Microbiology Lecture 13

Cannot grow at all in the presence of O2

Obligate anaerobes

General features of Clostridium perfringens

Gram-positive rods, rectangular, anaerobic

Distinctions of Clostridium perfringens from other Clostridium spp.

-Rarely sporulates in vivo or in vitro

-Grows rapidly in tissue and in culture

Clostridium perfringens is transmitted by

inoculation of spores into penetrating wound or ingestion of spores

Risk factor for Clostridium perfringens

poor circulation (e.g., diabetics)

Virulence factors of Clostridium perfringens

Alpha (α) toxin

Alpha (α) toxin =

a lecithinase (phospholipase C)

Disease of Clostridium perfringens

-Myonecrosis (gas gangrene); predominately caused by type A Clostridium perfringens strains

-Anemia; due to alpha toxin

Diagnosis for Clostridium perfringens

-History of penetrating trauma or crush injury

-Appearance of wound - skin is initially red, but rapidly spreads and develops a purplish to black discoloration of skin

-"mousy" odor

-Gas bubbles in tissue visible with imaging

General features of Clostridium botulinum

•Gram-positive bacillus, anaerobe, forms spores

•Environmental pathogen - contaminated soil, honey

Clostridium botulinum is transmitted by

•Adults and older children - ingestion of food containing preformed toxin, "foodborne botulism"

•Infants - consumption of spore-containing food; "infant botulism"

Diagnosis for Clostridium botulinum

detection of toxin in suspected food source or stool of or serum of patient; detection of organism in infant's stool

Virulence factors of Clostridium botulinum

•Endospores - found in soil

•Botulinum toxin - heat-labile A/B neurotoxin - heavy (B) and light (A) chain

•"Risky" foods - In infants: honey and contaminated soil

Disease of Clostridium botulinum in Adults

Foodborne botulism

-Local GI symptoms, blurred vision

-Flaccid paralysis

drooping eyelids, double vision, facial weakness, trouble speaking, difficulty swallowing, and/or difficulty breathing

Flaccid paralysis

Disease of Clostridium botulinum in Infants

Most common form of botulism

•Progresses to flaccid paralysis and respiratory arrest → "floppy baby syndrome"

Susceptibility factor for Clostridium botulinum in Infants

Lack of intestinal microbiota allows adherence of spores and colonization of intestine upon germination of spore

General features of Clostridium tetani

•Gram-positive bacillus, anaerobe, extremely O2-sens

•Terminal spore = "tennis racket" or "drumstick" morphology

Clostridium tetani is transmitted by

-Organism ubiquitous in soil

-Inoculation of bacterial spores into penetrating wound

Diagnosis for Clostridium tetani

clinical manifestations combined with patient history

Treatment for Clostridium tetani

•Surgical debridement of wound

•DTap and Tdap Vaccine (where "T" = tetanus toxoid)

Virulence factors of Clostridium tetani

•Tetanolysin

•Tetanospasmin

Disease of Clostridium tetani

•spastic paralysis

•trismus ("lockjaw")

•opisthotonos (back spasms)

General features of Clostridioides difficile (formerly Clostridium)

Gram-positive, spore-forming, anaerobe

Major predisposing factors for Clostridioides difficile

-Recent antibiotic therapy

-Recent contact with health care setting

-Advanced age and reduced immune function

-Use of proton-pump inhibitors (PPI) - lowers GI acidity

Virulence Factors of Clostridioides difficile

•Spores

•Toxin A (enterotoxin) and Toxin B (cytotoxin)

Production of Toxin A (enterotoxin) and Toxin B (cytotoxin) leads to:

pseudomembrane formation (fibrin and mucin production), watery diarrhea, and PMN influx

Disease of Clostridioides difficile

•Onset is usually post-antibiotic treatment

•Mild diarrhea to severe pseudomembranous colitis (bloody diarrhea), sepsis, toxic megacolon, and death

•Relapse is common due to inability of antibiotics to kill spores

Diagnosis for Clostridioides difficile

screening test (like "GDH") followed by a confirmatory test (like toxin "EIA")

Treatment for Clostridioides difficile

•Antibiotics

•Fecal transplant - restores healthy microbiome

General features of Bacteroides spp.

•Gram-negative anaerobic bacilli

•Colonize oropharynx and GI tract

Virulence factors of Bacteroides spp.

Polysaccharide capsule

Disease of Bacteroides spp.

B. fragilis (very common variation)

•intra-abdominal infections due to composition of polysaccharide capsule that facilitates adhesion to peritoneal surfaces

General features of Actinomyces spp.

•Gram-positive filamentous anaerobic bacteria

•NOT acid-fast (in contrast to Nocardia)

Actinomyces spp. is transmitted by

when normal mucosal barriers are compromised (i.e., trauma, surgery, infection) which allows bacterial access to deeper tissue

Disease of Actinomyces spp.

•Chronic granulomatous lesions become suppurative and form abscesses

•presence of "sulfur granules", yellow to orange in color resembling grains of sand

Diagnosis for Actinomyces spp.

culture or microscopy of purulent exudate, seeing filaments and granules

General features of Cutibacterium acnes

•Small Gram-positive anaerobic rods

•Commonly found on skin, conjunctiva, external ear, oropharynx, female genital tract = part of flora

Disease of Cutibacterium acnes

•Acne vulgaris

•Opportunistic infection of prosthetic joints (esp. shoulders),