Biofilm formation and antibiotic resistance in Klebsiella pneumoniae urinary strains.

AIMS: 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. METHODS AND RESULTS: 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. CONCLUSIONS: XDR strains exhibited phenotypic and genotypic features supporting a significant growth as biofilm. SIGNIFICANCE AND IMPACT OF THE STUDY: 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.

Risk factors for carbapenemase-producing Enterobacteriaceae colonization of asymptomatic carriers on admission to an Italian rehabilitation hospital.

The spread of carbapenemase-producing Enterobacteriaceae (CPE) has become a worldwide problem. Early identification and isolation of asymptomatic carriers are important for infection prevention and control measures. All inpatients (N=1427) admitted to 'Fondazione Santa Lucia' Rehabilitation Hospital in 2014 were screened by rectal swab; 10.2% of them were CPE-colonized. The multivariate analysis on anamnestic data showed that both previous admission to an intensive care unit (odds ratio: 4.04; 95% confidence interval: 2.20-7.44; P<0.001) or post-acute care hospitals (2.88; 1.74-4.77; P<0.001) and presence of a central venous catheter (2.19; 1.34-3.59; P<0.001) were significant risk factors.

High rate of colistin resistance among patients with carbapenem-resistant Klebsiella pneumoniae infection accounts for an excess of mortality.

Carbapenem-resistant Klebsiella pneumoniae (CR-KP) is becoming a common cause of healthcare-associated infection in Italy, with high morbidity and mortality. Prevalent CR-KP clones and resistance mechanisms vary between regions and over time. Therapeutic approaches and their impact on mortality have to be investigated. We performed a prospective study of patients with CR-KP isolation, hospitalized in nine hospitals of Rome, Italy, from December 2010 to May 2011, to describe the molecular epidemiology, antibiotic treatment and risk factors for mortality. Overall, 97 patients (60% male, median age 69 years) were enrolled. Strains producing blaKPC-3 were identified in 89 patients, blaVIM in three patients and blaCTX-M-15 plus porin defects in the remaining five patients. Inter-hospital spread of two major clones, ST512 and ST258, was found. Overall, 36.1% and 20.4% of strains were also resistant to colistin and tigecycline, respectively. Infection was diagnosed in 91 patients who received appropriate antibiotic treatment, combination therapy and removal of the infectious source in 73.6%, 59.3% and 28.5% of cases, respectively. Overall, 23 different antibiotic regimens were prescribed. In-hospital mortality was 25.8%. Multivariate analysis adjusted for appropriate treatment, combination therapy and infectious-source removal, showed that Charlson comorbidity score, intensive-care unit onset of infection, bacteraemia and infection due to a colistin-resistant CR-KP strain were independent risk factors for mortality. The spread of clones producing K. pneumoniae carbapenemases, mainly ST258, is currently the major cause of CR-KP infection in central Italy. We observed a high rate of resistance to colistin that is independently associated with worse outcome.