Biomedical subjects

Bhushan M Jayarao

Publications and source records attributed to Bhushan M Jayarao.

6 recordsLinked to original sources

PubMed2006

Antimicrobial-resistant enteric bacteria from dairy cattle.

A study was conducted to understand the descriptive and molecular epidemiology of antimicrobial-resistant gram-negative enteric bacteria in the feces of healthy lactating dairy cattle. Gram-negative enteric bacteria resistant to ampicillin, florfenicol, spectinomycin, and tetracycline were isolated from the feces of 35, 8, 5, and 42% of 213 lactating cattle on 74, 39, 9, 26, and 82% of 23 farms surveyed, respectively. Antimicrobial-resistant gram-negative bacteria accounted for 5 (florfenicol) to 14% (tetracycline) of total gram-negative enteric microflora. Nine bacterial species were isolated, of which Escherichia coli (87%) was the most predominant species. MICs showing reduced susceptibility to ampicillin, ceftiofur, chloramphenicol, florfenicol, spectinomycin, streptomycin, and tetracycline were observed in E. coli isolates. Isolates exhibited resistance to ampicillin (48%), ceftiofur (11%), chloramphenicol (20%), florfenicol (78%), spectinomycin (18%), and tetracycline (93%). Multidrug resistance (> or =3 to 6 antimicrobials) was seen in 40% of E. coli isolates from healthy lactating cattle. Of 113 tetracycline-resistant E. coli isolates, tet(B) was the predominant resistance determinant and was detected in 93% of isolates, while the remaining 7% isolates carried the tet(A) determinant. DNA-DNA hybridization assays revealed that tet determinants were located on the chromosome. Pulsed-field gel electrophoresis revealed that tetracycline-resistant E. coli isolates (n = 99 isolates) belonged to 60 subtypes, which is suggestive of a highly diverse population of tetracycline-resistant organisms. On most occasions, E. coli subtypes, although shared between cows within the herd, were confined mostly to a dairy herd. The findings of this study suggest that commensal enteric E. coli from healthy lactating cattle can be an important reservoir for tetracycline and perhaps other antimicrobial resistance determinants.

Animals↗

PubMed2006

Molecular epidemiology of ceftiofur-resistant Escherichia coli isolates from dairy calves.

Healthy calves (n = 96, 1 to 9 weeks old) from a dairy herd in central Pennsylvania were examined each month over a five-month period for fecal shedding of ceftiofur-resistant gram-negative bacteria. Ceftiofur-resistant Escherichia coli isolates (n = 122) were characterized by antimicrobial resistance (disk diffusion and MIC), serotype, pulsed-field gel electrophoresis subtypes, beta-lactamase genes, and virulence genes. Antibiotic disk diffusion assays showed that the isolates were resistant to ampicillin (100%), ceftiofur (100%), chloramphenicol (94%), florfenicol (93%), gentamicin (89%), spectinomycin (72%), tetracycline (98%), ticarcillin (99%), and ticarcillin-clavulanic acid (99%). All isolates were multidrug resistant and displayed elevated MICs. The E. coli isolates belonged to 42 serotypes, of which O8:H25 was the predominant serotype (49.2%). Pulsed-field gel electrophoresis classified the E. coli isolates into 27 profiles. Cluster analysis showed that 77 isolates (63.1%) belonged to one unique group. The prevalence of pathogenic E. coli was low (8%). A total of 117 ceftiofur-resistant E. coli isolates (96%) possessed the bla(CMY2) gene. Based on phenotypic and genotypic characterization, the ceftiofur-resistant E. coli isolates belonged to 59 clonal types. There was no significant relationship between calf age and clonal type. The findings of this study revealed that healthy dairy calves were rapidly colonized by antibiotic-resistant strains of E. coli shortly after birth. The high prevalence of multidrug-resistant nonpathogenic E. coli in calves could be a significant source of resistance genes to other bacteria that share the same environment.

Animals↗

PubMed2005

Dissemination of Salmonella enterica subsp. enterica Serovar Typhimurium var. Copenhagen clonal types through a contract heifer-raising operation.

Salmonella enterica subsp. enterica serovar Typhimurium var. Copenhagen isolates from a heifer-raising operation and from 11 dairy herds that had their calves contracted to the heifer-raising operation were examined for their phenotypic and genotypic characteristics. Results of the study showed that the heifer-raising operation could serve as a clearinghouse for Salmonella serovar Typhimurium var. Copenhagen and perhaps other Salmonella serotypes.

