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Flashcards in Microbiology - Clinical Bacteriology Deck (50):
1

Gram-positive lab algorithm (129)

2

Identification of gram-positive cocci

  • Staphylococci 
  • Streptococci 

  • Staphylococci
    • NOvobiocin
      • Saprophyticus is Resistant;
      • Epidermidis is Sensitive.
    • On the office’s “staph” retreat, there was NO StRESs.
  • Streptococci
    • Optochin
      • Viridans is Resistant;
      • Pneumoniae is Sensitive.
      • OVRPS (overpass).
    • Bacitracin
      • Group B strep are Resistant;
      • Group A strep are Sensitive.
      • B-BRAS.

3

α- vs. β-hemolytic bacteria

  • α-hemolytic bacteria
  • β-hemolytic bacteria

  • α-hemolytic bacteria
    • Form green ring around colonies on blood agar.
    • Include the following organisms:
      • Streptococcus pneumoniae (catalase (-) and optochin sensitive)
      • Viridans streptococci (catalase (-) and optochin resistant)
  • β-hemolytic bacteria
    • Form clear area of hemolysis on blood agar.
    • Include the following organisms:
      • Staphylococcus aureus (catalase and coagulase (+))
      • Streptococcus pyogenes—group A strep (catalase (-) and bacitracin sensitive)
      • Streptococcus agalactiae—group B strep (catalase (-) and bacitracin resistant)
      • Listeria monocytogenes (tumbling motility, meningitis in newborns, unpasteurized milk)

4

Staphylococcus aureus

  • Properties
  • Causes...
  • TSST
  • S. aureus food poisoning

  • Properties
    • Gram-positive cocci in clusters [A].
    • Protein A (virulence factor) binds Fc-IgG, inhibiting complement activation and phagocytosis. 
    • Commonly colonizes the nose.
    • Staph make catalase because they have more “staff.”
    • Bad staph (aureus) make coagulase and toxins.
  • Causes...
    • Inflammatory disease—skin infections, organ abscesses, pneumonia (often after influenza virus infection), endocarditis, and osteomyelitis
      • Forms fibrin clot around self Ž--> abscess.
    • Toxin-mediated disease—toxic shock syndrome (TSST-1), scalded skin syndrome (exfoliative toxin), rapid-onset food poisoning (enterotoxins)
    • ƒƒMRSA (methicillin-resistant S. aureus) infection—important cause of serious nosocomial and community-acquired infections; resistant to methicillin and nafcillin because of altered penicillin-binding protein
  • TSST
    • A superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation.
    • Presents as fever, vomiting, rash, desquamation, shock, end-organ failure. 
    • Use of vaginal or nasal tampons predisposes to toxic shock syndrome.
  • S. aureus food poisoning
    • Due to ingestion of preformed toxin Ž--> short incubation period (2–6 hr).
    • Enterotoxin is heat stable Ž--> not destroyed by cooking.

5

Staphylococcus

  • Staphylococcus epidermidis
  • Staphylococcus saprophyticus

  • Staphylococcus epidermidis
    • Infects prosthetic devices and intravenous catheters by producing adherent biofilms.
    • Component of normal skin flora
      • Contaminates blood cultures.
    • Novobiocin sensitive.
  • Staphylococcus saprophyticus
    • Second most common cause of uncomplicated UTI in young women (first is E. coli).
    • Novobiocin resistant.

6

Streptococcus pneumoniae

  • Most common cause of...
  • Properties
  • Pneumococcus is associated with...
  • Virulence

  • Most common cause of...
    • ƒƒMeningitis
    • ƒƒOtitis media (in children)
    • Pneumonia
    • Sinusitis
    • S. pneumoniae MOPS are Most OPtochin Sensitive
  • Properties
    • Lancet-shaped, gram-positive diplococci [A].
    • Encapsulated.
    • IgA protease.
    • No virulence without capsule.
  • Pneumococcus is associated with “rusty” sputum, sepsis in sickle cell anemia and splenectomy.

7

Viridans group streptococci

  • Properties
  • Cause...
  • S. sanguinis

  • Properties
    • Viridans streptococci are α-hemolytic.
    • Normal flora of the oropharynx
    • Resistant to optochin, differentiating them from S. pneumoniae, which is α-hemolytic but is optochin sensitive. 
    • Viridans group strep live in the mouth because they are not afraid of-the-chin (op-to-chin resistant)
  • Cause 
    • Dental caries (Streptococcus mutans)
    • Subacute bacterial endocarditis at damaged valves (S. sanguinis)
  • S. sanguinis
    • Sanguis = blood.
    • There is lots of blood in the heart (endocarditis).
    • S. sanguinis makes dextrans, which bind to fibrin-platelet aggregates on damaged heart valves.

