Identification and clinical significance of Bordetella holmesii isolated from a rare case of bacteremia in Nantong China / 中华微生物学和免疫学杂志

ABSTRACT

Objective To analyze the identification, drug resistance and clinical significance of a rare bacterium of Bordetella holmesii ( B. holmesii) to improve its detection and clinical diagnosis and treat-ment. Methods A strain isolated from a bacteremia case was identified by bacterial culture, biochemical tests and 16S rRNA gene sequencing. Mega 7. 0 software was used to conduct a similarity analysis of 16S rRNA gene sequences between the type strains of Bordetella spp. and the isolate, and then a phylogenetic tree was constructed. Antibiotic resistance of the isolate was determined by E-test. Changes in bacterial growth were measured after adding different concentrations of riboflavin or its inhibitor lumiflavin to the cul-ture medium. Results B. holmesii ABD2 was the pathogen causing bacteremia in the immunocompetent pa-tient. It was deposited under the number of CGMCC 1. 13721 in China General Microbiological Culture Col-lection Center (CGMCC), and the 16S rRNA gene sequences were deposited in National Center for Biotech-nology Information ( NCBI) with the accession number of KT828544. 1. Unrooted tree showed that the B. holmesii strain was highly homologous with B. pertussis. Antibiotic susceptibility test showed that the mini-mum inhibitory concentrations ( MIC) of piperacillin, ceftazidime, cefepime, imipenem, meropenem, cipro-floxacin, levofloxacin, gentamicin, amikacin, erythromycin, tetracycline and polymyxin B against the isolate were low, while the MIC values of cefazolin, cefuroxime, cefoxitin, cefotaxime, aztreonam and trime-thoprim-sulfamethoxazole were high. Riboflavin accelerated the growth of B. holmesii ABD2, while its inhibi-tor lumiflavin had an inhibitory effect. Conclusions As B. holmesii is hard to isolate and identify, limited clinical, microbiological and epidemiological data are available. It is an under-recognized pathogen with a considerable amount of information that remains to be studied.