Aerobic gram positive Bacilli

Spore formers

Bacillus Spp.

Non spore formers non-branching

Corynebacterium

Listeria

Erysipelothix

Arcanobacterium and Truperella

Gardenerlla

Branching non spore formers

Nocardia

Strptomyces

Actinomadura

Gordonia

Rhodococcus

Tropheryma

Bacillus spp.

Catalase positive

Most are motile

G+ve large rods with empty spaces

Endospores

Endospores

Formed in aero/anaerobic conditions

Highly resistant to heat, drying and chemicals

Bacillus cereus group

B anthracis

B cereus

B thuringiensis

B mycoides

All genetically similar

Bacillus subtilis

Are contaminants typically not speciated in the laboratory

B cereus biovar anthracis

Potential bioterrorism agent

Has never infected human

Anthrax-like disease in gorillas

Bacillus anthracis general

Large G+ve rods “bamboo” appearence

Agent of anthrax, disease in livestock

Humans acquire infection by contamination of wound, ingestion/inhalation of spores

Bacillus cereus

Causes food poisoning

Opportuistic

Bacillus clinical significance

2 or more sources

Repeated isolation from the same source

Present in direct smear

Compromised host

Bacillus anthracis lab

G+ve rods

Catalase +ve

Non motile

Non-hemolytic

Penicillin Susceptible

Spore former in aerobic conditions

BSL-3

Lecithinase +ve

Bacillus anthracis colony morophology

Raised, dull, opaque, grayish white colonies “Frosted glass”

Edge interlacing chains matted hair “Medusa Head”

Growth with penicillin “String of pearls” former in aerobic conditions

Bacillus anthracis virulence factors

Polypeptide capsule (glutamic acid)

Potent exotoxin

Protective antigen PA

Edema Factor EF

Lethal factor LF

Protective antigen PA Bacillus anthracis

Serves as a binding molecule for EF and LF following attachment to hosts cell surface receptors

EF + PA = Edema

LF + PA = Cell death

Bacillus anthracis infections

Cutaneous “malignant pustule” eschar

Gastrointestinal = consume spores, hard to diagnose

Pulmonary = Wool-sorters disease

Bacillus anthracis treatment

Penicillin high dose

Cipro/Doxy used in initial therapy

Vaccination for high risk

Bacillus cereus infections

Toxin mediated food poisoning

Diarrhea syndrome

Emetic form

B cereus Diarrhea syndrome

Associated with meat, poultry, soups

Incubation period of 8-16 hours

Fever uncommon

Resolves in 24 hours

B cereus Emetic form

Associated with fried rice

Abdominal cramps and vomiting

Incubation period is 1-5 hours

Resolves in 9 hours

Bacillus cereus lab

G+ve rods

Catalase +ve

Beta-hemolytic

Motile

Penicillin Resistant

Lecithinase +ve

Grows on PEA

String of pearls negative

Corynebacterium spp general

G+ve, Catalase +ve, non-motile

Non spore forming rods

L-V shape palisades, Club ends, Diptheroid

When to report Corynebacterium

Isolated from sterile sites CSF

Predominating organism

Urine sample >100,000 CFU and is sole isolate

Diphtheria toxin C diphtheriae

Lysogenic bacteriophage which carries tox gene

Non toxic strains may become toxigenic when infected with tox-carrying bacteriophage

Active fragment + Binding fragment

Diphtheria toxin Active fragment

Cytotoxic

Disrupts protein synthesis

Leads to cell/tissue death

Diphtheria toxin Binding fragment

Binds to specific cell membrane receptors

Mediates entry of the toxin into the cell cytoplasm

Diphtheria toxin in vivo

Alkaline pH 7.8-8.0

Presence of oxygen

Low iron conc needed,

toxin is released in significant amounts when iron in medium is exhauseted

Respiratory disease diphtheria

Incubation 2-5 days

Sore throat, fever, malaise

Toxin produced locally, pharynx/tonsils

White pseudomembrane, bull neck

Systemic infection diphtheria

Toxin absorbed in blood stream

Kidney, hearts, nervous system

Death from cardiac failure

Demyelinating peripheral neuritis = paralysis

Cutaneous infection diphtheriae

More prevalent in tropics

Sites of minor abrasions

May be super infected with Streptococcus pyogenes and/or Staphylococcus aureus

Corynebacterium diphtheriae morphology

G+ve, non-spore forming, rods/club shaped (phosphate reserves)

Palisades

Produce Metachromatic granules or Babes’ Ernst granules = Stain a different color

Corynebacterium diphtheriae culture

Facultative anaerobe, grown best under aerobic conditions

Blood serum = Loeffler serum agar, Loeffler’s slant

SBA = beta hemolysis

Selective/differential Cystine tellurite blood agar CBTA

Loeffler’s slant C diphtheriae

Demonstrate pleomorphic and metachromatic granules under microscope

CTBA C diphtheriae

Modification of Tinsdale medium, selective/differential

Sheep/bovine red blood cells

Cystine - brown halo cystinase activity

Potassium tellurite - inhibit non-coryneform bactera

Black colony = reduction of tellurite

Corynebacterium diphtheriae lab

G+ve, Urease -ve

Beta hemolysis

Catalase +ve

Nitrate +ve

Glucose/maltose +ve

Sucrose/lactose -ve

Elek immunodiffusion test

Isolation C diphtheriae does not mean patient has diphtheria, iron starved colonies will produce toxin

