Determination of vancomycin minimum inhibitory concentration for ceftazidime resistant Streptococcus pneumoniae in Iran.

BACKGROUND: In the context of growing health concerns over antibiotic resistance, the evaluation of the minimum inhibitory concentration (MIC) of vancomycin for Streptococcus pneumoniae (S. pneumoniae) strains resistant to ceftazidime becomes important for guiding health policy makers. The aim of this study was to determine vancomycin MIC of ceftazidime resistant S. pneumoniae strains. METHODS: Fifty identified serotypes of ceftazidime resistant S. pneumoniae strains were included in the study. The vancomycin MIC of the above mentioned bacteria was determined based on the 0.5 McFarland standards, by using a microdilution broth and the Etest method. RESULTS: The results showed that out of 50 ceftazidime resistant strains of S. pneumoniae, 46 strains (92%) have shown a vancomycin MIC ≤0.19 - 0.1.5 µg/ml and only four strains (8%) have shown a vancomycin MIC equal to 1.5 µg/ml and the related maximum zone of inhibition was of 10 millimeter diameters. CONCLUSIONS: The results of this investigation point out the emergence of S. pneumoniae strains with a vancomycin MIC ≥1.5 µg/ml, which were resistant to ceftazidime. This finding uncovers a major health concern: a vancomycin MIC higher than 1.5 µg/ml and maximum zone of inhibition of only 10 millimeter. These findings represent an important warning for health authorities globally, concerning the treatment of patients, as the occurrence of S. pneumoniae strains with decreased vancomycin susceptibility has been demonstrated.

The Study of Genetic Relationship Among Third Generation Cephalosporin-resistant Salmonella enterica Strains by ERIC-PCR.

BACKGROUND AND OBJECTIVES: Salmonella is an important food-borne pathogen responsible for disease in humans and animals. The aim of this study was to investigate the genetic relationship among third generation cephalosporin-resistant Salmonella enterica strains by Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR. METHODS: The study included all Salmonella isolates obtained from clinical cases in a pediatric hospital in Tehran, Iran during 2006 to 2009. Antimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute. The genetic relationship between third generation cephalosporins-resistant Salmonella enterica strains was determined using ERIC-PCR. RESULTS: Of 136 Salmonella enterica isolates recovered from pediatric patients, six isolates including four Salmonella enterica serotype Infantis and two Salmonella enterica serotype Enteritidis showed an extended-spectrum cephalosporins resistant phenotype. ERIC-PCR differentiated Salmonella enterica serotypes Infantis and Enteritidis into 2 distinct clusters arbitrarily named as E1 and E2. Profile E1 was found in two Salmonella enterica serotype Enteritidis isolates, and profile E2 was found in four Salmonella enterica serotype Infantis isolates. CONCLUSION: Extended-spectrum cephalosporins resistant Salmonella could be attributed to a few predominant serotypes including Enteritidis and Infantis in this study. Genetic analysis using ERIC-PCR showed that closely related clones are responsible for the occurrence of extended-spectrum cephalosporins resistant Salmonella infection in Tehran.

The occurrence of extended-spectrum ß-lactamase producing Shigella spp. in Tehran, Iran.

BACKGROUND AND OBJECTIVES: The emergence of extended-spectrum ß-lactamase (ESBL)-producing Shigella spp. is of increasing clinical concern specially in children worldwide. The aim of this study was to investigate the occurrence of extended-spectrum ß-lactamase producing Shigella spp. in Tehran, Iran. MATERIALS AND METHODS: The study included all Shigella isolates recovered from pediatric patients aged less than 12 years admitted to a major pediatric hospital in Tehran, Iran, from 2008 to 2010. Bacterial identification, antimicrobial susceptibility testing, extended spectrum ß-lactamases (ESBLs) screening and confirmatory tests were performed according to the standard guidelines. Conjugal transfer experiments and plasmid analysis were also carried out. Polymerase chain reaction and sequencing were used to identify the genetic determinants responsible for ESBL production. RESULTS: Four out of 55 Shigella isolates, including three S. sonnei and one S. flexneri, showed an ESBL-positive phenotype. Plasmid transfer of the ESBL phenotype was successful for the S. flexneri isolate only. By PCR and sequencing, one S. sonnei isolate tested positive for the CMY-59 gene, while the other two S. sonnei and the S. flexneri isolates tested positive for the bla TEM-1 and bla CTX-M-15 genes. CONCLUSION: We found the prevalence of ESBL producing Shigella isolates was higher than detection rates observed in many other countries. Our finding raise concerns about the dissemination of ESBL among the strains of endemic S. sonnei throughout the country, because this species is now the most frequently isolated Shigella species in Iran and shigellosis by such strains in the community can pose a significant threat to patients and presents a challenge for disease management.

