Frequency of Resistance to Antimicrobial Agents among MRSA Strains Isolated from Broilers and ‘Pluck Shop’ Workers in Trinidad

Introduction:  Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of zoonotic infections in many countries. People with occupational contact with food producing animals are at high risk of colonization. In Trinidad, MRSA strains have been reported in cattle, humans and pigs, however, it has not been documented in broilers.

Purpose:   The aim of this study was to determine the prevalence of MRSA and the frequency of antimicrobial resistance in MRSA isolated from broilers and workers at the ‘pluck shops’ in Trinidad.

Methods: Choanal, cloacal and pharyngeal swabs taken from broilers and nasal swabs from humans were enriched in Mueller Hinton broth with 6.5% sodium chloride followed by secondary enrichment in phenol red mannitol broth with 75 mg/L aztreonam and 5 mg/L ceftizoxime. Enriched samples were plated on both CHROMagar MRSA and Brilliance MRSA. Suspect isolates were identified as Staphylococcus aureus (SA) using standard biochemical procedures, then confirmed as MRSA using the PBP2a test kit and PCR for the mecA gene. Susceptibility of MRSA isolates to 16 antimicrobial agents was detected by the disc diffusion method.

Results:  Of the 287 broilers and 47 humans sampled, MRSA was isolated from 11 (3.8%) and 1 (2.1%), respectively. All isolates were resistant to one or more of the 16 antimicrobial agents and all were susceptible to vancomycin, rifampicin and chloramphenicol. The frequency of resistance ranged from 25.0% (streptomycin) to 100% (oxacillin, penicillin and ampicillin).

Significance: The study demonstrated that slaughtered broilers and workers at ‘pluck shops’ in Trinidad harbor multidrug resistance MRSA. This is of public health significance as occupational exposure of humans can lead to an increased risk of acquiring MRSA infections.