Child Health Research Foundation, Department of Microbiology, Dhaka Shishu Hospital, Dhaka 1207, Bangladesh.
International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
J Glob Antimicrob Resist. 2017 Mar;8:131-134. doi: 10.1016/j.jgar.2016.11.009. Epub 2017 Jan 26.
In recent years, an increasing prevalence of macrolide resistance among pneumococci in Bangladesh has been observed. However, the scenario remains incomplete, as few isolates (<1%) are available from pneumonia cases and most pneumococcal meningitis cases (>80%) are culture-negative. This study optimised a triplex PCR method to detect macrolide resistance genes (MRGs) (mefA and ermB) and cpsA from culture-negative pneumococcal cases to predict the prevalence and level of macrolide resistance.
The presence of MRGs among pneumococcal strains (n=153) with a wide range of erythromycin MICs (<0.5 to ≥256mg/L) was determined by PCR. Triplex PCR was validated by simultaneous detection of MRG(s) and cpsA in culture-negative clinical specimens and corresponding isolates. The known impact of the presence of specific MRG(s) on MICs of strains was used to predict the MICs of non-culturable strains based on the presence/absence of MRG(s) in the specimens.
None of the erythromycin-susceptible isolates possessed any of the MRGs, and all non-susceptible strains had ≥1 MRG. MICs were 2-16mg/L and ≥256mg/L for 93% of strains with mefA and ermB, respectively, whereas 100% of isolates with both genes had MICs≥256mg/L. PCR for body fluids showed 100% concordance with corresponding isolates when tested for MRG(s) in parallel.
Erythromycin MICs can be predicted for non-culturable strains with 93-100% precision based on detection of ermB and/or mefA. This method will be useful for establishing comprehensive surveillance for macrolide resistance among pneumococci, specifically in the population with prior antibiotic use.
近年来，孟加拉国肺炎球菌对大环内酯类药物的耐药性呈上升趋势。然而，由于从肺炎病例中获得的分离株较少（<1%），而且大多数肺炎球菌性脑膜炎病例（>80%）培养呈阴性，因此情况仍不完整。本研究优化了一种三重 PCR 方法，以检测培养阴性肺炎球菌病例中的大环内酯类耐药基因（MRG）（mefA 和 ermB）和 cpsA，以预测大环内酯类耐药的流行率和水平。
通过 PCR 检测具有广泛红霉素 MIC 值（<0.5 至≥256mg/L）的肺炎球菌菌株（n=153）中 MRG 的存在。通过同时检测培养阴性临床标本和相应分离株中的 MRG(s)和 cpsA，对三重 PCR 进行验证。根据标本中 MRG(s)的存在/缺失，利用已知特定 MRG(s)对菌株 MIC 值的影响，预测非可培养菌株的 MIC 值。
所有红霉素敏感菌株均未携带任何 MRG，所有非敏感菌株均携带≥1 种 MRG。mefA 和 ermB 的 MIC 值分别为 2-16mg/L 和≥256mg/L，占耐药菌株的 93%，而携带这两种基因的菌株的 MIC 值均≥256mg/L。当同时平行检测 MRG(s)时，对体液进行 PCR 检测与相应分离株具有 100%的一致性。
基于 ermB 和/或 mefA 的检测，可对非可培养菌株的红霉素 MIC 值进行 93-100%的准确预测。该方法将有助于建立对肺炎球菌大环内酯类耐药的全面监测，特别是在有抗生素使用史的人群中。
