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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Characterization and Interventions for Foodborne Pathogens » Research » Publications at this Location » Publication #376455
Research Project: Advanced Development of Innovative Technologies and Systematic Approaches to Foodborne Hazard Detection and Characterization for Improving Food Safety

Location: Characterization and Interventions for Foodborne Pathogens

Title: Animal-use antibiotics induce cross-resistance in bacterial pathogens to human therapeutic antibiotics

Author
item SINGH, ATUL - Purdue University
item BHUNIA, ARUN - Purdue University

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2019
Publication Date: 7/25/2019
Citation: Singh, A.K., Bhunia, A. 2019. Animal-use antibiotics induce cross-resistance in bacterial pathogens to human therapeutic antibiotics. Current Microbiology. 76:1112–1117. https://doi.org/10.1007/s00284-019-01744-2.
DOI: https://doi.org/10.1007/s00284-019-01744-2

Interpretive Summary: Exposure of bacteria to a sub-lethal dosage of antibiotics is one of the major causes of the onset of antibiotic resistance. Therefore, we assessed the emergence of antibiotic cross-resistance in pathogenic bacteria (Salmonella enterica serovar Enteritidis, Klebsiella pneumoniae, Staphylococcus aureus, and Listeria monocytogenes) after exposure to a sub-lethal dose of veterinary feed directive (VFD) antibiotics, tilmicosin and florfenicol. Pre-exposure of these bacteria to a sub-inhibitory concentration of tilmicosin and florfenicol, increased cross-resistance to ampicillin, tetracycline, and nalidixic acid from 1.25 to 40-fold compared to bacteria that were not exposed to the antibiotics. This study could serve as a foundation to understand the mechanisms of acquired cross-resistance to traditional therapeutic antibiotics, and to develop strategies to alleviate such problems by using alternative antimicrobials.

Technical Abstract: Exposure of bacteria to a sub-lethal dosage of antibiotic is one the major causes for the onset of antibiotic resistance. Therefore, we aimed to assess the emergence of antibiotic cross-resistance in bacteria after exposure to a sub-lethal dose of veterinary feed directive (VFD) antibiotics, tilmicosin, and forfenicol. The minimum inhibitory concentrations (MICs) of tilmicosin and forfenicol against Salmonella enterica serovar Enteritidis, Klebsiella pneumoniae, Staphylococcus aureus, and Listeria monocytogenes were determined. Next, the pathogens were exposed to a sub-inhibitory concentration of tilmicosin (0.5, 5, 20 µg/ml) and forfenicol (1, 20 µg/ml) for 24 h and 48 h, and acquired cross-resistance to human therapeutic antibiotics was measured by determining the increase in MIC values. MICs of ampicillin, tetracycline, nalidixic acid, and meropenem against Salmonella and Klebsiella were in the range of 20–1000 µg/ml, 5–62.5 µg/ml, 5–125 µg/ml, and 0.05–0.1 µg/ml, respectively, whereas MICs against Staphylococcus and Listeria were 2.5–10 µg/ml, 2.5 µg/ml, 62.5–500 µg/ml, and 0.1–0.2 µg/ml, respectively. Pre-exposure of these bacteria to a sub-inhibitory concentration of tilmicosin and forfenicol, increased cross-resistance against ampicillin, tetracycline, and nalidixic acid from 1.25- to 40-fold compared to the antibiotic unexposed bacteria with the exception of meropenem, which did not show increased resistance. This study could serve as a foundation to understand the mechanisms of acquired cross-resistance to traditional therapeutic antibiotics, and to develop strategies to alleviate such problem by using alternative antimicrobials.