Molecular Surveillance of Clinical Methicillin-ResistantStaphylococcus aureusIsolates in Neonatal Intensive Care Units

A longitudinal molecular surveillance of clinical methicillin-resistant Staphylococcus aureus isolates in neonatal units in a teaching hospital, 2003-2018

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has been an important nosocomial pathogen in our neonatal units since 1990s. To understand the longitudinal changing molecular epidemiology of these MRSA isolates, we conducted this study.

MATERIALS

From 2003 to 2018, we collected clinical MRSA isolates from 536 infants hospitalized at neonatal units of a medical center in northern Taiwan. First isolate from each infant was characterized.

RESULTS

The case/isolate number ranged from 7 cases/isolates (the lowest) in 2010 to 71 cases/isolates (the highest) in 2004. Of the 536 isolates, a total of 15 pulsotypes were identified. Three major clones were identified and characterized as sequence type (ST) 239/pulsotype A/staphylococcal chromosomal cassette (SCC) mec III/Panton-Valentine leukocidin (PVL)-negative, accounting for 22.2% of the isolates, ST59/pulsotype C/SCCmec IV/PVL-negative, accounting for 34.3% and ST59/pulsotype D/SCCmec V_T/PVL-positive, accounting for 30.0%. The first clone (hospital strains) dominated in the first two years, and became weakened from 2005 through 2016. Clonal complex (CC) 59 (combined the second and third clones) dominated (>50% of the isolates) from 2005 through 2018. One community clone (ST573) demonstrated a marked increase since 2007 and vanished abruptly since 2010. Several minor MRSA clones emerged after 2010.

CONCLUSION

The molecular epidemiology of MRSA isolates in our neonatal units from 2003 to 2018 revealed that an epidemic as well as endemic hospital clone of ST239 dominated before 2005 and was replaced by the local community clone of CC59 thereafter.

Right-sided endocarditis caused by polyclonal Staphylococcus aureus infection

We present a case of bacterial endocarditis with both methicillin-sensitive and methicillin-resistant Staphylococcus aureus, which based on typing, originated from two distinct clones. Such a case may be misinterpreted by microbiology lab automation to be a monoclonal multi-drug resistant Staphylococcus aureus, while simple microbiology techniques will instantly reveal distinct clonality.

Vancomycin, teicoplanin, daptomycin, and linezolid MIC creep in methicillin-resistant Staphylococcus aureus is associated with clonality

The purpose of this study is to evaluate the susceptibility trend of vancomycin, teicoplanin, daptomycin, and linezolid against methicillin-resistant Staphylococcus aureus (MRSA) blood isolates of different clones over an 11-year period.From 2000 to 2010, all bloodstream MRSA isolates from Chang Gung Memorial Hospital in Taiwan were prospectively collected. Three periods, namely 2000 to 2001, 2004 to 2005, and 2010, were included and 124 MRSA isolates were selected from each period. Minimum inhibitory concentrations (MICs) were determined by E-test. All the isolates were molecularly characterized.MRSA molecular epidemiology evolved from 1 predominant pulsotype (type A) to 5 major pulsotypes of 3 clonal complexes (CC). Vancomycin, teicoplanin, and daptomycin MICs creep were observed, particularly for pulsotype A-CC 239-staphylococcal cassette chromosome mec (SCCmec) III though its prevalence dramatically decreased since 2004 to 2005. Throughout the study period, the overall vancomycin modal MIC was stable at 1.5 mg/L, but teicoplanin and linezolid modal MIC increased to 2 and 2 mg/L, respectively. Isolates with teicoplanin and linezolid ≧ 2 ug/mL belonged to multiple clones. Pulsotype F-ST5-SCCmec II with a high rate of teicoplanin MIC ≧ 2 ug/mL continued clonal spread. Teicoplanin MIC had a high correlation with linezolid MIC.Molecular epidemiology MRSA bloodstream isolates in northern Taiwan evolved from 2000 throughout 2010, which was subsequently associated with the changing distribution of antibiotic MICs. While vancomycin MIC level remained unchanged, teicoplanin, daptomycin, and linezolid MIC levels increased. The impact of these changes on clinical treatment response deserves further investigations.

