GRAM NEG Flashcards by Hagar Grace

Ferment glucose
• Reduce nitrate to nitrites • Oxidase-negative

ENTEROBACTERIACEAE

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IMViC: + + - -

Escherichia coli

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Greenish metallic sheen on EMB or MacConkey agar o

The most common cause of UTI in females

E.coli

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E.coli: Watery diarrhea

ETEC

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E.coli: Watery diarrhea of long durations, mostly infants, often in developing countries

EPEC

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E.col: Bloody diarrhea, hemorrhagic colitis, HUS

EHEC

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E.coli: Bloody diarrhea

Enteroinvasive E. coli

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Persistent watery diarrhea in children and patients with HIV

EAEC

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Have O antigen
o Cultured in XLD
o Transmitted via fecal-oral
route
-lactose megtaive
-non lactose fermenting

Shigella

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Facultative gram-negative rods with large polysaccharide capsule
o Non-motile
o Urease positive
o Ornithine negative
o VP positive
o Inhabitants of the nasopharynx and GIT

Klebsiella

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Pneumonia (Necrotizing): thick, bloody sputum (“currant jelly” sputum), usually
nosocomial, MC cause in alcoholics

Klebsiella

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Large number of organisms needed for infection (> 100,000)
Facultative gram-negative rods
o Non-lactose fermenting
o Cultured on XLD medium

Salmonella

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Biochemical reaction:
-H2S positive
- Lysine positive
-Indole negative
- Urea negative

Salmonella

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Common in patients with sickle cell anemia or cancer

Septicemia (S. choleraesuis)

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Urea positive
o Deaminase positive
o Motile
o Burnt chocolate or chocolate cake odor

Proteus

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Proteus spp that is:
-Indole positive
- H2S positive

P. vulgaris

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Swarming motility

Proetus mirabilis

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Proteus spp that is:
- Swarming motility
- Indole negative
- Complicated UTI: UTI associated with nephrolithiasis (staghorn calculi)

P. mirabilis

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Motile
o Lactose fermenters
o Mucoid colonies
o Contaminated medical devices: respirators and other medical instruments o Ingested from water, vegetables and food products

Enterobacter

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DNAse, ONPG, gelatinase positive
o VP positive; produces RED PIGMENT

Serratia

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Transmitted by bite of an infected flea
Small gram-negative rods with bipolar (safety pin) staining
Bubonic plague

Y. pestis

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Yersinia spp. that is found in GIT swine, rodents, and dogs. Transmission is via ingestion if contaminated food or water

Y. entercolitica

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Wild and domesticated animals (rodents, birds, and rabbits)

MOT: contact with infected animal or ingestion of contaminated food or water

Acute mesenteric lymphadenitis and “pseudotubercles”

Y. pseudotuberculosis

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Most often tend to infect ICU patients

Acinetobacter spp.

BA: smooth, opaque, raised, creamy, and smaller than Enterobacteriaceae, some genospecies are beta-hemolytic Mac: non-lactose fermenter, colonies exhibit a purplish hue that may be mistaken as lactose fermenter

Acinetobacter spp.:

BA: large, smooth, glistening colonies with uneven edges and lavender-green to light purple pigment; greenish discoloration underneath growth; ammonia smell Mac: non-lactose fermenter

Stenotrophomonas maltophilia

dry wrinkled colony appear violet-purple; isolate through the use of Ashdown medium

B. pseudomallei

BA: cream to yellow-orange; smooth and mucoid (24-48 hours) to dry and wrinkled; putrid odor MAC: NLF, but appear as pink colonies (oxidizes lactate) Ashdown: NLF, dry, wrinkled, violet-purple

Burkholderia pseudomallei

BA: spreading and flat, serrated edges; confluent growth; often with metallic sheen; bluish green, red, or brown pigment; often beta-hemolytic; grape-like or corn tortilla- like odor; mucoid colonies seen in CF patients MAC: NLF

Pseudomonas aeruginosa

BA: feather-edged colonies usually surrounded by zone of green discoloration; produces a highly characteristic fruity odor resembling apples or strawberries

ALCALIGENES

causative agent of Cholera

Vibrio cholerae

Gastroenteritis especially in children Severe watery diarrhea (strains that produce a heat-labile and heat-stable enterotoxin) Complications: HUS and kidney disease

Aeromonas spp.

rapid or darting shooting-star motility in dark microscopy

V. cholerae

- Grows on most routine laboratory media -Colonies may be beta-hemolytic -Almond-like odor (ammonium cyanide) - Most strains produce violacein (ethanol soluble violet pigment)

Chromobacterium violaceum

Used to separate Vibrios (susceptible) from other oxidase-positive, glucose fermenters (resistant) and to differentiate V. cholerae O1 and nonO1 (susceptible) from other Vibrio spp. (resistant)

