STEP 1 Gram Negative Bacteria 1 Flashcards by Alex Payvandi

Colonies grown on MacConkey agar are which color?

Pink

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Which bacteria (5) grow on MacConkey’s agar? Which one is weak fermenter? “maConKEE’S agar”

Citrobacter Klebsiella E. coli Enterobacter Serratia (weakly)

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How does E. coli ferment lactose?

E. coli produced B-galactosidase which breaks down lactose into galactose and glucose…FUN!!

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Which bacteria are resistant to penicillin G? How do we kill these bugs? How are these bugs resistant?

Gram negative bacilli are resistant to PCN G.

Gram negative bacilli MAY be resistant to PCN derivatives such as ampicillin and amoxicillin.

The outer membrane of gram negative bacilli bugs inhibits enter of PCN G and vancomycin

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Neisseria comes in two forms Algorithm findings: gram and shape

fermentation

which protease?

N. Gonococci and N. meningococci

Both are GRAM NEGATIVE DIPLOCOCCI

Both ferment GLUCOSE

Both produce IgA protease

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How to tell Neisseria species apart?

“MeninGococci ferment Maltose and Glucose” “Gonococci ferments Glucose only”

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Gonococci: Capsule Maltose fermentation Vaccine Transmission Causes (5) Prophylaxis (2) Treatment (1 + ?)

NO polysacchardie capsule

NO maltose fermentation

NO vaccine (due to rapid antigenic variation of pilus proteins)

Sexually transmitted

Gonorrhea, septic arthritis, neonatal conjunctivitis, PID, and Fitz-Hugh-Curtis Syndrome

Condoms for sex and erythromycin ointment prevents neonatal transmission

Treatment: CEFTRIAXONE + (azithromycin or doxycycline to cross cover for chlamydia)

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Meningococci: Capsule Maltose fermentation Vaccine Transmission Causes (3) Prophylaxis (3) Treatment (2)

Polysaccharide capsule

Maltose and glucose fermentation

Vaccine (none for type B)

Respiratory and oral transmission

Causes meningococcemia, meningitis, and Waterhouse-Friderichsen syndrome

Rifampin, cipro, or ceftriaxone prophylaxis

Treatment: CEFTRIAXONE or PCN G

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Lab findings of haemophilus influenzae (size, gram, shape)

Transmission?

Which strain is most invasive?

What do non-invasive strains cause?

Produces which protease?

Small, gram negative rod

Aerosol transmission

HiB

Mucosal infections: otitis media, conjunctivitis, bronchitis

IgA protease (invades mucosal surfaces)

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H. influenza grows on which agar? What requirements (2)

Chocolate agar Factor V (NAD+) and X (hematin)

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H. influenza causes which disease states? “haEMOPhilus”

Epiglottitis (children) Meningitis Otitis media Pneumonia

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How to treat H. influenza mucosal infections

Amoxicillin (+/- clavulanatic acid)

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How to treat H. influenza meningitis? Prophylaxis?

Ceftriaxone for treatment

Rifampin for prophylaxis

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Describe the HiB vaccine. When to give the HiB vaccine?

Type B capsular polysaccharide conjugated to diphtheria toxoid. Given between 2-18 months

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Legionella staining and shape

Gram NEGATIVE ROD….doesn’t stain well Use SILVER STAIN

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How is legionella cultured?

Grown on CHARCOAL yeast extract culture with IRON and CYSTEINE

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How is legionella detected clinically?

Antigen in urine

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Legionella transmission

Aerosol transmission from environmental water source: air conditioning, hot water tanks, hot tubs NOT FROM PERSON TO PERSON

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Legionella treatment:

macrolide or quinolone

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Legionnaires’ disease symptoms:

Severe pneumonia

Fever

CNS disturbances

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What is Pontiac Fever?

Mild, acute, flu-like syndrome caused by a Legionella species

What will labs show with Legionella?

hyponatremia

Pseudomonas aeruginosa algorithm:

aerobic?

Stain and shape?

Lactose?

Oxidase?

Aerobic, Gram NEGATIVE ROD

Non-lactose fermenting

Oxidase +

Pseudomonas appearance and smell

Pyocyanin (blue-green) pigment Smells likes grapes apparently

Pseudomonas source

Some type of water source...usually a hot tub

Which toxins (2) does Pseudomonas produce

Endotoxin --\> fever and shock Exotoxin A --\> inactivated EF-2

"PSEUDOmonas" is associated with... (8) \*\*There are two more outside of PSEUDO that you must know.

