24. Anaerobic Bacteria

found in soil, water...

Clostridium ssp

found in mucosal tissues

Bacteroides, Actinomyces ssp

•bacteria lack catalase and/or superoxide dismutase which makes them susceptible to oxidative damage (NO WAY TO DETOXIFY!)

- use other electron acceptors
•Less ATP is produced, so bacteria are typically slow-growers
•CO2 and H2 generated by these reactions, so bacteria often produce gas in tissues
Produce short chain fatty acids during metabolism → contributes to foul smell

- produce major lethal toxins
- produce enterotoxin (superantigen)

- alpha (α)
- beta (β)
- epsilon (ε)
- Iota (I)
- theta (θ)

•binds brush border cells of ileum and jejunum (not duodenum), altering membrane permeability and promoting fluid and electrolyte loss

- cellulitis
- fasculitis
- myonecrosis

- food poisoning (gastroenteritis)

- necrotizing enteritis

2 toxins
•Tetanolysin
•Tetanospasmin

hemolysin

classic A/B toxin
•The A subunit is a Zn peptidase that cleaves SNARE proteins involved in trafficking and release of neurotransmitter-containing vesicles (see slide 38 for SNARE proteins)
•RESULT- inhibitory neurotransmitters glycine and GABA are not released, producing spastic paralysis
•Toxin binding is irreversible, so damage remains and recovery dependent on if/when new axonal termini are generated

- localized
- cephalic
- neonatal

•toxin does not disseminate to CNS, but stays localized to site of primary infection

subset of localized tetanus when head is site of primary infection, very poor prognosis

•infection at umbilical stump with disease progressing to generalized tetanus; high mortality rates with developmental defects in survivors

- endospores found in soil
- Botulinum toxin

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

•Inhibits binding of vesicles with axon terminus thereby preventing release of acetylcholine at neuromuscular junction
•Muscle can't contract, so flaccid paralysis results (wrinkles gone)

- honey and powdered formula
- spore-containing soil and dust (most common)

•Relative lack of intestinal microbiota (often a problem for babies!) allows adherence of spores and colonization of intestine upon germination of spore
•Adults routinely ingest spores which cannot colonize due to competition with normal GI flora

•Recent antibiotic therapy - reduces normal GI flora
•Recent contact with health care setting
•Reduced immune function (esp. elderly) - cannot control infection

•spores resistant to decontamination and persist in hospitals

•Survival of spores in stomach (resistant to gastric acid) → germinate in small intestine
•polysaccharide capsule
•Adherence
•Produce Toxin A (enterotoxin) and Toxin B (cytotoxin)

induces cytokine production

disrupts cytoskeleton by actin depolymerization causing tissue destruction

1. screen stool sample for C. diff with EIA or NAAT assay
2. Toxin A/B EIA to identify toxin-producing infection

•Characterized by chronic granulomatous lesions that form abscesses connected by sinus tracts, macroscopic colonies of the bacteria resemble yellow grains of sand "sulfur granules," lesions firm upon palpation

filamentous arrangement

- Lactobacillus spp
- Bifidobacterium spp
- Eubacterium spp

- Bifidobacterium spp
- Eubacterium spp

Lactobacillus

- used with probiotics

•secretion of lactic acid, H2O2, and bacteriocins (antibacterial substances) which suppresses growth of pathogenic bacteria

•other organisms (Candida, anaerobes) overgrow and cause disease

•Acne vulgaris (teenagers and young adults) - causes acne!
•Opportunistic infections (prosthetic devices or intravascular lines)

•Associated with endodontic abscesses and infections of lacrimal apparatus (lacrimal canaliculitis)

polysaccharide capsule, degrade Ig; assoc. w/ upper respiratory tract infections & gynecological infections

pili for attachment, associated with periodontal disease

upper respiratory tract

•Gram negative bacilli
•Modified LPS (low endotoxin activity)
•capsule
•fimbriae
•Products of anaerobic metabolism inhibit phagocytosis and intracellular killing

human large intestine

•Trauma lead spread to sterile sites in the body and cause infection
•Causes septicemia, abscess, peritonitis, pleuropneumonia, and genital infections
•In general: abdominal infections and abscesses

adhesion

‒fimbriae of P. gingivalis can adhere to epithelium and extracelluar molecules (e.g. fibronectin, fibrinogen) that promotes binding

capsule containing hyaluronic acid

•a group of fastidious, slow-growing, gram-negative bacteria whose growth requires an atmosphere of carbon dioxide. (fastidious means hard to grow!)

normally reside in the oral cavity and have been associated with local infections in the mouth. They are also known to cause severe systemic infections—most often bacterial endocarditis, which can develop on either native or prosthetic valves