Bacteriology Flashcards
Gram-positive cocci in clusters Catalase-positive Coagulase-negative Novobiocin-sensitive Whitish, non-hemolytic colonies on blood agar
Staphylococcus epidermidis
Gram-positive cocci in grape-like clusters
B-hemolytic yellow or golden colonies on blood agar
Catalase-positive
Coagulate-positive
Salt-tolerant on mannitol salts agar
“Gold” color is due to pigment staphyloxanthia
Toxin: TOXIC SHOCK SYNDROME TOXIN (TSST-1)
Mechanism: Bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-y and IL-2 –> shock
Manifestation: Toxic shock syndrome: fever, rash, shock; other toxins cause scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin)
Staphylococcus aureus
Gram-positive cocci in clusters Catalase-negative Coagulase-negative Novobiocin-resistant Whitish, non-hemolytic colonies on blood agar
Staphylococcus saprophyticus
Gram-positive cocci in chains B-hemolytic Catalase-negative Bacitracin-sensitive Lancefield group A Positive PYR test
Toxin: STREPTOLYSIN O
Mechanism: Protein that degrades cell membrane
Manifestation: Lyses RBCs; contributes to B-hemolysis; host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of post streptococcal glomerulonephritis)
Streptococcus pyogenes
Gram-positive cocci in chains B-hemolytic Catalase-negative Bacitracin-resistant Hydrolyze hippurate CAMP test-positive Lancefield group B Grow using LIM broth
Streptococcus agalactiae (group b strep)
Gram-positive cocci in chains Catalase-negative Gamma (nonhemolytic) colonies Lancefield group D Bite and optochin-resistant Hydrolyzes esculin in bile-esculin agar (BEA) Positive PYR test E. Faecalis can grow in 6.5% NaCl S. Bovis cannot grow in 6.5% NaCl
Enterococcus Faecalis ( group D strep)
Aerobic, gram-positive box-car like rods nonmotile
Spore-forming
Medusa head morphology
Bacillus anthracis
Aerobic, gram-positive spore-forming rod
Motile
Chinese fried rice syndrome
Bacillus cereus
Anaerobic, gram-positive, spore-forming rods
Spore is at one end (terminal spore) so organism looks like a tennis racket
Clostridium tetani
Anaerobic, gram-positive, spore-forming rods
Canned goods (bulging)
Honey
Botulinum toxin—> flaccid paralysis
Clostridium botulinum
Triad of botulism
- Symmetric descending flaccid paralysis (with prominent bulbar involvement)
- Absence of fever
- Intact sensorium
Anaerobic, gram-positive, spore-forming rods
Double hemolysis on blood agar
Growth on egg-yolk agar
Clostridium perfringens
Anaerobic, gram-positive, spore-forming rods
Exotoxins in stool detected by cytopathic effect on cultured cells or ELISA
colon
Fecal-oral route
Hospital personnel
Clostridium difficile
Nonbloody diarrhea associated with pseudomembranes (yellow-white plaques) on the colonic mucosa
Toxic megacolon can occur
Pseudomembranous colitis
Aerobic, non-spore forming, non-motile gram-positive rods
Club or comma-shaped rods arranged in V or L shape
Looks like Chinese characters
Metachromatic granules
Black colonies on tellurite plate
Toxigenicity detected using modified elek test
Corynebacterium diphtheriae
Gram-negative “kidney-bean” diplococci
Large polysaccharide capsule
Oxidase-positive colonies on chocolate agar
Ferments maltose and glucose
Neisseria meningitidis
Gram-negative “kidney-bean” diplococci
Insignificant capsule
Oxidase-positive colonies on Thayer-Martin medium
Ferment glucose only
Neisseria gonorrhoeae
Small gram-negative (coccobacillary rods) rods
Requires factor X (hemin) and V (NAD) for growth (chocolate agar)
Satellite phenomenon around S. Aureus colonies
Haemophilus influenzae
Small gram-negative rods
Culture on Bordet-Go agar or Regan-Lowe charcoal medium
Bordetella Pertussis
Poorly gram-negative rods visualize with silver stain
Facultative intracellular bacteria
Culture on charcoal yeast extract agar
Rapid urinary antigen test
Legionella pneumophila
Facultative gram-negative rods
Lactose-fermenting colonies on EMB or MacConkey’s agar
Green sheen on EMB agar; metallic sheen
TSI agar shows acid slant and acid butt with gas but no H2S
Typing by O and H antigens
Escherichia coli
Non-lactose-fermenting, gram-negative rods
Produce no gas from the fermentation of glucose
Do not produce H2S
Nonmotile
Have O antigens
Cultured in XLD medium
Shigella spp
