Characterization of nasal methicillin-resistant Staphylococcus aureus isolated from international human and veterinary surgeons

PURPOSE

Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is poorly described for surgeons, despite the increased exposure to nosocomial pathogens and at-risk patients. This study investigated the molecular epidemiology and antimicrobial resistance of 26 MRSA isolates cultured from the nares of an international cross-sectional study of 1166 human and 60 veterinary surgeons.

METHODOLOGY

All isolates were subjected to agr, spa and multilocus sequence typing, and the presence of 22 virulence factors was screened for by PCR. Additionally, biofilm-forming ability, haemolytic activity, staphyloxanthin production and antibiotic resistance were determined. The genome of a rifampicin-resistant MRSA was sequenced.

RESULTS

Approximately half of the isolates belonged to well-described clonal lineages, ST1, ST5, ST8, ST45 and ST59, that have previously been associated with severe infections and increased patient mortality. Two of the three veterinarian MRSA belonged to epidemic livestock-associated MRSA clonal lineages (ST398 and ST8) previously associated with high transmission potential between animals and humans. The isolates did not display any consistent virulence gene pattern, and 35 % of the isolates carried at least one of the Panton-Valentine leukocidin (lukFS-PV), exfoliative toxin (eta) or toxic shock syndrome (tst) genes. Resistance to rifampicin was detected in one veterinarian isolate and was found to be due to three mutations in the rpoB gene.

CONCLUSION

Surgeons occupy a critical position in the healthcare profession due to their close contact with patients. In this study, surgeons were found to be colonized with MRSA at low rates, similar to those of the general population, and the colonizing strains were often common clonal lineages.

Antibiotic Resistance of Commensal Staphylococcus aureus and Coagulase-Negative Staphylococci in an International Cohort of Surgeons: A Prospective Point-Prevalence Study

Nasal colonization with antibiotic resistant bacteria represents both a risk factor for the colonized individual and their immediate contacts. Despite the fact that healthcare workers such as orthopedic surgeons are at a critical interface between the healthcare environment and an at-risk patient population, the prevalence of antibiotic resistant bacteria within the surgical profession remains unclear. This study offers a snapshot of the rate of nasal colonization of orthopedic surgeons with multi-resistant staphylococci including methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCoNS). We performed a prospective, observational study obtained at a single time point in late 2013. The participants were active orthopedic, spine and head & neck surgeons from 75 countries. The prevalence of nasal carriage of the different bacteria and the corresponding 95% confidence interval were calculated. From a cohort of 1,166 surgeons, we found an average S. aureus nasal colonization rate of 28.0% (CI 25.4;30.6) and MRSA rate of 2.0% (CI 1.3;2.9), although significant regional variations were observed. The highest rates of MRSA colonization were found in Asia (6.1%), Africa (5.1%) and Central America (4.8%). There was no MRSA carriage detected within our population of 79 surgeons working in North America, and a low (0.6%) MRSA rate in 657 surgeons working in Europe. High rates of MRCoNS nasal carriage were also observed (21.4% overall), with a similar geographic distribution. Recent use of systemic antibiotics was associated with higher rates of carriage of resistant staphylococci. In conclusion, orthopedic surgeons are colonized by S. aureus and MRSA at broadly equivalent rates to the general population. Crucially, geographic differences were observed, which may be partially accounted for by varying antimicrobial stewardship practices between the regions. The elevated rates of resistance within the coagulase-negative staphylococci are of concern, due to the increasing awareness of their importance in hospital acquired and device-associated infection.

Perception vs Reality: Methicillin-Resistant Staphylococcus aureus Carriage Among Healthcare Workers at a Veterans Affairs Medical Center

In a prevalence study of 209 healthcare workers, 18 (8.6%) and 13 (6.2%) carried methicillin-resistant Staphylococcus aureus in their nares or on their hands, respectively. However, 100 (62%) of 162 workers completing an associated survey believed themselves to be colonized, revealing a knowledge deficit about methicillin-resistant Staphylococcus aureus epidemiology. Infect. Control Hosp. Epidemiol. 2015;37(1):110-112.

Nasal carriage of Staphylococcus aureus among surgeons and surgical residents: a nationwide prevalence study

BACKGROUND

Staphylococcus aureus nasal carriage is an independent risk factor for developing nosocomial infections and for developing surgical site infection (SSI) in particular. The number of post-operative nosocomial S. aureus infections can be reduced by screening patients and decolonizing nasal carriers. In addition to patients, health care workers may also be S. aureus nasal carriers. The aim of this study was to explore S. aureus nasal carriage rates among surgeons.