Vibriostatic test

Found in mixed infections resulting from human bites or clenched0fist wounds; Causes soft tissue infections in IV drug users who lick their injection sites

Eikenella corrodens

tendency to pit or corrode the agar, demonstrating a slightly yellow hue after several days, and exude a chlorin bleach odor

Eikenella corrodens

BA: convex, smooth, gray, nonhemolytic; rough and mucoid variants can occur, may have must or mushroom odor

Pasteurella multocida subsp. multocida

Capnophiles; Isolated form the throat of children younger than 4 years old; BA: small, with a zone of beta-hemolysis, may pit the agar

Kingella kingae

requires protoporphyrin IX referred to as X factor and V factor, NAD, or NADP for in vitro growth

HAEMOPHILUS

Chancroid: sexually transmitted disease; Initial symptom is a painful genital ulcer with several satellite lesions and inguinal lymphadenopathy

Haemophilus ducreyi

small coccobacilli or short rods with occasional cells appearing as tangled filaments

H. haemolyticus

either slender or coccobacillary. Traditionally described as “school of fish”

H. ducreyi H. ducreyi

focal suppurative reaction (cat scratch disease) in immunocompetent patients

B. henselae

causative agent of trench fever and bacillary angiomatosis in immunocompromised patients

B. quintana

causative agent of acute hemolytic bacteria (Oroya fever) or a chronic vasoproliferative disease; Carrison disease

B. bacilliformis

irregular, dry, white, “cauliflower-like” colonies that pit the agar or small, circular, tan moist colonies

B. henselae

Bacterial agent isolated and characterized as the causative agent of CD

Afipia felis

fourth most common Campylobacter-like organism isolated from stool and is associated with persistent, watery diarrhea

Arcobacter butzleri

small, curved, or seagull-winged, faintly staining, gram-negative rods

Campylobacter spp

gray to pink or yellow gray and slightly mucoid; some colonies may exhibit a tailing effect along the streak lines

Campylobacter spp.

Spiral-shaped organisms resembling Campylobacter spp. Isolated from the human stomach

Helicobacter spp.

. Mesophilic (20-45OC) • Obligate aerobic • Faintly staining, thin, gram-negative, fastidious bacilli • Do not grow on routine media

LEGIONELLA

3-4mm in diameter, gray-white to blue-green, glistening, convex, and circular, and may exhibit a cut-glass type of internal granular speckling

Legionella

isolated from air-conditioning ducts and colling towers, potable water, large warm-water plumbing system, humidifiers, whirlpools, and technical and medical equipment

Legionella

Capable of survival for extended periods ; small, convex, smooth, translucent, gamma-hemolytic, and slightly yellow and opalescent after at least 48 hours of incubation; evident with - Fever - Chills - Weight loss - Night sweats

Brucella

Gram stain: small coccobacilli that resemble fine grains of sand

Brucella

causative agent of whooping cough

BORDATELLA PERTUSSIS

small and shiny, resembling mercury drops; colonies become whitish-gray with age

Young colonies of B. pertussis and B. parapertussis

MOT: handling the carcasses or skin of infected animals, inhaling infective aerosols or ingesting contaminated water, insect vectors (deerflies and ticks), bitten by carnivores that have eaten the infected animal

F. tularensis

isolated in victims of near- drowning accidents, present in animals and ground water

Francisella philomiragia

Rabbit fever, deer fly fever, and market man’s disease

F. tualrensis: tularemia

MOT: Rat bite, direct contact with rat feces or saliva; haverhill fever

Streptobacillus moniliformis

“fluff balls” or ”breadcrumbs” near the bottom of the tube or on the surface of the sedimented RBC layer in blood culture media

Streptobacillus moniliformis

Cells may appear variable in size or as long, tangled chains and filaments with bulbar swelling Spiral shaped and resemble a string of pearls

Streptobacillus moniliformis

Colonies are embedded in the agar and may have a “fried egg” appearance with a dark center and a flattened lacy edge

Streptobacillus moniliformis

Never been grown in culture ; Clinical signs and symptoms are similar to Streptobacillus moniliformis except that arthritis is rarely seen

Spirillum minus

Young children: otitis media

M. catarrhalis

2nd most commonly reported STI

N. gonnorhoeae

Leading cause of fatal bacterial meningitis in children and adults

N. meningitidis

”kidney- or coffee bean-shaped” diplococci

N. gonorrhoeae

Large, pinkish to brown, opque, smooth; fiable “hockey puck” consistency

Moraxella catarrhalis

Small, grayish white, convex, translucent, shiny colonies w/ either smooth or irregular margins

Neisseria gonorrhoeae

Medium, smooth, round, moist, gray to white; encapsulated strains are mucoid; may be greenish cast in agar underneath colonies

Neisseria meningitidis

GRAM NEG Flashcards

(75 cards)