Gram + Bacteria Flashcards
S. Aureus Lab Algorithm
Gram +
Cocci in Clusters
Catalase +
Coagulase +
S. Aureus Virulence Factor, Main Toxin, and Colonization
Virulence Factor: Protein A (binds Fc-IgG, inhibiting complement and phagocytosis)
Toxin: TSST (binds MHCII and TCR, inducing T cells)
Colonization: Commonly colonizes the nose and skin
S. Aureus Diseases (2 main ones)
Inflammatory Disease (skin, organs, pneumonia, endocarditis, osteomyelitis) Toxin-mediated disease (toxic shock:TSST1, scalded skin:exfoliative toxin, food poisoning:entertoxins)
Staph epidermidis Lab Algorithm
Gram + Cocci in clusters Catalase + Coagulase - Novobiocin sensitive
Staph epidermidis Pathology and Flora
Infects prothetic devices and intravenous catheters by producing adherent biofilms
Component of normal skin flora (contaminates blood cultures)
Staph saprophyticus Lab Algorithm and Presentation
Gram + cocci in clusters, catalase +, coagulase -, novobiocin resistant
Second most common cause of uncomplicated UTI in young women (first is E. coli)
Staphylococcus epidermidis and saprophyticus Treatment
Needs to include Vancomycin
Streptococcus pyogenes Lab Algorithm
Gram + cocci in chains, catalase -, beta hemolytic,
Strep pyogenes (Group A) Lab Algorithm
Gram + cocci in chains, catalase -, beta hemolytic, bacitracin sensitive
ASO titer detects regent infection
Strep pyogenes Presentation (3 Main Categories)
Pyogenic: pharyngitis, cellulitis, impetigo
Toxigenic: scarlet fever, toxic shock-like
Immunologic: rheumatic fever, acute glomerulonephritis
JONES Criteria for rheumatic fever
Polyarthritis Carditits Subcutaneous nodules Erythema marginatum Sydenham chorea
Scarlet Fever
Caused by toxins (exotoxin A?) secreted by Strep pyogenes
Scarlet rash with sandpaper-like texture
Strawberry tongue (also kawasaki)
Circumoral pallor
M Proteins
These are proteins on Strep pyogenes
Antibodies to M proteins enhance host defenses against Strep pyogenes, but also can give rise to rheumatic fever
Strep agalactiae (Group B) Lab Algorithm
Gram + cocci in chains, catalase -, beta hemolytic, bacitracin resistant
Strep agalactiae Presentation
Colonizes vagina
Can cause pneumonia, meningitis, and sepsis in babies
Produ
Strep agalactiae Presentation
Colonizes vagina
Can cause pneumonia, meningitis, and sepsis in babies
Produces CAMP factor (enlarges S aureus hemolysis)
Pregnant women screened at 35 weeks and positive cultures receieve intrapartum penicillin prophylaxis
Strep pneumoniae Lab Algorithm
Gram + cocci in chains (diplococci?), catalase -, alpha hemolytic, optochin sensitive
Lancet-shaped
Strep pnuemoniae Presentation
Associated with a "rust colored sputum" Most common cause of: Meningitits Otitis media (in children) Pneumonia Sinusitis
Strep pneumoniae Virulence Factor
IgA protease (cleaves IgA in order to colonize respiratory mucosa) Polysaccharide Capsule
Strep pneumoniae Lab Algorithm
Gram + cocci in chains (diplococci?), catalase -, alpha hemolytic, optochin sensitive, bile soluble (lysed by bile)
Lancet-shaped
Strep pneumoniae Virulence Factor
IgA protease (cleaves IgA in order to colonize respiratory mucosa) Polysaccharide Capsule
Viridans Group Streptococci Lab Algorithm
Gram + cocci in chains, catalase -, alpha hemolytic, optochin resistant, bile insoluble (not lysed by bile)
Viridans Group streptococci Presentation
Normal flora of the oropharynx
Cause dental caries (mutans)
Cause subacute bacterial endocarditis and damaged valves (sanguinis–makes dextrans which bind to fibrin-platelet aggregates on damaged valves)
Viridans Group streptococci Presentation
Normal flora of the oropharynx
Cause dental caries (mutans)
Cause subacute bacterial endocarditis and damaged valves (sanguinis–makes dextrans which bind to fibrin-platelet aggregates on damaged valves)
Enterococci (Group D strep) Lab Algorithm
Gram + cocci in chains, catalase -, gamma hemolytic (but variable actually), growth in bile and 6.5% NaCl (E. faecalis)
Enterococci Presentation
Normal colonic flora that are penicillin G resistant
UTI, biliary tract infections, and subacute endocarditis following GI/GU procedures
Treat with vancomycin (unless VRE)
Strep bovis (Group D strep) Lab Algorithm
Gram + cocci in chains, catalase -, gamma hemolytic (but variable actually), growth in bile but not 6.5% NaCl
Enterococci (Group D strep) Lab Algorithm
Gram + cocci in chains, catalase -, gamma hemolytic, growth in bile and 6.5% NaCl (E. faecalis)
Strep bovis (Group D strep) Lab Algorithm
Gram + cocci in chains, catalase -, gamma hemolytic (but variable actually), growth in bile but not 6.5% NaCl