What To Think If the Results of the National Institutes of Health Randomized Trial of Methicillin-ResistantStaphylococcus aureusand Vancomycin-ResistantEnterococcusControl Measures Are Negative (and Other Advice to Young Epidemiologists): A Review and an Au Revoir

The incidence of methicillin-resistantStaphylococcus aureus(MRSA) and vancomycin-resistantEnterococcus(VRE) infections continues to rise in National Nosocomial Infections Surveillance system hospitals, and these pathogens are reportedly causing more than 100,000 infections and many deaths each year in US healthcare facilities. This has led some to insist that control measures are now urgently needed, but several recent articles have suggested that isolation of patients does not work, is not needed, or is unsafe, or that a single cluster-randomized trial could be used to decide such matters. At least 101 studies have reported controlling MRSA infection and 38 have reported controlling VRE infection by means of active detection by surveillance culture and use of isolation for all colonized patients in healthcare settings where the pathogens are epidemic or endemic, in academic and nonacademic hospitals, and in acute care, intensive care, and long-term care settings. MRSA colonization and infection have been controlled to exceedingly low levels in multiple nations and in the state of Western Australia for decades by use of active detection and isolation. Studies suggesting problems with using such data to control MRSA colonization and infection have their own problems, which are discussed. Randomized trials are epidemiologic tools that can sometimes provide erroneous results, and they have not been considered necessary for studying isolation before it is used to control other important infections, such as tuberculosis, smallpox, and severe acute respiratory syndrome. No single epidemiologic study should be considered definitive. One should always weigh all available evidence. Infection with antibiotic-resistant pathogens such as MRSA and VRE is controllable to a low level by active detection and isolation of colonized and infected patients. Effective measures should be used to minimize the morbidity and mortality attributable to these largely preventable infections.

Methicillin-resistant Staphylococcus aureus transmission and infections in a neonatal intensive care unit despite active surveillance cultures and decolonization: challenges for infection prevention

OBJECTIVE

To characterize the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) transmission and infections in a level IIIC neonatal intensive care unit (NICU) and identify barriers to MRSA control.

SETTING AND DESIGN

Retrospective cohort study in a university-affiliated NICU with an MRSA control program including weekly nares cultures of all neonates and admission nares cultures for neonates transferred from other hospitals or admitted from home.

METHODS

Medical records were reviewed to identify neonates with NICU-acquired MRSA colonization or infection between April 2007 and December 2011. Compliance with hand hygiene and an MRSA decolonization protocol were monitored. Relatedness of MRSA strains were assessed using pulsed-field gel electrophoresis (PFGE).

RESULTS

Of 3,536 neonates, 74 (2.0%) had a culture grow MRSA, including 62 neonates with NICU-acquired MRSA. Nineteen of 74 neonates (26%) had an MRSA infection, including 8 who became infected before they were identified as MRSA colonized, and 11 of 66 colonized neonates (17%) developed a subsequent infection. Of the 37 neonates that underwent decolonization, 6 (16%) developed a subsequent infection, and 7 of 14 (50%) that remained in the NICU for 21 days or more became recolonized with MRSA. Using PFGE, there were 14 different strain types identified, with USA300 being the most common (31%).

CONCLUSIONS

Current strategies to prevent infections-including active identification and decolonization of MRSA-colonized neonates-are inadequate because infants develop infections before being identified as colonized or after attempted decolonization. Future prevention efforts would benefit from improving detection of MRSA colonization, optimizing decolonization regimens, and identifying and interrupting reservoirs of transmission.

Prevalence and molecular characterization of Staphylococcus aureus colonization among neonatal intensive care units in Taiwan

BACKGROUND

Staphylococcus aureus, particularly methicillin-resistant (MRSA), is an important pathogen in neonatal intensive care units (NICUs). Carriage of S. aureus is a significant risk factor for subsequent infection.

OBJECTIVES

To determine the current status of MRSA prevalence among NICU-hospitalized infants in Taiwan, we conducted this pilot island-wide survey.

METHODS

On two designated dates in 2011, each patient who stayed in the NICUs of 7 participating hospitals was included. Nasal and umbilical swabs were obtained and sent for detection of S. aureus. The prevalence and risk factors for MRSA carriage were analyzed. MRSA strains were tested for antimicrobial susceptibility and underwent molecular characterization.

RESULTS

A total of 251 subjects were included. The overall prevalence of S. aureus and MRSA carriage was 13 and 4.4%, respectively. Previous skin and soft tissue infection was the only predictor in multivariate analysis (OR 40.36; 95% CI 2.32-702.64; p = 0.011). Among 11 MRSA isolates, 3 pulsotypes were identified, with one major type (73%). Nine isolates carried a type IV staphylococcal chromosomal cassette, and 2 carried the type VT. All but one MRSA isolate belonged to linage sequence type 59, the community clone in Taiwan.