METHODS

Nasal swabs were collected from surgeons and surgical residents during a national surgical congress. The control group consisted of non-hospitalized patients. Staphylococcus aureus carriage was detected using selective chromogenic agars by use of a fully automated inoculator. Suspected colonies were identified further by positive catalase and slide coagulation reactions.

RESULTS

Samples were collected from 366 surgeons and surgical residents and 950 control patients. The S. aureus nasal carriage rate among surgeons and residents was significantly greater compared with the control group (45.4% versus 30.8%, odds ratio [OR] 1.86 [1.45-2.38], p<0.001). No significant difference in carriage rate was found between surgeons and residents (46.8% versus 43.3%, p=0.769) and years of experience as a surgeon was not associated with a greater carriage rate. Male gender was an independent risk factor for carriage among physicians odds ratio ([OR] 1.90 [95% confidence interval 1.19-3.01], p=0.007).

CONCLUSIONS

The nationwide rate of S. aureus nasal carriage among surgeons and surgical residents proved to be significantly greater compared with a non-hospitalized patient control group. Male gender is an independent risk factor for carriage among physicians. Future studies are needed to investigate the possible relation with nosocomial post-operative S. aureus infections.

Role of healthcare apparel and other healthcare textiles in the transmission of pathogens: a review of the literature

Healthcare workers (HCWs) wear uniforms, such as scrubs and lab coats, for several reasons: (1) to identify themselves as hospital personnel to their patients and employers; (2) to display professionalism; and (3) to provide barrier protection for street clothes from unexpected exposures during the work shift. A growing body of evidence suggests that HCWs' apparel is often contaminated with micro-organisms or pathogens that can cause infections or illnesses. While the majority of scrubs and lab coats are still made of the same traditional textiles used to make street clothes, new evidence suggests that current innovative textiles function as an engineering control, minimizing the acquisition, retention and transmission of infectious pathogens by reducing the levels of bioburden and microbial sustainability. This paper summarizes recent literature on the role of apparel worn in healthcare settings in the acquisition and transmission of healthcare-associated pathogens. It proposes solutions or technological interventions that can reduce the risk of transmission of micro-organisms that are associated with the healthcare environment. Healthcare apparel is the emerging frontier in epidemiologically important environmental surfaces.

MRSA carriage among healthcare workers in non-outbreak settings in Europe and the United States: a systematic review

Abstarct

Methicillin-resistant Staphylococcus aureus colonization among health care workers in a downtown emergency department in Toronto, Ontario

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) acquired in the community, otherwise known as community-acquired MRSA, has emerged rapidly in recent years. Colonization with MRSA has been associated with an increased risk of symptomatic and serious infections and, in some settings, health care workers (HCWs) exhibit a higher prevalence of MRSA colonization.

OBJECTIVE

To determine MRSA colonization in emergency department (ED) HCWs in the setting of a moderate prevalence of MRSA in skin and soft tissue infections.

METHODS

The present study was conducted at a downtown ED in Toronto, Ontario. ED HCWs completed a brief questionnaire and swabs were taken from one anterior nare, one axilla and any open wounds (if present). Swabs were processed using standard laboratory techniques.

RESULTS

None of the 89 staff (registered nurses [n=55], physicians [n=15], other [n=19]) were MRSA positive and 25 (28.1%) were colonized with methicillin-susceptible S aureus.

CONCLUSIONS

Contrary to common belief among HCWs and previous studies documenting MRSA colonization of HCWs, MRSA colonization of this particular Canadian ED HCW cohort was very low and similar to that of the local population.

Risk ofStaphylococcus aureuscarriage in childcare employees

Asymptomatic carriage ofStaphylococcus aureusis an important risk factor for developing infection, as well as a key contributor to transmission. Despite the fact that childcare workers are at known risk for infections, little research has focused on bacterial carriage in this occupational group. We conducted a cross-sectional study comparing the prevalence ofS. aureusin 110 childcare employees with the prevalence in 111 unexposed participants. Questionnaire data was collected for employees, unexposed adults, and children. Multivariate analysis allowed for adjustment for confounders. Data on work-related exposures are presented as well. The prevalence ofS. aureusin employees, unexposed adults, children, and on surfaces was 35·2%, 33·6%, 19·8%, and 9·8%, respectively. Washing children's hands upon their arrival at childcare facilities may decrease the risk ofS. aureuscarriage in employees (odds ratio 0·17, 95% confidence interval 0·095–0·32,P < 0·0001).

