Gram Negative and Other Bacteria Flashcards
Neisseria gonorrhoeae
gram-negative diplococci, ferment glucose, no capsule
produce IgA protease
within polymorphonuclear lwukocytes
sexually transmitted
gonorrhea, septic arthritis, neonatal conjuctivitis, PID
Fitz-Hugh-Curtis syndrome
treatment: ceftriaxone (+ azithromycin or doxyxyline for possible chlamydia coinfection)
Neisseria meningitidis
gram negative diplococci, ferment glucose and maltose, capsule
vaccine (none for type B)
transmitted through respiratory and oral secretions
meningococcemia and meningitis, Waterhouse-Friderichsen syndrome
treatment: ceftriaxone or penicillin G
rifampin, ciproflaxacin or ceftriaxone prohylaxis in close contacts
Haemophilus influenzae
small gram-negative coccoid rods
aerosol transmission; produces IgA protease
cause Epiglottitis (“cherry red” in children), Meningitis, Otitis media, Pneumonia (EMOP)
non-typeable strains - mucosal infections (otitis media, conjunctivitis, bronchitis)
capsular (polyribosylribitol phosphate) type B - invasive disease (meningitis, pneumonia)
culture on chocolate agar with factor V (NAD+, produced by S. aureus) and factor X (hematin)
treatment: meningitis with ceftriaxone; rifampin for prophylaxis in close contacts
vaccine - contains type B capsular polysaccharide conjugated to diphtheria toxoid - given at 2-18 months of age (prevent meningitis)
Legionella pneumophila
gram-negative rod - use silver stain
grow on charcoal yeast extract with iron and cysteine
aerosol transmission from environmental water source habitat; no person-to-person transmission
detected by presence of antigen in urine; labs show hyponatremia
Legionnaires’ disease - severe pneumonia, fever, GI and CNS syndrome
Pontiac fever - mild flu-like syndrome
Pseudomonas aeruginosa
gram-negative aerobic rods
non-lactose fermenting, oxidase positive, blue-green pigment, grape-like odor
water source, burn infections
PSEUDO
Pneumonia - in CF with biofilm if chronic
Sepsis - black lesions on skin
External otitis - swimmer’s ear, malignant in diabetics
UTI
Drug use and Diabetic Osteomyelitis
hot tub folliculitis
produces endotoxin (fever, shock) and exotoxin A (inactivates EF-2)
treatment: aminoglycoside + extended-spectrum penicllin (piperacillin, ticarcillin)
E. coli virulence factors
fimbriae - cystitis and pylonephritis
K capsuel - pneumonia, neonatal meniningitis
LPS endotoxin - septic shock
Klebsiella
gram-negative rod, fast lactose fermenter
intestinal flora
causes lobar pneumonia in alcoholics and diabetics when aspirated; nosocomial UTIs
mucoid colonies caused by abundant polysaccharide capsule
red “currant jelly” sputum
Salmonella
gram negative rod, lactose nonfermenter, oxidase negative
have flagella, can disseminate hematogenously
many animal reservoirs
produces hydrogen sulfide
invades intestinal mucosa and causes a monocytic response –> can cause bloody diarrhea
Typhi - typhoid fever, only in humans - rose spots on the abdomen, fever, headache, and diarrhea - can remain in gallbladder and cause a carrier state
Shigella
gram negative rod, lactose nonfermenter, oxidase negative
no flagella; cell to cell transmission, no hematogenous spread
only reservoirs are humans and primates
invades intestinal mucosa and causes PMN infiltration –> often causes bloody diarrhea
Campylobacter jejuni
gram-negative comma shaped
grows in 42 C, oxidase positive
causes bloody diarrhea, especially in children
fecal-oral transmission through food (poultry, raw meat, unpasteurized milk); puppy feces
common antecedent to Guillain-Barre syndrome and reactive arthritis
Vibrio cholerae
gram-negative comma shape
grows in alkaline media, oxidase positive
