Serotypes, virulence factors and multilocus sequence typing of <i>Glaesserella parasuis</i> from diseased pigs in Taiwan

Abstract

Serotype 4 (33.3%) and 5 (21.4%) were the most prevalent, followed by nontypable isolates (15.9%), serotype 13 (9.4%), 12 (6.5%), 14 (6.2%), 7 (3.3%), 1 (1.8%), 9 (1.1%), 11 (0.7%) and 6 (0.4%). Nine out of 10 putative virulence factors showed high positive rates, including group 1 <i>vtaA</i> (100%), <i>fhuA</i> (80.4%), <i>hhdA</i> (98.6%), <i>hhdB</i> (96.0%), <i>sclB7</i> (99.6%), <i>sclB11</i> (94.9%), <i>nhaC</i> (98.2%), <i>HAPS_0254</i> (85.9%), and <i>cirA</i> (99.3%). According to the results of antimicrobial susceptibility testing, ceftiofur and florfenicol were highly susceptible (>90%). Notably, 68.8% isolates showed multidrug resistance. MLST revealed 16 new alleles and 67 new sequence types (STs). STs of these isolated <i>G. parasuis</i> strains were classified into three clonal complexes and 45 singletons by Based Upon Related Sequence Types (BURST) analysis. All the <i>G. parasuis</i> strains in PubMLST database, including strains from the diseased pigs in the study, were defined into two main clusters by Unweighted Pair Group Method with Arithmetic Mean (UPGMA). Most isolates in this study and virulent isolates from the database were mainly located in cluster 2, while cluster 1 included a high percentage of nasal isolates from asymptomatic carriers. In conclusion, this study provides current prevalence and antimicrobial susceptibility of <i>G. parasuis</i> in Taiwan, which can be used in clinical diagnosis and treatment of Glässer's disease.