Detecting imipenem resistance in Acinetobacter baumannii by automated systems (BD Phoenix, Microscan WalkAway, Vitek 2); high error rates with Microscan WalkAway

<p>Abstract</p> <p>Background</p> <p>Increasing reports of carbapenem resistant <it>Acinetobacter baumannii </it>infections are of serious concern. Reliable susceptibility testing results remains a critical issue for the clinical outcome. Automated systems are increasingly used for species identification and susceptibility testing. This study was organized to evaluate the accuracies of three widely used automated susceptibility testing methods for testing the imipenem susceptibilities of <it>A. baumannii </it>isolates, by comparing to the validated test methods.</p> <p>Methods</p> <p>Selected 112 clinical isolates of <it>A. baumanii </it>collected between January 2003 and May 2006 were tested to confirm imipenem susceptibility results. Strains were tested against imipenem by the reference broth microdilution (BMD), disk diffusion (DD), Etest, BD Phoenix, MicroScan WalkAway and Vitek 2 automated systems. Data were analysed by comparing the results from each test method to those produced by the reference BMD test.</p> <p>Results</p> <p>MicroScan performed true identification of all <it>A. baumannii </it>strains while Vitek 2 unidentified one strain, Phoenix unidentified two strains and misidentified two strains. Eighty seven of the strains (78%) were resistant to imipenem by BMD. Etest, Vitek 2 and BD Phoenix produced acceptable error rates when tested against imipenem. Etest showed the best performance with only two minor errors (1.8%). Vitek 2 produced eight minor errors(7.2%). BD Phoenix produced three major errors (2.8%). DD produced two very major errors (1.8%) (slightly higher (0.3%) than the acceptable limit) and three major errors (2.7%). MicroScan showed the worst performance in susceptibility testing with unacceptable error rates; 28 very major (25%) and 50 minor errors (44.6%).</p> <p>Conclusion</p> <p>Reporting errors for <it>A. baumannii </it>against imipenem do exist in susceptibility testing systems. We suggest clinical laboratories using MicroScan system for routine use should consider using a second, independent antimicrobial susceptibility testing method to validate imipenem susceptibility. Etest, whereever available, may be used as an easy method to confirm imipenem susceptibility.</p

DETERMINATION OF HEPATITIS B VIRUS GENOTYPES BY DNA SEQUENCE ANALYSIS IN PATIENTS FROM ANKARA, TURKEY

WOS: 000277896300010PubMed: 20549959Hepatitis B virus (HBV) genotypes vary depending on the geographical region. The HBV genotype determined in Turkey has been genotype D which is found as the homogenously disseminated single genotype The aim of this study was to determine HBV genotypes in a group of HBV infected patients who were admitted to a university hospital in Ankara, Turkey Serum samples from HBsAg positive and anti-HBs negative 84 (52 male, 32 female) patients with HBV infection were included into the study. Anti-HBc was positive in 95 2%, HBeAg was positive in 47.6% and anti-HBe was positive in 11 9% of the patients. Mean HBV-DNA levels of the patients were 5.7 x 10(7) +/- 4 6 x 10(7) IU/ml, mean ALT levels were 131 +/- 171 IU/ml and mean AST levels were 98 +/- 170 IU/ml. HBV-DNA was extracted from serum by the phenol-chloroform method and PCR was performed to amplify the S gene region of HBV-DNA Cycle sequencing of PCR products was performed by a commercial "Cy5/Cy5.5 Dye Primer Cycle Sequencing Kit" (Visible Genetics, Canada) based on dideoxy chain termination method The sequences were read and analyzed in an automated fluorescence-based DNA-sequencing system (Long-Read Tower System, Visible Genetics, Canada) The nucleotide sequences of the patient samples were compared with the previously reported sequences in gene bank for each genotype According to the comparative analysis of S-sequences of all patient samples with the published sequences of the genotypes in gene bank, all of the 84 hepatitis B strains (100%) were shown to be related to D genotypic group, subtype ayw. A phylogenetic analysis was performed and phylogenetic trees were constructed using programs in the PHYLIP phylogeny inference package The patient samples clustered within the genotypic group D According to these results, the main HBV genotype in our patients was genotype D in accordance with the previous molecular epidemiologic information on HBV in this geographic area HBV genotype determination may help to establish more rational clinical approach in the evaluation of HBV infected patients

