Gram positive bacili

Corynebacterium spp.

Found as free-living saprophytes.

• water, soil, air

• resistant to drying

• 80 species, of which are 50 are clinically significant

Corynebacterium spp.

They are members of the usual flora of humans and animals. It is also closely related to Mycobacteria and Nocardia.

Corynebacterium spp.

Catalase positive and non motile.

Corynebacterium spp.

Facultative anaerobic

Gram-positive, non-spore-forming rods (arranged in palisades and club-shaped)

Babes-Ernst granules

Corynebacterium diphtheriae

Is the most significant pathogen of Corynebacterium. It causes diphtheria and difficult to speciate other species.

Exotoxin

Is a major virulence factor of Corynebacterium diphtheriae.

Immunoglobulin (IgG)

Toxin is antigenic. Thus can use __ to block toxin effects.

Fragment A

Active fragment of Toxigenic Corynebacterium diphtheriae that inhibits protein synthesis and leads to cell/tissue death.

Fragment B

Fragment of Toxigenic Corynebacterium diphtheriae that binds to specific cell membrane receptors.

Cutaneous Form

Nonrespiratory disease of C. diphtheria that is more prevalent in the tropics and infections occur at the site of minor abrasions.

Loeffler's Serum Agar

Used to demonstrate pleomorphism and metachromatic granules (Babes-Ernst granules).

Cystine-Tellurite Blood Agar (CTBA)

Modified Tinsdale medium. Selective and differential.

Corynebacterium amycolatum

Common on skin and most frequently recovered species.

Corynebacterium jeikeium

Infections from catheters or prosthetic devices. Prosthetic valve endocarditis.

Corynebacterium pseudodiphtheriticum

Opportunistic infection of Corynebacteria. Often endocarditis.

Corynebacterium pseudotuberculosis

-Contact with sheep

-Dermonecrotic toxin

Corynebacterium striatum

• Rare infections

• Normal flora

Corynebacterium ulcerans

• Mastitis in cattle

• Contact with animals or unpasteurized milk

Corynebacterium urealyticum

• Urinary pathogen

• Highly urease positive (within minutes)

Rothia dentocariosa

Normal oral flora (endocarditis).

Listeria monocytogenes

Gram-positive, nonsporulating forming rods (Coccobacillus that often appears like cocci). It is widespread in nature and primarily infect animals (human exposure is limited).

Listeria monocytogenes

Generally from dairy products because it grows at low temperature. Processed meats also can contain this.

Listeriolysin O

Virulence factor of L. monocytogenes that damages phagocytic membrane and prevents killing of the organism.

Listeria monocytogenes

Gram-positive non-spore-forming coccobacillary.

Listeria monocytogenes

Grows well on sheep blood agar (SBA) and chocolate agar. Prefers slightly increased carbon dioxide.

Listeria monocytogenes

Colonies produce a narrow zone of hemolysis (similar to group B Streptococcus).

Listeria monocytogenes

Grows at 4C

Catalase positive

Negative for hippurate hydrolysis

Motile at 25 C (umbrella type motility).

CAMP Test

Produces a "block" type of hemolysis in contrast to "arrow" shape produced by group B Streptococcus.

Erysipelothrix rhusiopathiae

Gram positive, non-spore-forming, pleomorphic rods that is distributed in nature and infection through occupational exposure.

Erysipeloid

Self-limiting localized infection at the site of inoculation and produces painful swelling, usually on the hands or fingers (heals within 3 to 4 weeks).

Endocarditis

May occur in those who have had valve replacements.

Erysipelothrix rhusiopathiae

CO2 is required and grows on blood or chocolate agar (colonies may appear gray or translucent with alpha hemolysis).

Erysipelothrix rhusiopathiae

Catalase negative and produces H2s on TSI.

Arcanobacterium

Catalase negative and have a narrow zone B-hemolysis (black dot on agar surface under the colony).

Arcanobacterium haemolyticum

It causes pharyngitis and pruritic scarlatiniform rash with desquamation of the skin of the hands and feet.

Arcanobacterium pyogenes

It causes sepsis and wound infections in those with animal contact.

Arcanobacterium bernardiae

It causes bacteriemia, wound infections, UTIs, and septic arthritis.