produces profuse rice-water diarrhea via toxin that permanently activates Gs, increase cAMP
endemic to developing countries
prompt oral rehydration is necessary
Yersinia enterocolitica
gram-negative
causes mesenteric adenitis that can mimic Crohn’s or appendicitis
transmitted from pet feces, contaminated milk or pork
Helicobacter pylori
gram-negative curved rod, urease positive, oxidase positive
causes gastritis and up to 90% of duodenal ulcers
treatment: PPI, clarithromycin, amoxicillin or metronidazole
Leptospira interrogans
spirochete
found in water contaminated with animal urine
causes leptospirosis: flu-like symptoms, jaundice, photophobia with conjuctivitis
prevalent among surfers and in the tropics (Hawaii)
Weil’s disease: severe form with jaundice and azotemia from liver and kidney dysfunction; fever, hemorrhage, anemia
Borrelia burgdorferi
spirochete - only visualized using aniline dyes (Wright’s or Giemsa)
transmitted by Ixodes tick; natural reservoir is mouse (important to tick life cycle)
common in NE US
3 stages:
1) erythema chronicum migrans, flu-like symptoms
2) neurologic (facial nerve palsy), cardiac (AV nodal block)
3) musculoskeletal (chronic monoarthritis and migratory polyarthritis), neurological (encephalopathy and polyneuropathy), cutaneous manifestations
Treponema pallidum
sphirochete - dark-field microscopy
primary: localized disease - painless chancre (screen w/ VDRL and confirm w/ FTA-ABS)
secondary: disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata (screen w/ VDRL and confirm w/ FTA-ABS)
tertiary: gummas (chronic granulomas) aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis), Argyll Robertson pupil (test spinal fluid w/ VDRL)
congenital: saber shins, saddle nose, CN VIII deafness, Hutchinson’s teeth, mulberry molars (transmission occurs in 1st trimester)
treatment: penicillin G
False positive VDRL: viral infection (mono, hepatitis), some drugs, rheumatic fever, SLE, leprosy
Gardnerella vaginalis
pleomorphic, gram-variable rod
gray vaginal discharge with a fishy smell; nonpainful
associated with sexual activity, but not an STD
clue cells or vaginal epithelial cells covered with bacteria
treatment: metronidazole
Rickettsia rickettsii
obligate intracellular organisms that need CoA and NAD+
Rocky Mountain spotted fever (tick) - broadly distributed in US
rash startes at wrists and ankles and then spreads to trunk, palms, and soles
Other rash - Typhus:
endemic (fleas) - R. thyphi
epidemic (human body louse) - R. prowazekii (rash starts centrally and spreads out, sparing palms and soles)
No rash:
ehrlichiosis (tick) - ehrlichia - monocytes with morula (berry-like inclusions) in cytoplasm
anaplasmosis (Ixodes tick) - anaplasma - granulocytes with morula in cytoplasm
Chlamydia trachomatis
obligate intracellular organism that cause mucosal infections
elementary and reticulate bodies
reactive arthritis, conjunctivitis, nongonococcal urethritis, PID
A, B, C - chronic infection, blindness due to follicular conjunctivitis in Africa
D-K - urethritis/PID, ectopic pregnancy, neonatal pneumonia, or neonatal conjuncivitis
L1, L2, L3 - lymphogranuloma venereum
diagnosis: cytoplasmic insulsions seen on Giemsa or fluorescent antibody-stained smear (wall lacks muramic acid)
treatment: azithromycin (one-time treatment) or doxycycline
Mycoplasma pneumoniae
no cell wall –> no gram stain (membrane contains sterols)
grown on Eaton’s agar
causes atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, diffuse interstitial infiltrate)
frequent outbreaks in military recuits and prisons (patients < 30)
high titer of cold agglutinins (IgM), which can lyse RBC
treatment: macrolide or fluoroquinolone
