AUTHOR=Punchihewage-Don Anuradha Jeewantha , Schwarz Jurgen , Diria Abdirahman , Bowers John , Parveen Salina 

TITLE=Prevalence and antibiotic resistance of Salmonella in organic and non-organic chickens on the Eastern Shore of Maryland, USA

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1272892

DOI=10.3389/fmicb.2023.1272892

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p><italic>Salmonella</italic> infections have been intensely increasing and becoming a universal public health crisis. This study investigated the prevalence of <italic>Salmonella</italic> in organic and non-organic chickens and the antimicrobial resistance profiles and virulence genes (<italic>inv</italic>A, <italic>pag</italic>C, and <italic>spv</italic>C) in recovered <italic>Salmonella</italic> isolates.</p></sec><sec><title>Methods</title><p>Whole chicken carcasses [organic (<italic>n</italic> = 240) and non-organic (<italic>n</italic> = 240)] were obtained monthly for 1 year (<italic>n</italic> = 480) from a retail store on the Eastern Shore of Maryland. <italic>Salmonella</italic> isolation and identification were conducted by following the whole carcass enrichment method recommended by USDA-FSIS. Confirmed <italic>Salmonella</italic> isolates (organic <italic>n</italic> = 76; non-organic <italic>n</italic> = 137) were serotyped and tested for antibiotic susceptibility and virulence genes using standard methods.</p></sec><sec><title>Results</title><p>Forty-nine percent (237/480) of the carcasses were positive for <italic>Salmonella</italic>. Organic and non-organic positivity rates were 37.1 and 61.8%, respectively. A significantly higher <italic>Salmonella</italic> contamination was observed in non-organic chickens (<italic>p</italic> &lt; 0.05). The most common serovars were <italic>Salmonella</italic> Kentucky (47%), <italic>S. Infantis</italic> (35%), <italic>S</italic>. Enteritidis (6%), <italic>S</italic>. <italic>Typhimurium</italic> (5%), and <italic>S</italic>. Blockley (4%). Isolates were frequently resistant to at least one antibiotic (91.24%) or multidrug resistant (45.54%). Resistance was observed to tetracycline (82.8%), minocycline (42.3%), nitrofurantoin (40.3%), cefazolin (38.3%), ampicillin (32.1%), and ceftriaxone (26%). All isolates were susceptible to fluoroquinolone, carbapenem, and glycylcycline. The majority of isolates (99.1%) possessed at least one of three virulence genes of concern and 4.2% tested positive for all three. Ninety-five, 89, and 6.6% of isolates contained <italic>inv</italic>A, <italic>pag</italic>C, and <italic>spv</italic>C genes, respectively. The <italic>spv</italic>C gene was not detected in serovars recovered from organic chickens though 92% and 82% of isolates were positive for <italic>inv</italic>A and <italic>pag</italic>C. The frequency of <italic>Salmonella</italic> recovered from non-organic chickens possessing <italic>inv</italic>A, <italic>pag</italic>C, and <italic>spv</italic>C genes were 97.1, 89.8, and 10.2%, respectively. Detection of <italic>inv</italic>A and <italic>pag</italic>C genes showed no significant difference (<italic>p</italic> &gt; 0.05) between organic and non-organic chickens but a significantly higher <italic>spv</italic>C gene (<italic>p</italic> &lt; 0.05) was detected in non-organic chickens due to the majority of <italic>S</italic>. Enteritidis (92.3%) exclusively recovered from non-organic chicken carried <italic>spv</italic>C gene.</p></sec><sec><title>Discussion</title><p>This study reveals a high prevalence of <italic>Salmonella</italic> in both organic and non-organic chickens, which exhibit resistance to vital antibiotics and carry virulence genes, thereby creating a potential risk of salmonellosis.</p></sec>