The Relationship between Biofilm Formation and Multiple Antibiotic Resistance of Streptococcus Isolates from Bovine Milk with Mastitis
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Date
2024
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Due to the increase in multi-antibiotic resistance (MDR) among streptococci, which have the ability to colonize different surfaces and form biofilms, treatment options have begun to be limited in diseases caused by these bacteria. The success of antibacterial therapy in mastitis may be related not only to the antibiotic susceptibility of the etiological factors, but also to the biofilm formation capacity, which is one of the most important virulence factors in bacteria. The aim of this study was to investigate the relationship between biofilm production and multi-antibiotic resistance of streptococcal isolates obtained from cow's milk with mastitis. For this purpose, 71 streptococcal isolates obtained from 282 subclinical mastitis milk from 27 farms were used. After the isolates were obtained by conventional methods, polymerase chain reaction (PCR) identifications were carried out. While the biofilm forming capacities of the isolates were determined phenotypically by the microplate method (MP); resistance to nine antibiotics belonging to nine antimicrobial families was evaluated by disc diffusion tests. Isolates resistant to at least three or more antimicrobial drug classes were considered multi-antibiotic resistant (MDR). Pearson Chi-Square (χ2) test was used to examine the relationship between biofilm forming capacity of isolates and multiple antibiotic resistance. Of the 71 streptococci obtained, 42 (59.1%) were identified as S. uberis, 13 (18.3%) as S. agalactiae, 8 (11.3%) as S. parauberis and 8 (11.3%) as S. dysgalactiae. Fifty one (71.8%) of the isolates were biofilm producers. Biofilm production was found in 84.7% (11/13), 75.0% (6/8), 69.1% (29/42), and 62.5% (5/8) in S. agalactiae, S. parauberis, S. uberis and S. dysgalactiae isolates, respectively. The most common resistance was to tetracycline (70.4%), followed by clindamycin (39.4%), ampicillin and vancomycin (35.2%), erythromycin (33.8%), and cefotaxime (32.4%). While 67.6% of the isolates were susceptible to chloramphenicol, 91.5% to linezolid and levofloxacin, 43.7% were MDR. The rate of multidrug resistance was higher in S. agalactiae (84.6%) than in S. parauberis (50%), S. dysgalactiae (50%) and S. uberis (28.6%). A significant correlation was found between the biofilm forming capacity of the isolates and multiple antibiotic resistance (P=0.016). It was concluded that biofilm-forming isolates showed higher resistance to antibiotics. As a result of this study, it was determined that mastitic streptococci isolates have the ability to produce biofilms that can significantly affect the course of the disease, and significantly affect multi-antibiotic resistance. The high biofilm forming capacity of MDR streptococcal isolates (87.0%, 27/31) might designate their high pathogenic potential that may pose a threat to human health. © 2024, Israel Veterinary Medical Association. All rights reserved.