Salmonella enterica in farm environments in the Ashanti Region of Ghana

BACKGROUND: Salmonella enterica are important foodborne pathogens and the third leading cause of death among diarrheal infections worldwide. This cross-sectional study investigated the frequency of antibiotic-resistant Salmonella enterica in commercial and smallholder farm environments in the Ashanti Region of Ghana. A total of 1490 environmental samples, comprising 800 (53.7%) soil (from poultry, pigs, sheep, goats and cattle farms), 409 (27.4%) pooled poultry fecal and 281 (18.9%) dust (from poultry farms) samples, were collected from 30 commercial and 64 smallholder farms. All samples were processed using standard culture methods. Isolates were identified by biochemical methods and confirmed using the VITEK 2 System. Antibiotic susceptibility testing was carried out by disk diffusion following the EUCAST guidelines. Serotyping was performed using the Kauffman White Le Minor Scheme. RESULTS: The overall Salmonella frequency was 6.0% (n/N = 90/1490); the frequency varied according to the type of sample collected and included: 8.9% for dust (n/N = 25/281), 6.5% for soil (n/N = 52/800) and 3.2% for pooled poultry fecal samples (n/N = 13/409). Salmonella was also recovered from commercial farm environments (8.6%, n/N = 68/793) than from smallholder farms (3.2%, n/N = 22/697) (PR = 2.7, CI: 1.7 – 4.4). Thirty-four different Salmonella serovars were identified, the two most common being Rubislaw (27.8%, n/N = 25/90) and Tamale (12.2%, n/N = 11/90). Serovar diversity was highest in strains from soil samples (70.6%, n/N = 24/34) compared to those found in the dust (35.2%, n/N = 12/34) and in fecal samples (29.4%, n/N = 10/34). Salmonella frequency was much higher in the rainy season (8.4%, n/N = 85/1007) than in the dry season (1.0%, n/N = 5/483) (PR = 8.4, 95% CI: 3.3 – 20.0). Approximately 14.4% (n/N = 13/90) of the isolates were resistant to at least one of the tested antimicrobials, with 84.6% (n/N = 11/13) being resistant to multiple antibiotics. All Salmonella Kentucky (n = 5) were resistant to ciprofloxacin. CONCLUSION: This study showed that farm environments represent an important reservoir for antibiotic-resistant Salmonella, which warrants monitoring and good husbandry practices, especially in commercial farms during the rainy season, to control the spread of this pathogen.