Methicillin resistant Staphylococcus aureus (MRSA) isolated in Saudi Arabia: epidemiology and antimicrobial resistance patterns

Methicillin resistant Staphylococcus aureus (MRSA) comprised about 7·5% per annum of all S. aureus isolated in a general hospital in Jeddah, Saudi Arabia during the 3 year period 1990–1992. Most isolates were from wound sites (71%). Resistance to gentamicin (83%) and tetracycline (93%) was frequently observed whilst resistance to ciprofloxacin (1%) and rifampicin (6%) was uncommon. Low levels of mupirocin resistance (MIC 8 mg 1⁻¹), were detected in 3% of all MRSA isolates.     

A laboratory-confirmed outbreak of rifampicin-methicillin resistant Staphylococcus aureus (RMRSA) in a newborn nursery

The routine laboratory monitoring of methicillin-resistant strains of Staphylococcus aureus (MRSA) at a large teaching hospital led to the detection of a new, multiply-resistant strain of MRSA, which was resistant not only to penicillin, oxacillin, methicillin, cephamandole, erythromycin, tetracycline, kanamycin and gentamicin but also to rifampicin and sulphamethoxazole-trimethoprim. The rifampicin-methicillin resistant strain of S. aureus (RMRSA) was first detected in blood cultures of babies from the newborn nursery. A bacteriological investigation of the nursery revealed the source to be a paediatric medical officer who was colonised with the resistant strain, and who at the time was receiving rifampicin for pulmonary tuberculosis. The rifampicin resistance was presumably acquired during rifampicin therapy. The outbreak in the nursery was brought to an abrupt end by treatment of the colonised medical officer with mupirocin, applied nasally twice a day for a week, and by the introduction of standard infection-control measures. Reference laboratory assistance was needed to confirm the initial assumption that the outbreak was caused by a single strain.     

Staphylococcus aureus clfB and spa alleles of the repeat regions are segregated into major phylogenetic lineages

To reliably differentiate among Staphylococcus aureus isolates we recently developed the Double Locus Sequence Typing (DLST) based on the analysis of partial sequences of clfB and spa genes. This method is highly discriminatory and gives unambiguous definition of types. The highly clonal population structure of S. aureus suggests that isolates with identical clfB or spa alleles belong to the same clonal complex (CC) defined by Multi-Locus Sequence Typing (MLST). To test this hypothesis as well as to investigate putative intra-CC genetic structure, we analyzed a total of 289 isolates (186 MSSA and 103 MRSA) with DLST-, spa- and MLST-typing.Among the 289 strains, 242 were clustered into 7 major MLST CCs, 40 into minor CCs and 7 were not grouped into CCs. A total of 205 DLST- and 129 spa-types were observed. With one exception, all DLST-clfB, DLST-spa and spa-type alleles were segregated into CCs. DLST-types sharing an identical allele (clfB or spa) were clustered using eBURST. Except for one strain, all isolates from each DLST cluster belonged to the same CC. However, using both DLST- and spa-typing we were not able to disclose a clear intra-CC structure. Nevertheless, the high diversity of these loci confirmed that they are good markers for local epidemiological investigations.     

Surveillance of methicillin-resistant Staphylococcus aureus in England and Wales, 1986–1990

The incidence of methicillin-resistant Staphylococcus aureus in England and Wales was monitored by a weekly reporting scheme from early 1986 to March 1990. Potential coverage was approximately two-thirds of hospital beds. Reporting centres fell from a peak of 210 in 1986 to a low of 101 centres early in 1989 with later recovery. There were 2367 positive reports in 1986, 2174 in 1987, 1700 in 1988, 1701 in 1989 and 632 in the first quarter of 1990. Colonizations outnumbered infections by 2:1. There were marked regional differences: North-East Thames was dominant in 1986 and 1987, and then declined; South-East Thames showed a dramatic increase in 1988 which continued. Other regions showed less significant changes but there were continuing problems in the South-Western Region and in the West Midlands. Some of these changes were related to the decline of EMRSA-1, possibly due to the introduction of effective control measures, and to the emergence of EMRSA-3 in South-East Thames and its spread to Wessex.     

