Antimicrobial susceptibility and presence of resistance genes in staphylococci from poultry

The species distribution, susceptibility to 19 antimicrobial agents and pre sence of selected genes encoding resistance to macrolides, streptogramins a nd tetracyclines were examined among 118 staphylococcal isolates from infec tions of poultry in Denmark. Isolates were identified using a combination o f conventional biochemical testing and 16S rDNA sequencing. The most common species were Staphylococcus aureus (83), Staphylococcus hyicus (11), Staph ylococcus xylosus (9) and Staphylococcus cohnii (6). The isolates were susc eptible to most antimicrobials tested. A high frequency of S. aureus (30%) was resistant to ciprofloxacin. Only six (7%) S. aureus isolates and one St aphylococcus saprophyticus were penicillin resistant. Resistance to sulpham ethoxazole was observed among 16 (19%) of S. aureus isolates and two coagul ase negative staphylococci (CNS). Twenty (24%) of the S. aureus isolates we re resistant to erythromycin and 19 of these isolates contained the ermA ge ne, whereas the remaining isolate contained the ermC gene. Eleven (48%) of the novobiocin resistant CNS were resistant to erythromycin and all these i solates contained the ermA gene. Two isolates identified as S. xylosus, wer e found to be resistant to streptogramins and both contained the vatB- and the vgaB-genes. Thirty-nine (47%) of the S. aureus isolates, three of nine S. hyicus and eight of the 23 novobiocin resistant CNS were tetracycline re sistant and all contained the tct(K) gene. A single S. aureus isolate also contained the tet(M) gene. The present study showed a frequent occurrence o f resistance to fluoroquinolones, tetracycline and macrolides among staphyl ococci isolated from broilers in Denmark, whereas the occurrence of resista nce to other antimicrobial agents remains low. Similar genes, encoding resi stance to erythromycin, tetracycline and streptogramins to those previously observed, were detected. (C) 2000 Elsevier Science B.V. All rights reserve d.