Antibacterial activity of porphyrin derivatives against multidrug-resistant bacteria.

In this study, it was aimed to investigate the antibacterial activities of the cationic porphyrin derivatives against some multi drug resistant clinical bacterial isolates and standard strains for the development of potential antibacterial agents. In addition to the standard strains, methicillin-resistant Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa clinical isolates were studied. We synthesized eight (P1-P8) cationic porphyrin derivatives. The minimum inhibitory concentrations (MIC) of these substances were determined by micro dilution method. Ciprofloxacin was used for quality control. The study was repeated three times. All porphyrin derivatives exhibited antibacterial activity at different levels according to the studied bacteria. The strongest antibacterial activity was obtained with compounds P6, P7 and P8. These compounds were found to have MIC values of <5-156µg/ml. Because of the low MIC values, it has been concluded that these synthesized porphyrin derivatives may be high-potency agents against bacteria with high resistance profile.

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.

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.

The antibacterial activity of photodynamic agents against multidrug resistant bacteria causing wound infection.

Antimicrobial photodynamic inactivation (aPDI) of multidrug-resistant (MDR) wound pathogens was evaluated with cationic porphyrin derivatives (CPDs). MDR bacterial strains including Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, and Klebsiella pneumoniae were used. The CPDs named PM, PE, PN, and PL were synthesized as a photosensitizer (PS). A diode laser with a wavelength of 655 nm was used as a light source. aPDI of the combinations formed with different energy densities (50, 100, and 150 J/cm²) and PS concentrations (ranging from 3.125 to 600 µM) were evaluated on each bacterial strain. Dark toxicity, cytotoxicity, and phototoxicity were determined on fibroblast cells. In the aPDI groups, survival reductions of up to 5.80 log10 for E. coli, 5.90 log10 for P. aeruginosa, 6.11 log10 for K. pneumoniae, and 6.78 log10 for A. baumannii were obtained. The cytotoxic effect of PL and PM on fibroblast cells was very limited. PN was the type of CPD with the highest dark toxicity on fibroblast cells. In terms of providing broad-spectrum aPDI without or with very limited cytotoxic effect, the best result was observed in aPDI application with PL. The other CPDs need some modifications to show bacterial selectivity for use at 50 µM and above.

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 and antimicrobial activity of some pyridinium salts.

Some substituted benzylidenehydrazinylpyridinium derivatives bearing benzyl, ethylphenyl and propylphenyl groups on the pyridinium nitrogen were synthesized and screened for possible antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans using the microdilution method. Antimicrobial test results indicated that compounds containing a 3-phenylpropyl chain displayed the highest antimicrobial activity against Staphylococcus aureus and the compound 3d was the most active in the series against all tested bacteria and fungi strains.

[In vitro activity of linezolid/ertapenem combination in resistant gram-positive bacteria]. / Dirençli gram-pozitif bakterilerde linezolid/ertapenem kombinasyonunun in vitro aktivitesi.

The increasing prevalence of vancomycin-resistant enterococcus and methicillin-resistant staphylococcus infections has become a major therapeutic challenge and alternative therapy options are under consideration. In the present study, we aimed to evaluate the in vitro antibacterial activity of linezolid combined with ertapenem against two vancomycin-resistant Enterococcus faecium (VREF), two methicillin-resistant Staphylococcus aureus (MRSA) and two methicillin-resistant Staphylococcus epidermidis (MRSE) strains isolated from clinical specimens. In vitro activity of linezolid/ertapenem combination at 1/2 x MIC (minimal Inhibitory Concentration), 1 x MIC and 4 x MIC concentrations for each of the isolates was determined by time-kill curve method. At 1 x MIC and 4 x MIC concentrations, additive effect was detected for MRSA (at 6 and 24 h) and VREF (at 6 h) strains. Synergism was observed between two antibiotics at 4 x MIC concentration against one of the MRSE strains at 6th hour. Additive effect was determined at 6th and 24th hours in this strain at 1 x MIC concentration. No synergism was present in the other MRSE strain but additive interaction was detected at 6 h (1/2 x MIC) and 24 h (1 x MIC). Although these results support the use of linezolid/ertapenem combination in infections caused by resistant gram-positive strains, further in vitro and in vivo studies are necessary.

[Extended spectrum beta-lactamase types in Klebsiella pneumoniae strains isolated from blood cultures]. / Kan kültürlerinden izole edilen Klebsiella pneumoniae suslarinda genislemis spektrumlu beta-laktamaz varliginin arastirilmasi ve tiplendirilmesi.

