Community-associated meticillin-resistant Staphylococcus aureus in children in Taiwan, 2000s

Risk Factors for Severe Respiratory Syncytial Virus Infection in Hospitalized Children

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of bronchiolitis and pneumonia in infants and young children. Starting in December 2010, RSV monoclonal antibody (RSV mAb) was endorsed by Taiwan National Health Insurance and given to children with prematurity and/or congenital heart diseases, which are considered high-risk factors for severe RSV diseases. Investigating other important contributing risk factors is warranted.

METHODS

We conducted a cohort study at National Taiwan University Hospital to determine the rate of severe outcomes among children hospitalized due to RSV infection from 2008 to 2018. Adjusted for age, sex and birth cohorts born before and after RSV mAb endorsement, we identified risk factors for severe RSV infection, defined as the requirement of invasive ventilator support.

RESULTS

There were 1985 admissions due to RSV infections. Among them, 66 patients (3.3%) had severe RSV infection. The proportion of severe RSV infections decreased significantly after RSV mAb endorsement. Multivariable analysis revealed that age <1.5 months and cardiovascular and congenital/genetic diseases were high-risk underlying conditions. In addition, bacterial coinfections, elevated creatinine levels and initial abnormal chest radiograph findings posed warning signs for severe RSV infection.

CONCLUSIONS

Children younger than 1.5 months of age with cardiovascular or congenital/genetic diseases were predisposed to severe RSV infection and might benefit from RSV mAb prophylaxis.

Dissemination of meticillin-resistant Staphylococcus aureus sequence type 8 (USA300) in Taiwan

BACKGROUND

In Taiwan, sequence type (ST) 239 and ST59 were two major clones among meticillin-resistant Staphylococcus aureus (MRSA) clinical isolates in the past two decades. USA300 (ST8) prevailed in the Americas but not in outside areas. Recently USA300 (ST8) emerged and was increasingly identified in Taiwan; we thus conducted an island-wide study to explore the role of USA300 among MRSA isolates.

METHODS

One hundred MRSA bloodstream isolates identified in 2020 from each of the six participating hospitals in Taiwan were collected and characterized. The first 10 ST8 isolates from each hospital were further analysed by whole-genome sequencing.

RESULTS

Of the 590 confirmed MRSA isolates, a total of 22 pulsotypes and 21 STs were identified. The strain of pulsotype AI/ST8 was the most common lineage identified, accounting for 187 isolates (31.7%) and dominating in five of six hospitals, followed by pulsotype A/ST239 (14.7%), pulsotype C/ST59 (13.9%) and pulsotype D/ST59 (9.2%). Of the 187 pulsotype AI/ST8 isolates, 184 isolates were characterized as USA300 and clustered in three major sub-pulsotypes, accounting for 78%. Ninety per cent of the 60 ST8 isolates for whole-genome sequencing were clustered in three major clades.

CONCLUSIONS

In 2020, USA300 became the most common clone of MRSA in Taiwan, accounting for >30% of MRSA bloodstream isolates island wide. Most of USA300 isolates circulating in Taiwan might have been imported on multiple occasions and evolved into at least three successful local clades. MRSA USA300 has successfully established its role in Taiwan, an area outside of the Americas.

Virulence attributes of successful methicillin-resistant Staphylococcus aureus lineages

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of severe and often fatal infections. MRSA epidemics have occurred in waves, whereby a previously successful lineage has been replaced by a more fit and better adapted lineage. Selection pressures in both hospital and community settings are not uniform across the globe, which has resulted in geographically distinct epidemiology. This review focuses on the mechanisms that trigger the establishment and maintenance of current, dominant MRSA lineages across the globe. While the important role of antibiotic resistance will be mentioned throughout, factors which influence the capacity of S. aureus to colonize and cause disease within a host will be the primary focus of this review. We show that while MRSA possesses a diverse arsenal of toxins including alpha-toxin, the success of a lineage involves more than just producing toxins that damage the host. Success is often attributed to the acquisition or loss of genetic elements involved in colonization and niche adaptation such as the arginine catabolic mobile element, as well as the activity of regulatory systems, and shift metabolism accordingly (e.g., the accessory genome regulator, agr). Understanding exactly how specific MRSA clones cause prolonged epidemics may reveal targets for therapies, whereby both core (e.g., the alpha toxin) and acquired virulence factors (e.g., the Panton-Valentine leukocidin) may be nullified using anti-virulence strategies.