8

Streptococcus pyogenes (group A streptococci)

  • Causes...
  • Properties
  • Jones criteria

  • Causes...
    • Pyogenic—pharyngitis, cellulitis, impetigo
      • Impetigo more commonly precedes glomerulonephritis than pharyngitis.
    • Toxigenic—scarlet fever, toxic shock–like syndrome, necrotizing fasciitis
      • Scarlet fever: scarlet rash with sandpaper-like texture, strawberry tongue, circumoral pallor.
    • Immunologic—rheumatic fever, acute glomerulonephritis
    • Pharyngitis can result in rheumatic “phever” and glomerulonephritis.
  • Properties
    • Bacitracin sensitive.
    • Antibodies to M protein enhance host defenses against S. pyogenes but can give rise to rheumatic fever.
    • ASO titer detects recent S. pyogenes infection.
  • J♥NES criteria for rheumatic fever
    • Joints—polyarthritis
    • —carditis
    • Nodules (subcutaneous)
    • Erythema marginatum
    • Sydenham chorea

9

Streptococcus agalactiae (group B streptococci)

  • Properties
  • Causes...
  • Produces...
  • Screening

  • Properties
    • Bacitracin resistant
    • β-hemolytic
    • Colonizes vagina
  • Causes...
    • Pneumonia, meningitis, and sepsis, mainly in babies.
    • Group B for Babies.
  • Produces CAMP factor, which enlarges the area of hemolysis formed by S. aureus.
    • Note: CAMP stands for the authors of the test, not cyclic AMP.
    • Hippurate test (+).
  • Screening
    • Screen pregnant women at 35–37 weeks. 
    • Patients with (+) culture receive intrapartum penicillin prophylaxis.

10

Group D streptococci

  • Enterococci
    • Definition
    • Properties
  • Streptococcus bovis

  • Enterococci
    • Definition
      • Entero = intestine, faecalis = feces, strepto = twisted (chains), coccus = berry.
      • Enterococci (Enterococcus faecalis and E. faecium) are normal colonic flora that are penicillin G resistant and cause UTI, biliary tract infections, and subacute endocarditis (following GI/GU procedures).
      • Lancefield group D includes the enterococci and the nonenterococcal group D streptococci. 
        • Lancefield grouping is based on differences in the C carbohydrate on the bacterial cell wall. 
    • Properties
      • Variable hemolysis.
      • VRE (vancomycin-resistant enterococci) are an important cause of nosocomial infection.
      • Enterococci, hardier than nonenterococcal group D, can grow in 6.5% NaCl and bile (lab test).
  • Streptococcus bovis
    • Colonizes the gut.
    • Can cause bacteremia and subacute endocarditis in colon cancer patients.
    • Bovis in the blood = cancer in the colon.

11

Corynebacterium diphtheriae

  • Causes...
  • Mechanism
  • Symptoms
  • Lab diagnosis
  • Prevention
  • Mnemonic

  • Causes...
    • Diphtheria via exotoxin encoded by β-prophage.
  • Mechanism
    • Potent exotoxin inhibits protein synthesis via ADP-ribosylation of EF-2.
  • Symptoms
    • Pseudomembranous pharyngitis (grayish-white membrane [A]) with lymphadenopathy, myocarditis, and arrhythmias.
  • Lab diagnosis
    • Based on gram-positive rods with metachromatic (blue and red) granules and Elek test for toxin.
    • Black colonies on cystine-tellurite agar.
    • Coryne = club shaped.
  • Prevention
    • Toxoid vaccine prevents diphtheria.
  • ABCDEFG:
    • ADP-ribosylation
    • Beta-prophage
    • Corynebacterium
    • Diphtheriae
    • Elongation Factor 2
    • Granules

12

Spores: bacterial

  • Spores
  • Spore-forming gram-positive bacteria found in soil
  • Other spore formers

  • Spores
    • Some bacteria can form spores at the end of the stationary phase when nutrients are limited.
    • Spores are highly resistant to heat and chemicals.
    • Have dipicolinic acid in their core. 
    • Have no metabolic activity.
    • Must autoclave to kill spores (as is done to surgical equipment) by steaming at 121°C for 15 minutes.
  • Spore-forming gram-positive bacteria found in soil
    • Bacillus anthracis, Clostridium perfringens, C. tetani.
  • Other spore formers
    • B. cereus, C. botulinum, Coxiella burnetii.

13

Clostridia (with exotoxins)

