Prevalence and acquisition of MRSA amongst patients admitted to a tertiary-care hospital in Brazil

Methicillin-resistant Staphylococcus spp. investigation in hospitalized horses and contacting personnel in a teaching veterinary hospital

Staphylococci are well-known opportunistic pathogens associated with suppurative diseases in humans and animals. Antimicrobial resistance is an emergent threat to humans and animals worldwide. This study investigated the prevalence of methicillin-resistant Staphylococcus spp. (MRS) in hospitalized horses and contacting personnel (veterinarians and staff), and assessed possible interspecies transmission in a teaching veterinary hospital. Nasal swabs from horses (n = 131) and humans (n = 35) were collected. The microorganisms were identified by traditional biochemical tests and genotypic methods, i.e., PCR, internal transcript spacer PCR (ITS-PCR), and gene sequencing. Staphylococcal species were isolated in 18% (23/131) of the horses, of which 8% (11/131) were S. hyicus, 4 % (5/131) were S. aureus, 4% (5/131) were S. pseudintermedius, and 2% (2/131) were S. schleiferi subsp. coagulans. The mecA gene was detected in an S. pseudintermedius isolate. Staphylococcus spp. was isolated in 40% (14/35) of the human samples, all of which were S. aureus. In four samples of S. aureus, the clonal profile ST398 was identified; among them, a clonal similarity of 98.1% was observed between a horse and a contacting human. This finding supports the need for biosecurity measures to avoid the spread of multidrug-resistant staphylococci in humans and horses.

Ward-level factors associated with methicillin-resistant Staphylococcus aureus acquisition-an electronic medical records study in Singapore

Background

Methicillin-Resistant Staphylococcus aureus (MRSA) is endemic in hospitals worldwide. Intrahospital transfers may impact MRSA acquisition risk experienced by patients. In this study, we investigated ward characteristics and connectivity that are associated with MRSA acquisition.

Methods

We analysed electronic medical records on patient transfers and MRSA screening of in-patients at an acute-care tertiary hospital in Singapore to investigate whether ward characteristics and connectivity within a network of in-patient wards were associated with MRSA acquisition rates over a period of four years.

Results

Most patient transfers concentrated in a stable core network of wards. Factors associated with increased rate of MRSA acquisition were MRSA prevalence among patients transferred from other wards (rate ratio (RR): 7.74 [95% confidence interval (CI): 3.88, 15.44], additional 5 percentage point), critical care ward (RR: 1.72 [95% CI: 1.09, 2.70]) and presence of MRSA cohorting beds (RR: 1.39 [95% CI: 1.03, 1.90]. Oncology ward (RR: 0.66 [95% CI: 0.46, 0.94]) (compared to medical ward), and median length of stay (RR: 0.70 [95% CI: 0.55, 0.90], additional 1.5 days) were associated with lower acquisition rates. In addition, we found evidence of interaction between MRSA prevalence among patients transferred from other wards and weighted in-degree although the latter was not associated with MRSA acquisition after controlling for confounders.

Conclusion

Wards with higher MRSA prevalence among patients transferred from other wards were more likely to have higher MRSA acquisition rate. Its effect further increased in wards receiving greater number of patients. In addition, critical care ward, presence of MRSA cohorting beds, ward specialty, and median length of stay were associated with MRSA acquisition.

Prevalence and Associated Factors of Methicillin Resistance Staphylococcus aureus (MRSA) Among Urinary Tract Infection Suspected Patients Attending at Arba Minch General Hospital, Southern Ethiopia

BACKGROUND

Urinary tract infection (UTI) is a very frequent infection both in the community and hospital patients, and the emergence of methicillin-resistant Staphylococcus aureus (MRSA) in the community setting and infections with this pathogen become a prevalent problem among UTI patients. Therefore, the aim of this study was to determine prevalence and associated factors of methicillin resistance staphylococcus aureus (MRSA) among urinary tract infection suspected patients attending at Arba Minch General Hospital.