CONCLUSIONS

On a designated date, 4.4% of the infants staying in NICUs in Taiwan carried almost genetically identical community strains of MRSA. MRSA colonization in these infants was significantly associated with previous skin and soft tissue infection.

Successful control of methicillin-resistant Staphylococcus aureus in endemic neonatal intensive care units--a 7-year campaign

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is among the most important nosocomial pathogens in the intensive care unit (ICU) worldwide, including Taiwan. Since 1997, our neonatal ICUs (NICUs) had become endemic for MRSA.

Methodology/Principal Findings

To control MRSA spread in our NICUs, we implemented a series of infection control measures stepwise, including reinforcement of hand hygiene since January 2000, augmentation of aseptic care over the insertion site of central venous catheter since July 2001, introduction of alcohol-based handrubs since April 2003, surveillance culture for MRSA and cohort care for the colonized patients between March 2003 and February 2004, and surveillance culture with subsequent decolonization of MRSA between August 2005 and July 2006. After implementation of these measures, MRSA healthcare-associated infection (HAI) density reduced by 92%, from 5.47 episodes per 1000 patient-days in 1999 to 0.45 episodes per 1000 patient-days in 2006; MRSA bloodstream infection reduced from 40 cases in 1999 to only one case in 2006. Compared to those obtained during the period of surveillance culture without decolonization, both rates of MRSA colonization (8.6% vs. 41%, p<0.001) and infection (1.1% vs. 12%, p<0.001) decreased significantly during the period of surveillance and decolonization. Molecular analysis of the clinical isolates during the study period showed that the endemic clone, which dominated between 1998 and 2005, almost disappeared in 2006, while the community clones increased significantly in 2006–2007.

Conclusion/Significance

Through infection control measures, MRSA HAIs can be successfully controlled, even in areas with high levels of endemic MRSA infections such as our NICUs.

The potential economic value of a Staphylococcus aureus vaccine for neonates

The continuing morbidity and mortality associated with Staphylococcus aureus (S. aureus) infections, especially methicillin-resistant S. aureus (MRSA) infections, have motivated calls to make S. aureus vaccine development a research priority. We developed a decision analytic computer simulation model to determine the potential economic impact of a S. aureus vaccine for neonates. Our results suggest that a S. aureus vaccine for the neonatal population would be strongly cost-effective (and in many situations dominant) over a wide range of vaccine efficacies (down to 10%) for vaccine costs (or=1%).

Comparative molecular analysis of community-associated and healthcare-associated methicillin-resistant Staphylococcus aureus isolates from children in northern Taiwan

From August 2004 to July 2005, 210 clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates were collected prospectively from 173 children admitted to Chang Gung Children's Hospital in Taiwan. A comparative molecular analysis of the 111 community-associated (CA) isolates from 102 children and the 99 healthcare-associated (HA) isolates from 71 children was conducted. In comparison to the HA isolates (31%), the CA isolates (90%) were more likely to have been isolated from pus (p <5 x 10(-8)). For each patient with MRSA infection, only the first isolate was selected for molecular analysis. The molecular characteristics differed significantly between the CA and the HA isolates (p <5 x 10(-8)). The clone characterized as sequence type (ST)59/pulsotype D (similar to USA1000)/staphylococcal chromosomal cassette (SCC)mec V(T)/Panton-Valentine leukocidin (PVL)-positive accounted for 69% of the CA isolates, and another clone, characterized as ST239/pulsotype A (Hungary clone)/SCCmec III/PVL-negative, accounted for 45% of the 71 HA isolates. The CA clone of ST59 also accounted for 20% of the HA isolates, including 47% of the 17 community-onset isolates. It was concluded that the molecular characteristics of clinical MRSA isolates from children differed significantly between the CA and the HA isolates in northern Taiwan. However, the CA clone of ST59 was also identified in a substantial proportion of HA isolates.