  • Clostridia
  • C. tetani
  • C. botulinum
  • C. perfringens
  • C. difficile

  • Clostridia
    • Gram-positive, spore-forming, obligate anaerobic bacilli.
  • C. tetani
    • Produces tetanospasmin, an exotoxin causing tetanus.
      • Tetanus toxin (and botulinum toxin) are proteases that cleave releasing proteins for neurotransmitters.
    • Tetanus is tetanic paralysis
      • Blocks glycine and GABA release (both are inhibitory neurotransmitters) from Renshaw cells in spinal cord
      • Causes spastic paralysis, trismus (lockjaw), and risus sardonicus.
  • C. botulinum
    • Produces a preformed, heat-labile toxin that inhibits ACh release at the neuromuscular junction, causing botulism.
      • In adults, disease is caused by ingestion of preformed toxin.
      • In babies, ingestion of spores in honey causes disease (floppy baby syndrome).
    • Botulinum is from bad bottles of food and honey (causes a flaccid paralysis).
  • C. perfringens
    • Produces α toxin (“lecithinase,” a phospholipase) that can cause myonecrosis (gas gangrene) and hemolysis.
    • Perfringens perforates a gangrenous leg.
  • C. difficile
    • Produces 2 toxins.
      • Toxin A, enterotoxin, binds to the brush border of the gut.
      • Toxin B, cytotoxin, causes cytoskeletal disruption via actin depolymerization --> pseudomembranous colitis -->Ž diarrhea.
        • Difficile causes diarrhea.
    • Often 2° to antibiotic use, especially clindamycin or ampicillin.
    • Diagnosed by detection of one or both toxins in stool.
    • Treatment: metronidazole or oral vancomycin.
      • For recurring cases, fecal transplant may prevent relapse.

14

Anthrax

  • Caused by...
  • Cutaneous anthrax
  • Pulmonary anthrax

  • Caused by Bacillus anthracis 
    • A gram-positive, spore-forming rod [A] that produces anthrax toxin.
    • The only bacterium with a polypeptide capsule (contains D-glutamate).
  • Cutaneous anthrax
    • Boil-like lesion Ž--> ulcer with black eschar [A] (painless, necrotic) Ž--> uncommonly progresses to bacteremia and death.
  • Pulmonary anthrax
    • Inhalation of spores Ž--> flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock.
    • Woolsorters’ disease—inhalation of spores from contaminated wool.

15

Bacillus cereus

  • Causes...
  • Emetic type
  • Diarrheal type

  • Causes food poisoning.
    • Spores survive cooking rice.
      • Reheated rice syndrome.
    • Keeping rice warm results in germination of spores and enterotoxin formation.
  • Emetic type usually seen with rice and pasta.
    • Nausea and vomiting within 1–5 hr.
    • Caused by cereulide, a preformed toxin.
  • Diarrheal type causes watery, nonbloody diarrhea and GI pain within 8–18 hr.

16

Listeria monocytogenes

  • Properties
  • Causes...
  • Treatment

  • Properties
    • Facultative intracellular microbe
    • Acquired by ingestion of unpasteurized dairy products and deli meats, via transplacental transmission, or by vaginal transmission during birth.
    • Form “rocket tails” (via actin polymerization) that allow them to move through the cytoplasm and into the cell membrane, thereby avoiding antibody.
    • Characteristic tumbling motility
    • Only gram-positive organism to produce LPS.
  • Causes...
    • Amnionitis, septicemia, and spontaneous abortion in pregnant women;
    • Granulomatosis infantiseptica;
    • Neonatal meningitis;
    • Meningitis in immunocompromised patients;
    • Mild gastroenteritis in healthy individuals.
  • Treatment:
    • Gastroenteritis usually self-limited
    • Ampicillin in infants, immunocompromised patients, and the elderly in empirical treatment of meningitis.

17

Actinomyces vs. Nocardia

  • Both
  • Gram
  • Acid fast?
  • Found in...
  • Causes...
  • Treatment

  • Both
    • Form long, branching filaments resembling fungi.
  • Gram
    • A: Gram-positive anaerobe [A]
    • N: Gram-positive aerobe
  • Acid fast?
    • A: Not acid fast
    • N: Acid fast (weak) [B]
  • Found in...
    • A: Normal oral flora
    • N: Soil
  • Causes...
    • A: oral/facial abscesses that drain through sinus tracts, forms yellow “sulfur granules”
    • N: pulmonary infections in immunocompromised and cutaneous infections after trauma in immunocompetent
  • Treatment
    • A: Penicillin
    • N: Sulfonamides

18

1° and 2° tuberculosis (134)

  • PPD(+)
  • PPD(-)
  • Interferon-γ release assay (IGRA)

  • PPD(+) 
    • If current infection, past exposure, or BCG vaccinated.
  • PPD(-) i
    • If no infection or anergic (steroids, malnutrition, immunocompromise) and in sarcoidosis.
  • Interferon-γ release assay (IGRA)
    • A more specific test
    • Has fewer false positives from BCG vaccination.

19

Mycobacteria

  • M. tuberculosis
  • M. kansasii
  • M. avium
  • All mycobacteria
  • TB symptoms
  • Cord factor
  • Sulfatides

  • M. tuberculosis
    • TB, often resistant to multiple drugs
  • M. kansasii
    • Pulmonary TB-like symptoms
  • M. avium–intracellulare
    • Causes disseminated, non-TB disease in AIDS
    • Often resistant to multiple drugs
    • Prophylactic treatment with azithromycin.
  • All mycobacteria are acid-fast organisms [A]
  • TB symptoms
    • Fever, night sweats, weight loss, and hemoptysis.
  • Cord factor in virulent strains
    • Inhibits macrophage maturation
    • Induces release of TNF-α.
  • Sulfatides (surface glycolipids)
    • Inhibit phagolysosomal fusion.