A Review on Five and Six-Membered Heterocyclic Compounds Targeting the Penicillin-Binding Protein 2 (PBP2A) of Methicillin-Resistant Staphylococcus aureus (MRSA)

Staphylococcus aureus is a common human pathogen. Methicillin-resistant Staphylococcus aureus (MRSA) infections pose significant and challenging therapeutic difficulties. MRSA often acquires the non-native gene PBP2a, which results in reduced susceptibility to β-lactam antibiotics, thus conferring resistance. PBP2a has a lower affinity for methicillin, allowing bacteria to maintain peptidoglycan biosynthesis, a core component of the bacterial cell wall. Consequently, even in the presence of methicillin or other antibiotics, bacteria can develop resistance. Due to genes responsible for resistance, S. aureus becomes MRSA. The fundamental premise of this resistance mechanism is well-understood. Given the therapeutic concerns posed by resistant microorganisms, there is a legitimate demand for novel antibiotics. This review primarily focuses on PBP2a scaffolds and the various screening approaches used to identify PBP2a inhibitors. The following classes of compounds and their biological activities are discussed: Penicillin, Cephalosporins, Pyrazole-Benzimidazole-based derivatives, Oxadiazole-containing derivatives, non-β-lactam allosteric inhibitors, 4-(3H)-Quinazolinones, Pyrrolylated chalcone, Bis-2-Oxoazetidinyl macrocycles (β-lactam antibiotics with 1,3-Bridges), Macrocycle-embedded β-lactams as novel inhibitors, Pyridine-Coupled Pyrimidinones, novel Naphthalimide corbelled aminothiazoximes, non-covalent inhibitors, Investigational-β-lactam antibiotics, Carbapenem, novel Benzoxazole derivatives, Pyrazolylpyridine analogues, and other miscellaneous classes of scaffolds for PBP2a. Additionally, we discuss the penicillin-binding protein, a crucial target in the MRSA cell wall. Various aspects of PBP2a, bacterial cell walls, peptidoglycans, different crystal structures of PBP2a, synthetic routes for PBP2a inhibitors, and future perspectives on MRSA inhibitors are also explored.

Insight into the Clonal Lineage and Antimicrobial Resistance of Staphylococcus aureus from Vascular Access Infections before and during the COVID-19 Pandemic

Patients receiving hemodialysis are at risk of vascular access infections (VAIs) and are particularly vulnerable to the opportunistic pathogen Staphylococcus aureus. Hemodialysis patients were also at increased risk of infection during the COVID-19 pandemic. Therefore, this study determined the change in the molecular and antibiotic resistance profiles of S. aureus isolates from VAIs during the pandemic compared with before. A total of 102 S. aureus isolates were collected from VAIs between November 2013 and December 2021. Before the pandemic, 69 isolates were collected, 58%, 39.1%, and 2.9% from arteriovenous grafts (AVGs), tunneled cuffed catheters (TCCs), and arteriovenous fistulas (AVFs), respectively. The prevalence of AVG and TCC isolates changed to 39.4% and 60.6%, respectively, of the 33 isolates during the pandemic. Sequence type (ST)59 was the predominant clone in TCC methicillin-resistant S. aureus (MRSA) and AVG-MRSA before the pandemic, whereas the predominant clone was ST8 in AVG-MRSA during the pandemic. ST59 carrying the ermB gene was resistant to clindamycin and erythromycin. By contrast, ST8 carrying the msrA gene was exclusively resistant to erythromycin. The ST distribution for different VAIs changed from before to during the pandemic. The change in antibiotic resistance rate for different VAIs was closely related to the distribution of specific STs.

Acute bacterial skin and skin structure infections in pediatric patients: potential role of dalbavancin

INTRODUCTION

Acute bacterial skin and skin structure infections (ABSSSIs) are a subtype of skin and soft tissue infections (SSTI), usually sustained by Gram-positive bacteria, whose incidence is high among children. ABSSSIs are responsible for a considerable number of hospitalizations. Moreover, as multidrug resistant (MDR) pathogens become widespread, the pediatric category seems burdened with an increased risk of resistance and treatment failure.

