Microbiology - Bacteria Flashcards
Acinetobacter baumannii
Gram - coccobaillus
Non-lactose fermenting (non-pink colonies on MacConkey agar)
Can cause nosocomial pneumonia, bacteremia, wound infections, esp with war, UTIs
Actinomyces israelii
Gram + rods in filamentous chains
Obligate anaerobe
Molar colonies, yellow sulfur granules → stains purple with H&E (see picture)
a/w poor dentition, lumpy jaw (oral/facial abscesses), pulmonary actinomycosis a/w aspiration
“Israel has yellow sand”
Tx: penicillin
Bacillus anthracis
Gram + boxcar rods in chains
Spore-forming
Polypeptide capsule of D-glutamate
EF (edema factor) mimics adenylate cyclase → ↑ cAMP
LF (A toxins) PA (B toxin)
Cutaneous: boil-like lesions with black eschar
Pulmonary: inhales spores → flu-like symptoms, fever, pulmonary hemorrhage, mediastinitis → widened mediastinum, shock
Gastrointestional
Treat with ciprofloxacin
Bacillus cereus
Gram + rod
Spore-forming
Beta hemolytic
Causes food-borne illness, endopthalmitis (post-surgical, hematogenous)
Emetic type from preformed cereulide toxin (esp. from reheated rice)
Diarrheal type
Bartonella bacilliformis
Gram - rod Sand fly-borne Limited to Andes in Peru Causes Carrion’s disease Phase 1: Oroya fever with hemolytic anemia Phase 2: verruga peruana
Bartonella henselae
Gram - rod
Flea-born
Cat reservoir
Causes cat scratch fever or bacillary angiomatosis (biopsy reveals neutrophilic inflammation)
Bartonella quintana
Gram - rod Body louse-bore Causes trench fever, bacillary angiomatosis
Best media to grow Neisseria?
Thayer-Martin or VPN media
Vancomycin inhibits gram +
Polymyxin inhibits non-Neisseria gram -
Nystatin inhibits fungi
Bordetella pertussis
Gram - coccobacilli
Encapsulated
Requires fatty acid for culture (Bordet-Gengou agar or Regan Lowe charcoal with horse blood) → “Bordet for Bordetella”
Pertussis toxin → overactivation of adenylate cyclase increases cAMP by disabling Gi → impaired phagocytosis
Causes pertussis (whooping cough)
DTaP vaccine for children, Tdap for adults
Borrelia bergdoferi
Lyme disease
Deer tick (Ixodes)
Mice are natural reservoir
Spirochete Stage 1: erythema migrans (expanding bulls-eye rash), fever, lymphadenitis
Stage 2: annular skin lesions, meningoencephalitis, Bell’s palsy, arthritis, carditis
Stage 3: arthritis, neuropathy, 3rd degree heart block
Treat with doxycycline
Borrelia hermsii
Soft-shelled tick Spirochete Endemic relapsing fever
Borrelia recurrentis
Spirochete
Transmitted by body louse
Epidemic relapsing fever
Brucella
Gram - coccoid rod
Facultative intracellular, lives in RES
Consumption of infected milk or milk products, exposure to cattle, pigs
Causes undulant fever/brucellosis
Campylobacter jejuni
Gram - rod (gull-shaped, comma-shaped)
Oxidase +
Grows in 42°C (“Campylobacter likes the campfire”)
Transmitted from puppies, livestock, ingestion of undercooked meat
Intestinal invasion
Causes inflammatory diarrhea, especially in children
Complications include Guillain-Barre syndrome and Reiter’s syndrome (reactive arthritis)
Capnocytophagia canimorsus
Gram - rod Dog > cat bite Resistant to TMP/SMX, aminoglycosides
Causes of VDRL false positives:
Viruses (mono/EBV, hepatitis)
Drugs
Rheumatic fever
Lupus and leprosy
Chlamydia pneumonia
Atypical pneumonia in young adults
Intracellular
Lacks muramic acid in cell wall
Tx: azithromycin or doxycycline
Chlamydia trachomatis
Gram - coccus or rod
Obligate intracellular pathogen (elementary bodies [infective part] and reticulate bodies)
Serovars A, B, C cause infectious keratitis (trachoma)
