USMLE - Micro Bacteria

Cocci --> Catalase test

Catalase -: Streptococcus

Catalase +: Staph

Staph --> Coagulase test

Coagulase +: S aureus

Coagulase -: Do Novobiocin test

"NO StRESs at the staph retreat"

Novobiocin sensitive: S epidermidis

Novobiocin resistant: S saprophyticus

Clostridium (anaerobe)

Corynebacterium

Listeria

Bacillus (aerobe)

Mycobacterium (acid fast)

Anaerobe, not acid fast: Actinomyces
Aerobe, acid fast: Nocardia

Hemolysis test
Partial hemolysis –> green on blood agar–> α
Complete hemolysis –> clear on blood agar –> β
No hemolysis on blood agar –> γ

“OVRPS”
Capsule, +Quellung, Optochin sensitive –> Strep pneumoniae
No capsule, Optochin resistant –> Viridans streptococci (S mutans)

“B-BRAS”
Group A: Bacitracin sensitive –> S pyogenes
Group B: Bacitracin resistent –> S agalactiae

Group D (Enterococcus): Growth in bile and 6.5% NaCl (E faecalis)

Nonenterococcus: Growth in bile, not 6.5% NaCl (S bovis)

Staphlococcus aureus (catalase+, coagulase+)

Streptococcus pyogenes (GAS: Catalase-, Bacitracin sensitive)

Streptococcus agalactiae (GBS: Catalase-, Bacitracin resistent)

Listeria Monocytogenes (tumbling motility, meningitis in newborns, unpasteurized milk)

Gram+ Cocci in Clusters, Catalase+, Coagulase+
Protein A binds FcIgG and inhibits complement fixation and phagocytosis
TSST –> fever, vomiting, rash, desquamation, shock, end organ failure
Skin infection, Organ abscess (coagulase forms fibrin clot around self), Pneumonia, Endocarditis, Osteomyelitis, Food poisoning (preformed toxins), TSS, Scalded skin syndrome (exfoliative toxin)

Methicillin Resistent Staph Aureus
Resistent to β-lactams because of altered penicillin binding protein

Part of normal skin flora
Contaminates blood cultures
Infects prosthetic devices and IV catheters by producing adherent biofilms

Gram+, Lancet Shaped, Diplococci
Encapsulated, IgA protease
α hemolytic, Optochin sensitive
“MOPS are Most OPtochin Sensitive”
Meningitis, Otitis media (in children), Pneumonia, Sinusitis
Rusty sputum, sepsis in sickle cell anemia and splenectomy

α hemolytic, Optochin Resistent, Produces Dextran from Sucrose
Normal flora of oropharynx
Dental caries (S mutans) and Subacute bacterial endocarditis (S sanguis) - stick to prosthetic valve via glycocalyx
Adheres to Fibrin-Platelet Aggregates

Gram+ Cocci, β-Hemolytic, bacitracin sensitive
Pyogenic: pharyngitis, cellulitis, impetigo
Toxigenic: scarlet fever, TSLS, Necrotizing fasciitis
Immunologic: Rheumatic fever, acute glomerulonephritis
ASO titers
M protein enhances host defense but gives rise to rheumatic fever

GAS

"JONES"

Joints - polyaarthritis

Carditis

Nodules (subcutaneous)

Erythema marginatum

Sydenham's chorea

Scarlet rash sparing face, Strawberry (scarlet) tongue, Scarlet throat

Pharyngitis –> RF and Glomerulonephritis
Impetigo more commonly precedes glomerulonephritis than pharyngitis

“GBS: B is for babies”
Gram+ Cocci, β-Hemolytic, bacitracin resistent, Hippurate test +
Produces CAMP factor which enlarges area of hemolysis formed by S aureus
Vagina
Pneumonia, Meningitis, and Sepsis in babies
Screen pregnant women at 35-37 weeks
Pt’s with + cultures receive intrapartum penicillin prophylaxis

Enterococcus

Names

Markers

Where are they normally?

Resistant to?

What do they cause?

Bad version?

