Study on acquisition of bacterial antibiotic resistance determinants in poultry litter

Abstract

Antibiotic resistance and the mode of transmission were investigated in bacteria isolated from poultry litter. Total aerobic heterotrophic bacteria were screened and identified for their resistance to different antibiotics such as ampicillin, streptomycin, erythromycin, tetracycline, chloramphenicol, kanamycin, tobramycin, and rifampicin. The distribution of bacteria found in the litter was Staphylococcus (29.1%), which was the predominant group, followed by Streptococcus (25%), Micrococcus (20.8%), Escherichia coli (12.5%), Salmonella (8.3%), and Aeromonas (4.1%). Fifty percent of these isolates were susceptible to ampicillin, 57% to erythromycin, 25% to tetracycline, 4% to chloramphenicol, 40% to kanamycin, 75% to streptomycin, 54% to tobramycin, and 4% to rifampicin. Three randomly selected isolates representing Staphylococcus, Streptococcus, and Micrococcus were examined for plasmids, and plasmid-curing and plasmid-induced transformation studies were conducted. Streptococcus and Micrococcus harbored a plasmid of 4.2 and 5.1 kb, respectively, whereas Staphylococcus did not harbor any plasmids. Plasmids were cured in Streptococcus and Micrococcus at a concentration of 75 and 100 microg/ mL of acridine orange, respectively, and transformation of 4.2- and 5.1-kb plasmids isolated from the Streptococcus and Micrococcus to plasmid-free E. coli DH5alpha strain was possible. In conjugation experiments, the antibiotic resistance profiles of transconjugant cells were found to be the same as the donors with the exception of Staphylococcus. The results of this study suggest that transformation and conjugation could be an important mechanism for horizontal gene transfer between bacteria in poultry litter. An understanding of the mechanism and magnitude of resistance gene transfer may provide a strategy to reduce the potential for dissemination of these genes.

Heat Shock-Enhanced Conjugation Efficiency in Standard Campylobacter jejuni Strains

“…Therefore, based on the findings of this study and the potential high load of C. jejuni in poultry litter (Ͼ10 9 CFU/g feces), C. jejuni may display enhanced ability for HGT during composting. Notably, animal litter could contain various antibiotic-resistant bacteria, either commensals or pathogens, such as Campylobacter, pathogenic E. coli, Salmonella, and Clostridium perfringens (39). Although composting may reduce the load of certain pathogens in litter, this practice may promote the emergence of an antibiotic-resistant pathogen, such as C. jejuni, due to the heat shock-enhanced conjugation observed in this study.…”

Intestinal microbiome of poultry and its interaction with host and diet

“…Such a practice can greatly increase the incidence of horizontal transfer of resistance genes and may contribute to the wide spread of antimicrobial resistance among adverse and pathogenic bacteria and is thus of particular interest. [125][126][127] In addition, virulence genes can also be exchanged among poultry enteric pathogens, increasing the recipient's pathogenicity. 128 The predominant commensal intestinal microorganisms usually possess certain traits which enable them to outcompete other bacteria (especially adverse and pathogenic bacteria) and survive in the GI tract.…”

Characterization of Multidrug-Resistant Escherichia coli Isolates from Animals Presenting at a University Veterinary Hospital

“…The physical linkage of genes, in some cases at least, may explain these epidemiological data (65). Transfer of resistance plasmids between bacteria of veterinary importance, including E. coli, has been demonstrated in vitro and in vivo (14,49).…”