Medical microbiology module 2

Bacillus morphology

β hemolytic

Large gram positive & lives in soil

Spore forming

Large colonies

Translucent or opaque, waxy or mucoid (may slime off plate onto lid)

Bacillus tests

Catalase positive

Bacillus anthracis

G/S: Large, square ended GPR (sometime encapsulated)

^ look like bamboo rods from rods w/ spore

Morphology: non hemolytic, gray, medusa head, tenacious consistency

Bacillus anthracis virulence factors

Capsule - resistant to hydrolysis & isomer of glutamic acid

Toxin - 3 component PRO exotoxin

1 PA (protective antigen)

2 EF (edema factor)

3 LF (lethal factor)

Anthrax

anthrax → meningitis

3 Types:

Cutaneous

(forms black eschars/ malignant pustule)

-Cut contaminated with spores

-drum making incidents

inhalation

-Woolsorter’s disease

-Ragpicker’s disease

gastrointestinal

-ingestion of spore

difficult to diagnose ☹

Anthrax treatment

ciprofloxacin, doxycycline, and others

sus to pen, but some are now res

vaccine to military and researchers

Bacillus anthracis ID

Normally from sterile sites so no selective media

Aerobically & anaerobically

Catalase: +

Non motile

ferments glucose

Produce lecithinase

grows in high salt

OLD METHOD: inoculate isolate onto agar w/ pen → examine for string of pearls

Laboratory Response Network (LRN)

3 levels:

Sentinel, reference, and national laboratories

Objective: diagnose B anthracis

Bacillus cereus

Food poisoning, keratitis, meningitis, and septicemia

Diarrheal: from meat / poultry ingestion, 8-16 hr incubation, lasts 24 hrs

Emetic: Fried rice ingestion, vomiting, 1-5 hr incubation

2 distinct enterotoxins: spores survive cooking → germinate when food cools down

Mild & self limiting

Other Bacillus sp. infections

B. subtilis- infections rare seen as contaminants & may have pigments (yellow pink and brown + very slimy)

B. stearothermophilus- Used for autoclave and sterility testing QC b/c very heat resistant spores

B. thuringiensis- biological insecticide

RESIS: penicillins and cephalosporins

Treat: vancomycin or clindamycin

Corynebacterium / Diptheroids

Normal flora on skin & mucous membrane

cell wall = meso - diaminopimelic acid (m-DAP) & some mycolic acids (waxy) close to mycobacteria + nocardiae

dismissed as contaminant, but body site depends es in immunocompromised patients

G/S: Slightly curved, GPR, club shaped, or coryneform (small gpr in palisades, V or L letter formations

C. diphtheriae

Throat culture

Morphology: very small β hemolysis

G/S: Pleomorphism & metachromatic granules

rare due to vaccine

Exotoxin is virulence factor → lysogenized by bacteriophage with toxin gene (antigenic)

natural host = humans

C. diphtheriae → Diphtheria

symptoms: sore throat, fever, and malaise

toxin is produced locally → pharynx or tonsils

tissue necrosis (white / gray pseudomembrane)

affects kidneys & heart → death by cardiac failure or paralysis

C. diphtheriae

Loffler’s serum: Loeffler’s slant

Cystine - Tellurite blood agar (CTBA): brown or grayish to black halos around dark colonies (selective & differential)

^ colonies appear black (reduction of tellurite) / brown and brown halo (cystinase activity)

urease: -

ferments glucose & maltose

Catalase: +

Nonmotile

Reduces nitrate to nitrite

C. diphtheriae treatment

Treat with antitoxin and penicillin or erythromycin

Toxigenicity testing:

Elek test - immunodiffusion test

alt test: ELISA and immunochromatographic strip assays & PCR detects tox gene

C. jeikeium

Skin flora

infects immunocompromised hosts, IV drugs users, those with catheter lines

common cause of prosthetic valve endo carditis

SUS to vancomycin and tetracycline

RES to macrolide antibiotics is often encountered

Otro corynebacterium

C. urealyticum: Most frequently isolated & clinically significant → primarily a urinary pathogen → encrusted cystitis

-Strict aerobe + slow growing

-non hemolytic, white colonies

-catalase +, Urease +

C. pseudotuberculosis: animal pathogen (zoonosis from sheep)

C. Ulcerans: animal pathogen causes mastitis in cattle (zoonosis)

^ may produce diphtheria toxin

Erysipelothrix rhusiopathiae

1 pathogenic species

G/S: GP thin rods that may form long filaments or short rods, pleomorphic

Morphology: BA and CHOC colonies may appear gray or translucent with alpha hemolysis

