ABSTRACT
Background & objectives: Pediococcus pentosaceus has been reported to cause clinical infections while it is being promoted as probiotic in food formulations. Antibiotic resistance (AR) genes in this species are a matter of concern for treating clinical infections. The present study was aimed at understanding the phenotypic resistance of P. pentosaceus to macrolide-lincosamide-streptogramin B (MLSB) antibiotics and the transfer of AR to pathogens. Methods: P. pentosacues isolates (n=15) recovered from fermented foods were screened for phenotypic resistance to MLSBantibiotics using disc diffusion and microbroth dilution methods. Localization and transferability of the identified resistance genes, erm(B) and msr(C) were evaluated through Southern hybridization and in vitro conjugation methods. Results: Four different phenotypes; sensitive (S) (n=5), macrolide (M) (n=7), lincosamide (L) (n=2) and constitutive (cMLSB) (n=1) were observed among the 15 P. pentosaceus isolates. High-level resistance (>256 ?g/ml) to MLSBwas observed with one cMLSBphenotypic isolate IB6-2A. Intermediate resistance (8-16 ?g/ml) to macrolides and lincosamides was observed among M and L phenotype isolates, respectively. Cultures with S phenotype were susceptible to all other antibiotics but showed unusual minimum inhibitory concentration (MIC) values of 8-16 ?g/ml for azithromycin. Southern hybridization studies revealed that resistance genes localized on the plasmids could be conjugally transferred to Enterococcus faecalis JH2-2. Interpretation & conclusions: The study provides insights into the emerging novel resistance patterns in P. pentosaceus and their ability to disseminate AR. Monitoring their resistance phenotypes before use of MLS antibiotics can help in successful treatment of Pediococcal infections in humans.
ABSTRACT
Background & objectives: Bacterial biofilms a multi-layered defence, comprise extracellular DNA (eDNA) and proteins, protect bacteria from harmful environment and nutrient limitation and utilize the mutual benefits within a community. Bacterial biofilms also defend bacteria from harsh environments such as antibiotic treatment. This leads to poor antibiotic penetration, slow growth, adaptive stress responses, and formation of persister cells. This study was done to determine the relation of antibiotic resistance deciphered by the biofilms in Lactobacillus plantarum, a lactic acid bacteria (LAB) with probiotic significance. Methods: The gentamicin-resistant L. plantarum isolates were allowed to form biofilms and subjected to DNase I and proteinase K treatment. The optical density (OD) values were recorded for the biofilm assay and the cell count for the number of viable cells was taken for the control and the test samples. Percentage reduction was calculated based on the difference between the initial and final OD for both the parameters. Results: The biofilm assay revealed that the native L. plantarum isolates which were phenotypically susceptible, possessed the ability to form biofilms. The OD values were significantly decreased in comparison to the biofilm-forming control culture when these were treated with DNase I and proteinase K. Interpretation & conclusions: The study revealed that the biofilms formed by L. plantarum comprised of eDNA and proteins which was evidenced by the reduction in OD values and percentage in comparison to the control upon DNase I and proteinase K treatment. This indicates that the eDNA and biofilm matrix proteins are vital constituents of biofilms and may carry significant risk when coupled with antibiotic resistance.