Nosocomial bloodstream infections in a Turkish university hospital: study of Gram-negative bacilli and their sensitivity patterns

Anti-capsular activity of CuO nanoparticles against Acinetobacter baumannii produce efflux pump

Copper oxide nanoparticles are modern kinds of antimicrobials, which may get a lot of interest in the clinical application. This study aimed to detect the anti-capsular activity of CuO nanoparticles against Acinetobacter baumannii produce efflux pump. Thirty-four different clinical A. baumannii isolates were collected and identified by the phenotypic and genetic methods by the recA gene as housekeeping. Antibiotic sensitivity and biofilm-forming ability, capsular formation were carried out. The effect of CuO nanoparticles on capsular isolates was detected, the synergistic effects of a combination CuO nanoparticles and gentamicin against A. baumannii were determined by micro broth checkerboard method, and the effect of CuO nanoparticles on the expression of ptk, espA and mexX genes was analyzed. Results demonstrated that CuO nanoparticles with gentamicin revealed a synergistic effect. Gene expression results show reducing the expression of these capsular genes by CuO nanoparticles is major conduct over reducing A. baumannii capsular action. Furthermore, results proved that there was a relationship between the capsule-forming ability and the absence of biofilm-forming ability. As bacterial isolates which were negative biofilm formation were positive in capsule formation and vice versa. In conclusion, CuO nanoparticles have the potential to be used as an anti-capsular agent against A. baumannii, and their combination with gentamicin can enhance their antimicrobial effect. The study also suggests that the absence of biofilm formation may be associated with the presence of capsule formation in A. baumannii. These findings provide a basis for further research on the use of CuO nanoparticles as a novel antimicrobial agent against A. baumannii and other bacterial pathogens, also to investigate the potential of CuO nanoparticles to inhibit the production of efflux pumps in A. baumannii, which are a major mechanism of antibiotic resistance.

Comparison of the effects of silver nanoparticles on pathogenic bacteria resistant to beta-lactam antibiotics (ESBLs) as a prokaryote model and Wistar rats as a eukaryote model

BACKGROUND

Antimicrobial resistance in hospital pathogens is an important concern. It can cause longer hospital stays, increase costs, and contribute to increased mortality and morbidity in hospitalized patients. The aim of this study was to categorize and identify gram-negative bacilli capable of ESBLs production and to study the effect of MIC silver nanoparticles on bacteria strains and then study them in Wistar rats.

MATERIAL AND METHODS

A total of 186 clinical samples in 3 hospital of Isfahan city was studied during 8 months. The ESBL assay was performed by disk diffusion method. Minimum inhibitory concentration (MIC) values were determined by agar dilution method. Additionally, ESBLs production was examined by using the standard ESBL disc and DDT (double disk approximation test) procedures. Student's T-test and ANOVA were used for statistical analysis of the data. The ESBL-producing bacteria were then subjected to minimum concentrations of silver nanoparticles and then examined in Wistar rats.

RESULTS

Of the 186 patients studied, 140 (75.3%) had gram-negative bacilli containing ESBL and 46 (24.7%) had gram-negative bacilli without ESBL and the most prevalent bacteria was identified as Klebsiella pneumonia, with especially strong resistance to cefotaxime. All of these bacteria were sensitive to the silver nanoparticle solution with density of 100 ppm, but the 4 nm size did not show any significant difference from control group Wistar rats at 6 months.

CONCLUSIONS

The results seem to indicate a direct correlation between silver nanoparticle solution concentration and the diameter of growth zone for ESBL-producing bacteria. Assays in our study were in vitro; if use of silver nanoparticle particles in vivo proves to be with adverse effects, it could be a valuable alternative to antibiotics.

Evaluation of bacteremias in a Turkish university hospital: 3-year outcomes

In this retrospective study, the investigators examined blood cultures from patients that had been diagnosed with bacteremias over a 3-y period. The study was conduced at Kocatepe University Hospital (Middle Anatolia, Turkey). Blood samples that arrived at the university's microbiology laboratory between 2002 and 2005 were evaluated retrospectively. These samples were classified as contamination, false positivity, community-acquired bacteremia (CAB), or hospital-acquired bacteremia (HAB). Patient age and sex, foci of bacteremia, present comorbidities, predisposing factors, pathogens, and mortality rates were evaluated. A total of 1783 blood cultures that had been drawn from 1441 patients during this 3-y period were examined retrospectively. Of 354 positive isolates, 61 (17.2%) were CABs and 293 (82.8%) were HABs. In HABs, the most commonly isolated microorganisms were Staphylococcus aureus (37.5%), coagulase-negative staphylococci (29.7%), and Escherichia coli (10.2%); in CABs, the most commonly isolated microorganisms were S aureus (29.5%), Brucella spp (26.2%), and E coli (24.6%). Crude mortality rates were determined to be 15.2% for HABs and 12.7% for CABs. This study yielded data on the most common foci of bacteremia, microbiologic factors, and the epidemiology associated with HABs and CABs. It is hoped that these data will enhance empirical antibiotic therapeutic approaches, thereby preventing delays in treatment and decreasing mortality rates associated with bacteremias.

Detection and prevalence of active drug efflux mechanism in various multidrug-resistant Klebsiella pneumoniae strains from Turkey

The prevalence of active drug efflux pump and porin alterations was investigated in Turkish nosocomial strains of Klebsiella pneumoniae exhibiting a multidrug-resistant phenotype. MICs of various antibiotics, including quinolones, chloramphenicol, tetracycline, and beta-lactams, for those strains were determined either with or without the efflux pump inhibitor phenylalanine arginine beta-naphthylamide (PAbetaN). Thirty-nine percent of the strains exhibited a PAbetaN-modulated resistance for quinolones, chloramphenicol, and tetracycline. In these strains, a significant increase of chloramphenicol accumulation was gained in the presence of the efflux pump inhibitor PAbetaN or with the energy uncoupler carbonyl cyanide m-chlorophenylhydrazone. Moreover, high-level expression of the membrane fusion protein AcrA, which was immunodetected in most of those isolates, suggests that the AcrAB/TolC efflux machinery contributed to their antibiotic resistance. Studies of K. pneumoniae porins indicated that the majority of the strains, including extended-spectrum beta-lactamase producers and efflux-positive ones, presented an alteration in their sorbitol-sensitive porin (OmpK35) expression. This is the first report showing the prominent role of active drug efflux in the antibiotic resistance of nosocomial K. pneumoniae strains from Turkey.

Hospital-acquired pneumonia: challenges and options for diagnosis and treatment

The management of hospital-acquired pneumonia (HAP) presents a major challenge for the clinician. The insensitivity of current diagnostic methods and the increasing prevalence of nosocomial pathogens with multiple antibiotic resistance complicate the issue. Use of mechanical ventilation and broad-spectrum antimicrobials in the intensive care setting predipose patients to acquire HAP more frequently with antimicrobial-resistant pathogens. Controversy exists regarding the patients in which invasive diagnostic testing is indicated; the timing of these procedures is another subject of debate. Proper empirical therapy is fundamental to a favourable outcome, and the selection of inappropriate agents to which pathogens are resistant contributes significantly to morbidity and mortality. In general, there is agreement on the requirement for a thorough knowledge of the local causative organisms and the pathogens' resistance profiles. A wide variety of antimicrobials can be used either as monotherapy or in combinations.

The organization of hospital infection control in Turkey

This article describes the current organization of infection control in Turkey in regard to regulations, functions and responsibilities of infection control committees and the national NosoLINE project. Also, incidence and prevalence of hospital infections and antimicrobial resistance in Turkey are reported.