No abstract

Linezolid, an oxazolidinone antimicrobial agent that acts by inhibiting protein synthesis in a unique fashion, is used in the treatment of community-acquired pneumonia, skin and soft-tissue infections and other infections caused by Gram-positive bacteria including VRE and methicillin-resistant staphylococci. Currently, linezolid resistance among these pathogens remains low, commonly <1.0%, although the prevalence of antibiotic resistance is increasing in many countries. Therefore, the development of resistance by clinical isolates should prompt increased attention of clinical laboratories to routinely perform linezolid susceptibility testing for this important agent and should be taken into account when considering its therapeutic use. Considering the importance of linezolid in the treatment of infections caused by Gram-positive bacteria, this review was undertaken to optimize the clinical use of this antibiotic.

This is the first known description of ESBL-producing and AmpC β-lactamase-producing Shigella and of PMQR Shigella in Iran. The emergence of CTX-15, CMY-2 and qnrS1 genes may compromise the treatment of shigellosis. Strategies to minimize the spread of ESBL-producing and AmpC-β-lactamase-producing Shigella should be implemented.

Background: Extended-spectrum beta (β)-lactamase (ESBL)-producing enterobacteria are major emerging pathogens in nosocomial infections. Methodology: The combination disk synergy test was used to evaluate 202 consecutive non-repeated Klebsiella pneumoniae (K. pneumonia) strains for ESBL production. The strains were isolated from various clinical specimens of hospitalized patients over the period from July 2005 to March 2007. Their antibiotic susceptibility pattern was also determined by the disk diffusion method. Demographic and medical data of the patients were recorded using a questionnaire. Results: One hundred and fifty-seven (77.7%) of the isolates were confirmed as ESBL-producers. By univariate analysis, young age, stay in intensive care unit (ICU)/medical wards, recent stay in ICU, and number of days of ICU stay were found to be risk factors for acquisition of resistant bacteria (χ2 and Mann-Whitney U tests, P < 0.05). However, binary logistic multivariate regression analysis confirmed that stay in ICU [Odds ratio (OR) 6.09, 95% confidence interval (CI) 2.36-15.72; P < 0.001] or medical wards [OR 3.72, 95% CI 1.42-9.75; P = 0.007] were significantly associated with ESBL production. Imipenem, ofloxacin, cefoxitin and norfloxacin (against urinary isolates) were found to be highly active against ESBL-producing isolates in vitro (100%, 75.2%, 69.4% and 66.7% susceptibility, respectively). In addition to most β-lactams, they showed co-resistance with other antibiotics such as ciprofloxacin, aminoglycosides, trimethoprim/sulfamethoxazole and tetracycline. Conclusion: Our results showed a high prevalence of ESBL-producing K. pneumoniae in our hospital setting. As the available treatment options are limited, antibiotic control policies together with the implementation of infection control measures remain of high importance.

This study indicated that the 13-valent pneumococcal conjugate vaccine (PCV13) could cover the majority of the invasive pneumococcal isolates. Drug-resistant and multidrug-resistant Streptococcus pneumoniae strains are circulating in Iran. Therefore, public immunization of infants using PCV13 is recommended to reduce the incidence of pneumococcal disease and pneumococcal-resistant strains in Teheran.

BackgroundTo investigate antibiotic resistance, the occurrence and distribution of class 1 and 2 integrons in multidrug- resistant Staphylococcus aureus isolates from hospitals in Tehran, Iran.The isolates were examined for susceptibility to antimicrobial agents. The mecA gene, class 1 and 2 integrons were detected by PCR. Integrase positive strains were further analysed for the presence of resistance gene cassettes using specific primers and were sequenced.ResultsAmong 139 S.aureus isolates, 109 (78.4 %) and 112 (80.5 %) strains were considered as multidrug resistant and mecA positive, respectively. Class 1 integrons and internal variable regions were found in 72.6 % (101/139) and 97 % (98/101) and class 2 integrons and variable regions also in 35.2 % (49/139) and 65.3 % (32/49) of S.aureus clinical isolates, respectively. Twelve distinct cassette arrays were found, containing genes encoding resistance to β-lactams, aminoglycosides, streptothricin, trimethoprim, chloramphenicol,a putative glucose dehydrogenase precursor and a protein with unknown function. Gene cassette arrays aadB, aadA2 and dhfrA1-sat2-aadA1 were common in S.aureus isolates. We detected a completely new gene cassettes which contained aadB, oxa2, aacA4, orfD-aacA4-catB8, aadB-catB3, orfD-aacA4 and aadB-aadA1-cmlA6 of class 1 and dhfrA1-sat2-aadA1, dhfrA11, dhfrA1-sat2 of class 2 integrons.ConclusionsThis is the first study to report carriage of class 1 and 2 integrons and associated gene cassettes among in S.aureus isolates from Iran.

Acinetobacter baumannii is a ubiquitous pathogen that has emerged as a major cause of healthcare-associated infections. Acinetobacter baumannii usually causes respiratory tract, urinary tract, blood stream and surgical site infections. They are of increasing importance because of its ability to rapidly develop resistance to the major groups of antibiotics. There are few data available on the antimicrobial susceptibility of A. baumannii in Iran. During the period of study from July 2005 to November 2006, a total of 88 strains of A. baumannii were isolated from clinical specimens obtained from patients hospitalized in an Iranian 1000-bed tertiary care hospital. Conventional bacteriological methods were used for identification of A. baumannii. Susceptibility testing was performed by the method recommended by Clinical Laboratory and Standards Institute (CLSI). The majority of isolates were from respiratory tract specimens. The organism showed high rate of resistance to ceftriaxone (90.9%), piperacillin (90.9%), ceftazidime (84.1%), amikacin (85.2%) and ciprofloxacin (90.9%). Imipenem was the most effective antibiotic against A. baumannii and the rate of resistance for imipenem was 4.5%. The second most effective antibiotic was tobramycin, and 44.3% of A. baumannii isolates were resistant to this antibiotic. In conclusion, our study showed that the rate of resistance in A. baumannii to imipenem was low. There was a significant relationship between demographic features of patients such as age, undergoing mechanical ventilation, length of hospital stay and drug resistance.

Class 2 integrons were found to be predominant among our Shigella spp. This reflects the need to monitor the acquisition and dissemination of different resistant gene cassettes among integrons. Comparison of PFGE pattern through standard procedures promoted the molecular epidemiological surveys and identification of clonal isolates in Iran and other Asian countries.