Microbiology: Gram Positive Bacteria

Catalase+: Staphylococcus

• "On the office's staph retreat there was NO StRESs"
• NOvobiocin: Saprophyticus is Resistant; Epidermidis is Sensitive

Catalase-: Streptococci

• "OVRPS" (overpass)
• Optocin: Viridans is Resistant; Pneumoniae is Sensitive

• "B-BRAS"
• Bacitracin: group B strep are Resistant; group A strep are Sensitive

• alpha: partial
• beta: complete
• gamma: none

-green ring on agar

• Strep pneumo (optochin sensitive)
• Viridans Strep (optochin resistant)

-clear ring on blood agar

• Strep pyogenes (Group A strep)
• Strep agalactiae (Group B strep)
• Staph aureus
• Listeria monocytogenes

• G+ Cocci in clusters
• -catalase+
• -coagulase+
• -Protein A (binds IgG)
• -TSST1 superantigen (TSS)

Forms fibrin clot around self --> abscess

• Presentation:
• 1. Inflammatory Disease
•      -skin infection
•      -organ abscesses
•      -pneumonia
• 2. Toxin-mediated Disease
•       -TSS (TSST1)
•      -Scalded skin syndrome (exfoliative toxin)
•      -rapid onset food poisoning (ingestion of preformed entertoxins)
• 3. MRSA (methicillin resistant)
• 4. Acute bacterial Endocarditis
• 5. Osteomyelitis

• G+ Cocci in clusters
• -catalase+
• -coagulase-
• -Novobiocin Sensitive

• -infects prosthetic devices and IV catheters
• -produces adherent biofilms
• -component of normal skin flora
• -contaminates blood culture

• G+ diplococci (lancet shaped)
• -catalase-
• -alpha hemolytic
• -optochin sensitive
• -encapsulated (not virulent w/o capsule)
• -IgA protease

• Most Common Cause of:
•      -Meningitis
•      -Otitis media (children)
•      -Pneumonia
•      -Sinusitis
• "S. pneumo MOPS are Most OPtochin Sensitive"

• -Associated with "rusty" sputum
• -Sepsis in SCA and asplenia

• G+ Cocci in chains
• -catalase-
• -alpha hemolytic
• -optochin resistant

-normal flora of oropharynx

• Streptococcus mutans: dental caries
• Streptococcus sanguis: subacute bacterial endocarditis at damaged valves

-Glycocalyx allows S. sanguis to stick to valves

"Viridans group strep live in the mouth because they are not afraid of-the-chin (optochin)"

• G+ Cocci in chains
• -Catalase-
• -beta hemolytic
• -bacitracin sensitive

• Causes:
• 1. Pyogenic
•      -pharyngitis
•      -cellulitis
•      -impetigo
• 2. Toxigenic
•      -Scarlet Fever
•      -Toxic Shock-Like Syndrome
•      -Necrotizing Fascitis
• 3. Immunologic:
•      -Rheumatic Fever
•      -Acute Glomerulonephritis

Antibodies to M protein: host defense, also cause RF

ASO titre: recent S. pyogenes infection

Glomerulonephritis more commonly preceded by impetigo than pharyngitis

"Pharyngitis can result in rheumatic phever and glomerulonephritis"

Scarlet Fever: rash sparing face, strawberry tongue, scarlet throat

• JNES Criteria for Rheumatic Fever
• -Joints: Polyarthritis

• -: endocarditis
• -Nodules (subcutaneous)
• -Erythema marginatum (pink ring on trunk/inner surface of limbs)
• -Sydenham's chorea (primarily face, feet and hands)

• G+ Cocci in chains
• -catalase-
• -Beta hemolytic
• -Bacitracin resistant

Colonize vagina

• Causes:
• 1. Pneumonia
• 2. Meningitis
• 3. Sepsis

"Group B for Babies!"

CAMP factor: enlarges area of hemolysis formed by S. aureus

Hippurate test positive

• Screen pregnant women at 35-37 weeks
• Intrapartum penicillin prophylaxis

• G+ cocci in chains
• -catalase-
• -variable hemolysis (gamma)
• -grows in 6.5% NaCl and bile (hardy)

• E. faecalis
• E. faecium

• Normal colonic flora
• PCN G resistant

• Cause:
• 1. UTI
• 2. Biliary Tract Infections
• 3. Subacute Endocarditis

Lancefield grouping (includes enterocci and non-enterococci)

VRE important cause of nosocomial infection

• G+ cocci in chains
• -Catalase-
• -gamma hemolysis
• -sensitive to 6.5% NaCl
• -grows in bile

Colonizes the gut

• Causes:
• 1. Bacteremia and acute endocarditis in colon cancer patients

"Bovis in the blood = cancer in the colon"

