Effect of Predator Bacteria Bdellovibrio bacteriovorus on Clinical Pathogens and Biofilms.

Antimicrobial resistance has become one of the most important public health problems of our century. In addition to the spread of resistance, biofilm production also makes the treatment of infections increasingly difficult. Therefore, this study, it was aimed to investigate the effect of the predator bacterium Bdellovibrio bacteriovorus HD100 on various clinical pathogens and their biofilms. A large panel of Gram-positive and negative clinical isolates were included in the study. The double-layer agar method was used to optimize the cultivation of predatory bacteria. The effectiveness of Bdellovibrio bacteriovorus HD 100 on planktonic cells and biofilms, was determined by co-culture and crystal violet staining methods, respectively. The antibiofilm activity was also visualized via scanning electron microscopy. The predator bacteria was found effective against most of the Gram-negative isolates. But it was determined that the lowest activity among these isolates was shown to Pseudomonas aeruginosa and Acinetobacter baumannii. Although it is known that B. bacteriovorus does not predate on Gram-positive isolates, interestingly, Staphylococci species included in this study were found to be inhibited in co-culture studies. As determined in co-culture and biofilm studies, B. bacteriovorus can be used to control both bacterial growth and biofilms in most Gram-negative species. Interestingly, our data also suggest that predatory bacteria may also be effective against Gram-positive bacterial biofilms in addition to Staphylococcus aureus. Although the evaluation of different species of isolates in this study demonstrates the potential of predatory bacteria, the host specificity and the relation of prey and predator need to be demonstrated. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-023-01071-y.

In vitro effects of ciprofloxacin, levofloxacin and moxifloxacin on Mycobacterium tuberculosis isolates.

INTRODUCTION: Increased tuberculosis prevalence, and isolation of multidrug resistant (MDR) Mycobacterium tuberculosis strains frequently as causative organisms from tuberculosis infections are resulted in increasing need of new anti-tuberculosis drugs. Nowadays, fluoroquinolones known to have fewer side effects than the other drugs used in treatment of tuberculosis are sometimes assessed even as first-line anti-tuberculosis drugs due to their in vitro and in vivo strong activity. It was aimed in this study to investigate phenotypically the fluoroquinolone susceptibility in MDR and non-MDR M. tuberculosis isolates. MATERIALS AND METHODS: A total of 126 MDR and non-MDR M. tuberculosis isolates from mycobacteriology laboratory of two hospitals in the Aegean Region of Turkey were included in the study. Ciprofloxacin (CIP), levofloxacin (LEV) and moxifloxacin (MXF) susceptibilities were assessed by agar proportion method according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. RESULT: Twelve (15.2%), 5 (6.3%) and 4 (5.1%) of the MDR M. tuberculosis strains were resistant to CIP, LEV, MXF, respectively [resistance breakpoints (µg/mL); CIP (> 2), LEV (> 1), MXF (> 0.5)] while non-MDR strains were susceptible to CIP, LEV, MXF. CONCLUSIONS: Consequently, although high fluoroquinolone susceptibilities were evaluated as a pleasing data in this study, to preserve their efficiency for many years steadily, quinolone usage and resistance increment in MDR M. tuberculosis isolates should be monitored elaborately.

Analyses of Plasmids Harbouring Quinolone Resistance Determinants in Enterobacteriaceae Members.

The aim of this study was to explore the plasmid characteristics of eight clinical Enterobacteriaceae strains containing extended broad spectrum beta-lactamases and plasmid-mediated quinolone resistance. Plasmids were transferred by conjugation or transformation and resistance determinants were investigated by PCR. We showed that at least one plasmid harbouring qnrB or qnrS determinant was transferred by conjugation in five isolates. QepA determinant was confirmed to be on a non-conjugative plasmid. We found at least one beta-lactamase gene in seven of the eight clinical isolates having plasmid-mediated quinolone resistance, which indicated that these two resistance determinants were mostly on the same conjugative plasmids.