METHODS

Facility-based cross-sectional study was done at Arba Minch General Hospital from July to October 2020. Midstream urine specimen was collected from outpatients, cultured and biochemical tests were performed to identify the intended pathogen, finally the antibiotic susceptibility pattern of MRSA was done and possible associated factors were determined. The cleaned data were entered and analyzed using SPSS version 21.

RESULTS

Four hundred and twenty two (422) adult outpatients were enrolled in this study, of which males accounted for 238 (56.4%) of the participants. The mean and standard deviation age of the participants was 27.4 (SD 27.4 ± 15.6) years. A total of 54 S. aureus isolates were recovered from urine specimen. The prevalence of MRSA among the isolated S. aureus was 23/54 (42.59% (95% CI (35.0, 47.0)). Participants who had previous exposure to UTI (p < 0.002), presence of chronic disease (p < 0.029), and hospitalization (p < 0.006) were statically associated with the prevalence of MRSA. From all the MRSA isolates, 53.7% were resistant against Nitrofurantoin.

CONCLUSION

This study revealed that MRSA could be prevalent in isolates from patients suspected of urinary tract infection and exhibiting different resistance pattern for antibiotics commonly used for treatment of staphylococcal infections.

Prevalence and antimicrobial resistance profile of Staphylococcus aureus in inherited epidermolysis bullosa: a cross-sectional multicenter study in Brazil

BACKGROUND

Infection is an important complication of epidermolysis bullosa (EB), and Staphylococcus aureus has been pointed out as the most common pathogen among this population. The objective of this study was to investigate the prevalence and antimicrobial resistance profile of S. aureus colonizing EB patients in Brazil.

METHODS

This cross-sectional multicenter study was conducted between December 2015 and December 2017. We included a total of 89 individuals with EB from medical centers across Brazil. Data were obtained through clinical and bacteriological investigation. S. aureus were identified by biochemical tests. The nuc and mecA genes were confirmed by PCR assay. Antimicrobial susceptibility was investigated by disk diffusion method.

RESULTS

The overall prevalence of S. aureus was 51.7% (46/89). Methicillin-resistant S. aureus (MRSA) was detected in 24.7% (19/77) of all S. aureus isolates, colonizing 15.7% (14/89) of all patients. Community-associated (CA)-MRSA strains were resistant against sulfamethoxazole/trimethoprim and levofloxacin (P < 0.05%). S. aureus colonization of the nares and belly button represented a 3.4 times higher risk of simultaneous skin lesion colonization (P < 0.05%).

CONCLUSIONS

The high frequency of MRSA colonizing patients with EB is alarming considering its association with life-threatening complications and poorer outcomes. EB patients are at increased risk of colonization and infection by Staphylococcus aureus and CA-MRSA. Getting to know S. aureus carriage sites and its antimicrobial susceptibility profile is key when planning new individualized and more effective prophylactic and therapeutic measures.

The History of Methicillin-Resistant Staphylococcus aureus in Brazil

Since the emergence of MRSA in the 1960s, a gradual increase in infections by resistant bacteria has been observed. Clinical manifestations may vary from brand to critical condition due to host risk factors, as well as pathogen virulence and resistance. The high adaptability and pathogenic profile of MRSA clones contributed to its spread in hospital and community settings. In Brazil, the first MRSA isolates were reported in the late 1980s, and since then different genetic profiles, such as the Brazilian epidemic clone (BEC) and other clones considered a pandemic, became endemic in the Brazilian population. Additionally, Brazil's MRSA clones were shown to be able to transfer genes involved in multidrug resistance and enhanced pathogenic properties. These events contributed to the rise of highly resistant and pathogenic MRSA. In this review, we present the main events which compose the history of MRSA in Brazil, including numbers and locations of isolation, as well as types of staphylococcal cassette chromosome mec (SCCmec) found in the Brazilian territory.

