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Flashcards in Bacteriology Deck (72):


  • Gram positive cocci in clusters
  • Protein A binds Fc-IgG, inhibiting complement activation and phygocytosis
  • causes
    • inflammatory disease: skin infection, organ abscesses, pneumonia, endocarditis, osteomyelitis
    • Toxin mediatad disease: TOSS-1, scalded skin syndrome ( exfoliative toxin), rapid onset of food poisoning (enterotoxin)
    • MRSA: serious nosocomial and community acquired infections. Resistant to methicillin d/t altered penicilin binding protein
  • Toxins
    • TSST: super antigen that binds MHC II and TCR leading to polycolonal T cell activation ( fever, vomiting, shock, end organ failure
    • Food poisoning: ingestion of preformed toxins ( 2-6 hr incubation). Heat stable toxin is not destroyed by cooking


Staphylococcus Epidermidis

  • Gram positive, cocci, catalase positive, coagulase (-), novobiocin sensitive
  • infects prostatic devices and intravenous catheters by producing an adherent biofilm
  • component of normal skin flora
  • contaminates blood culture


Staphylococcus Saprophyticus

  • Gram positive, Cocci, Catalase positive, Coagulase negative
  • novobiocin resistant
  • second most common cause of UTI in young women ( after E. coli)


Streptococcus pneumoniae

  • Gram positive, diplococci, catalase negative, alpha hemolytic
  • Causes
    • Meningitis
    • Otiti media (children)
    • Pneumonia
    • sinusitis
  • encapsulated (no virulence without capsule)
  • IgA protease


Viridans streptococci

  • Gram positive, Cocci, catalase negative, alpha hemolysis
  • no capsule, optochin resistant, bile insoluble
  • normal flora of oropharynx and cause dental carries (S. mutans) and subcute bacterial endocarditis at damaged valves


Streptococcus pyogenes

Gram positive, Cocci, Catalase negative, Beta hemolysis

  • bacitracin sensitive
  • Causes
    • Pyogenic: pharyntitis, cellulitis, impetigo
    • Toxigenic: scarlet fever, toxic shock syndrome, necrotizing faciitis
    • Immunologic: rheumatic fever, acute glomerulonephritis
  • Antibodies to M proteins enhance host defenses but can give rise to rheumatic fever
  • JONES criteria
    • joints
    • carditis
    • nodules
    • erythema nodosum
    • syndenham chorea
  • impetigo more commonly preceeds glomerulonephitis than pharyngitis
  • Scarlet fever: scarlet rash with sandpaper like texture, straberry tongue, circumoral pallor


Streptococcus agalactiae

Group B strep

Gram positive, Cocci, chains, catalase (-), beta hemolytic

  • Bacitracin resistant
  • Colonizes vagina
  • Causes ( mainly in babies)
    • penumonia
    • meningitis
    • sepsis
  • Produces CAMP factor which enlarges the area of hemolysis formed by S. aureus.
  • Hippurate test positve
  • screen pregnant women at 35-57 weeks: positive cultures requires intrapartum penicillin prophylaxis



Gram positive, Cocci, catalase negative, no hemolysis, grown in 6.5% NaCl and bile

  • E. faecalis and E. faecium
  • normal colonic flora that are penicillin G resistant
  • cause UTI, biliary tract infections, subacute endocarditis
  • VRE: cause nosocomial infection


Streptococcus bovis

Gram positive, cocci, catalase negative, grows in bile, does not grow in 6.5% NaCl

  • colonizes the gut
  • can cause bactermia and subacute endocarditis in colon cancer patients
  • Bovis in the blood= cancer in the colon


Corynebacterium dipthaeriae

  • Diphtheria
  • exotoxin encoded by beta prophage
    • inhibits protein synthesis via ADP- ribosylation of EF-2
  • Symptoms
    • pseudomembranous pharyngitis
    • lymphadenopathy
    • myocarditis
    • arrythmia
  • Gram postive rod
  • metachromatic (red and blue) granules
  • Elek test for toxin
  • black colonies on cystine tellurite agar


  • ADP ribosylation
  • Beta prophage
  • Corynbacterium
  • Diptheriae
  • Elongation factor 2
  • Granules


Spore forming bacteria

  • Bacillus anthracis (G+)
  • Clostridium perfringens (G+)
  • C. tetani (G+)
  • B. cereus
  • C. botulinum
  • Coxiella burnetii