Serovars D-K cause STIs: cervicitis, urethritis with a clear discharge, reactive arthritis, PID, neonatal conjunctivitis (unilateral), neonatal pneumonia
Serovars L1-L3 cause lymphogranuloma venereum –> tender regional lymphadenopathy that ulcerates to form buboes
Diagnose with nucleic acid amplification test
Treat with azithromycin, doxycycline, tetracycline
Chlamydophila psittaci
Causes Psittacosis
Transmitted from parrots/birds
Clostridium botulinum
Gram + rod
Spore-forming
Obligate anaerobe
Botulinum toxin (pre-formed, heat labile) is a protease that cleaves SNARE proteins and prevents release of acetylcholine at neuromuscular junction
Flaccid paralysis, floppy baby syndrome (honey)
Clostridium difficile
Gram + rod
Obligate anaerobe
Spores resistant to heat, alcohol-based antiseptics
Toxin A (enterotoxin) binds to brush border of gut and toxin B (cytotoxin) depolymerizes actin → psueomembranous colitis → diarrhea → toxic megacolon
Risk factor include older age, Caucasian female, recent hospitalization, recent antibiotic use (esp. clindamycin, ampicillin)
Tx: metronidazole, oral vancomycin, fidaxomin, fecal transplant
Clostridium perfringens
Gram + rod
Obligate anaerobe
Spore-forming (resistant to heat and alcohol-based antiseptics)
Alpha-toxin/lecithinase/phospholipid C splits phospholipids, hemolyzes RBCs
Myonecrosis (gas gangrene), food poisoning
Clostridium tetani
Gram + rod (tennis racket)
Spore-forming
Obligate anaerobe
Tetanospasmin toxin is a protease that cleaves SNARE proteins → prevents release of GABA and glycine → decrease in inhibitory neurotransmitters → increased activation of motor nerves → spastic paralysis, risus sardonicus, trismus (lock jaw)
Toxin travels from wound → motor neuron axons → spinal cord
Corynebacterium diphtheriae
Gram + rod arranged in “Chinese letter” clumps
Catalase +
Contains cytoplasmic granules that stain with aniline dyes like methylene blue
Grow on Tellurite agar or Loffler medium
Causative agent of diphtheria (pseudomembrane), myocarditis → arrhythmias, lymphadenopathy
The toxin can be cleaved into a fragment that catalyzes the NAD+ -dependent ADP-ribosylation of elongation factor 2, thereby inhibiting protein synthesis
Treat with horse antitoxin
Prevent with DTaP vaccine (toxoid)
Coxiella burnetii
Gram - rod
Obligate intracellular
Spore-forming
Aerosol
Contact with goats, sheep, or cattle
Q fever, atypical pneumonia
Eikenella corrodens
Gram - rod
Anaerobic
Human bite wounds
Smells like bleach
Enteroaggregative E. coli (EAEC)
Gram - rod
Oxidase -
Glucose fermenter
Lactose fermenter → colonies turn pink on MacConkey agar
Dauses diarrhea in infants and adults
Enterobacteria
Gram - rod
Lactose fermenter (fast)
a/w endocarditis with abdominal or pelvic surgery
Enterococcus faecalis/faecium
Gram + cocci
Catalse -
Gamma/Non-hemolytic → Group D
Salt and bile-tolerant
Causes complicated UTI, biliary tract infections, subacute endocarditis following GI/GU procedures
Enterohemorrhagic E. coli (EHEC)/Shiga Toxin-producing E. coli (STEC)
Gram - rod
Oxidase -
Glucose fermenter
Lactose fermenter → colonies turn pink on MacConkey agar
Does not ferment sorbital
Causes hemorrhagic colitis, hemolytic uremic syndrome (“H for hold the antibiotics, hamburger, and HUS”)
Shiga-like toxin inactivates 60S ribosome by removing adenine from rRNA
Most common serotype if O157:H7
Enteroinvasive E. coli (EIEC)
Gram - rod
Oxidase -
Glucose fermenter
Lactose non-fermenter
Causes bacillary dysentery
Invades intestinal mucosa (shigella-like) but does not produce shiga toxin
Enteropathogenic E. coli (EPEC)
Gram - rod
