Bacteriology II and Gram Positives Flashcards
What test separates Staph Aureus from other staph species
Coagulate - Staph A is coagulase +
What does coagulase do
Virulence - allows bacteria to induce coagulation, and allows binding to fibrin and fibrinogen - increasing binding to host tissues and decreasing phagocytosis
What are some coagulase negative staph species
S. epidermidis
S. saprophyticus
How to differentiate coagulase negative staph species?
Novobiocin test
What is beta hemolysis
Complete hemolysis of blood agar
What types of strep cause beta hemolysis
Group A and Group B Strep
What is group A strep and what does it cause
Strep Pyogenes - causes strep throat
What is group B strep
Strep agalactiae
What is alpha hemolysis
Partial hemolysis - green circle
What are two types of strep with alpha hemolysis?
- Strep pneumo
2. Strep Viridians (green)
Gram positive diplococci with capsule
Strep pneumo
How to differentiate alpha hemolytic species
Strep pneumo has a capsule
Strep viridians does not
What is gamma hemolysis and what is it typical of
No hemolysis - Enterococcus
What are the gram + rods?
Clostridium Corynebacterium Listeria Bacillus Mycobacterium (acid-fast)
Gram + anaerobic rod
Clostridium
What are gram + bacteria that have branching filaments
Actinomyces and nocardia
How to differentiate gram + bacteria with branching filaments?
Actinomyces - anaerobe, not acid fast
Nocardia - aerobe, acid fast
What is staph aurerus protein A?
Virulence factor that can bind Fc-IgG which inhibits complement activation/opsonization and phagocytosis
What are the pigment producing bacteria
Staph Aureus
Actinomyces israelii
Pseudomonas aeruginosa
Serratia marcescens
Large golden colonies
Staph Aureus
Yellow/sulfur granules
Actinomyces israelii
Blue-green pigment
Pseudomonas aeruginosa
Red pigment
Serratia marcescens
Staph saprophyticus
Coag neg staph
UTIs
What staph species infects prosthetic devices and IV catheters
Staph epidermidis - produces adherent biofilms
Strep pneumoniae diseases
Most common cause of both CAP and bacterial meningitis in adults. Rust colored sputum.
Causes otitis media and sinusitis
Rusty colored sputum
Strep pneumo
Virulence factors of S. pneumo
IgA protease - can cleave IgA on mucosa surfaces
Capsule
Viridans strep
Many species that have alpha (partial) hemolysis, no capsule
Considered normal flora
How do viridans strep get into blood stream
S. sanguinis can cause subacute bacterial endocarditis at damaged valves
They make dextrans that bind fibrin-plt aggregates on damaged heart valves
What does strep pyogenes cause
Pyogenic - pharyngitis, cellulitis, impetigo
Toxigenic - Scarlet fever, TSS, nec fasc
Immunologic - rheumatic fever, PSGN
What is the Jones criteria
For rhuematic fever Joints - polyarthritis O - heart - pancarditis Nodules - subcutaenous Erythema marginatum Sydenham chorea
Group B strep (Strep agalactiae) - CAMP factor
Enlarges area of hemolysis formed by S. Aureus
Hippurate test
Positive in GBS
What strep species are bacitracin sensitive and resistant
Sensitive - Strep pyogenes
Resistant - Strep agalactiae
Enterococci
Endocarditis and UTI
Antibiotic resistance
Strep bovis and what does it cause
Group D strep
Colonizes the gut
Can cause bacteremia and subacute endocarditis in colon cancer pateints
What bacteria can grow in 6.5% NaCl and bile
Enterococci
How is corynebacterium diphtheriae diagnosed
Gram positive rods w/metachromatic granules
Elek test for toxin
What does corynebacterium diphtheriae look like on agar
Black colonies on cystine-tellurite agar
What is the ABCDEFG of corynebacterium diphtheriae
ADP-ribosylation Beta-prophage Corynebacterium Diphtheriae EF-2 Granules
Antibiotics for diphtheria
Antitoxin
Erythromycin or penicillin
Give vaccine - natural infection doesn’t induce immunity
Clostridia
Spore forming gram + rods that are obligate anaerobes
Clostridium tetani
Spore - Makes tetanospasmin
Once inoculated in a wound, becomes a gram positive rod, makes the toxin
Clostridium botulinum
Heat labile toxin that inhibits Ach at NMJ
Clostridium perfringens
Produces alpha toxin - a phospholipase that causes myonecrosis (gas gangrene) and hemolysis
C. Diff toxins
Produces 2 toxins
Toxin A: enterotoxin that binds brush border
Toxin B: cytotoxin that causes cytoskeletal disruption via actin depolymerization –> pseudomembranous colitis –> diarrhea
Bacillus anthracis
Gram positive rod
Produces toxin w/3 components
Only bacterium w/ a polypeptide capsule
Cutaneous anthrax
More common
Spores under the skin
Small papule appears transforms into small painless ulcer w/central necrosis, black eschar
Surrounding edema and erythema
Pulmonary anthrax
Inhalation of spores - phagocytosed in alveoli –> mediastinal LNs.
Flu like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock.
Woolsorter’s disease.
What does pulmonary anthrax look like on CXR
Mediastinal widening
What are some obligate anaerobes
Clostridium tetani
Actinomyces
Bacteroides
Listeria monocytogenes
Gram positive rod
Facultative intracellular organism
Tumbling motility
How does listeria enter body
Through GI tract - penetrates intestinal mucosa and is taken up by monocytes
How does listeria get into cytosol
From phagosome via listeriolysin O
How does listeria evade antibody
Forms rocket tails via actin polymerization that allows movement through cytoplasm and into cell membrane, avoiding antibody
Actinomyces
Anaerobes that colonize OP and GI tract
Nocardia
Gram positive aerobe, looks like actinomyces, acid fast.
Found in soil
In whom does nocardia cause infection
Pulmonary infections in immunocompromised and cutaneous infections after trauma in immunocompetent
Treatment of actinomyces
PCN
Treatment of nocardia
Sulfonamides
Actinomyces infections
Oral/facial abscesses that drain through sinus tracts