Clostridium Tetani

G (+), spore-forming, obligate anaerobic bacilli

  • Produces tetanospasmin
    • exotoxin cause tetanus
    • tetanus toxin are proteases that cleave releasing proteins for neurotransmitters
  • Induces tetanic paralysis
    • blocks glycine and GABA release from Renshaw cells in spinal cord
    • causes spastic paralysis, trismus (lockjaw), risus sardonicus


Clostridium Botulinum

G (+), spore-forming, obligate anaerobic bacilli

  • Produces preformed, heat labile toxin that inhibits ACh receptor release at NMJ
  • causes botulism
  • Disease in adults: ingetion of preformed toxin
  • Disease in babies: ingestion of spores ( floppy baby syndrome)
  • causes flaccid paralysis


Clostridium perfringens

G (+), spore-forming, obligate anaerobic bacilli

  • produces alpha toxin (lecithinase) a phospholipase that causes myonecrosis and hemolysis
  • gas gangrene


Clostridium difficile

G (+), spore-forming, obligate anaerobic bacilli

  • Toxin A
    • enterotoxin
    • binds to brush border of gut
  • Toxin B
    • cytotoxin
    • cytoskeletal disruption via actin depolarization
    • pseudomembranous colitis
    • diarrhea
  • often secondary to antibiotic use
  • Diagnosed by detection of one or both toxins in stool
  • Tx: metronidazole (Flagyl) or PO vancomycin


Bacillus anthracis

  • Gram positive, spore forming rod
  • produces anthrax toxin
  • polypeptide capsule (containing D-glutamate)

Cutaneous anthrax

  • Boil like lesion--> ulcer with back eschar
  • painless, necrotic
  • uncommonly progresses to bacteremia and death

Pulmonary anthrax

  • inhalation of spores
  • flu like symptoms that rapidly progresses to fever, pulmonary hemorrhage, mediastinitis and shock
  • woolsorter's disease: inhalation of spores from contaminated wool


Listeria monocytogenes

  • Facultative intracellular microbe
  • acquired by ingestion of unpasteurized dairy produces and deli meats via transplacental transmission or by vaginal transmission at birth
  • "Rocket tails": actin polymerization that allow them to move through cytoplasm and into cell membrane
  • Gram positive, produces LPS
  • Pregnant women: septicemia, spontaneous abortion
  • granulomatosis infantiseptica, neonatal meningitis, meningitis in immunocompromised, mild gastroenteritis in healthy
  • Tx: ampicillin in infants, immunocompromised and elderly for meningitis



  • Gram positive anaerobic
  • not acid fast
  • normal oral flora
  • causes oral/facial abscesses that drain through sinus tracts, forms yellow "sulfur granules"
  • Tx: penicillin



  • Gram positive aerobe
  • acid fast (weak)
  • found in soil
  • causes pulmonary infections in immunocompromised and cutaneous infection after trauma in immunocompromised
  • Tx: sulfonamides


Mycobacterium tuberculosis

  • acid fast
  • sxs: fever, night sweats, weight loss, hemoptysis
  • cord factor in virulent strains inhibits macrophage maturation and induces release of TNF-z
  • Sulfatides (surface glycolipids) inhibit phagolysosomal fusion


Mycobacterium leprae

  • acid fast bacillus
  • infects skin and superficial nerves ( glove and stocking loss of sensation)
  • reservoir in US: armadillos


  • diffusely over skin with leonine facies
  • communicable
  • low cell mediated immunity with humoral Th2 response
  • Tx: Dapsone + rifampin+ clofazimine for 2-5 years


  • limited to few hypoesthetic hairless skin plaques
  • high cell mediated immunity with a TH1 type immune response
  • Tx: dapson + rifampin for 6 mo





  • Gram negative
  • diplococci
  • ferment glucose and produce IgA proteases
  • N. gonorrhoaea is often intracellular




  • gram negative, diplococci
  • no polysaccharide capsule
  • no maltose fermentaiton
  • no vaccine
  • sexually transmitted
  • causes
    • gonorrhea
    • septic arthritis
    • neonatal conjunctivitis
    • pelvic inflammatory disease (PID)
    • Fitz-Hugh-Curtis syndrome
  • Condoms prevent sexual transmission
  • Erythromycin ointment prevents neonatal transmission
  • Tx: ceftriaxone ( azithromycin or doxycycline) for possible chlamdia co-infection