20

Leprosy (Hansen disease)

  • Caused by...
  • 2 forms
    • Lepromatous
    • Tuberculoid
  • Treatment
    • Lepromatous
    • Tuberculoid

  • Caused by Mycobacterium leprae
    • An acid-fast bacillus
    • Likes cool temperatures
    • Infects skin and superficial nerves—“glove and stocking” loss of sensation
    • Cannot be grown in vitro.
    • Reservoir in United States: armadillos.
  • 2 forms
    • Lepromatous
      • Presents diffusely over the skin [A], with leonine (lion-like) facies [B], and is communicable
      • Characterized by low cell-mediated immunity with a humoral Th2 response.
      • Lepromatous can be lethal.
    • Tuberculoid
      • Limited to a few hypoesthetic, hairless skin plaques
      • Characterized by high cell-mediated immunity with a largely Th1- type immune response. 
  • Treatment:
    • Lepromatous
      • Dapsone, rifampin, and clofazimine for 2–5 years
    • Tuberculoid
      • Multidrug therapy consisting of dapsone and rifampin for 6 months

21

Gram-negative lab algorithm (136)

22

Lactose-fermenting enteric bacteria

  • For each:
    • Grow...
    • Examples
    • E. coli
  • MacConkey agar
  • EMB agar

  • MacConkey agar
    • Grow pink colonies
    • Examples: Citrobacter, Klebsiella, E. coli, Enterobacter, and Serratia (weak fermenter).
      • Test with MacConKEES agar.
    • E. coli roduces β-galactosidase, which breaks down lactose into glucose and galactose.
  • EMB agar
    • Grow as purple/black colonies
    • Examples: Klebsiella, E. coli, and Enterobacter
      • Lactose is KEE.
    • E. coli grows purple colonies with a green sheen.

23

Penicillin and gram-negative bugs

  • Gram-negative bacilli are resistant to penicillin G but may be susceptible to penicillin derivatives such as ampicillin and amoxicillin.
  • The gram-negative outer membrane layer inhibits entry of penicillin G and vancomycin.

24

Neisseria

  • Neisseria
  • ​Gonocci vs. Meningococci
    • Polysaccharide capsule?
    • Fermentation
    • Vaccine?
    • Transmission
    • Causes...
    • Prevention
    • Treatment

  • Neisseria
    • Gram-negative diplococci
    • Ferment glucose
    • Produce IgA proteases
    • N. gonorrhoeae is often intracellular (within neutrophils) [A]
  • Gonocci vs. Meningococci
    • Polysaccharide capsule?
      • G: No
      • M: Yes
    • Fermentation
      • GGonococci ferment Glucose
      • MMeninGococci ferment Maltose and Glucose
    • Vaccine?
      • G: No (due to rapid antigenic variation of pilus proteins)
      • M: Yes (none for type B)
    • Transmission
      • G: Sexually transmitted
      • M: Respiratory and oral secretions
    • Causes...
      • G: Gonorrhea, septic arthritis, neonatal  (PID), and Fitz-Hugh–Curtis syndrome
      • M: Meningococcemia [B] and meningitis, Waterhouse-Friderichsen syndrome
    • Prevention
      • G: Condoms prevent sexual transmission; erythromycin ointment prevents neonatal transmission
      • M: Rifampin, ciprofloxacin, or ceftriaxone prophylaxis in close contacts
    • Treatment
      • G: Ceftriaxone + (azithromycin or doxycycline) for possible chlamydia coinfection
      • M: Ceftriaxone or penicillin G

25

Haemophilus influenzae

  • Properties
  • Culture
  • Causes...
  • Treatment
    • Mucosal infections
    • Meningitis
  • Prophylaxis

  • Properties
    • Small gram-negative (coccobacillary) rod. 
    • Aerosol transmission.
    • Most invasive disease caused by capsular type B.
    • Nontypeable strains cause mucosal infections (otitis media, conjunctivitis, bronchitis).
    • Produces IgA protease.
  • Culture
    • Culture on chocolate agar requires factors V (NAD+) and X (hematin) for growth
      • Can also be grown with S. aureus, which provides factor V.
    • When a child has “flu,” mom goes to five (V) and dime (X) store to buy some chocolate.
  • HaEMOPhilus causes...
    • Epiglottitis [A] [B] (“cherry red” in children), Meningitis, Otitis media, and Pneumonia.
    • Does not cause the flu (influenza virus does).
  • Treatment
    • Treat mucosal infections with amoxicillin +/- clavulanate.
    • Treat meningitis with ceftriaxone.
  • Prophylaxis
    • Rifampin prophylaxis in close contacts.
    • Vaccine contains type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid or other protein.
      • Given between 2 and 18 months of age.

