Assessment of sensitivity to ampicillin, erythromycin and clindamycin in isolates of Lactobacillus crispatus originated from the digestive tract of domestic chickens in southwest Iran and detection of antibiotic resistance genes

Abstract

Introduction: Lactobacillus crispatus is one of the species that plays an important role in
the intestinal health of animals, especially in chicken and turkey. This bacterial isolate is one
of the desirable lactic acid strains used in probiotic formulations used by humans and farm
animals. L. crispatus, like other commensal bacteria of the gastrointestinal tract, can become
a reservoir and carrier of antibiotic resistance genes due to the improper use of antibiotics in
the poultry industry and transfer these genes to pathogenic bacteria. Therefore, it is
necessary to monitor and control the determinants of antibiotic resistance to confirm the
safety status of isolates originating from the digestive system of living animals.
Materials & methods: In this study, the resistance of three isolates of L. crispatus
originated from the digestive system of domestic chickens in the southwest of Iran to the
antibiotics ampicillin, erythromycin, and clindamycin was investigated by broth
microdilution method, and then the resistance genes in Isolates with resistance to the
investigated antibiotic were detected by the polymerase chain reaction (PCR) method.
Results: In this study, L. crispatus ABRIIN34 isolate was phenotypically resistant to the
three studied antibiotics, and L. crispatus ABRIIN32 isolate showed resistance to
clindamycin. The detection of antibiotic resistance genes by PCR method confirmed the
presence of erm(B) and ere(B) resistance genes in the plasmid DNA of L. crispatus
ABRIIN34 isolate. Also, the presence of the ampicillin resistance gene (bla) in the plasmid
DNA of this isolate was confirmed. However, the presence of a clindamycin resistance gene
was not observed in isolates with resistance to this antibiotic.
Conclusion: The findings of this study provide insight into antibiotic resistance in probiotic
microorganisms with an emphasis on resistance to ampicillin, erythromycin, and
clindamycin. The results of this study determined that antibiotic resistance genes are
scattered among the native bacteria of the digestive tract and this must be taken into
consideration when choosing probiotic bacteria.