Non spore forming, may form long filaments

*disease in animals → butchers, pig farmers acquire disease

Erysipelothrix rhusiopathiae treatment

RESIS Vancomycin

use penicillin or other beta lactam

Erysipelothrix rhusiopathiae disease

Erysipeloid- is an acute bacterial infection of the skin and other organs caused by the microorganism erysipelothrix rhusiopathiae

self limiting localized infection @ site of inoculation

painful swelling on hands & purple red color

Endocarditis- valve replacements

use penicillin or ampicillin

Erysipelothrix rhusiopathiae lab

CO2 req

G/S

Non motile

Catalase: -

Indole: -

VP: -

H2S: +

22C in a gelatin tube → test tube brush like pattern

To differentiate use neomycin: L monocytogenes sus

Gardnerella vaginalis

Normal flora (small amounts)

Absences of lactobacillus → overgrowth of G. vaginalis & mobiluncus & others → Bacterial vaginosis / vaginitis

Association with pre mature rupture of membranes

Lactobacillus

Normal Flora: (mouth, genital, intestinal)

Aerobic and anaerobic strains

Morphology: alpha hemolytic on blood agar

G/S: pinpoint colonies GPR in chains

Probiotic, prevents bacterial vaginosis, protects female host from urogenital infections

Lactic acid from glycogen → v vaginal pH

Lactobacillus disease

Low virulence but clinical infections of bacteremia & endocarditis (high mortality)

Lactobacillus treatment

Freq resis to cephalosporins & vancomycin

Treat with penicillin & aminoglycoside

Listeria monocytogenes

Morphology: β hemolysis, small, round, translucent

G/S: GP non spore forming rods

grows @ 4C

widespread in nature → infect animal → human ingests animal product → sickness

reservoir: unpasteurized dairy products, hot dogs, other processed meats

Listeria monocytogenes disease

virulence factor: ability to penetrate gut to get into blood stream

Pregnant women

-3rd trimester → spontaneous abortion or still birth

Immunocompromised hosts

-pneumonia

Neonates

-sepsis

-meningitis

Hemolysin: listeriolysin O → damages the phagosome membrane

-catalase

-superoxide dismutase

-phospholipase C

-Surface PRO: P60

Listeria monocytogenes treatment

Treat with ampicullin or SXT

Listeria monocytogenes ID

CSF, Blood, Placenta: grows well on blood agar

Catalase: +

Motility @ 25 “umbrella” (tumbling motility in hanging drop)

Hippurate: +

Bile esculin hydrolysis: +

CAMP: + block type hemolysis (Q tip)

G/S

Glucose: +

VP & MR: +

Aerobic actinomycetes

Norcardia, Actimomadura, streptomyces

Culture: sim morphology to fungi

Non spore forming bacteria

Infections: immunocompromised patients (pulmonary & cutaneous infections)

Mycetoma: swelling draining sinuses & granules

Virulence factor: Nocobactin

Nocardia

All soil organism

Aerobic

G/S: GP Rods filamentous, branching

Morphology: chalky, matte / velvety appearance → breadcrumbs, smells like dirt

white or pink or orange colony

Nocardia treatment

Treat with SXT & carbapenem

Do not treat w/ penicillin

Nocardia disease

Chronic bronchopulmonary

misdiagnosed as pulmonary TB :(

-thick purulent sputum

-Necrotic, abscessed lesion

-No scarring or walling off

Cutaneous- N. brasiliensis

localized → progress to invasive

Actinomycotic mycetoma v eumycotic mycetoma

-training sinus tracts

-sulfur granules

Nocardia ID

Grows on BA (slow grower)

encountered on fungal or TB culture media

Partially Acid fast by kinyoun stain

Substrate hydrolysis

Carbohydrare utilization

molecular

Rhodococcus spp & Rothia dentocariosa

R. Equi- Salmon to pink, mucoid

soil → some infections in HIV patients

Rothia dentocariosa

Normal Flora: Upper resp tract & oropharynx

saliva and plaque

may appear as branching filaments