Microbiology: Gram Negative 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)

-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

• Gram (-) diplococci
• -ferment glucose
• -produce IgA proteases

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

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

• -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)

• -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

• -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

• 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)"

• 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)

• Virulence Factors:
• -fimbriae: cystitis, pyelonephritis
• -K capsule: pneumonia, neonatal meningitis
• -LPS endotoxin: septic shock

• Strains:
• -EIEC (invasive)
• -ETEC
• -EPEC
• -EHEC

Invasive; dysentery

• Mechanism:
• -microbes invade intestinal mucosa and cause necrosis and inflammation
• -no toxins produces
• -clinical manifestations similar to Shigella

Traveler's diarrhea, watery

• Labile toxin
• Stabile toxin

No inflammation or invasion

Diarrhea usually in children (Pediatrics)

No toxin produced

Adheres to apical surface, flattens villi, prevents absorption

• 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

-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

• -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

• -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

• 
• -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

• -Comma shaped
• -oxidase positive
• -grows in alkaline media

-endemic to developing countries

• Causes:
• -diffuse rice water diarrhea

-cholera toxin that permanently activates G_s (increased cAMP)

• Treatment:
• -prompt oral rehydration

• Transmission:
• -pet feces
• -contaminated milk
• -pork

• Causes:
• -mesenteric adenitis that can mimic Crohn's or appendicitis

• 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

-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

-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

• -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

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

• -constricts with accommodation but is not reactive to light
• -associated with tertiary syphilis

"prostitute's pupil": accommodates but does not react

-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

• -Flu-like syndrome immediately after antibiotics are started
• -due to killed bacteria releasing pyrogens

-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

• -zoonosis
• -Cat scratch disease

-zoonosis

Causes: lyme disease

Transmission: Ixodes tick (live on deer and mice)

-zoonosis

Causes: recurrent fever

Transmission: louse (recurrent b/c of variable surface antigens)

-zoonosis

Causes: Brucellosis/undulant fever

Transmission: unpasteurized dairy

-zoonosis

Causes: bloody diarrhea

Transmission: puppies, livestock (F/O, ingestion of undercooked meat)

-zoonosis

Causes: Psittacosis (Parrot disease)

Transmission: Parrots, other birds

-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

-zoonosis

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

Transmission: Lone star tick

-zoonosis

Causes: Tularemia

Transmission: Rabbits, ticks, deer fly

-zoonosis

Causes: Leptospirosis

Transmission: animal urine

-zoonosis

Causes: leprosy

Transmission: armadillos, humans

-zoonosis

Causes: cellulitis, osteomyelitis

Transmission: animal bite, cats, dogs

-zoonosis

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

"Rickettsii on the wRists, Typhus on the Trunk"

Transmission: louse

• -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

-zoonosis

Causes: endemic typhus

Transmission: fleas

-zoonosis

Causes: Plague

Transmission: flea (rats and prairie dogs are reservoirs)

• 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"

• Rocky Mountain Spotted Fever
• Typhus (endemic, epidemic)

• Ehrlichiosis
• Anaplasmosis
• Q fever

"you drive CARS using your palms and soles"

• Coxsackievirus A (hand, foot and mouth disease)
• Rocky Mountain Spotted Fever
• Secondary Syphilis

• 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

• 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

• 
• -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