The evolution of Staphylococcus aureus

A broad variety of infections, ranging from minor infections of the skin to post-operative wound infections can be caused by Staphylococcus aureus. The adaptive power of S. aureus to antibiotics leaded, in the early 1960s, to the emergence of methicillin-resistant S. aureus (MRSA). The cause of resistance to methicillin and all other β-lactam antibiotics is the mecA gene, which is situated on a mobile genetic element, the staphylococcal cassette chromosome mec (SCCmec). Seven major variants of SCCmec, type I to VII, are distinguished. The most important techniques used to investigate the molecular epidemiology of S. aureus are pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), S. aureus protein A (spa) typing and SCCmec typing (only for MRSA). These techniques have been used to study the evolution of the MRSA clones that have emerged since the early 1960s, and to study their subsequent worldwide dissemination. The early MRSA clones were hospital-associated (HA-MRSA). However, from the late 1990s, community-associated MRSA (CA-MRSA) clones emerged worldwide. CA-MRSA harbors SCCmec type IV, V or VII, the majority belong to other S. aureus lineages compared to HA-MRSA, and CA-MRSA is often associated with the presence of the toxin Panton-Valentine leukocidin (PVL). However, during recent years, the distinction between HA-MRSA and CA-MRSA has started to disappear, and CA-MRSA is now endemic in many US hospitals. MRSA probably originated trough the transfer of SCCmec into a limited number of methicillin-sensitive S. aureus (MSSA) lineages. This review describes the latest observations about the structure of SCCmec, the techniques used to study the molecular epidemiology and evolution of S. aureus as well as some challenges that researchers face in the future.     

Methicillin-resistant Staphylococcus aureus: investigation of a hospital outbreak using a case-control study

A retrospective case-control study of 50 MRSA-positive patients was carried out during an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) at an acute general hospital in London. Controls were randomly selected from MRSA-negative patients admitted during the outbreak period. Risk factors investigated included length of admission prior to screening, number of ward changes, main diagnosis, extent of staff contact, pressure sores, surgical and other invasive procedures and antibiotic treatment. Outcome variables examined were rates of infection (versus colonization) with MRSA and mortality. Patients with MRSA were in hospital longer before microbiological specimens were taken and moved wards more often than controls. In a logistic regression analysis, length of stay in hospital, pressure sores, physiotherapy and surgical procedures were associated with a significantly increased risk of acquiring MRSA. Odds ratios (and 95% confidence intervals) for having acquired MRSA were: 8·3 (1·02−71·43) if a patient had pressure sores; 3·7 (1·10−12·5) if they received physiotherapy; and 3·2 (1·82−10·0) if they underwent surgical procedures. The rate of clinical infection amongst patients with this strain of MRSA was 26% and included life-threatening infections such as septicaemia, underlining the potential virulence of MRSA. Surgery and physiotherapy may have been markers of debility. Physiotherapy was probably a marker of increased rates of contact with all hospital staff, and high standards of hand hygiene should be promoted amongst all staff as the most important factor in controlling an outbreak of MRSA. Good bed management is essential for hospital infection control.     

Methicillin-resistant Staphylococcus aureus in a teaching hospital: investigation of nosocomial transmission using a matched case-control study

In early 1996 a hospital-wide methicillin-resistant Staphylococcus aureus (MRSA) epidemic was recognized in a 900-bed university hospital. In order to investigate hospital-specific transmission routes, a case-control study was carried out. Cases and controls were matched for age (± 10 years), sex, admission date (± 10 days) and clinical department on admission. Data on potential risk factors, were retrieved by chart review. Between June 1996 and February 1997, 67 patients with hospital-acquired MRSA were identified. Molecular typing showed that 85% of the cases carried an indistinguishable strain. The average time at risk for cases and controls was 17.3 and 23.7 days, respectively (P= 0.01). Seventeen patients (25.4%) developed infection. Conditional multivariate regression analysis showed that intensity of care (P= 0.002), number of transfers (P= 0.019), and fluoroquinolone therapy (P= 0.025) were independently associated with acquisition of MRSA. Intensity of care can be considered as a surrogate marker for a number of manipulations which represent the main risk factors for MRSA transmission. Frequent transfers within the hospital hinder, not only the epidemiological analyses, but also efforts to bring an outbreak under control. Our findings give epidemiological support to recent molecular studies which suggest that fluoroquinolone use may increase the transmissibility of MRSA in hospitals.     

