Molecular detection of Streptobacillus hongkongensis in human nasopharynx in Hong Kong

Abstract

Streptobacillus hongkongensis is a novel member of the genus Streptobacillus. It is a fastidious and pleomorphic Gram-negative bacillus which has been isolated recently in two streptobacillary like infections reported in Hong Kong. Bacterial strain 〖 HKU33〗^T was firstly isolated from the peritonsillar abscess while strain HKU34 was isolated from the joint fluid of another individual. Regarding the phylogenetic study of the complete 16S rRNA gene, partial groEL, gyrB and recA gene sequences, 〖 HKU33〗^T and HKU34 relate most closely to Streptobacillus moniliformis, which is one of the etiological agent of widespread rat bite fever. Nevertheless, there is no information on the prevalence of S. hongkongensis and its role in human. As the nasopharynx of rats is one of the dominant natural reservoir of S. moniliformis, a bacterium highly related species to S. hongkongensis, whether S. hongkongensis also naturally resides in the nasopharynx of rats or other animals, such as human, is of research interest.

In this study, human nasopharyngeal swabs were collected for bacterial culture. Total bacterial DNA were then collected and the presence of S. hongkongensis genomic DNA in the samples were screened by PCR-amplification, using the 16 rRNA gene as the DNA marker and specific primers. The partial bacterial 16S rRNA gene sequences obtained were compared with those of other bacteria in the GenBank database. Out of 277 samples, 45 yielded DNA fragments which shared > 97% partial 16S rRNA gene sequence homology with S. hongkongensis〖 HKU33〗^T, indicating that the prevalence of S. hongkongensis in human nasopharynx is 16.2%