Characterization of fusidic acid-resistant Staphylococcus aureus isolates in the community of Casablanca (Morocco)

Resistance to fusidic acid in Staphylococcus aureus is caused by mutation of the elongation factor G (EF-G) encoded by fusA or by expression of a protein, encoded by fusB or fusC, that protects the drug target. Other mechanisms involved in this resistance are mutations in the riboprotein L6 operon within rplF. The aim of this study was to determine the prevalence and mechanisms of resistance to fusidic acid in clinical isolates of S. aureus in Casablanca (Morocco) and to define the phenotypic and genotypic traits of these isolates and their clonal relationship. All fusidic acid-resistant S. aureus (FAR-SA) isolates were tested for fusB and fusC genes and were evaluated for the detection of mutations in fusA and fusE (rplF). fusB-positive strains were tested for a cadDX operon, encoding cadmium resistance. The agr group and the presence of toxin genes were monitored to characterize all FAR-SA isolates which were typed by pulsed-field gel electrophoresis (PFGE) and spa typing. Among 140 clinical S. aureus isolates collected in 2007 and 2008, 18 (～13%) exhibited resistance to fusidic acid. The most common resistance determinant was fusC, found in 16 isolates. Molecular typing showed that 14 of them harboured an agr group III and belonged to the same clonal complex (CC) spa type 127 and identical clonotype (cluster labelled A). These isolates also possessed the staphylococcal enterotoxin H gene. The second resistance determinant was fusB found in two isolates. These two isolates lacked cadDX gene and were found to belong to two unrelated clusters and spa types. While no isolate carrying mutations in rplF was found, 15 expressed a silent mutation in fusA (nucleotide 342). Only acquired fusidic acid resistance genes (mainly fusC) were prevalent among FAR-SA isolates with almost all of the clinical specimens belonging to CC-spa type 127. This study provides valuable data on the prevalence of fusidic acid-resistant S. aureus with the associated molecular mechanisms of resistance and the genetic background of the strains in Casablanca.     

The population structure of Staphylococcus aureus among general practice patients from The Netherlands

To investigate the prevalence, the antibiotic resistance pattern and the population structure of Staphylococcus aureus , S. aureus isolates from the anterior nostrils of patients of general practitioners (GPs) were analysed. Insight into the S. aureus population structure is essential, as nasal carriers of S. aureus are at increased risk of developing an S. aureus infection. S. aureus was isolated from nasal swabs from 2691 patients with no sign of an infection collected in 29 GP practices in The Netherlands. The susceptibility pattern for several classes of antibiotics was determined, as well as the S. aureus genetic background, using spa typing. S. aureus was isolated from 617 of the 2691 (23%) nasal swabs. The prevalences of resistance to ciprofloxacin, co-trimoxazole, fusidic acid, macrolides and mupirocin were 0.2%, 0%, 6%, 5% and 1%, respectively. Half of the isolates were associated with a genetic background common to the major methicillin-resistant S. aureus (MRSA) clones, e.g. clonal complex (CC)1, CC5, CC8, CC22, CC30 and CC45, and the remainder were mainly associated with CC7, CC12, CC15, CC26, CC51 and CC101. The low prevalences of resistance suggest that, in the Dutch situation, S. aureus isolates from patients visiting their GP because of complaints not related to infection do not represent a large reservoir of antibiotic resistance genes. Although no MRSA isolates were found, the genetic background of some of the S. aureus isolates is commonly observed among community-associated (CA)-MRSA clones (CC1, CC8 and CC30), and this might suggest that these isolates have the potential to become CA-MRSA.     

