Vuotto C, Longo F, Pascolini C, Donelli G, Balice M P, Libori M F, Tiracchia V, Salvia A, Varaldo P E
Microbial Biofilm Laboratory, Fondazione Santa Lucia, Rome, Italy.
Microbiological Laboratory, Fondazione Santa Lucia, Rome, Italy.
J Appl Microbiol. 2017 Oct;123(4):1003-1018. doi: 10.1111/jam.13533. Epub 2017 Aug 25.
Multidrug-resistant Klebsiella pneumoniae has become a relevant healthcare-associated pathogen. Capsule, type 1 and 3 fimbriae (mrkA gene), type 2 quorum-sensing system (luxS), synthesis of D-galactan I (wbbM), LPS transport (wzm) and poly-beta-1,6-N-acetyl-D-glucosamine (pgaA) seem involved in K. pneumoniae biofilm. Nonenzymatic antibiotic resistance is related to nonexpression or mutation of porins (OmpK35 and OmpK36), and efflux pump (acrB) overexpression. The aim of this study was to analyse some virulence factors of K. pneumoniae isolates, and to evaluate possible correlations between their antibiotic resistance profile and ability to form biofilm.
Quantitative biofilm production assay, congo red agar test and string test were performed on 120 isolates clustered in 56 extensively drug-resistant (XDR), 40 MDR and 24 susceptible (S) strains. Nine representative strains were analysed by real-time RT-PCR for the expression of antibiotic resistance (OmpK35, OmpK36, acrB) and biofilm production genes (mrkA, luxS, pga, wbbM, wzm) during planktonic and sessile growth. XDR isolates showed a higher ability to form biofilm (91·07%) and to produce polysaccharides (78·57%) when compared to MDR and S strains. In biofilm-growing XDR strains, seven of eight genes were upregulated, with the only exception of OmpK36.
XDR strains exhibited phenotypic and genotypic features supporting a significant growth as biofilm.
This study produces new findings that highlight a positive correlation between antibiotic resistance profile and biofilm-forming ability in XDR K. pneumoniae strains. These new evidences might contribute to the progress in selection of therapeutic treatments of infections caused by K. pneumoniae resistant also to the 'last line of defence' antibiotics, that is, carbapenems.
多重耐药肺炎克雷伯菌已成为一种重要的医疗保健相关病原体。荚膜、1型和3型菌毛（mrkA基因）、2型群体感应系统（luxS）、D-半乳聚糖I的合成（wbbM）、LPS转运（wzm）和聚-β-1,6-N-乙酰-D-葡萄糖胺（pgaA）似乎与肺炎克雷伯菌生物膜的形成有关。非酶促抗生素耐药性与孔蛋白（OmpK35和OmpK36）的不表达或突变以及外排泵（acrB）的过表达有关。本研究的目的是分析肺炎克雷伯菌分离株的一些毒力因子，并评估其抗生素耐药谱与形成生物膜能力之间的可能相关性。
对120株分离株进行了定量生物膜产生试验、刚果红琼脂试验和拉丝试验，这些分离株分为56株广泛耐药（XDR）、40株多重耐药（MDR）和24株敏感（S）菌株。通过实时RT-PCR分析了9株代表性菌株在浮游生长和固着生长期间抗生素耐药性（OmpK35、OmpK36、acrB）和生物膜产生基因（mrkA、luxS、pga、wbbM、wzm）的表达。与MDR和S菌株相比，XDR分离株形成生物膜的能力（91.07%）和产生多糖的能力（78.57%）更高。在生物膜生长的XDR菌株中，八个基因中有七个上调，唯一的例外是OmpK36。
XDR菌株表现出支持生物膜显著生长的表型和基因型特征。
本研究产生了新的发现，突出了XDR肺炎克雷伯菌菌株的抗生素耐药谱与生物膜形成能力之间的正相关。这些新证据可能有助于在选择治疗对“最后一道防线”抗生素即碳青霉烯类也耐药的肺炎克雷伯菌引起的感染的治疗方法方面取得进展。
