Molecular typing, serotyping and cytotoxicity testing of Campylobacter jejuni strains isolated from commercial broilers in Puerto Rico


Omar A. Oyarzabal, 260 Lem Morrison Dr., Department of Poultry Science, Auburn University, AL 36849, USA. E-mail:


Aims:  Thirty Campylobacter jejuni strains isolated from fecal samples (= 94; 32%) from 13 positive farms (n = 17; 76%) from commercial broiler chickens in Puerto Rico were analysed by molecular methods.

Methods and Results:  Isolates were identified with multiplex polymerase chain reaction assays, tested for their antimicrobial susceptibility and characterized with pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), serotyping and bacterial cytotoxicity in mammalian cells. Isolates exhibited high resistance to vancomycin (minimum inhibitory concentration, MIC of >256 μg ml−1) and trimethoprim (MIC of >32 μg ml−1); few were resistant to clindamycin (MIC90 4 μg ml−1), erythromycin (MIC90 8 μg ml−1) and tetracycline (MIC90 8 μg ml−1); but none was resistant to azithromycin (MIC90 4 μg ml−1), ciprofloxacin (MIC90 1 μg ml−1) or gentamycin (MIC90 4 μg ml−1). Most strains restricted with SmaI, but a combination of SmaI–KpnI digestion was more discriminatory. MLST analysis yielded four sequence types (ST), and ST-2624 was the predominant one. Phylogenetic analysis revealed a high degree of recombination for glnA and pgm genes. The predominant serotypes were O:3 and O:5. Most strains had lowest cytotoxicity potential with Caco-2 cells, medium cytotoxicity with INT-407 and Hep-2 cells and high cytotoxicity with CHO cells.

Conclusion:  A low degree of antimicrobial resistance, 13 PFGE profiles, 4 ST and a large variability in cytotoxicity assays were found for these strains.

Significance and Impact of the Study:  This is the first characterization of C. jejuni strains isolated from broilers in Puerto Rico. The genetic diversity of these strains suggests that several techniques are needed for strain characterization.