Iranian Journal of Medical Microbiology

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Background and objectives: Pseudomonas aeruginosa is important opportunistic pathogen and to produce widespread infection by numerous virulence factors. Drug delivery system that reduces the drugs toxicity while increasing their therapeutic index is a great interest and liposomes can provide the benefits. Liposomes are colloidal vesicules ranging from a few nanometers to several micrometers in diameter. The present in vitro study was designated to evaluate the antimicrobial activity of free and liposomal amikacin against Pseudomonas aeruginosa(ATCC 27853).
Materials and methods: The minimal inhibitory concentrations (MICs) of free and liposomal amikacin for Pseudomonas aeruginosa (ATCC 27853) were determined by broth macro-dilution technique as recommended by CLSI (Clinical and laboratory standards institute). We therefore, encapsulated this drug in to liposome prepared by sonication. Change of number of bacteria in equal minimal inhibitory concentration of liposomal amikacin was compared with the change of number of bacteria in the present of various concentrations of free amikacin.
Results:The results showed that of liposomal amikacinhad antimicrobial effect and MIC of liposomal amikacin were equal of 4µg/ml however minimal inhibitory concentration of free amikacin was 2µg/ml. Comparison of change of number of bacteria had shown that the effect of liposomal amikacin (4 µg/ml) after 8 h is equal of 6 µg/ml free amikacin after 4h.
Conclusion: According to the results we can probably to use of liposomal amikacin for Pseudomonas infections, but we need more study and research

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Background and aims: Escherichia coli harboring extended spectrum β-lactamase (ESBLs) are significantly resistant to other antibiotics and caused several health problems. The present study was carried out to characterize the ESBL types and to determine their pattern of resistance to four antimicrobial agents in clinical isolates of E. coli.

Material and methods: During April 2012 to May 2013, 500 clinical isolates of E. coli were collected from two hospitals in Boroujerd. Phenotypic screening and confirmation tests for ESBL detection and antibiotic susceptibility testing were performed according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Minimum inhibitory concentration of imipenem, meropenem, amikacin and ceftriaxone was determined by the E-test method. All ESBLs producing isolates were examined for presence of the TEM, SHV and CTX-M genes by PCR method.

Results: All of the studied isolates were susceptible to imipenem and meropenem. Additionally, among ESBLs producer isolates good susceptibility to amikacin and ceftriaxone (P-value ˂ 0.5) was observed. The prevalence of the TEM, SHV and CTX-M genes among 190 ESBLs producing isolates was as follows: TEM positive: 61 (32.1%), SHV positive: 60 (31.6%) and CTX-M: 62 (32.6%). TEM, SHV and CTX-M genes occurred together in 25 (13.1%) of the isolates.

Conclusion: The high prevalence of E.coli producing ESBL in Boroujed hospitals reported. More than one ESBL was produced by many isolates, and this was correlated with increased resistance levels. Carbapenems continue to show good in vitro activity agent ESBLs producing organism. 

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Background and Aim: Urinary tract infection (UTI) is one of the most common infections, and Escherichia coli is so far the most common causative agent of this disease. The O antigen, consisting of many repeats of an oligosaccharide unit, is part of the lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria. The variability of the O antigen provides the major basis for serological schemes of Gram-negative bacteria. The aim of this study was to investigate the prevalence of O-serogroups among E. coli isolated from patients with UTI.

Materials and Methods: During three months, 210 patients with urinary tract infection, referred to three hospitals of Tehran, Sanandaj and Boroujerd. E. coli isolates were identified using standard methods then serogrouping was performed by using PCR method.

Results: A total of 150 E. coli strains were isolated from the urine samples. The most common types of O antigens were O1 (13.33%), O16 (8%), O8 (5.33%) and O21 (4%). There was no positive isolate for O22 and O83 genes.

Conclusions: The present study revealed that serogroup O1 was isolated with maximum frequency followed by O16, O8 and O21, respectively. In UPEC, the O-serogroups can be related to the virulence factor profile of each strain. Further studies from other parts of Iran and on other serogroup are recommended.