Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Japan.
J Antimicrob Chemother. 2019 Apr 1;74(4):931-934. doi: 10.1093/jac/dky542.
We have previously identified group B Streptococcus (GBS) clinical isolates with reduced penicillin susceptibility (PRGBS) that were non-susceptible to cefotaxime; however, the rates of cefotaxime and ceftriaxone non-susceptibility among PRGBS isolates have never been reported. Therefore, we first determined the MICs of 22 antibacterial drugs/compounds for 74 PRGBS isolates and then determined the rates of cefotaxime and ceftriaxone non-susceptibility among these isolates.
We used 74 clinical PRGBS isolates, previously collected in Japan and confirmed to harbour relevant amino acid substitutions in PBP2X. We also used 80 penicillin-susceptible GBS (PSGBS) clinical isolates as controls. The MICs of 22 antibacterial drugs/compounds for all 154 GBS isolates were determined via microdilution and/or agar dilution methods, as recommended by the CLSI.
The rates of non-susceptibility/resistance to ampicillin, cefotaxime, ceftriaxone and levofloxacin for the 80 PSGBS isolates were 0%, 0%, 0% and 30%, respectively, but were 15% (P = 0.0003), 28% (P < 0.0001), 36% (P < 0.0001) and 93% (P < 0.0001) for the 74 PRGBS isolates, respectively. No PRGBS isolates were identified to be non-susceptible to meropenem, doripenem, vancomycin, quinupristin/dalfopristin, daptomycin or linezolid.
We found that cefotaxime- and ceftriaxone-non-susceptible PRGBS isolates occur at relatively high rates in Japan. Importantly, this finding suggests that the range of drugs likely to be effective in treating PRGBS infections may be limited compared with those available for PSGBS infections; therefore, clinicians should exercise care when considering drug choice and efficacy for PRGBS infections.
我们之前已经鉴定出具有降低青霉素敏感性（PRGBS）的 B 组链球菌（GBS）临床分离株，这些分离株对头孢噻肟不敏感；然而，PRGBS 分离株对头孢噻肟和头孢曲松的不敏感性率从未有过报道。因此，我们首先确定了 74 株 PRGBS 分离株的 22 种抗菌药物/化合物的 MIC 值，然后确定了这些分离株中头孢噻肟和头孢曲松的不敏感性率。
我们使用了 74 株来自日本的临床 PRGBS 分离株，这些分离株之前被收集并证实携带相关的 PBP2X 氨基酸取代。我们还使用了 80 株青霉素敏感的 GBS（PSGBS）临床分离株作为对照。所有 154 株 GBS 分离株的 22 种抗菌药物/化合物的 MIC 值均通过微量稀释法和/或琼脂稀释法确定，如 CLSI 所推荐的那样。
80 株 PSGBS 分离株对氨苄西林、头孢噻肟、头孢曲松和左氧氟沙星的不敏感性/耐药率分别为 0%、0%、0%和 30%，而 74 株 PRGBS 分离株的不敏感性/耐药率分别为 15%（P=0.0003）、28%（P<0.0001）、36%（P<0.0001）和 93%（P<0.0001）。没有 PRGBS 分离株被鉴定为对美罗培南、多利培南、万古霉素、奎奴普丁/达福普汀、达托霉素或利奈唑胺不敏感。
我们发现，头孢噻肟和头孢曲松不敏感的 PRGBS 分离株在日本的发生率相对较高。重要的是，这一发现表明，与 PSGBS 感染相比，可能有效治疗 PRGBS 感染的药物范围可能有限；因此，临床医生在考虑 PRGBS 感染的药物选择和疗效时应谨慎。