Clinical experience and outcomes of community-acquired and nosocomial methicillin-resistant Staphylococcus aureus in a northern Australian hospital

Methicillin-resistant Staphylococcus aureus (MRSA) is a well-recognized cause of hospital-acquired sepsis. We reviewed the clinical features of a new variant of community-acquired MRSA originally described from the Kimberley region of northern Western Australia (WA MRSA). This strain has become an increasing cause of community- and hospital-acquired sepsis at Royal Darwin Hospital (RDH) in the Northern Territory, especially in Aboriginal Australians from remote communities. Fifty percent of WA MRSA was community-acquired, with 76% in Aboriginals. Like the MRSA from eastern Australia (EA MRSA), WA MRSA commonly caused skin sepsis but was less likely to cause respiratory or urinary infections compared with EA MRSA. Twelve out of 125 (9·6%) WA MRSA and 7/93 (7·5%) EA MRSA infections were septicaemias. Septicaemia due to WA MRSA occurred in adult medical patients, especially those with temporary haemodialysis catheters, while EA MRSA septicaemia occurred throughout the hospital. Aboriginal people were more likely to develop both community- and hospital-acquired WA MRSA septicaemia [overall relative risk (RR) 12·3 (95% CI 3·7–40·7)]. Control of WA MRSA requires policies to reduce transmission in both hospitals and communities. Community-based control programmes need support for individual patient management, improved housing and hygiene, control of skin sepsis and appropriate use of antibiotics, especially in rural Aboriginal communities in northern Australia.     

Sustained low prevalence of meticillin-resistant Staphylococcus aureus upon admission to hospital in The Netherlands

The prevalence of meticillin-resistant Staphylococcus aureus (MRSA) carriage at hospital admission in The Netherlands was 0.03% in 1999–2000. The aim of the present study was to assess whether the prevalence of MRSA carriage in The Netherlands has changed over the last few years. In five Dutch hospitals, 6496 unique patients were screened for nasal S. aureus carriage at hospital admission by microbiological culture between 1 October 2005 and 7 June 2007. In total, 2036 of 6496 (31.3%) patients carried S. aureus in their nose, and seven of 6496 (0.11%) patients were nasal carriers of MRSA. Compared with 1999–2000, the prevalence of MRSA carriage in the Dutch population at hospital admission has increased more than three fold; however, this increase was not significant (P = 0.06, Fisher’s exact test). This prevalence is still among the lowest in the world, probably as a result of the stringent Dutch infection control policy, and the restrictive use of antibiotics in The Netherlands.     

Emergence and spread of low-level mupirocin resistance in methicillin-resistant Staphylococcus aureus isolated from a community hospital in Japan