AREAS COVERED

To obtain a view on the status of the field, we describe the clinical, epidemiological, and microbiological aspects of ABSSSI in children. Old and new treatment options were critically revised with a focus on the pharmacological characteristics of dalbavancin. Evidence on the use of dalbavancin in children was collected, analyzed, and summarized.

EXPERT OPINION

Many of the therapeutic options available at the moment are characterized by the need for hospitalization or repeated intravenous infusions, safety issues, possible drug-drug interactions, and reduced efficacy on MDRs. Dalbavancin, the first long-acting molecule with strong activity against methicillin-resistant and also many vancomycin-resistant pathogens represents a game changer for adult ABSSSI. In pediatric settings, the available literature is still limited, but a growing body of evidence supports dalbavancin use in children with ABSSSI, demonstrating this drug to be safe and highly efficacious.

Diversity and Dissemination of Methicillin-Resistant Staphylococcus aureus (MRSA) Genotypes in Southeast Asia

Methicillin-resistant Staphylococcus aureus (MRSA) is a successful pathogen that has achieved global dissemination, with high prevalence rates in Southeast Asia. A huge diversity of clones has been reported in this region, with MRSA ST239 being the most successful lineage. Nonetheless, description of MRSA genotypes circulating in the Southeast Asia region has, until now, remained poorly compiled. In this review, we aim to provide a better understanding of the molecular epidemiology and distribution of MRSA clones in 11 Southeast Asian countries: Singapore, Malaysia, Thailand, Vietnam, Cambodia, Lao People's Democratic Republic (PDR), Myanmar, Philippines, Indonesia, Brunei Darussalam, and Timor-Leste. Notably, while archaic multidrug-resistant hospital-associated (HA) MRSAs, such as the ST239-III and ST241-III, were prominent in the region during earlier observations, these were then largely replaced by the more antibiotic-susceptible community-acquired (CA) MRSAs, such as ST22-IV and PVL-positive ST30-IV, in recent years after the turn of the century. Nonetheless, reports of livestock-associated (LA) MRSAs remain few in the region.

Molecular characterization and virulence gene profiling of methicillin-resistant Staphylococcus aureus associated with bloodstream infections in southern China

Methicillin-resistant Staphylococcus aureus (MRSA) causes an enormous illness burden, including skin and soft tissue infections (SSTIs), pneumonia, bloodstream infections (BSI), and sepsis. BSI are associated with significant patient morbidity and mortality worldwide. However, limited information is available on MRSA-related BSI in China. This study aimed to investigate the molecular characterization of 77 MRSA isolates recovered from hospitalized patients with BSI between 2012 and 2020 at three first-class tertiary hospitals in southern China based on multilocus sequence typing (MLST), spa typing, and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, 13 clonal complexes (CCs) were identified, with CC59 and CC5 being the largest clusters, indicating high genetic diversity among BSI-causing MRSA isolates. ST59 was the most prevalent MLST type (22.1%). ST5/ST764-MRSA SCCmec II was the predominant adult MRSA clone, whereas ST59-MRSA SCCmec IV was the most common pediatric MRSA clone. ST5-t2460, ST764-t1084, and ST59-t437 were the most common types of adult MRSA isolates, whereas ST59-t437 and ST59-t172 were the predominant types of children’s MRSA isolates. ST59-SCCmec IV/V represented the most common clone among community acquired-MRSA isolates. ST5/ST764-SCCmec II was the most common type of hospital-associated MRSA isolate. The most prevalent toxin-encoding genes detected were hla, hld, icaA, and clfA (96.1–100%). Forty-three (100%, 43/43) isolates harbored more than 18 of the tested virulence genes in adults and eight virulence genes (23.5%, 8/34) in children. Virulence gene analysis revealed diversity among different clones: the positivity rates for the Panton-Valentine leukocidin (PVL) gene were 55.8 and 35.3% in adult and pediatric MRSA isolates, respectively; the genes seb–sei were present in all adult strains; seb–seg–sei–seo were present in all ST5, ST59, ST15, ST45, and ST22 adult strains; and seg–sei–sem–sen–seo were present in different clones, including ST15, ST45, and ST22 adult MRSA isolates and ST25, ST30, ST546, and ST72 children’s MRSA isolates. Adult MRSA isolates had significantly higher antibiotic resistance rates and virulence gene prevalence than pediatric MRSA isolates. For 8 years, this study provided epidemiological data on the molecular characteristics and virulence genes in different groups of MRSA BSI in China. Our findings may provide critical information for a better understanding of MRSA BSI.