Animals↗

PubMed2004

Multi-virulence-locus sequence typing of Listeria monocytogenes.

A multi-virulence-locus sequence typing (MVLST) scheme was developed for subtyping Listeria monocytogenes, and the results obtained using this scheme were compared to those of pulsed-field gel electrophoresis (PFGE) and the published results of other typing methods, including ribotyping (RT) and multilocus sequence typing (MLST). A set of 28 strains (eight different serotypes and three known genetic lineages) of L. monocytogenes was selected from a strain collection (n > 1,000 strains) to represent the genetic diversity of this species. Internal fragments (ca. 418 to 469 bp) of three virulence genes (prfA, inlB, and inlC) and three virulence-associated genes (dal, lisR, and clpP) were sequenced and analyzed. Multiple DNA sequence alignment identified 10 (prfA), 19 (inlB), 13 (dal), 10 (lisR), 17 (inlC), and 16 (clpP) allelic types and a total of 28 unique sequence types. Comparison of MVLST with automated EcoRI-RT and PFGE with ApaI enzymatic digestion showed that MVLST was able to differentiate strains that were indistinguishable by RT (13 ribotypes; discrimination index = 0.921) or PFGE (22 profiles; discrimination index = 0.970). Comparison of MVLST with housekeeping-gene-based MLST analysis showed that MVLST provided higher discriminatory power for serotype 1/2a and 4b strains than MLST. Cluster analysis based on the intragenic sequences of the selected virulence genes indicated a strain phylogeny closely related to serotypes and genetic lineages. In conclusion, MVLST may improve the discriminatory power of MLST and provide a convenient tool for studying the local epidemiology of L. monocytogenes.

Amino Acid Sequence↗

PubMed2003

Bulk-tank milk analysis. A useful tool for improving milk quality and herd udder health.

Bulk-tank milk (BTM) analysis is now widely accepted as a useful tool for evaluating milk quality and monitoring udder-health status in a herd. Bacterial and somatic cell count (SCC) estimation of BTM, when done repeatedly over a period of time, can become a significant knowledge base. When interpreted within the context of the farm's management practices, this information provides a basis for evaluating current and potential milk quality and mastitis problems in a herd. This article describes the process of using BTM analysis to make decisions on improving milk quality and herd udder health. It should be kept in mind that although individual cow samples for milk culture and SCC are more definitive for diagnosis and monitoring of udder health, BTM analysis is less expensive, more convenient, and faster than testing milk samples from individual animals or groups of cows.

Animals↗

PubMed2002

Evaluation of five selective media for isolation of catalase-negative gram-positive cocci from bulk tank milk.

Five selective media including Edwards modified medium, Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L), Streptococcus selective medium, Streptosel agar, and thallium-crystal violet-toxin-ferric citrate medium were evaluated for the isolation of streptococci and streptococci-like organisms from raw milk. The sensitivity and specificity of these selective media for streptococci and streptococci-like organisms were determined by using American Type Culture Collection reference strains. Under experimental conditions Edwards modified medium with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) showed the highest sensitivity (100%) and specificity (100%) for streptococci and streptococci-like organisms followed by thallium-crystal violettoxin-ferric citrate medium, Edwards modified medium, Streptococcus selective medium, and Streptosel agar. Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) allowed growth of all streptococci and streptococci-like organisms, while inhibiting growth of the staphylococci and gram-negative reference strains. Bulk tank milk samples from 114 dairy herds were spiral plated onto Edwards modified medium with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L). A total of 344 isolates (at least three isolates from each sample) were randomly selected and identified to their species. This medium permitted growth of 328 streptococci and streptococci-like organisms belonging to genera Aerococcus, Enterococcus, Gemella, Lactococcus, Streptococcus, and Vagococcus. When Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) was evaluated using bulk tank milk samples, the sensitivity and specificity of this medium for streptococci and streptococci-like organisms were observed to be 100 and 87.5%, respectively. The positive predictive value for streptococci and streptococci-like organisms was observed to be 99.4%. The results of the study indicate that Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) can be used as a selective medium for the isolation of streptococci and streptococci-like organisms from bulk tank milk.

Animals↗