Phenotypic and genotypic evaluation of fluoroquinolone resistance in clinical isolates of Staphylococcus aureus in Tehran

Background: Fluoroquinolones are broad-spectrum antibiotics widely used in the treatment of bacterial infections such as Staphylococcus aureus isolates. Resistance to these antibiotics is increasing. Material/Methods: The occurrence of mutations in the grlA and gyrA loci were evaluated in 69 fluoroquinolone-resistant S. aureus isolates from 2 teaching hospitals of Tehran University of Medical Sciences. Results: Out of the 165 S. aureus isolates, 87 (52.7) were resistant to methicillin and 69 (41.8) were resistant to fluoroquinolone. Fluoroquinolone-resistant S. atoms isolates had a mutation at codon 80 in the grlA gene and different mutational combinations in the gyrA gene. These mutational combinations included 45 isolates at codons 84 and 86,23 isolates at codons 84,86 and 106 and 1 isolate at codons 84, 86 and 90. Fluoroquinolone-resistant S. aureus isolates were clustered into 33 PFGE types. Conclusions: The findings of this study show that the fluoroquinolone-resistant S. aureus strains isolated in the teaching hospitals in Tehran had multiple mutations in the QRDRs region of both grlA and gyrA genes

Study of Pseudomonas Aeroginosa resistance to Penicillines, Cephalosporins and Aminoglycosides

Drug therapy and prophylaxy in infectious diseases, from hygienic and economical point of view, are very important. Infections caused by pseudomonas aeroginosa were particularly severe, with high mortality rates. In the recent years pseudomonas aeroginosa continued to cause the most severe, life-thereating infections in burned patients, in spite of the introduction of a wide variety of antibiotics advised specifically for their anti pseudomonal activity. The aim of this study, in which many cases of ps.aeroginosa infections are assessed is to identify the drug resistance of this bacteria to penicillines, cephalosporins and aminoglycosides by antibiotic sensitivity test (disk ager diffusion). Results as percent of resistance to each antibiotic were 89% to carbenicillin, 55% to piperacillin, 89% to mezlocillin, 89.5% to ticarcillin+clavulonic acid, 85% to ceftriaxone, 95% to tobramycin, 5% of all isolates were not sensitive to any antibiotics

Evaluation of biofilm production and characterization of genes encoding type III secretion system among Pseudomonas aeruginosa isolated from burn patients

Pseudomonas aeruginosa is one of the common pathogenic causes of serious infections in burn patients throughout the world. Type III secretion toxins are thought to promote the dissemination of P. aeruginosa from the site of infection, the bacterial evasion of the host immune response and inhibition of DNA synthesis leading to host cell death. A total of 96 isolates of P. aeruginosa were collected from wound infections of burn patients, from April to July 2010. Antimicrobial susceptibility of the isolates were determined by disk agar diffusion method. Polymerase chain reaction (PCR)-based method was used for targeting the genes encoding the type III secretion toxins. The quantitative determination of biofilm-forming capacity was determined by a colorimetric microtiter plate assay. All the isolates were resistant to cefixime and ceftriaxone. More than 90 of the isolates were resistant to amikacin, carbenicillin, cefepime, cefotaxime, cefpodoxime, gatifloxacin, gentamicin, piperacillin/tazobactam, ticarcillin and tobramycin. All the isolates carried the exoT gene, 95 carried exoY, 64.5 carried exoU and 29 carried the exoS gene. Most of the isolates (58) carried both exoY and exoU genes while 24 showed the concomitant presence of exoS and exoY and 1 carried both exoS and exoU. Coexistence of exoS, exoY and exoU was seen in 4 of the isolates. Biofilm formation was seen in more than 96 of the isolates among which 47 were strong biofilm producers, 26 were moderate and 22.9 were weak biofilm formers. In conclusion, the findings of this study show that the genes, particularly the exoU gene, encoding the type III secretion toxins, are commonly disseminated among the P. aeruginosa strains isolated from burn patients. (c) 2012 Elsevier Ltd and ISBI. All rights reserved

