Shankar Chaitra, Nabarro Laura Eb, Anandan Shalini, Ravi Raji, Babu Priyanka, Munusamy Elakkiya, Jeyaseelan Visali, Rupali Priscilla, Verghese Valsan P, Veeraraghavan Balaji
Department of Clinical Microbiology,Christian Medical College, Vellore, Tamil Nadu.
Department of Biostatistics,Christian Medical College, Vellore, Tamil Nadu.
J Assoc Physicians India. 2018 Dec;66(12):13-16.
Infections caused by carbapenem resistant K. pneumoniae are increasing and associated with high mortality rates. There are increasing reports of hypermucoviscous/ hypervirulent K. pneumoniae isolated from various sources. However, there is limited data on the prevalence of hypermucoviscous strains among carbapenem-resistant K. pneumoniae from invasive infections in India and its association with mortality. rmpA, rmpA2 and magA genes are associated with these hypervirulent strains. In this study, we investigate the prevalence of hypermucoviscous strains amongst carbapenem resistant K. pneumoniae isolated from blood culture. Association of mortality rate with meropenem minimum inhibitory concentration and hypermucoviscous strains are determined.
86 non-repetitive carbapenem resistant K. pneumoniae isolated from bacteremia underwent E-test for meropenem minimum inhibitory concentration (MIC) determination and PCR for detection of carbapenamase genes. String test, PCR for rmpA, rmpA2 and magA were performed for characterisation of hypervirulent strains. Results: 31.3% of the 86 isolates displayed hypermucoviscous phenotype as indicated by a positive string test. Among the two genotypic markers, 7% were positive for rmpA2 and all were negative for rmpA and magA. 74.1% and 67.9% mortality were seen among string test positives and isolates meropenem MIC of ≥16µg/ml respectively (p 0.036 and 0.008 respectively). Isolates with both string positivity and meropenem MIC of ≥16µg/ml had a very high mortality rate of 84.2%.
String test, aids prediction of disease severity, and is independently associated with increased mortality in invasive carbapenem resistant K.pneumoniae health care-acquired infections. High meropenem MIC is a significant risk factor for mortality. Combination of string positive carbapenem resistant hypermucoviscous K. pneumoniae resulted in mortality rate of 84.2%. It is important to monitor prevalence of carbapenem resistant hypermucoviscous/hypervirulent K. pneumoniae among invasive isolates especially in a setting with high resistance rates as combination of increased virulence and decreased susceptibility to antimicrobials results in worse outcomes.
耐碳青霉烯类肺炎克雷伯菌引起的感染日益增多，且与高死亡率相关。从各种来源分离出高黏液性/高毒力肺炎克雷伯菌的报道也越来越多。然而，关于印度侵袭性感染中耐碳青霉烯类肺炎克雷伯菌中高黏液性菌株的流行情况及其与死亡率的关联的数据有限。rmpA、rmpA2和magA基因与这些高毒力菌株有关。在本研究中，我们调查了从血培养中分离出的耐碳青霉烯类肺炎克雷伯菌中高黏液性菌株的流行情况。确定了死亡率与美罗培南最低抑菌浓度及高黏液性菌株之间的关联。
对从菌血症中分离出的86株非重复性耐碳青霉烯类肺炎克雷伯菌进行E试验以测定美罗培南最低抑菌浓度（MIC），并进行PCR检测碳青霉烯酶基因。进行拉丝试验、rmpA、rmpA2和magA的PCR以鉴定高毒力菌株。结果：86株分离株中，31.3%表现出拉丝试验阳性所表明的高黏液性表型。在两种基因标记中，7%的rmpA2呈阳性，rmpA和magA均为阴性。拉丝试验阳性和美罗培南MIC≥16μg/ml的分离株的死亡率分别为74.1%和67.9%（p分别为0.036和0.008）。拉丝试验阳性且美罗培南MIC≥16μg/ml的分离株的死亡率非常高，为84.2%。
拉丝试验有助于预测疾病严重程度，且与侵袭性耐碳青霉烯类肺炎克雷伯菌医院获得性感染的死亡率增加独立相关。高美罗培南MIC是死亡率的一个重要危险因素。拉丝试验阳性的耐碳青霉烯类高黏液性肺炎克雷伯菌组合导致死亡率为84.2%。监测侵袭性分离株中耐碳青霉烯类高黏液性/高毒力肺炎克雷伯菌的流行情况很重要，尤其是在耐药率高的环境中，因为毒力增加和对抗菌药物敏感性降低的组合会导致更差的结果。
