Instituto de Ciências Biológicas e Naturais, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais, Brazil.
Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
J Med Microbiol. 2020 Jan;69(1):41-45. doi: 10.1099/jmm.0.001117.
Vancomycin has become the first-line therapy for most infections caused by methicillin-resistant staphylococci. To evaluate the vancomycin MIC, staphylococcal cassette chromosome (SCC) types and clonality of coagulase-negative staphylococci (CoNS) isolates recovered from neonates with true primary bloodstream infections (BSI). CoNS isolates were prospectively recovered from blood cultures of non-repetitive patients admitted to a neonatal intensive care unit (NICU) in a tertiary-care hospital during a 3-year period. BSI was defined based on established criteria. Micro-organisms were identified phenotypically and by PCR. MIC-values for vancomycin and oxacillin were determined by broth dilution method and E-test. The SCC type conferring methicillin resistance was determined by multiplex PCR. The heterogeneous vancomycin (hV) resistance phenotype was screened on brain heart infusion agar containing 4 µg ml of vancomycin. The clonality was investigated by PFGE. Seventy-four CoNS isolates were recovered from blood cultures of neonates during the study period but only 40 (54 %) were associated with true primary BSI. Nine (22.5%) babies died. was the most prevalent species (95 %; 38/40). All isolates were methicillin-resistant (MR). SCC type IV was predominant (55.3 %; 21/38). Most (80.0 %; 32/38) isolates exhibited vancomycin MIC-values of 2-4 µg ml not associated with the SCC type or clonality. Sixteen (42.1%) isolates displayed hV resistance. All babies who died were harbouring MR- exhibiting vancomycin MICs of 2-4 µg ml. The findings of this study demonstrated that blood invasive MR- isolates recovered at NICU tend to show decreased vancomycin susceptibility making therapy of those fragile patients difficult.
万古霉素已成为治疗耐甲氧西林葡萄球菌引起的大多数感染的一线治疗药物。为了评估凝固酶阴性葡萄球菌（CoNS）从新生儿真正原发性血流感染（BSI）中分离出的万古霉素 MIC、葡萄球菌盒式染色体（SCC）类型和克隆性。在 3 年期间，从一家三级医院新生儿重症监护病房（NICU）中连续住院患者的血液培养物中前瞻性地分离出 CoNS 分离株。BSI 是根据既定标准定义的。通过表型和 PCR 鉴定微生物。通过肉汤稀释法和 E 试验确定万古霉素和苯唑西林的 MIC 值。通过多重 PCR 确定赋予耐甲氧西林的 SCC 类型。在含有 4µg ml 万古霉素的脑心浸液琼脂上筛选异质性万古霉素（hV）耐药表型。通过 PFGE 研究克隆性。在研究期间，从新生儿血液培养物中分离出 74 株 CoNS 分离株，但只有 40 株（54%）与真正的原发性 BSI 有关。9 例（22.5%）婴儿死亡。是最常见的物种（95%；38/40）。所有分离株均对甲氧西林耐药（MR）。SCC 类型 IV 占优势（55.3%；21/38）。大多数（80.0%；32/38）分离株表现出与 SCC 类型或克隆性无关的万古霉素 MIC 值为 2-4µg ml。16 株（42.1%）分离株显示 hV 耐药性。所有死亡的婴儿均携带 MR-，万古霉素 MIC 值为 2-4µg ml。本研究的结果表明，从 NICU 中分离出的血液侵袭性 MR- 分离株往往表现出对万古霉素的敏感性降低，使这些脆弱患者的治疗变得困难。
