A frequency and molecular typing study of methicillin-resistant staphylococcus aureus isolates in teaching hospitals in Shahrekord, southwestern Iran

Methicillin-resistant Staphylococcus aureus (MRSA) remains a significant public health problem and treatment challenge. Objectives: This study was conducted to determine the frequency, molecular types, and drug resistance of S. aureus isolated from nasal carriers in two teaching hospitals (Hajar and Kashani) in Shahrekord, southwestern Iran. Methods: In this cross-sectional study, 262 nasal specimens were obtained from healthcare staff. The disk-diffusion method was used to detect MRSA. Nine antibiotic disks were used to determine the antibiotic susceptibility pattern. Staphylococcal cassette chromosome mec (SCCmec) types were identified by the multiplex polymerase chain reaction (PCR). The data analysis was performed using Fisher’s exact test with SPSS software. Results: Forty-eight (18.8%) specimens were identified as S. aureus, of which 30 (11.45%) specimens were methicillin resistant. The nasal colonization rate of the MRSA isolates was not associated with age or gender (P > 0.05). The highest resistance (33%) recorded was to rifampin, and all the isolates were susceptible to quinupristin-dalfopristin, vancomycin, and linezolid. The SCCmec results showed that 16.7%, 6.7%, 20%, and 56.6% of MRSA isolates were types I, II, III, and IV, respectively. Conclusions: Nasal isolates of MRSA were prevalent among hospital staff. The highest level of resistance was to rifampin, and all the isolates were susceptible to quinupristin-dalfopristin, vancomycin, and linezolid. SCCmec type 4 was the most frequent MRSA isolate. © 2016, Ahvaz Jundishapur University of Medical Sciences

Microbiological qualification of air, water and dialysate in a haemodialysis centre; a new focus on Legionella spp.

Background and Objectives: The microbiological monitoring of the water used for haemodialysis is important especially for Legionella and non-fermentative bacteria since patients with end stage renal disease (ESRD) are suffering from deteriorated function of immune system. Materials and Methods: A total 50 water and dialysate samples were weekly collected over a period of 10 weeks from 5 sites. Total and faecal coliforms were determined by utilizing the most probable number (MPN) method. For isolation of Legionella, water samples were inoculated on a BCYE medium. DNA extraction was performed and was used to amplify 16S rRNA gene of Legionella species. Airborne bacteria were sampled using a single stage Andersen air sampler. Results: Out of total 50 water samples, 24 samples had bacterial contamination. The highest rate of Legionella contamination was observed in the storage tank (67 cfu/ml). Legionella was not isolated from the dialysate effluent samples. The highest rate of total bacterial count was related to the dialysate effluent and the maximum total count of coliforms was related to the reverse osmosis. The isolated bacteria were Gram-negative bacilli (mostly Pseudomonas isolates), Gram-positive cocci (mostly Micrococcus spp.) and Gram-positive bacilli (mostly Bacillus spp.). Six samples were contaminated with coliforms. No faecal coliform was isolated from the samples. Conclusion: These results indicated that dialysis machine is an important source of contaminations such as Staphylococcus, Pseudomonas and Legionella. Therefore an efficient prevention program is needed to eliminate bacterial contamination of dialysis water system. Moreover, in haemodialysis centres, periodic surveillance programs for microbiological qualification can lead to a better planning for disinfection of haemodialysis water systems. © 2016, Tehran University of Medical Science. All rights reserved

Molecular epidemiology and nitrofurantoin resistance determinants of nitrofurantoin-non-susceptible Escherichia coli isolated from urinary tract infections

Objectives: The worldwide emergence of multidrug-resistant uropathogens has resulted in the revival of old antibiotics such as nitrofurantoin (NIT) for the treatment of uncomplicated urinary tract infections (UTIs). This study aimed to identify determinants of NIT resistance and to investigate the genetic diversity of NIT-resistant (NIT-R) Escherichia coli isolates. Methods: Six NIT-R and three NIT-susceptible clinical E. coli isolates from patients with UTI were studied. The susceptibility of the isolates to various classes of antibiotics was evaluated by disk diffusion. The presence of plasmid-encoded efflux pump genes (oqxA and oqxB) was investigated by PCR. Nucleotide sequences of the nfsA, nfsB and ribE genes were determined. The genetic relatedness of the NIT-R isolates was evaluated by multilocus sequence typing (MLST). Results: All six NIT-R isolates were characterised with high-level NIT resistance (MIC � 512 mg/L) and they belonged to five distinct STs including ST131 (n = 2), ST73, ST405, ST10 and ST354 (n = 1 each). Amikacin, carbapenems, minocycline, tigecycline and fosfomycin were the most active agents against the studied uropathogens. The oqxA and oqxB genes were not detected in any isolate. All NIT-R isolates harboured inactivating genetic alterations in nfsA and nfsB NfsA H11Y, S33N, S38Y, W212R substitutions, �g638 (frameshift), �a64-g73 (frameshift) and NfsB F84S, P45S, W94Stop, E197Stop substitutions, �nfsB locus. The ribE gene of most isolates was unaffected, except for one isolate co-harbouring a deleterious RibE G85C substitution and NfsA/B alterations. Conclusion: NIT resistance in the studied E. coli isolates was mainly mediated by nfsA and nfsB alterations. © 201