Prevalence of methicillin-resistant Staphylococcus aureus nasal colonization among Taiwanese children in 2005 and 2006

From July 2005 to October 2006, a total of 3,046 children, of ages between 2 months and 5 years, presented for a well-child health care visit to one of three medical centers, which are located in the northern, central, and southern parts of Taiwan, and were surveyed for nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA). The overall prevalences of S. aureus and MRSA nasal carriage among the children were 23% and 7.3%, respectively (18% and 4.8% in the central region, 25% and 6.7% in the southern region, and 27% and 9.5% in the northern region). Of the 212 MRSA isolates (96%) available for analysis, a total of 10 pulsed-field gel electrophoresis (PFGE) patterns with two major patterns (C [61%] and D [28%]) were identified. One hundred forty-nine isolates (70%) contained type IV staphylococcal cassette chromosome mec (SCCmec) DNA, and 55 isolates (26%) contained SCCmec V(T). The presence of Panton-Valentine Leukocidin (PVL) genes was detected in 60 isolates (28%). Most MRSA isolates belonged to one of two major clones, characterized as sequence type 59 (ST59)/PFGE C/SCCmec IV/absence of PVL genes (59%) and ST59/PFGE D/SCCmec V(T)/presence of PVL genes (25%). We concluded that between 2005 and 2006, 7.3% of healthy Taiwanese children were colonized by MRSA in nares. MRSA harbored in healthy children indicates an accelerated spread in the community.

Methicillin-resistant Staphylococcus aureus colonization and its association with infection among infants hospitalized in neonatal intensive care units

OBJECTIVES

We conducted this study to assess the rate of methicillin-resistant Staphylococcus aureus colonization and its association with infection among infants hospitalized in methicillin-resistant S aureus-endemic NICUs.

METHODS

Between March 2003 and February 2004, surveillance culture specimens from the nares, postauricular areas, axillae, and umbilicus of infants admitted to the NICUs at a children's hospital in Taiwan were obtained weekly for the detection of methicillin-resistant S aureus. All colonized and clinical isolates from each study infant with methicillin-resistant S aureus infection were genotyped with pulsed-field gel electrophoresis, with Sma1 digestion, and compared.

RESULTS

A total of 783 infants were included in this study. Methicillin-resistant S aureus colonization was detected for 323 infants during their NICU stays, with detection with the first 2 samples for 89%. Nares and umbilicus were the 2 most common sites of initial colonization. Methicillin-resistant S aureus colonization was associated significantly with premature birth (< or = 28 weeks) and low birth weight (< or = 1500 g), and infants with colonization had a significantly higher rate of methicillin-resistant S aureus infection, compared with those without colonization (26% vs 2%). Methicillin-resistant S aureus colonization was noted for 84 of 92 infants with methicillin-resistant S aureus infections. Of the 68 episodes with previous colonization and isolates available for genotyping analysis, colonized and clinical isolates were indistinguishable in 63 episodes, highly related in 2 episodes, and distinct in 3 episodes.

CONCLUSIONS

More than 40% of the hospitalized infants were colonized with methicillin-resistant S aureus during their stay in methicillin-resistant S aureus-endemic NICUs; this was associated significantly with methicillin-resistant S aureus infection. Most infants with methicillin-resistant S aureus infections had previous colonization with an indistinguishable strain.

Changing molecular epidemiology of methicillin-resistant Staphylococcus aureus bloodstream isolates from a teaching hospital in Northern Taiwan

A changing molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream isolates from a university-affiliated hospital in Taiwan during a 4-year interval was demonstrated. The changing epidemiology is due to the introduction of a new epidemic clone (sequence type 5) and a local community clone (sequence type 59) of MRSA into the hospital.

Control of a cluster of community-associated, methicillin-resistant Staphylococcus aureus in neonatology

To control an outbreak of community-associated MRSA (CA-MRSA) in a neonatology unit, an investigation was conducted that involved screening neonates and parents, molecular analysis of MRSA isolates and long-term follow-up of cases. During a two-month period in the summer of 2000, Panton-Valentine leukocidin (PVL)-producing CA-MRSA (strain ST5-MRSA-IV) was detected in five neonates. The mother of the index caseshowed signs of mastitis and wound infection and consequently tested positive for CA-MRSA. A small cluster of endemic, PVL-negative MRSA strains (ST228-MRSA-I) occurred in parallel. Enhanced hygiene measures, barrier precautions, topical decolonization of carriers, and cohorting of new admissions terminated the outbreak. Four months after the outbreak, the mother of another neonate developed furunculosis with the epidemic CA-MRSA strain. One infant had persistent CA-MRSA carriage resulting in skin infection in a sibling four years after the outbreak. In conclusion, an epidemic CA-MRSA strain was introduced by the mother of the index case. This spread among neonates and was subsequently transmitted to another mother and a sibling. This is the first report of a successfully controlled neonatology outbreak of genetically distinct PVL-producing CA-MRSA in Europe.