
Cytotoxin & Enterotoxin Enteroaggregative shiga toxin (EAST like LT-1), PE-T
- Enterohemorrhagic E. coli (EHEC) - Causes hemorrhagic colitis like intestine
instead of small. Most common transmitted and symptoms shown in 3-4 days. Usually in
HUS can occur as a complication. EHEC came from EPEC that acquired shiga-toxin
- Other opportunistic E. coli diseases- UTI, neonatal meningitis, septicemia
• Clinical Disease
1. Enterocolitis: Y. enterocolitica and Y. pseudotuburculosis. Swollen lymph nodes &
colitis which mimics appendicidis.
2. Bacteremia: from blood transfusion, can replicate at low temp
3. Plague: zoonosis with rats/fleas/humans. Bubonic swollen lymph nodes, 75%
mortality. Pneumonic goes septic and can die before showing symptoms 90% Klebsiella
- Klebsiella pneumoniae: slimy capsule mucoid. Pneumonia and UTI’s
- Klebsiella granulomatis: granulomas
- Proteus mirabilis: Urease (+)
- Enterobacter, Citrobacter, Morganella, Serratia
Non-fermenting Gram (-) Bacilli
Everywhere in enve. Carriers common in hospital, immune compromised, Abx resistance
- Pseudomonas aeruginosa: Gram (-) rods, OXIDASE (+), obligate aerobes, motile.
Makes water soluble pigment. Don’t decolorize as well, so look a little gram +.
• Quorum Sensing Biofilm: HSL=Homoserine lactone (las gene), inducible. Binds to
transcription factors involved in biofilm production and causes the secretion of alginate.
High density of bacteria have HSL auto-induced which binds to transcriptional receptor
(PA 1, 2).
• Virulence Factors
1. Adhesins- pili and biofilms.
2. Exotoxin A (ETA)- Acts like Diptheria toxin, causes tissue damage in wounds/burns,
and corneal infections.
3. TTSS- epithelial barrier damage
4. Cytotoxins injected by TTSS: phospholipase C (exo U), Exoenzyme S/T promotes
invasion by rearranges the cytoskeleton causes apoptosis. Causes bacteremia and
5. Exotoxin T- decreases wound healing
6. Exotoxin S/U- decrease IL-1, 18 (cytokines)
7. Las A/B Regulated by HSL. Degrade elastin, degrade complement proteins
(immune evasive) 8.