title: Genetic analysis of a pediatric clinical isolate of Moraxella catarrhalis with resistance to macrolides and quinolones.
abstract: During the surveillance conducted in 2012 by the Drug-resistant Pathogen Surveillance Group in Pediatric Infectious Disease, we isolated a strain of Moraxella catarrhalis that demonstrated resistance to both macrolides and quinolones from a male pediatric patient aged 1.5 years who had developed acute bronchitis. Then we evaluated the susceptibility of this strain to different types of antibacterial agents and conducted a genetic analysis. The results of the susceptibility evaluation showed that the MIC values of azithromycin, clarithromycin, and rokitamycin were >64 μg/mL, >64 μg/mL, and 4 μg/mL, respectively; clearly demonstrating resistance to macrolides. The MIC values of the quinolones levofloxacin, tosufloxacin, and garenoxacin were 4 μg/mL, 2 μg/mL, and 1 μg/mL, respectively; indicating decreased susceptibility. The genetic analysis of this strain revealed one mutation in 23s rRNA with a replacement of adenine by thymine at nucleotide position 2330 (A2330T) and another mutation in gyrB at nucleotide position 1481 by replacement of adenine with guanine (A1481G) that caused a substitution of the 494 th asparagine acid by glycine, as being associated with the observed resistance to macrolides and quinolones, respectively. Similar to drug-resistant bacteria Streptococcus pneumoniae and Haemophilus influenzae, the prevalence of which has recently increased, the treatment of drug-resistant M. catarrhalis infections is considered difficult due to the development of resistance to different types of antibacterial agents. It is vital to maintain an unwavering focus on the trend toward an increasing number of drug-resistant M. catarrhalis strains and ensure the proper use of each antibacterial agent.
authors.affiliation: Department of Infectious Diseases, Keio University School of Medicine, Shinjuku, Japan; The Drug-Resistant Pathogen Surveillance Group in Pediatric Infectious Disease, Japan. Electronic address: siwata@a8.keio.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Iwata
authors.affiliation: The Drug-Resistant Pathogen Surveillance Group in Pediatric Infectious Disease, Japan; Department of Pediatrics, Fuji Heavy Industries Health Insurance Society Ota Memorial Hospital, Ota, Japan.
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Sato
authors.affiliation: The Drug-Resistant Pathogen Surveillance Group in Pediatric Infectious Disease, Japan; Department of Pediatrics, Saitama Sekishinkai Hospital, Sayama, Japan.
authors.forename: Yoshikiyo
authors.initials: Y
authors.lastname: Toyonaga
authors.affiliation: The Kitasato Institute, Kitasato University Research Center for Anti-infectious Drugs, Minato, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Hanaki
authors.affiliation: The Drug-Resistant Pathogen Surveillance Group in Pediatric Infectious Disease, Japan; The Kitasato Institute, Kitasato University Research Organization for Infection Control Sciences, Minato, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sunakawa
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D006801:Humans; D007223:Infant; D018942:Macrolides / Q000494:pharmacology*; D008297:Male; D008826:Microbial Sensitivity Tests; D001936:Moraxella catarrhalis / Q000187:drug effects / Q000235:genetics; D045828:Moraxellaceae Infections / Q000382:microbiology*; D015363:Quinolones / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D015363:Quinolones
keywords: Drug resistance; Macrolides; Moraxella catarrhalis; Pediatric infectious disease; Quinolones; Susceptibility