Arcanobacterium haemolyticum

Lipase and lecithinase positive. It also exhibits a CAMP inhibition reaction.

Gardnerella vaginalis

Short, pleomorphic gram-positive rod or coccobacillus.

Gardnerella vaginalis

Its infection is bacterial vaginosis (BV) and produces wet mounts of vaginal fluid.

Bacteria Vaginosis (BV)

Malodorous discharge and vaginal pH of greater than 4.5

Gardnerella vaginalis

Grows at SBA or chocolate agar (5% to 7% CO2 at 35C to 37C).

Human Blood Bilayer Tween (HBT) Agar

Medium of choice of G. vaginalis.

Nocardia spp.

Aerobic, gram positive filamentous rods.

Morphologically resemble fungi.

Nocardia spp.

Slow growers, may take 3 to 6 days.

Primarily affect immunocompromised

Rare but high mortality rate (40%)

Nocardia cyriacigeorgica and Nocardia farcinica

It causes confluent bronchopneumonia.

Nocardia brasiliensis

It causes cutaneous infection termed actinomycotic mycetomas.

Nocardia spp.

Gram-positive branching filaments are seen in direct smears from sputum or aspirated material. It may also show beading appearance.

Paraffin Bait Test

Nocardia can be identified using _.

Bacillus spp.

Found in nature and most are saprophytic and are isolated as contaminants.

Bacillus spp.

Gram-positive large rods with "empty" spaces. Catalase positive.

Bacillus anthracis

Agent of anthrax, a disease in livestock.

Bacillus anthracis

Humans acquire infection by contamination of wound or ingestion or inhalation of spores.

Bacillus anthracis

Large, spore-forming, gram-positive bacilli.

Spores viable for over 50 years

Nonhemolytic on SBA.

Pulmonary anthrax or "Woolsorter's disease"

Acquired through inhalation of spores.

Gastrointestinal Anthrax

Acquired by ingestion of contamination raw meat and inoculates into a lesion on the intestinal mucosa.

Injectional Anthrax

Acquired by direct injection of the endospores into tissue.

Bacillus anthracis

Large, square-ended gram positive rods. Bamboo appearance.

Bacillus anthracis

Nonhemolytic on 5% blood agar; raised, large, grayish-white, irregular, fingerlike edges. "Medusa head" or "Beaten egg whites".

Penicillin

Most isolates of Anthrax are susceptible to _.

Bacillus cereus

It causes food poisoning.

Clostridium perfringens

Boxcar-shaped, gram-negative bacillus. It produces a double zone of hemolysis on Brucella blood agar or blood agar.

Clostridium tetani

Heavily swarming with terminal spores.

Clostridium septicum

Heavily swarming with subterminal spores.

Clostridia spp.

Most frequently encountered in exogenous infections (wounds, ingesting toxins).

Clostridium difficile

Antibiotic-associated diarrhea and pseudomembranous colitis.

Type A

Type of C. perfringens food poisoning through ingestion of enterotoxin causing diarrhea and cramps. Usually self-resolving.

Type C

Type of C. perfringens food poisoning that causes Enteritis necroticans.

Enteritis Necroticans

Acute onset of severe abdominal pain and diarrhea, which is often bloody, and may be accompanied by vomiting.

Type A, B, and E

Botulinum toxins are type A through G, but only types ___ are associated with human disease.

Toxin A

Is now used in medical treatments, including Botox.

Clostridium botulinum

Causes flaccid paralysis (in contrast to tetanus).

Botulism

Its source of infection are home canning and home-cured meats.

Infant Botulism

Ingestion of spores in contaminated honey and colonize the colon and produce toxins.

Clostridium tetani

Causative agent of Tetanus.

Tetanus

Develops from tetanospasmin neurotoxin.

Tetanospasmin Neurotoxin

Inhibits neurons by inhibiting neurotransmitters.

Myonecrosis

It is also known as gas gangrene.

Gas Gangrene

Contaminated wounds from trauma or surgery.

C. perfringens

Most common cause of Myonecrosis.

Myonecrosis

Grow, multiply, and produce toxin.

Alpha Toxin

It causes tissue necrosis and deeper invasion.

C. perfringens

Most common isolate from blood cultures.