Aerobic Gram Positive Rods

Listeria monocytogenes

- found in contaminated ?

-usually affects ?

-clin manif?

• dairy, veg, meat, non-pasteurized cheeses → can grow in cold temp

• neonates, pregnant women, immunocompromised (transplant pt)

• flu-like symptoms, sepsis, meningitis, granulomatosis infantisepticum

L. monocytogenes can facultatively persist/multiply in __.

Other bacti?

monophages & macrophages (mono!)

Mycobacteria, Brucella, Legionella, Salmonella, Francisella, Yersinia

L. monocytogenes morphology

short GPR, non-spore

small, grey, translucent w/narrow zone of beta-hem (identical col morph to GBS)

L. monocytogenes

catalase ?

esculin hydrolysis?

CAMP test?

motility?

catalase + (r/o GBS, also GPR not cocci)

esculin hydrolysis, hippurate hydrolysis, CAMP test = positive

tumbling motility in broth

semisolid media → umbrella

Erysipelothrix rhusiopathiae

found in (major resovoir?) → major exposures in?

causes __

cattle, horses, dogs, fish, poultry, rodents; pigs major resovoir → occupational ie farmers, fisherman, butchers

erysipeloid (form of cellulitis); may cause septicemia, endocarditis

Erysipelothrix rhusiopathiae ID
- morph

-biochemical?

• short, slender, straight or curved GPR

• 2 col morph from same specimen!!: small, weakly alpha-hemo, OR larger spreading

• bottle brush look in gelatin agar

• catalase neg

• TSI slant (or KIA agar) → prod H2S → black = +

TSI slant (H2S test)

diff Erysip. rhusiopathiae from other GPR

H2S (Erysip. rhusiopathiae prod) + ferrous ammonium sulfate → black +

inoculate tube w/needle stab/streak → incubate overnight 35C w/ cap loosened → add lead acetone paper to detect H2S gas

pos = black

neg = no black precipitate

Lactobacillus ssp

• found where?

• key role in?

normal flora of human vagina, GI tract, oropharynx

dairy, meats, grain products

fights against Candida vaginitis, bacterial vaginosis, UTI, STDs

Lactobacillus sp

morph

biochem

long, slender, or short coccobacilli, often chains, or spiral

col: pinpoint, a-hem, white, large

catalase = neg

Corynebacterium sp (aka __)

morph

found where?

pleomorphic, non-spore, GPR; may have club-shape or striations; V or L formations, palisading

widely found in soil, water

normal flora of human skin & mucous membranes

Corynebacterium diptheriae

-symptoms

-produces ___ that attacks ___.

-febrile illness, pseudomembrane forms on oropharynx

-exotoxin; heart, central/peripheral nervous system, liver, kidneys

**only exotoxin produced if strain carries beta-corynephage

infects the i-compromised

Corynebacterium diptheriae media

need agar w/ cystine & potassium tellurite

• cystine-tellurite agar or modified Tinsdale medium) → black colony w/brown halo

Loeffler’s serum slant: methylene blue stain → stains metachromatic granules → all Corynebacterium sp + → not recc’d

Corynebacterium diptheriae

biochem?

must be tested for ___ to conclusively call C. diptheriae

DM biochem!

ELEK immunoprecipitate test (immunodiffusion)

other important diptheroid is ___

• like Staph. epidermidis, causes infns from ___

• Abx

• lipophilic → grows better w/___

Coryne. jeikeium

infn of indwelling medical devices, bacteremia

Tween 80

Arcanobacterium haemolyticum

clin manif?

assoc’d w/ acute pharyngitis in children & young adults → self-limiting infn → don’t need to treat w/Abx ; may also cause sepsis, endocarditis, cutaneous ulcers

Arcanobacterium haemolyticum

morph

biochem test

col: similar to beta-hem Strep

delicate, irregular GPR, some branching

reverse CAMP test = pos (inhibits hemolysis of Staph aureus)

reverse CAMP test

requires CAMP S.aureus for beta-lysin

pos = red arrows (inhibition of hemolysis) towards Staph streak → Arcano. haemolyticum

Gardnerella vaginalis clinical significance

-what test can be done by the clinician to rapidly test for bact vaginosis?

bacterial vaginosis → no single organism responsible

-no WBC in GS

-malodorous vaginal discharge

-inc in G. vaginalis & anaerobes & dec in normal Lactobacilli

-clue cells seen

KOH sniff test - smell ammonium smell

G. vaginalis

morph

biochem tests

Gram variable rods

col: beta-hem on V agar (human blood) & non-hem on SBA

oxidase = neg

catalase = neg

hippurate hydrolysis = pos

Bacillus sp. morph & biochem

col: large, spreading, gray-white, irregular margins; many beta-hemo

GPR (easily overdecolorized)

mostly catalase = pos

speciation is based on cell morph, size, spore shape/location, biochem test

Bacillus anthracis importance

• found in ___

agent of anthrax → bioterrorism → development of Laboratory Response Network

herbaceous animals

B. anthracis most common form: ___

cutaneous form

a slow healing painless ulcer w/black eschar & serosanguineous discharge

B. anthracis other high mortality forms (80-90% if untreated): ___ & ____

pulmonary (woolsorter’s disease)

• caused by inhaling endospores

• hemorrhagic mediastinal adenitis (chest infn)

gastrointestinal

• contaminated meats

• fever, bloody vomiting, bloody stool

B. anthracis morph & how to r/o?

large GPR w/ovoid NON-swollen endospores, bamboo-like

col: flat, irregular, non-hem on SBA, “medusa-head”, ground-glass color

non-motile (not performed anymore)

if suspect → sent to PH lab

can treat with penicillin

Bacillus cereus: 2 enterotoxins (food poisoning)

short incubation (1-6 hr): vomiting, heat-stable, assoc’d w/fried rice!

long incubation (8-16hr): diarrhea, heat-labile, assoc’d w/meat, vet, cake, dairy (non-cooked)

B. cereus ID differs from B. anthracis in __ ?

motile, beta-hem, B-lactamase → penicillin-R

B. cereus clin manif

assoc’d w/operations, burns, IVDA

cause sepsis, endocarditis, meningitis, necrotizing pneumonia