Colistin Resistance inEscherichia coliandSalmonella entericaStrains Isolated from Swine in Brazil

Abstract

Reports about acquired resistance to colistin in different bacteria species are increasing, including E. coli of animal origin, but reports of resistance in wild S. enterica of different serotypes from swine are not found in the literature. Results obtained with one hundred and twenty-six E. coli strains from diseased swine and one hundred and twenty-four S. enterica strains from diseased and carrier swine showed a frequency of 6.3% and 21% of colistin-resistant strains, respectively. When comparing the disk diffusion test with the agar dilution test to evaluate the strains, it was confirmed that the disk diffusion test is not recommended to evaluate colistin resistance as described previously. The colistin MIC 90 and MIC 50 values obtained to E. coli were 0.25 μg/mL and 0.5 μg/mL, the MIC 90 and MIC 50 to S. enterica were 1 μg/mL and 8 μg/mL. Considering the importance of colistin in control of nosocomial human infections with Gram-negative multiresistant bacteria, and the large use of this drug in animal production, the colistin resistance prevalence in enterobacteriaceae of animal origin must be monitored more closely.

Impact of antibiotic use in the swine industry

“…Colistin which is an old drug retrieved for use in human medicine to treat critical infections is being used in pigs to treat multi-drug resistant enterotoxigenic E. coli (ETEC) infections. Not surprisingly colistin resistance has been found in pigs strains [5,16,48] although some consider it less common in Europe [49]. A particular issue to note is the use of apramycin in pigs and its capacity to select for apramycin/gentamicin resistant strains through the carriage of the aac(3)-IV gene [50].…”

Multidrug resistance in <i>Escherichia coli</i> carrying integrons isolated from a pig farm with moderate antibiotic use

“…There was no strain resistant for colistin, but disk diffusion test is not the best test to evaluate colistin resistance (Morales et al, 2012). E. coli strains resistant to four and five antibiotics simultaneously were the most prevalent (27.3% and 28.4%, respectively) (Table 2).…”

Increasing burden of urinary tract infections due to intrinsic colistin-resistant bacteria in hospitals in Marseille, France

“…Some hypotheses can be so proposed. First, it is possible that intrinsic CRB infections are mediated by a common source, such as food or the environment [20]. Second, we can suppose that this phenomenon can be due to a Proteus spp.…”