Microbiology: Gram Negative Bacteria

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jknell
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Microbiology: Gram Negative Bacteria
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2013-04-05 12:13:00
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  1. Gram Negative Algorithm
  2. Lactose-Fermenting Enteric Bacteria
    • Grow pink colonies on MacConkey's agar
    • EMB Agar: grow purple/black colonies
    • E coli: Green sheen

    • "CEEK(S)" (in ceek shyps)
    • Citrobacter
    • E Coli
    • Enterobacter
    • Klebsiella
    • Serratia

    E Coli produces β-galactosidase (breaks lactose into glucose and galactose)
  3. PCN and Gram Negative Bugs
    -GNRs are resistant to penicillin G but my be susceptible to PCN derivatives such as ampicillin and amoxicillin

    -GN outer membrane layer inhibits entry of penicillin G and vancomycin
  4. Neisseria
    • Gram (-) diplococci
    • -ferment glucose
    • -produce IgA proteases

    • "MeninGococci ferment Maltose and Glucose
    • Gonococci ferment Glucose"

    • Types:
    • 1. Neisseria gonorrhea
    • 2. Neisseria meningitiditis

  5. Neisseria gonorrhea
    • -no polysaccharide capsule
    • -no maltose fermentation
    • -no vaccine (rapid Ag variation of pilus prots)
    • -sexually transmitted

    • Causes:
    • -gonorrhea
    • -septic arthritis
    • -neonatal conjunctivitis
    • -PID
    • -Fitz-Hugh-Curtis Syndrome (liver capsule inflammation, complication of PID)

    • Treatment:
    • -ceftriaxzone
    • -tx chlamydia coinfection (azithromycin, doxcycycline)
  6. Neisseria Meningiditis
    • -polysaccharide capsule
    • -maltose fermentation
    • -vaccine (none for type B)
    • -transmission: respiratory and oral secretions

    • Causes:
    • -meningococcemia
    • -meningitis
    • -Waterhouse-Friderichsen syndrome (hemorrhage into adrenal glands)

    • Treatment:
    • -ceftriazone or PCN G
    • -prophylax close contacts with rifampin, ciprofloxacin or ceftriaxone
  7. Haemophilus influenzae
    • -small Gram (-) coccobacillary rod
    • -produces IgA protease
    • -culture on chocolate agar, needs factor V (NAD+) and X (hematin) for growth
    • *can also be cultured with S. aureus which produces Factor V

    • Type B (HiB):
    • -capsule
    • -causes most invasive disease

    • Nontypeable strains:
    • -mucosal infections (otitis media, conjunctivitis, bronchitis)

    Transmission: aerosol

    • Causes:
    • -Epiglottitis (Cherry red in children)
    • -Meningitis
    • -Otitis Media
    • -Pneumonia

    Does NOT cause "flu"

    • Treatment:
    • -meningitis with ceftriaxone
    • -prophylax close contacts with rifampin

    • Vaccine:
    • -type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxin
    • -2-18 months old
  8. Legionella pneumophila
    • Gram (-) rod
    • -gram stains poorly --> use silver stain

    • Culture:
    • -charcoal yeast extract with iron and cysteine

    • Diagnosis:
    • -antigen in urine

    • Transmission:
    • -aerosol from environmental water source habitat
    • -no person-to-person transmission!

    • Causes:
    • 1. Legionnaire's disease
    • -severe pneumonia
    • -fever
    • -GI and CNS sx
    • 2. Pontiac Fever
    • -mild flu-like syndrome

    • Treatment:
    • -macrolide or quinolone

    "French legionnaire with his silver helmet, sitting around a campfire (charcoal) with his iron dagger - he is no sissy (cysteine)"
  9. Pseudomonas aeruginosa
    • Gram (-) rod
    • -aerobic "Aeruginosa -- aerobic"
    • -non-lactose fermenting
    • -oxidase positive

    • -produces procyanin (blue-green pigment)
    • -grape-like odor
    • -endotoxin (fever, shock)
    • -exotoxin A (inactivates EF-2)

    • Transmission:
    • -water source

    *associated with wound and burn infections

    • Causes: "PSEUDOmonas"
    • Pneumonia (esp in CF)
    • Sepsis (black lesions on skin)
    • External otitis
    • UTI
    • Drug use and Diabetic Osteomyelitis