26

Legionella pneumophila

  • Growth
  • Detection
  • Transmission
  • Treatment
  • Legionnaires' disease
  • Pontiac fever

  • Growth
    • Gram-negative rod.
    • Gram stains poorly—use silver stain.
    • Grow on charcoal yeast extract culture with iron and cysteine.
    • Think of a French legionnaire (soldier) with his silver helmet, sitting around a campfire (charcoal) with his iron dagger—he is no sissy (cysteine).
  • Detection
    • Detected clinically by presence of antigen in urine. 
    • Lab shows hyponatremia.
  • Transmission
    • Aerosol transmission from environmental water source habitat (e.g., air conditioning systems, hot water tanks).
    • No person-to-person transmission.
  • Treatment
    • Macrolide or quinolone.
  • Legionnaires’ disease
    • Severe pneumonia, fever, GI and CNS symptoms.
  • Pontiac fever
    • Mild flu-like syndrome.

27

Pseudomonas aeruginosa

  • Properties
  • Associated with...
  • Ecthyma gangrenosum
  • Treatment

  • Properties
    • Aerobic gram-negative rod.
    • Non-lactose fermenting, oxidase (+).
    • Produces pyocyanin (blue-green pigment [A]).
    • Has a grape-like odor.
    • Water source.
    • Produces endotoxin (fever, shock) and exotoxin A (inactivates EF-2). 
    • Aeruginosa—aerobic.
      • Think water connection and blue-green pigment.
  • PSEUDOmonas is associated with...
    • Wound and burn infections, Pneumonia (especially in cystic fibrosis), Sepsis, External otitis (swimmer’s ear), UTI, Drug use and Diabetic Osteomyelitis, and hot tub folliculitis. 
      • Think Pseudomonas in burn victims.
    • Malignant otitis externa in diabetics.
    • Chronic pneumonia in cystic fibrosis patients is associated with biofilm
  • Ecthyma gangrenosum
    • Rapidly progressive, necrotic cutaneous lesions caused by Pseudomonas bacteremia.
    • Typically seen in immunocompromised patients.
  • Treatment
    • Aminoglycoside plus extended-spectrum penicillin (e.g., piperacillin, ticarcillin, cefepime, imipenem, meropenem).

28

E. coli

  • E. coli virulence factors
  • For each:
    • Toxin and mechanism
    • Presentation
  • EIEC
  • ETEC
  • EPEC
  • EHEC

  • E. coli virulence factors
    • Fimbriae—cystitis and pyelonephritis
    • K capsule—pneumonia, neonatal meningitis
    • LPS endotoxin—septic shock.
  • EIEC
    • Toxin and mechanism
      • Microbe invades intestinal mucosa and causes necrosis and inflammation.
      • Clinical manifestations similar to Shigella.
    • PresentationInvasive; dysentery.
  • ETEC
    • Toxin and mechanism
      • Produces heat-labile and heat-stable enteroToxins.
      • No inflammation or invasion.
    • Presentation: Travelers’ diarrhea (watery).
  • EPEC
    • Toxin and mechanism
      • No toxin produced.
      • Adheres to apical surface, flattens villi, prevents absorption.
    • Presentation
      • Diarrhea usually in children (Pediatrics).
  • EHEC
    • Toxin and mechanism:
      • O157:H7 is the most common serotype.
        • Produces Shiga-like toxin that causes Hemolytic-uremic syndrome (triad of anemia, thrombocytopenia, and acute renal failure).
        • Also called STEC (Shiga toxin–producing E. coli). 
      • Microthrombi form on endothelium damaged by toxin -->Ž mechanical hemolysis (schistocytes formed) and decreased renal blood flow;
        • Microthrombi consume platelets Ž--> thrombocytopenia.
    • Presentation:
      • Dysentery (toxin alone causes necrosis and inflammation).
      • Does not ferment sorbitol (distinguishes it from other E. coli).

29

Klebsiella

  • An intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated. 
    • Very mucoid colonies caused by abundant polysaccharide capsules.
    • Red “currant jelly” sputum.
  • Also cause of nosocomial UTIs.
  • 4 A’s:
    • Aspiration pneumonia
    • Abscess in lungs and liver
    • Alcoholics
    • di-A-betics

30

Salmonella vs. Shigella

  • Flagella?
  • Transmission
  • Reservoirs
  • Produce hydrogen sulfide?
  • Antibiotics...
  • Invades intestinal mucosa and causes...
  • Bloody diarrhea?
  • Ferments lactose?

  • Flagella?
    • Salmonella: Yes (salmon swim)
    • Shigella: No
  • Transmission
    • Salmonella: Can disseminate hematogenously
    • Shigella: Cell to cell transmission; no hematogenous spread
  • Reservoirs
    • Salmonella: Have many animal reservoirs
    • Shigella: Only reservoirs are humans and primates
  • Produce hydrogen sulfide?
    • Salmonella: Yes
    • Shigella: No
  • Antibiotics...
    • Salmonella: May prolong fecal excretion of organism
    • Shigella: Shorten duration of fecal excretion of organism
  • Invades intestinal mucosa and causes...
    • Salmonella: A monocytic response
    • Shigella: PMN infiltration
  • Bloody diarrhea?
    • Salmonella: Can cause
    • Shigella: Often causes
  • Ferments lactose?
    • Salmonella: No
    • Shigella: No

31

Salmonella typhi

  • Causes...
  • Found...
  • Characterized by...

