Işın Akyar

Evaluation of the MALDI TOF-MS method for identification of Candida strains isolated from blood cultures

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI TOF-MS) allows rapid and accurate identification of microorganisms. It is being used increasingly and becoming an important tool in clinical laboratories. Phenotypic identification of Candida species remains labor- and time consuming, and the results may sometimes be inconclusive. Rapid and reliable species identification of Candida is essential for antifungal treatment due to species-specific susceptibility patterns. In this study, we evaluated the performance of MALDI TOF-MS for identification of Candida strains. A total of 281 clinical Candida strains isolated from blood cultures were included in this study. Candida species were identified with conventional methods and automated VITEK 2 YST panels as well as with MALDI TOF-MS. Isolates with discrepant results were subjected to DNA sequencing of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2). Ninety-four percent of the isolates were identified correctly by VITEK 2 and MALDI TOF-MS. Altogether, MALDI-TOF MS yielded the correct species identification for 281 (100%) clinical Candida isolates. MALDI-TOF proved to be a rapid and reliable method for identification of Candida strains in the clinical laboratory.

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

BackgroundIncreasing reports of carbapenem resistant Acinetobacter baumannii 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 A. baumannii isolates, by comparing to the validated test methods.MethodsSelected 112 clinical isolates of A. baumanii 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.ResultsMicroScan performed true identification of all A. baumannii 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%).ConclusionReporting errors for A. baumannii 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.

Leishmaniasis in Turkey: first clinical isolation of Leishmania major from 18 autochthonous cases of cutaneous leishmaniasis in four geographical regions.

To report isolation of Leishmania major strains obtained from 18 Turkish autochthonous cutaneous leishmaniasis (CL) patients infected with L. major between 2011 and 2014.

The use of Matrix-assisted laser desorption ionization-time of flight mass spectrometry in the identification of Francisella tularensis

Francisella tularensis is the cause of the zoonotic disease tularemia and is classified among highly pathogenic bacteria (HPB) due to its low infection dose and potential for airborne transmission. In the case of HBP, there is a pressing need for rapid, accurate and reliable identification. Phenotypic identification of Francisella species is inappropriate for clinical microbiology laboratories because it is time-consuming, hazardous and subject to variable interpretation. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was recently evaluated as a useful tool for the rapid identification of a variety of microorganisms. In this study, we evaluated the use of MALDI-TOF MS for the rapid identification of Francisella tularensis and differentiation of its subspecies. Using national collection of Francisella isolates from the National Tularemia Reference Laboratory (Public Health Institution of Turkey, Ankara), a total of 75 clinical isolates were investigated by species and subspecies-specific polymerase chain reaction (PCR) test and MALDI-TOF MS. All isolates were originally identified as F. tularensis subsp. holarctica according to region of difference 1 (RD1) subspecies-specific PCR results. For all isolates MALDI-TOF MS provided results in concordance with subspecies-specific PCR analysis. Although PCR-based methods are effective in identifying Francisella species, they are labor-intensive and take longer periods of time to obtain the results when compared with MALDI-TOF MS. MALDI-TOF MS appeared to be a rapid, reliable and cost-effective identification technique for Francisella spp. Shorter analysis time and low cost make this an appealing new option in microbiology laboratories.

Six-year distribution pattern of hepatitis C virus in Turkey: a multicentre study

ABSTRACT Hepatitis C infection is a public health problem. The aim of this retrospective study was to determine the distribution of hepatitis C virus (HCV) genotypes in seven regions of Turkey, by evaluating 7002 patients with chronic HCV in a six-year period. During the 2009–2014 period, serum/plasma samples from 7002 new consecutive HCV RNA positive patients were collected. The female patients were 3867 (55.2%). The genotype distribution of HCV patiens was evaluated by ages and years. Statistical analysis was performed by using the Mann–Whitney test and the χ2 analysis. During the six-year period, genotype 1b was the most common genotype (67.7%) followed by untypeable genotype 1 (7.7%), genotype 4 (7.3%) and genotype 3 (6.7%). In 2014, genotype 3 was the second most common one (11.3%) and genotype 4 was the third most common one (9.8%). In the group with <25 years old patients, genotype 1b was most common (78.48%, 62/79) between the years of 2009 and 2011, whereas genotype 3 (34.8%, 86/247), between the years of 2012 and 2014. Genotype 1b was the most common in the groups between 26 and 35 years, 36 and 45 years, 46 and 55 years, 56 and 65 years. The rate of genotype 3 was increased from 4.78% to 10.06% and the rate of genotype 4 was increased from 1.3% to 3.84%, from 2009–2011 to 2012–2014. In recent years, genotypes 3 and 4 have gained importance. New therapeutic strategies and survey studies may be required for the modified HCV genotype pattern.