    • Treatment:
    • -aminoglycoside + extended spectrum penicillin (piperacillin, ticarcillin)
  10. E coli
    • Virulence Factors:
    • -fimbriae: cystitis, pyelonephritis
    • -K capsule: pneumonia, neonatal meningitis
    • -LPS endotoxin: septic shock

    • Strains:
    • -EIEC (invasive)
    • -ETEC
    • -EPEC
    • -EHEC
  11. EIEC
    Invasive; dysentery

    • Mechanism:
    • -microbes invade intestinal mucosa and cause necrosis and inflammation
    • -no toxins produces
    • -clinical manifestations similar to Shigella
  12. ETEC
    Traveler's diarrhea, watery

    • Labile toxin
    • Stabile toxin

    No inflammation or invasion
  13. EPEC
    Diarrhea usually in children (Pediatrics)

    No toxin produced

    Adheres to apical surface, flattens villi, prevents absorption
  14. EHEC
    • Dysentery (toxin alone causes necrosis and inflammation)
    • *does not ferment sorbitol (vs other E. coli)

    • O157:H7
    • -most common serotype
    • -produces shiga-like toxin
    • -HUS (anemia, thrombocytopenia, acute renal failure)

    Endothelium swells and narrows lumen leading to mechanical hemolysis and reduced renal blood flow. Damaged endothelium consumes platelets
  15. Klebsiella
    -intestinal flora

    -causes lobar pneumonia in alcoholics and diabetics when aspirated

    -very mucoid colonies (caused by abundant polysaccharide capsule)

    -red "current jelly" sputum

    -also causes nosocomial UTIs

    • "4 A's"
    • Aspiration pneumonia
    • Abscesses in lungs and liver
    • Alcoholics
    • diAbetics
  16. Salmonella
    • -have flagella ("salmon swim")
    • -hematogenous dissemination
    • -many animal reservoirs
    • -produce H2S
    • -invades intestinal mucosa and causes a monocytic response
    • -can cause bloody diarrhea
    • -non-lactose fermenter

    -Tx with Abx may prolong sx

    • Salmonella typhi
    • -causes typhoid fever
    • -found only in humans
    • -rose spots on the abdomen, fever, HA, diarrhea
    • -can remain in gallbladder and cause carrier state
  17. Shigella
    • -no flagella
    • -transmission: cell to cell, NO hematogenous spread
    • -only reserviors are humans and primates
    • -doesn't produce H2S
    • -invades intestinal mucosa and causes PMN infiltration
    • -often causes bloody diarrhea
    • -non-lactose fermenter

    Tx with Abx prolong excretion of organism in feces
  18. Campylobacter jejuni
    • -comma or S-shaped
    • -oxidase positive
    • -grows at 42C (Campylobacter likes the hot campfire)

    • Causes:
    • -major cause of bloody diarrhea (esp in children)

    • Transmission:
    • -F/O through foods (poultry, meat, unpasteurized milk)

    **common antecedent to Guillain Barre and reactive arthritis
  19. Vibrio cholerae
    • -Comma shaped
    • -oxidase positive
    • -grows in alkaline media

    -endemic to developing countries

    • Causes:
    • -diffuse rice water diarrhea

    -cholera toxin that permanently activates Gs (increased cAMP)

    • Treatment:
    • -prompt oral rehydration
  20. Yersinia enterocolitica
    • Transmission:
    • -pet feces
    • -contaminated milk
    • -pork

    • Causes:
    • -mesenteric adenitis that can mimic Crohn's or appendicitis
  21. Helicobacter pylori


    • Gram (-) rod
    • -curved
    • -urease positive (urease breath test)
    • -creates alkaline environment

    • Causes:
    • -gastritis
    • -up to 90% of duodenal ulcers

    Risk factor for peptic ulcer, gastric adenomcarcinoma and lymphoma

    • Treatment:
    • -triple therapy
    • -PPI
    • -Clarithromycin
    • -amoxicillin or metronidazole
  22. Spirochetes


    -spiral shaped bacteria with axial filaments

    • "BLT" B is Big
    • Borrellia
    • Leptospira
    • Treponema

    Only borrelia can be visualized using aniline dyes in light microscopy

    Treponema visualized by dark-field microscopy
  23. Leptospira interrogans
    -found in water contaminated with animal urine

    • Causes Leptospirosis:
    • -flu-like sx
    • -jaundice
    • -photophobia with conjunctivitis

    *surfers and in tropics (Hawaii)