  • Causes typhoid fever.
  • Found only in humans.
    • Can remain in gallbladder and cause a carrier state.
  • Characterized by rose spots on the abdomen, fever, headache, and diarrhea.

32

Campylobacter jejuni

  • Causes...
  • Transmission
  • Properties

  • Causes...
    • Major cause of bloody diarrhea, especially in children.
    • Common antecedent to Guillain-Barré syndrome and reactive arthritis.
  • Transmission
    • Fecal-oral transmission through foods such as poultry, meat, unpasteurized milk.
  • Properties
    • Comma or S-shaped
    • Oxidase (+)
    • Grows at 42°C 
      • Campylobacter likes the hot campfire”

33

Vibrio cholerae

  • Causes...
  • Properties
  • Found...
  • Treatment

  • Causes...
    • Produces profuse rice-water diarrhea via enterotoxin that permanently activates Gs, increases cAMP. 
  • Properties
    • Comma shaped
    • Oxidase (+)
    • Grows in alkaline media.
  • Found
    • Endemic to developing countries.
  • Treatment
    • Prompt oral rehydration is necessary.

34

Yersinia enterocolitica

  • Transmission
  • Causes...

  • Transmission
    • Usually transmitted from pet feces (e.g., puppies), contaminated milk, or pork.
  • Causes...
    • Causes mesenteric adenitis that can mimic Crohn disease or appendicitis.

35

Helicobacter pylori

  • Causes...
  • Properties
  • Diagnosis
  • Creates...
  • Treatment

  • Causes...
    • Causes gastritis and peptic ulcers (especially duodenal).
    • Risk factor for peptic ulcer, gastric adenocarcinoma and lymphoma.
    • Creates alkaline environment.
  • Properties
    • Curved gram-negative rod
    • Catalase, oxidase, and urease (+)
  • Diagnosis
    • Can use urea breath test or fecal antigen test for diagnosis. 
  • Treatment
    • Most common initial treatment is triple therapy: proton pump inhibitor + clarithromycin + either amoxicillin or metronidazole.

36

Spirochetes

  • Properties
  • Diagnosis

  • Properties
    • The spirochetes are spiral-shaped bacteria with axial filaments and include Borrelia (big size), Leptospira, and Treponema.
    • BLT.
    • B is Big.
  • Diagnosis
    • Only Borrelia can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy.
    • Treponema is visualized by dark-field microscopy.

37

Leptospira interrogans

  • Causes...
  • Found...
  • Weil disease

  • Causes leptospirosis
    • Flu-like symptoms, jaundice, photophobia with conjunctival suffusion (erythema without exudate).
  • Found...
    • Found in water contaminated with animal urine
    • Prevalent among surfers and in tropics (i.e., Hawaii).
  • Weil disease (icterohemorrhagic leptospirosis)
    • ​Severe form with jaundice and azotemia from liver and kidney dysfunction
    • Fever, hemorrhage, and anemia.

38

Lyme disease

  • Caused by...
  • Reservoir
  • Found...
  • Symptoms
  • Treatment

  • Caused by...
    • Borrelia burgdorferi, which is transmitted by the tick Ixodes [A] (also vector for Babesia).
  • Reservoir
    • Natural reservoir is the mouse.
    • Mice are important to tick life cycle.
  • Found...
    • Common in northeastern United States.
  • Symptoms
    • Initial symptoms—erythema chronicum migrans [B], flu-like symptoms, +/- facial nerve palsy.
    • Later symptoms—monoarthritis (large joints) and migratory polyarthritis, cardiac (AV nodal block), neurologic (encephalopathy, facial nerve palsy, polyneuropathy).
    • FAKE a Key Lyme pie:
      • Facial nerve palsy (typically bilateral)
      • Arthritis
      • Kardiac block
      • Erythema migrans
  • Treatment
    • Doxycycline, ceftriaxone.

39

Syphilis

  • Caused by...
  • Treamtent
  • 1° syphilis
  • 2° syphilis
  • 3° syphilis
  • Congenital syphilis

  • Caused by...
    • Spirochete Treponema pallidum.
  • Treatment
    • Penicillin G.
  • 1° syphilis
    • Localized disease presenting with painless chancre [A].
    • If available, use dark-field microscopy to visualize treponemes in fluid from chancre [B].
    • Serologic testing: VDRL/RPR (non-specifc), confirm diagnosis with specific test (e.g., FTA-ABS).
  • 2° syphilis
    • Disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata (also confirmable with dark-field microscopy). 
      • Secondary syphilis = Systemic
    • Serologic testing: VDRL/RPR (non-specific), confirm diagnosis with specific test (e.g., FTA-ABS).
    • Latent syphilis ((+) serology without symptoms) follows.
  • 3° syphilis
    • Gummas (chronic granulomas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis, “general paresis”), Argyll Robertson pupil.
    • Signs: broad-based ataxia, (+) Romberg, Charcot joint, stroke without hypertension.
    • For neurosyphilis: test spinal fluid with VDRL or RPR.
  • Congenital syphilis
    • Saber shins, saddle nose, CN VIII deafness, Hutchinson teeth, mulberry molars.
    • To prevent, treat mother early in pregnancy, as placental transmission typically occurs after first trimester.

