Fluoroquinolone Efflux by the Plasmid-Mediated Multidrug Efflux Pump QacB Variant QacBIII in Staphylococcus aureus▿

Plasmids that carry the multidrug efflux genes qacA and qacB are widely distributed in methicillin-resistant Staphylococcus aureus (MRSA). Although the QacA and QacB proteins are similar to each other, their respective substrate specificities may differ. We investigated the variability and structure-function relationships of QacA and QacB in MRSA isolates. The amino acid sequences of 7 QacA and 25 QacB proteins showed that QacB was present in three variants, designated QacBII, QacBIII, and QacBIV, that were different from the prototypic QacB variant encoded by plasmid pSK23, which was named QacBI, while QacA was present in two variants. When cloned and expressed in S. aureus, the strain carrying qacBIII exhibited higher susceptibility to dyes and decreased susceptibility to norfloxacin and ciprofloxacin compared to strains carrying the other QacB variants. Site-directed mutagenesis experiments revealed that the residue at position 320 in QacB plays an important role in the resistance phenotypes to dyes and fluoroquinolones. Furthermore, the accumulation of norfloxacin and ciprofloxacin in the strain carrying qacBIII was significantly decreased. Our data demonstrate that the plasmid-mediated multidrug efflux pump QacB variant QacBIII confers the capability for fluoroquinolone efflux on S. aureus

Surveillance of Antimicrobial Prescriptions in Community Pharmacies Located in Tokyo, Japan

An antimicrobial resistance (AMR) Action Plan was launched in 2016 to prevent the spread of antimicrobial-resistant bacteria in Japan. Additional support for the appropriate use of pediatric antimicrobial agents was initiated in 2018 to promote the appropriate use of antimicrobial agents in the community. To evaluate the effectiveness of the AMR Action Plan in the community, we investigated antimicrobial prescriptions in community pharmacies. Data on prescriptions for antimicrobial agents dispensed in 42 community pharmacies located in the Tama district, Tokyo, Japan, were collected between April 2013 and December 2019. In this study, we employed the DPY, which was calculated as defined daily doses (DDDs)/1000 prescriptions/year. The DPY is the number of antimicrobial agents used (potency) per 1000 antimicrobial prescriptions dispensed in pharmacies per year. The number of prescriptions for third-generation cephalosporins, fluoroquinolones, and macrolides decreased after the initiation of the AMR Action Plan; the DPYs of these antimicrobial agents decreased significantly by 31.4%, increased by 15.8%, and decreased by 23.6%, respectively (p < 0.05). The number of antimicrobial prescriptions for pediatric patients has been decreasing since 2018. Declines in the DPYs of third-generation cephalosporins, fluoroquinolones, and macrolides were higher in pediatric pharmacies than in other pharmacies. Our data suggest that the AMR Action Plan and additional support for the appropriate use of antimicrobial agents in children influenced the number of antimicrobial prescriptions in community pharmacies in Japan

In vitro anti-biofilm effect of anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) agents against the USA300 clone

Objectives: Infection with a typical community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), the USA300 clone, has become a worldwide epidemic. Biofilm formation at the site of infection is one of the reasons for the development of intractable infectious diseases resulting from this clone. Here we evaluated the in vitro antibiofilm effects of anti-MRSA agents to identify the most effective agent against the USA300 clone embedded in biofilms. Methods: Vancomycin, linezolid, teicoplanin, daptomycin, arbekacin and tigecycline were used as anti-MRSA agents. The biofilm permeability of the anti-MRSA agents was assessed using a biofilm-coated Transwell®. Morphological and compositional effects of anti-MRSA agents against biofilms were analysed based on the distribution of fluorescence intensity using confocal laser microscopy. Bactericidal activities of the anti-MRSA agents against biofilm-embedded S. aureus were compared. Results: The permeability rates of linezolid (93.1%), daptomycin (91.3%), arbekacin (87.1%) and tigecycline (99.7%) for biofilms formed by the USA300 clone were found to be significantly higher than those of vancomycin (64.9%) and teicoplanin (62.3%) (P < 0.01). Confocal microscopic analysis showed that daptomycin greatly altered the biofilm morphology (decreased thickness and increased roughness) and markedly reduced the area occupied by the biofilm. Furthermore, daptomycin effectively reduced the extracellular DNA of biofilms and showed the highest bactericidal activity against biofilm-embedded USA300 clone among the anti-MRSA agents. Conclusion: The findings from this study demonstrate that, of the tested anti-MRSA agents, daptomycin is the most effective against biofilm-embedded USA300 clone in vitro

Severity and intractableness of skin infections caused by Panton–Valentine leukocidin‐positive methicillin‐resistant Staphylococcus aureus

Abstract Cases of skin infections caused by Panton–Valentine leukocidin (PVL)‐positive methicillin‐resistant Staphylococcus aureus (MRSA), particularly USA300 clone, have been increasing in Japan. We report that clinical findings of 5 patients with PVL‐positive MRSA and compared to those of four patients with PVL‐negative MRSA. Severities of patients with PVL‐positive MRSA were significantly higher than those of patients with PVL‐negative MRSA. Average durations of antimicrobial therapy for patients with PVL‐positive MRSA were 3.4‐fold longer than those for patients with PVL‐negative MRSA. Our data suggest that PVL‐positive MRSA should be deal with a causative agent for intractable skin infections in Japan likewise other countries

Specific clones of Staphylococcus lugdunensis may be associated with colon carcinoma

Staphylococcus lugdunensis produces a tannase with activity that may be associated with the onset of colon carcinoma. To clarify this feature of colon carcinoma-associated S. lugdunensis, we obtained isolates from healthy subjects and patients with colon adenomas and carcinomas and analyzed their genetic backgrounds. In total, 40 S. lugdunensis isolates from 288 rectal swabs collected between 2002 and 2008 were used. These isolates were classified into four groups according to the diseases of the subjects: healthy (n = 13), colon carcinoma (n = 13), colon adenoma (n = 9), and unknown (n = 5). The isolates were also classified by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing. In addition, an antimicrobial susceptibility test and detection of resistance genes were performed for all isolates. According to the PFGE analysis, 40 isolates could be classified into five groups. Among the groups, carcinoma and colon adenoma patients were significantly more frequently (40.9%) classified into group D (p < 0.05), whereas healthy subjects were more frequently (38.5%) classified into group A. All isolates in group D were typed as ST27, which was clearly different than isolates in the other groups. All isolates were susceptible to the antimicrobial agents tested, including β-lactams, although seven strains produced β-lactamase. Our data suggest that a specific clone of S. lugdunensis might be associated with colon carcinoma and colon adenoma. This clone showed high susceptibility to many antimicrobial agents. Therefore, eradication therapy may lead to a decreased risk of colon carcinoma. Keywords: Staphylococcus lugdunensis, Colon carcinoma, Pulsotype, Multilocus sequence typin