The objective of this study was to investigate the state of mupirocin resistance in methicillin-resistant Staphylococcus aureus (MRSA) in a community hospital in Japan. Ninety strains of MRSA were isolated from the respiratory tract of 56 patients (group I, Jun 1990-Aug 1996) before introduction of mupirocin in Japan, which were compared with 168 strains from 48 patients (group II, Sept 1996-Jan 1998) and 146 strains from 85 patients (group III, Feb 1999-Dec 1999) isolated after introduction of mupirocin. Comparisons were made by determining the minimum inhibitory concentrations (MIC) against nine antibiotics. Fifty-five MRSA isolates from 27 patients [13 (27.1%) of 48 in group II and 14 (16.5%) of 85 in group III] after introduction of mupirocin showed low-level resistance to mupirocin (MIC, 6.25 to 50 microg/ml) but the remaining isolates were sensitive to mupirocin (MIC < or =3.13 microg/ml). Most patients colonized with low-level mupirocin-resistant MRSA were elderly (> or =65 years of age), on total parenteral nutrition or nasal feeding and had other underlying diseases. The proportion of patients colonized with low-level mupirocin-resistant MRSA following repeated use of mupirocin was higher in patients of group II than those of group III. Molecular typing by pulsed-field gel electrophoresis (PFGE) demonstrated that the pattern of 13 MRSA isolates from 13 patients of group II consisted of three patterns (A, B, C) with predominance of pattern A, while the pattern of 13 MRSA isolates from 13 patients of group III consisted of three patterns (A, C, D) with predominance of patterns A and D. Our results indicated that resistance of MRSA to mupirocin remains at a low level at present in Japan. However, we should be aware of the possible emergence of MRSA highly resistant to mupirocin in the future.     

上海嘉定区某医院2018—2022年环境中金黄色葡萄球菌的分布及其耐药性

目的 了解上海市嘉定区某医院环境中金黄色葡萄球菌(SA)的污染状况及耐药性,探讨环境菌株中耐甲氧西林金黄色葡萄球菌(MRSA)检出情况及耐药性特点。 方法 采集该医院环境标本并分离鉴定SA,采用肉汤稀释法对分离的SA进行15种常见抗菌药物耐药性检测,并检测菌株mecA基因。 结果 936份医院环境标本中,60份标本检出SA,检出率为6.41%,SA中MRSA的检出率为25.00%。综合重症监护病房(ICU)、呼吸内科SA的检出率分别为7.35%、5.94%,MRSA的检出率分别为3.51%、0.64%。医院环境中鼠标键盘SA的检出率最高(17.14%),其次是患者的病号服、枕头被褥和床头柜(均为16.67%)。环境标本中肥皂(盒)、洗手(消毒)瓶的MRSA检出率最高,分别为7.69%、6.25%。医院环境标本中的SA对达托霉素、利奈唑胺、呋喃妥因、利福平、复方磺胺甲唑、替考拉宁、万古霉素7种抗菌药物均敏感,MRSA对其余8种抗菌药物的耐药率均高于甲氧西林敏感金黄色葡萄球菌(MSSA)。 结论 该医院综合ICU环境检出的SA中MRSA的占比高于呼吸内科,环境标本中高MRSA检出率和高SA检出率的标本不一致,MRSA的耐药率高于MSSA,需加强医院,特别是ICU中SA及MRSA的消毒与控制,避免SA耐药性升高。     

金黄色葡萄球菌去定植在预防骨与关节手术感染的作用分析

金黄色葡萄球菌是引起骨与关节感染的常见病原体之一,可通过分泌毒素、生物膜形成等多种方式致病。由于金黄色葡萄球菌可在宿主鼻腔及其他部位长期定植,显著增加住院患者骨与关节感染风险。去定植已被证实可降低住院患者金黄色葡萄球菌骨与关节感染的发生率,既往常用的去定植药物(如莫匹罗星等)效果好,但由于诱导耐药、过敏反应等原因,临床上需要不断研发其他新型替代药物。本文将从金黄色葡萄球菌致病机制、定植,以及骨与关节感染的相关性等方面进行综述,旨在为金黄色葡萄球菌骨与关节感染的预防与治疗提供参考依据。     

Clinical and molecular characteristics of nosocomial meticillin-resistant Staphylococcus aureus skin and soft tissue isolates from three Indian hospitals

