Drug resistance among pathogenic bacteria from animals in Ontario.

This research paper studies the prevalence of drug resistance among bacteria from animals in Ontario, emphasizing that the bovine population is a primary source of certain resistant strains, and revealing potential patterns in their resistance.

Introduction

The article discusses a study conducted in Ontario during 1971-72, focused on the level of antimicrobial drug resistance in over 3000 clinical isolates of animal pathogens. This research was undertaken to gain insights regarding the level of multiple drug resistance patterns prevalent among particular bacteria, specifically within the Enterobacteriaceae family, including strains like Escherichia coli and Salmonella typhimurium.

Resistance Patterns

• The study found that the most common resistance pattern among bovine strains of bacteria was resistance to at least six commonly used drugs.
• The strains also showed resistance to other antibiotics of established therapeutic value.
• Among the various species of animals investigated, the bovine population stood out as a significant source of chloramphenicol-resistant E. coli and S. typhimurium bacteria.

R Factors in Salmonella

• All of the multiply resistant strains of S. typhimurium tested were found to have R factors. An R factor is a plasmid (a small, circular, double-stranded DNA molecule) that imbues multi-drug resistance in bacteria.
• These R factors played a crucial role in the transfer of most of the resistance determinants, including resistance to chloramphenicol, to a recipient E. coli strain during in vitro testing.

Penicillin Resistance

An interesting finding was that unlike many other species and strains, penicillin resistance among Staphylococcus aureus of bovine mammary origin did not exhibit high levels. This suggests that the bacterial strains originating from this particular animal source may remain susceptible to penicillin-based therapies.

Antimicrobial Drug Susceptibility

Despite the general prevalence of resistance, some degree of susceptibility to antimicrobial drugs was still observed among bacterial species such as staphylococci, streptococci, and Corynebacterium sp. Various antimicrobial agents demonstrated effective in vitro activity against these species, indicating potential avenues to combat their proliferation. However, whether these in vitro results are replicated in vivo needs further study.