Organisms and controls are streaked on low iron plate 10mm apart

Filter paper with diphtheria antitoxin is added = form lines of precipitation = antibody + antigen complex = +ve

Corynebacterium amycolatum

Normal skin flora

Prosthetic joint infections and endocarditis

Typically immunocompromised

Wide range antibiotic resistance

Corynebacterium jeikeium

Normal skin flora

Most common cause of prosthetic valve endocarditis

Urease -ve

Nitrate reduction -ve

PYR +ve

Choice of drug vancomycin

Corynebacterium pseudodiphteriticum

Normal flora of nasopharynx

Typically NOT pleomorphic, stains evenly in palisades

Respiratory infection in immunocompromised

Corynebacterium pseudotuberculosis

Veterinary pathogen/sheep

Cause granulomatous lymphadenitis

Cystinase +ve = brown halo CTBA

Reverse CAMP test positive = inhibit hemolysis in Staph aureus

Corynebacterium striatum

Normal skin and nasopharynx flora

Typically a contaminant, device related infections

Treat with vancomycin, resistant to daptomycin

Corynebacterium ulcerans

Produce diphtheria like toxins human/cattle

Unpasteurized dairy

Cystinase +ve = brown halo

Urease +ve

Nitrate reduction -ve

Reverse CAMP +ve

Corynebacterium urealyticum

UTIs

Nitrate reduction -ve

Rapid urease +ve

Treat with vancomycin

Listeria monocytogenes pregnant women

Disease in pregnant women/newborn

Spontaneous abortion and stillborn neonates

Chorioamnionitis - infection of placenta and amniotic fluid

Self-limiting - eliminated when birth

Listeria monocytogenes in newborns

Early onset - intrauterine infection

Late onset - meningitis

Granulomatosis infantiseptica - granulomatous, inflammatory, or nodular rash on the skin

Listeria monocytogene immunocompromised/healthy

CNS and endocarditis

Eating contaminated cheese, coleslaw, ice cream, hot dogs, and lunch meat

Listeria monocytogenes virulence factors

Hemolysin

Protein p60

Catalase

Superoxide dismutase

Phospholipase C

L monocytogenes Hemolysin

Listeriolysin O

Damages phagosome membrane, protects organism from macrophages

L monocytogenes p60

Induce phagocytosis of mammalian cells

L monocytogenes Superoxide dismutase

Protect against oxidative stress

L monocytogenes Phospholipase C

Escape host cell phagocytosis and spread

Listeria monocytogenes Morphology/Culture

G+ve, short non-branching bacillus

SBA and Chocolate agar, slightly increased CO2

Narrow zone Beta hemolysis

Cold enrichment used to isolate 4*C for 7 weeks

Listeria monocytogenes lab

G+ve, non-branching

Catalase +ve, 6.5% NaCl +ve

Hydrolyzes esculin +ve

Hippurate hydrolysis +ve

Motility at 25*C, tumbling motility

Umbrella/block type CAMP test +ve

Erysipelothrix rhusiopathiae lab

G+ve, non-branching pleomorphic bacilli

Catalse -ve

Can cause animal disease = FISH, swine, turkey, sheep

Humans acquire through occupational exposure = joint stiffness

Erysipelothrix rhusiopathiae Infection

Erysipeloid = self limiting, painful swelling, usually hands or fingers, heals within 3-4 weeks

Septicemia and endocarditis = valve replacements

Cutaneous / disseminated infections

Erysipelothrix rhusiopathiae Culture

Grows on SBA and CHOC

Alpha hemolysis, CO2 required

Catalse -ve

Produces H2S on TSI slant

Test tube branch like pattern on gelatin stab

Arcanobacterium

Primary human is A haemolyticum = 10 - 20 y/o

T pyogenes = cattle, animal contact

T bernardiae = bacteremia, wound infection, UTI and septic arthritis

Arcanobacterium lab

Gram +ve

Beta hemolysis on SBA

Catalase -ve

Non-motile, non branching

Resistant to penicillin

Reverse CAMP +ve

Arcanobacterium haemolyticum Reverse CAMP

Inhibition of beta-lysins produced by S aureus by phospholipase D produced by A haemolyticum

Gardnerella vaginalis

Gram variable thinner peptidoglycan layer

G+ve, short pleomorphic rods or coccobacillus

Clue cells in smear

Growth on SBA and CHOC

Hippurate hydrolysis +ve

Fishy odor + KOH

Gardenerlla vaginalis infection

Bacterial vaginosis

Reduction in Lactobacillus population in the vagina followed by an increase in pH