Strep bovis Presentation
Colonizes the gut
Can cause bactermia and subacute endocarditis in colon cancer patients
Strep bovis Presentation
Colonizes the gut
Can cause bactermia and subacute endocarditis in colon cancer patients
Gram + Rods
Clostridium (anaerobe) Corynebacterium Listeria Bacillus (aerobe) Mycobacterium (acid-fast)
Corynebacterium diphtheriae Lab Diagnosis
Gram + Rod (coryne=club shaped) Non-spore forming Motile Metachromatic (blue and red) Granules Elek test for diptheria toxin Black colonies on cystine-tellurite agar
Corynebacterium diphtheriae Presentation
Diptheriae:
Pharyngitis with pseudmomembranes in throat
Severe lymphadenopathy (bull neck)
Myocarditis
Arrhythmias
Note that toxoid vaccine prevents diphtheria
Costridia Lab Diagnosis
Gram positive bacilli
Spore forming
Obligate anaerobes
All motile spores except C. perfringens
C. tetani Toxin and Presentation
Tetanus Toxin
Spastic paralysis, trismus (lockjaw), and risus sardonicus (facial spasm–looks like grinning)
C. botulinum Toxin, Transmission, and Presentation
Heat labile Botulin Toxin
Transmitted in adults by ingesting preformed toxin
Transmitted in kids by ingesting spores in honey
Presentation: botulism (descending flaccid paralysis)
C. perfringes Toxin and Presentation
Alpha toxin (a phospholipase)
Myonecrosis (gas gangrene)–may need amputation
Hemolysis
C. difficile Toxins, Presentation, and Treatment
Toxin A (enterotoxin) and Toxin B (cytotoxin) Leads to pseudomembranous colitis and diarrhea often secondary to antibiotic use (especially clindamycin or ampicillin) Treatment: metronidazole or ORAL vancomycin or fecal transplant for recurrent cases
Bacillus Lab Algorithm
Gram + Bacilli
Spore forming
Obligate aerobe
B. cereus is motile and B. anthracis is not motile
Bacillus anthracis Toxin, Capsule, and Presentation
Anthrax toxin
PolyPEPTIDE capsule (D glutamate)
Causes cutaneous, pulmonary, or ingested anthrax
Cutaneous Anthrax Presentation
Boil-like lesion leads to ulcer with black eschar which can uncommonly progress to bacteremia and death
Pulmonary Anthrax Presentation
Inhalation of spores leads to flu-like symptoms that rapdily progress to fever, pulmonary hemorrhage, mediastinitis, and shock. Death is 100%.
Woolsorters’ disease is inhalation of spores from contaminated wool
Ingested Anthrax Presentation
Throat and intestine lesions leads to dysentery
Bacillus cereus Presentation
Causes food poisoning
Emetic type usually seen with rice and pasta from the heat stable toxin and is seen 1-5 hours after ingestion
Diarrheal type is from the heat labile toxin and is seen 8-18 hours after ingestion
Listeria monocytogenes Lab Algorithm
Gram + bacilli
Non-spore forming
Motile
Only Gram + with LPS
Listeria monocytogenes Transmission
Ingestion of unpasteurized dairy products and deli meats, transplacental transmission, or vaginal transmission during birth
Listeria monocytogenes Presentation
Can cause amnionitis, septicemia, and spontaneous abortion in pregenant women
Meningitis in immunocompromised or neonates
Mild gastroenteritis in healthy
Listeria monocytogenes Treatment
Gastroenteritis self limited
Ampicillin for meningitis
Actinomyces Information
Gram + beaded filaments (resembling fungi)
Transmitted by trauma
Anaerobic and not acid fast
Normal oral flora
Causes oral/facial abscesses that drain through sinus tracts, forming yellow “sulfur granules”
Nocardia Information
Gram + beaded filaments (resembling fungi)
Transmitted by inhalation (found in soil)
Acid fast
Pulmonary infections in immunocompromised (also kidney/brain abscesses) and cutaneous infections after trauma in immunocompetent
Actinomyces/Nocardia Treatment
SNAP:
Sulfonamides for nocardia (SN)
Actinomyces: penicillin
Primary TB
ASK RJ
Secondary TB
ASK RJ
Mycobacteria Lab Diagnosis
Gram + Rod
Acid Fast
M. kansasii and M. avium Presentation
M. kansasii: pulmonary TB like symptoms
M. avium: disseminated, non-TB disease in AIDS
TB Symptoms
Fever
Night Sweats
Weight Loss
Hemoptysis
Leprosy Basic Information
Caused by M. leprae (likes cool temperatures)
Infects skin and superficial nerves (glove and stocking loss of sensation)
Reservoir of ARMADILLOS
Treatment: Multidrug therapy (dapsone and rifampin for 6 months + clofazimine and 2-5 years instead for lepromatous)
Tuberculoid Leprosy
Limited to a few hypoesthetic hairless skin plaques
High cell mediated immunity with a largely TH1 immune response (strong immune response)
Could have granulomas
Lepromatous Leprosy
Diffusely over the skin and is communicable
Low cell-mediated immunity with a HUMORAL and TH2 response (weak immune response)