    • Weil's Disease:
    • -icterohemorrhagic leptospirosis
    • -severe form with jaundice and azotemia (high levels of nitrogen compounds) from liver and kidney dysfunction
    • -fever
    • -hemorrhage
    • -anemia
  24. Lyme Disease
    • -caused by Borrelia burgdorferi
    • -common in NE US

    • Transmission:
    • -tick Ixodes (also a vector for babesia)
    • -natural reservoir is mouse (important in tick life cycle)

    • Stage 1:
    • -erythema chronicum migrans (target lesion)
    • -flu-like sx

    • Stage 2:
    • -neurologic (facial nerve palsy)
    • -cardiac (AV node block)

    • Stage 3:
    • -musculoskeletal (chronic monoarthritis and migratory polyarthritis)
    • -neurologic (encephalopathy and polyneuropathy)
    • -cutaneous

    • "FAKE an Key Lyme pie"
    • Facial nerve palsy (typically bilateral)
    • Arthritis
    • Kardiac block
    • Erythema migrans
  25. Syphilis
    Caused by Treponema pallidum

    • Primary Syphilis:
    • -localized disease
    • -painless chancre
    • -screen with VDRL and confirm diagnosis with FTA-ABS

    • Secondary Syphilis:
    • -disseminated disease
    • -constitutional sx
    • -maculopapular rash (palms and soles)
    • -condylomata lata
    • -Screen with VDRL, confirm diagnosis with FTA-ABS
    • -"Secondary syphilis = systemic"
    • Tertiary Syphilis:
    • -gummas (chronic granulomas)
    • -aortitis (vasa vasorum destruction)
    • -neurosyphilis (tabes dorsalis)
    • -argyll roberston pupil
    • -test spinal fluid with VDRL

    • Signs of Tertiary Syphilis:
    • -broad-based ataxia
    • -positive Romberg
    • -Charcot joint
    • -stroke w/o HTN

    • Congenital Syphilis:
    • -Saber shins
    • -saddle nose
    • -CNVIII deafness
    • -Hutchinson's teeth (smaller, more widely spaced)
    • -mulberry molars
    • *early prevention! placental transmission usually occurs after first trimester
  26. Argyll Robertson Pupil
    • -constricts with accommodation but is not reactive to light
    • -associated with tertiary syphilis

    "prostitute's pupil": accommodates but does not react
  27. VDRL false positives
    -detects nonspecific antibody that reacts to beef cardiolipin

    -used to dx syphilis

    • Many false positives:
    • -viral infection (mono, hepatitis)
    • -some drugs
    • -rheumatic fever
    • -SLE
    • -leprosy

    • "VDRL"
    • Viruses
    • Drugs
    • Rheumatic Fever
    • Lupus and Leprosy
  28. Jarisch-Herxheimer reaction
    • -Flu-like syndrome immediately after antibiotics are started
    • -due to killed bacteria releasing pyrogens
  29. Zoonotic Bacteria
    -infectious diseases transmitted between animals and humans

    • Bartonella
    • Borrelia burgdorferi
    • Borrelia recurrentis
    • Brucella
    • Campylobacter
    • Chlamydia psittaci
    • Coxiella burnetii
    • Ehrlichia chaffeensis
    • Francisella tularensis
    • Mycobacterium leprae
    • Pasteurella multocida
    • Ricekttsia prowazekii
    • Rickettsia rickettsii
    • Rickettsia typhi
    • Yersinia pestis
  30. Bartonella
    • -zoonosis
    • -Cat scratch disease
  31. Borrelia burgdorferi
    -zoonosis

    Causes: lyme disease

    Transmission: Ixodes tick (live on deer and mice)
  32. Borrelia recurrentis
    -zoonosis

    Causes: recurrent fever

    Transmission: louse (recurrent b/c of variable surface antigens)
  33. Brucella
    -zoonosis

    Causes: Brucellosis/undulant fever

    Transmission: unpasteurized dairy
  34. Campylobacter
    -zoonosis

    Causes: bloody diarrhea

    Transmission: puppies, livestock (F/O, ingestion of undercooked meat)
  35. Chlamydophila psittaci
    -zoonosis

    Causes: Psittacosis (Parrot disease)

    Transmission: Parrots, other birds
  36. Coxiella burnetii
    -zoonosis

    • Q fever
    • -no arthropod vector
    • -presents as pneumonia
    • "Q fever is Queer because it has no rash or vector and its causative organism can survive outside in its endospore form"

    Transmission: aerosols of cattle/sheep amniotic fever
  37. Ehrlichia chaffeensis
    -zoonosis

