Antiseptics and disinfectants are extensively used in hospitals and other health care settings for a variety of topical and hard-surface applications A wide variety of active chemical agents (biocides) are found in these products, many of which have been used for hundreds of years, including alcohols, phenols, iodine, and chlorine Most of these active agents demonstrate broad-spectrum antimicrobial activity; however, little is known about the mode of action of these agents in comparison to antibiotics This review considers what is known about the mode of action and spectrum of activity of antiseptics and disinfectants The widespread use of these products has prompted some speculation on the development of microbial resistance, in particular whether antibiotic resistance is induced by antiseptics or disinfectants Known mechanisms of microbial resistance (both intrinsic and acquired) to biocides are reviewed, with emphasis on the clinical implications of these reports

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Antiseptics and Disinfectants: Activity, Action, and Resistance

Cryptosporidium spp. and cryptosporidiosis.

The issue of whether low-level tolerance to germicides selects for antibiotic-resistant strains is unsettled but might depend on the mechanism by which tolerance is attained. For example, changes in the permeability barrier or efflux mechanisms might affect susceptibility to both antibiotics and germicides, but specific changes to a target site might not. Some researchers have suggested that use of disinfectants or antiseptics (e.g., triclosan) could facilitate development of antibiotic-resistant microorganisms 334, 335, . Although evidence in laboratory studies indicates low-level resistance to triclosan, the concentrations of triclosan in these studies were low (generally <1 μg/mL) and dissimilar from the higher levels used in antimicrobial products (2,000–20,000 μg/mL) 364, . Thus, researchers can create laboratory-derived mutants that demonstrate reduced susceptibility to antiseptics or disinfectants. In some experiments, such bacteria have demonstrated reduced susceptibility to certain antibiotics . There is no evidence that using antiseptics or disinfectants selects for antibiotic-resistant organisms in nature or that such mutants survive in nature. ). In addition, the action of antibiotics and the action of disinfectants differ fundamentally. Antibiotics are selectively toxic and generally have a single target site in bacteria, thereby inhibiting a specific biosynthetic process. Germicides generally are considered nonspecific antimicrobials because of a multiplicity of toxic-effect mechanisms or target sites and are broader spectrum in the types of microorganisms against which they are effective 344, .

/pdf/guideline-for-disinfection-and-sterilization-in-healthcare-1gzqhqy6ow.pdf

Guideline for disinfection and sterilization in healthcare facilities, 2008

The apicomplexan Cryptosporidium parvum is an intestinal parasite that affects healthy humans and animals, and causes an unrelenting infection in immunocompromised individuals such as AIDS patients. We report the complete genome sequence of C. parvum, type II isolate. Genome analysis identifies extremely streamlined metabolic pathways and a reliance on the host for nutrients. In contrast to Plasmodium and Toxoplasma, the parasite lacks an apicoplast and its genome, and possesses a degenerate mitochondrion that has lost its genome. Several novel classes of cell-surface and secreted proteins with a potential role in host interactions and pathogenesis were also detected. Elucidation of the core metabolism, including enzymes with high similarities to bacterial and plant counterparts, opens new avenues for drug development.

https://science.sciencemag.org/content/sci/304/5669/441.full.pdf

Complete genome sequence of the apicomplexan, Cryptosporidium parvum.

Background Small numbers of Cryptosporidium parvum oocysts can contaminate even treated drinking water, and ingestion of oocysts can cause diarrheal disease in normal as well as immunocompromised hosts. Since the number of organisms necessary to cause infection in humans is unknown, we performed a study to determine the infective dose of the parasite in healthy adults. Methods After providing informed consent, 29 healthy volunteers without evidence of previous C. parvum infection, as determined by the absence of anti-cryptosporidium–specific antibodies, were given a single dose of 30 to 1 million C. parvum oocysts obtained from a calf. They were then monitored for oocyst excretion and clinical illness for eight weeks. Household contacts were monitored for secondary spread. Results Of the 16 subjects who received an intended dose of 300 or more oocysts, 14 (88 percent) became infected. After a dose of 30 oocysts, one of five subjects (20 percent) became infected, whereas at a dose of 1000 or more oocysts, ...

https://www.nejm.org/doi/pdf/10.1056/NEJM199503303321304

The Infectivity of Cryptosporidium parvum in Healthy Volunteers

Purified Cryptosporidium parvum oocysts were exposed to ozone, chlorine dioxide, chlorine, and monochloramine. Excystation and mouse infectivity were comparatively evaluated to assess oocyst viability. Ozone and chlorine dioxide more effectively inactivated oocysts than chlorine and monochloramine did. Greater than 90% inactivation as measured by infectivity was achieved by treating oocysts with 1 ppm of ozone (1 mg/liter) for 5 min. Exposure to 1.3 ppm of chlorine dioxide yielded 90% inactivation after 1 h, while 80 ppm of chlorine and 80 ppm of monochloramine required approximately 90 min for 90% inactivation. The data indicate that C. parvum oocysts are 30 times more resistant to ozone and 14 times more resistant to chlorine dioxide than Giardia cysts exposed to these disinfectants under the same conditions. With the possible exception of ozone, the use of disinfectants alone should not be expected to inactivate C. parvum oocysts in drinking water.

https://aem.asm.org/content/aem/56/5/1423.full.pdf

Effects of ozone, chlorine dioxide, chlorine, and monochloramine on Cryptosporidium parvum oocyst viability.

Purified Cryptosporidium parvum oocysts were exposed toozone,chlorine dioxide, chlorine, andmonochloramine. Excystation andmouse infectivity were comparatively evaluated toassessoocystviability. Ozoneand chlorine dioxide more effectively inactivated oocysts thanchlorine andmonochloramine did.Greater than90% inactivation asmeasured byinfectivity was achieved bytreating oocysts with1ppm ofozone (1mg/liter) for 5min.Exposure to1.3ppm ofchlorine dioxide yielded 90%inactivation after 1h,while 80ppm ofchlorine and80ppm ofmonochloramine required approximately 90minfor90%inactivation. Thedataindicate that C.parvum oocysts are30times more resistant toozoneand14times more resistant tochlorine dioxide than Giardia cysts exposed tothese disinfectants underthesame conditions. Withthepossible exception ofozone,the useofdisinfectants alone should notbeexpected toinactivate C.parvum oocysts indrinking water. Cryptosporidium parvum, acoccidian intestinal parasite, infects humansandmaycause gastroenteric disease. Thelife cycle iscompleted intheterminal portions ofthesmall intestine. Anenvironmentally resistant oocyst stage isproducedandpassedintotheenvironment withhostfeces. Unlike other coccidia, theC.parvumoocyst isfully sporulated andreadytoinitiate infection uponexcretion (8). Numerouscasesofcryptosporidial infection havebeen reported inotherwise healthy people since thefirst report of aninfected three-year-old child in1976(19). Immunodefi

M. S. Madore

Papers

Effects of ozone, chlorine dioxide, chlorine, and monochloramine on Cryptosporidium parvum oocyst viability.

Effects ofOzone,Chlorine Dioxide, Chlorine, andMonochloramine on Cryptosporidium parvum OocystViability