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.

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.

Characterization of Alloiococcus otitidis strains isolated from children with otitis media with effusion by Pulsed-Field Gel Electrophoresis.

OBJECTIVE: Alloiococcus otitidis is a slow growing organism which has been isolated in a few studies on patients with otitis media with effusion (OME). According to the literature review, there is no study about the molecular typing of A. otitidis. In this study, the characteristics of A. otitidis isolates from patients with OME were investigated via Pulsed-Field Gel Electrophoresis (PFGE) typing method. METHODS: A total of 50 children with OME, who underwent myringotomy or who had an insertion of a ventilation tube, were included in this study. The isolates were identified to the species level as A. otitidis using standard biochemical methods, following which the amplification and sequencing of the 16S rRNA gene were carried out. The molecular characteristic of A. otitidis was investigated by PFGE technique. RESULTS: Fifteen isolates of A. otitidis were identified in the middle ear fluid of the patients. All the isolates were susceptible to ampicillin, amoxicillin/clavulanate and fluoroquinolones. All of the 15 isolates were typed by PFGE method and were found to include 13 different PFGE types. CONCLUSION: The current study, being the first reports on the molecular typing of A. otitidis by PFGE method, shows that A. otitidis is a heterogenic organism in Iranian children who have OME.

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/m3 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/m3. 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.

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.

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.

Time-kill study and synergistic activity of cell-wall inhibitor antibiotics in combination with gentamicin against Enterococcus faecalis and Enterococcus faecium.

The synergy between gentamicin and vancomycin, teicoplanin, ampicillin and linezolid was studied by time-kill method. Two clinical vancomycin resistant enterococci (VRE) and two vancomycin susceptible enterococci (VSE) isolates were used. Different concentrations of antibiotics were combined. Two VSE strains and the control strain exhibited synergism with the combination of gentamicin, vancomycin, teicoplanin, ampicillin and linezolid. Two VRE strains exhibited synergism with the combination of gentamicin and ampicillin. Synergy between gentamicin and vancomycin, teicoplanin and linezolid was not observed against these isolates. The VRE isolates were positive for vanA, aac (6')-Ie aph (2") and aph (3')-IIIa genes and their vancomycin, teicoplanin and gentamicin MICs were 512 µg/ml, 512 µg/ml and >4000 µg/ml, respectively. In order to treat serious enterococcal infections, further clinical evaluation is needed to examine the in vitro combined effects of gentamicin and vancomycin, teicoplanin and linezolid.

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.

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. aureus 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.

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 ß-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.

Molecular analysis and antimicrobial susceptibility of methicillin resistant Staphylococcus aureus in one of the hospitals of Tehran University of Medical Sciences: high prevalence of sequence type 239 (ST239) clone.

Methicillin-resistant Staphylococcus aureus (MRSA), particularly the multidrug-resistant clones, is an increasing worldwide problem. The average incidence rate of MRSA in Tehran was found to be over 40%. A total of 140 MRSA isolates obtained from patients attending a teaching hospital in Tehran, from May 2009 to December 2009, were included in this study. The antimicrobial susceptibility profile of MRSA isolates was determined by the agar disk diffusion method. Molecular analysis of MRSA strains was accomplished by Pulsed-Field Gel Electrophoresis (PFGE) and Multi-locus sequence typing (MLST). Detection of mecA gene was used to confirm resistance to methicillin among the MRSA isolates. All the MRSA isolates were susceptible to chloramphenicol, teicoplanin, tigecycline and vancomycin. All MRSAisolates were resistant to oxacillin, whilst 139 strains showed resistance against ciprofloxacin, erythromycin, gentamicin, tetracycline and trimethoprim-sulfamethoxazole. PFGE analysis of all the 140 MRSA isolates produced five distinct pulsotypes designated as pulsotypes A-E. Most of the isolates (n=132) were clustered into pulsotype A. The most prevalent sequence type (ST) was ST 239 (pulsotype A) found in 82% (37/45) of the tested isolates. The second most prevalent type was ST 1238 (pulsotypes B, C and D) found in 15% (7/45) of the isolates. The remaining type, ST 8 (pulsotype E) was found in a single isolate. The results of this study indicated that the MRSA clone ST 239 was a major clone in the selected university hospital of Tehran and that it was widely spread among the different wards as well as all the age groups of patients.

