Persistence Of Methicillin-resistant Staphylococcus Aureus Research Articles

Diversity and persistence of MRSA and VRE in skilled nursing facilities: environmental screening, whole-genome sequencing and development of a dispersion index

Environmental contamination with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) in skilled nursing facilities (SNFs) may contribute to patient acquisition. We assessed diversity and association of MRSA and VRE isolates in a SNF wing and developed a mathematical index to define each strain's tendency to persist in rooms and spread horizontally. Longitudinal study of MRSA and VRE colonization and contamination among successive patient occupancies in a cluster of nine SNF private rooms during eight months characterized by microbiological testing and whole genome isolate typing. 'Dispersion index" of a strain is defined as the number of rooms it was found in (including the patient), divided by the average of times it was found consecutively in the same room. MRSA (ten strain types) and VRE (seven types) were recovered from room or patient in 16.4% and 35.6% of the occupancies, respectively. MRSA showed moderate horizontal spread and several episodes of same-room persistence (three distinct strain types) (overall dispersion index: 1.08). VRE showed high tendency towards horizontal spread /new introductions (overall dispersion index: 3.25), and only one confirmed persistence episode. The emerging picture of high diversity among contaminating strains and high likelihood of room persistence despite terminal cleaning (MRSA) and horizontal spread between rooms (VRE) in this setting calls for improved cleaning practices, heightened contact precautions, and most of all to establish individually tailored facility screening programs to enable informed choices based on local, measurable and actionable epidemiologic parameters. University of Michigan OAIC REC Scholarship to M.C. National Institutes of Health K24 AG050685 to L.M.

Transcriptome Analyses of Prophage in Mediating Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections represent a significant subset of S. aureus infections and correlate with exceptionally high mortality. We have recently demonstrated that the lysogenization of prophage ϕSA169 from a clinical persistent MRSA bacteremia isolate (300-169) into a clinical resolving bacteremia MRSA isolate (301-188) resulted in the acquisition of well-defined in vitro and in vivo phenotypic and genotypic profiles related to persistent outcome. However, the underlying mechanism(s) of this impact is unknown. In the current study, we explored the genetic mechanism that may contribute to the ϕSA169-correlated persistence using RNA sequencing. Transcriptomic analyses revealed that the most significant impacts of ϕSA169 were: (i) the enhancement of fatty acid biosynthesis and purine and pyrimidine metabolic pathways; (ii) the repression of galactose metabolism and phosphotransferase system (PTS); and (iii) the down-regulation of the mutual prophage genes in both 300-169 and 301-188 strains. In addition, the influence of different genetic backgrounds between 300-169 and 301-188 might also be involved in the persistent outcome. These findings may provide targets for future studies on the persistence of MRSA.

Diversity and persistence of MRSA and VRE in nursing homes: Environmental screening and whole-genome sequencing

Background: Transmission of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) is of special concern among frail patients in nursing homes. To understand environmental contamination patterns in this setting, we screened a suitable section of a nursing home over time and assessed MRSA and VRE prevalence in patients and their rooms. We were especially interested in assessing whether MRSA and VRE strains persist in rooms during changes of occupancy after patient discharge. Methods: We conducted a prospective cohort study of MRSA and VRE colonization and contamination among successive patients in a cluster of 9 single-occupancy rooms. Using flocked swabs, 5 high-touch surfaces were screened 3 times a week for 34 weeks. Patients were also screened (ie, nares, groin, and hands), if they agreed to participate. Whole-genome sequencing was performed on 67 nonredundant MRSA and VRE strains. Single-nucleotide polymorphism heatmaps and similarity trees were generated to evaluate strain diversity and persistence the facility. Results: Overall, 146 distinct occupancy events were captured during the study (16.5 average per room; range, 11–22), with 387 study visits and 4,670 total swabs collected. All rooms were contaminated with VRE, and 8 of 9 were contaminated with MRSA at least once during the study period. New contamination of a room with MRSA or VRE was observed in 43 (23%) of 185 opportunities, with potential persistence during occupancy changes in 25 (32.9%) of 76 opportunities. Sequencing of 67 nonredundant isolates identified at least 6 enterococcal clades and 10 MRSA clades (6 USA100 and 4 USA300), indicating a high degree of diversity and probably multiple introductions in the facility during the study time. In 3 separate cases, whole-genome sequencing confirmed persistence of a specific MRSA strain during a change of room occupancy, including 1 case of a MRSA strain persisting in a clean room before admission of the next patient. For VRE, 2 cases of persistence during room occupancy changes were confirmed, along with 6 cases of possible persistence (contamination across noncontiguous room occupancy events). Conclusions: Active surveillance screening and a recurring evaluation of terminal cleaning procedures should be considered due to high levels of circulation and persistence of MRSA and VRE in the nursing home setting.Funding: NoneDisclosures: None