We analysed risk factors for nosocomial meticillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTIs) in three Indian hospitals. We also determined antimicrobial resistance patterns and genotypic characteristics of MRSA isolates using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and staphylococcal cassette chromosome (SCCmec) typing. Medical records of 709 patients admitted to three tertiary hospitals with nosocomial S. aureus SSTIs were clinically evaluated. Antimicrobial susceptibility testing of patient isolates was performed in accordance with Clinical and Laboratory Standards Institute guidelines, with meticillin and mupirocin resistance confirmed by multiplex polymerase chain reaction. PFGE analysis of 220 MRSA isolates was performed, followed by MLST and SCCmec typing of a selected number of isolates. MRSA was associated with 41%, 31% and 7.5% of infections at the three hospitals, respectively. Multiple logistic regression analysis identified longer duration of hospitalisation [odds ratio (OR): 1.78; OR: 2.83 for ≥20 days], intra-hospital transfer (OR: 1.91), non-infectious skin conditions (3.64), osteomyelitis (2.9), neurological disorders (2.22), aminoglycoside therapy (1.74) and clindamycin therapy (4.73) as independent predictors for MRSA SSTIs. MRSA isolates from all three hospitals were multidrug resistant, with fifteen clones (I–XV) recognised. A majority of the strains possessed type III cassette. The common sequence type (ST) 239 was considered the signature MLST sequence for PFGE clone III. This major MRSA clone III was closely related to the UK EMRSA-1 and was significantly more resistant to antibiotics. Dissemination of multidrug-resistant MRSA clones warrants continuous tracking of resistant genotypes in the Indian subcontinent.     

Decline in the rates of meticillin-resistant Staphylococcus aureus acquisition and bacteraemia in a general intensive care unit between 1996 and 2008

Analysis of admission and weekly screening and other cultures for meticillin-resistant Staphylococcus aureus (MRSA) taken in the intensive care unit (ICU) demonstrated a 75% reduction in the estimated rate of acquisition of MRSA between 1996 and June 2008. Four periods were defined by three events: a new ICU (December 1997); addition of a two-bed bay (January 2001); and extra infection control measures in ICU and the hospital generally, including screening of all admissions (December 2006). In ICU, acquisition/1000 bed-days decreased promptly in each successive period, 49.0 (34.4–63.6), 28.3 (21.7–34.9), 19.3 (16.3–22.3) and 11.8 (7.3–16.3) respectively, and MRSA bacteraemias/1000 bed-days decreased between the last three periods, 7.6 (4.7–10.5), 3.7 (2.6–4.8) and 0.4 (0–2.9) with no change in the proportion colonised progressing to bacteraemia and a small increase in the rate of other bacteraemias. From December 2006 prevalence of MRSA in admissions to ICU from general wards decreased from 13.5% (11.6–15.4) to 6.4% (4.0–8.8) consequent upon a reduction in estimated pre-ICU acquisition rate from 26.0 (22.7–29.3) to 9.4 (6.0–12.8)/1000 bed-days. These results suggest that the improved environment of the new ICU and its extension and the recent changes in infection control each contributed to the observed reductions in MRSA acquisition and subsequent bacteraemia within ICU. Improved infection control in the hospital was associated with decreased acquisition of MRSA on the general wards.     

金黄色葡萄球菌血流感染住院患儿临床特征及危险因素

目的 了解儿童金黄色葡萄球菌(SA)血流感染的临床特点以及菌株的药敏特征,探讨耐甲氧西林金黄色葡萄球菌(MRSA)血流感染和SA血流医院感染(HA)的易感因素。方法 回顾性分析2014年1月—2019年12月某儿童医院血培养检出SA住院患儿的病历资料,根据其药敏试验结果及来源分为MRSA组与甲氧西林敏感金黄色葡萄球菌(MSSA)组、HA组与社区感染(CA)组,应用卡方检验和logistic回归分析MRSA血流感染及HA血流感染的危险因素。结果 共纳入143例病例,男女比例为1.8∶1,<1岁71例(49.6%),病灶性血流感染90例(62.9%)。MARS组50例(35.0%),MSSA组93例(65.0%);HA组73例(51.0%),CA组70例(49.0%)。机械通气[OR=17.320,95%CI(1.576～190.399)]、抗菌药物联合使用[OR=0.580,95%CI(0.359～0.938)]是MRSA血流感染的独立危险因素(均P<0.05)。机械通气[OR=31.466,95%CI(1.434～690.538)]、入院前使用抗菌药物[OR=24.524,...     