    • Ehrliciosis
    • -monocytes with morula (berry-like inclusions)

    Transmission: Lone star tick
  38. Francisella tularensis
    -zoonosis

    Causes: Tularemia

    Transmission: Rabbits, ticks, deer fly
  39. Leptospira
    -zoonosis

    Causes: Leptospirosis

    Transmission: animal urine
  40. Mycobacterium leprae
    -zoonosis

    Causes: leprosy

    Transmission: armadillos, humans
  41. Pasteurella multocida
    -zoonosis

    Causes: cellulitis, osteomyelitis

    Transmission: animal bite, cats, dogs
  42. Ricekttsia prowazekii
    -zoonosis

    • Epidemic typhus
    • -rash starts centrally and spreads out, sparing palms and soles

    "Rickettsii on the wRists, Typhus on the Trunk"

    Transmission: louse
  43. Rickettsia rickettsii
    • -zoonosis
    • -broadly distributed in US
    • -obligate intracellular organism (need CoA and NAD+)

    • Rocky Mountain Spotty Fever
    • -rash typically starts at wrists and ankles then spreads to trunk, palms and soles
    • -Classic triad (HA, fever, rash (vasculitis))

    "Rickettsii on the wRists, Typhus on the Trunk"

    Transmission: Dermacentor tick bite
  44. Rickettsia typhi
    -zoonosis

    Causes: endemic typhus

    Transmission: fleas
  45. Yersinia pestis
    -zoonosis

    Causes: Plague

    Transmission: flea (rats and prairie dogs are reservoirs)
  46. Gardnerella vaginalis
    • Gram variable rod
    • -pleomorphic

    • Causes:
    • -vaginosis
    • -gray vaginal discharge, fishy smell
    • -non-painful

    Associated with sexual activity (not an STD)

    • Bacterial Vaginosis:
    • -overgrowth of certain bacteria in vagina
    • -clue cells (vaginal epithelial cells covered in bacteria)

    Treatment: metronidazole

    "I don't have a clue why I smell fish in the vagina garden"
  47. Rickettsial diseases with rash
    • Rocky Mountain Spotted Fever
    • Typhus (endemic, epidemic)
  48. Rickettsial diseases without rash
    • Ehrlichiosis
    • Anaplasmosis
    • Q fever
  49. Palm and Sole Rash
    "you drive CARS using your palms and soles"

    • Coxsackievirus A (hand, foot and mouth disease)
    • Rocky Mountain Spotted Fever
    • Secondary Syphilis
  50. Chlamydiae
    • Intracellular: can't make ATP
    • Chlamys = cloak (intracellular)

    -cell wall lacks muramic acid

    Cause mucosal infections

    • Two forms:
    • 1. Elementary body
    • -small, dense
    • -"is Enfectious and Enters cell via Endocytosis"'

    • 2. Reticulate body
    • -Replicates in cell by fission
    • -form seen on tissue culture

    • Chlamydia trachomatis:
    • -reactive arthritis
    • -conjunctivitis
    • -nongonococcal urethritis
    • -PID

    • C. pneumoniae and C. psittaci:
    • -atypical pneumonia
    • -transmitted by aerosol

    • Diagnosis:
    • -cytplasmic inclusions on Giemsa or fluorescent antibody-stained smear

    • Treatment:
    • -azithromycin (one time tx)
    • -OR doxycyclin
  51. Chlamydia trachomatis serotypes
    • A,B and C:
    • -chronic infection
    • -cause blindness due to follicular conjuntivitis in Africa
    • -"ABC = Africa/Blindness/Chronic infection"

    • D-K:
    • -urethritis/PID
    • -ectopic pregnancy
    • -neonatal pneumonia (staccato cough)
    • -neonatal conjunctivitis

    • L1, L2 and L3:
    • -lymphogranuloma venereum
  52. Mycoplasma pneumoniae
    • -no cell wall (not seen on Gram stain)
    • -membrane contains sterols for stability
    • -grown on Eaton's agar

    • Causes:
    • -atypical "walking" pneumonia (pts <30, military recruits, prisons)
    • -insidious onset
    • -HA
    • -nonproductive cough
    • -diffuse interstitial infiltrate
    • *Xray looks worse than patient

    • High titer of cold agglutinins (IgM)
    • -can agglutinate or lyse RBCs

    • Treatment:
    • -macrolide
    • -OR fluoroquinolone

    *PCN ineffective since mycoplasma lack cell wall

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