Department of Respiratory Medicine and Allergology, Sapporo Medical University School of Medicine, Sapporo, Japan.
Department of Microbiology, Sapporo Medical University School of Medicine, Sapporo, Japan.
Antimicrob Agents Chemother. 2018 Aug 27;62(9). doi: 10.1128/AAC.00851-18. Print 2018 Sep.
β-Lactam-resistant is a clinical concern. A high prevalence (>40%) of β-lactamase-negative high-level ampicillin-resistant (high-BLNAR) isolates in Japan has been reported. However, the reasons for the expansion are unknown. High-BLNAR strains possess an amino acid substitution, either Asn526Lys (group III) or Arg517His (group III-like) in addition to Ser385Thr, in penicillin-binding protein 3 (PBP3). To determine the current prevalence of high-BLNAR strains and the mechanisms behind their expansion in Japan, their prevalence, PBP3 types, multilocus sequence types, and susceptibilities to quinolones approved in Japan as alternatives were determined. Sixty percent of clinical isolates (62/104 isolates) were β-lactamase-negative ampicillin-resistant (BLNAR) strains. Among BLNAR isolates, 92% (57/62 isolates) were high-BLNAR strains. Most isolates were classified as belonging to group III, which contained many genotypes (11 PBP3 types and 25 sequence types). These results indicated that the expansion of high-BLNAR isolates was multiclonal and such strains are still predominant in Japanese clinical settings. One high-BLNAR isolate harbored the novel amino acid substitution Asn526Met in addition to Ser385Thr in PBP3, suggesting a new group (group IV). No quinolone-resistant isolates were identified. The MICs for the quinolones (moxifloxacin, garenoxacin, and tosufloxacin) were similar to that for levofloxacin, whereas sitafloxacin exhibited a lower MIC. However, we obtained 4 isolates with decreased quinolone susceptibility with the amino acid substitution Ser84Leu in GyrA, and 3 of those isolates were high-BLNAR isolates. In summary, this study shows that multiclonal high-BLNAR strains predominate in a Japanese university hospital. Isolates remain sensitive to quinolones, but vigilance is required to prevent the development of fluoroquinolone resistance in high-BLNAR strains.
β-内酰胺耐药是一个临床关注的问题。日本曾报道过β-内酰胺酶阴性高耐氨苄青霉素（高耐 BLNAR）分离株的高流行率（>40%）。然而，其扩张的原因尚不清楚。高耐 BLNAR 菌株除了 Ser385Thr 之外，还具有青霉素结合蛋白 3（PBP3）中的氨基酸取代，即 Asn526Lys（第 III 组）或 Arg517His（第 III 组样）。为了确定日本高耐 BLNAR 菌株的当前流行率及其扩张的机制，确定了它们的流行率、PBP3 类型、多位点序列类型以及日本批准的作为替代品的喹诺酮类药物的敏感性。60%的临床分离株（62/104 株）为β-内酰胺酶阴性氨苄青霉素耐药（BLNAR）株。在 BLNAR 分离株中，92%（57/62 株）为高耐 BLNAR 株。大多数分离株被归类为属于第 III 组，其中包含许多基因型（11 种 PBP3 类型和 25 种序列类型）。这些结果表明，高耐 BLNAR 分离株的扩张是多克隆的，并且此类菌株在日本临床环境中仍然占主导地位。一株高耐 BLNAR 分离株在 PBP3 中除了 Ser385Thr 之外还携带新的氨基酸取代 Asn526Met，提示存在一个新的组（第 IV 组）。未发现耐喹诺酮的分离株。喹诺酮（莫西沙星、加替沙星和托氟沙星）的 MIC 与左氧氟沙星相似，而司帕沙星的 MIC 较低。然而，我们获得了 4 株具有 GyrA 中 Ser84Leu 氨基酸取代的喹诺酮敏感性降低的分离株，其中 3 株为高耐 BLNAR 分离株。综上所述，本研究表明，多克隆高耐 BLNAR 菌株在日本一所大学医院中占主导地位。分离株仍对喹诺酮类药物敏感，但需要警惕高耐 BLNAR 菌株中氟喹诺酮类药物耐药性的发展。
