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

Prevalence of Enteropathogenic and Shiga Toxin-producing Escherichia coli Among Children With and Without Diarrhoea in Iran

The aim of the study was to determine the rates of detection of enteropathogenic Escherichia coli (EPEC) and Shiga toxin-producing E. coli (STEC) strains among children in two randomly-selected populations in Iran. In total, 1,292 randomly-selected faecal samples from children aged less than 10 years were screened for EPEC and STEC. Of the 1,292 cases participated in the study, 184 had diarrhoea, and 1,108 were healthy/asymptomatic children. The conventional culture method and slide agglutination with 12 different commercial EPEC antisera were used for the detection of EPEC. The colony sweep polymyxin- B extraction method, non-sorbitol fermentation (NSF) phenotype, and slide agglutination with O157: H7 antisera were used for the screening and detection of STEC. Of EPEC belonging to 11 different serogroups, O111 and O127 were most commonly found in 36.4% of the diarrhoeal cases and 7.2% of the asymptomatic children. A significant association (p<0.05) was found between isolation of EPEC and diarrhoea. 8.7% of the diarrhoeal cases and 2% of children without diarrhoea were infected with STEC, but none of the isolates belonged to the O157:H7 serotype. A significant association (p<0.05) was found between STEC and diarrhoeal cases. Based on these findings, it can be concluded that different EPEC serogroups may be agents of endemic infantile diarrhoea, and STEC strains are an important enteropathogen among young children

VIRULENCE FACTORS, ANTIMICROBIAL SUSCEPTIBILITY AND MOLECULAR CHARACTERIZATION OF STREPTOCOCCUS AGALACTIAE ISOLATED FROM PREGNANT WOMEN

Forty-one Streptococcus agalactiae isolates collected from pregnant women at 35-37 weeks of gestation were analysed for their capsular types, antimicrobial resistance determinants, distribution of virulence factors and genetic relatedness using PCR and multiplex PCR. Capsular type III was predominant (65.8), followed by capsular type II (14.6), Ib (7.3), and V(4.9). All isolates were susceptible to penicillin, vancomycin, linezolid and quinupristin-dalfopristin. Resistance to tetracycline, erythromycin and clindamycin were found in 97.6, 24.4, and 14.6 of isolates, respectively. The most common antimicrobial resistance gene was tetM found in 97.6 of the isolates followed by ermTR and ermB found in 12 and 7.3 of isolates, respectively. The most common virulence gene was hly (100), followed by scpB (97.6), bca (97.6), rib (53.65) and bac (4.9). The insertion sequence IS1548 was found in 63.4 of isolates. By multi locus variable number of tandem repeat analysis (MLVA) typing, 30 different allelic profiles or MLVA types (MTs) were identified. The most frequent was the MT1 (5/41, 12.2) and followed by MT2 (4/41, 9.75). Our data revealed that population structure of these isolates is highly diverse and indicates different MLVA types

Multiple-locus variable number of tandem repeats (VNTR) fingerprinting (MLVF) and antibacterial resistance profiles of extended spectrum beta lactamase (ESBL) producing Pseudomonas aeruginosa among burnt patients in Tehran

Extended spectrum p-lactamase (ESBL)-producing trait was present in 48 out of the 112 (42.8) Pseudomonas aeruginosa isolates collected from burn wound infections during a 12-month period. The presence of oxa-10, per-1, veb-1 and ges genes and the multiple-locus variable number of tandem repeats (VNTR) fingerprinting (MLVF) of 112 P. aeruginosa strains were determined by PCR and multiplex PCR. Disk diffusion methods were used to determine the susceptibility of the isolates to antimicrobial agents as instructed by CLSI. All ESBL isolates were resistant to aztreonam, cefepime, cefotaxime, cefpodoxime, ceftazidime, ceftriaxone and ofloxacin. Fewer than 60 of ESBL isolates were resistant to imipenem, meropenem, and piperacillin-tazobactam but more than 90 were resistant to amikacin, ciprofloxacin, levofloxacin, ticarcillin and tobramycin. The most prevalent ESBL genes included oxa-10 (70) and per-1 (50) followed by veb-1 (31.3). The gene encodes GES enzyme did not detect in any isolates. A total of 100 P. aeruginosa strains were typed by MLVF typing method. MLVF produced 42 different DNA banding patterns. These data indicate that different MLVF types infect burn wounds in patients at a hospital in Tehran and also suggest an alarming rate of ESBL-producing isolates in this test location. (C) 2011 Elsevier Ltd and ISBI. All rights reserved

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

Genetic similarity between adenoid tissue and middle ear fluid isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis from Iranian children with otitis media with effusion

Background: Otitis media with effusion (OME) is a common disease among children, in the pathogenesis of which bacterial infections play a critical role. It was suggested that adenoid tissue could serve as a reservoir for bacterial infection, the eustachian tubes being the migration routes of bacteria into the middle ear cavity. The aim of this study was to investigate the genetic similarity between isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, obtained from adenoid tissue and middle ear fluid. Methods: A total of 60 specimens of middle ear fluids (MEFs) and 45 specimens of adenoid tissue were obtained from 45 children with OME. All the samples were inoculated on culture media for bacterial isolation and identification. The genetic similarity between bacterial isolates was determined by pulsed-field gel electrophoresis (PFGE). Results: The same bacterial species were simultaneously isolated from adenoid tissue and MEFs of 14 patients, among which, 6 pairs of M. catarrhalis, 5 pairs of S. pneumoniae and 3 pairs of H. influenzae were identified. Conclusions: Based on the genetic similarities between isolate pairs, found by PFGE analysis, this study suggested that M. catarrhalis, S. pneumoniae and H. influenzae colonize the adenoid tissue, then migrate to the middle ear cavity and, hence, contribute to the total pathogenesis of OME. (C) 2013 Elsevier Ireland Ltd. All rights reserved

Molecular analysis of typical and atypical enteropathogenic Escherichia coli (EPEC) isolated from children with diarrhoea

Diarrhoea continues to be one of the most common causes of morbidity and mortality among infants and children in developing countries. To investigate the incidence, antimicrobial resistance and genetic relationships of enteropathogenic Escherichia coli (EPEC) in children with diarrhoea, a total of 612 stool specimens were collected in Tehran, Iran, and cultured to isolate strains of EPEC. The disc diffusion method was used to determine the susceptibility of the isolates according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The presence of eae, stx and bfp-A genes was determined by PCR. The genetic relationships between EPEC isolates were determined by pulsed-field gel electrophoresis (PFGE). Out of the 412 strains of E. coli obtained from 612 diarrhoeal stool specimens, 23 (5.6) were identified as EPEC, of which seven (30.4) were classified as typical strains of EPEC and 16 (69.6) were classified as atypical. Out of the 23 EPEC isolates, 69.5 were resistant to ampicillin, 39.1 were resistant to tetracycline and cotrimoxazole, 30.4 were resistant to cefpodoxime, ceftazidime, ceftriaxone and aztreonam, and 26.1 were resistant to imipenem. The isolates were classified into 21 pulsotypes by PFGE profiles. The present study shows that typical and atypical EPEC isolates displayed considerable heterogeneity in PFGE profiles and EPEC infections were only sporadic in Tehran. Overall 69 of isolates were resistant to at least one of the antibiotics tested

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