PEGylation of Polyethylenimine Lowers Acute Toxicity while Retaining Anti-Biofilm and β-Lactam Potentiation Properties against Antibiotic-Resistant Pathogens.

Bacterial biofilms, often impenetrable to antibiotic medications, are a leading cause of poor wound healing. The prognosis is worse for wounds with biofilms of antimicrobial-resistant (AMR) bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), and multi-drug resistant Pseudomonas aeruginosa (MDR-PA). Resistance hinders initial treatment of standard-of-care antibiotics. The persistence of MRSA, MRSE, and/or MDR-PA often allows acute infections to become chronic wound infections. The water-soluble hydrophilic properties of low-molecular-weight (600 Da) branched polyethylenimine (600 Da BPEI) enable easy drug delivery to directly attack AMR and biofilms in the wound environment as a topical agent for wound treatment. To mitigate toxicity issues, we have modified 600 Da BPEI with polyethylene glycol (PEG) in a straightforward one-step reaction. The PEG–BPEI molecules disable β-lactam resistance in MRSA, MRSE, and MDR-PA while also having the ability to dissolve established biofilms. PEG-BPEI accomplishes these tasks independently, resulting in a multifunction potentiation agent. We envision wound treatment with antibiotics given topically, orally, or intravenously in which external application of PEG–BPEIs disables biofilms and resistance mechanisms. In the absence of a robust pipeline of new drugs, existing drugs and regimens must be re-evaluated as combination(s) with potentiators. The PEGylation of 600 Da BPEI provides new opportunities to meet this goal with a single compound whose multifunction properties are retained while lowering acute toxicity.

Emergency medical services oxygen equipment: a fomite for transmission of MRSA?

ObjectivesThe primary purpose of this study was to determine if methicillin-resistant Staphylococcus aureus (MRSA) was present on the surface of oxygen cylinders and regulators used in the prehospital setting and...

Methicillin-Resistant Staphylococcus Aureus in Melanesian Children with Haematogenous Osteomyelitis from the Central Highlands of Papua New Guinea

Background: Methicillin-Resistant Staphylococcus aureus (MRSA) has been an important cause of bone infection since the 1940s. Current guidelines recommend targeted antibiotic use for osteomyelitis treatment informed by microbial sensitivity patterns. However, in settings without microbiology facilities, empirical antibiotic use is common. Unrecognized antibiotic resistance potentiates persistence of MRSA with osteomyelitis progression to chronic forms with complications despite antibiotic treatment. Materials and Methods: A prospective observational study was done to identify common etiological agent (s) in bone infection in Melanesian children (that were admitted to the two surgical and one pediatric wards of the SJNM-KUGH in the Simbu province of Papua New Guinea in 2012 and 2017), observe for presence of antimicrobial resistance, and determine effective antibiotic regimes for treatment of bone pediatric osteomyelitis. Seventy pediatric patients presenting from the community with osteomyelitis were recruited, with bone and non-bone specimens sampled, cultured and isolates tested for resistance to common antibiotics. Results: Staphylococcus aureus (S. aureus) was isolated in 67% (47/70) of collected specimens. Of the 47 isolates, there was 91.5% resistance to penicillin, 85.1% resistance to methicillin, 89.4% resistance to oxacillin, 93.6% resistance to ampicillin and 80.9% resistance to ceftriaxone. S. aureus showed 91.5% sensitivity to gentamycin, 93.6% sensitivity to erythromycin, tetracycline and clindamycin, and 95.7% sensitivity to Co-trimoxazole. Conclusion: MRSA was the leading cause of haematogenous osteomyelitis in Melanesian children. S.aureus was isolated mainly from infected long bones of the lower limbs (79%) of children presenting from the community, suggesting a predominantly community-associated MRSA.

