Microbiology Lecture #9 Notes Controlling Microbes p.236-249

Control: "Kill, inhibit, or remove". Note: emphasis on obliteration, not cooperation. This approach= stringent selection for antibiotic resistance, for example.

Disinfectant resistance now also a major problem. VRE: "Very Resistant to Everything" (properly, "Vancomycin Resistant Enterococci") Antibiotics, disinfectants. Cryptospiridium parvum outbreak caused by alteration in Milwaukee filtration protocol:

"D" value: 90 % killed by heat. Calculate steepness of line in fig. 9.1 for various temperatures. Medically significant = killed by boiling 5-10 minutes (sea level) except spore-formers, hepatitis

Antiseptics = dilute disinfectants, often. Damage skin; nutrients released. Leave some disinfectants on inanimate objects.

Flaming mouths of flasks, test tubes= widely used, but ineffective. Listeria monocytogenes grows in refrig. federal standards = "zero" (impossible to prove)

Synergy between various protocols: Ex.: Heat + acid = potentiated effects. Acid + spores = no germination (tomatoes not troubled by C. botulinum).

A_w: water activity. Most microbes inhibited if A_w dropped few %. Exception: xerophilic fungi. Sensitivity discs (fig 9.2) test effectiveness of disinfectants. Similar test for antibiotics. (Kirby-Bauer)

Protocols must be geared to applications; most efficient. Ex.: 20% saponated cresol same effect as 2%, but more expensive, caustic. Sometimes heat damages items (like antibiotics).

Glassware "melts back together" in dry heat (much longer to sterilize than moist heat). Surfactants: drop surface tension, increase intimacy of contact with microbes. Huge banks of foam in 1960s on Ohio River. Now: biodegradables.

Home canning is much more dangerous that commercial. "Sort of sterile"similar to "a little bit pregnant". "Commercially sterile" = free from commercially significant organisms.

http://www.fda.gov/bbs/topics/NEWS/NEW00603.html

P97-41 FOOD AND DRUG ADMINISTRATION FOR IMMEDIATE RELEASE Arthur Whitmore: 202-205-4144 Dec. 2, 1997 Consumer Inquires: 800-532-4440 FDA APPROVES IRRADIATION OF MEAT FOR PATHOGEN CONTROL The Food and Drug Administration today approved irradiation of meat products for controlling disease-causing micro-organisms. The approval applies to fresh and frozen red meats such as beef, lamb and pork. "Irradiation of meat could prove to be another important tool to protect consumers from food-borne disease," said Michael A. Friedman, M.D., Lead Deputy FDA Commissioner. "The process has been shown to be safe and to significantly reduce bacterial contamination." This approval is based on FDA's thorough scientific review of a substantial number of studies conducted worldwide on the effects of irradiation on a wide variety of meat products. The studies included examination of the chemical effects of radiation, impact on nutrient content of irradiated products, potential toxicity concerns, and effects on microorganisms in or on irradiated products. FDA concluded that irradiation is safe in reducing disease-causing microbes in or on meats, and that it does not compromise the nutritional quality of treated products. FDA has previously approved irradiation of poultry to control pathogens, of pork for control of the trichina parasite, of foods such as fruits, vegetables, and grains to control insects, and of spices, seasonings, and dry enzymes used in food processing to control microorganisms. Food products are treated by subjecting them to radiation from radioactive or machine sources, which kills significant numbers of insects, pathogenic bacteria and parasites. Irradiation does not make food radioactive, nor does it noticeably change taste, texture, or appearance. Irradiation of food products to control food-borne disease in humans has been generally endorsed by the United Nation's World Health Organization and the American Medical Association. Disease-causing microorganisms that can be controlled by irradiation include Escherichia coli 0157:H7 and Salmonella species. FDA's approval is the latest action by the Clinton Administration to take positive steps to reduce the number of consumers suffering from food-borne pathogens. Other steps include the implementation of mandatory Hazard Analysis and Critical Control Point (HACCP) safety programs at seafood, meat, poultry processing plants; expansion of the nation's network of surveillance sites for food-borne disease; funding additional research on food-borne disease control and detection; increasing the number of inspectors and inspections of domestic and imported produce; and implementing industry and consumer education programs on reducing food-borne illness risks. Irradiation, although a potentially useful tool for helping reduce risk of food-borne disease, is a complement to, not a replacement for, proper food-handling practices by producers, processors, and consumers. This approval is in response to a petition filed in August 1994 by Isomedix Inc. of Whippany, N.J.