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Abstract: |
Objective: Isolation and identification of antibiotics
resistant bacteria in raw milk. Methods: Luria-Bertani plates
containing ampicillin (32 μg/mL), clindamycin (4 μg/mL), or
chloramphenicol (32 μg/mL) were used in isolating the antibiotics
resistant bacteria from samples; 16S rRNA analysis method was
used to identify the isolates; blood agar plates were used in
hemolysis assay; K-B disk diffusion method was used to confirm
the resistant phenotypes. Results: 60 raw milk samples collected
from Zhangjiakou were screened for antibiotic resistant bacteria.
The screening results showed that 48 (80%) samples had isolates
resistant to more than one antibiotic, 39 (65%) samples had
isolates resistant to more than two antibiotics, and 14 (23.33%)
samples had isolates resistant to three antibiotics tested. Totally,
48 strains were isolated resistant to ampicillin, 46 strains were
isolated resistant to clindamycin, and 21 strains were isolated
resistant to chloramphenicol. Ten strains (resistant to three
antibiotics) were randomly selected for 16S rRNA analysis and
they were identified as Serratia marcescens (1), Pseudomonas
aeruginosa (8), and Enterobacter cloacae (1), respectively.
Hemolysis test results showed those 2 strains with α-hemolytic
phenotype, 2 strains with β-hemolytic phenotype, and 6 strains
with γ-hemolytic phenotype. Furthermore, with K-B disk
diffusion method, all 10 isolates were validated resistant to 3
antibiotics tested except that one isolate intermediated to
chloramphenicol and two isolates susceptible to chloramphenicol.
Conclusion: Raw milk is the reservoir of a variety of antibiotics
resistant bacteria; antibiotic plates can be used for preliminary
screening of antibiotics resistant bacteria from raw milk samples.
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