Search

Like animals and people, insects can serve as both collectors and disseminators of antibiotic resistance genes, as exquisitely demonstrated by a recent study (B. Tian, N. H. Fadhil, J. E. Powell, W. K. Kwong, and N. A. Moran, mBio 3[6]:e00377-12, doi:10.1128/mBio.00377-12, 2012). Notably, the relatively confined ecosystem of the honeybee gut demonstrates a large propensity for harboring a diverse set of tetracycline resistance genes that reveal the environmental burden resulting from the long-time selective pressures of tetracycline use in the honeybee industry. As in humans and animals, these genes have become established in the native, nonpathogenic flora of the insect gut, adding credence to the concept that commensal floras provide large reservoirs of resistance genes that can readily move into pathogenic species. The homology of these tetracycline resistance determinants with those found in tetracycline-resistant bacteria associated with animals and humans strongly suggests a dissemination of similar or identical genes through shared ecosystems. The emergence of linked coresistances (ampicillin and tetracycline) following single-antibiotic therapy mirrors reports from other studies, namely, that long-term, single-agent therapy will result in resistance to multiple drugs. These results contrast with the marked absence of diverse, single- and multiple-drug resistance genes in wild and domestic bees that are not subjected to such selective pressures. Prospective studies that simultaneously track both resistance genes and antibiotic residues will go far in resolving some of the nagging questions that cloud our understanding of antibiotic resistance dissemination.

Treatment of infections is compromised worldwide by the emergence of bacteria that are resistant to multiple antibiotics. Although classically attributed to chromosomal mutations, resistance is most commonly associated with extrachromosomal elements acquired from other bacteria in the environment. These include different types of mobile DNA segments, such as plasmids, transposons, and integrons. However, intrinsic mechanisms not commonly specified by mobile elements-such as efflux pumps that expel multiple kinds of antibiotics-are now recognized as major contributors to multidrug resistance in bacteria. Once established, multidrug-resistant organisms persist and spread worldwide, causing clinical failures in the treatment of infections and public health crises.

The possible association between triclosan and bacterial susceptibility to antibiotic was examined among staphylococci and several species of gram-negative bacteria (GNB) isolated from the hands of individuals in a community setting. Hand cultures from individuals randomized to using either antibacterial cleaning and hygiene products (including a hand soap containing 0.2% triclosan) or nonantibacterial cleaning and hygiene products for a 1-year period were taken at baseline and at the end of the year. Although there was no statistically significant association between triclosan MICs and susceptibility to antibiotic, there was an increasing trend in the association the odds ratios (ORs) for all species were compared at baseline (OR = 0.65, 95% confidence interval [95%CI] = 0.33 to 1.27) versus at the end of the year (OR = 1.08, 95%CI = 0.62 to 1.97) and for GNB alone at baseline(OR = 0.66, 95%CI = 0.29 to 1.51) versus the end of year (OR = 2.69, 95%CI = 0.78 to 9.23) regardless of the hand-washing product used. Moreover, triclosan MICs were higher in some of the species compared to earlier reports on household, clinical, and industrial isolates, and some of these isolates had triclosan MICs in the range of concentrations used in consumer products. The absence of a statistically significant association between elevated triclosan MICs and reduced antibiotic susceptibility may indicate that such a correlation does not exist or that it is relatively small among the isolates that were studied. Still, a relationship may emerge after longer-term or higher-dose exposure of bacteria to triclosan in the community setting.

Background. Much has been written recently about the potential hazards versus benefits of antibacterial (biocide)—containing soaps. The purpose of this systematic literature review was to assess the studies that have examined the efficacy of products containing triclosan, compared with that of plain soap, in the community setting, as well as to evaluate findings that address potential hazards of this use—namely, the emergence of antibiotic-resistant bacteria. Methods. The PubMed database was searched for English-language articles, using relevant keyword combinations for articles published between 1980 and 2006. Twenty-seven studies were eventually identified as being relevant to the review. Results. Soaps containing triclosan within the range of concentrations commonly used in the community setting (0.1%–0.45% wt/vol) were no more effective than plain soap at preventing infectious illness symptoms and reducing bacterial levels on the hands. Several laboratory studies demonstrated evidence of triclosan-adapted cross-resistance to antibiotics among different species of bacteria. Conclusions. The lack of an additional health benefit associated with the use of triclosan-containing consumer soaps over regular soap, coupled with laboratory data demonstrating a potential risk of selecting for drug resistance, warrants further evaluation by governmental regulators regarding antibacterial product claims and advertising. Further studies of this issue are encouraged. [ABSTRACT FROM AUTHOR]

We examined whether household use of antibacterial cleaning and hygiene products is an emerging risk factor for carriage of antimicrobial drug-resistant bacteria on hands of household members. Households (N = 224) were randomized to use of antibacterial or nonantibacterial cleaning and hygiene products for 1 year. Logistic regression was used to assess the influence of antibacterial product use in homes. Antibacterial product use did not lead to a significant increase in antimicrobial drug resistance after 1 year (odds ratio 1.33, 95% confidence interval 0.74-2.41), nor did it have an effect on bacterial susceptibility to triclosan. However, more extensive and longer term use of triclosan might provide a suitable environment for emergence of resistant species. Further research on this issue is needed. [ABSTRACT FROM AUTHOR]