High throughput Luminex beads based multiplex assay for identification of six major bacterial pathogens of mastitis in dairy animals.

Introduction: Bovine mastitis is caused by over 150 different microorganisms. Specific identification and quantification of multiple bacteria in a single milk sample becomes essential for rapid intervention. Methods: In the present study a Luminex beads based multiplex assay emphasizing on the precise identification of six major bacterial pathogens of mastitis was developed. Assay was developed in two triplex sets, triplex 1 comprised of Streptococcus agalactiae, Streptococcus dysgalactiae and Streptococcus uberis while triplex 2 consisted of Staphylococcus aureus, E. coli and Klebsiella pneumoniae. Results: The analytical sensitivity was 10 6 copies per reaction mixture for all the six bacteria. A 100% analytical specificity was observed for simultaneous detection of these bacteria. Clinical milk samples from 100 bovine quarters were tested for validation. Discussion: The analytical sensitivity was similar to the findings reported earlier in real time PCR multiplex assay targeting the DNA of the 11 most common bacterial species or groups in mastitis. The analytical specificity of the optimized assay was 100% similar to reported earlier for simultaneous detection of Mycoplasma spp. and for seven entric viruses of humans.The developed assay indicates a concept proof of a rapid, cost effective high throughput diagnostic tool for identification of major bacteria causing mastitis.

Development and evaluation of a gold nanoparticle based Lateral Flow assay (LFA) strip test for detection of Brucella spp.

The widely used serodiagnostic test (RBPT, CFT, I-ELISA and FPA) for diagnosis of brucellosis cannot detect vertically infected or carrier animals that are seronegative, a persistent source of infection to other susceptible animals in the herd. For reducing transmission of disease within the herd, these animals must be detected using a rapid, sensitive, user friendly penside diagnostic test. In the present study, Lateral Flow immunoassay (LFA) strip test was developed for detection of Brucellaspp. from clinical samples (bovine aborted foetal stomach contents). The LFA strip was fabricated by printing anti-Brucella polyclonal antibodies (PAb) and anti-bovine antibodies IgG on test and control line, respectively. For conjugation, colloidal gold nanoparticles (30 nm GNP, Sigma, USA) were conjugated with anti-brucella PAb. The LFA strip test was able to detect 107 cfu/ml B.abortus S99 inactivated organism in PBS and it did not exhibit any cross reactivity with selected non Brucella pathogens. To further validate, 115 clinical specimens were tested using LFA strip test. The relative sensitivity (DSn) and relative specificity (DSp) of LFA strip test was determined by ROC curve analysis using PCR and culture method as reference standard. DSn and DSp of LFA strip test was observed as 78.57% (95%CI: 49.2-95.3); 93.07% (95%CI: 86.2-97.2) and 80.0% (95%CI:51.9-95.7); 94.0% (95%CI:0.795-0.925) using culture and PCR as reference diagnostic tests, respectively. It may be concluded that, the LFA strip test can be used as a rapid penside diagnostic test for screening of brucellosis. To the best of our knowledge, this is the first report on development of GNP based LFA strip test for detection of Brucella spp. from bovine aborted fetal content samples.

Draft genome sequence of field isolate Brucella melitensis strain 2007BM/1 from India.

OBJECTIVES: Brucellosis is among one of the most widespread important global zoonotic diseases that is endemic in many parts of India. Brucella melitensis is supposed to be the most pathogenic species for humans. Here we report the draft genome sequence of B. melitensis strain 2007BM/1 isolated from a human in India. METHODS: Genomic DNA was extracted from Brucella culture and was sequenced using an Illumina MiSeq platform. The generated reads were assembled using three de novo assemblers and the draft genome was annotated. RESULTS: This monoisolate, with a genome length of 3268756bp, was found to be resistant to azithromycin and trimethoprim/sulfamethoxazole but susceptible to tetracycline, ofloxacin, rifampicin, ciprofloxacin and doxycycline. The presence of virulence genes in the strain was identified. CONCLUSIONS: The results obtained will help in understanding drug resistance mechanisms and virulence factors in highly zoonotic B. melitensis and suggest the need for judicious use of antibiotics in livestock health and management practices.