Difference in C carbohydrate in cell wall

GDS: S bovis
Gram+ cocci Non-hemolytic and growth in bile but not 6.5% NaCl
Colonizes the gut
Bacteremia and subacute endocarditis in colon cancer patients

S bovis, E. faecalis, E. faecium

Gram+ rods with metachromatic (blue and red) granules
Black colonies on Cystine-Tellurite agar
Elek’s test for toxins
+ Aniline dyes
Diphtheria via exotoxin encoded by β prophage. Inhibits protein synthesis by ADP-ribosylation of EF2
Pseudomembranous pharyngitis (gray-white membrane), lymphadenopathy, myocarditis, arrhythmias
Toxoid vaccine prevents diphtheria

Dipicolinic acid in the core
Autoclave @ 121 degrees C for 15 minutes

Gram+ rods that are obligate anaerobes. Spore forming

| Tetani, Botulinum, Perfringens, Difficile

Gram+ rods that are obligate anaerobes. Spore forming
Tetanospasmin is an exotoxin. Cleaves SNARE protein required for NT release of GABA and Gly neurons (Renshaw cells in spinal cord)
Muscle rigidity, lock jaw, Risus sardonicus

Gram+ rods that are obligate anaerobes. Spore forming
Botulinum toxin
Cleaves SNARE protein required for NT release of ACh from neurons
Baby who ate honey has Flaccid paralysis (floppy baby)

Gram+ rods that are obligate anaerobes. Spore forming
Alpha toxin (lecithinase)
Phospholipase that degrades tissues and cell membranes
Degradation of phospholipid C --> myonecrosis (gas gangrene) and hemolysis (double zone of hemolysis on blood agar)
Gas Gangrenous Leg

Gram+ rods that are obligate anaerobes. Spore forming
Toxin A (enterotoxin) binds brush border of gut
Toxin B (cytotoxin) destroys cytoskeletal structure of enterocytes causing pseudomembranous colitis
Diarrhea after antibiotic use (clindamycin or ampicillin)
Detection of toxin in stool
Metronidazole or oral vancomycin

Gram+ spore forming rod
Only bacteria with polypeptide capsule (with D-glutamate)
Antrax toxin
Cutaneous vs Pulmonary

Contact --> black eschar (painless ulcer); can progress to bacteremia and death
Black skin lesion - black eschar (necrosis) surrounded by edematous ring
Caused by Lethal factor and Edema factor (Mimics AC and increases cAMP)

Inhalation of spores --> flu-like symptoms that rapidly progresses to fever, pulmonary hemorrhage, mediastinitis, and shock

Inhalation of Anthrax spores from contaminated wool

Gram+ aerobic rods
Food poisoning. Spores survive cooking rice and keeping it warm results in germination of spores and enterotoxin formation
Emetic type: Rice and pasta. Nausea and vomiting for 1-5 hours caused by cereulide (a preformed toxin)
Diarrheal type causes watery non-bloody diarrhea and GI pain for 8-18 hours

Gram+ rods
Facultative intracellular microbe
Ingestion of unpasteurized milk/cheese or deli meats. Vaginal transmission during birth
Forms actin rockets to move from cell to cell with characteristic tumbling motility

Amnionitis, Septicemia, and Spontaneous abortion in pregnant women
Granulomatosis infantiseptica, Neonatal meningitis
Meningitis in immunocompromised pts
Mild gastroenteritis in health individuals
Gastroenteritis is self limiting
Ampicillin for infants, immunocompromised and elderly

Gram+ branching filaments

Anaerobic

Not Acid Fast

Normal oral flora

Oral/facial abscesses that drain through sinus tracts forming yellow sulfur granules

Penicillin

Gram+ branching filaments
Aerobe
Acid Fast
Soil
Pulmonary infections in immunocompromised
Cutaneous infections after trauma in normals
Sulfonamides

+: Current infection, Past exposure, BCG vaccinated

| -: No infection, anergic (steroids, malnutrition, immunocompromised), or Sarcoidosis

Acid Fast

Tuberculosis

Kansaii (pulmonary TB-like symptoms)

Avium-Intracellulare (disseminated nonTB disease in AIDS resistant to multiple drugs. Treat prophylactically with azithromycin)

Leprae

Fever, Night sweats, Wt loss, Hemoptysis
Cord Factor: inhibits macrophage maturation and induces release of TNFα
Sulfatides (surface glycolipids) inhibit phagosysosomal fusion
Caseating granuloma w/ multinuclear Langhan's giant cells

Non immune host (usually a child)
Hilar nodes + Ghon focus (usually in mid zone of lung) = Ghon Complex
Heals by fibrosis --> immunity and hypersensitivity --> Tuberculin+
Progressive disease
Bacteremia --> miliary TB
Preallergic lymphatic or hematogenous dissemination --> dormancy in several organs --> reactivation in adult life