  • Gram negative, diplococci
  • Polysaccharide capsule
  • maltose fermentation
  • vaccine
  • respiratory and oral secretion transmission
  • causes
    • meningococcemia
    • meningitis
    • Waterhouse-Friderichsen syndrome
  • Prophylaxis: Rifampin, ciprofloxicin, ceftriaxone
  • Tx: Ceftriaxone or penicillin G


Haemophilus influenzae

  • gram negative rod (coccobacillus)
  • aerosol transmission
  • produces IgA protease
  • Culture on chocolate agar requires factors V (NAD+) and X (hematin) for growth
  • causes
    • epiglottitis
    • meningitis
    • otitis media
    • pneumonia
  • Tx: 
    • mucosal infections: amoxicillin +/- clavulanate
    • meningitis: cetriaxone
  • Prophylaxis: Rifampin
  • Vaccine: type B capsule polysaccharide conjugated to diptheria toxoid (given between 2-18 mo)


Legionella pneumophilia

  • gram negative rod
  • silver stain
  • grows on charcoal yeast extract culture with iron and cysteine
  • detected by presence of antigen in urine
  • aerosol tranmission from environmental water sources habitat ( air conditioning, hot water tanks)
  • No person to person transmission
  • Tx: macrolide or quinolone

Legionnaire's disease

  • severe pneumonia, fever, GI and CNS symptoms

Pontiac Fever

  • mild flu like symptoms


Pseudomonas aeruginosa

  • Aerobic gram negative rod
  • non-lactose fermenting, oxidase positive
  • produces pyocyanin (blue-green pigment)
  • grape-like odor
  • water source
  • produces endotoxin ( fever, shock) and exotoxin A ( inactivates EF-2)
  • associated with 
    • wound and burn infections
    • Pneumonia (CF)
    • Sepsis
    • External otitis (Swimmer's ear)
    • UTI
    • Drug use
    • Diabetic osteomyelitis
    • hot tub folliculitis

Ecthyma gangrenosum

  • rapidly progressive necrotic cutaneous lesions caused by pseudomonas bacteremia
  • typically seen in immunocompromised pts

Tx: aminoglycoside + extended spectrum penicillin (piperacillin, cefepime, imipenem, meropenem)



E. Coli

Gram negative, Rod, Lactose fermenter (fast)

  • Virulence factors
    • fimbriae: Cystitis and pyelonephritis
    • K capsule: pneuonia, neonatal meningitis
    • LPS endotoxin: septic shock


E. coli:


Microbe invades intestinal mucosa and causes necrosis and inflammation

  • invasive
  • dysentery


E. coli:


produces heat labile and heat stable enterotoxins

  • no inflammation or invasion
  • Traveler's diarrhea (watery)


E. coli:


  • No toxin produced
  • adheres to apical surface, flattens villi
  • prevents absorption
  • diarrhea in children (pediatrics)


E. coli:


  • 0157:H7
  • dysentery
  • Does not ferment sorbitol
  • produces shiga like toxin that causes hemolytic-uremic syndrome ( anemia, thrombocytopenia, acute renal failure)
  • microthrombi form on endothelium damaged by toxin--> mechanical hemolysis (schistocytes formed)--> decreased renal blood flow
  • microthrombi consume platelets leading to thrombocytopenia



  • Gram negative, rods, lactose fermenter (fast)
  • intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated
  • very mucoid colonies caused by abundant polsaccharide capsules
  • red "current jelly" sputum
  • also a cause of nosocomial UTIs
  • 4 As
    • aspiration pneumonia
    • abscesses in lung and liver
    • Alcoholics
    • diAbetics



  • Gram negative, rod, lactose non-fermenter, oxidase negative
  • Have flagella ( salmon swim)
  • disseminated hematogenously
  • have many animal reservoirs
  • produce hydrogen sulfide
  • antibiotics may prolong fecal excretion of organisms
  • invades intestinal mucosa and causes a monocytic response
  • cause bloody diarrhea
  • does not ferment lactose

Salmonella typhi

  • causes typhoid fever
  • found only in humans
  • rose spots on the abdomen, fever, headache, diarrhea
  • can remain in gallbadder and cause a carrier state