Appearance of methicillin-resistant Staphylococcus aureus (MRSA) sensitive to gentamicin in a hospital with a previous endemic distinct MRSA

Since 1990 a clone of gentamicin and methicillin-resistant Staphylococcus aureus (MRSA) has remained endemic in our hospital, but since January 1996 a gentamicin-sensitive strain has progressively replaced the previous clone. We characterized the phenotypic and molecular pattern of the MRSA strains isolated in our hospital in 1996 and compared prospectively the epidemiological, clinical and evolutionary characteristics of ninety patients infected or colonized by gentamicin-sensitive MRSA (GS-MRSA) (49) and by gentamicin-resistant MRSA (GR-MRSA) (41). Finally we studied the variation of aminoglycoside consumption in our hospital from 1989 to 1996. We observed two antibiotypes (GS-MRSA and GR-MRSA) corresponding to two major chromosomal patterns. Patients with GS-MRSA usually acquired the infection 72 hours after hospital admission. No significant differences were observed in epidemiological characteristics, clinical presentation and evolution between patients with GS-MRSA and GR-MRSA. Since 1989 aminoglycoside intake in our hospital has decreased by 46%.     

Effect of systemic antibiotics and topical chlorhexidine on meticillin-resistant Staphylococcus aureus carriage in intensive care unit patients

Antibiotics and antiseptics have the potential to influence carriage and transmission of meticillin-resistant Staphylococcus aureus (MRSA), although effects are likely to be complex, particularly in a setting where multiple agents are used. Here admission and weekly MRSA screens and daily antibiotic and antiseptic prescribing data from 544 MRSA carriers on an intensive care unit (ICU) are used to determine the effect of these agents on short-term within-host MRSA carriage dynamics. Longitudinal data were analysed using Markov models allowing patients to move between two states: MRSA positive (detectable MRSA carriage) and MRSA negative (no detectable carriage). The effect of concurrent systemic antibiotic and topical chlorhexidine (CHX) on movement between these states was assessed. CHX targeted to MRSA screen carriage sites increased transition from culture positive to negative and there was also weaker evidence that it decreased subsequent transition from negative back to positive. In contrast, there was only weak and inconsistent evidence that any antibiotic influenced transition in either direction. For example, whereas univariate analysis found quinolones to be strongly associated with both increased risk of losing and then reacquiring MRSA carriage over time intervals of one day, no effect was seen with weekly models. Similar studies are required to determine the generalisability of these findings.     

Results of a multicentre randomised controlled trial of statistical process control charts and structured diagnostic tools to reduce ward-acquired meticillin-resistant Staphylococcus aureus: the CHART Project

Statistical process control (SPC) charts have previously been advocated for infection control quality improvement. To determine their effectiveness, a multicentre randomised controlled trial was undertaken to explore whether monthly SPC feedback from infection control nurses (ICNs) to healthcare workers of ward-acquired meticillin-resistant Staphylococcus aureus (WA-MRSA) colonisation or infection rates would produce any reductions in incidence. Seventy-five wards in 24 hospitals in the UK were randomised into three arms: (1) wards receiving SPC chart feedback; (2) wards receiving SPC chart feedback in conjunction with structured diagnostic tools; and (3) control wards receiving neither type of feedback. Twenty-five months of pre-intervention WA-MRSA data were compared with 24 months of post-intervention data. Statistically significant and sustained decreases in WA-MRSA rates were identified in all three arms (P<0.001; P=0.015; P<0.001). The mean percentage reduction was 32.3% for wards receiving SPC feedback, 19.6% for wards receiving SPC and diagnostic feedback, and 23.1% for control wards, but with no significant difference between the control and intervention arms (P=0.23). There were significantly more post-intervention 'out-of-control' episodes (P=0.021) in the control arm (averages of 0.60, 0.28, and 0.28 for Control, SPC and SPC+Tools wards, respectively). Participants identified SPC charts as an effective communication tool and valuable for disseminating WA-MRSA data.