Partially immune hypersensitized host (adult)
Fibrocaseous cavitary lesion usually in upper lobes
Reactivation in the lungs
CNS (parenchymal tuberculoma or meningitis)
Vertebral body (Pott's Disease)
Lymphadenitis, Renal, GI

Likes cool temps: infects skin, superficial nerves (glove and stocking loss of sensation)

Cannot be grown in vitro

Armadillos

Lepromatuous vs Tuberculoid

Dapsone + Rifampin

Presents diffusely over skin

Communicable

Low cell-mediated immunity with a humoral Th2 response

Dapsone + Rifampin + Clofazimine for 2-5 years

Limited to a few hypoesthetic hairless skin plaques
High cell-mediated immunity with Th1 cell response
Dapsone + Rifampin for 6 months

Oxidase+, comma shaped: Campylobacter jejuni or Vibrio cholerae
Diplococci --> Maltose test
M+: Neisseria meningitidis. M-: N. gonorrhoeae
Coccoid rods --> Haemophilus influenzae, Pasturella, Brucella, Bordetella pertussis
Rods --> Lactose fermentation test
L+: Klebsiella, E coli, Enterobacter
L-: Oxidase test
O+: Pseudomonas, H pylori
O-: Shigella, Salmonella, Proteus

"test with MacConKEES agar"
Pink colonies on MacConkey's agar
Purple/black colonies on EMB
E coli grows with purple colonies with green sheen
E coli produces β-galactosidase breaks lactose into glucose and galactose
Citrobacter, Klebsiella, E coli, Enterobacter, Serratia

Gram- outer membrane layer inhibits entry of penicillinG and vancomycin
May be susceptible to penicillin derivatives (ampicillin, amoxicillin)

Fast fermenters: Klebsiella, E coli, Enterobacter

| Slow fermenters: Citobacter, Serratia

Do Oxidase Test
Oxidase+: Pseudomonas, H pylori
Oxidase-: Shigella, Salmonella, Proteus

Grows @ 42: Campylobacter jejuni

| Grows in alkaline media: Vibrio Cholerae

Gram- diplococci
Both ferment glucose
Produce IgA proteases
Gonococci vs Meningococci

No polysaccharide capsule

Only Glucose fermentation

No vaccine (due to antigenic variation of pilus proteins)

Sexual transmission

Polymorphonuclear leukocytes

Gonorrhea, Septic arthritis, Neonatal conjunctivitis, PID, Fitz-Hugh-Curtis syndrome
Ceftriaxone + (azithromycin or doxycycline) for possible chlamydia coinfection

Polysaccharide capsule
Ferments Glucose and Maltose
Vaccine (none for type B)
Respiratory and oral secretions

Meningococcemia, Meningitis, Waterhouse-Friderichsen syndrome
Rifampin, Ciprofloxacin, Ceftriaxone
Ceftriaxone or PenicillinG

Gram- coccoid rods
Aerosol transmission
Most invasive is capsular type B
Cause mucosal infections (otitis media, conjunctivitis, bronchitis)
IgA protease
Vaccine contains B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid and other proteins. Give @ 2-18 months

"When child has the flu, mom goes to V and X store to buy some chocolate"
Chocolate agar requires V (NAD) and X (hematin). Can also grow with S aureus (provides V)
"haEMOPhilus"
Causes Epiglottitis (cherry red in children), Meningitis, Otitis media, Pneumonia
Rifampin
Ceftriaxone

Gram- rods but stain poorly. Use Silver stain
"French Legionnaire with Silver helmet, sitting around a Charcoal fire with his Iron dagger. He's no Sissy (cysteine)"
Charcoal yeast extract with iron and cysteine
Ag in urine. Hyponatremia
Aerosol transmission from water source. No person-to-perosn
Legionnaires disease, Pontiac fever
Macrolide or Quinolone

Legionella pneumophila

| Severe pneumonia, Fever, GI, CNS symptoms

Legionella pneumophila

| Mild flu-like symptoms

Gram- rod. Aerobic ("think AERuginosa - Aerobic"). Non-lactose fermenting, Oxidase+
Produces pyocyanin (blue-green) pigment. Grape-like odor
Water source
Endotoxin (fever, shock), Exotoxin A (inactivates EF2)
Burn victims, CF pt