[Comparison of phenotypic methods and polymerase chain reaction for the detection of carbapenemase production in clinical Klebsiella pneumoniae isolates]. / Klinik Klebsiella pneumoniae izolatlarinda karbapenemaz üretiminin saptanmasinda polimeraz zincir reaksiyonu ve fenotipik yöntemlerin karsilastirilmasi.

Being a member of the Enterobacteriaceae family, Klebsiella pneumoniae is an opportunistic pathogen that inhabits normal human microbiota and causes predominantly hospital-acquired infections. The emergence of K.pneumoniae isolates which are resistant particularly to the carbapenem group of antibiotics has led to an increase in hospitalization period, mortality and morbidity. Although different rates of resistance are observed between countries, regions and even healthcare facilities, there has been a rapid increase in the prevalence of carbapenem-resistant strains in the last 10 years. Fast and correct identification of carbapenem-resistant strains is important for the successful treatment of infections caused by these resistant bacteria. The objective of this study was to investigate the presence and the types of carbapenemases in carbapenem-resistant K.pneumoniae strains using "MASTDISCS™ ID carbapenemase detection disc set", a commercial product that can be used for this purpose, and "Carbapenem Inactivation Method (CIM)", a relatively new method, and compare the results of these methods by polymerase chain reaction (PCR). For this purpose, we used 54 K.pneumoniae strains isolated in 2015-2016, that were resistant to any of the ertapenem, meropenem or imipenem antibiotics. The identification of the strains was performed using VITEK MS and their antibiotic susceptibility tests were carried out using the VITEK 2 Compact® automated system. For the strains that were found resistant to carbapenems in the automated system, the minimum inhibitor concentration (MIC) values were determined by the gradient testing method according to the recommendations of "The European Committee on Antimicrobial Susceptibility Testing (EUCAST)". The blaOXA-48, blaIMP, blaNDM, blaVIM, and blaSIM genes were investigated with PCR among these isolates. Phenotypic enzyme typing was performed in the carbapenem-resistant strains using the "MASTDISCS™ ID carbapenemase detection disc set" and "Carbapenem Inactivation Method (CIM)". REP-PCR was used to reveal clonal relationship of the isolates. The 54 K.pneumoniae isolates were found as resistant to carbapenem and the MIC50 and MIC90 values of imipenem, meropenem and ertapenem were 32 µg/ml. Only 33 of the strains had blaOXA-48 and two of them had only blaNDM, the remaining 19 strains had both of these two genes. The blaIMP, blaVIM and blaSIM genes were not encountered in any of the isolates. When the isolates were assessed by the REP-PCR method, six main clones were detected. The "MASTDISCS™ ID carbapenemase detection disc set" was able to detect all the carbapenemase producing strains and it remained incapable of distinguishing OXA-48 in the strains which had both OXA-48 and metallo beta lactamase (MBL) enzymes. The CIM method showed a low rate of positivity (46.15%) in the strains containing blaOXA-48, but was found much more successful in the strains containing blaNDM with a detection rate of 85.71%. In this study, it was concluded that the Mastdiscs-ID method could be successfully used to detect the presence of blaOXA-48 which has a high prevalence in our country.

Genotype distribution of Mycobacterium tuberculosis in theAegean Region and associated demographic factors