Short communication: Occurrence of methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci in dairy goat herds in Ohio, United States

In light of the scarcity of information about the occurrence and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (MRCNS) in small ruminants in general, and particularly dairy goats, we launched this limited-scope study. The findings reported here show the detection of MRSA and MRCNS in goat milk and teat skin samples from dairy goat herds in the state of Ohio. A total of 120 milk samples and 120 teat-swab samples were collected from 5 farms. After conventional isolation and phenotypic characterization of the staphylococci colonies, bacterial isolates were tested by PCR assay targeting the genes nuc to identify Staphylococcus aureus and mecA to detect MRSA and MRCNS. The clonal complexes of MRSA isolates was also determined by multiloccus sequence typing. Fifteen (6.2%) positive S. aureus samples were found in this study: 9 from milk and 6 from teat skin samples. Four (2%) MRSA isolates were detected and, using multiloccus sequence typing genotyping, these were designated to clonal complexes CC133 (n = 2; milk samples) and CC5 (n = 2; teat skin). Three (1.25%) coagulase-negative staphylococci isolates from the teat skin also harbored the mecA gene. Although, the MRSA isolated from milk samples is not a typical human-associated lineage, the CC5 clone isolated from teat skin is a common and widespread clonal complex associated with humans, suggesting that this extramammary niche could be a relevant reservoir of methicillin-resistant staphylococci. Furthermore, the fact that 75% of MRSA were recovered from 1 farm showing poor hygiene practices strengthens the hypothesis that good hygiene practices could be useful to prevent persistence and spread of MRSA at a farm level.

Methicillin-resistant Staphylococcus aureus nasal colonization in a level III neonatal intensive care unit: Incidence and risk factors

To describe epidemiologic features and identify risk factors for methicillin-resistant Staphylococcus aureus (MRSA) acquisition in a level III neonatal intensive care unit (NICU). A prospective, cohort study in a university-affiliated NICU with an infection control program including weekly nasal cultures of all neonates. Demographic, clinical, and microbiologic data were prospectively collected between June 2009 and June 2013. Molecular characterization of MRSA isolates was done by multilocus variable number tandem repeat fingerprinting, staphylococcal cassette chromosome mec typing, and on representative isolates by multilocus sequence typing and spa typing. Of 949 neonates, 217 (22.87%) had a culture growing MRSA, including 117 neonates testing positive at their first sampling. Of these latter infants, 96 (82.05%) were inborn and 59 (50.43%) had been transferred from the nursery. Length of stay and colonization pressure were strong independent predictors of MRSA acquisition. Among MRSA isolates, 7 sequence types were identified, with ST22-IVa, spa type t223, being the predominant strain. In an endemic area, early MRSA acquisition and high colonization pressure, likely related to an influx of colonized infants from a well-infant nursery, can support persistence of MRSA in NICUs. Surveillance, molecular tracking of strains, and reinforcement of infection control practices, involving well-infant nurseries in a comprehensive infection control program, could be helpful in containing MRSA transmission.

Structural and functional characterization of methicillin-resistant Staphylococcus aureus's class IIb fructose 1,6-bisphosphate aldolase.

Staphylococcus aureus is one of the most common nosocomial sources of soft-tissue and skin infections and has more recently become prevalent in the community setting as well. Since the use of penicillins to combat S. aureus infections in the 1940s, the bacterium has been notorious for developing resistances to antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA). With the persistence of MRSA as well as many other drug resistant bacteria and parasites, there is a growing need to focus on new pharmacological targets. Recently, class II fructose 1,6-bisphosphate aldolases (FBAs) have garnered attention to fill this role. Regrettably, scarce biochemical data and no structural data are currently available for the class II FBA found in MRSA (SaFBA). With the recent finding of a flexible active site zinc-binding loop (Z-Loop) in class IIa FBAs and its potential for broad spectrum class II FBA inhibition, the lack of information regarding this feature of class IIb FBAs, such as SaFBA, has been limiting for further Z-loop inhibitor development. Therefore, we elucidated the crystal structure of SaFBA to 2.1 Å allowing for a more direct structural analysis of SaFBA. Furthermore, we determined the KM for one of SaFBA’s substrates, fructose 1,6-bisphosphate, as well as performed mode of inhibition studies for an inhibitor that takes advantage of the Z-loop’s flexibility. Together the data offers insight into a class IIb FBA from a pervasively drug resistant bacterium and a comparison of Z-loops and other features between the different subtypes of class II FBAs.