Multiple-locus variable number of tandem repeats fingerprinting (MLVF) and virulence factor analysis of methicillin resistant Staphylococcus aureus SCCmec type III.

Methicillin resistant Staphylococcus aureus (MRSA), particularly strains with type III staphylococcal cassette chromosome mec (SCCmec), represent a serious human pathogen in Tehran, Iran. The disease-causing capability depends on their ability to produce a wide variety of virulent factors. The prevalence of exotoxin genes and multiple-locus variable number of tandem repeats fingerprinting (MLVF) profile among MRSA isolates, from patients in Tehran, was evaluated by PCR and Multiplex-PCR. The MLVF typing of 144 MRSA isolates with type III SCCmec produced 5 different MLVF types. Generally, 97.2% (140/144) of all the isolates were positive for at least one of the tested exotoxin genes. The most prevalent genes were hld, found in 87.5% (126/144) of the isolates followed by lukE-lukD and hla found in 72.9% (105/144) and 70.1% (101/144) of the isolates, respectively. The tst gene, belonging to MLVF types I, IV and V, was found among three of the isolates from blood and wound samples. The sea gene was detected in 58.3% (84/144) of the isolates and the sed and see genes were found in one isolate with MLVF type V. The coexistence of genes was observed in the 87.5% (126/144) of the isolates. The rate of coexistence of hld with lukE-lukD, hla with lukE-lukD and sea with lukE-lukD were 66.7% (96/144), 44.4% (64/144) and 44.4% (64/144), respectively. The present study demonstrated that MRSA strains with type III SCCmec show different MLVF patterns and exotoxin profiles.

Antimicrobial resistance of nosocomial strain of Acinetobacter baumannii in Children's Medical Center of Tehran: a 6-year prospective study.

There are increasing reports of emergence of multiple drug resistant (MDR) Acinetobacter spp in the world; however there are a few reports in our country. 145 A. baumannii isolates from distinct wards and Children's Medical Center (CMC) in Tehran were studied in order to find the profile of antibiotic resistance among them. 40.6% (59/145) of A. baumannii isolates were identified as MDR. Overall susceptibility rates to cotrimoxazole, chloramphenicole and ciprofloxacin were 23.4%, 16.9% and 20.1%, respectively. Frequency susceptibility rates to amikacin, kanamycin, gentamycin and tobramycin decreased gradually from 81.2%, 50%, 50% and 62.5% in 2002 to 25%, 15.6%, 28.1% and 25% in 2007 respectively. Overall susceptibility rates to cephalosporines cephalotin, ceftazidime, cefteriaxon, ceftizoxime and cefixime were 9.3%, 14.7%, 16.2%, 15.9% and 18%, respectively. Susceptibility to carbapenems was assessed only in 2007. The susceptibility rates of Imipenem and meropenem were shown to be 50% and 46.8%, respectively. Our data indicates that MDR A. baumannii strains are spreading and carbapenem resistance is becoming more common in Iran. Our findings also highlight the importance of clinicians' access to updated susceptibility data regarding A. baumannii in developing countries such as Iran.

Effect of chlorhexidine on coronal microleakage from root canals obturated with Resilon/Epiphany Self-Etch.

This ex vivo study compared saliva coronal microleakage in root canals filled with Resilon/Epiphany Self-Etch (SE) system after final irrigation with different solutions. A total of 60 extracted single-rooted human teeth were instrumented using Mtwo Ni-Ti rotary instruments and divided into two experimental groups (n = 20 each) and positive and negative control groups (n = 10 each). The canals were irrigated with 1.3% NaOCl during instrumentation. After removing the smear layer with 17% EDTA, the root canals in groups A and B were flushed with distilled water and 2% chlorhexidine (CHX), respectively, after which they were obturated with Resilon/Epiphany SE using lateral compaction technique. After sterilizing the whole system with gamma-rays, saliva leakage was tested using a split-chamber model. Specimens were monitored every 24 h for 60 days. The data collected were then analyzed using the chi-square test and Kaplan-Meier survival analysis. As compared with group A, the specimens in group B tended to be more resistant to saliva leakage; however, the difference was not significant (P > 0.05). In conclusion, our findings suggest that 2% CHX is a good conditioner for root canal dentin before use of Resilon/Epiphany SE.