  • Gram negative, Rods, lactose non-fermenter, oxidase negative
  • no flagella
  • cell to cell transmission ( no hematogenous spread)
  • humans and primates are only reservoirs
  • does not produce hydrogen sulfide
  • antibiotics shorten duration of fecal excretion of organisms
  • invades intestinal mucosa and causes PMN infiltration
  • often causes bloody diarrhea
  • does not ferment lactose


Campylobacter jejuni

  • Gram negative, oxidase positive, comma shaped, grows at 42C
  • major cause of bloody diarrhea ( esp children)
  • Fecal-oral transmission through foods (poultry, meat, unpasturized milk
  • common antecedent to Cuillain-Barre syndrome and reactive arthritis



Vibrio cholerae

  • Gram negative, oxidase positive, comma shaped, grows in alkaline media
  • profuse rice-water diarrhea via enterotoxin that permanently activates Gs ( incr. cAMP)
  • Endemic to developing countries
  • prompt oral rehydration is necessary


Yersinia enterocolitica

  • usually transmitted from pet feces (puppies), contaminated milk or pork
  • causes mesenteric adenitis that can mimic Crohns disease or appendicitis


Helicobacter pylori

  • Gram negative, oxidase positive, comma shaped
  • produces urease
  • causes gastritis and peptic ulcer disease (duodenal)
  • risk factor for peptic ulcer, gastic adenocarcinoma and lymphoma
  • catase, oxidiase and urease positive
  • urea breath test or fecal antigen test for diagnosis
  • Tx: triple therapy
    • proton pump inhibitor
    • clarithromycin
    • amoxicillin or metronidazole



spiral shaped bacteria with axia filaments

  • Borrelia ( big, visualized using aniline dye) in light microscopy
  • Leptospira
  • Treponema ( dark field microscopy)


Leptospira interrogans

  • spirochete
  • found in water contaminated with animal urine
  • causes leptospirosis (flu-like symptoms, jaundice, photophobia with conjunctival suffusion (erythema w/o exudate)
  • prevalent among surfers and in tropics

Weil disease

  • icterohemorrhagic leptospirosis
  • severe form of jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage, and anemia


Borrelia burgdorferi

  • Spirochetes
  • transmitted by tick Ixodes
  • natural reservoir in mouse
  • common in northeast US
  • Early Symptoms
    • erythema chronicum migrans
    • flu like symptoms
    • +/- facial nerve palsy
  • Later symptoms
    • monoarthritis (large joints)
    • migratory polyarthritis
    • cardiac (AV nodal black)
    • neurologic (encephalopathy, facial nerve palsy, polyneuropathy)
  • Tx: doxycycline, ceftriaxone


Treponema pallidum

  • Spirochete
  • Primary Syphilis:
    • localized disease presenting with painless chancre
    • serologic testing: VDRL/RPR (non-specific)
    • Confirm: FTA-ABS
  • Secondary Syphilis:
    • Disseminated disease with constitutional symptom, maculopapular rash (palms and soles), condylomata lata
    • confirm with dark field microscopy
    • Serologic testing: VDRL/RPR (non-specific), confirm diagnosis with specific test ( FTA-ABS)
    • systemic
    • Latent syphilis (+ serology w/o symptoms) follows
  • Tertiary Syphillis
    • Gummas ( chronic granulomas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis)
    • Argyll Robertson pupil
    • signs: broad based ataxia, + Romberg, Charcot joint, stroke without HTN
    • test spinal fluid with VDRL or RPR
  • Congenital syphilis
    • saber shins, saddle nose, CN VIII deafness, Hutchinson teeth, mulberry molars
    • Prevention: treat mother early in pregnancy



Zoonotic bacteria:


Ixodes ticks

(live on deer and mice)


Zoonotic bacteria:


Cat scratch disease, bacillary angiomatosis

Cat scratch


Zoonotic bacteria:

Borrelia Burgdorferi

Lyme Disease

Ixodes ticks

(live on deer and mice)


Zoonotic bacteria:

Borrelia recurrentis

Relapsing fever


recurrent due to variable surface antigens


Zoonotic bacteria:


Brucellosis/ undulant fever

Unpasteurized dairy


Zoonotic bacteria:


  • Bloody diarrhea
  • puppies, livestock ( fecal-oral) ingestion of undercook meat