Background/aim: The Aegean Region is the second-ranking region in Turkey according to the Human Development Index and population density and it hosts 1/8 of Turkey's population. Izmir is the largest city of the region, receiving internal migration both from inside and outside the region. The tuberculosis incidence in Izmir is lower than overall in Turkey: 17.7/100,000 in 2011. Our aims were to determine genotypes of Mycobacterium tuberculosis isolates; to explore possible associations between genotypes with case-demographic data, clinical presentation, and antimicrobial susceptibility patterns; and to determine variations in genotype distribution of strains isolated in Ege University Hospital, Izmir. Materials and methods: Forty-nine M. tuberculosis isolates from 49 patients in 1996-2000 and 421 M. tuberculosis isolates from 421 patients in 2009-2014 were spoligotyped. Drug susceptibility testing and demographic data of the 421 isolates were investigated. Chi-square, Student's t, and Mann-Whitney U tests were used for analyses. Results: Among the 470 M. tuberculosis strains, 132 different spoligopatterns were identified and 46 different clusters for 384 strains were determined. The most predominant spoligotypes were ST53 (n = 116; 24.7%) and ST41 (n = 38; 8.1%), followed by ST50 (5.7%), ST284 (4.7%), and ST4 (4.3%), respectively. ST53 was the most predominant type in both sexes. Multidrug resistance (MDR) was determined in 12 isolates, of which six were ST1.Conclusion: As a consequence of worldwide migration and increasing status of HIV-infected hosts, the increasing prevalence of Beijing strains with higher MDR rates may threaten disease control programs. With its increasing trend, ST284 could replace ST41 in the following years in this region.

Gamma scintigraphy and biodistribution of (99m)Tc-cefotaxime sodium in preclinical models of bacterial infection and sterile inflammation.

(99m)Tc-cefotaxime sodium ((99m)Tc-CEF) was developed and standardized under varying conditions of reducing and antioxidant agent concentration, pH, radioactivity dose, and reducing agent type. Labeling studies were performed by changing the selected parameters one by one, and optimum labeling conditions were determined. After observing the conditions for maximum labeling efficiency and stability, lyophilized freeze dry kits were prepared accordingly. Simple method for radiolabeling of CEF with (99m)Tc has been developed and standardized. Labeling efficiency of (99m)Tc-CEF was assessed by both radio thin-layer chromatography and radio high-performance liquid chromatography and found higher than 90%. The labeled compound was found to be stable in saline and human serum up to 24 h. Two different freeze dry kits were developed and evaluated. Based on the data obtained from this study, both products were stable for 6 months with high labeling efficiency. The prepared cold kit was found sterile and pyrogen free. The bacterial infection and sterile inflammation imaging capacity of (99m)Tc-CEF was evaluated. Based on the in vivo studies, (99m)Tc-CEF has higher uptake in infected and inflamed thigh muscle than healthy thigh muscle.

(99m) Tc-Doxycycline hyclate: a new radiolabeled antibiotic for bacterial infection imaging.

Radiolabeled antibiotics are promising radiopharmaceuticals for the precise diagnosis and detection of infectious lesions. Doxycycline Hyclate (DOX) was chosen to investigate new (99m) Tc-labeled antibacterial agent. Ready to use freeze dry kits were formulated with optimum labeling conditions. Human serum stability, sterility, and pyrogenicity of kits were estimated, and gamma scintigraphy, in vivo biodistribution, and histopathological studies with bacterial infected rats were performed. DOX were successfully labeled by (99m) Tc with high radiochemical purity, and the labeled compound was stable in human serum. Kits were sterile, pyrogen-free, and stable up to 6 months. Static images depicted rapid distribution throughout the body and high uptake in bacterial infected thigh muscle. The uptake ratios of radiopharmaceuticals in infected thigh muscle were found above 2 up to 5 h. Five hours after injection, the rats were sacrificed, and biodistribution was determined. Samples of bacterial infected muscle, healthy muscle, blood, liver, spleen, lung, kidney, stomach, intestine, urine and heart were weighed, and the radioactivity was measured by using a gamma counter. The %ID/g of (99m) Tc-DOX was found 0.23 ± 0.06 for infected thigh muscle. According to the imaging, biodistribution, and histopathological studies, the promising characteristics of (99m) Tc-DOX make the new radiopharmaceutical valuable to examine for future studies.