Oxidase -
Glucose fermenter
Lactose fermenter → colonies turn pink on MacConkey agar
Causes diarrhea in infants (“P for pediatric”)
Pedestal formation
Adheres to apical surface → flattens villi → prevents absorption
Enterotoxigenic E. coli (ETEC)
Gram - rod
Oxidase -
Glucose fermenter
Lactose fermenter → colonies turn pink on MacConkey agar
Causes watery diarrhea in travelers (“T for traveler”) and children
LB (heat labile) toxin is cholera toxin-like→ overactivates adenylate cyclase → ↑ cAMP → ↑ Cl- and H20 secretion in gut
ST (heat stable) toxin → overactivates guanylate cyclase → ↑ cGMP → ↓ resorption of NaCl and H20 in gut
Erhlichia chaffeensis
Gram -
Obligate intracellular in hematopoetic cells
Lone star tick
Human Monocytic Erhlichiosis
Cytoplasmic mulberry inclusion in leukocytes (see picture)
Escherichia coli
Gram - rod
Lactose fermenter → colonies turn pink on MacConkey agar
Colonies show green metallic sheen on EMB agar
Oxidase -
Encapsulated
Most common cause of UTI
fimbriae → cystitis, pyelonephritis
K capsule → pneumonia, neonatal meningitis
LPS endotoxin → septic shock
Escherichia coli K1
Gram - rod Lactose fermenter Sialic acid capsule Can cause meningitis, bacterimia in newborns
For what organisms do you use Sabouraud agar?
Fungi
Franciscella tularensis
Gram - coccobacilli
Facultative intracellular pathogen lives in macrophages
Requires cysteine in grow
Acquired via exposure to ticks, rabbits, deer fly
Causes tularemia
Fusobacterium nucleatum
Gram - rod Anaerobic Causes periodontal disease, pleuropulmonary infection, linked to colorectal cancer
Gardnerella vaginalis
Gram variable rod
β-hemolytic
Elevated in bacterial vaginosis –> thin, grayish/white discharge and fishy odor with KOH
Diagnose with elevated pH (>4.5), Whiff test, clue cells
Treat with metronidazole or clindamycin
Group B Streptococci
Gram + cocci Catalase - Beta-hemolytic CAMP test + Bacitracin resistant Common cause of meningitis, bacteremia in newborns
HACEK
Haemophilus parainfluenzae, Aggregatibacter acetomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae a/w endocarditis with negative blood cultures
Haemophilus ducreyi
Gram - coccobacillus
Culture with enriched agar (factors X and V + CO2)
Causes painful ulcers (chancroid) and possibly inguinal lymphadenopathy
Haemophilus influenzae
Gram - coccobacilli
Oxidase +
Culture on blood agar requires factors X (hematin, heat stable) and V (NAD+, heat labile) to grow; S. aureua supplements NAD+
Type b (Hib) is encapsulated (polyribose-ribitol phosphate) and causes meningitis in infants, epiglottitis, cellulitis, pneumonia (secondary, COPD)
Non-typable/non-encapsulated causes conjuctivitis, otitis media, sinusitis
IgA protease cleaves IgA to colonize respiratory mucosa
Tx mucosal infections: amoxicillin ± clavulanate
Tx meningitis: ceftriaxone; prophylaxsis for close contacts with rifampin
Hib vaccine (conjugated)
Helicobacter pylori
Gram - spiral rod (comma-shaped)
Catalase +
Oxidase +
Urease +
Silver stain
Type I carcinogen
Causes gastritis, ulcers, adenocarcinoma, and MALT lymphoma
Contains urease, VacA, CagA
Protective against asthma, active TB, esophageal cancer
Dx: urea breath test, fecal antigen test
Tx: triple therapy (PPI + clarithromycin + amoxicillin or metronidazole)
Hemolytic uremic syndrome
a/w EHEC (shiga-like toxin producing E. coli)
S&S: anemia, thrombocytopenia, acute renal failure
Toxin damaged endothelium → microthrombi form (↓ platelets) → mechanical hemolysis (schistocytes) + decreased renal blood flow
How do superantigens cause toxic shock syndrome?