Genotypic distribution of Staphylococcus aureus colonizing children and adolescents in daycare centers, an outpatient clinic, and hospitals in a major Brazilian urban setting

Staphylococcus aureus nasal colonization is a major risk factor for infection. Studies have suggested an epidemiologic shift in the methicillin-resistant S. aureus (MRSA) strains that circulate in Brazil. We conducted cross-sectional studies of MRSA carriage among 1) children and adolescents in community daycare centers, 2) an outpatient clinic, and 3) hospitals in a large Brazilian metropolitan setting. There were 1.500 study subjects, 500 from each locale: 768 (51.2%) carried S. aureus whereas 150 (10%) of these were colonized with MRSA. The most common lineages were the Southwest Pacific (SWP) and the Pediatric clones in all three groups. Roughly 50% of SWP carried Panton-Valentine leukocidin (PVL) (p < 0.01) genes while 63.3% of the Pediatric clones were resistant or intermediately resistant to erythromycin (p < 0.01). This study describes a clonal change of the Brazilian epidemic clone (BEC) to the Pediatric and SWP lineages in Brazil. This finding has implications for clinical management of MRSA infections.

Phenotypic and Molecular Screening of Nasal S. aureus from Adult Hospitalized Patients for Methicillin- and Vancomycin-resistance

INTRODUCTION

Nasal carriers of Staphylococcus aureus are common and play an important role in the transmission of infections. The aim of this study is a phenotypic and molecular investigation of nasal methicillin- and vancomycin-resistant S. aureus in hospitalized patients.

METHODS

202 nasal swabs were collected from patients at Prince Hamzah Hospital, Jordan, through 2016-2017. Swabs were processed according to standard microbiological procedures to isolate Staphylococci. Antibiotic susceptibility testing was performed using disk diffusion, E-test, microdilution and Vitek 2. Methicillin resistance was confirmed by testing for the mecA gene, while vancomycin resistance was screened by testing for the vanA and vanB genes.

RESULTS

The mean age of participants was 50.17±18.18 years and 59.4% were females. Nasal Staphylococci was isolated in 64/202 (31.7%), S. aureus was isolated from 33 samples (16.3%), MRSA was isolated from 13 samples (6.4%) and constitutive Macrolide-lincosamidestreptogramin B (MLSB) was isolated from 12 samples (5.9%). All MRSA isolates harbored the mecA gene. All isolates were sensitive to vancomycin using E-test and the microdilution test and were negative for the vanA and vanB genes. The highest resistance rate was observed for benzylpenicillin (>90%), while the lowest resistance rate was for tobramycin (<5%) among all isolates. Nasal Staphylococci, S. aureus and MRSA colonization significantly correlate with increased number of family members and previous hospitalization (P<0.05), while nasal S. aureus significantly correlates with a history of skin infection (P=0.003).

CONCLUSION

Nasal colonization by mecA-mediated MRSA is common among hospitalized patients, while vanA- and vanB-mediated vancomycin resistance was not detected in any nasal isolates.

Reducing transmission of methicillin-resistant Staphylococcus aureus in a surgical ward of a resource-limited hospital in Indonesia: an intervention study

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in healthcare settings in Indonesia.

Aim

To evaluate the effect of a bundle of preventive measures on the transmission and acquisition of MRSA in a surgical ward of a resource-limited hospital in Indonesia.

Methods

The study consisted of a pre-intervention (7 months), intervention (2 months), and post-intervention phase (5 months) and included screening for MRSA among eligible patients, healthcare workers (HCWs), and the hospital environment. In the intervention phase, a bundle of preventive actions was introduced, comprising: a hand hygiene educational program, cohorting of MRSA-positive patients, decolonization therapy for all MRSA-positive patients and HCWs, and cleaning and disinfection of the ward's innate environment. Hand hygiene compliance was assessed throughout the study period. The primary outcome was the acquisition rate of MRSA among patients per 1,000 patient-days at risk. Clonality of MRSA isolates was determined by Raman spectroscopy and multilocus sequence typing.