40

Argyll Robertson pupil

  • Argyll Robertson pupil constricts with accommodation but is not reactive to light.
  • Associated with 3° syphilis.
  • “Prostitute pupil”—accommodates but does not react.

41

VDRL false positives

  • VDRL detects nonspecific antibody that reacts with beef cardiolipin.
  • Inexpensive, widely available test for syphilis
  • Quantitative, sensitive but not specific.
  • Many false positives, including viral infection (e.g., mononucleosis [EBV], hepatitis), some drugs, and SLE.
  • VDRL:
    • Viruses (mono, hepatitis)
    • Drugs
    • Rheumatic fever
    • Lupus and leprosy

42

Jarisch-Herxheimer reaction

  • Flu-like syndrome after antibiotics are started
  • Due to killed bacteria releasing pyrogens.

43

Zoonotic bacteria

  • Zoonosis
  • For each
    • Disease
    • Transmission & source
  • Anaplasma spp.
  • Bartonella spp.
  • Borrelia burgdorferi
  • Borrelia recurrentis
  • Brucella spp.
  • Campylobacter
  • Chlamydophila psittaci
  • Coxiella burnetii
  • Ehrlichia chaffeensis
  • Francisella tularensis
  • Leptospira spp.
  • Mycobacterium leprae
  • Pasteurella multocida
  • Rickettsia prowazekii
  • Rickettsia rickettsii
  • Rickettsia typhi
  • Yersinia pestis

  • Zoonosis
    • Infectious disease transmitted between animals and humans.
  • Anaplasma spp.
    • Disease: Anaplasmosis
    • Transmission & source: Ixodes ticks (live on deer and mice)
  • Bartonella spp.
    • Disease: Cat scratch disease, bacillary angiomatosis
    • Transmission & source: Cat scratch
  • Borrelia burgdorferi
    • Disease: Lyme disease
    • Transmission & source: Ixodes ticks (live on deer and mice)
  • Borrelia recurrentis
    • Disease: Relapsing fever
    • Transmission & source: Louse (recurrent due to variable surface antigens)
  • Brucella spp.
    • Disease: Brucellosis/undulant fever
    • Transmission & source: Unpasteurized dairy
  • Campylobacter
    • Disease: Bloody diarrhea
    • Transmission & source: Puppies, livestock (fecal-oral, ingestion of undercooked meat)
  • Chlamydophila psittaci
    • Disease: Psittacosis
    • Transmission & source: Parrots, other birds
  • Coxiella burnetii
    • Disease: Q fever
    • Transmission & source: Aerosols of cattle/sheep amniotic fluid
  • Ehrlichia chaffeensis
    • Disease: Ehrlichiosis
    • Transmission & source: Lone Star ticks
  • Francisella tularensis
    • Disease: Tularemia
    • Transmission & source: Ticks, rabbits, deer fly
  • Leptospira spp.
    • Disease: Leptospirosis
    • Transmission & source: urine
  • Mycobacterium leprae
    • Disease: Leprosy
    • Transmission & source: Humans with lepromatous leprosy; armadillo (rare)
  • Pasteurella multocida
    • Disease: Cellulitis, osteomyelitis
    • Transmission & source: Animal bite, cats, dogs
  • Rickettsia prowazekii
    • Disease: Epidemic typhus
    • Transmission & source: Louse
  • Rickettsia rickettsii
    • Disease: Rocky Mountain spotted fever
    • Transmission & source: Dermacentor ticks
  • Rickettsia typhi
    • Disease: Endemic typhus
    • Transmission & source: Fleas
  • Yersinia pestis
    • Disease: Plague
    • Transmission & source: Fleas (rats and prairie dogs are reservoirs)

44

Gardnerella vaginalis

  • Properties
  • Associations
  • Characterized by...
  • Treatment

  • Properties
    • A pleomorphic, gram-variable rod that is involved in vaginosis.
    • Presents as a gray vaginal discharge with a fishy smell
    • Nonpainful (vs. vaginitis).
  • Associations
    • Associated with sexual activity, but not sexually transmitted.
  • Characterized by...
    • Bacterial vaginosis is also characterized by overgrowth of certain anaerobic bacteria in vagina.
    • Clue cells, or vaginal epithelial cells covered with Gardnerella bacteria, are visible under the microscope (arrow) [A].
  • Treatment
    • Metronidazole or (to treat anaerobic bacteria) clindamycin.
  • I don’t have a clue why I smell fish in the vagina garden!