[Investigation of the virulence factors of multidrug-resistant Acinetobacter baumannii isolates]. / Çok ilaca dirençli Acinetobacter baumannii izolatlarinda virülans faktörlerinin arastirilmasi

Acinetobacter baumannii is an opportunistic human pathogen which causes life-threatening nosocomial infections such as ventilator-associated pneumonia, bacteremia, meningitis, urinary tract and wound infections. Treatment options are very limited for infections caused by multi-drug resistant (MDR) A.baumannii strains. Until recently, the majority of studies related to A.baumannii have focused on antibiotic resistance, treatment protocols and epidemiological data, however, there have been few studies addressing the virulence factors of this organism. The features such as biofilm formation, serum resistance, motility, efflux pumps and iron acquisition mechanisms help the bacterium to survive in adverse environmental conditions and facilitate the development of an infection. The aim of the present study was to investigate the basic characteristics that contribute to the virulence of clinically important MDR A.baumannii isolates. Sixty-five ciprofloxacin-imipenem-trimethoprim/sulfamethoxazole-resistant A.baumannii strains isolated from various clinical specimens between December 2011 and March 2012 at Ege University Faculty of Medicine, Department of Medical Microbiology were included in the study. The clonal relationship of the isolates was analyzed by PCR using Enterobacterial repetitive intergenic consensus (ERIC)-2 primer. Biofilm formation, serum resistance, twitching and swarming motility, efflux pump and siderophore production were sought in representatives of each clone. Investigated MDR A.baumannii isolates were classified into seven main clusters, and the largest cluster included 86% of the strains. The virulence-associated features were investigated in 16 representative strains, including sub-groups. Twelve, three and one of the examined strains were determined to be strong, intermediate and weak biofilm producers, respectively. Siderophore production was not encountered in any of the isolates. Of the sixteen strains, two, one and thirteen isolates were found to be resistant, moderately susceptible and susceptible to bactericidal effect of serum, respectively. In our study, swarming motility was observed in seven strains while twitching motility was observed in only one strain. Swarming was simultaneously detected with twitching in one isolate. The presence of an efflux pump was investigated with ciprofloxacin in 16 representative strains but none of them were positive. However, eflux pump was determined in two of the five doxycycline resistant strains. Biofilm production was the most commonly observed characteristic among the examined strains. In addition, serum resistance, swarming and an efflux pump which has a spectrum including tetracyclines, were also determined among features associated with virulence. While the biofilm production was encountered at the members of all clones, serum resistance was found only in the representatives of the most dominant clone. Motility and the presence of an efflux pump were not associated with a particular clone. MDR A.baumannii strains are among the most important agents of nosocomial infections in our hospital and all over the world. Revealing the characteristics that play a role in the pathogenesis of these isolates, will contribute to infection control measures and to the investigation of new treatment options.

Synthesis and antileishmanial activity of novel pyridinium-hydrazone derivatives.

A series of substituted phenylethylidenehydrazinylpyridinium derivatives bearing methyl, ethyl, propyl, and propylphenyl groups on the pyridinium nitrogen were synthesized and evaluated for in vitro antileishmanial activity against Leishmania tropica by using the microdilution method. Among the tested compounds, 3d, 5c, 3b, and 3c were found to be the most active derivatives against the promastigotes of L. tropica (IC50 values are 6.90, 9.92, 11.69 and 12.03 µM, respectively) and to be more active than reference drug meglumine antimonaite (glucantime) (IC50 value: 20.49 µM). The derivatives investigated in this study may have the potential to be lead compound against leishmanial infection.

Tigecycline susceptibility in multidrug resistant Acinetobacter isolates from Turkey.

The present study aimed to evaluate antimicrobial activity of tigecydcline against 84 multidrug resistant (MDR) Acinetobacter spp. strains by disc diffusion and E-test methods. The results of disc diffusion test were compared according to two different interpretation ways. In addition, E-test results and the disc diffusion results that interpreted by both the methods were checked for compatibility. According to the disc diffusion test, 3 strains (3.57%) were found resistant to tigecycline when considering breakpoints suggested by Food and Drug Administration (FDA). On the other hand, none of the strains was found resistant to the evaluation criteria recommended by Jones etal. (2007). Considering E-test results of tigecycline, MIC, and MICG, values of tigecycline for Acinetobacter spp. were 0.75 and 1 mg/l, respectively. Based on FDA defined breakpoints for Enterobacteriaceae, any resistant isolate was detected. In conclusion, although there are some differences in the results, tigecycline was found quite effective on Acinetobacter spp. isolates with reference to the both disc diffusion and the E-test methods.