Findings

In total, 1,120 patients were included. Hand hygiene compliance rate rose from 15% pre-intervention to 65% post-intervention (P<0.001). The MRSA acquisition decreased from 9/1,000 patient-days at risk pre-intervention to 3/1,000 patient-days at risk post-intervention, but this difference did not reach statistical significance (P=0.08). Raman type 9 which belonged to ST239 was the single dominant MRSA clone.

Conclusion

The introduction of a bundle of preventive measures may reduce MRSA transmission and acquisition among surgery patients in a resource-limited hospital in Indonesia, but additional efforts are needed.

Early switch/early discharge opportunities for hospitalized patients with methicillin-resistant Staphylococcus aureus complicated skin and soft tissue infections in Brazil

BACKGROUND

Early antibiotic switch and early discharge protocols have not been widely studied in Latin America. Our objective was to describe real-world treatment patterns, resource use, and estimate opportunities for early switch from intravenous to oral antibiotics and early discharge for patients hospitalized with methicillin-resistant Staphylococcus aureus complicated skin and soft-tissue infections.

MATERIALS/METHODS

This retrospective medical chart review recruited 72 physicians from Brazil to collect data from patients hospitalized with documented methicillin-resistant Staphylococcus aureus complicated skin and soft tissue infections between May 2013 and May 2015, and discharged alive by June 2015. Data collected included clinical characteristics and outcomes, hospital length of stay, methicillin-resistant Staphylococcus aureus-targeted intravenous and oral antibiotic use, and early switch and early discharge eligibility using literature-based and expert-validated criteria.

RESULTS

A total of 199 patient charts were reviewed, of which 196 (98.5%) were prescribed methicillin-resistant Staphylococcus aureus -active therapy. Only four patients were switched from intravenous to oral antibiotics while hospitalized. The mean length of methicillin-resistant Staphylococcus aureus-active treatment was 14.7 (standard deviation, 10.1) days, with 14.6 (standard deviation, 10.1) total days of intravenous therapy. The mean length of hospital stay was 22.2 (standard deviation, 23.0) days. The most frequent initial methicillin-resistant Staphylococcus aureus-active therapies were intravenous vancomycin (58.2%), intravenous clindamycin (19.9%), and intravenous daptomycin (6.6%). Thirty-one patients (15.6%) were discharged with methicillin-resistant Staphylococcus aureus -active antibiotics of which 80.6% received oral antibiotics. Sixty-two patients (31.2%) met early switch criteria and potentially could have discontinued intravenous therapy 6.8 (standard deviation, 7.8) days sooner, and 65 patients (32.7%) met early discharge criteria and potentially could have been discharged 5.3 (standard deviation, 7.0) days sooner.

CONCLUSIONS

Only 2% of patients were switched from intravenous to oral antibiotics in our study while almost one-third were early switch eligible. Additionally, one-third of hospitalized patients with methicillin-resistant Staphylococcus aureus complicated skin and soft tissue infections were early discharge eligible indicating opportunity for reducing intravenous therapy and days of hospital stay. These results provide insight into possible benefits of implementation of early switch/early discharge protocols in Brazil.

Prevalence of nasal carriage of methicillin-resistant Staphylococcus aureus in patients at hospital admission in The Netherlands, 2010-2017: an observational study

OBJECTIVES

We determined the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage upon hospital admission, among patients who were screened preoperatively for nasal S. aureus carriage between 2010 and 2017. We also aimed to evaluate the prevalence of MRSA carriers without the standard risk factors.

METHODS

We conducted an observational study to determine the prevalence of MRSA nasal carriage among patients who were screened preoperatively for nasal S. aureus carriage between 2010 and 2017. Samples of cardiothoracic patients were tested by polymerase chain reaction (PCR), other samples were cultured using chromogenic agar plates. A Poisson regression model with robust error variance was used to assess whether there was a trend in the prevalence of MRSA over time.

