Background:Extended spectrum β-lactamases (ESBLs) and AmpC β-lactamases enzyme are major sources of resistance to β-lactam antibiotics especially in Enterobacteriaceae such as Escherichia coli and Klebsiella pneumoniae. Increasing frequency of the co-existence of ESBLs with AmpC-β-lactamases in bacteria is a serious threat for treating bacterial infections.Objectives:The aim of this study was to determine the presence of AmpC and CTX-M types of β-lactamases in clinical isolates of E. coli and K. pneumoniae producing ESBLs.Materials and Methods:Resistance to different antibiotics was determined using the standard disk diffusion method. ESBLs, MBLs and AmpC-β-lactamases were detected by the combination double disk test (CDDT) method and polymerase chain reaction (PCR) was used to determine blaCTX-M genes in the ESBLs and AmpC positive isolates.Results:The prevalence of ESBLs and AmpC-β-lactamase producer isolates was 181 (43.8%) and 133 (37.2%), respectively. The prevalence of blaCTX-M among isolates was 61 (14.7%).Conclusions:Outbreak of isolates co-expressing AmpC-β-lactamases and ESBLs can cause serious problems in the future, regarding the treatment of infections caused by these common enteric pathogens.

Our results revealed that MRSA strains that were isolated from the air, the environment of the ICU and the patients who were colonized or infected with MRSA often exhibited the same spa and SCCmec types. These results also reveal that the isolates from the patients and environment were usually indistinguishable.

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.

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.

The probiotic potential of Lactobacillus species isolated from infant feces was investigated. For this study, the antibiotic susceptibility, tolerance in gut-related conditions, antimicrobial activity, and ability to adhere to a human colorectal adenocarcinoma cell line (Caco-2 cells) of four commonwere assessed. Most isolates that which were sensitive to imipenem, ampicillin, gentamycin, erythromycin and tetracycline were selected for other tests. L. gasseri isolates had the greatest sensitivity to gastric and intestinal fluids (<10% viability). L. fermentum (FH5, FH13 and FH18) had the highest adhesion to Caco-2 cells. The lowest antibacterial activity against pathogenic bacteria was shown by L. gasseri strains in spot tests. Furthermore, non-adjusted cell-free culture supernatants with low pH had greater antimicrobial activity, which was related to organic acid. The results showed that some isolates of L. rhamnosus and L. fermentum are suitable for use as a probiotic.