Carbapenemase investigation with rapid phenotypic test (RESIST-4 O.K.N.V) and comparison with PCR in carbapenem-resistant Enterobacterales strains.

Background and Objectives: RESIST-4 O.K.N.V. assay is a lateral immunochromatocraphic test for the identification of oxacillinase (OXA)-48-like, Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-ß-lactamase (NDM), and Verona integron-encoded metallo-ß-lactamase (VIM) producing strains. It was aimed to evaluate the performance of the RESIST-4 O.K.N.V. test and to compare it with the reference method polymerase chain reaction (PCR). Also, the objective was to determine the distribution of carbapenemase types of CRE strains isolated in our hospital. Materials and Methods: Between January 2016-October 2019, 187 strains isolated from clinical samples were included in this study. Bacterial identification was done using MALDI-TOF MS. Antibiotic susceptibility tests were studied with the VITEK-2 automated system. Meropenem minimum inhibitory concentrations (MICs) were determined by the gradient test. All strains were studied with the RESIST-4 O.K.N.V. test and then the strains were selected for the PCR test. bla OXA-48, bla NDM, bla KPC, and bla VIM were investigated with PCR. K. pneumoniae NCTC® 13438 (KWIKSTIKTM, Microbiologics®, USA) was used as the positive control, E. coli ATTC® 25922 TM (Microbiologics®, USA) and three carbapenem-sensitive clinical isolates were also used as the negative control. Results: Meropenem MIC50 and MIC90 values were determined to be >32 mg/L. With PCR bla OXA-48, bla NDM, bla KPC and bla VIM were detected in 79, 63, 20, and 4 strains, respectively. bla OXA-48 and bla NDM were found together in 51 of the isolates. bla OXA-48, bla NDM, bla KPC, and bla VIM were not detected in two strains with carbapenem resistance in susceptibility tests. The sensitivity of the immunochromatographic test was 100% for OXA-48, KPC, and VIM but 84.1% for NDM. Specificity was determined as 100% for OXA-48, NDM, KPC, and VIM. Conclusion: RESIST-4 O.K.N.V. test showed high sensitivity and specificity in detecting OXA-48, KPC, NDM, and VIM type carbapenemases. However, it should be kept in mind that there may be false-negative results related to NDM.

Silencing acpP gene via antisense oligonucleotide-niosome complex in clinical Pseudomonas aeruginosa isolates.

Pseudomonas aeruginosa, an opportunistic Gram-negative pathogen, is one of the major causes of nosocomial infections. In addition to its physiological adaptation capacity, it can develop resistance to disinfectants and antibiotics through various mechanisms. Recently, new eradication methods are gaining attention. Therefore, in this study, an LNA-2'-O-methyl hybrid antisense oligonucleotide targeting the acyl carrier protein P (acpP) gene was introduced into P. aeruginosa isolates. The design was determined through sequence analysis and prediction of the secondary structure of mRNA by software. Niosomes were used for enhancing cellular uptake. The control of the binding and transfection ability of the sequence was determined fluorometrically by labeling with 6-Fam. The effects were determined with broth microdilution method and qPCR studies. Eight different formulations were prepared. Among these, one formulation has shown to have ASO complexation ability whose composition was 312 µl Span 80 + 69.5 mg Cholesterol+ 36.4 mg CTAB+1 ml Chloroform and 5 ml dH2O. Thus this formulation was determined as the delivery system for the next stages. Significant gene inhibition was detected at the six isolates. Results of this study suggested that niosomes can be used as a delivery system for cellular uptake of ASO and could eliminate bacterial growth.

Effects of disinfectants and ciprofloxacin on quorum sensing genes and biofilm of clinical Pseudomonas aeruginosa isolates.