Staphylococcus aureus Keratitis in Taiwan: Genotyping, Antibiotic Susceptibility, and Clinical Features

Staphylococcus aureus is an important pathogen for keratitis, a vision-threatening disease. We aimed to investigate the genotyping, antibiotic susceptibility, and clinical features of S. aureus keratitis, and to explore the possible role of Panton–Valentine leucocidin (PVL), a major virulence factor of S. aureus. We recruited 49 patients with culture-proven S. aureus keratitis between 2013 and 2017 at Chang Gung Memorial Hospital, Taiwan. PVL gene, multilocus sequence type (MLST), staphylococcal cassette chromosome mec (SCCmec), and pulsed-field gel electrophoresis (PFGE) were performed. Antibiotic susceptibility was verified using disk diffusion/E test. There were 49 patients with S. aureus keratitis; 17 (34.7%) were caused by methicillin-resistant S. aureus (MRSA) and 9 (18.4%) isolates had PVL genes. The predominant genotyping of MRSA isolates was CC59/PFGE type D/SCCmec VT/PVL (+). All methicillin-sensitive S. aureus (MSSA) and approximately 60% MRSA were susceptible to fluoroquinolones. No significant differences in clinical features, treatments, and visual outcomes were observed between MRSA/MSSA or PVL(+)/PVL(−) groups. In Taiwan, approximately one third of S. aureus keratitis was caused by MRSA, mainly community-associated MRSA. Although MRSA isolates were more resistant than MSSA, clinical characteristics were similar between two groups. Fluoroquinolones could be good empiric antibiotics for S. aureus keratitis.

Community-Associated Methicillin-Resistant Staphylococcus Aureus Colonization in a Birth Cohort of Early Childhood: The Role of Maternal Carriage

Background: Methicillin-resistant Staphylococcus aureus (MRSA) colonization in infants may pose a risk for subsequent infection in children. The study aimed to determine S. aureus colonization patterns in infancy, and strain relatedness between maternal and infant colonization.

Methods: A prospective cohort study was conducted for nasopharyngeal S. aureus detection in neonates at delivery; in children at 1, 6, 12, 24, 36, and 60 months of age; and from mothers immediately after the delivery of their baby and when their child is 1 month old. A questionnaire for infants and mothers was administered at each planned visit.

Results: In total, 521 and 135 infant–mother dyads underwent nasopharyngeal swab collection at 1 month and immediately after delivery, respectively. Among the 521 dyads at 1 month of age, concordant S. aureus colonization was found in 95 dyads, including MRSA in 48.4% (46/95). No concordant MRSA carriage was present among the 135 dyads at delivery. The genetic relatedness of concurrent MRSA-colonized dyads showed that more than two-thirds (32/46 [69.6%]) had identical genotypes, mainly ST 59/PVL-negative/SCCmec IV. Infants aged 1 month had the highest incidence of S. aureus, and the trend declined to a nadir at the age of 12 months. Carrier mothers who smoked cigarettes may increase the risk of infant Staphylococcus colonization (odds ratio, 2.12; 95% confidence interval, 1.23–3.66; p < 0.01).

Conclusions: Maternal–infant horizontal transmission may be the primary source of MRSA acquisition in early infancy. The avoidance of passive smoking could be recommended for the prevention of S. aureus carriage.

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.

Drivers of methicillin-resistant Staphylococcus aureus (MRSA) lineage replacement in China

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen subdivided into lineages termed sequence types (STs). Since the 1950s, successive waves of STs have appeared and replaced previously dominant lineages. One such event has been occurring in China since 2013, with community-associated (CA-MRSA) strains including ST59 largely replacing the previously dominant healthcare-associated (HA-MRSA) ST239. We previously showed that ST59 isolates tend to have a competitive advantage in growth experiments against ST239. However, the underlying genomic and phenotypic drivers of this replacement event are unclear.