Toxins (TSST-1 for staph, exotoxin A for strep) bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-γ and IL-2
S&S: fever, rash, shock
Klebsiella pneumoniae
Gram - rod
Lactose fermenter (fast) → mucoid colonies turn pink on MacConkey agar
Encapsulated
Urease +
Thick mucoid capsule –> current jelly suputum
Pneumonia in malnourished, alcoholics, diabetics, nosocomial UTI
Lactobacilli (L. acidophilus)
Gram + rod Converts lactose to lactic acid Normal oral flora that can cause dental caries
Legionella pneumophila
Gram - rod, primarily intracellular
a/w water aerosols
Doesn’t gram stain well → silver stain
LPS can be detected in a urine sample
Culture on charcoal yeast with iron and cysteine
Causes high fever + GI symptoms + pneumonia (typical and atypical), hyponatremia
Treat with macrolide or quinolone
Leptospira interrogans
Transmitted through water infected with animal urine
Leptospirosis: acute febrile illness with conjunctival suffusion (erythema without exudate), jaundice, photophobia, renal failure
Treat with doxycycline
Listeria monocytogenes
Gram + rod
Catalase +
CAMP test +
Beta-hemolytic
Facultative intracellular → ActA → “rocket tails” via actin polymerization
Listerolysin O → only gram + organisms to have LPS
Acquired by ingestion of unpasteurized dairy and deli meats, transplancental and vaginal transmission
Cause of meningitis in newborns, amnionitis, spontaneous abortion, gastroenteritis
Can grow in the cold
Tx meningitis with ampicillin
Moraxella catarrhalis
Gram - diplococci Oxidase + Causes conjunctivitis, otitis media, sinusitis
Mycobacterium avium-intracellulare
Causes TB-like disease in AIDS
When CD4 count < 50 → MAC prophylaxis with azithromycin
Mycobacterium leprae
Acid-fast bacillus
Likes cool temperatures so affects skin and nerve of the hands and feet
Armadillos serve as reservoir
Lepromatous form (diffuse cutaneous, communicable) → Th2 response (- lepromin skin test); treat with dapsone, rifampin, clofazimine for 2-5 years
Tuberculoid form → Th1 response (+ lepromin skin test); treat with dapsone and rifampin for 6 months
Mycobacterium marinum
Fish tank granuloma
Mycobacterium tuberculosis
Gram + like (but won’t gram stain)
Obligate aerobe
Mycolic acid in cell envelope –> acid fast stain
Culture on Lowenstein-Jensen agar
Cord factor is a virulence factor that causes the bacteria to grow in chains/serpentine cords and inactivates neutrophils, damages mitochondria, and releases TNF
Causes TB (can be latent, reactivated, miliary, disseminated)
Characterized by Ghon complex in mid zone of lung (primary infection), caseating granuloma, or secondary infection (cavitary lesion in upper lobes due to high PO2)
Can spread hematogenously and effect vertebrae (Pott disease) and cranial nerves
Treat with RIPE
Mycoplasma genitalium
No cell wall Causes urethritis
Mycoplasma hominis
No cell wall Causes endometritis, salpingitis, PID
Mycoplasma pneumoniae
No cell wall → no gram stain
Grows on Eaton agar (requires cholesterol)
Atypical pneumonia in young adults in close quarters; CXR findings worse than clinical appearance
High titer of cold agglutinins (IgM) which can lyse RBCs
Tx: macrolide, doxycycline, fluoroquinolone
Name some obligate anaerobes
Clostridium
Bacteroides
Actinomyces
Obligate anaerobes lack catalase and/or superoxide dismutase and are suseptible to oxidative damage
