Investigation of the Relationship between the Presence of Chromosomal and Plasmid-Encoded AmpC Genes and Type of Clinical Specimen in Pseudomonas Aeruginosa

BACKGROUND AND OBJECTIVE: Different clinical specimens play a decisive role in the type and nature of drug resistance in pathogenic organisms. Occasionally, the presence of certain antibiotic resistance genes is associated with the type of clinical specimen. The aim of this study was to determine the relationship between the presence of chromosomal and plasmid-encoded AmpC genes and type of clinical specimen in Pseudomonas aeruginosa. METHODS: In this descriptive and experimental study, 114 isolates of Pseudomonas aeruginosa, and clinical specimens including blood, urine, wound secretion, burn injuries were collected from teaching hospitals in Hamadan. The presence of chromosomal and plasmid-encoded AmpC genes was evaluated using multiplex PCR technique. FINDINGS: The plasmid-encoded AmpC genes were observed more than chromosomal genes in Pseudomonas aeruginosa isolates. The FOX gene with a value of 29 (37.66%) (p≤0.037) and DHA gene with a value of 5(6.4%) (p≤0.015) in plasmid-encoded AmpC genes, while FOX gene with a value of 39 (48.75%) (p≤0.001) and MOX gene with a value of 2 (7.36%) in chromosomal AmpC genes had the highest and lowest frequency, respectively. CONCLUSION: The results of the study showed that the presence of chromosomal and plasmid-encoded AmpC genes may have various frequencies according to the type of clinical specimen

Identification and Determination of the Relationship between ccr Alleles and Antibiotic Resistance in Clinical Isolates of Methicillin Resistant Staphylococcus aureus

BACKGROUND AND OBJECTIVE: Resistance to methicillin and the presence of the ccr gene in Staphylococcus aureus have provided the basis for the emergence of methicillin resistant strains. The aim of this study was to identify the ccr cassette alleles in methicillin-resistant S.aureus strains and to determine the relationship between the presence of these casts with a multivariate process. METHODS: In this study, 135 clinical isolates of methicillin-resistant S.aureus was isolated by genotypic methods. ccr gene cassette was evaluated qualitatively by multiplex PCR method. Data was analyzed using SPSS version 16 and also, the chi - square test was used. FINDINGS: Out of 135 strains of S.aureus resistant to methicillin, penicillin and erythromycin antibiotic resistance were the most frequent, more than 90%, respectively. Also, ccr gene cassette in the study on genes ccrA/B1, ccrA/B2, ccrA/B3, ccrA/B4, ccrA2/B, ccrC had taken place, respectively, in 2 isolates (1.3%) for gene ccrA/B1, 12 isolates (8.2%) ccrA/B2, 15 isolates (10.34 %) ccrA/B3, 2 isolates (1.3%) ccrA/B4, 4 isolates (8.2 percent) ccrA2/B and 22 isolates (15.87 %) were positive for the gene ccrC. A significant correlation between the presence of these genes and antibiotic distribution was observed (p=0.05). CONCLUSION: The ccr gene cassette can provide a background of resistance to various antibiotics in methicillin-resistant S.aureus strains

Frequency of Shiga –toxin producing E.coli (STEC) in patients with hemorrhagic colitis referring to Tehran hospitals

Background&Objective: Shiga-toxin producing E. coli (STEC) belonging to several different O serotypes are one of the etiological agent of diarrhea. The STEC strains are considered as an etiological agent for enteritis after non-typhoidal salmonellosis and Campylobacter. They have also been associated closely with the hemolytic uremic syndrome (HUS) and hemorrhagic colitis(HC). The aim of this study was to determine of the frequency of STEC in patients with hemorrhagic colitis referring to Tehran hospitals. Materials&Methods: From March to September 2004, 70 patients with hemorrhagic colitis (Case)an 70 patients with diarrhea (Control) were included in this study. The stx gene was detected by PCR and was used for the determination of STEC strains. Slide agglutination with specific antisera used to detect O serogroup. Polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) analysis of the flagellin gene (fliC) was performed for determining their flagellar antigen (H). Results: Two samples (2.9%) from Hemorrhagic colitis cases and 12 samples (17.1 %) from diarrheal cases were positive for STEC. There was no significant correlation between STEC and Hemorrhagic colitis but there was a significant correlation between STEC and diarrhea (p<0.05). STEC isolates O142:H48 serotype was from hemorrhagic colitis cases and O126:H47, O126:H6, O26:H4 and O111:H23 serotypes were from diarrheal cases. These serotypes were not reported in hemorrhagic colitis cases. Conclusion: Our data showed that there was no significant correlation between STEC and hemorrhagic colitis. This could be explained since serotype responsible for hemorrhagic colitis i.e. O157:H7 serotype is not present in Iran

Mortality attributable to carbapenem-resistant Pseudomonas aeruginosa

Whether carbapenem resistance is associated with mortality in patients with Pseudomonas aeruginosa bacteremia is controversial. To address this issue, we conducted a systematic review and meta-analysis based on cohort studies. We searched PubMed and Embase databases to identify articles (up to April 2015). The DerSimonian and Laird random-effect model was used to generate a summary estimate of effect. Associations were evaluated in subgroups based on different patient characteristics and study quality criteria. Seven studies with a total of 1613 patients were finally included, of which 1 study had a prospective design, and the other 6 were retrospective. Our meta-analysis showed patients with carbapenem-resistant P. aeruginosa bacteremia were at a higher risk of death compared with those with carbapenem-susceptible P. aeruginosa bloodstream infections (pooled odds ratio (OR) from three studies reporting adjusted ORs: 3.07, 95% confidence interval (CI), 1.60–5.89; pooled OR from 4 studies only reporting crude ORs: 1.46, 95% CI, 1.10–1.94). The results were robust across a number of stratified analyses and a sensitivity analysis. We also calculated that 8%–18.4% of deaths were attributable to carbapenem resistance in four studies assessing the outcome with 30-day mortality, and these were 3% and 14.6%, respectively, in two studies using 7-day mortality or mortality during bacteremia as an outcome of interest. Carbapenem resistance had a deleterious impact on the mortality of P. aeruginosa bacteremia; however, the results should be interpreted cautiously because only three studies reporting adjusted ORs were included. More large-scale, well-designed prospective cohorts, as well as mechanistic studies, are urgently needed in the future