EVALUATION OF REDUCED SUSCEPTIBILITY TO VANCOMYCIN AMONG MRSA STRAINS ISOLATED FROM CLINICAL SPECIMENS

WOS: 000277896300021PubMed: 20549970In this study, a total of 390 methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from clinical specimens between April 2004 and June 2008, in a university hospital in Zonguldak (located at Black Sea region), Turkey, were evaluated retrospectively for reduced susceptibility to vancomycin Brain heart infusion (BHI) plates containing 4 and 6 mu g/ml of vancomycin were used to screen for vancomycin intermediate S aureus (VISA) strains Additionally, vancomycin minimal inhibitory concentrations (MIC) of the isolates were determined by agar dilution method No growth was observed on the screen plates after 24 and 48 hours of incubation None of the isolates revealed MIC values equal to or higher than 2 mu g/ml, MIC(90) and MIC(50) values were 1 mu g/ml Although VISA isolates were not detected in this study, no data was obtained for heterogeneous VISA isolates since macro-E test or population analysis were not performed It was concluded that systematic surveillance of MRSA isolates is of particular importance to investigate the presence of VISA/hVISA isolates which may lead to treatment failures and hospital epidemic

HEPATITIS C VIRUS GENOTYPES IN A PROVINCE OF WESTERN BLACK-SEA REGION, TURKEY

WOS: 000284385400013PubMed: 21063977Hepatitis C virus (HCV) is one of the significant causes of hepatitis, cirrhosis and hepatocellular carcinoma all throughout the world. There are six genotypes and more than 50 subtypes of HCV. HCV genotyping is of crucial importance in the determination of the treatment protocols and the follow-up of the clinical course since treatment success is low and the duration of treatment is longer in HCV genotype 1 infected cases. The aim of the present study was to evaluate the HCV genotype profiles of the patients with chronic hepatitis C in Zonguldak, providing the first data about HCV genotypes from western Black-Sea region, Turkey. The HCV genotypes of 44 patients (26 female, 18 male; age range: 29-89 years, mean age: 60.05 +/- 10.81 years) with positive anti-HCV antibody and HCV-RNA results, admitted to the hospital between May 2007 and July 2009, were retrospectively evaluated and included in the study. Alanine aminotransferase (ALT) levels of the patients were between 8-160 IU/L (mean 63.99 +/- 37.15 IU/L) and the aspartate aminotransferase (AST) levels were between 17-160 IU/L (mean 62.77 +/- 36.75 IU/L). HCV antibody was determined by ELISA method (Abbott Laboratories, USA), and HCV-RNA was determined by two commercial real-time polymerase chain reaction systems [Cobas Taqman (Roche Diagnostic, USA) and Rotor-Gene 6000 (Corbett Research, USA)]. The genotyping was performed by a reverse hybridization based method, Versant (R) HCV Genotype Assay (LiPA) 2.0 (Bayer Health Care, Belgium). HCV genotypes could not be determined for 5 (11.4%) patients since HCV-RNA levels were low. Genotyping could be performed for 39 (88.6%) patients and 38 (97.4%) had genotype 1b and one (2.6%) patient had genotype la. In conclusion, in concordance with the other studies conducted in our country, genotype 1b was found to be the most prevalent genotype in patients from our region

Investigation of OprD Porin Protein Levels in Carbapenem-Resistant Pseudomonas aeruginosa Isolates

Conclusions: Although the data support the idea that the basic mechanism of imipenem resistance could be via the loss of oprD, they do not fully explain the role of oprD and indicate that other mechanisms may play an important role. Additionally, the significant decrease in the oprD levels in MDR strains suggests that oprD also plays a role in the emergence of both carbapenem and non-carbapenem resistance

Investigation of OprD Porin Protein Levels in Carbapenem-Resistant Pseudomonas aeruginosa Isolates

Background: The Pseudomonas aeruginosa porin OprD is a substrate-specific porin that facilitates the diffusion of basic amino acids, small peptides, and carbapenems into the cell. OprD-mediated resistance occurs as a result of decreased transcriptional expression of oprD and/or loss of function mutations that disrupt protein activity. Objectives: In this study, we examined the level of oprD expression in P. aeruginosa clinical isolates to determine the contribution of OprD porins in carbapenem resistance. Materials and Methods: Included strains were divided into two groups, comprised of multidrug-resistant (MDR) and isolated carbapenem-resistant (ICR) strains. The transcription product level of oprD was identified using real-time polymerase chain reaction (qPCR). Results: Of the 18 clinical isolates, a decrease in the oprD level was found to be significant in 13 isolates. Nine of eighteen isolates with a significant decrease were determined in the first group and comprised MDR isolates that showed a statistically significant difference compared with the ICR group (P = 0.001). In the ICR group, oprD levels were found to be significantly low in 4 isolates. Six different patterns were determined by comparing band profiles in AP-PCR. Conclusions: Although the data support the idea that the basic mechanism of imipenem resistance could be via the loss of oprD, they do not fully explain the role of oprD and indicate that other mechanisms may play an important role. Additionally, the significant decrease in the oprD levels in MDR strains suggests that oprD also plays a role in the emergence of both carbapenem and non-carbapenem resistance. © 2015, Ahvaz Jundishapur University of Medical Sciences