Zoonotic bacteria:

Chlamydophila psittaci

  • Psittacosis
  • parrots, other birds


Zoonotic bacteria:

Coxiella burnetiii

  • Q fever
  • aerosols of cattle/sheep amniotic fluid


Zoonotic bacteria:

Ehrilichia chaffeensis


  • Lone star ticks


Zoonotic bacteria:

Francisella tularensis

  • Tularemia
  • Ticks, rabbits and deer fly


Zoonotic bacteria:


  • Leptospirosis
  • Animal urine


Zoonotic bacteria:

Mycobacterum leprae

  • Leprosy
  • Humans with lepromatous leprosy
  • armadillo


Zoonotic bacteria:

Pasteurella multocida

  • Cellulitis, osteomyelitis
  • animal bite, cats, dogs


Zoonotic bacteria:

Rickettsia prowazekii

  • Epidemic typhus
  • Louse


Zoonotic bacteria:

Rickettsia rickettsii

  • Rocky Mountain spotted fever
  • Dermacentor ticks


Zoonotic bacteria:

Rickettsia typhi

  • Endemic typhus
  • Fleas


Zoonotic bacteria:

Yersnia pestis

  • Plague
  • Fleas (rats and prairie dog are reservoirs)


Gardnerella vaginalis

  • pleomorphic, gram-variable rod that is involved in vaginosis
  • presents as a gray vaginal discharge with a fishy smell
  • non-painful
  • associated with sexual activity, but not sexually transmitted
  • Bacterial vaginosis is also characterized by overgrowth of certain anaerobic bacteria in vagina
  • Clue cells: vaginal epithelial cells covered with Garnerella bacteria
  • Tx: metronidazole or clindamycin


Rickettsia rickettsii

  • Rocky mountain spotted fever
  • vector is a tick
  • South Atlantic states (North Carolina)
  • Rash: starts at wrist and ankle and spreads to trunk, palms, soles
  • Obligate intracellular organisms that need coA and NAD+ because they can't synthesize ATP

Triad: headache, fever, rash (vasculitis)



Richettsii typhi

  • endemic (fleas): Typhus
  • rash starts centrally and spread out sparring palms and soles

* Rickettsii on the wRists, Typhus on the Trunk*



  • Erhlichia
  • vector is a tick
  • monocytes with morulae (berry like inclusions) in cytoplasm



  • Anaplasma
  • vector is a tick
  • Granulocytes with morulae in cytoplasm


Coxiella burnetii

Q fever

  • No arthropod vector
  • tick feces and cattle placenta release spores that are inhaled as aerosols
  • presents as pneumonia
  • no rash, no vector and causative organism can survive outside of its endospore form



  • can't make their own ATP
  • obligate intracellular organisms that cause mucosal infections
  • 2 forms
    • Elementary body (small dense)- infectious and enters cells via endocytosis
    • Reticulate body replicates in cell by fission
  • Chlamydia trachomatis
    • reactive arthritis: Reiter syndrome
    • follicular conjunctivitis
    • nongonococcal urethritis
    • PID
  • C. pneumoniae and C. psittaci: atypical pneumonia (transmitted by aerosol)
  • Lab diagnosis: cytoplasmic inclusions seen on Giemsa or fluorescent antibody smear
  • Tx: azithromycin or doxycycline


Chlamydia Trachomatis

  • Types A, B, C
    • Chronic infection
    • cause blindness due to follicular conjunctivitis in Africa
  • Types D-K
    • Urethritis/PID
    • ectopic pregnancy
    • neonatal pneumonia (staccato cough)
    • neonatal conjunctivitis
  • Types L1, L2, L3
    • Lymphogranuloma venereum
    • small, painless ulcers on genitals --> swollen, painful inguinal lymph node that ulcerate (buboes)
    • Tx: doxycycline


Mycoplasma pneumoniae

Classica cause of atypical "walking" pneumonia

  • No cell wall, not seen on gram stain
  • bacterial membrane contains sterols for stability
  • frequent outbreaks in military recruits and prisons
  • insidious onset, headache, nonproductive cough, patchy or diffuse interstital infiltrate
  • High titer of cold agglutinins (igM) which can agglutinate or lyse RBCs
  • Grown on Eaton agar
  • Tx: macrolide, doxycyline or fluoroquinolone (penicillin inffective)