MOLECULAR TYPING OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS STRAINS BY PCR-RFLP OF SPA GENE: A REFERENCE LABORATORY PERSPECTIVE

Purpose: To characterize methicillin-resistant Staphylococcus aureus (MRSA) strains by molecular typing based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of spa gene and to assess the utility of spa genotyping over bacteriophage typing in the discrimination of the strains. Materials and Methods: Studies were undertaken on 125 MRSA strains representing the most predominant phage types and the non phage typeable strains. Strains were typed by bacteriophage typing and PCR-RFLP of spa gene. DNA sequence analysis of the amplified spa gene fragment of the representative RFLP patterns was performed using standard protocols. Results: All the strains resistant to oxacillin were found to contain mec A gene. Fifty-two per cent of these strains were typeable by the international basic set of 23 phages. Five different PCR-RFLP patterns were observed among 125 MRSA strains. Non phage typeable strains were differentiated into four PCR-RFLP patterns. Sequencing of the spa gene from the representative strains of each RFLP pattern confirmed the length of these restriction fragments due to variation in the 24 bp and the 174 bp tandem repeats. It also revealed the presence of three new spa repeat patterns. Conclusion: The study demonstrates the importance of spa genotyping in the discrimination of MRSA strains, which were otherwise indistinguishable by bacteriophage typing. spa genotyping allowed differentiation of strains within a particular phage type. Nucleotide sequencing of isolates of different PCR-RFLP patterns indicated a correlation between the RFLP patterns of a variable number of tandem repeats and the phage type. The study provides valuable information on the epidemiological characterization of MRSA strains.     

The use of Raman spectroscopy in the epidemiology of methicillin-resistant Staphylococcus aureus of human- and animal-related clonal lineages

In order to perform a cost-effective search and destroy policy for methicillin-resistant Staphylococcus aureus (MRSA), a quick and reliable typing method is essential. In an area with a high level of animal-related MRSA ST398, pulsed field gel electrophoresis (PFGE) typing and spa-typing are not sufficient to discriminate between co-incidental findings and true transmission of MRSA. This study is the first to retrospectively show the performance of Raman spectroscopy in 16 well-documented outbreaks. We analysed 525 isolates, 286 MRSA ST398 and 239 from other PFGE clusters with Raman spectroscopy. When epidemiologically linked isolates from the outbreaks were analysed with PFGE as the reference standard, Raman spectroscopy correctly identified 97% of cases that were indistinguishable from the index case. With Raman cluster analysis, the most dominant distinction was between MRSA ST398 and other MRSA of human clonal lineages. Within MRSA ST398, 22 different Raman clusters were identified. Raman typing correctly identified an ST398 (spa type t567) outbreak in a hospital setting. No direct correlation was observed between Raman clusters and spa types. We conclude that Raman spectroscopy is a quick and reliable method of MRSA typing, which can be used in outbreak settings and it is comparable to PFGE, with the added advantage that PFGE non-typeable isolates can also be readily typed using the same sample preparation protocol.     

耐甲氧西林金黄色葡萄球菌spa基因分型

目的 研究浙江省瑞安地区耐甲氧西林金黄色葡萄球菌(MRSA)的spa基因分型。 方法 采集2011年3-11月瑞安市人民医院检验科微生物室临床分离的金黄色葡萄球菌菌株,共100株。采用头孢西丁纸片法筛选耐甲氧西林金黄色葡萄球菌,PCR扩增MRSA spa基因的X区,测序后通过数据库进行分型。 结果 48株确证为MRSA,可分为16个型别,其中t030型15株,t437型12株,t6944型5株,t172型3株,t9538型2株,t5699、t148型、t179型、t1751型、t015型、t5554型、t127型、t159型、t062型、t163型各1株,同时发现1个新型t10149。 结论 瑞安地区MRSA的spa分型以t030和t437为主,t10149为新型菌种。     

临潼矿泉对心理健康影响的研究

目的 探讨临潼矿泉对人心理健康的影响.方法 选择新入伍健康战士40人进行20次一个疗程的矿泉水浸浴,在疗程前后分别进行症状自评量表(SCL-90)的测查,并与中国军人常模进行比较.结果 矿泉水浴后的SCL-90结果 均有下降,其中.躯体化、强迫、人际关系、抑郁、焦虑、恐怖、偏执等因子分差异非常显著(P＜0.01),精神病性差异显著(P＜0.05).结论 一定条件的矿泉水浴对心理健康有积极影响.