Shigella transmission
4Fs Food Fingers Feces Flies
Gram-negative rods
Obligate aerobe
Non-lactose-fermenting
Oxidase-positive
Pyocyanin (blue-green pigment)
Sweet grape-like odor
Grown on Cetrimide agar
Pseudomonas aeruginosa
Facultative gram-negative rods
Non-lactose-fermenting
Urease-positive
Swarming motility
Alkaline urine
Struvite
Magnesium-ammonium-phosphate
Staghorn calculi
Proteus mirabilis
Facultative gram-negative rods with large polysaccharide capsule
Extended spectrum beta-lactamase (ESBL)
Urease-positive
Current jelly sputum
Most common cause in alcoholics
Klebsiella pneumoniae
Curved gram-negative rods
Microaerophilic
Urease-positive
Helicobacter pylori
Comma-shaped gram-negative rods
Microaerophilic
Positive oxidase and catalase test
Grows well at 42C on Skirrows agar
Campy medium (with antibiotics)
Gullain-barre syndrome
Reiter’s syndrome
Campylobacter jejuni
Comma-shaped gram-negative rods
Motile
Oxidase-positive
Cultured on thiosulfate citrate bile salts sucrose (TCBS) agar
Shooting star motility
Vibrio spp
Encapsulated, pleomorphic gram-negative bacillus
Bipolar densities (Donovan bodies) look like closed safety pins
Small painless papule ulcerates to form beefy red ulcer with velvety surface
Pseudobuboe formation
Granuloma inguinale (donovanosis)
Gram-negative rods
Reservoir: domestic animals
Transmission: oro-fecal route
Mesenteric adenitis (pseudo appendicitis)
Small gram-negative rod
Culture on chocolate agar with heme (factor x)
PE: painful genital ulcer
Chancroid
Facultative gram-variable rod
Clue cells present
Positive whiff test (fishy odor)
Malodorous vaginal discharge
Bacterial vaginosis
Dog reservoir
Transmission: dog tick (dermacentor) bite
Forms morulae in cytoplasm of monocytes
Ehrlichia chaffeensis
Gram-negative rod
Normal oral flora of cats
Cat-scratch fever in immunocomponent individuals
Bacillary angiomatosis in immunocompromised
Transmission: cat bite or scratch
Cat-scratch disease
Obligate intracellular bacteria
Energy parasites that use host ATP
Cell wall lacks muramic acid
Grown in cycloheximide culture
Cytoplasmic inclusions in Giemsa
Chlamydia trachomatis
Thin, coiled spirochetes
Hook at one or both pointed ends (shepherd’s crook)
Obligate aerobe
Grown on Ellinghausen-McCullough-Johnson-Harris (EMJH) medium or Fletcher’s medium
Leptospira interrogans
Rapid changes due to programmed rearrangements of bacterial DNA encoding surface proteins
Transmitted by human body louse (Pediculus humanus)
Diagnostic test of choice is microscopy
DOC is tetracycline or erythromycin
Relapsing fever ( borrelia recurrentis)
C. Trachomatis types D-K
Late-onset (2-4weeks)
Striking tachypnea, characteristic paroxysmal cough (staccato cough), absence of fever, and eosinophilia
Neonatal pneumonia
C. Trachomatis types L1-L3
Papule or vesicular which ulcerates and leads to suppurative inguinal lymphadenitis (buboes)
Positive Frei test
Lymphogranulomq venereum
C. Trachomatis types D-K Most common cause of STDs Neonatal conjunctivitis Neonatal pneumonia Associated with Reiter's syndrome
Genital tract infections
Aerobic, acid-fast rods
Ziehl-Neelsen
Lowenstein-Jensen medium
Luciferase assay
Mycobacterium tuberculosis
Small gram-negative rods without a capsule
Contaminated dairy or direct contact
Tx: doxycycline plus rifampicin
Brucellosis (undulating fever)
Small gram-negative rods
Reservoir: rabbits, deer, and rodents
Transmission: ticks, aerosols, contact and ingestion
Tx: streptomycin or gentamicin
Tularemia (francisella tularentia)
Most virulent bacteria Small gram-negative rods with bipolar (safety pin) staining Reservoir: wild rodents Transmission: flea bite, inhalation PE: buboes, cutaneous hemorrhage Treatment: streptomycin and tetracycline
Yersinia pestis
Short, encapsulated gram-negative rod that exhibits bipolar staining
Buttery colonies with musty odor due to indole production
Reservoir: cats and dogs
Transmission: animal bites
Treatment: penicillin G
Pasteurella multocida
Anaerobic, gram-negative rods Predominant anaerobe of human colon Spreads to blood or peritoneum during bowel trauma, perforation or surgery Synergistic pathogenicity Low with endotoxic activity Foul-smelling discharge Abdominal abscess
Bacteroides fragilis