RESULTS

In total, 31 093 nasal swabs were obtained from 25 660 patients. Three-hundred and seventy-five swabs (1.2%) had an invalid result. Therefore, 30 718 swabs (98.8%) were included in our analysis. Overall, S. aureus was detected in 7981/30 718 patients (26.0% 95% CI 25.5-26.5%) of whom 41 were MRSA (0.13% 95% CI 0.10-0.18%). The MRSA prevalence varied from 0.03% to 0.17% over the years without evidence of a changing trend over time (p = 0.40). Results of the questionnaire revealed that 30 of the 41 patients (73.2%) had no known risk factors for MRSA carriage (0.10%; 95% CI 0.07-0.14%).

CONCLUSION

Our study revealed a sustained low prevalence of MRSA carriage upon hospital admission over 7 years. This supports the effectiveness of the Dutch Search and Destroy policy, in combination with a restrictive antibiotic prescription policy.

Characteristics of methicillin-resistant Staphylococcus aureus in patients on admission to a teaching hospital in Rio de Janeiro, Brazil

BACKGROUND

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are associated with greater mortality and morbidity; however, risk factors for community-acquired infections caused by MRSA have not been established. Therefore, community patients who are admitted to hospitals without the necessary contact precautions and are infected with community-acquired lineages eventually cause these lineages to spread to these settings. The aim of this study was to detect community-acquired lineages of MRSA in patients on admission to a Brazilian teaching hospital.

METHODS

The antimicrobial susceptibility of the MRSA isolates from nasal swabs was evaluated as was the molecular characteristics of the staphylococcal cassette chromosome mec (SCCmec). The clonality was determined using pulsed-field gel electrophoresis and multilocus sequence type analysis.

RESULTS

A total of 702 patients were evaluated between March 2012 and March 2013; 180 (25%) of them were colonized by S aureus, and 21 (3%) were MRSA. The SCCmec IV/USA1100/sequence type (ST) 30 was the predominant MRSA lineage (42.8%), followed by SCCmec IV/USA800/ST5 (23.8%).

CONCLUSIONS

The occurrence of MRSA colonization was very low, and only 1 patient from cardiac surgery developed an infection, which was caused by an SCCmec II/USA100/ST5 isolate. Screening for MRSA colonization on admission does not seem to be productive; however, for populations submitted to specific surgeries, active surveillance should be implemented.

Prevalence of methicillin-resistant Staphylococcus aureus carriage on admission among patients attending regional hospitals in Dar es Salaam, Tanzania

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for hospital and community acquired infection. Colonization with MRSA is associated with a high risk of developing infection. This study aimed to determine the rate of MRSA carriage on admission and the associated risk factors among patients attending regional hospitals, in Dar es Salaam, Tanzania.

Results

A total of 258 patients were included in this study. Nasal swabs were collected on admission to the hospital and after 48 h of hospital stay for detection of MRSA. Of 258 patients enrolled, 89 (34.5%) were colonized with S. aureus and out them 22 (24.7%) were carriers of MRSA, giving an overall MRSA nasal carriage rate of 8.5% (22/258). One patient acquired MRSA while admitted in the hospital. Most of the S. aureus isolates 85 (95.5%) were resistant to penicillin. Resistance to gentamycin, ciprofloxacin, kanamycin, linezolid and mupirocin were 14.6, 11.2, 11.2, 3.4 and 1.1%, respectively. The prevalence of inducible clindamycin resistance, constitutive clindamycin resistance, MS phenotype (resistance to erythromycin alone), and multidrug resistance was 21.3, 3.4, 12.4, and 16.9%, respectively. We observed a statistically significant association between MRSA and multiple drugs resistance among S. aureus isolates (p = 0.001). Of the risk factors investigated none were statistically significant associated with MRSA.

Conclusion

There is a high prevalence of MRSA among patients on admission at the two municipal hospitals in Dar es Salaam. The high prevalence of MRSA and the increased rates of resistance to commonly used antimicrobials among MRSA isolates call for attention to the importance of including the screening of MRSA in our hospitals setting in order to prevent further spread of MRSA strains to other patients and to the communities. Control and prevention strategies should be emphasized including decolonization.

