Consulting-Specifying Engineer - September 2007 - (Page 32)

seven classes of antibiotics, a similarly small number of fungicidal agents, and there are less vaccines than there are viruses (Ryan, 1994). The result is that as each new treatment becomes ineffective, the arsenal of treatments begins shrinking to dangerously low levels. Some predict that one day new medicines will become obsolete faster than new ones are developed. Increasing drug resistance Some microbes possess the abilities to resist one or more types of treatments, while others may be multi-drug resistant (MDR). Still, A major problem with antiviral drugs is the high frequencies of drug-resistant mutants. others are subject to the phenomenon of pan-drug resistance, which is defined as those microbes that resist all seven major classes of antimicrobial agents: penicillins, cephalosporins, carbapenems, monobactams, quinolones, aminoglycosides and polymyxins (Falagas and Kasiakou, 2005). Drug resistance is defined in terms of an IC50 value, or the concentration that causes 50% growth inhibition, and resistance is defined as a 10-fold increase in IC50 values (Andre et al 2004, Andersson et al 2003). A wide body of evidence is available regarding the drug resistance of individual species of nosocomial pathogens. A selection of data and representative sources are provided here as examples of the scope of the problem. At least 11 major microbes, including species of Streptococcus and Staphylococcus, already are highly resistant to standard antibiotic treatment (Pimentel et al 1998). Rapid increase in drug resistance by disease organisms is caused by the widespread use and overuse of more than 300 antibiotics by the medical profession (ASM “Report of the ASM task force on antibiotic resistance”). In addition, one-half of the antibiotics used in the United States to treat humans also are used to treat disease-infected domestic animals. The concurrent use of antibiotics for both humans and livestock enhances selection for drug-resistant microbes, further exacerbating the problem of antibiotic resistance (Pimentel et al, 1998). Although drug resistance often has been associated with nosocomial infections, innate resistance of bacteria is increasingly being reported. MDR Haemophilus influenzae are being increasingly reported from all over the world (Jain, 1997). Alcaligenes and Acinetobacter species have acquired a wide range of drug resistance. Multidrug resistant strains of Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae, have been recognized among casualties returning from battlefields (Davis et al, 2005). Clinically isolated Pseudomonas aeruginosa have acquired resistance to fluoroquinolones and amikacin, approximately 20% and 5%, respectively. Dr. William Jarvis of the Centers for Disease Control & Prevention warns that, “In at least 70% of the hospital-acquired infections that occur, the organism is resistant to at least one antibiotic.” Bacteria acquire up to 90% of their genetic material from distantly related bacteria species, according to new research from the University of Arizona in Tucson. It is even possible for unrelated species to exchange bits of genetic information that allow them to develop drug resistance. The drug resistance of streptococcal infections, which can cause Scarlet Fever, has increased from 0.8% to 28% in the past decade, according to figures from the Institute of Environmental Science and Research in New Zealand. MRSA has shown up outside hospital settings and has even become a problem in athletics, where it may contaminate sports equipment and facilities (”Benching Bacteria from Athletics: New Sporting Goods Line Answers Call for Protection Against Antibiotic-Resistant Staph Infections”). Multidrug-resistant tuberculosis has caused a resurgence in this disease worldwide, and close to one million people die each year from this disease, once thought to be under control in the West (WHO Europe “World Health Organization Europe Fact Sheet 07/02”). Burkholderia pseudomallei, the causative agent of melioidosis, has shown increasing resistance to antibiotics and has resulted in severe problems with treatment regimes, leading to intensification of the search for new drugs (Perumal et al, 2006). The evolution of drug resistance in microbes can be surprisingly rapid. In 1979, only 6% of European pneumococcus strains were resistant to penicillin, but one decade later that percentage had grown to 44% (Platt, 1996). Viruses are treated with vaccines and antiviral agents, not with antibiotics, and these have generally remained effective over the years. The The multifaceted problem of drug resistance in nosocomial pathogens threatens to extend explosively beyond the boundaries of health care settings. trouble is that each new variant of a virus generally requires a specific antiviral agent and a specific vaccine (Ryan, 1994). Viruses can mutate rapidly, more rapidly than any bacteria, and a vaccine must be quickly developed at the first appearance of any new variant or virus (ASM “Report of the ASM task force on antibiotic resistance”). The greatest concern with viruses is not their abilities to resist treatment, but their propensity to cause explosive epidemics before a vaccine or effective treatment can be developed. Influenza and SARS virus are two examples of viruses that can cause high fatality rates without treatment. A major problem with antiviral drugs is the high frequencies of drugresistant mutants. There are experimental and clinically approved drugs Continued to p.36 32 Consulting-Specifying Engineer • SEPTEMBER, 2007

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - September 2007

Contents M/E Roundtable Cover Story: Airborne Superbugs Third-Party Liability Back to School Product Spotlight Codes & Standards Professional Practices How To New Products Jobs/Cliassifieds Specifier’s Notebook Pure Power Supplement New Technologies, Same Old Transmission Problems Wireless Battery Recharging Solar Concentration Renewables Tracking System A Mighty Wind The Importance of Load Bank Testing Quality Power for Security Systems

Consulting-Specifying Engineer - September 2007

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