Zinc Oxide Therapy Increases Prevalence and Persistence of Methicillin‐Resistant Staphylococcus aureus in Pigs: A Randomized Controlled Trial

There is concern that therapeutic use of zinc oxide (ZnO) in swine production may select for methicillin-resistant Staphylococcus aureus (MRSA) due to co-location of the zinc resistance gene (czrC) and methicillin resistance gene (mecA) within the staphylococcal cassette chromosome mec (SCCmec). The objective of this investigation was to determine whether MRSA carriage in pigs is influenced by exposure to therapeutic doses of in-feed ZnO (3000 mg/kg) when compared to the recommended dietary levels (100 mg/kg). A randomized controlled trial was completed using 110 pigs that were naturally colonized with czrC-positive MRSA. The pigs were followed from birth to weaning (21 d), at which point they were randomized into 8 pens and exposed to either a control feed (100 mg ZnO/kg feed; n = 49 pigs) or a treatment feed (3000 mg ZnO/kg feed; n = 50 pigs); neither feed contained additional antimicrobials. MRSA carriage was monitored weekly in each group for 4 weeks post-weaning. The prevalence of MRSA was significantly higher in the treatment group at 1-week (OR = 18.1; P < 0.01) and 2 weeks (OR = 3.01; P = 0.01) post-weaning when compared to the control group, but there was no difference later in the nursery phase. Persistent MRSA carriage (testing positive ≥2 times post-weaning) was observed in 2% (1/49) of control pigs and 22% (11/50) of treated pigs (P < 0.01). All MRSA isolates (spa types t034 and t3075) carried czrC and showed uniform resistance to zinc. These findings demonstrate that the prevalence and persistence of MRSA in nursery pigs can be affected by high levels of in-feed ZnO in the absence of antibiotics.

Methicillin-ResistantStaphylococcus aureus

Despite the availability of effective preventative and therapeutic strategies, methicillin-resistant Staphylococcus aureus (MRSA) remains amajor cause of health care–associated and, more recently, community-acquired infections. Since the introduction of methicillin in 1959, epidemics due to different clones ofMRSAhave occurred in diverse geographic regions.1 The result has been the persistence of MRSA as an important pathogen worldwide. In the United States, themost recentMRSA epidemic has been due to the clone USA300. USA300 has been responsible for themajorityof communityandhealth care–associatedoutbreaks since the early 1990s.1 Until recently, thenumber of infections has continued to rise, especially in urban centers. While themajority of these have been skin and soft-tissue infections (SSTIs), a notable minority have been invasive and life-threatening.1 Two articles in this issueof JAMAInternalMedicineprovide additional insight into both the incidence and the risks associatedwithdevelopmentofMRSA infections.Danteset al2provide evidence that the overall incidence of invasiveMRSA infections nationally is declining. Casey et al3 perform an ecological investigation; they find that individuals livingnear high-density farming operations (ie, farms having an animal density of 2 animals or 1000-lbs live weight per acre) or near crop fieldsusingmanure exported from thehigh-density livestock farms are at increased risk of developingMRSA or other bacterial SSTIs. Both studies raise questions thatwarrant further investigation. Dantes et al2 useddata from theActiveBacterial Core Surveillance Program (ABCSP) to compare the national incidence rate of invasive MRSA infections for the years 2005 through 2011. The findings are of special importance because of the surveymethods that areusedand the size of the sample population (approximately 15 million). The ABCSP is an active surveillance program that is population based and includes a reviewofmedical records. It serves as amodel for this type of surveillance. The results show that the incidence of health care–associated community-onset and hospital-onset invasive MRSA infections have declined by 27.7% and 54.2%, respectively. The findings are consistent with several earlier reports including one from the same group. This impressive declinemaywellbeduetothe implementationof infectioncontrol efforts at thehospital level; however, it is alsopossible that the epidemic MRSA strains circulating in the health care setting have evolved, becoming less virulent. In contrast to the decline inhealth care–associatedMRSA, the estimated reduction in incidence of community-associated infections was a modest 5%. In addition to the evidence that the incidenceofMRSA infections is declining, the study highlights 2 important points. The first is the observation that there is an increased risk of recurrent infection among recentlyhospitalizedpatientswith healthcare–associatedcommunity-onset infections.Thesepatients had a 64% risk of infection at 3 months or less followingdischarge.Others have also reported ahigh risk of reinfection in discharged patients either infected or colonized with MRSA.4 Possible explanations for the patients’ increased risk include underlyingmedical comorbidities, persistent colonizationor recolonizationwithMRSA,orexposure tosimilar risks of MRSA infection following discharge. This subset of patients would appear to be candidates for studies directed at reducing their high risk of recurrent infection. The second finding is the limited change in the incidence of communityassociated infections. This is in marked contrast with the reduction in the incidence of health care–associated infections. As noted by the authors, the study highlights the need for a greater understanding of how these epidemic MRSA strains spread and initiate infection within the community. Related articles pages 1970 and 1980 Research Original Investigation National Burden of Invasive MRSA Infections