Representações sociais da infecção comunitária por profissionais da atenção primária

Resumo Objetivo Apreender as representações sociais elaboradas pelos profissionais da Atenção Primária sobre infecção comunitária e analisar como tais representações influenciam no controle da infecção e na qualidade da assistência. Métodos Pesquisa exploratória, qualitativa, realizada com 16 profissionais da saúde, selecionados por amostragem simples. Para coleta dos dados, utilizou-se formulário semiestruturado. Os dados foram processados e analisados pela Classificação Hierárquica Descendente. Resultados Foram obtidas quatro classes: Atenção Primária em saúde na gestão das infecções comunitárias; O papel da educação em saúde na prevenção e no controle das infecções; O conceito de infecção comunitária e fatores de risco; Medidas de prevenção e controle das infecções comunitárias. Conclusão As representações sociais sobre a infecção comunitária se organizam a partir da prática profissional, na qual os participantes reconhecem as dificuldades em conceituar o termo, elencar fatores de riscos e medidas de prevenção e controle, refletindo na qualidade da assistência prestada.

Detection and preliminary physico-chemical properties of antimicrobial components in the native excretions/secretions of three species of Chrysomya (Diptera, Calliphoridae) in Brazil

Antibiotic-resistant bacteria in hospitals and communities increasingly threaten public health in Brazil and the rest of the World. There is an urgent need for additional antimicrobial drugs. Calliphorid blowfly larvae are a rich source of antimicrobial factors but the potential of Neotropical species has been neglected. This preliminary study evaluates the antimicrobial activity of the native excretions/secretions of larvae of three species of Brazilian calliphorids, Chrysomya megacephala, Chrysomya albiceps and Chrysomya putoria. Native excretions/secretions were collected from third instar larvae, sterile filtered and tested for antibacterial activity against Staphylococcus aureus 9518, Escherichia coli K12 4401 and Serratia marcescens 365. Turbidometric assays were made in micro-plates, using an ELISA reader, with readings taken up to 22 h. Bacterial suspensions at the start and end of each experiment were also serially diluted, spread on nutrient agar plates and then colony forming units counted. The physico-chemical characteristics of the native excretions/secretions were also tested by freezing/thawing, boiling, and protease digestion. The native excretions/secretions of larvae from these three Chrysomya species significantly inhibited bacterial growth. Therefore, Brazilian calliphorid flies could potentially provide new classes of antibiotics.

The occurrence and dissemination of methicillin and vancomycin-resistant Staphylococcus in samples from patients and health professionals of a university hospital in Recife, State of Pernambuco, Brazil

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) strains have been responsible for many nosocomial outbreaks. Within hospitals, colonized employees often act as reservoirs for the spread of this organism. This study collected clinical samples of 91 patients admitted to the intensive care unit (ICU), hemodialysis/nephrology service and surgical clinic, and biological samples from the nasal cavities of 120 professionals working in those environments, of a University Hospital in Recife, in the State of Pernambuco, Brazil. The main objective of this study was to determine the occurrence and dissemination of methicillin- and vancomycin-resistant Staphylococcus spp.

METHODS

The isolates obtained were tested for susceptibility to oxacillin and vancomycin and detection of the mecA gene. In addition, the isolates were evaluated for the presence of clones by ribotyping-polymerase chain reaction (PCR).

RESULTS

MRSA occurrence, as detected by the presence of the mecA gene, was more prevalent among nursing technicians; 48.1% (13/27) and 40.7% (11/27) of the isolates were from health professionals of the surgical clinic. In patients, the most frequent occurrence of mecA-positive isolates was among the samples from catheter tips (33.3%; 3/9), obtained mostly from the hemodialysis/nephrology service. Eight vancomycin-resistant strains were found among the MRSA isolates through vancomycin screening. Based on the amplification patterns, 17 ribotypes were identified, with some distributed between patients and professionals.

CONCLUSIONS

Despite the great diversity of clones, which makes it difficult to trace the source of the infection, knowledge of the molecular and phenotypic profiles of Staphylococcus samples can contribute towards guiding therapeutic approaches in the treatment and control of nosocomial infections.