METHODS

Here, we investigated the replacement of ST239 using whole-genome sequencing data from 204 ST239 and ST59 isolates collected in Chinese hospitals between 1994 and 2016. We reconstructed the evolutionary history of each ST and considered two non-mutually exclusive hypotheses for ST59 replacing ST239: antimicrobial resistance (AMR) profile and/or ability to colonise and persist in the environment through biofilm formation. We also investigated the differences in cytolytic activity, linked to higher virulence, between STs. We performed an association study using the presence and absence of accessory virulence genes.

RESULTS

ST59 isolates carried fewer AMR genes than ST239 and showed no evidence of evolving towards higher AMR. Biofilm production was marginally higher in ST59 overall, though this effect was not consistent across sub-lineages so is unlikely to be a sole driver of replacement. Consistent with previous observations of higher virulence in CA-MRSA STs, we observed that ST59 isolates exhibit significantly higher cytolytic activity than ST239 isolates, despite carrying on average fewer putative virulence genes. Our association study identified the chemotaxis inhibitory protein (chp) as a strong candidate for involvement in the increased virulence potential of ST59. We experimentally validated the role of chp in increasing the virulence potential of ST59 by creating Δchp knockout mutants, confirming that ST59 can carry chp without a measurable impact on fitness.

CONCLUSIONS

Our results suggest that the ongoing replacement of ST239 by ST59 in China is not associated to higher AMR carriage or biofilm production. However, the increase in ST59 prevalence is concerning since it is linked to a higher potential for virulence, aided by the carriage of the chp gene.

Evolution and Population Structures of Prevalent Methicillin-Resistant Staphylococcus aureus in Taiwan

Global methicillin-resistant Staphylococcus aureus (MRSA) strains were dominated by few genetic lineages, suggesting their inherent advantage of competitive fitness. The information of genome evolution and population structures of prevalent MRSA strains can help gain a better understanding of the success of the pandemic clones. Whole-genome sequencing was performed in 340 MRSA isolates belonging to three prevalent lineages, including ST59 (129 isolates), ST239/241 (140 isolates), and ST5 (71 isolates), collected from 1996 to 2016 in Taiwan. The time-scaled phylogeny and evolutionary pathways were estimated by Bayesian analysis using Markov chain Monte Carlo. The toxome, resistome, and plasmids were characterized by screening the raw reads with a public database. ST59, ST239/241, and ST5 MRSA were estimated to emerge in 1974, 1979, and 1995, respectively, in Taiwan. ST59 evolved through two major pathways, generating two subclones in 1980 and 1984. Both ST59 subclones remained prevalent in the healthcare and community environments in late 2010s. ST239/241 diverged into three subclones, respectively, in 1989, 1993, and 1995. The 1995-emerging ST239 subclone predominated after 2000 by replacing two previous early subclones. ST5 could be subdivided into two clades within 3 years of introduction, but no substantial difference of genomic profiles was identified in the strains of distinct clades. Each of the three pandemic MRSA lineages harbored its own specific toxome, resistome, and plasmids. The frequently identified genetic diversities between the subclones of the same lineage were genes mediating immune evasion, leukocidins, enterotoxins, and resistance to aminoglycosides. In conclusion, MRSA ST59 and ST239/241 emerged in the 1970s and evolved drastically during 1980 and 1995, resulting in three successful subclones prevailing in Taiwan. ST5 was introduced late in 1995 without a significant genetic drift during 20 years of evolution.

Nasal Methicillin-Resistant Staphylococcus aureus Colonization in Patients with Type 1 Diabetes in Taiwan