Genotypic characterization of Staphylococcus aureus isolated from a burn centre by using agr, spa and SCCmec typing methods

Infections caused by Staphylococcus aureus remain a major global healthcare problem. We aimed to find the common lineages of S. aureus strains circulating in a burn hospital in Tehran. A total of 167 isolates of S. aureus obtained from patients, healthcare workers (HCWs) and environment in Shahid Motahari burn hospital were genotyped by using spa, agr and staphylococcal cassette chromosome mec (SCCmec) typing methods. Antimicrobial susceptibility testing was performed by using the disc diffusion method. The frequency of methicillin-resistant S. aureus (MRSA) was 64.7 (n = 108), with distribution frequencies among patient, HCW and surface isolates of 64.2 (n = 79), 50 (n = 7) and 73.3 (n = 22), respectively. SCCmec type III (75, n = 81) was found to be the most frequent SCCmec type among MRSA isolates, followed by SCCmec type I (20.4, n = 22) and SCCmec type IV (1.8, n = 2). The remaining MRSA isolates (2.8, n = 3) were nontypeable by this method. About 78.4 (n = 131), 10.2 (n = 17) and 4.8 (n = 8) of all isolates were characterized as agr types I, II and III, respectively, and the other isolates (6.6) were nontypeable. spa types t030 and t037 constituted the first and second most predominant spa types found in 56.4 (n = 57) and 25.6 (n = 26) of isolates, respectively. We also report here a novel spa type, t16471. The most prevalent genotypes of the isolates found among patient, surface and HCW samples were SCCmec type III/t030, t037/agr type I. Continuous tracking of epidemic isolates and better hospital infection control policies are recommended to efficiently prevent the spread of bacteria to inpatients. © 201

Alterations in Mesenteric Lymph Node T Cell Phenotype and Cytokine Secretion are Associated with Changes in Thymocyte Phenotype after LP-BM5 Retrovirus Infection

In this study, mouse MLN cells and thymocytes from advanced stages of LP-BM5 retrovirus infection were studied. A decrease in the percentage of IL-7+ cells and an increase in the percentage of IL-16+ cells in the MLN indicated that secretion of these cytokines was also altered after LP-BM5 infection. The percentage of MLN T cells expressing IL-7 receptors was significantly reduced, while the percentage of MLN T cells expressing TNFR-p75 and of B cells expressing TNFR-p55 increased. Simultaneous analysis of surface markers and cytokine secretion was done in an attempt to understand whether the deregulation of IFN-Υ secretion could be ascribed to a defined cell phenotype, concluding that all T cell subsets studied increased IFN-Υ secretion after retrovirus infection. Finally, thymocyte phenotype was further analyzed trying to correlate changes in thymocyte phenotype with MLN cell phenotype. The results indicated that the increase in single positive either CD4+CD8- or CD4- CD8+ cells was due to accumulation of both immature (CD3- ) and mature (CD3+) single positive thymocytes. Moreover, single positive mature thymocytes presented a phenotype similar to the phenotype previously seen on MLN T cells. In summary, we can conclude that LP-BM5 uses the immune system to reach the thymus where it interferes with the generation of functionally mature T cells, favoring the development of T cells with an abnormal phenotype. These new T cells are activated to secrete several cytokines that in turn will favor retrovirus replication and inhibit any attempt of the immune system to control infection