Transmission dynamics of methicillin-resistant Staphylococcus aureus in a medical intensive care unit

Intensive care units (ICUs) play an important role in the epidemiology of methicillin-resistant Staphyloccocus aureus (MRSA). Although successful interventions are multi-modal, the relative efficacy of single measures remains unknown. We developed a discrete time, individual-based, stochastic mathematical model calibrated on cross-transmission observed through prospective surveillance to explore the transmission dynamics of MRSA in a medical ICU. Most input parameters were derived from locally acquired data. After fitting the model to the 46 observed cross-transmission events and performing sensitivity analysis, several screening and isolation policies were evaluated by simulating the number of cross-transmissions and isolation-days. The number of all cross-transmission events increased from 54 to 72 if only patients with a past history of MRSA colonization are screened and isolated at admission, to 75 if isolation is put in place only after the results of the admission screening become available, to 82 in the absence of admission screening and with a similar reactive isolation policy, and to 95 when no isolation policy is in place. The method used (culture or polymerase chain reaction) for admission screening had no impact on the number of cross-transmissions. Systematic regular screening during ICU stay provides no added-value, but aggressive admission screening and isolation effectively reduce the number of cross-transmissions. Critically, colonized healthcare workers may play an important role in MRSA transmission and their screening should be reinforced.

Unexpected absence of meticillin-resistant Staphylococcus aureus nasal carriage by healthcare workers in a tertiary hospital in Kenya

Healthcare workers (HCWs) are a major reservoir of meticillin-resistant Staphylococcus aureus (MRSA). A cross-sectional study was conducted between July and December 2010 to determine the prevalence of nasal carriage of MRSA at the Aga Khan University Hospital Nairobi. Nasal swabs were taken from 246 randomly selected HCWs. MRSA was identified using both phenotypic and genotypic methods. The prevalence of MRSA carriage was 0% [95% confidence interval (CI): 0-1.5%] whereas that of meticillin-susceptible Staphylococcus aureus was 18.3% (95% CI: 14.0-23.6%). Given the absence of MRSA in our hospital, screening HCWs should be limited to an outbreak setting.

Should healthcare workers be screened routinely for meticillin-resistant Staphylococcus aureus? A review of the evidence

Meticillin-resistant Staphylococcus aureus (MRSA) is considered endemic in the UK National Health Service (NHS), and routine MRSA screening of hospital inpatients has recently been introduced in both Scotland and England. The UK National Screening Committee states that public pressure for widening the eligibility criteria of a proposed screening programme should be anticipated and any related decisions scientifically justifiable. A literature review was conducted to examine whether MRSA screening in Scotland should be expanded to include the routine screening of healthcare workers (HCWs). There are no published prevalence studies reporting the overall MRSA carriage rate in HCWs in NHS hospitals. Estimates of HCW carriage from the worldwide literature vary widely depending on the country, hospital specialty and setting (endemic, non-endemic or outbreak). Recent studies conducted in endemic hospital settings report non-outbreak carriage rates of 0-15%. The role of HCW carriage in the transmission of MRSA is not well understood. Persistent carriage could act as a reservoir for infection and HCWs have been implicated as the source in a number of published outbreak reports. There are no published controlled trials examining the impact of routine HCW screening as an intervention in the prevention and control of MRSA infections in the endemic hospital setting. Most of the evidence for HCW screening comes from outbreak reports where the outbreak was brought to an end following the introduction of staff screening as part of a suite of infection control measures. Further research is required before a recommendation could be made to introduce routine MRSA screening of HCWs in the NHS in Scotland.

Sensitivy to antibiotics in strains of S. aureus isolated from cow´s milk

Strains of S. aureus were isolated from individual milk samples of 500 lacting cows from different areas in Slovakia (PH 1 - Košice region, 300 samples; PH 2 - Žilina region, 200 samples). The statistical significance between both dairy farms included in the experiment in the presence of genus Staphylococcus isolated on Baird-Parker agar from milk samples was p < 0,0001(***) . Totally, 122 milk samples were positive for the presence of Staphylococcus aureus (83 Košice regions, 52 Žilina regions). All 122 isolates of S. aureus were sensitive for the methicilin as detected by interpretative criteria developed by NCCLS (2002). For 122 S. aureus isolates, we compared antibiotic susceptibility results determined by the standardized agar diffusion assay with the PCR assay for the detection of antibiotic resistance mecA gene. For all isolates, we found a correlation between the results of the PCR and those of classical resistance testing. The obtained results were confirmed by PCR analysis, according to which, any of our tested isolate of S. aureus from all 122 individual milk samples from both experimental dairy farms were not positive for the presence of mecA gene coding  the methicilin resistance.

Epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization among patients and healthcare workers in a Portuguese hospital: a pre-intervention study toward the control of MRSA

This two-year study investigated the epidemiology of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) among patients and healthcare workers (HCWs) in two wards with a high frequency of MRSA isolation, at Hospital Geral de Santo António (HGSA), Portugal. Three point-prevalence surveys per year were carried out. A case-control approach was used to identify potential risk factors associated with MRSA carriage among patients. Incidence rates and risk factors of MRSA carriage among HCWs who were negative at the baseline observation were estimated. Prevalence of MRSA carriage among 276 patients screened was 5.1%. Admission to HGSA or attendance to the Diabetic Foot Outpatient Unit (DFOU) of HGSA within the past 12 months, and previous MRSA isolation were significant risk factors for MRSA carriage. Among HCWs (n = 126), the prevalence of MRSA carriage was 4.8% and the incidence rate was 61/1000 person-years. Nurses and nurse aids were the HCW categories with the highest risk of becoming colonized with MRSA over time (p = 0.01). One HCW chronically colonized was detected. Molecular typing revealed a clonal identity for isolates recovered from patients and HCWs of the same wards, with 88.6% of isolates belonging to the EMRSA-15 (ST22-MRSA-IV) clone.

Methicillin-resistant Staphylococcus aureus infection in septorhinoplasty

OBJECTIVES

Review the literature on methicillin-resistant Staphylococcus aureus (MRSA) infection following septorhinoplasty, identify patient groups at risk for MRSA complications following septorhinoplasty, and evaluate the need for antibiotic prophylaxis in these patients.

DISCUSSION

Patients who are susceptible to MRSA infections may also be at higher risk for nasal colonization, and this includes elderly patients, patients recently hospitalized or treated in a rehabilitation center, and healthcare workers. Few cases of MRSA infection following septorhinoplasty have been reported in the literature. Prevention of nosocomial and postsurgical MRSA infections has been well studied, and it seems that elimination of nasal colonization is a major step in preventing these infections.

CONCLUSIONS

Patients at increased risk for MRSA colonization should be screened prior to septorhinoplasty and if positive treated with antibiotic prophylaxis consisting of elimination of nasal carriage prior to surgery. Perioperative systemic antibiotic use should be considered, especially in revision cases.

Prevalence of Staphylococcus aureus colonization in orthopaedic surgeons and their patients: a prospective cohort controlled study

BACKGROUND

Methicillin-resistant Staphylococcus aureus and methicillin-sensitive Staphylococcus aureus surgical site infections are an increasing health problem in the United States. To date, no study, as far as we know, has evaluated the prevalence of Staphylococcus aureus colonization in orthopaedic surgeons. The purpose of our study was to assess the prevalence of methicillin-resistant Staphylococcus aureus and methicillin-sensitive Staphylococcus aureus colonization in orthopaedic surgery attending surgeons and residents at our institution compared with that in our high-risk patients.

METHODS

We performed nasal swab cultures in seventy-four orthopaedic attending surgeons and sixty-one orthopaedic surgery residents at our institution, screening for methicillin-resistant Staphylococcus aureus and methicillin-sensitive Staphylococcus aureus. We compared these results with a prospective database of nasal cultures of patients undergoing joint replacement and spine surgery.

RESULTS

A total of 135 physicians were screened. Of those physicians, 1.5% were positive for methicillin-resistant Staphylococcus aureus and 35.7% were positive for methicillin-sensitive Staphylococcus aureus. None of the sixty-one residents were positive for methicillin-resistant Staphylococcus aureus. However, 59% were positive for methicillin-sensitive Staphylococcus aureus. Of the seventy-four attending surgeons, 2.7% were positive for methicillin-resistant Staphylococcus aureus and 23.3%, for methicillin-sensitive Staphylococcus aureus. Previous studies at our institution have demonstrated a 2.17% prevalence of nasal carriage of methicillin-resistant Staphylococcus aureus and an 18% rate of methicillin-sensitive Staphylococcus aureus in high-risk patients. Thus, no difference was found between the prevalence of methicillin-resistant Staphylococcus aureus in residents or attending surgeons and that in the high-risk patients. However, the prevalence of methicillin-sensitive Staphylococcus aureus colonization in the surgeons (35.7%) was significantly higher than that in the high-risk patient group (18%) (p < 0.01).