Aminoglycosides are ineffective because they require oxygen to enter into the bacteria
Name some obligate anerobes
Nocardia
Pseudomonas
Mycobacterium tuberculosis
Neisseria gonorrheae
Gram - diplococci (often found intracellularly)
Oxidase +
No capsule
Glucose fermenter
Maltose non-fermenter
IgA protease
Causes urethritis, vulvovaginitis (girls, postmenopause), cervicitis (premenopause) with mucupurulent discharge, PID, prostatitis, epididymitis, septic arthritis, neonatal conjunctivitis (bilateral)
Treat with ceftriaxone + azithromycin
No vaccine due to antigenic variation of the pili
Neisseria meningiditis
Gram - diplococci
Catalase +
Oxidase +
Encapsulated
Maltose fermenter
Glucose fermenter
Lipooligosaccharide toxin IgA protease contributes to morbidity and mortality
Common cause of meningitis in infants, children, and adults, Waterhouse-Friderichsen syndrome (primary acute adrenal insufficiency 2/2 hemorrhagic necrosis), cutaneous manifestations (non-blanching petechial, purpuric, or ecchymotic rash)
Long-term sequalae include amputations, hearing loss, skin scarring
Tx: ceftriazone or penicillin G; prophylaxis in close contacts with rifampin, ciprofloxacin, or ceftriaxone
Nocardia
Gram +, branching
Obligate aerobe
Urease +
Weakly acid fast
Causes cavitary pneumonia and brain abscess in immunocompromised and cutaneous infections after trauma in immunocompetent
Tx: sulfonamides
Orientia tsutsugamushi
Gram - coccobacillus Mite-borne Scrub typhus
Pasteurella multicodia
Gram - coccobacillus
Cat > dog bites
Causes cellulitis, osteomyelitis
Resistant to clindamycin
Characteristic mouse-like odor (indole +)
Porphyromonas gingivalis
Can cause periodontitis and diabetes, CVD, adverse pregnancy outcomes
Propionibacterium acnes
Gram + rod
Anaerobic
Causes acne, chronic blepharitis, infection of prosthetic devices, endopthalmitis (post-surgical)
Proteus mirabilis
Gram - rod
Lactose non-fermenter
Oxidase -
Urease +
Motility causes “swarming” on agar
Causes UTI, pyelonephritis, kidney stones (MAP/Struvite)
Pseudomonas aeruginosa
Gram - rod
Lactose non-fermenter
Oxidase +
Catalse +
Obligate aerobe
Smells like artificial grape
Produces blue-green pigment (pyocyanin)
Causes pneumonia in CF patients, nosocomial pneumonia, hot tub folliculitis, otitis externa, UTIs, burn wounds, infectious keratitis, endophthalmitis (post-traumatic), otitis externa, osteomyelitis (diabetics and IVDU), ecythyma gangrenosum (dermatologic lesions) in immunocompromised/neutropenic
Treat with aminoglycoside plus extended-spectrum penicillin (e.g. piperacilin)
Exotoxin A inactivates elongation factor 2
Rickettsia akari
Gram - coccobacillus
Obligate intracellular
Mite-borne
Rickettsialpox
Black eschar mimics anthrax
Treat with doxycycline
Rickettsia prowazekii
Gram - coccobacillus
Obligate intracellular
Louse-borne
Epidemic typhus fever
Tx: doxycycline
Rickettsia rickettsii
Gram - coccobacillus
Obligate intracellular in endothelial cells
Actin polymerization
American dog tick (Dermacentor)
Rocky Mountain Spotted Fever (rash starts on wrists and ankles and spreads to trunk, palms, and soles)
Treat with doxycycline
Rickettsia typhi
Gram - coccobacillus
Obligate intracellular
Flea-borne
Murine endemic typhus
Tx: doxycycline
Salmonella
Gram - rod
Oxidase -
Glucose fermenter
Lactose non-fermenter