The effect of two post-space preparation techniques on the seal of resilon and gutta-percha obturation materials.

INTRODUCTION: The aim of this study was to compare the effect of post space preparation with Gates Glidden drills or hand files on the sealing ability of gutta-percha or Resilon obturation materials. MATERIALS AND METHODS: One-hundred and four single-rooted human teeth were instrumented and divided into four experimental groups (n=21 each) and two groups of positive and negative control (n=10). Forty-two roots of experimental groups were obturated with gutta-percha and Dorifill sealer; and 42 roots with Resilon/Epiphany self-etch using lateral compaction technique. Each gutta-percha or Resilon group was divided into two subgroups (n=21) and post-space prepared with either Gates Glidden drills or hand files and chloroform. After post space preparation, 5 mm of apical gutta-percha or Resilon was left intact. The whole system was sterilized with gamma-rays. Saliva leakage was tested using a split-chamber model. Specimens were monitored every 24 hours for 30 days. The data were analyzed using log-rank test and Cox regression analysis. RESULTS: There were no significant differences between the sealing ability of gutta-percha and Resilon. Furthermore, no significant difference was found between two different methods of post space preparation (P>0.05). CONCLUSION: Under the limitations of this ex vivo study, there were no significant differences between the sealing ability of Resilon and gutta-percha after post space preparation using Gates Glidden drills or hand files with the aid of chloroform.

Coronal microleakage in root canals obturated with lateral compaction, warm vertical compaction and guttaflow system.

INTRODUCTION: Root canal obturation seals the root canal system to prevent re-entry and/or growth of microorganisms. The provision of an appropriate restoration to coronally seal the access cavity affects the success of endodontic treatment. The purpose of this study was to evaluate the coronal microbial leakage in root canals that were either filled by lateral compaction, GuttaFlow or warm vertical compaction. MATERIALS AND METHODS: In this ex vivo study, 80 single-rooted human extracted teeth were randomly divided into three experimental groups (n=20) and two positive and negative control groups (n=10). The teeth in experimental groups were obturated with cold lateral compaction, GuttaFlow system or warm vertical compaction techniques. After sterilization of the whole system with gamma-ray, saliva leakage was tested using a split-chamber model. Specimens were monitored every 24 hours for 30 days. The data were analyzed using log-rank and Kaplan-Meier survival analysis tests. RESULTS: There were no significant differences in impeding saliva leakage between the three experimental groups (P>0.05). CONCLUSION: Under the conditions of this ex vivo study, it can be concluded that the sealing ability of cold lateral compaction, warm vertical compaction and GuttaFlow system was comparable.

Distribution of bla(TEM), bla(SHV), bla(CTX-M) genes among clinical isolates of Klebsiella pneumoniae at Labbafinejad Hospital, Tehran, Iran.