Patient-level factors associated with methicillin-resistant Staphylococcus aureus carriage at hospital admission: a systematic review

BACKGROUND

Selective methicillin-resistant Staphylococcus aureus (MRSA) screening programs target high-risk populations. To characterize high-risk populations, we conducted this systematic review to identify patient-level factors associated with MRSA carriage at hospital admission.

METHODS

Studies were identified in the MEDLINE (1950-2011) and EMBASE (1980-2011) databases. English studies were included if they examined adult populations and used multivariable analyses to examine patient-level factors associated with MRSA carriage at hospital admission. From each study, we abstracted details of the population, the risk factors examined, and the association between the risk factors and MRSA carriage at hospital admission.

RESULTS

Our electronic search identified 972 citations, from which we selected 27 studies meeting our inclusion criteria. The patient populations varied across the studies. Ten studies included all patients admitted to hospital, and the others were limited to specific hospital areas. MRSA detection methods also varied across studies. Ten studies obtained specimens from the nares only, whereas other studies also swabbed wounds, catheter sites, and the perianal region. Methods of MRSA diagnoses included polymerase chain reaction tests, cultures in various agar mediums, and latex agglutination tests. Patient age, gender, previous admission to hospital, and previous antibiotic use were the risk factors most commonly examined. The risk factor definition and study methods varied among studies to an extent that precluded meta-analysis.

CONCLUSION

The existing literature cannot be used to identify risk factors for MRSA colonization at the time of hospitalization. Future studies should be aware of the differences in the existing literature and aim to develop standardized risk factor definitions.

Prevalence dependent calibration of a predictive model for nasal carriage of methicillin-resistant Staphylococcus aureus

BACKGROUND

Published models predicting nasal colonization with Methicillin-resistant Staphylococcus aureus among hospital admissions predominantly focus on separation of carriers from non-carriers and are frequently evaluated using measures of discrimination. In contrast, accurate estimation of carriage probability, which may inform decisions regarding treatment and infection control, is rarely assessed. Furthermore, no published models adjust for MRSA prevalence.

METHODS

Using logistic regression, a scoring system (values from 0 to 200) predicting nasal carriage of MRSA was created using a derivation cohort of 3091 individuals admitted to a European tertiary referral center between July 2007 and March 2008. The expected positive predictive value of a rapid diagnostic test (GeneOhm, Becton & Dickinson Co.) was modeled using non-linear regression according to score. Models were validated on a second cohort from the same hospital consisting of 2043 patients admitted between August 2008 and January 2012. Our suggested correction score for prevalence was proportional to the log-transformed odds ratio between cohorts. Calibration before and after correction, i.e. accurate classification into arbitrary strata, was assessed with the Hosmer-Lemeshow-Test.

RESULTS

Treating culture as reference, the rapid diagnostic test had positive predictive values of 64.8% and 54.0% in derivation and internal validation corhorts with prevalences of 2.3% and 1.7%, respectively. In addition to low prevalence, low positive predictive values were due to high proportion (> 66%) of mecA-negative Staphylococcus aureus among false positive results. Age, nursing home residence, admission through the medical emergency department, and ICD-10-GM admission diagnoses starting with "A" or "J" were associated with MRSA carriage and were thus included in the scoring system, which showed good calibration in predicting probability of carriage and the rapid diagnostic test's expected positive predictive value. Calibration for both probability of carriage and expected positive predictive value in the internal validation cohort was improved by applying the correction score.

CONCLUSIONS

Given a set of patient parameters, the presented models accurately predict a) probability of nasal carriage of MRSA and b) a rapid diagnostic test's expected positive predictive value. While the former can inform decisions regarding empiric antibiotic treatment and infection control, the latter can influence choice of screening method.