Encapsulated (Vi antigen protects from opsonization and phagocytosis)
H2S+
Intestinal invasion
Causes bloody enterocolitis or bacteremia (immunocompromised), osteomyelitis in sickle cell disease
Salmonella typhi
Salmonella paratyphi
Gram - rod
Oxidase -
Glucose fermenter
Lactose non-fermenter
H2S+
Intestinal invasion
Has flagella (“salmon swim”)
Causes bloody diarrhea, typhoid fever (rose spots on the abdomen, fever, headache, diarrhea)
Can result in carrier state if bacteria colonizes the gallbladder
Serratia marcrescens
Gram - rod
Lactose fermenter (slow)
Catalase +
Produces a red pigment
Can cause UTI (often nosocomial and drug resistant)
Shigella dysenteriae
Gram - rod
Oxidase -
Glucose fermenter
Lactose non-fermenter
Intestinal invasion
Type 1 causes inflammatory diarrhea and produces shiga toxin → inactivated 60S ribosome by removing adenine from rRNA
May cause hemolytic uremic syndrome
Shigella flexnerii
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Causes inflammatory diarrhea Most common in developing countries
Shigella sonnei
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Causes inflammatory diarrhea Most common in the US
Staphylococcus aureus
Gram + cocci
Catalase +
Coagulase +
a/w acute endocarditis in IV drug abusers → large vegetations that destroy the valve, commonly tricuspid
Secondary bronchopneumonia, blepharitis, conjuctivitis, endophthalmitis (post-surgical, post-trauma, hematogenous), otitis externa, sinusitis, osteomyelitis in children (most common, adheres to collagen), furuncle
Characterized by focal destructiveness, puss, neutrophilic inflammation, and abscess formation
Can cause scalded skin syndrome when exofoliative A and B toxins cleave desmoglein 1
Toxic shock syndrome toxin (TSST-1) is a superantigen → toxic shock syndrome
Protein A binds Fc region of IgG → prevents opsonization and phagocytosis
Staphylococcus epidermidis
Gram + cocci
Catalase +
Coagulase -
Novobiocin sensitive
Urease +
a/w endocarditis with prosthetic valves, complicated catheter-associated UTI, endophthalmitis (post-surgial), otitis externa
Makes biofilm
Characterized by focal destructiveness, puss, neutrophilic inflammation, and abscess formation
Staphylococcus saprophyticus
Gram + cocci
Catalase +
Coagulase -
Novoiocin resistant
Urease +
a/w UTI in young, sexually active females
Streptobacillus moniliformis
Gram - rod, branching Rat bite fever
Streptoccocus bovis
Gram + cocci
Catalase -
Gamma/Non-hemolytic → Group D
a/w subacute endocarditis with colorectal cancer
Streptococcus agalactiae
Gram +
Catalase -
Beta-hemolytic → Group B
Bacitracin resistant
CAMP factor +
Hippurate test +
Encapsulated
Causes meningitis in newborns
Streptococcus mutans
Gram + cocci Alpha hemolytic Normal oral flora that can cause dental caries
Streptococcus pneumoniae
Gram + diplococci, lancet-shaped
Catalase -
Alpha-hemolytic
Optochin sensitive
Bile soluble
Encapsulated
a/w endocarditis in alcoholics
Most common cause of community-acquired pneumonia, meningitis in infants, children, and adults, otitis media, conjuctivitis, sinusitis
IgA protease cleaves IgA to colonize respiratory mucosa
Streptococcus pyogenes
Gram + cocci in chains
Catalase -
Beta-hemolytic
Group A
Bacitracin sensitive
PYR +