Nonlocal layerwise formulation for interfacial tractions in layered nanobeams

Interfacial tractions generated at the interface in two-layered nanobeams are studied through the stress-driven nonlocal theory of elasticity and an interface model. The model uses a layerwise description of the problem and satisfies the continuity conditions at the interface. The size-dependency are incorporated into formulation through a nonlocal constitutive law which defines the strain at each point as an integral convolution in terms of the stresses in all the points and a kernel. The Bernoulli-Euler beam theory is used separately for each layer to describe kinematic field, and to derive size-dependent system of coupled governing equations. The displacement components within the layers are derived and the interfacial tractions are obtained through the interfacial constitutive relations. Results are presented for the interfacial shear and normal tractions, exhibiting a different behavior at the nano-scale compared to those of the layered beams with large-scale dimensions including different maximum interfacial tractions and the location where maxima occur. A superior resistance of nanobeams against debondings and delaminations due to the interfacial normal tractions compared to that of the beams with large-scale dimensions is observed. The formulation and the understandings presented here are expected to stimulate further researches on multilayered nanobeams, including their interfacial fracture mechanics

Size-dependent linear elastic fracture of nanobeams

A nonlocal linear elastic fracture formulation is presented based on a discrete layer approach and an interface model to study cracked nanobeams. The formulation uses the stress-driven nonlocal theory of elasticity to account for the size-dependency in the constitutive equations, and the Bernoulli-Euler beam theory to define the kinematic field. Two fundamental mode I and mode II fracture nanospecimens with applications in Engineering Science are studied to reveal principal characteristics of the linear elastic fracture of beams at nanoscale. The domains are discretized both through the transverse and longitudinal directions and the field variables are derived by solving systems of the nonlocal equilibrium equations subjected to the variationally consistent and constitutive boundary and continuity conditions. The energy release rates of the fracture nanospecimens are calculated both from the global energy consideration and from the localized fields at the tip of the crack, i.e. the cohesive forces and the displacement jumps. The results are shown to be the same, proving the capability of the interface model to predict localized fields at the crack tip which are important for the cohesive fracture problems. It is found that the nanospecimens with higher nonlocality have higher fracture resistance and load bearing capacity due to higher energy absorptions and lower energy release rates. The crack propagation in the nanospecimens are also studied and load-displacement curves are presented. The nonlocality considerably increases the stiffness of the initial linear response of the nanospecimens. The fracture model is also able to capture the non-linear post-peak response and the unstable crack propagation, the snap-back instability, which is more intense for nanospecimens with higher nonlocality

Analysis of bond behavior of injected anchors in masonry elements by means of Finite Element Modeling

Injected anchors made of steel bars embedded in masonry elements by means of cement-based grout represented in the past a wide solution for avoiding out-of-plane mechanisms. Corrosion phenomena in steel bars reduced the effectiveness of such type of intervention over time. Innovative materials, as the Fiber Reinforced Plastic ones, can represent a suitable alternative to increase durability and performance of injected anchors. Since the effectiveness of injected anchors is strictly related to bond behaviour along both the bar-grout and the grout-masonry interfaces, a detailed analysis by means of a Finite Element model was developed for different types of bars embedded in masonry elements. The numerical model was firstly calibrated on some experimental results of pull-out tests available in literature and, then, is used for investigating the effects of several parameters on both local and global behaviour. Load-displacement curves and local distributions of shear stresses are examined in detail. The numerical analyses evidenced that the maximum tensile force in the anchor mainly depends on the shear strength of the bar-grout and the grout-masonry interfaces and on the embedded length, but for very long embedded length, it can be limited by the tensile failure in the anchor or in the masonry

Genetic similarity between adenoid tissue and middle ear fluid isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis from Iranian children with otitis media with effusion

Background: Otitis media with effusion (OME) is a common disease among children, in the pathogenesis of which bacterial infections play a critical role. It was suggested that adenoid tissue could serve as a reservoir for bacterial infection, the eustachian tubes being the migration routes of bacteria into the middle ear cavity. The aim of this study was to investigate the genetic similarity between isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, obtained from adenoid tissue and middle ear fluid. Methods: A total of 60 specimens of middle ear fluids (MEFs) and 45 specimens of adenoid tissue were obtained from 45 children with OME. All the samples were inoculated on culture media for bacterial isolation and identification. The genetic similarity between bacterial isolates was determined by pulsed-field gel electrophoresis (PFGE). Results: The same bacterial species were simultaneously isolated from adenoid tissue and MEFs of 14 patients, among which, 6 pairs of M. catarrhalis, 5 pairs of S. pneumoniae and 3 pairs of H. influenzae were identified. Conclusions: Based on the genetic similarities between isolate pairs, found by PFGE analysis, this study suggested that M. catarrhalis, S. pneumoniae and H. influenzae colonize the adenoid tissue, then migrate to the middle ear cavity and, hence, contribute to the total pathogenesis of OME. (C) 2013 Elsevier Ireland Ltd. All rights reserved