Transmission and Persistence of Methicillin-ResistantStaphylococcus aureusin Milk, Environment, and Workers in Dairy Cattle Farms

The aim of this study was to determine the presence and persistence of methicillin-resistant Staphylococcus aureus (MRSA) in milk, farm environment, and farmers on 22 dairy cattle farms in Korea during 2008-2009. Genetic relatedness among the MRSA isolates was also investigated. Of 1146 samples examined, 35 of 559 (6.3%) quarter milk samples from 371 cows, four of 86 (4.7%) hand and nose samples from 43 farmers, and 6 of 501 (1.2%) farm environment samples were MRSA positive. Except for three isolates, all MRSA were classified into ST72-spa t324-SCCmec IV with PVL negative, the most predominant clonal type among community-associated MRSA in South Korea. All 35 MRSA-positive milk samples from 19 cows were obtained from a single farm (Farm G) out of 22 (4.5%) farms tested. The farm G was revisited 1 year later and milk samples were collected for examination of MRSA again. Two of six previous MRSA-positive cattle that had been kept on the farm still harbored MRSA genetically identical to MRSA strains, which were isolated from the same farm a year ago. The results of this study provide the evidence of transmission of MRSA among cattle, farm environment, and farmers and also long-term persistence of MRSA in animals.

Modeling the Spread of Methicillin-Resistant Staphylococcus aureus in Nursing Homes for Elderly

Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in many hospital settings, including nursing homes. It is an important nosocomial pathogen that causes mortality and an economic burden to patients, hospitals, and the community. The epidemiology of the bacteria in nursing homes is both hospital- and community-like. Transmission occurs via hands of health care workers (HCWs) and direct contacts among residents during social activities. In this work, mathematical modeling in both deterministic and stochastic frameworks is used to study dissemination of MRSA among residents and HCWs, persistence and prevalence of MRSA in a population, and possible means of controlling the spread of this pathogen in nursing homes. The model predicts that: without strict screening and decolonization of colonized individuals at admission, MRSA may persist; decolonization of colonized residents, improving hand hygiene in both residents and HCWs, reducing the duration of contamination of HCWs, and decreasing the resident∶staff ratio are possible control strategies; the mean time that a resident remains susceptible since admission may be prolonged by screening and decolonization treatment in colonized individuals; in the stochastic framework, the total number of colonized residents varies and may increase when the admission of colonized residents, the duration of colonization, the average number of contacts among residents, or the average number of contacts that each resident requires from HCWs increases; an introduction of a colonized individual into an MRSA-free nursing home has a much higher probability of leading to a major outbreak taking off than an introduction of a contaminated HCW.