The aim of this study was to investigate and type the extended spectrum beta-lactamases (ESBL) in Klebsiella pneumoniae strains isolated from blood cultures. Following the detection of antibiotic susceptibilities in 32 K. pneumoniae isolates, ESBL were detected in 13 (41%) of them by using double disc synergy test. Minimum inhibition concentrations for ceftazidime, cefotaxime, and aztreonam of ESBL positive strains were determined by E-test. After the extraction of the enzymes, the types of ESBLs were investigated by isoelectric focusing method. It was seen that, of all ESBL positive strains, one strain had four bands, one had three bands, six strains had two bands, and each of the others had only one beta-lactamase band. The results of polymerase chain reaction (PCR) revealed bla(SHV) in ten samples, bla(TEM) in six samples, and bla(SHV) with bla(TEM) in four samples. Ten SHV enzymes were typed as ESBL by PCR-RFLP (restriction fragment lenght polymorphism) method. The results of isoelectric focusing, PCR and RFLP performed in these ESBL positive K. pneumoniae isolates showed that the ESBL types could be SHV-2, SHV-5 and SHV-12 in the tested strains. It should always be taken into consideration that K. pneumoniae isolates could produce ESBLs and antibiotic treatment protocols should be adjusted in accordance.

Photodynamic antimicrobial activity of new porphyrin derivatives against methicillin resistant Staphylococcus aureus.

Methicillin resistant Staphylococcus aureus (MRSA) with multiple drug resistance patterns is frequently isolated from skin and soft tissue infections that are involved in chronic wounds. Today, difficulties in the treatment of MRSA associated infections have led to the development of alternative approaches such as antimicrobial photodynamic therapy. This study aimed to investigate photoinactivation with cationic porphyrin derivative compounds against MRSA in in-vitro conditions. In the study, MRSA clinical isolates with different antibiotic resistance profiles were used. The newly synthesized cationic porphyrin derivatives (PM, PE, PPN, and PPL) were used as photosensitizer, and 655 nm diode laser was used as light source. Photoinactivation experiments were performed by optimizing energy doses and photosensitizer concentrations. In photoinactivation experiments with different energy densities and photosensitizer concentrations, more than 99% reduction was achieved in bacterial cell viability. No decrease in bacterial survival was observed in control groups. It was determined that there was an increase in photoinactivation efficiency by increasing the energy dose. At the energy dose of 150 J/cm2 a survival reduction of over 6.33 log10 was observed in each photosensitizer type. While 200 µM PM concentration was required for this photoinactivation, 12.50 µM was sufficient for PE, PPN, and PPL. In our study, antimicrobial photodynamic therapy performed with cationic porphyrin derivatives was found to have potent antimicrobial efficacy against multidrug resistant S. aureus which is frequently isolated from wound infections.

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.

Molecular characterization of TEM- and SHV-derived extended-spectrum beta-lactamases in hospital-based Enterobacteriaceae in Turkey.

TEM- and SHV-derived extended-spectrum beta-lactamases (ESBLs) producing Enterobacteriaceae have been reported from throughout the world, but there has been limited data for the molecular characterization of these enzymes in Turkey. The aim of this study was to investigate and to type the TEM- and SHV-derived ESBLs in 63 ESBL-producing clinical isolates of Enterobacteriaceae, and it included further analysis; transfer experiments, isoelectric focusing, PCR, PCR-restriction fragment length polymorphism, and DNA sequencing. According to PCR results the transconjugant strains included 52.7% TEM, 74.3% SHV, and 32.4% of both the TEM and SHV genes. Using PCR/NheI restriction analysis, 45 of the 46 ESBL detected in transconjugants were determined to be SHV-derived. DNA sequencing was performed for the identification of TEM- and SHV-derived ESBLs for 18 selected transconjugants. SHV-2, SHV-5, and SHV-12 were detected in five, seven, and five samples, respectively. This is the first description of SHV-12 in Turkey.

Prevalence of blaPER-1 and integrons in ceftazidime-resistant Gram-negative bacteria at a university hospital in Turkey.

In this study, we examined the prevalence of the PER-1 enzyme and the presence of clinically important integron classes in ceftazidime-resistant Gram-negative bacteria isolated at a university hospital. The blaPER-1 gene was detected by PCR in 33 (19.5%) of the total 169 Gram-negative bacteria, including 17 (23.3%) of the 73 Pseudomonas aeruginosa isolates and 16 (25%) of the 64 Acinetobacter baumannii complex isolates. Molecular fingerprinting revealed that blaPER-1 prevalence was mostly due to the dissemination of clonally related P. aeruginosa and A. baumannii complex strains. Class 1 integron (intI1) was detected in 52.7% of the 169 bacteria examined in this study. Its detection rates were estimated at 49.3% and 57.8% of the P. aeruginosa and A. baumannii complex strains isolated, respectively. It was also detected in 11 of the 16 Escherichia coli isolates and 5 of the 10 Klebsiella pneumoniae isolates. A single E. coli isolate and another K. pneumoniae isolate contained both class 1 and class 2 integrase genes. The results of this study revealed that clonally related blaPER-1-positive P. aeruginosa and A. baumannii complex strains, mostly harboring intI1, had disseminated at our hospital.