BACKGROUND: Pseudomonas aeruginosa is one of the most virulent bacteria and quorum sensing (QS) genes have an importance on virulence factors such as biofilm that provide resistance against disinfectants and antibiotics. OBJECTIVE: This study aimed to determine the minimum inhibitory concentrations of the disinfectants, to investigate the effects of disinfectants and ciprofloxacin on biofilm production mature biofilm of clinical P. aeruginosa isolates, and it was aimed to investigate the effects of the agents on the expression levels of several QS-related genes in the isolates. METHODS: Minimum inhibitory concentration (MIC) levels of polyhexamethylene biguanide (PHMB), chlorhexidine (CHX), quaternary ammonium compounds (QAC), glutaraldehyde (GLU) and ciprofloxacin (CIP) against clinical P. aeruginosa isolates were evaluated by microdilution method. Effects of the agents on the biofilm producing capacities of clonally unrelated nine strains were investigated by spectrophotometric method. Alterations in the expression of QS-related genes (lasI, lasR, rhlI and rhlR) were investigated by qPCR in three isolates that were CIP-susceptible and strong biofilm producer. RESULTS: According to microdilution method results, three isolates were found as resistant, one isolate was found as intermediate susceptible and five isolates were found as susceptible to CIP, and CHX (7.81-31.25 µg/mL) had the lowest MIC against P. aeruginosa. CHX inhibited biofilm production levels of eight of nine isolates, and GLU and CIP inhibited six of nine isolates in the presence of agents at MIC levels. GLU inhibited the mature biofilm levels of three of nine isolates at MIC and MIC/4 levels and four of nine isolates at MIC/2 levels. Expression levels of QS-related genes were reduced or induced in the presence of different disinfectants. CONCLUSIONS: More efforts are required to decrease the risk of ineffective and low-dose application of disinfectants and antimicrobials against bacteria. Targeting of QS-related genes may be a reasonable strategy for the inhibition of virulence factors in P. aeruginosa.

Antifungal and Antibiofilm Activities of Selective Serotonin Reuptake Inhibitors Alone and in Combination with Fluconazole.

OBJECTIVES: Candida spp. are clinically important pathogens that cause difficulties for treatment by biofilm formation. Considering antifungal resistance rates and the limitations in the discovery of new antifungals, the antifungal and antibiofilm effects of various drugs used for different therapeutic purposes are becoming more important. The goal of our study was to determine the antifungal and antibiofilm effects of the selective serotonin reuptake inhibitors (SSRIs), namely sertraline (SRT), paroxetine (PRX), and fluoxetine (FLX) alone and in combination with fluconazole (FLC) against Candida spp. MATERIALS AND METHODS: Twenty Candida spp. strains isolated from clinical samples from Ege University Hospital were identified by the Dalmau method and matrix-assisted laser desorption ionization time of flight mass spectrometry. The minimum inhibitory concentrations (MICs) of the SSRIs and FLC were detected by broth microdilution method. Synergistic interactions between the SSRIs and FLC were investigated by checkerboard assay. The antibiofilm effects of the SSRIs were determined by spectrophotometric microplate method. RESULTS: Among the isolates, five different Candida spp. (C. albicans, C. glabrata, C. krusei, C. tropicalis, and C.parapsilosis) were identified. The MICs of the SSRIs ranged between 16-512 µg/mL. While SRT showed the highest antifungal effect, the antibiofilm efficacy of FLX was higher than that of the other agents. Moreover, FLX and PRX showed a synergistic effect with FLC in 13 and 19 isolates, respectively. Four isolates were strong biofilm producers while nine isolates were moderate biofilm producers. C. parapsilosis strains showed higher biofilm production than the other species. At MIC/2 concentration, FLX and SRT alone inhibited mature biofilms in six and five isolates, respectively, while PRX caused increases biofilm formation in seven isolates. CONCLUSION: This study revealed that MIC/2 concentrations of SSRIs could have antifungal and antibiofilm effects. SRT and FLX alone or in combination with antifungals may possibly have therapeutic potential for combating fungal infections.