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.

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.

Quantitative and qualitative determination of dimethyl phthalate and N, N-diethyl-m-toluamide in repellents commercial formulations by high performance thin layer chromatography.

In this study HPTLC was used for simultaneous quantitative and qualitative determination of N, N-diethyl meta toluamide (DEET) and dimethyl phthalate (DMP), which are the main elements and active ingredients in current chemical repellents. Some defined amounts of commercial form of 3 repellents included trench pomade, stick insect repellent (SIR), which is containing 33% of DEET and DMP60 (dimethyl phthalate 60%) dissolved in ethyl acetate solvent, separately. The method employed TLC aluminum plate precoated with silica gel plates (SiO4) 60F245 as the stationary phase. The solvent system consisted of benzene-diethyl etherhexane (5:3:2, v/v/v) as mobile phase. The multiple level method used for spotting. Densitometric analysis of repellents was carried out using TLC scanner 3 and CATS4 software in the absorption/reflection mode at 230 nm. According to the results, the type and amount of active ingredients in DMP60 lotion was 61.8 g (SE = +/-1.6) per 100 cc and in SIR, 31.3 g (SE = +/-0.8) diethyl meta toluamide per 100 g of repellents raw materials. Also the active ingredients in trench pomade were determined as a combination of DMP and DEET by rates of 5.5 g (SE = +/-0.2) and 25 g (SE = +/-l) per 100 g repellents commercial formulations, respectively. In this study, the value of Rf for DMP and DEET was calculated 0.71 +/- 0.2 and 0.32 +/- 0.2, respectively. HPTLC is a suitable method to quantitatively and quantitatively determine repellents which have DMP and DEET active ingredients. Since most of commercial chemical repellents have this active ingredient, adjusting and setting HPTLC up can be important.

Laboratory determination of protection time in four chemical repellents against Anopheles stephensi.

In the present study we determined the Protection Time (PT) and Failure Time (FT) of the DMP lotion, which is synthesized and formulated in Iran and it was compared with other products such as MIP60 and Dimp31.7 lotions (commercial and current formulations of dimethyl phthalate) and trench pomade (a popular local repellent in Iran) against Anopheles stephensi Liston (main malaria vector in south of Iran) in laboratory condition. In this research which is an interventional and experimental study, the screen cage method was used to estimate PT and FT of repellents against An. stephensi. The following commercial formulations of chemical repellents were tested: Iranian DMP lotion (DMP60) (contains 60% dimethyl phthalate, 25% isopropyl alcohol, 5% twine 80 and 10% water), MIP60 and Dimp31.7 lotions contains 60 and 31.7% active ingredient of dimethyl phthalate and trench pomade (a combination of N,N-diethyl-m-toluamide (DEET) and DMP). Test was done on human volunteers. In this test some defined amount of repellents applied on human volunteer's forearm and then was inserted in cage against mosquitoes biting to determine PT and FT. According to the results of this research, the PT of Iranian DMP60 lotion against An. stephensi was determined about 274 min (SE = ++/-.04), which didn't have any significant difference with MIP60 and trench pomade, but it was significantly more than Dimp31.7. Furthermore the FT of DMP60 against An. stephensi was determined about 327 min (SE = +/-10.47), that in this case it had a significant deference with MIP60 lotion and trench pomade. The failure time of DMP60 was less than another two repellents. The Iranian DMP60 lotion can potentially compete with MIP60 and Dimp31.7, but to increase the FT rate, its formulation need to be improved.