ABSTRACT
OBJECTIVES: Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) has been accounted as one of the main risk factors for the development of complicated nosocomial infections. The present study aimed to determine nasal carriage rate, antimicrobial susceptibility pattern and molecular characteristics of MRSA isolates. METHODS: This cross-sectional study was performed within 6 months period from July 2015 at 3 hospitals of Isfahan, Iran. Totally, 326 nasal samples were collected by cotton sterile swab from the nasal cavity of participants. Standard microbiological methods were used for identification S. aurues and MRSA isolates. Antibiotic susceptibility pattern was determined by the disc diffusion method according to the CLSI recommendation. Determination of SCCmec typing, agr groups, and virulence genes were performed by PCR method. RESULTS: Overall, 23.6% of cases were S. aureus carriers including, 23.4% (25/107) of HCWs and 23.7% (52/219) of patients. The rate of MRSA nasal carriages among patients was found to be 51.9% and 16% in HCWs. The highest levels of resistance among MRSA isolates were against ampicillin (93.5%) and tetracycline (83.4%); while, the most effective antibiotics were vancomycin and co-trimoxazole with 100% and 71%, susceptibility. The presence of hla and pvl genes was detected in 80.6% and 3.2% of MRSA isolates, respectively. SCCmec types I, III, IV and V were found in 16.1%, 25.8%, 25.8%, and 16.1% of isolates, respectively. Moreover, agr group I was the predominant type with 43.3. CONCLUSION: Our results showed a high rate of MRSA colonization in hospitalized patients which remains a significant healthcare problem in our region.
Subject(s)
Carrier State/epidemiology , Inpatients , Medical Staff, Hospital , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Nasal Cavity/microbiology , Staphylococcal Infections/epidemiology , Adult , Bacterial Proteins/genetics , Bacterial Toxins/genetics , Carrier State/microbiology , Cross Infection/microbiology , Cross-Sectional Studies , Drug Resistance, Multiple, Bacterial , Exotoxins/genetics , Female , Hemolysin Proteins/genetics , Hospitals, Urban/statistics & numerical data , Humans , Iran/epidemiology , Leukocidins/genetics , Male , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/drug effects , Methicillin-Resistant Staphylococcus aureus/genetics , Multiplex Polymerase Chain Reaction , Staphylococcal Infections/microbiology , Trans-Activators/genetics , Virulence/geneticsSubject(s)
Drug Resistance, Bacterial/genetics , Macrolides/therapeutic use , Staphylococcal Infections/microbiology , Staphylococcus/genetics , Anti-Bacterial Agents/therapeutic use , Bacterial Proteins/genetics , Genotype , Humans , Iran , Membrane Proteins/genetics , Penicillin-Binding Proteins , Phenotype , Staphylococcal Infections/drug therapy , Staphylococcus/isolation & purificationABSTRACT
A two-component model is developed consisting of a discrete loop of cardiac cells that circulates action potentials as well as a pacing mechanism. Physiological properties of cells such as restitutions of refractoriness and of conduction velocity are given via experimentally measured functions. The dynamics of circulating pulses and the pacer's action are regulated by two threshold relations. Patterns of spontaneous initiations and terminations of reentry (SITR) generated by this system are studied through numerical simulations and analytical observations. These patterns can be regular or irregular; causes of irregularities are identified as the threshold bistability (T-bistability) of reentrant circulation and in some cases, also phase-resetting interactions with the pacer.