Extended-spectrum beta-lactamase (ESBL)-producing isolates of Klebsiella pneumoniae have been increasingly recognized in the hospital settings in Iran as well as throughout the world. The aim of this study was to detect and determine the genes encoding the ESBLs including bla(TEM), bla(SHV), and bla(CTX-M) groups among the K. pneumoniae isolates at Labbafinejad Hospital by polymerase chain reaction (PCR) and characterize them by direct sequencing of PCR products. Eighty-nine isolates were isolated from patients at different wards during March 2008-March 2009. They were identified as K. pneumoniae using biochemical tests. Susceptibility of isolates to 17 different antimicrobial agents was determined using agar disk diffusion method. The phenotypic confirmatory test was used to screen the isolates for production of ESBLs. To amplify the bla(SHV) the template DNA was extracted by boiling method. Plasmid DNA was extracted using minipreparation kit and used as template in PCR for detection of bla(TEM) and bla(CTX-M). The selected PCR products were sequenced and analyzed. All 89 strains were susceptible to imipenem. The rates of resistance to different antibiotics were in the following order: aztronam (79.7%), cefexime (67.4%), cefpodoxime (66.2%), cefotaxime (65.1%), ceftazidime (61.7%). The phenotypic confirmatory test detected 62 isolates (69.7%) as ESBL-producing K. pneumoniae. The prevalence of genes encoding ESBLs were as follows: bla(TEM) 54% (n = 48), bla(SHV) 67.4% (n = 60), bla(CTX-M-I) 46.51% (n = 40), and bla(CTX-M-III) 29% (n = 25). The bla(CTX-M-II) and bla(CTX-M-IV) were not detected. All bla(TEM) types were characterized as bla(TEM-1) and all bla(CTX-M-I) were identified as bla(CTX-M-15). The SHV types were characterized as SHV-5, SHV-11, and SHV-12. The rate of ESBL at Labbafinejad Hospital was 25% increase in a 4-year study that ended in March 2009. It appears that bla(TEM-1), bla(SHV-5), bla(SHV-11), bla(SHV-12), and bla(CTX-M-15) are the dominant ESBLs among the resistant strains of K. pneumoniae in Iran.

Molecular characterization of methicillin-resistant Staphylococcus aureus clones from a teaching hospital in Tehran.

A total of 52 methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates were collected from patients attending the teaching hospital of Tehran University of Medical Sciences. Disks containing antibiotics were used to determine the susceptibility of MRSA isolates. Analysis of SmaI macrorestriction profiles of the 52 MRSA isolates were grouped into three PFGE types. The majority of isolates (n=49) were clustered into only one major PFGE type, designated as pulsotype A; these belonged to SCCmec type III or IIIA and showed resistance to ampicillin, ciprofloxacin, cotrimoxazole, erythromycin, gentamicin, and tetracycline. The remaining isolates fell into pulsotypes B and C, both belonging to SCCmec-type IV. All MRSA isolates were susceptible to vancomycin, teicoplanin, quinupristin-dalfopristin, linezolid, and tigecycline. The present study shows that a MRSA clone similar to the Brazilian clone (ST 239) of MRSA, which is a multiresistant MRSA clone with a high level of methicillin resistance, is very common in this teaching hospital in Tehran.

Phenotypic and genotypic evaluation of aminoglycoside resistance in clinical isolates of staphylococci in Tehran, Iran.

Aminoglycosides play an important role in the treatment of staphylococcal infections, despite the emerging widespread resistance among Staphylococcus. To determine the prevalence of aminoglycoside resistance and aminoglycoside modifying enzyme (AME) genes among infected patients at a teaching hospital in Tehran, Iran, we tested 585 Staphylococcus isolates, of which 322 were Staphylococcus aureus and 263 were coagulase-negative staphylococci, as determined by the disk diffusion method and multiplex PCR. The minimum inhibitory concentration of gentamicin for each isolate was determined by microbroth dilution. All methicillin-resistant staphylococci were mecA-positive by PCR. Of the 585 isolates, 27.6% were susceptible to gentamicin and kanamicin, 27.1% to tobramicin and amikacin, and 21.3% to netilmicin. The most prevalent AME genes included aac(6')-Ie-aph(2'') (93.7%) followed by aph(3')-IIIa (84.3%) and ant (4')-Ia (28.1%). More than 90% of aminoglycoside-resistant staphylococci contained at least one AME gene. The coexistence of two or three AME genes was detected in most gentamicin-resistant isolates. These results suggest an alarming rate of aminoglycoside resistance in this test location in Tehran, Iran. Continued surveillance at the genotypic and phenotypic levels, and adherence to well-designed antibiotic and infection-control policies are necessary to limit the spread of antimicrobial resistance.