Fecal Carriage of Extended Spectrum Beta-Lactamase (ESBL)-Producing Escherichia coli and Klebsiella spp. in Children in Zonguldak

WOS: 000488951800011Introduction: The aim of this study was to determine the prevalence of fecal carriage of extended-spectrum beta-lactamase (ESBL)-producing bacteria, ESBL enzyme types, and risk factors affecting colonization in children. Materials and Methods: Stool specimens of 0-15 years old children admitted to the pediatric outpatient clinic for any reason between October 2012-December 2013 were evaluated. Demographic data of the patients were collected through a questionnaire. Patients samples were cultured on selective EMB agar plates. The presence of ESBL was investigated by double disc synergy test and agar gradient test was used when necessary. Enzyme types of the isolates were determined by polymerase chain reaction (PCR). Results: The prevalence of fecal carriage was determined as 33% (150 of 454). Of the 154 ESBL-producing bacteria, 142 (92.2%), 11 (57.1%), and 1 (0.6%) were E. coil, K. pneumoniae and K. oxytoca, respectively. Of the ESBL-producing bacteria, 92.8% were positive for bla(CTX-M)genes. Of the bla(CTX-M) gene-positive isolates, 81.1% were positive for bla(CTX-M-)(15)( )and 94.4% were positive for bla(CTX-M-3) genes while 62.5% isolates were positive for both bla(CTX-M-3) and bla(CTX-M-15) genes. No significant association was demonstrated between carriage rates and the questioned risk factors. Conclusion: A high rate (33%) of fecal carriage of ESBL bacteria was found in the child population of Zonguldak. No significant association was demonstrated between carriage rates and the questioned risk factors. Predominant beta-lactamase enzyme types were CTX-M group while CTX-M-3 and CTX-M-15 were the most common enzyme types

Causative Agents of Intravenous Catheter-Related Infections and Their Antibiotic Susceptibilities

WOS: 000287635700011PubMed: 21341163Intravenous catheterization can lead to colonization as well as a broad spectrum of infections ranging from catheter site infections to catheter-related blood stream infections (CRBSIs). The aim of this study was to evaluate the distribution of causative agents and their antibiotic susceptibility patterns in CRBSIs and catheter site infections along with the colonization rates and colonizing microorganisms in Zonguldak Karaelmas University Hospital, Turkey. The results of cultures from catheter tips and/or intracatheter blood cultures and simultaneously taken peripheral blood cultures were sent to medical microbiology laboratory and were retrospectively investigated for 201 patients hospitalized between September 2007 and September 2009. The catheter tips were cultured by semi-quantitative and quantitative culture methods. Blood cultures from the catheters and peripheral veins were performed in BACTEC 9120 (Becton Dickinson, USA) blood culture systems. The antibiotic susceptibility tests were done by Kirby-Bauer disk diffusion method according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Out of 201 patients included, 28 (13.9%) had CRBSIs and 13 (6.4%) had catheter site infections while colonization was defined for 55 (27.3%) patients. Of 28 patients with CRBSIs, Acinetobacter spp. were isolated from 11 including five carbapenem-resistant strains, methicillin-resistant coagulase-negative staphylococci (MRCNS) from eight, methicillin-susceptible coagulase-negative staphylococci (MSCNS) from two, Klebsiella pneumoniae from two patients and one of each patient's cultures yielded methicillin-resistant Staphylococcus aureus (M RSA), carbapenem-resistant Pseudomonas aeruginosa, Enterococcus spp., Escherichia coli and MRCNS + Enterococcus faecium. Of 13 patients with catheter site infections, five MSCNS, two methicillin-susceptible S.aureus (MSSA), two E.coli, and one of each K.pneumoniae, MRCNS, Enterococcus spp., K.pneumoniae + P.aeruginosa were isolated. No resistance to vancomycin and teicoplanin were detected among the staphylococci isolated from CRBSIs and catheter site infections. The distribution of the 55 colonizing microorganisms were as follows; 18 MSCNS, 18 MRCNS, four Acinetobacter spp., five K.pneumoniae, three E.coli, two MSSA, and one of each MRSA, P.mirabilis, P.aeruginosa, Corynebacterium spp., Candida albicans. In this study, the predominant microorganism isolated from CRBSIs was Acinetobacter spp., followed by coagulase-negative staphylococci. This unexpected distribution of the agents was related to the Acinetobacter spp. that have gained endemic potential following an Acinetobacter outbreak in our hospital in 2006. We emphasize that it is critical for any individual hospital to assess periodically the distribution and susceptibility profiles of isolates obtained from catheter-related infections to set out rational empirical treatment strategies