CONCLUSIONS

At a major teaching hospital, a higher prevalence of methicillin-sensitive Staphylococcus aureus colonization was found among attending and resident orthopaedic surgeons compared with a high-risk patient group, but the prevalence of methicillin-resistant Staphylococcus aureus colonization was similar.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Prevalence of methicillin-resistant and methicillin-susceptible s. aureus in the saliva of health professionals

INTRODUCTION

S. aureus is one of the main agents of nosocomial infection and is sometimes difficult to treat with currently available active antimicrobials.

PURPOSE

To analyze the prevalence of methicillin-susceptible S.aureus (MSSA) and methicillin-resistant S. aureus (MRSA) as well as the MRSA antimicrobial susceptibility profile isolated in the saliva of health professionals at a large public education hospital.

MATERIALS AND METHODS

The project was approved by the research and ethics committee of the institution under study. Three samples of saliva from 340 health professionals were collected. The saliva analysis used to identify S. aureus was based on mannitol fermentation tests, catalase production, coagulase, DNAse, and lecithinase. In order to detect MRSA, samples were submitted to the disk diffusion test and the oxacillin agar screening test. In order to identify the minimum inhibitory concentration, the Etest technique was used.

RESULTS

The prevalence of MSSA was 43.5% (148/340), and MRSA was 4.1% (14/340). MRSA detected by the diffusion disk test, was 100% resistant to penicillin and oxacillin, 92.9% resistant to erythromycin, 57.1% resistant to clindamycin, 42.9% resistant to ciprofloxacin and 57.1% resistant to cefoxetin.

CONCLUSION

This subject is important for both the education of health professionals and for preventative measures. Standard and contact-precautions should be employed in professional practice.

Prevalence of methicillin-resistant Staphylococcus aureus nasal carriage in healthcare workers

Thirty (12%) of 257 healthcare workers were colonized with methicillin-resistant Staphylococcus aureus (MRSA). There was no significant difference in MRSA colonization among physicians (13%), nurses (12%), and other healthcare professionals (11%). Potential risk factors for MRSA colonization were found in 90% or more of all subjects, including those with MRSA and methicillin-susceptible S. aureus nasal carriage, as well as in persons who were not colonized.

The role of healthcare personnel in the maintenance and spread of methicillin-resistant Staphylococcus aureus

Healthcare workers may acquire methicillin-resistant Staphylococcus aureus (MRSA) from patients, both hospital and home environments, other healthcare workers, family and public acquaintances, and pets. There is a consensus of case reports and series which now strongly support the role for MRSA-carrying healthcare personnel to serve as a reservoir and as a vehicle of spread within healthcare settings. Carriage may occur at a number of body sites and for short, intermediate, and long terms. A number of approaches have been taken to interrupt the linkage of staff-patient spread, but most emphasis has been placed on handwashing and the treatment of staff MRSA carriers. The importance of healthcare workers in transmission has been viewed with varying degrees of interest, and several logistical problems have arisen when healthcare worker screening is brought to the forefront. There is now considerable support for the screening and treatment of healthcare workers, but it is suggested that the intensity of any such approach must consider available resources, the nature of the outbreak, and the strength of epidemiological associations. The task of assessing healthcare personnel carriage in any context should be shaped with due regard to national and international guidelines, should be honed and practiced according to local needs and experience, and must be patient-oriented.

Prevalence of Staphylococcus aureus nasal colonization in emergency department personnel

STUDY OBJECTIVE

Nasal colonization with Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) can precede infection in patients and contacts. Although general population S aureus/MRSA rates are well described, the prevalence of S aureus and MRSA nasal colonization in emergency department health care workers is not defined. We seek to determine the prevalence of S aureus and MRSA nasal colonization among ED health care workers without evidence of an active site of staphylococcal infection and identify variables associated with colonization.

METHODS

We prospectively studied a convenience sample of ED health care workers from 5 urban teaching hospitals in Pittsburgh, PA. Each participant completed a questionnaire and nasal culturing. We tested susceptibility with the oxacillin disc diffusion method. We analyzed data with descriptive statistics and univariate regression, with alpha set at 0.05.

RESULTS

Of 255 subjects, 23% were physicians; 62% were nurses, nursing assistants, or patient care technicians; and 15% were clerical staff or social service workers. Of 81 (31.8%) S aureus isolates, 11 (13.6%) were MRSA, an overall prevalence of 4.3%. All positive MRSA samples were from nurses, nursing assistants, or patient care technicians. No other covariate had an association with S aureus or MRSA colonization.

CONCLUSION

In this urban ED health care worker population, the prevalence of S aureus is similar but MRSA nasal colonization is higher than previously reported estimates in the general population of the United States. Physicians and nonpatient contact ED health care workers did not have MRSA colonization.