Evaluation of the Carba NP Test for the Detection of Carbapenemase Activity in Bacteroides Species

We evaluated the usefulness of the Carba NP test for rapid detection of carbapenemase activity in Bacteroides spp. The minimum inhibitory concentration (MIC) for imipenem was determined with gradient test strips, and cfiA gene was investigated by polymerase chain reaction for 27 clinical Bacteroides spp. isolates. Carba NP test was performed according to recommendations of the Clinical and Laboratory Standards Institute. Among three cfiA gene harboring clinical isolates, two imipenem resistant isolates were Carba NP test positive, while the imipenem intermediate isolate was negative. Our preliminary results suggest that the Carba NP test can be useful as a rapid test to detect carbapenemases in Bacteroides species.

Comparison of Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry with VITEK2 Gram Positive System for Identification of Beta Haemolytic Streptococci

Background: Matrix–assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is known as a successful tool for bacterial identification and suitable for clinical diagnostics. The aim of our study was to evaluate diagnostic accuracy of MALDI-TOF MS system and VITEK2 Gram Positive Identification (GP ID) system for the identification of Beta Hemolytic Streptococci (BHS). Materials and Methods: A total 148 BHS which were isolated from various clinical specimens were included in the study. Isolates were identified by Bruker Biotyper 3.4 and VITEK2 GP ID coupled to the agglutination test. Identification results for Bruker Biotyper 3.4 and VITEK2 GP ID systems were classified in three different categories as follows: correct identification, low level of discrimination, no identification/misidentification. Identification results of BHS were evaluated according to these categories. Results: BHS isolates were defined as Streptococcus pyogenes (n: 69), Streptococcus agalactiae (n: 59), Streptococcus dysgalactiae serogroup C (n: 5), and Streptococcus dysgalactiae serogroup G (n: 15) according to latex agglutination assay. MALDI-TOF MS analysis of 148 BHS isolates yielded correct identification for 89.9% of S. pyogenes , 64.4% of S. agalactiae , and 95.0% S. dysagalactiae serogroup C and G; while VITEK2 GP ID gave correct identification for 62.3% of S. pyogenes , 67.8% of S. agalactiae , and 65.0% of S. dysagalactiae serogroup C and G. Conclusions: MALDI-TOF MS-based identification provides faster and more accurate identification of beta-hemolytic streptococcal species than VITEK2 GP ID system.

Chapter 12 – Food Pathogens

This chapter introduces the basic principles and concepts of mass spectrometry (MS) in the detection of food pathogens. Frequent and sporadic outbreaks of food-related illness linked to foodborne pathogens are of increasing concern to public health officials, the food industry, and society. The frequency and endurance of such outbreaks point to the urgency in developing rapid, robust, and accurate methods to identify and characterize these sometimes deadly microorganisms. Pathogens most frequently associated with outbreaks of foodborne illness are Escherichia coli, Salmonella, Listeria monocytogenes, Campylobacter, and Norovirus. Because of its speed, sensitivity, and specificity, mass spectrometry (MS) is increasingly used for rapid microbial identification via detection and/or identification of biomolecules—typically proteins, peptides, nucleotides, or DNA but also lipids—that are highly specific for the microorganism that produced them.

[Amoebic liver abscess in a patient initially diagnosed with pneumonia: case report and discussion of relevant literature].

In one-third of the patients with amoebiasis, amoebic liver abscess (ALA) may occur after the penetration of amoebic trophozoites through the intestinal wall. ALA is seen mostly among men aged 20-45 years with a serious clinical outcome, with fever and abdominal pain on the right upper quadrant. Most patients have no recent history of amoebic colitis; indeed, they have neither gastrointestinal complaints nor Entamoeba histolytica (E. histolytica) cysts/trophozoites in their stools. Therefore, ultrasonography and serology are primary in ALA diagnosis, while searching for E. histolytica DNA in abscess fluid using PCR has been preferred as an effective and reliable method, lately. Early antimicrobial therapy is effective; however, for cases irresponsive to therapy after 72 hours and with large abscess, drainage or surgical intervention is indicated. If left untreated, ALA may disseminate to other organs and cause death. The data concerning the extra-intestinal manifestations of amebiasis in Turkey are limited. Here, a rare case of a young man with an initial diagnosis of pneumonia followed by the identification of ALA after radiological interventions and laboratory tests is presented and the relevant literature is discussed.