To study the drug sensitivity and biofilm forming ability of Listeria monocytogenes isolated from instant delicatessen meats in Chaoyang District, Beijing.

A total of 41 strains of Listeria monocytogenes isolated from instant delicatessen meats were collected. Serotyping was performed by combining polymerase chain reaction (PCR) with serum agglutination. Drug sensitivity tests were conducted using the micro-broth dilution method, and the biofilm forming ability and genes related to biofilm formation were detected by 96-well plate crystal violet staining and PCR.

Listeria monocytogenes was classified into 4 kinds of serotypes: 1/2a serotype 46.34% (19/41), 1/2b serotype 29.27% (12/41), 1/2c serotype 21.95% (9/41) and 4b serotype 2.44% (1/41). The resistant rates of erythromycin, tetracycline, penicillin, gentamicin, vancomycin were 9.76%, 7.32%, 4.88%, 4.88%, 2.44%. No resistant strains to ampicillin, ciprofloxacin and chloramphenicol were detected. The 90.24% (37/41) of the tested strains exhibited biofilm-forming capacity, among which weak, moderate and strong biofilm-forming isolates accounted for 70.73% (29/41), 14.63% (6/41) and 4.88% (2/41), respectively. All drug-resistant strains exhibited biofilm-forming ability. The positive rates of flaA, degU, motB, sigB, yneA, agrA, relA, luxS, bapL were 100.00% (41/41), 97.56%(40/41), 97.56% (40/41), 95.12% (39/41), 95.12% (39/41), 92.68% (38/41), 92.68% (38/41), 87.80% (36/41) and 41.46% (17/41). The distribution of agrA differed significantly among strains with varying biofilm-forming abilities(P<0.05), and strains with stronger biofilm-forming capacity showed a higher carriage rate of agrA.

Listeria monocytogenes isolates from instant delicatessen meats in Chaoyang District, Beijing is predominantly 1/2a serotype. Drug-resistant strains with biofilm-forming capacity are identified, which may increase the risk of persistent contamination by drug resistant strains.