Clostridium botulinum and perfringens

Characteristics of Clostridium Gram positive rods in filaments or chains Strict anaerobes (C. bot) to oxygen tolerant (C. perf) Spore forming (endospores) Vegetative cells motile ~55 (C. bot) to 965,000 (C. perf) cases/year in US (#2) Diverse physiologically and biochemically >100 species; only 5 human pathogens C. difficile, C. tetani, C. sordellii Image from Wikipedia

C. botulinum Historically, first recognized foodborne pathogen 1793, outbreak of blunzen in modern day Germany Justinius Kerner, medical officer, identified several cases. Noted more often in larger sausages made with components other than muscle tissue Coined term botulinum (botulus [Lt] = sausage) 1896; determined that this disease caused by toxin

Characteristics of endospores Business end: Low moisture Proteins protecting DNA Endospore stain

Ecology/reservoir Saprophyte Soils (one study suggested 24% of soil samples in US are positive) Aquatic muds (anaerobic, moist, nutrient rich) Spores readily dispersed by dust, aerosols Intestinal tract of animals But not obligatory

Classification of C. botulinum (proteolytic) (non-proteolytic) Properties C. botulinum group I C. botulinum group II C. botulinum group III Neurotoxin A, B, F B, E, F C, D Min. growth temp 10oC 3oC 15oC Opt. growth 35-40oC 18-25oC Max. growth 48oC 45oC NA Min. pH 4.6 5.0 Inhibitory aw 0.94 0.97 Inhibitory NaCl 10% 5% 3% D100oC spores 25 min <0.1 min D121oC spores 0.21 min <0.005 min In US, ~60% due to type A, ~20% type B, 20% type E

Characteristics of toxin Most potent toxin known; LD adult human ~0.01mg Enters bloodstream, targets nerve cells Neurotoxin (not enterotoxin) Inhibits acetylcholine release at neuromuscular junctions Only produced during vegetative growth www.hopkins-gi.org

Disease Foodborne botulinum (intoxication) Incubation period 8h to 8d; oft 12-48 h Double/blurred vision, dilated pupils, drooping eyelids Dysphagia, dysphonia Death by respiratory failure Patient remains mentally aware Infant (adult) botulinum (infection) Honey not recommended to children under 1 yrs FDA study suggests 13% are positive Intestinal environment not fully developed “Floppy baby syndrome” Wound botulinum (infection)

Prevention: mostly a reminder! Prevent growth and toxin production Not possible to prevent contamination Acid and water activity “Potentially hazardous foods” (pH>4.6, aw>0.85) 12D process Sodium nitrite in cured meats Toxin infrequent in high acid foods unless: Insufficient penetration of acid into food Food contaminated with spoilage organisms that raise pH Inactivate spores D121oC of 0.21 min used as “golden rule” Inactivate toxin 70 oC/1 h, boiling for 5 min Study suggests standard pasteurization reduces 99.95-99.99% activity

4 features of contaminated food Food contaminated at source or during processing Food receives treatment that restricts competitive microflora (yeasts, LAB) but permits Clostridium survival Conditions of food are suitable for germination and outgrowth Food consumed cold and/or after insufficient heat treatment to inactivate toxin http://extension.psu.edu/food-safety/food-preservation/safe-methods

Clostridium perfringens

Notable differences from C. bot Is considered an anaerobe, but is aerotolerant Fast doubling time (<10 minutes) Much more common Less severe disease; “self-limiting” 14 toxin types (enterotoxins); 4 are “typing toxins” Type Alpha Beta Epsilon Iota A + - B C D E

C. perfringens disease Infection (not intoxication), high infectious dose (>108) Incubation period ~8-18 hours Some survive gastric transit, get to intestines Vegetative cells sporulate Synthesize toxin Toxin binds to epithelial cells Diarrhea and abdominal cramps Usually resolves spontaneously ~12-24 hours Death rare; elderly or some underlying condition

Characteristics of foodborne illness Beef, poultry (meat, gravies, stews) primarily pH ~5-8.3, temps >15 C Food contaminated with vegetative cells Cells not heat-killed Food temperature abused, not cooled quickly Often when cooking for large groups (group homes, large events)

Policy changing outbreaks Sept 1985: Two sisters and mother develop peripheral weakness and respiratory troubles Type B botulinum toxin in blood Additional cases; link is Vancouver restaurant Garlic was chopped, covered in soybean oil, and stored pH 4.6-5.7 seen in 15 bottles measured

Garlic in oil