In vitro activity of linezolid against Mycobacterium tuberculosis strains isoalted from Western Turkey.

We investigated the linezolid susceptibility of Mycobacterium tuberculosis strains isolated from a tertiary care hospital in Izmir. A total of 67 M. tuberculosis strains (33 multidrug-resistant [MDR] and 34 non-MDR) were isolated and identified by the Tuberculosis Laboratory, Department of Microbiology and Clinical Microbiology, Faculty of Medicine, Ege University. The activity of linezolid was studied by the standard agar proportion method. For all of the strains, the MIC range was 0.06-1 mg/L, and the MIC(50) and MIC(90) values were 0.5 mg/L. No differences were observed between the MDR and non-MDR isolates. In general, linezolid was found to be effective for both the non-MDR and MDR M. tuberculosis strains.

Synthesis of new water-soluble ionic liquids and their antibacterial profile against gram-positive and gram-negative bacteria.

A series of imidazolium bromide salts (NIM-Br 1a, 1b and 1c) bearing different lengths of alkyl chains were synthesized and theirin vitro antibacterial activities were determined by measuring the minimum inhibitory concentration (MIC) values for Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. In addition, these imidazolium derivatives were also evaluated against biofilm produced by these bacterial strains. All compounds were found to be effective against Gram-positive and Gram-negative bacteria, and also more effective on the S. aureus biofilm production than the others.

Investigation of the Antimicrobial Susceptibility Profile, Virulence Genes, and Epidemiologic Relationship of Clinical Salmonella Isolates.

OBJECTIVES: The objectives of this study were to investigate the epidemiologic relationship, prevalence of the beta-lactamase and virulence genes of clinical ampicillin-resistant Salmonella enterica. MATERIALS AND METHODS: In vitro ampicillin susceptibilities of 117 Salmonella enterica isolates obtained between 2011-2012 from Ege University Hospital, Bacteriology Laboratory of Medical Microbiology Department were examined using disc diffusion assays in accordance with the CLSI guidelines. The MIC levels in the ampicillin-resistant bacteria were determined using the broth microdilution method. The resistant strains were serotyped by the Public Health Institution. Epidemiologic relations of resistant strains were evaluated using ERIC-PCR. The presence of beta-lactamase genes and virulence factors were detected using PCR. RESULTS: The 117 S. enterica strains had ten isolates that were resistant to ampicillin, and the MIC range of ampicillin was found as 512-128 µg/mL. Ampicillin-resistant strains were susceptible to nalidixic acid, ciprofloxacin, cefotaxime, sulfamethoxazole/trimethoprim. Four different serotypes were identified and isolates were grouped into seven clusters. Five isolates carried blaTEM , and two carried the blaCTX-M gene. However, it was determined that blaSHV and blaPER genes did not exist in these strains. Virulence genes invA, pipD, and sopB were found in all isolates. sifA, pefA, and sopE genes were found in seven, four, and three isolates, respectively. CONCLUSION: Our data suggest that the rate of ampicillin resistance in S. enterica isolates was 8.5% in the two year period, but this ratio was generally lower than rates abroad. blaCTX-M and blaTEM genes could be responsible for ampicillin resistance. The blaSHV gene, which is highly prevalent in our country, was not found in any strains. sopB and pipD genes, which might be associated with beta-lactam resistance, were found in all strains. It is also noteworthy that the three isolates containing the sopE gene, which is associated with epidemic cases, were of the same serotypes and epidemiologic clusters.

The post-antibiotic effects of linezolid against Gram-positive pathogens.