a/w pharyngitis, pyoderma (impetigo, erysipelas, cellulitis, necrotizing fasciitis), scarlet fever (sandpaper-like rash with fever, sore throat, circumoral pallor, strawberry tongue), rheumatic fever/heart disease (M-protein mimicry)
Streptolysin O degrades cell membranes, lyses RBCs; anti-streptolysin O used to dx rheumatic fever
Exotoxin A (superantigen) → streptococcal toxic shock syndrome
Viridians group streptococci
Gram + cocci
Catalase -
Alpha-hemolytic
Optochin resistant
Not bile soluble
Synthesize dextrans from sucrose to adhere to tooth enamel and fibrin-platelet aggregates
Streptococcus sanguinis a/w subacute endocarditis of previously damaged valves → small vegetations that don’t destroy the valve
Streptococcus mutans a/w dental caries
Treponema pallidum
Spirochete
Causes syphilis (1° - painless ulcers, 2° - patches, rashes on palms and soles, conylomata lata, 3° - gummas, aortitis, neurosyphilis), congenital syphilis (snuffles, saber shins, saddle nose, CN VIII deafness, Hutchinson teeth, mulberry molars)
Diagnose with darkfield microscopy, fluorescent antibody staining, nontreponemal and treponemal serology tests
Treat with penicillin G
Trichomonas vaginalis
Flagellated protozoan
Causes trichomoniasis –> copious yellow/green, frothy discharge, odor, itching, burning, inflammation
Dx: motile trophozoites on wet mount (see picture), strawberry cervix, pH > 4.5
Tx: metronidazole for patient and sexual partner
Ureaplasma urealyticum
No cell wall
Urease +
Causes urethritis
Vibrio cholerae
Gram - rod (comma-shaped)
Oxidase +
Grows in alkaline media
Glucose fermenter
Can cause voluminous “rice-water” diarrhea
Cholera toxin overactivates adenylate cyclase → ↑ cAMP by permanently activating Gs → ↑ Cl- and water secretion in the gut
Vibrio parahemolyticus
Gram - rod
Oxidase +
Glucose fermenter
Can cause secretory diarrhea
Commonly transmitted from undercooked seafood (increasing with global warming)
Vibrio vulnificus
Wound exposure to shellfish or warm salt/brackish water
Can cause hemorrhagic bullae
What bacterial diseases are transmitted by body louse?
Trench fever (Bartonella quintana), epidemic typhus (Rickettsia prowazekii), epidemic relapsing fever (Borrelia recurrentis)
What bacterial diseases are transmitted by fleas?
Murine endemic typhus (Rickettsia typhi), bubonic plague (Yersinia pestis), cat scratch fever (Bartonella henselae)
What bacterial diseases are transmitted by mites?
Scrub typhus (Orientia tsutsugamushu), Rickettsialpox (Rickettsia akari)
What bacterial diseases are transmitted by ticks?
Lyme (Borrelia burgdorferi), STARI, endemic relapsing fever (Borrelia hermsii), RMSF (Rickettsia rickettsii), sometimes tularemia (Franciscella tularensis) and Q fever (Coxiella brunetti)
What can cause a false negative PPD test?
Steroid use
Malnutrition
Immunocompromised
Sarcoidosis
What can cause a positive PPD test?
Current TB infection
Past TB exposure
BCG vaccination → interferon-gamma release assay more specific (fewer false positives); measures INF-gamma released by T lymphocytes when exposed to Mycobacterium tuberculosis antigens
What conjucated vaccines are available?
Conjugated vaccines are made for encapsulated bacteria whereby capsule polysaccharides are joined to a carrier protein to stimulate T cell activation and class switching
Available for PCV/Prevnar, Hib, and meningococcal vaccines
What CSF findings are consistent with bacterial meningitis?