Nasal methicillin-resistant Staphylococcus aureus (MRSA) colonies are an essential reservoir of infection, especially for patients with diabetes. However, data on MRSA colonization in patients with type 1 diabetes are limited. We investigated the epidemiology of MRSA colonization in patients with type 1 diabetes. This prospective cross-sectional study was conducted in a medical center (Chang Gung Memorial Hospital) in Taiwan from 1 July to 31 December 2020. Nasal sampling and MRSA detection were performed. The molecular characteristics of MRSA isolates were tested, and factors associated with MRSA colonization were analyzed. We included 245 patients with type 1 diabetes; nasal MRSA colonization was identified in 13 (5.3%) patients. All isolates belonged to community-associated MRSA genetic strains; the most frequent strain was clonal complex 45 (53.8%), followed by ST59 (30.8%) (a local community strain). MRSA colonization was positively associated with age ≤ 10 years, body mass index < 18 kg/m², and diabetes duration < 10 years; moreover, it was negatively associated with serum low-density lipoprotein cholesterol ≥ 100 mg/dL. No independent factor was reported. The nasal MRSA colonization rate in type 1 diabetes is approximately 5% in Taiwan. Most of these colonizing strains are community strains, namely clonal complex 45 and ST59.

Whole genome sequence analysis of multi drug resistant community associated methicillin resistant Staphylococcus aureus from food fish: detection of clonal lineage ST 28 and its antimicrobial resistance and virulence genes

Methicillin-resistant staphylococcus aureus (MRSA) sequence type 28 (ST 28) and spa type t021 is a CC30, prototype of ST-30, Community Associated-MRSA (CA-MRSA) (lukS-lukF +). It is a multi-drug resistant strain harbouring staphylococcal endotoxins, haemolysins, ureolysin, serine protease, and antimicrobial resistance genes. In this study, we report the draft genome sequence of this MRSA isolated from the most commonly used food fish, ribbon fish (Trichiurus lepturus). The total number of assembled paired-end high-quality reads was 7,731,542 with a total length of  2.8Mb of 2797 predicted genes. The unique ST28/ t021 CA- MRSA in fish is the first report from India, and in addition to antibiotic resistance is known to co-harbour virulence genes, haemolysins, aureolysins and endotoxins. Comprehensive comparative genomic analysis of CA-MRSA strain7 can help further understand their diversity, genetic structure, diversity and a high degree of virulence to aid in fisheries management.

Methicillin-Resistant Staphylococcus aureus (MRSA) Clonal Replacement in a Malaysian Teaching Hospital: Findings from an Eight-Year Interval Molecular Surveillance

Periodical surveillance on nosocomial pathogens is important for antimicrobial stewardship and infection control. The first methicillin-resistant Staphylococcus aureus (MRSA) molecular surveillance in Hospital Canselor Tuanku Muhriz (HCTM), a Malaysian teaching hospital, was performed in 2009. The dominant clone was identified as an MRSA carrying SCCmec type III-SCCmercury with ccrC and sea+cna toxin genes. In this study, we report the findings of the second HCTM MRSA surveillance carried out in 2017, after an interval of 8 years. Antibiotic susceptibility testing, SCCmec, toxin gene, and spa typing were performed for 222 MRSA strains isolated in 2017. Most strains were resistant to ciprofloxacin, erythromycin, clindamycin, cefoxitin, and penicillin (n = 126, 56.8%), belong to SCCmec type IV (n = 205, 92.3%), spa type t032 (n = 160, 72.1%) and harboured seg+sei toxin genes (n = 172, 77.5%). There was significant association between resistance of the aforementioned antibiotics with SCCmec type IV (p < 0.05), t032 (p < 0.001), and seg+sei carriage (p < 0.05). Results from this second MRSA surveillance revealed the occurrence of clonal replacement in HCTM during an interval of not more than 8 years. Investigation of the corresponding phenotype changes in this new dominant MRSA clone is currently on-going.

High prevalence nasal carriage of methicillin-resistant Staphylococcus aureus among long term care facility healthcare workers in relation to patient contact

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a major public health concern worldwide. Healthcare workers (HCWs) are an important source of transmission of MRSA. We conducted a prospective study to define the frequency of S. aureus nasal colonization with emphasis on the carriage of MRSA in HCWs in relation to the intensity of patient contact.

Methods

Out-of-hospital care emergency medical technicians and students, and HCWs in the emergency department, intensive care unit and a long-term care facility (LTCF) were enrolled to compare the prevalence of MRSA and methicillin-susceptible S. aureus (MSSA) nasal colonization. The MRSA isolates were further identified by their microbiological and molecular characteristics.