Frequency of Alloicoccus otitidis, Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae in children with otitis media with effusion (OME) in Iranian patients

Objective: To determine the presence of common bacterial agents of otitis media with effusion (OME), together with investigation these agent in the adenoid tissue and antimicrobial susceptibility pattern of isolated bacteria in Iranian children with OME. Methods: Polymerase chain reaction (PCR) and bacterial culture methods were used for detection and isolation of Alloicoccus otitidis, Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae in 63 middle ear fluid samples and 48 adenoid tissues from 48 OME patients. Fifteen patients were bilaterally affected. Antimicrobial susceptibility of all bacterial isolates were determined by disk agar diffusion (DAD) method. Results: Bacteria were isolated from 47 (n = 30) of the middle ear fluid samples and 79(n = 38) of the adenoid tissue specimens in OME patients. A. otitidis was the most common bacterial isolated from the middle ear fluid 23.8 by culture and 36.5 by PCR method. S. pneumoniae was the most prevalent pathogen (35.5 and 31.2 by culture and PCR) in the adenoid tissues. In 10 patients the same organisms were isolated from the middle ear fluid and adenoid tissue. Antimicrobial susceptibility pattern showed taht most isolates of bacteria were sensitive to ampicillin, Amoxicillin/Clavulanate and fluoroquinolones. Conclusion: The present study, being the first report on the isolation of A. otitidis by culture method in Iran and Asian countries, shows that A. otitidis is the most frequently isolated bacterium in Iranian children having otitis media with effusion. In this study A. otitidis, S. pneumoniae, H. influenzae and M. catarrhalis are the major bacterial pathogens in patients with OME and we found that ampicillin and Amoxicillin/Clavulanate have the excellent activity against bacterial agents in Iranian children with OME. (C) 2011 Elsevier Ireland Ltd. All rights reserved

Molecular characterization of Staphylococcus aureus isolated from children with adenoid hypertrophy: Emergence of new spa types t7685 and t7692

Objective: Adenoids have been associated with the pathogenesis of acute, recurrent and chronic infectious diseases of the upper respiratory system and their hypertrophy is one of the most common causes of upper airway obstruction affecting children. In this study, the characteristics of Staphylococcus aureus isolates from patients who had undergone adenoidectomy were investigated via spa typing method. Methods: A total of 113 children with adenoid hypertrophy who underwent adenoidectomy during September 2009 to November 2010, were included in the study. The isolates were identified to the species level as S. aureus using standard biochemical methods, following which the amplification and sequencing of the spa gene X region were carried out. Results: S. aureus was found in the adenoid tissue of 26 (23) patients. Out of the 26 S. aureus isolates, 5 (19), 3 (11.5) and 3 (11.5) were resistant to tetracycline, erythromycin and oxacillin respectively. All the isolates were susceptible to vancomycin, rifampin, ciprofloxacin, gentamicin, mupirocin and quinupristin-dalfopristin and were typed using spa typing method. All the isolates were found to include 21 spa types, including two previously unreported types (t7685 and t7692). The most prevalent spa types were t7685 (11.5), t230 (8), t325 (8) and t1149 (8). Conclusion: This study demonstrates that the prevalence rate of S. aureus in the adenoid tissue of the children assessed was 23. An interesting point to note was the dominance of the spa type t7685 that has not been previously reported by other studies. (C) 2011 Elsevier Ireland Ltd. All rights reserved

RISK FACTORS IN NEONATAL ANAEROBIC INFECTIONS

Anaerobic bacteria are well known causes of sepsis in adults but there are few studies regarding their role in neonatal sepsis. In an attempt to define the incidence of neonatal anaerobic infections a prospective study was performed during one year period. A total number of 400 neonates under sepsis study were entered this investigation. Anaerobic as well as aerobic cultures were sent. The patients were subjected to comparison in two groups: anaerobic culture positive and anaerobic culture negative and this comparison were analyzed statistically. There were 7 neonates with positive anaerobic culture and 35 neonates with positive aerobic culture. A significant statistical relationship was found between anaerobic infections and abdominal distention and pneumonia. It is recommended for those neonates with abdominal distention and pneumonia refractory to antibiotic treatment to be started on antibiotics with anaerobic coverage

