Identification, serotyping, and antimicrobial susceptibility of Riemerella anatipestifer isolated from ducks in Vietnam.

Background: Septicemia caused by Riemerella anatipestifer (R. anatipestifer) is a serious problem in the duck industry worldwide, and it is currently one of the major concerns for duck farming in Vietnam.. Aim: This study was conducted to identify the causative agent of septicemia in ducks in Vietnam. The antimicrobial susceptibility and serotypes of R. anatipestifer isolates were also determined to provide valuable information for disease treatment and vaccine development. Methods: Riemerella anatipestifer was isolated using blood agar and chocolate agar media. The commercial API 20NE microtest system and the partial nucleotide sequence analysis of the 16s rRNA were used to identify R. anatipestifer strains. Serotypes were determined by slide agglutination test using standard antisera against R. anatipestifer. The disk diffusion method was utilized to investigate the antimicrobial susceptibility of R. anatipestifer isolated strains. Results: A total of 408 samples were collected from ducks with typical symptoms of septicemia for R. anatipestifer isolation. Sixty-nine R. anatipestifer strains were identified. Serotyping results showed that 30 out of 69 bacterial strains were classified as serotypes 1, 6, 8, 10, and 20, with serotype 10 being the most prevalent. The antimicrobial susceptibility test revealed that 100% of the bacterial isolates were susceptible to Amoxicillin/clavulanic acid and Imipenem. On the contrary, the majority of R. anatipestifer strains were resistant to Nalidixic acid (89.9%), Streptomycin (75.4%), and Norfloxacin (72.5%). Conclusion: This is the first ever report in terms of identification, serotyping, and antimicrobial susceptibility tests of R. anatipestifer causing septicemia in ducks of Vietnam, providing useful scientific information for treatment as well as vaccine development to control the disease.

Evaluation of Two Multiplex PCR-High-Resolution Melt Curve Analysis Methods for Differentiation of Campylobacter jejuni and Campylobacter coli Intraspecies.

Campylobacter infection is a common cause of bacterial gastroenteritis in humans and remains a significant global public health issue. The capability of two multiplex PCR (mPCR)-high-resolution melt (HRM) curve analysis methods (i.e., mPCR1-HRM and mPCR2-HRM) to detect and differentiate 24 poultry isolates and three reference strains of Campylobacter jejuni and Campylobacter coli was investigated. Campylobacter jejuni and C. coli were successfully differentiated in both assays, but the differentiation power of mPCR2-HRM targeting the cadF gene was found superior to that of mPCR1-HRM targeting the gpsA gene or a hypothetical protein gene. However, higher intraspecies variation within C. coli and C. jejuni isolates was detected in mPCR1-HRM when compared with mPCR2-HRM. Both assays were rapid and required minimum interpretation skills for discrimination between and within Campylobacter species when using HRM curve analysis software.

Differentiation of Campylobacter jejuni and Campylobacter coli Using Multiplex-PCR and High Resolution Melt Curve Analysis.

Campylobacter spp. are important causes of bacterial gastroenteritis in humans in developed countries. Among Campylobacter spp. Campylobacter jejuni (C. jejuni) and C. coli are the most common causes of human infection. In this study, a multiplex PCR (mPCR) and high resolution melt (HRM) curve analysis were optimized for simultaneous detection and differentiation of C. jejuni and C. coli isolates. A segment of the hippuricase gene (hipO) of C. jejuni and putative aspartokinase (asp) gene of C. coli were amplified from 26 Campylobacter isolates and amplicons were subjected to HRM curve analysis. The mPCR-HRM was able to differentiate between C. jejuni and C. coli species. All DNA amplicons generated by mPCR were sequenced. Analysis of the nucleotide sequences from each isolate revealed that the HRM curves were correlated with the nucleotide sequences of the amplicons. Minor variation in melting point temperatures of C. coli or C. jejuni isolates was also observed and enabled some intraspecies differentiation between C. coli and/or C. jejuni isolates. The potential of PCR-HRM curve analysis for the detection and speciation of Campylobacter in additional human clinical specimens and chicken swab samples was also confirmed. The sensitivity and specificity of the test were found to be 100% and 92%, respectively. The results indicated that mPCR followed by HRM curve analysis provides a rapid (8 hours) technique for differentiation between C. jejuni and C. coli isolates.