"PSEUDOmonas"
Wound and burn infections. Hot tub folliculitis. Malignant Otitis externa in diabetics.
Pneumonia (in CF pt), Sepsis (black lesions on skin), External otitis (swimmers ear), UTI, Drug use, and Diabetic Osteomyelitis
Aminoglycoside + extended spectrum penicillin (piperacillin, ticarcillin)

Fimbriae (cystitis and pyelonephritis)
K capsule (pneumonia, neonatal meningitis)
LPS endotoxin (septic shock)
EIEC, ETEC, EPEC, EHEC

"I = Invades Intestines"
Invades intestinal mucosa
Necrosis and inflammation
Presents like Shigella

"T = Travelers"
Travelers Diarrhea (watery)
Labile toxin, Stable toxin
No inflammation or invasion

"P = Pediatrics"
Diarrhea in children
No toxin produced
adheres to apical surface, flattens villi, and prevents absorption

O157:H7
Does not ferment sorbitol (distinguish it from other E coli)
Swells endothelium --> narrowed lumen --> hemolysis, reduced renal blood flow. Damaged endothelium consumes platelets
Hemolytic Uremic Syndrome: Anemia, Thrombocytopenia, Acute Renal Failure
Shiga-like toxin. Dysentery (toxin alone causes necrosis and inflammation)

"4As"
Aspiration pneumonia, Abscess in lungs and liver, Alcoholics, diAbetics
Gram- Rods. Lactose fermenter
Intestinal flora
Lobal pneumonia in alcoholics and diabetics when aspirated. Nosocomial UTIs
Red currant jelly sputum from polysaccharide capsule

Gram- rods. NonLactose fermenting Oxidase-
Flagella+, Disseminated hematogenously
Many animal reservoirs. Produces Hydrogen sulfide
Antibiotics prolong symptoms
Invades intestinal mucosa. Causes Monocytic response
Can cause bloody diarrhea

Gram- rods. NonLactose fermenting Oxidase-

Flagella-. Cell-to-cell transmission. no hematogenous spread

Human and primate reservoirs. Does not produces Hydrogen sulfide

Antibiotics shorten excretion of organisms in feces

Invades intestinal mucosa. Causes PMN infiltration

Often cause bloody diarrhea

Typhoid fever
Only in humans
Rose spots on the abdomen, fever, headache, diarrhea
Can remain in gallbladder and causes carrier state

Gram- comma shaped oxidase+ that grows at 42 degs C
Bloody diarrhea in children
Fecal-oral transmission
Guillain Barre Syndrome and Reactive Arthritis

Gram- comma shaped oxidase+ that grows in alkaline media
Produces toxin that permanently activates Gs --> ↑cAMP
Rice-water diarrhea endemic in developing countries
Oral rehydration

Gram- coccobacillus
Pet feces, contaminated milk, pork
Mesenteric adenitis that mimics Crohn's or Appendicitis

Gram- rods. Doesn't ferment lactose. Oxidase+, Urease+ (breath test)
Gastritis and duodenal ulcers
Risk factor for Peptic Ulcers, Gastric Adenocarcinoma, Lymphoma
Creates alkaline environment
PPI, Clarithromycin, Amoxicillin, or Metronidazole

Spiral shaped bacteria with axial filaments
"BLT"
Borrelia (big size), Leptospira, Treponema
Only Borrelia can be visualized using aniline dyes (Wright's or Giemsa stain) in light microscopy
Treponema can be visualized by dark-field microscopy

Water contaminated with animal urine
Leptospirosis: flu-like symptoms Jaundice, Photophobia w/ conjunctivitis
Surfers and in tropics (Hawaii)

Icterohemorrhagic leptospirosis: Severe jaundice and Azotemia from liver and kidney dysfunction, Fever, Hemorrhage and anemia

Borrelia burgdorferi

Aniline dyes (Wright's or Giemsa stain) in light microscopy

Tick Ixodes

Mouse

NE USA

"FAKE a key lyme pie"

Facial nerve palsy (bilaterally), Arthritis, Cardiac Block, Erythema Migrans

Doxycycline, Ceftriaxone

1: Erythema chronicum migrans (bull's eye) and flu like symptoms
2: Neurologic (facial nerve palsy) and cardiac (AV block) manifestations
3: Musculoskeletal (chronic monoarthritis and migratory polyarthritis), Neurological (encephalopathy and polyneuropathy), and cutaneous manifestations

