[Enumeration and antimicrobial resistance of Campylobacter species from retail chicken carcasses]

To determine Campylobacter contamination level and antimicrobial resistance patterns from chicken carcasses in supermarkets and farmer's markets of 9 districts in Beijing.

From August 2012 to July 2013, whole chicken carcasses (n = 240) were collected from 27 supermarkets and 18 farmer's markets of nine districts in Beijing. The level of Campylobacter contamination was enumerated by plate counting method using the modified Karmali and modified Preston agar. Presumptive Campylobacter isolates were identified and characterized by gram stain, agglumination test and a multiplex PCR method. The level of Campylobacter contamination was calculated following the USDA/FSIS Campylobacter enumeration method. Selected 151 Campylobacter isolates were further characterized by minimal inhibitory concentrations(MICs) of eight antimicrobials.

A total of 26.3% (63/240) of the retail whole chicken carcasses were contaminated by Campylobacter and 151 Campylobacter isolates were recovered, including 85 Campylobacter jejuni isolates and 66 Campylobacter coli isolates. The P25, P50, P75 of Campylobacter contamination concentration were 7.5, 45.0 and 350.0 CFU/g, respectively. The antimicrobial resistance rate of C. jejuni and C. coli were as the following: azithromycin(AZI, 13% (11/85), 82% (54/85)), chloramphenicol (CHL, 33% (28/85), 42% (28/85)), ciprofloxacin (CIP, 95% (81/85), 100% (85/85)), doxycycline (DOX, 38% (32/85), 80% (53/85)), erythromycin (ERY, 12% (10/85), 82% (54/85)), gentamicin (GEN, 25% (21/85), 68% (45/85)), tetracycline (TET, 67% (57/85), 73% (62/85)), all isolates were susceptible to meropenem (MEP). The multi-drug resistance ratio of C. jejuni (55% (47/85) )was significantly lower than that (86% (57/66) )of C. coli (χ(2) = 16.70, P < 0.01). Among 151 Campylobacter isolates, 21 antimicrobial resistance patterns were identified, including 20 patterns among C. jejuni isolates and 10 patterns among C.coli isolates. Among C.jejuni isolates, CIP-DOX-TET was dominant (22% (19/85)), followed by CIP-TET (14% (12/85)), CHL-CIP-TET(9% (8/85)) and CHL-CIP-GEN (7% (6/85)). Among C.coli isolates,AZI-CHL-CIP-DOX-ERY-GEN-TET (35% (23/66)) was the dominant, followed by AZI-CIP-DOX-ERY-GEN-TET (21% (14/66) )and AZI-CIP-DOX-ERY-TET(15% (10/66)).

Our findings showed a high prevalence and concentration of Campylobacter contamination in retail chicken carcasses of nine districts in Beijing, especially the on-site slaughtered chicken from the farmer's markets. The resistance levels of these recovered Campylobacter isolates were serious.