Antibiotics resistant organisms

Inherited resistance in bacteria is accepted as the most important type from the standpoint of the community and the environment. Studies of isolated microorganisms of animal and human origin have demonstrated that plasmids from both sorts of isolates were practically identical. In terms of the dissemination of resistance determinants of R-plasmids, one must regard the problem as involving both humans and animals as vectors. Presence of a large reservoir of antibiotic-resistant organisms in animals has been demonstrated in the United States. 

There has been considerable debate over the role of antimicrobial residues as factors contributing to the relatively high levels of resistance found in human enteric bacterial populations. Whether the relatively high levels of antimicrobial resistance found among enteric bacterial populations arise from medical use, from selection due to exposure to antimicrobial residues, from colonization by antibiotic-resistant organisms related to food production, or from transient colonization of antibiotic-resistant species and transfer of resistance to indigenous populations is undefined (59-62). 

Prophylactic antimicrobial therapy has been shown to reduce the incidence of attacks of diarrhoea but its routine use carries the risk of hindering the diagnosis of serious infection. A wider issue is the possible development and spread of antibiotic-resistant organisms. Thus any benefits to the individual must be weighed against the risk to the community in the future. In most instances prophylactic antimicrobials should not be used but ciprofloxacin (500 mg once daily) may be justified for individuals who must remain well while travelling for short periods to high-risk areas. 

At present, it seems that Europe has taken the lead in the fight against antimicrobial drug resistance. At the Fourth European Conference on Antibiotic Resistance, organized by the European Commission and held in Rome in November 2003, it was strongly emphasized that only a multidisciplinary approach, involving all stakeholders—physicians, researchers, industry, politicians. 

It has also been suggested that antibiotics be administered prophylactically to individuals who think they might have been exposed to the infectious agent. However, there is one serious drawback to this approach it would likely expose a large number of individuals to antibiotics unnecessarily. This, in turn, could contribute to the development of antibiotic resistant organisms and thus compromise the health of others who depend on these same drugs. On balance, it appears that the risks of routine use of antibiotics outweigh the benefits. 

The effect of antibiotics on the Salmonella reservoir varies with the antibiotic susceptibility of the organisms. In previous studies the Salmonella reservoir decreased when animals were infected with an antibiotic-sensitive organism 1) but increased when infected with an antibiotic-resistant organism ( ). Neu and coworkers (9-10) have confirmed that antibiotic resistance is increasing in Salmonella isolated from humans (Table II). Resistance of typhlmurlum to Ampicillin increased from 23.4% in 1969 to 36.9% in 1974, resistance to Streptomycin increased from 27.3% to 45.6% and resistance to Tetracycline increased from 12.5% to 44.8%. 

In summary, antibiotic residues in foods pose certain potential risks as well as potential benefits. The emergence of possibly dangerous antibiotic resistance organisms has led to the consideration that antibiotics commonly used in humans or those which are cross resistant with important antibiotics used in humans, be eliminated from the food supply by banning their use in livestock production. Additional research in this area and that of toxic and/or allergic sensitivity reactions is required to make assessment of their public health risks. Only then can critical risk/benefit decisions be made for antibiotics. 

We must also realize that the clinical simulation models also test efficacy against resident bacterial populations that are not representative of the species encountered in a clinical setting. The subjects used in these studies are not healthcare personnel, and their microbial flora may not represent the types or numbers of organisms found on the hands of healthcare personnel. In addition, the hands of healthcare personnel are more likely to encounter antibiotic-resistant organisms that become transient or colonizers on their hands. Thus, the predictive value of these test methods, given this difference, must also be considered in the evaluation of test products. 

The hazardous microorganisms are primarily derived from the patient s own resident flora. In addition, patients in medical environments are frequently exposed to a wider variety of pathogens and potentially more antibiotic-resistant organisms than the general population. 

Antibiotics in feeds (see Chapter 24) have been used in intensive livestock systems to restrict infections, but their routine administration is now prohibited or discouraged because of the danger of producing antibiotic-resistant organisms. 

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