Burn and wound infections Pneumonia (especially in cystic fibrosis) Sepsis External otitis (swimmer's ear) UTI Drug use Diabetic Osteomyelitis Hot tub folliculitis

An immunocompromised patient has rapidly progressive, necrotic cutaneous lesions caused by Pseudomonas bacteremia...what does he have?

Ecthyma gangrenosum

Pseudomonas treatment

Aminoglycoside plus extended spectrum PCN (piperacillin, ticaracillin, cefipime, imipenem, meropenem)

E. coli has 3 virulence factors...what are they and what do they do

1. Fimbriae--cystitis and pyelonephritis (urinary) 2. K capsule--pneumonia, neonatal meningitis 3. LPS endotoxin--septic shock

What is the toxin and mechanism of EIEC? This is similar to which other microbe?

Microbe invades INTESTINAL mucosa and causes NECROSIS and INFLAMMATION Similar to SHIGELLA

What is the presentation of EIEC?

Invasive; dysentery

What is the toxin and mechanism of ETEC?

Produces HEAT-LABILE and HEAT-STABLE ENTERTOXINS No inflammation or invastion

What is the presentation of ETEC?

Traveler's diarrhea (watery)

What is the toxin and mechanism of EPEC?

NO TOXIN produced Adheres to apical surface, FLATTENS VILLI--\> prevents absorption

What is the presentation of EPEC?

Diarrhea, usually in children (P for pediatrics)

What is the most common serotype of EHEC?

O157:H7

What toxin does EHEC produce? What does this toxin cause? What is the triad of this syndrome

EHEC produces the SLT (Shiga-like toxin) Causes Hemolytic-Uremic Syndrome (HUS) HUS: Anemia, thrombocytopenia, and acute renal failure

What is the pathogenesis of hemolysis, decreased renal blood flow, and thrombocytopenia caused by EHEC?

1. Microthrombi form on endothelium damaged by SLT. This causes mechanical hemolysis (schistocytes form) and decreased renal blood flow 2. The microthrombi also consume platelets--\> thrombocytopenia

Where does Klebsiella normally reside? What is it known for causing in alcoholics and diabetics?

Intestinal flora Causes atypical lobar pneumonia when aspirated

Klebsiella has abundant polysaccharide capsules...what does this cause? What does Klebsiella sputum look like?

Very MUCOID colonies Red "currant jelly" sputum

Klebsiella is also known to cause what (3) besides pneumonia?

1. Abscess in lungs 2. Abscess in liver 3. Nosocomial UTIs

What are the 4 A's of Klebsiella (one is a stretch)

Aspiration pneumonia Abscess in lungs and liver Alcoholics di-A-betics (told you it was a stretch)

Salmonella: Flagella? Spread throughout the body? Animal reservoirs? \*\*Hydrogen sulfide production? \*\*Antibiotic effects on disease? Invades where in the body? Bodily response? Bloody diarrhea? \*\*Lactose fermentation?

Salmonella: HAS flagella HEMATOGENOUS spread MANY animal reservoirs \*\*PRODUCES hydrogen sulfide \*\*Antibiotics PROLONG fecal excretion of organism Invades INTESTINAL mucosa and causes a MONOCYTIC response CAN cause bloody diarrhea (not often) \*\*DOES NOT ferment LACTOSE

Shigella: Flagella Spread throughout the body Animal reservoirs \*\*Hydrogen sulfide production \*\*Antibiotic effects on disease Invades where in the body? Bodily response? Bloody diarrhea \*\*Lactose fermentation

Shigella: NO goddamn flagella CELL TO CELL transmission; no hematogenous spread Only reservoir are HUMANS and PRIMATES \*\*DOES NOT produce hydrogen sulfide \*\*Antibiotics SHORTEN fecal excretion of organism Invades INTESTINAL mucosa and causes a PMN response OFTEN causes bloody diarrhea \*\*DOES NOT ferment lactose

E. Coli algorithm findings: gram shape lactose

E. Coli is a gram negative rod FAST fermenter of lactose

Pseudomonas algorithm findings gram shape lactose oxidase

Gram Negative Rod Lactose negative Oxidase positive

Shigella algorithm findings

Gram negative rod Negative lactose Negative oxidase H2S -

Salmonella algorithm findings

Gram negative rod Lactose negative Oxidase negative H2S +

Salmonella typhi causes what? Found only in which animal?

Salmonella typhi causes Typhoid Fever Only found in humans

Salmonella typhi is characterized by what (4)? symptoms How to become a carrier?

Rose spots on abdomen Fever Headache Diarrhea Can remain in gallbladder causing a carrier state