Gram stain findings
Antigen findings
↑ opening pressure
↑ PMNs
↑ protein
↓ glucose
What diseases are caused by Ixodes ticks (deer ticks)?
Lyme disease Babesia Anaplamosis
What is a Jarisch-Herxheimer reaction?
Flu-like syndrome after starting antibiotics 2/2 killed bacteria releasing pyrogens
What is different about the cell membranes/walls of mycoplasma and mycobacteria?
Mycoplasma do not have cell walls, membranes contain sterols
Mycobacteria cell walls contain mycolic acid (acid fastness) and a high lipid content
What is hemolytic uremic syndrome?
microangiopathic hemolytic anemia, thrombocytopenia, glomerular thrombosis
What structures are unique to gram + organisms?
Cell wall made of peptidoglycans
Lipoteichoic acid (lipid + teichoic acid) → induces TNF, IL-1
What structures are unique to gram - organisms?
Outermembrane contains endotoxins (lipopolysaccharide); Lipid A induces TNF and IL-1
Which age groups are most affected by Neisseria meningitidis?
Infants, children, and adults
Which age groups are most affected by Streptococcus pneumoniae?
Infants, children, and adults
Which bacteria cause meningitis in adults?
Streptococcus pneumoniae Neisseria meningitidis Mycobacteria
Which bacteria cause meningitis in children?
Neisseria meningitidis Streptococcus pneumoniae
Which bacteria cause meningitis in infants?
Neisseria meningitidis Haemophilus influenzae Streptococcus pneumoniae
Which bacteria cause meningitis in newborns?
Group B streptoccoci Escherichia coli Listeria monocytogenes
Which orgninisms are acid fast?
Mycobacterium (e.g TB)
Nocardia (weakly acid fast)
Yersinia enterocolitica
Gram - rod
Oxidase -
Glucose fermenter
Lactose non-fermenter
Transmitted from pet feces, contaminated milk, pork
Causes enterocolitis, reiter’s syndrome, mesenteric lymphadenitis, extraintestinal infection
May mimic Chron’s disease or appendicitis (“take yer appendix out”)
Yersinia pestis
Gram - rod
Lactose non-fermenter
Oxidase -
Flea-borne (rats and prarie dogs are reservoirs)
Causes bubonic plague (painful buboes) or pneumonic plague
Yersinia pseudotuberculosis
Gram - rod
Oxidase -
Glucose fermenter
Lactose non-fermenter
Causes enterocolitis, reiter’s syndrome, mesenteric lymphadenitis, extraintestinal infection
May mimic appendicitis (“take yer appendix out”)
Pelvic inflammatory disease (PID)
Causes: chlamydia (subacute) or gonorrhea (acute)
S&S: cervical motion tenderness (chandelier sign), purulent cervical discharge, may include salpingitis, endometritis, hydrosalpinx, tubo-ovarian abscess, Fitz-Hugh-Curtis syndrome (ascending infection of the liver capsule with adhesion to the peritoneum)
Bacteroides fragilis
Gram - rod
Anaerobic
Unique surface polysaccharides favor abscess formation
Commonly isolated in intraabdominal infections
Which bacteria invade the intestinal mucosal causing bloody diarrhea?
Salmonella
Shigella
Enteroinvasive E. coli (EIEC)
Campylobacter jejuni
Entamoeba histolytica
Bacterial methods of acquiring genes for virulence and antibiotic resistance
Transformation = uptake of exogenous DNA
Transduction = bacteriophage transfers DNA
Conjugation = one-way transfer of plasmid DNA through sex pilus
Spontaneous or induced mutations
Transposon = mobile genetic elements that can transfer from plasmids to bacterial chromosome or vice versa
Tropheryma whipplei
Gram +
PAS + foamy macrophages
Causes Whipple disease: malabsorption, cardiac symptoms, arthralgias, neurologic symptoms