• G+ bacilli
• -Coryne = "club shaped"
• -metachromatic granules (blue and red)
• -Elek's test for toxins
• -Black colonies on cystine-tellurite agar

• Diphtheria
• -pseudomembranous pharyngitis (grayish-white membrane)
• -lymphadenopathy
• -myocarditis
• -arrhythmias
• exotoxin inhibits protein synthesis via ADP-ribosylation of EF2

• "ABCDEFG"
• -ADP-Ribosylation
• -Beta-prophage
• -Corynebacterium
• -Diphtheria
• -Elongation Factor 2
• -Granules

Prevention: toxoid vaccine

• G+ bacillus
• -spore forming
• -obilgate anaerobe

• C tetani
• C botulinum
• C perfringens
• C difficile

Tetanospasmin: exotoxin that causes tetanus, protease cleaves releasing protein for NTs

Blocks GABA and glycine release from Renshaw cells in the spinal cord

• Presentation:
• -spastic paralysis
• -trismus (lockjaw)
• -risus sardonicus

• Botulinum toxin:
• -heat labile
• -inhibits ACh release at NMJ

• Adults: ingestion of preformed toxin
• Children: ingestion of spores in honey (floppy baby syndrome)

• alpha toxin:
• -lecithinase (phospholipase)
• -causes myonecrosis (gas gangrene) and hemolysis

"Perfringens perforates a gangrenous leg"

• Toxin A:
• -enterotoxin
• -binds brush border of the gut

• Toxin B:
• -cytotoxin
• -destroys cytoskeleton of enterocytes
• -causes pseudomembranous colitis

Often secondary to antibiotic use (Clindamycin or ampicillin)

Diagnosis: detection of toxins in stool

Treatment: metronidazole, oral vancomycin

• G+ rod
• -spore forming
• -only bug with polypetide capsule (D-glutamate)
• -anthrax toxin

• Cutaneous anthrax:
• -Transmission: contact
• -black eschar (necrosis surrounded by edema, caused by lethal factor and edema factor, painless ulcer)
• -can progress to bacteremia and death

• Pulmonary anthrax:
• -Transmission: inhalation of spores (contaminated wool)
• -flu-like sx
• -rapidly progresses to fever
• -pulmonary hemorrhage
• -mediastinitis
• -shock
• -"woolsorter's disease'

G+ rod

• "reheated rice syndrome"
• -spores survive in cooking rice
• -keeping rice warm --> germination and enterotoxin formation

• Emetic type
• -rice and pasta
• -N/V within 1-5 hrs
• -cereulide: preformed toxin

• Diarrheal type
• -watery non-bloody diarrhea
• -GI pain
• -8-18hrs

• G+ rod
• -facultative intracellular

-unpasteurized milk/cheese, deli meats, vaginal transmission during birth

• -"actin rockets"
• -tumbling motility

• Cause:
• -In pregnant women (amnionitis, septicemia, spontaneous abortion)
• -neonatal meningitis
• -meningitis in immunocompromised
• -mild gastroenteritis in healthy

• Treatment:
• -gastroenteritis = self limited
• -Infants: ampicillin
• -Immunocompromised/elderly: empiric tx of meningitis

• G+
• -anaerobe
• -branching filaments (resemble fungi)

NOT acid fast

Normal oral flora

• Causes:
• -facial/oral abscesses
• -drain through sinus tracts
• -yellow sulfur granules

Tx: penicillin

• G+
• -aerobe
• -branching filaments

acid fast

Found in soil

• Causes:
• -pulmonary infections in immunocompromised
• -cutaneous infections after trauma in immunocompetent

Tx: sulfonamides

• 1. M tuberculosis
• -often resistant to multiple drugs

• 2. M kansaii
• -pulmonary TB-like sx

• 3. M avium-intracellulare
• -disseminated non-TB disease in AIDS
• -often resistant to multiple drugs
• -prophylaxis with azithromycin

• TB sx:
• -fever
• -night sweats
• -weight loss
• -hemoptysis

• Cord factor
• -in virulent strains
• -inhibits MP maturation
• -induces TNFa release

• Sulfatides
• -surface glycolipids
• -inhibit phagolysosome

M. leprae

• -infects skin and superficial nerves
• -likes cool temperatures (glove and stocking loss of sensation)
• -reservoir = armadillos

• Lepromatous
• -diffusely over skin
• -communicable
• -low cell-mediated immunity with humoral Th2 response
• "lepromatous can be lethal"
• Treatment:
• -2-5y: dapsone, rifampine, clofazimine

• Tuberculoid
• -hypoesthetic hairless skin plaques
• -high cell-mediated immunity with largely Th1 response
• Treatment:
• -multidrug therapy 6 mo: dapsone and rifampine