STUDIES ON BIOFILM FORMING BACTERIAL PATHOGENS OF BOVINE MASTITIS
| dc.contributor.advisor | Ramani Pushpa, R.N(Major) | |
| dc.contributor.advisor | Subramanyam, K.V | |
| dc.contributor.advisor | Srinivasa Rao, T | |
| dc.contributor.author | SATISH KUMAR, DONTAM | |
| dc.date.accessioned | 2017-08-17T07:25:20Z | |
| dc.date.available | 2017-08-17T07:25:20Z | |
| dc.date.issued | 2016-12 | |
| dc.description | THESES | en_US |
| dc.description.abstract | ABSTRACT: Bovine mastitis is the most common infectious diseases of dairy cattle which is economically important in dairy industry all over the world. The main etiological agents causing bovine mastitis are Staphylococcus aureus, Streptococcus agalactiae and Escherichia coli. Antimicrobial therapy is commonly implemented for mastitis prevention and control. Restriction of antimicrobial agents gaining access to the pathogens due to the impervious nature of the biofilm encased extracellular matrix, plays a pivotal role in biofilm antimicrobial resistance. Hence, the present study was undertaken to study the prevalence of biofilm forming bacteria involved in bovine mastitis and evaluation of their antibiogram profile. A total of 81 mastitis milk samples were investigated in the present study. Out of these, 67 (82.7%) samples were positive. No pathogens were isolated from 14 (17.3%) milk samples. A total of 95 organisms were recovered. Staphylococcus species (46.9%) was the predominant bacteria isolated followed by E. coli (33.3%), Streptococcus species (29.6%), Pseudomonas species (6.17%) and Listeria monocytogenes (1.23%).All 38 isolates of Staphylococcus spp. and 24 isolates of Streptococcus species were confirmed using genus specific primers. Whereas, 27 isolates of E. coli, 17 isolates of S. aureus, 12 isolates of Streptococcus uberis, 6 isolates of S. agalactiae, 4 isolates of Streptococcus dysgalactiae and one isolate of Listeria monocytogenes were confirmed using species specific oligonucleotide primers.The antibiogram profile indicated that Staphylococcus species, E. coli and Streptococcus species showed highest resistance to ampicillin, penicillin-G and ceftriaxone+ sulbactum followed by enrofloxacin, tetracycline and oxacillin and had least resistance to amoxicillin+ clavulanic acid and gentamicin. Whereas, the antibiogram of biofilm producing bacterial pathogens revealed more resistance to antibiotics used in the present study when compared to nonbiofilm producers.The MIC of Staphylococcus isolates ranged from 7.81- 0.49 μg/ml for enrofloxacin, 0.49- 7.81 μg/ml for gentamicin, 0.49- 31.25 μg/ml for amoxicillin, 0.49- 125 μg/ml penicillin-G, 3.9- 1000 μg/ml for oxacillin and 0.49- 31.25 μg/ml for ceftriaxone. The observed MIC of E. coli isolates ranged from 0.49- 31.25 μg/ml for gentamicin, 0.49- 125 μg/ml for amoxicillin, 3.9- 1000 μg/ml for penicillin-G, 0.49- 250 μg/ml for nalidixic acid and 0.49- 1.95 μg/ml for ceftriaxone. All isolates of E. coli were inhibited at a concentration of 0.49 μg/ml for enrofloxacin.The genotypic antibiotic profile of E. coli and Staphylococcus species was investigated. Among the 38 isolates of Staphylococcus species, 33 (86.8%) and 28 (73.7%) were carrying mecA and blaZ genes respectively. Both mecA and blaZ genes were found in 25 (65.8%) isolates of Staphylococcus species. Out of 17 isolates of S. aureus, mecA and blaZ genes were detected in 13 (76.5%) isolates each respectively. Both mecA and blaZ genes were found in 10 (58.8%) isolates of S. aureus. Tetracycline resistance genes were found in 74.07% of E. coli isolates in the present study. Among tetracycline resistance genes, tetB was found in higher frequency of 51.8%, and tetA was found in 48.1%. Whereas 25.9% isolates carried both tetA and tetB genes. None of the E. coli isolate was positive for quinolones gene.The biofilm formation of bacterial isolates was detected by using congo red agar method (CRA), microtitre plate assay (MTPA) and polymerase chain reaction (PCR). In E. coli, the frequency of biofilm producers was 66.7% when identified by CRA method, while it was 77.7% using MTPA method and by PCR, 88.8% of isolates were positive for biofilm gene (luxS). Out of 38 isolates of Staphylococcus species, 17 (44.7%) were producing biofilm by CRA method, 35 (92.1%) by MTPA. icaA and icaD genes responsible for biofilm formation in S. aureus were detected in three (17.6%) and seven (41.2%) of S. aureus isolates respectively. Two (11.76%) strains of S. aureus carried both icaA and icaD genes. None of the Staphylococcus isolates were positive to icaBC and bap genes. Out of 24 Streptococcus isolates, 12 (50%) were positive for biofilm production by CRA method, whereas 19 (79.2%) by MTPA method. Among 12 S. uberis isolates, biofilm formation was detected in 10 (83.3%) by CRA method, all 12 isolates were biofilm producers by MTPA method and the luxS gene responsible for biofilm production was detected in five (41.7%) isolates.The results of nucleotide sequences of biofilm genes of S. aureus (icaD), E. coli (luxS) and S. uberis (luxS) when blasted with reference strains in NCBI database revealed 98%, 100% and 100% homology respectively. | en_US |
| dc.identifier.uri | http://krishikosh.egranth.ac.in/handle/1/5810028800 | |
| dc.keywords | BIOFILM FORMING; BACTERIAL PATHOGENS; BOVINE MASTITIS | en_US |
| dc.language.iso | en | en_US |
| dc.pages | 190 | en_US |
| dc.publisher | SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI – 517 502. (A.P) INDIA | en_US |
| dc.sub | Veterinary Microbiology | en_US |
| dc.subject | null | en_US |
| dc.theme | STUDIES ON BIOFILM FORMING BACTERIAL PATHOGENS OF BOVINE MASTITIS | en_US |
| dc.these.type | M.V.Sc. | en_US |
| dc.title | STUDIES ON BIOFILM FORMING BACTERIAL PATHOGENS OF BOVINE MASTITIS | en_US |
| dc.type | Thesis | en_US |