A high prevalence of mupirocin and macrolide resistance determinant among Staphylococcus aureus strains isolated from burnt patients

Infections due to Staphylococcus aureus have become increasingly common among burn patients. The antibiotic resistance profile of S. aureus isolates and inducible resistance against clindamycin were investigated in this study. The presence of mecA gene, mupA gene and macrolide resistance genes were detected using PCR and multiplex-PCR. The resistance rate to methicillin, erythromycin and mupirocin were 58.5, 58 and 40, respectively. The prevalence of constitutive and inducible resistance among macrolide resistant isolates was 75 and 25, respectively. Ninety five percent of the isolates were positive for one or more erm genes. The most common genes were ermA (75), ermC (72) and ermB (69), respectively. The ermA gene predominated in the strains with the inducible phenotype, while ermC was more common in the isolates with the constitutive phenotype. The msrA gene was only found in one MRSA isolate with the constitutive phenotype. A total of 27 isolates (25) carried the mupA gene. All the mupirocin resistant isolates and almost all the erythromycin resistant isolates were also resistant against methicillin which may indicate an outbreak of MRSA isolates with high-level mupirocin and erythromycin resistance in the burn unit assessed. (C) 2011 Elsevier Ltd and ISBI. All rights reserved

A new methodology inspired from the Theory of Critical Distances for determination of inherent tensile strength and fracture toughness of rock materials

Measuring the intrinsic fracture properties of quasi-brittle materials like rocks is of great importance and at the same time a major issue for engineers. In this study, we explore the ability of the Theory of Critical Distances (TCD) to determine accurately both the tensile strength and fracture toughness. To this end, we conduct ring tests and semi-circular bend tests on four rock types including a red sandstone, a white coarse-grained marble, a fine-grained granite and a coarse-grained granite. This selection covers sedimentary, metamorphic and igneous rock types with different grain sizes. The experimental data are analysed using a new methodology developed from the so-called Point Method (PM), a particular form of the TCD, from which we infer the intrinsic tensile strength and the fracture toughness of the studied rock materials. Our results are compared with those obtained from ISRM suggested methodology that is modified to take into account the finite notch root radius used in our experiments. The comparison is successful, supporting that the newly developed methodology is suitable to determine the intrinsic tensile strength and fracture toughness of rock materials.</p

DISTRIBUTION OF BACTERIAL CONTAMINATION IN A TEACHING HOSPITAL IN TEHRAN - A SPECIAL FOCUS ON STAPHYLOCOCCUS AUREUS

There are documents that confirm the cycle of bacterial transmission between patients, staff, and the inanimate environment. The environment may have more effect on intensive care units (ICUs), because the patients who require intensive care have unstable clinical conditions and are more sensitive to infections. The aim of this study was to determine the prevalence of bacteria in air and inanimate surface in the ICUs and to compare the microbial levels to standard levels. Air and inanimate surface in the four ICUs of a teaching hospital underwent weekly surveillance by means of air sampler and swabs for a period of six-month. Total bacterial counts were evaluated onto trypticase soy agar and mannitol salt agar (MSA). A total of 725 samples air (168) and inanimate surfaces (557) were collected. The total mean +/- SD CFU/m(3) of airborne bacteria in all of the ICUs were 115.93 +/- 48.04. The most common bacteria in air of the ICUs were Gram-positive cocci (84.2%). The total mean +/- SD airborne of Staphylococcus aureus was 12.10+/-8.11 CFU/m(3). The highest levels of S. aureus contamination were found in ventilators and bed ledges. More suitable disinfection of hospital environments and monthly rotation in utilization of the various disinfectant agents are needed for the prevention of airborne and inanimate transmission of S. aureus