Ito Ryota, Kawamura Masato, Sato Takumi, Fujimura Shigeru
Tohoku Medical and Pharmaceutical University, Division of Clinical Infectious Diseases & Chemotherapy, Sendai, Miyagi, Japan.
Infect Drug Resist. 2022 Oct 10;15:5867-5878. doi: 10.2147/IDR.S382142. eCollection 2022.
Cefmetazole (CMZ), a cephamycin antibiotic, is primarily used as a definitive therapy for Extended Spectrum β-Lactamase (ESBL)-producing infections. However, the mechanism of CMZ resistance in is still unknown. To elucidate the resistance mechanism and to determine combined drugs for prevention of resistance acquisition.
Clinical isolates of 14 ESBL-producing and non-producing 12 isolates were used in in vitro testing of CMZ resistance acquisition. After 10-day of CMZ exposure (1st subculture), these strains were incubated in an antibacterial-free medium for 14-day. These strains were again exposed to CMZ for 10-day (2nd subculture) and confirmed for changes in MIC. For each strain detected after 1st subculture, each mRNA expression level of porin, chromosomal , and drug-efflux pump was measured using real-time RT-PCR. Relebactam (REL) has the potency to recover antimicrobial activity against carbapenem-resistant that has porin deficiency. REL was added to the CMZ dilution series, and MIC changes and those of porin were confirmed.
Of these 26 strains, 15 strains (57.7%) acquired resistance after 1st subculture, but after passage culture on the antibacterial-free medium, 11 strains recovered susceptibility. These 11 strains showed resistance after 2nd subculture. The expression levels of and were significantly decreased in these strains (<0.05). When REL was added, all strains suppressed resistance acquisition after 1st subculture. The mechanism was the activation of .
Our results showed that the mRNA expression levels of genes encoding porin were decreased in the strains that acquired resistance due to CMZ exposure, and that and in particular were thought to be involved in the acquisition of resistance. The CMZ acquisition of resistance was also suppressed by the concomitant use of REL and actually suppressed the decrease in mRNA expression in . It was confirmed that porin reactivated by REL.
头孢美唑（CMZ）是一种头孢霉素类抗生素，主要用作产超广谱β-内酰胺酶（ESBL）感染的确定性治疗药物。然而，CMZ耐药的机制仍不清楚。为阐明耐药机制并确定预防耐药产生的联合用药。
14株产ESBL临床分离株和12株非产ESBL临床分离株用于CMZ耐药获得的体外试验。在CMZ暴露10天（第1次传代培养）后，将这些菌株在无抗菌剂的培养基中培养14天。这些菌株再次暴露于CMZ 10天（第2次传代培养），并确认MIC的变化。对于第1次传代培养后检测到的每株菌株，使用实时RT-PCR测量孔蛋白、染色体和药物外排泵的每个mRNA表达水平。瑞来巴坦（REL）具有恢复对存在孔蛋白缺陷的耐碳青霉烯菌抗菌活性的能力。将REL添加到CMZ稀释系列中，并确认MIC变化和孔蛋白变化。
在这26株菌株中，15株（57.7%）在第1次传代培养后获得耐药性，但在无抗菌剂培养基上进行传代培养后，11株恢复了敏感性。这11株菌株在第2次传代培养后显示出耐药性。这些菌株中染色体和的表达水平显著降低（<0.05）。当添加REL时，所有菌株在第1次传代培养后均抑制了耐药性的获得。其机制是染色体的激活。
我们的结果表明，因CMZ暴露而获得耐药性的菌株中，编码孔蛋白的基因的mRNA表达水平降低，并且认为染色体和尤其与耐药性的获得有关。REL的联合使用也抑制了CMZ耐药性的获得，实际上抑制了染色体中mRNA表达的降低。证实REL使孔蛋白重新激活。