Cost and effects of different admission screening strategies to control the spread of methicillin-resistant Staphylococcus aureus

Nosocomial infection rates due to antibiotic-resistant bacteriae, e.g., methicillin-resistant Staphylococcus aureus (MRSA) remain high in most countries. Screening for MRSA carriage followed by barrier precautions for documented carriers (so-called screen and isolate (S&I)) has been successful in some, but not all settings. Moreover, different strategies have been proposed, but comparative studies determining their relative effects and costs are not available. We, therefore, used a mathematical model to evaluate the effect and costs of different S&I strategies and to identify the critical parameters for this outcome. The dynamic stochastic simulation model consists of 3 hospitals with general wards and intensive care units (ICUs) and incorporates readmission of carriers of MRSA. Patient flow between ICUs and wards was based on real observations. Baseline prevalence of MRSA was set at 20% in ICUs and hospital-wide at 5%; ranges of costs and infection rates were based on published data. Four S&I strategies were compared to a do-nothing scenario: S&I of previously documented carriers ("flagged" patients); S&I of flagged patients and ICU admissions; S&I of flagged and group of "frequent" patients; S&I of all hospital admissions (universal screening). Evaluated levels of efficacy of S&I were 10%, 25%, 50% and 100%. Our model predicts that S&I of flagged and S&I of flagged and ICU patients are the most cost-saving strategies with fastest return of investment. For low isolation efficacy universal screening and S&I of flagged and "frequent" patients may never become cost-saving. Universal screening is predicted to prevent hardly more infections than S&I of flagged and "frequent" patients, albeit at higher costs. Whether an intervention becomes cost-saving within 10 years critically depends on costs per infection in ICU, costs of screening and isolation efficacy.

Evaluation of pet contact as a risk factor for carriage of multidrug-resistant staphylococci in nursing home residents

BACKGROUND

Pets, often used as companionship and for psychological support in the therapy of nursing home residents, have been implicated as reservoirs for antibiotic-resistant bacteria. We investigated the importance of pets as reservoirs of multidrug-resistant (MDR) staphylococci in nursing homes.

METHODS

We assessed the carriage of MDR staphylococci in pets and in 2 groups of residents, those living in nursing homes with pets and those living without pet contacts. We collected demographic, health status, and human-pet contact data by means of questionnaires. We assessed potential bacteria transmission pathways by investigating physical resident-to-pet contact.

RESULTS

The observed prevalence of MDR staphylococci carriage was 84/229 (37%) in residents living with pets and 99/216 (46%) in those not living with pets (adjusted odds ratio [aOR], 0.6; 95% confidence interval [CI], 0.4-0.9). Active pet contact was associated with lower carriage of MDR staphylococci (aOR, 0.5; 95% CI, 0.4-0.8). Antibiotic treatment during the previous 3 months was associated with significantly increased risk for MDR carriage in residents (aOR, 3.1; 95% CI, 1.8-5.7).

CONCLUSIONS

We found no evidence that the previously reported benefits of pet contact are compromised by the increased risk of carriage of MDR staphylococci in residents associated with interaction with these animals in nursing homes. Thus, contact with pets, always under good hygiene standards, should be encouraged in these settings.

First report of methicillin-resistant Staphylococcus aureus Cordobes/Chilean clone involved in nosocomial infections in Brazil

SUMMARY Methicillin-resistant Staphylococcus aureus (MRSA) commonly causes infection in hospitalized patients. Resistance is due to the acquisition of mecA gene located on the chromosomal element SCCmec and to date 12 types have been identified. Specific epidemic clones of MRSA have emerged with enhanced ability to spread within and among hospitals and to cross national boundaries. We studied 30 isolates from patients with MRSA infections at two hospitals in Porto Alegre city from April to December, 2008 and determined their SCCmec type by PCR. Representative strains were typed by PFGE. Eighteen (60%) isolates carried SCCmec type III and had PFGE profiles clonally related to the previously characterized Brazilian epidemic clone, and 11 (36·7%) isolates with pulsotypes closely related to the Cordobes/Chilean clone harboured SCCmec type I. To the best of our knowledge, this is the first report of the appearance of Cordobes/Chilean clone involved in nosocomial infection in Brazil.