P11.01 Resistance of Acanthamoeba spp. cysts to disinfection treatments

P11.01 Resistance of Acanthamoeba spp. cysts to disinfection treatments

Long-term persistence of MRSA in re-admitted patients

BackgroundA better knowledge of methicillin-resistant Staphylococcus aureus (MRSA) persistence in hospitalised patients may impact on specific prevention strategies. We have investigated the persistence of MRSA-carriage in patients admitted and re-admitted to a university hospital.Patients and methodsBetween January 2002 and October 2005 all MRSA-positive patients admitted to the university hospital of Hannover Medical School were assessed at first admission and all subsequent re-admissions. Patients re-admitted at least once were analysed for the persistence or loss of MRSA. The association of possible factors influencing the persistence of MRSA colonisation or infection (age group, gender, decolonisation therapy during first hospital stay due to MRSA positivity and colonisation of different anatomical sites) was analysed using univariate, multivariate and time-dependent analyses.ResultsA total of 1,032 patients who had tested positive at least once for MRSA were admitted to our hospital during the study period, accounting for 2,038 admissions. Of these patients, 403 (39.1%) were admitted more than once (from two times to 21 times), and 238 (59.1%) of the re-admitted patients remained MRSA positive during all subsequent admissions. Fifty-five (13.6%) patients tested MRSA negative at their last admission, and 61 (15.1%) tested MRSA negative at at least two consecutive admissions. In 27 (6.7%) patients, the MRSA status differed more than once between subsequent admissions. Overall, the half-life time (HLT) of MRSA persistence was 549 days, with the duration of persistence dependent on the colonisation of different anatomical sites (HLT only wounds 117 days; HLT mouth, throat, bronchial secretions 627 days; HLT nose, wounds and other body sites 801 days; p < 0.01) and was prolonged if more than one body site was MRSA-positive (HR 2.18, 95% confidence interval 1.52–3.15).ConclusionA detailed knowledge of the dynamics of the loss of MRSA infection could result in a reduction of the incidence of MRSA in the future. Multiple anatomical site carriage of MRSA appeared to predict a prolonged persistence in our cohort of patients re-admitted to a university hospital.

RISK FACTORS AND ASSOCIATED PROBLEMS IN THE MANAGEMENT OF INFECTIONS WITH METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS

Purpose: It is necessary to define the problem of methicillin resistant Staphylococcus aureus (MRSA) in every hospital to evolve control strategies. The objectives of this study were to determine factors influencing the persistence of MRSA in patients with hospital acquired infection and to identify alternate cost effective antibiotics. Methods: A six month study was carried out for 50 patients with MRSA infection. Treatment modalities and risk factors were determined by a preset protocol. Minimum inhibitory concentration of commonly used antibiotics was determined. Results: The risk factors were prolonged postoperative morbidity, prior antibiotic therapy and emergency admissions. Seventy percent of the isolates were from postoperative cases undergoing emergency surgeries. Isolation was highest during the second week of hospital stay. Emergency admissions had a significantly higher chance of early isolation. Prior treatment with multiple antibiotics in 38% was found to be another major risk factor. Ofloxacin was seen to be efficacious in a small percentage of cases. Rifampicin in combination with ofloxacin and clindamycin were found to be other good alternatives. Ofloxacin was found to be the cheapest and vancomycin the most expensive, for a full course of treatment. Conclusions: Minimizing risk factors and attention to alternate cost effective combination therapy may ease the problem of management of infections with MRSA.

Surgimiento y diseminación de Staphylococcus aureus meticilinorresistente

Nosocomial infections due to methicillin-resistant Staphylococcus aureus (MRSA) is an important health problem worldwide. This microorganism causes a variety of clinical infections, including osteomyelitis, invasive endocarditis, septic arthritis and septicemia. Antimicrobial resistance is a factor that influences the persistence of MRSA in the hospital environment. The introduction of molecular typing techniques in epidemiological investigations has provided new tools for identifying the microorganism's origin and routes of dissemination. One of the most important conclusions that have resulted from these types of studies is that a small number of clones are responsible for most of the staphylococcal infections throughout the world.

Transregional Spread of a Single Clone of Methicillin–Resistant Staphylococcus aureus between Groups of Drug Users in Switzerland

An epidemic spread of methicillin-resistant Staphylococcus aureus (MRSA) among intravenous drug users (IDUs) has been observed in Zurich. In the present study we investigated the situation in the Grisons, Switzerland. We screened IDUs and their caregivers in medical and socio-therapeutical institutions in the Grisons for MRSA. Nose swabs were used for bacterial culture and pulsed-field gel electrophoresis for MRSA genotyping. A total of 191 nose swabs from 111 IDUs and 80 caregivers was analyzed. None of the caregivers was MRSA positive. Six IDUs were asymptomatic MRSA carriers (5.4%). They participated in the official heroin program (MRSA prevalence in this group 16%). The MRSA genotype was identical with the single clone found in IDUs in Zurich, strongly suggesting an epidemic spread. Decolonization was successful in two persons only. Persistence of MRSA in IDUs must therefore be assumed. We conclude that a single clone of MRSA, found in IDUs in Zurich, has spread to a distant region of Switzerland. A rigorous infection control program in all institutions with IDUs is necessary to prevent a further spread of MRSA.