Halil Yazgi

Detection of antimicrobial resistance and extended-spectrum β-lactamase production in Klebsiella pneumoniae strains from infected neonates

The present study was designed to determine the antimicrobial resistance and extended-spectrum β-lactamase (ESBL) activities of Klebsiella pneumoniae strains isolated from the neonatal intensive care unit of Atatürk University Hospital, Erzurum, Turkey. Antibiotic susceptibility of 40 isolates was detected by the standard disk diffusion method according to the National Committee for Clinical Laboratory Standards Guidelines. The double-disk synergy method was used to determine ESBL activity, which is associated with resistance to β-lactam antibiotics. Twenty-four (60%) of 40 K. pneumoniae strains were found to produce ESBL. Of the antibiotics tested, meropenem was found to be the most effective (100%), and ampicillin the least effective (0%). With the increasing incidence of antimicrobial resistance, which poses a clinically significant risk to vulnerable patients, it is important that clinical microbiology laboratories have accurate and timely information concerning the strains of bacteria present to enable them to predict which antibiotics are likely to be effective in treating the infections they may cause.

A Comparison of High-Level Aminoglycoside Resistance in Vancomycin-Sensitive and Vancomycin-Resistant Enterococcus Species

The aim of this study was to investigate whether there was a significant difference in high-level aminoglycoside resistance (HLAR) between vancomycin-sensitive enterococci (VSE) and vancomycin-resistant enterococci (VRE). Vancomycin resistance was determined in 116 Enterococcus isolates using brain-heart infusion agar containing 6 μg/ml vancomycin. HLAR was determined by both standard agar screening and disk diffusion methods. Streptomycin and gentamicin were used as predictors of HLAR. Vancomycin resistance and HLAR were found in 17 (14.7%) and 41 (35.3%) of the Enterococcus strains, respectively. HLAR was found in 11 of 17 VRE and 30 of 98 VSE strains. HLAR in VRE strains was significantly higher than in VSE. More enterococcal strains were found to be resistant to both gentamicin and streptomycin (29) than to gentamicin (one) or streptomycin (11) alone. The HLAR rate in VRE was two-fold higher than in VSE. The synergistic bactericidal effect of aminoglycosides and β-lactam or glycopeptide antibiotics is lost if there is high-level resistance to aminoglycosides.

Demonstration of In Vitro Antagonism between Fusidic Acid and Quinolones

Fusidic acid is an antibiotic active against staphylococci and other bacterial pathogens. It is used in the treatment of staphylococcal infections usually in combination with other antibacterial agents. Reports of the clinical effects of antimicrobial combinations containing fusidic acid have been somewhat inconsistent. The aim of this study was to investigate the in vitro antagonism of fusidic acid and quinolones. Twenty-six staphylococci strains isolated from various clinical samples were tested. After detecting the diameter of the zone of inhibition around fusidic acid, levofloxacin, ciprofloxacin, ofloxacin and moxifloxacin for each strain, in vitro antagonism between fusidic acid and each quinolone was investigated using disk approximation. In all 26 strains, quinolones and fusidic acid were antagonist in vitro. The reason for this antagonistic effect and its clinical implications are not known. However, care should be exercised in prescribing quinolones and fusidic acid in combination.

Comparison of coagulase-negative staphylococci isolated from blood cultures as a true bacteremia agent and contaminant in terms of slime production and methicillin resistance.

OBJECTIVE The aim of this study is to determine the species distribution, slime activity, and methicillin resistance of coagulase-negative staphylococci (CoNS) isolated from blood cultures as either contaminants or true bacteremia agents. MATERIALS AND METHODS In this study, 13.268 blood culture samples sent to our laboratory from various clinics during a two-year period were examined in terms of the presence of CoNS to clarify whether the isolates are true bacteremia agents, as defined by Centers for Disease Control and Prevention (CDC) criteria. The slime activities of true bacteremia agents (58 CoNS strains) and contaminants (50 randomly selected CoNS strains) were investigated by the Christensen method. The methicillin susceptibilities of the strains were determined by the disk diffusion method. RESULTS Although the frequency of slime production was 39.7% among the true bacteremia CoNS agents, it was 18% in CoNS that were judged to be contaminants (p<0.05). S. epidermidis was the most frequently isolated species for both the true bacteremia agent group (56.9%) and contaminant group (74%). Additionally, S. epidermidis was the bacterium most frequently characterized as slime producing in both groups. The methicillin resistance of slime-producing CoNS was determined to be 82.6% for the true bacteremia agent group and 77.8% for the contaminant group. CONCLUSION The presence of slime activity in CoNS isolated from blood culture samples is supportive evidence that they are most likely the agents of true bacteremia cases.

Investigation of Helicobacter pylori antigen in stool samples of patients with upper gastrointestinal complaints

Helicobacter pylori infection is usually acquired in early childhood and it can persist throughout life without antibiotic treatment. This study aimed to compare the accuracy of the noninvasive H. pylori Stool Antigen Test-applied on the stool samples with the invasive gold standart Rapid Urease Test-applied on the gastric biopy samples of patients with upper gastrointestinal complaints. After endoscopy, biopsy and stool specimens were taken in 122 patients. The infection was detected with rapid urease test which is accepted as gold standart test. Rapid, one-step H. pylori card test was applied to all patients stool specimens. In this study 106 of the 122 patients (86.8%) were positive for H. pylori infection, while 16 of the 122 patients (13.2%) were negative. H. pylori card test was negative in 13 of the 16 patients and was positive in 98 of the 106. The sensitivity, specifity, positive and negative predictive values were 92.45%, 81.25%, 97.02%, and 61.90%, respectively. H. pylori card test is rapid, easy, noninvasive and inexpensive methods for detection H. pylori infection. This test showed high sensitivity and specificity. Additionally, it may be a good alternative to invasive tests for the detection of H. pylori infections especially in children.

Comparison of Slime-producing Coagulase-negative Staphylococcus Colonization Rates on Vinyl and Ceramic Tile Flooring Materials

This study investigated the colonization of slime-producing coagulase-negative Staphylococcus (CoNS) in 80 patient wards in Turkey (40 vinyl and 40 ceramic tile floors). A total of 480 samples that included 557 CoNS isolates were obtained. Slime production was investigated with the Christensen method and methicillin-susceptibility was tested by the diskdiffusion method. There was a significant difference in the percentage of slime-producing CoNS isolates on vinyl (12.4%) versus ceramic tile flooring (4.4%). From vinyl flooring, the percentage of slime producing methicillin-resistant CoNS (MRCoNS) (8.9%) was significantly higher than for methicillin-sensitive CoNS (MSCoNS) (3.6%), whereas there was no difference from ceramic tile flooring (2.5% MRCoNS versus 1.8% MSCoNS). The most commonly isolated slime-producing CoNS species was S. epidermidis on both types of flooring. It is concluded that vinyl flooring seems to be a more suitable colonization surface for slime-producing CoNS than ceramic tile floors. Further studies are needed to investigate bacterial strains colonized on flooring materials, which are potential pathogens for nosocomial infections.

Atypical Colony Morphology of Staphylococcus lugdunensis Isolated from a Wound Specimen.

The incidence of infections due to coagulase-negative staphylococci (CoNS) has been steadily increasing in recent years. In this report, we describe an isolate of the CoNS Staphylococcus lugdunensis from a wound specimen with a colony morphology distinct from that of a classical S. lugdunensis colony. Specifically, wrinkled, medium-sized, beta hemolytic, opaque, rough white colonies were detected on blood agar. Catalase-positive, coagulase-negative, gram-positive cocci-yielding such colonies should be suspected of being S. lugdunensis.