45

Rickettsial diseases and vector-borne illness

  • Treatment for all
  • Rash common dieases
  • Rash rare dieases

  • Treatment for all
    • Doxycycline.
  • Rash common dieases
    • Rocky Mountain spotted fever
    • Typhus
  • Rash rare dieases
    • Ehrlichiosis
    • Anaplasmosis
    • Q fever

46

Rickettsial diseases and vector-borne illness:
Rash common

  • Rocky Mountain spotted fever
    • Properties
    • Transmission
    • Found...
    • Findings
  • Typhus
    • Transmission
    • Findings

  • Rocky Mountain spotted fever
    • Properties
      • Rickettsiae are obligate intracellular organisms that need CoA and NAD+ because they cannot synthesize ATP.
    • Transmission
      • Rickettsia rickettsii, vector is tick.
    • Found...
      • Despite its name, disease occurs primarily in the South Atlantic states, especially North Carolina. 
    • Findings
      • Rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles [A].
      • Classic triad—headache, fever, rash (vasculitis).
      • Palms and soles rash is seen in Coxsackievirus A infection (hand, foot, and mouth disease), Rocky Mountain spotted fever, and 2° Syphilis 
        • You drive CARS using your palms and soles
  • Typhus
    • Transmission
      • Endemic (fleas)—R. typhi.
      • Epidemic (human body louse)—R. prowazekii.
    • Findings
      • Rash starts centrally and spreads out, sparing palms and soles.
  • Rickettsii on the wRists, Typhus on the Trunk.

47

Rickettsial diseases and vector-borne illness:
Rash rare

  • Ehrlichiosis
  • Anaplasmosis
  • Q fever

  • Ehrlichiosis
    • Ehrlichia; vector is tick.
    • Monocytes with morulae [B] (berry-like inclusions) in cytoplasm.
  • Anaplasmosis
    • Anaplasma, vector is tick.
    • Granulocytes with morulae in cytoplasm.
  • Q fever
    • Coxiella burnetii; no arthropod vector.
    • Tick feces and cattle placenta release spores that are inhaled as aerosols.
    • 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.
    • Not in the Rickettsia genus, but closely related.

48

Chlamydiae

  • Properties
  • Forms
  • Chlamydia trachomatis
  • C. pneumoniae and C. psittaci
  • Treatment
  • Lab diagnosis

  • Properties
    • Chlamydiae cannot make their own ATP.
    • They are obligate intracellular organisms that cause mucosal infections.
      • Chlamys = cloak (intracellular)
    • The chlamydial cell wall is unusual in that it lacks muramic acid.
  • 2 forms
    • Elementary body (small, dense) 
      • Enfectious” and Enters cell via Endocytosis
      • Transforms into reticulate body.
    • Reticulate body
      • Replicates in cell by fission
      • Reorganizes into elementary bodies.
  • Chlamydia trachomatis
    • Causes reactive arthritis (Reiter syndrome), follicular conjunctivitis [A], nongonococcal urethritis, and PID.
  • C. pneumoniae and C. psittaci
    • Cause atypical pneumonia
    • Transmitted by aerosol.
    • Chlamydophila psittaci—notable for an avian reservoir.
  • Treatment
    • Azithromycin (favored because one-time treatment) or doxycycline.
  • Lab diagnosis
    • Cytoplasmic inclusions seen on Giemsa or fluorescent antibody–stained smear.

49

Chlamydia trachomatis serotypes

  • Types A, B, and C 
  • Types D–K 
  • Types L1, L2, and L3 

  • Types A, B, and C
    • Chronic infection, cause blindness due to follicular conjunctivitis in Africa.
    • ABC = Africa/Blindness/Chronic infection.
  • Types D–K
    • Urethritis/PID, ectopic pregnancy, neonatal pneumonia (staccato cough), neonatal conjunctivitis.
    • D–K = everything else.
    • Neonatal disease can be acquired during passage through infected birth canal.
  • Types L1, L2, and L3
    • Lymphogranuloma venereum—small, painless ulcers on genitals --> swollen, painful inguinal lymph nodes that ulcerate (“buboes”).
    • Treat with doxycycline.

50

Mycoplasma pneumoniae

  • Properties
  • Causes...
  • Treatment

  • Properties
    • No cell wall.
    • Not seen on Gram stain.
    • Bacterial membrane contains sterols for stability.
    • Grown on Eaton agar.
    • High titer of cold agglutinins (IgM), which can agglutinate or lyse RBCs.
  • Causes...
    • Classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, patchy or diffuse interstitial infiltrate). 
    • Mycoplasmal pneumonia is more common in patients <30 years old.
    • Frequent outbreaks in military recruits and prisons.
    • X-ray looks worse than patient.
  • Treatment
    • Macrolide, doxycycline, or fluoroquinolone (penicillin ineffective since Mycoplasma have no cell wall).

Decks in First Aid Class (92):