Spirochete Treponema pallidum
Dark field microscopy
PenicillinG

Localized disease presenting with painless chancre (with Treponema inside)
Screen with VDRL and confirm with FTA-ABS

Disseminated disease w/ constitutional symptoms, maculopapular rash (palms and soles), Condylomata lata (with Treponema inside)
Screen with VDRL and confirm with FTA-ABS

Gummas (chronic granulomas), Aortitis (vasa vasorum destruction), Neurosyphilis (tabes dorsalis), Argyll Robertson pupil
Broad-based ataxia, +Romberg, Charcot joint, Stroke w/o HTN
Test spinal fluid with VDRL

Congenital Syphilis
Presentation
When does it happen?

Pupils constrict with accommodation but is not reactive to light
Associated with tertiary syphilis
"Prostitute's pupil" accommodates but doesn't react

VDRL detects non-specific antibodies that react with beef cardiolipin
"VDRL"
Viruses (mono, hepatitis), Drugs, RF, Lupus, Leprosy

Flu like syndrome in Syphilis pt immediately after antibiotics are started due to killed bacteria releasing pyrogens

Cat scratch disease from Bartonella Spp

Recurrent fevers from Borrelia recurrentis

| Epidemic Typhus from Rickettsia Prowazekii

Brucellosis/Undulant fever from Brucella Spp

Psittacosis from Chlamydophila psittaci

Q fever from Coxiella burnetii

Ehrlichiosis from Ehrlichia chaffeensis

Tularemia from Francisella tularensis

Cellulitis, Osteomyelitis from Pastuerella multocida

Rocky Mountain Spotted Fever from Rickettsia Rickettsii

Endemic typhus from Rickettsia typhi

| Plague from Yersinia pestis

"I don't have a CLUE why I smell FISH in the VAGINA"
Pleomorphic gram variable rods
Vaginosis: gray vaginal discharge with fishy smell. Non painful
Associated with sexual activity but not an STD
Clue cell or vaginal epithelial cells covered with bacteria
Metronidazole

Overgrowth of certain bacteria in the vagina

Gram-

Obligate intracellular that need CoA and NAD

All over USA

Rocky Mountain Spotted Fever

Rash that starts at wrists and ankles

Gram-. rod-to-coccoid shaped

| Obligate intracellular organisms

Endemic

Fleas

Headache, fever, rash on trunk

Epidemic
Human body louse
Rash starts centrally and spreads out sparing soles and palms

"CARS driving with your palms and soles"

| Coxsackievirus A, Rocky Mountain Spotted Fever, Secondary Syphilis

Ehrlichia (a kind of rickettsia)
No rash
Ticks
Monocytes with morula (berry-like inclusions) in cytoplasm

Anaplasma (a kind of rickettsia)
No rash
Tick
Granulocytes with morula in cytoplasm

Tick feces and cattle placenta release spores that are inhaled by aerosols as spores. No arthropod vectors
Coxiella burnetii (closely related to rickettsia - obligate intracellular parasite)
Presents as pneumonia

Gram- Obligate intracellular parasite
Lacks Muramic Acid and Peptidoglycans
Mucosal infections
Cytoplasmic inclusions seen on Giemsa or Fluorescent Ab-stained smear
Elementary body (small, dense) is infectious and Enters cell via Endocytosis
Reticulate body Replicates in cell by fission. Form seen on tissue culture
Azithromycin (favored) or doxycycline

Causes reactive arthritis, conjunctivitis, non-gonococcal urethritis, and PID

Atypical pneumonia
Aerosol.
Psittaci notable for avian reservoir

A,B,C: Africa, Blindness (follicular conjunctivitis), Chronic infections
D-K: Urethritis/PID, Ectopic pregnancy, Neonatal pneumonia (staccato cough), neonatal conjuntivitis
Neonatal acquired by passage through birth canal
L1,L2,L3: Lymphogranuloma venereum

No Gram stain. No cell wall, Membrane contains sterols for stability
Eaton's agar
Cold agglutinins (IgM) which can agglutinate or lyse RBCs

Walking pneumonia: insidious onset, headache, non-productive cough, diffuse interstitial infiltrate
XR looks worse than pt
Outbreaks in military recruits and prisons. Pts under 30

Gram - coccobacillus

Whooping cough (staccato cough with deep inspirations)

Bordet-Gengou Agar

Pre whooping cough: Erythromycin

Post whooping cough: Supportive care