Virulence Characteristics and Molecular Typing of Carbapenem-Resistant ST15 Klebsiella pneumoniae Clinical Isolates, Possessing the K24 Capsular Type.

Klebsiella pneumoniae is an opportunistic pathogen that frequently causes nosocomial and community-acquired (CA) infections. Until now, a limited number of studies has been focused on the analyses of changes affecting the virulence attributes. Genotypic and phenotypic methods were used to characterise the 39 clinical K. pneumoniae isolates; all belonged to the pan-drug resistant, widespread clone ST 15 and expressed the K24 capsule. PFGE has revealed that the isolates could be divided into three distinct genomic clusters. All isolates possessed allS and uge genes, known to contribute to the virulence of K. pneumoniae and 10.25% of the isolates showed hypermucoviscosity, 94.87% produced type 1 fimbriae, 92.3% produced type 3 fimbriae, and 92.3% were able to produce biofilm. In vivo persistence could be supported by serum resistance 46.15%, enterobactin (94.87%) and aerobactin (5.12%) production and invasion of the INT407 and T24 cell lines. Sequence analysis of the whole genomes of the four representative strains 11/3, 50/1, 53/2 and 53/3 has revealed high sequence homology to the reference K. pneumoniae strain HS11286. Our results represent the divergence of virulence attributes among the isolates derived from a common ancestor clone ST 15, in an evolutionary process that occurred both in the hospital and in the community.

Identification and characterization of CTX-M-15 producing Klebsiella pneumoniae clone ST101 in a Hungarian university teaching hospital.

We investigated the molecular epidemiology of extended spectrum ß-lactamase (ESBL) producing Klebsiella pneumoniae isolates derived from the teaching hospitals of University of Pécs, Pécs, Hungary in the time period 2004-2008. Molecular typing, antimicrobial susceptibility testing, detection of common ß-lactamase genes (bla(CTX-M), bla(TEM) and bla(SHV)) and virulence associated traits (hypermucoviscosity, magA, k2a, rmpA, siderophores, type 1 and 3 fimbria, biofilm formation, serum resistance) were performed for 102 isolates. The results showed the presence of three major ciprofloxacin resistant CTX-M-15 producing clones (ST15 n = 69, ST101 n = 10, and ST147 n = 9), of which ST15 was predominant and universally widespread. Considering distribution in time and place, ST101 and ST147 were detected at fewer inpatient units and within a narrower time frame, as compared to ST15. Beside major clones, eleven minor clones were identified, and were shown to harbour the following ß-lactamase genes: six clones carried bla(CTX-M), four clones harboured bla(SHV-5) and one clone possessed both bla(CTX-M) and ESBL type bla(SHV). Among the SHV-5 producing K. pneumoniae clones a novel sequence type was found, namely ST1193, which harboured a unique infB allele. Different virulence factor content and peculiar antimicrobial susceptibility profile were characteristic for each clone. In contrast to major clone isolates, which showed high level resistance to ciprofloxacin, minor clone isolates displayed significantly lower MIC values for ciprofloxacin suggesting a role for fluoroquinolones in the dissemination of the major K. pneumoniae clones. This is the first description of the CTX-M-15 producing K. pneumoniae clone ST101 in Hungary.

Chemomechanical preparation by hand instrumentation and by Mtwo engine-driven rotary files, an ex vivo study.

OBJECTIVE: To compare the disinfecting efficacy of the sodium hypochlorite irrigation by root canal preparation with stainless steel hand files, taper 0.02 and nickel-titanium Mtwo files with taper 0.04-0.06. STUDY DESIGN: 40 extracted human teeth were sterilized, and then inoculated with Enterococcus faecalis (ATCC 29212). After 6 day incubation time the root canals were prepared by hand with K-files (n=20) and by engine-driven Mtwo files (VDW, Munich, Germany) (n=20). Irrigation was carried out with 2.5% NaOCl in both cases. Samples were taken and determined in colony forming units (CFU) from the root canals before and after the preparation with instruments #25 and #35. RESULTS: Significant reduction in bacterial count was determined after filing at both groups. The number of bacteria kept on decreasing with the extension of apical preparation diameter. There was no significant difference between the preparation sizes in the bacterial counts after hand or engine-driven instrumentation at the same apical size. Statistical analysis was carried out with Mann-Whitney test, paired t-test and independent sample t-test. CONCLUSIONS: Significant reduction in CFU was achieved after the root canal preparation completed with 2.5% NaOCl irrigation, both with stainless steel hand or nickel-titanium rotary files. The root canal remained slightly infected after chemo mechanical preparation in both groups. Key words:Chemomechanical preparation, root canal disinfection, nickel-titanium, conicity, greater taper, apical size.