The occurrence of Salmonella, extended-spectrum β-lactamase producing Escherichia coli and carbapenem resistant non-fermenting Gram-negative bacteria in a backyard poultry flock environment

Abstract

Increase in the number of small-scale backyard poultry flocks in the USA has substantially increased human-to-live poultry contact, leading to increased public health risks of the transmission of multi-drug resistant (MDR) zoonotic and food-borne bacteria. The objective of this study was to detect the occurrence of Salmonella and MDR Gram-negative bacteria (GNB) in the backyard poultry flock environment. A total of 34 backyard poultry flocks in Washington State (WA) were sampled. From each flock, one composite coop sample and three drag swabs from nest floor, waterer-feeder, and a random site with visible faecal smearing, respectively, were collected. The samples were processed for isolation of Salmonella and other fermenting and non-fermenting GNB under ceftiofur selection. Each isolate was identified to species level using MALDI-TOFF and tested for resistance against 16 antibiotics belonging to eight antibiotic classes. Salmonella serovar 1,4,[5],12:i:- was isolated from one (3%) out of 34 flocks. Additionally, a total of 133 ceftiofur resistant (Cef^R ) GNB including Escherichia coli (53), Acinetobacter spp. (45), Pseudomonas spp. (22), Achromobacter spp. (8), Bordetella trematum (1), Hafnia alvei (1), Ochrobactrum intermedium (1), Raoultella ornithinolytica (1), and Stenotrophomonas maltophilia (1) were isolated. Of these, 110 (82%) isolates displayed MDR. Each flock was found positive for the presence of one or more Cef^R GNB. Several MDR E. coli (n = 15) were identified as extended-spectrum β-lactamase (ESBL) positive. Carbapenem resistance was detected in non-fermenting GNB including Acinetobacter spp. (n = 20), Pseudomonas spp. (n = 11) and Stenotrophomonas maltophila (n = 1). ESBL positive E. coli and carbapenem resistant non-fermenting GNB are widespread in the backyard poultry flock environment in WA State. These GNB are known to cause opportunistic infections, especially in immunocompromised hosts. Better understanding of the ecology and epidemiology of these GNB in the backyard poultry flock settings is needed to identify potential risks of transmission to people in proximity.

Keywords: Achromobacter; Acinetobacter; E. coli; Pseudomonas; Salmonella; multidrug resistance; poultry.