OBJECTIVE: To investigate the post-antibiotic effect (PAE) of linezolid against methicillin-resistant and -susceptible staphylococci, vancomycin-resistant and -susceptible enterococci. METHODS: Clinical strains of Staphylococcus aureus (S. aureus), Staphylococcus epidermidis (S. epidermidis) and Enterococcus faecalis (E. faecalis) were isolated from hospitalized patients at Ege University Medical Faculty Hospital between June and September 2005. This study was made between September and December 2005. The PAE of linezolid was determined at the minimum inhibitory concentration (MIC) and 4 times the MIC concentrations for 60 minutes in Mueller-Hinton Broth (MHB). The duration of the PAE was obtained by following the recovery of bacterial growth in antibiotic free MHB measured colony forming units on Mueller-Hinton agar. RESULTS: All the straines were susceptible to linezolid. The PAE was greater at 4 times the MIC (0.5 - 2.4 hours) that at the MIC (0 - 1.7 hours) for linezolid against all organisms tested. The PAE for linezolid was slightly higher against E. faecalis strains than other organisms. CONCLUSION: In this study, it was demonstrated that linezolid had a moderate in vitro PAE against S. aureus, S. epidermidis and E.faecalis strains.

[Investigation of glycopeptide resistance in methicillin resistant staphylococcal isolates]. / Metisiline dirençli stafilokok izolatlarinda glikopeptid direncinin arastirilmasi.

The emergence of Staphylococcus aureus strains with intermediate resistance (VISA) and heterogen resistance (hVISA) to vancomycin leads to the occurence of severe therapeutic problems. The aim of this study was to investigate the vancomycin resistance in methicillin resistant S. aureus (MRSA) and coagulase-negative staphylococci (MRCoNS) isolated from clinical samples in Bacteriology Laboratory of Microbiology and Clinical Microbiology Department of Celal Bayar University Faculty of Medicine, Manisa (located in western Anatolia, Turkey). A total of 120 staphyloccoccal strains (92 MRSA and 28 MRCoNS) isolated from different clinical specimens (tracheal aspirate, blood, abscess, wound swabs, sputum, catheter tips, etc) between the period of June 2005 to December 2006 were included to the study. Vancomycin resistance were determined by agar screening method using brain hearth infusion agar plates containing 6 microg/mL vancomycin. Standard E-test and macro E-test methods were performed for 17 (14%) staphylococcal strains (10 MRSA and 7 MRCoNS) which had grown in agar screening plates. Vancomycin and teicoplanin minimal inhibitory concentration (MIC) ranges of those strains were found as 1.5-4 microg/mL and 2-4 microg/mL, respectively, by standard E-test method. In our study, no VISA and hVISA isolates were detected when MIC value of > or =8 microg/mL for vancomycin and teicoplanin, or > or =12 microg/mL for teicoplanin only were accepted as the criteria for hVISA determination. Agar screening method which is preferably used in routine laboratories for practical and economical reasons, lower sensitivity and specificity than E-test. It can be concluded that, since agar screening method is not reliable for the detection of vancomycin resistance, further multi-center studies with the use of standard methods are needed in order to clarify the vancomycin resistance patterns of staphylococci in our country.

DNA-wrapped multi-walled carbon nanotube modified electrochemical biosensor for the detection of Escherichia coli from real samples.

This paper introduces DNA-wrapped multi-walled carbon nanotube (MWCNT)-modified genosensor for the detection of Escherichia coli (E. coli) from polymerase chain reaction (PCR)-amplified real samples while Staphylococcus aureus (S. aureus) was used to investigate the selectivity of the biosensor. The capture probe specifically recognizing E. coli DNA and it was firstly interacted with MWCNTs for wrapping of single-stranded DNA (ssDNA) onto the nanomaterial. DNA-wrapped MWCNTs were then immobilised on the surface of disposable pencil graphite electrode (PGE) for the detection of DNA hybridization. Electrochemical behaviors of the modified PGEs were investigated using Raman spectroscopy and differential pulse voltammetry (DPV). The sequence selective DNA hybridization was determined and evaluated by changes in the intrinsic guanine oxidation signal at about 1.0V by DPV. Numerous factors affecting the hybridization were optimized such as target concentration, hybridization time, etc. The designed DNA sensor can well detect E. coli DNA in 20min detection time with 0.5pmole of detection limit in 30µL of sample volume.