Findings

S. aureus was isolated from 63 of 248 HCWs (25.4%). The overall MRSA nasal carriage rate was 15/248, 6%, and the prevalence was higher in the HCWs who had worked for 5–10 years (12.8%), and among female HCWs (10.3%) than male HCWs (0.9%). LTCFs had the highest prevalence (12%). In contrast, the overall carriage of MSSA was 48/248, 19.4%, and most carriers worked for ≥5 years (52.1%). Hospital nurses had the highest rate of MSSA carriage (21.4%). Most of the MRSA isolates were SCCmec IV/ST59 or ST45 (60%), and were resistant to erythromycin and clindamycin (53%).

Conclusions

Hospital nurses have highest S. aureus nasal carriage, whereas HCWs in the LTCFs comprise a significant reservoir of MRSA colonization. The differences in the characteristics of MRSA and MSSA nasal carriage among HCWs highlights the importance on long-term nasal screening of S. aureus in healthcare facilities.

A Possible Role of Insertion Sequence IS1216V in Dissemination of Multidrug-Resistant Elements MESPM1 and MES6272-2 between Enterococcus and ST59 Staphylococcus aureus

Sequence type 59 (ST59) is the dominant type of community-associated methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Previously, we reported that ST59 MRSA harbors enterococcal IS1216V-mediated multidrug-resistant composite transposons MESPM1 or MES6272-2. The MES were found to have a mosaic structure, largely originating in enterococci and partly native to S. aureus. The current study aimed to track the origin of the MES and how they disseminated from enterococci to ST59 S. aureus. A total of 270 enterococcal isolates were analyzed, showing that two ST64 Enterococcus faecalis isolated in 1992 and 11 clonal complex 17 Enterococcus faecium harbored MESPM1-like and MES6272-2-like structures, respectively. Sequence analysis revealed that ST64 E. faecalis strain N48 acquired the MESPM1-like structure on the plasmid pEflis48. The pEflis48 harbored the enterococci-originated region (erythromycin, kanamycin, and streptomycin resistances) and the S.aureus-originated region (chloramphenicol resistance) of MESPM1 but was separated by the replication region of the plasmid. Homologous recombination between the two direct repeats of IS1216V resulted in excision of the replication region of the plasmid to regenerate MESPM1. The p4780-1 and pV19 of E. faecium carried MES6272-2-like structures with IS1216V, albeit with multiple insertions by other insertion sequences. The findings show that IS1216V plays important roles in bidirectional gene transfer of multidrug resistance between enterococci and S. aureus.

Tracking the evolution of the two successful CC59 methicillin-resistant Staphylococcus aureus clones in Taiwan: the divergence time of the two clades is estimated to be the 1980s

Clonal complex 59 (CC59) is the dominant community-associated methicillin-resistant Staphylococcus aureus (MRSA) strain in Taiwan and includes the Asian-Pacific clone with Panton-Valentine leukocidin (PVL)-negative/staphylococcal cassette chromosome mec (SCCmec) IVg and the Taiwan clone characterised as PVL-positive/SCCmec V (5C2&5). Nevertheless, data on the evolutionary history of the two dominant CC59 MRSA clones in Taiwan are scarce. In this study, a total of 258 CC59 S. aureus strains from Taiwan were classified by multiple-locus variable-number tandem repeat analysis (MLVA), which revealed two major clusters (MT1 and MT2) with distinct mobile genetic elements (MGEs). However, sequencing and PCR mapping of the β-lactamase-producing plasmid revealed no difference among all CC59 S. aureus strains. Bayesian evolutionary analysis of 18 of the CC59 S. aureus strains based on core genome alignment revealed two clades: (i) Clade A, which shared the samples with MT1, had the features of mainly harbouring gentamicin-resistant MES_6272-2 or MES₄₅₇₈, φSA3 translocation in νSaβ and SCCmec IVg; and (ii) Clade B, which shared the samples with MT2, had the features of mainly harbouring streptomycin-resistant MES_PM1, PVL phage and SCCmec V (5C2&5). Based on the time-calibrated phylogenetic tree, the estimated time of divergence of the two clades was in the 1980s. These results suggest that the CC59 S. aureus progenitor acquired a β-lactamase-producing plasmid and then developed the varied genetic backgrounds, which were associated with the acquisition and maintenance of distinct MGEs, leading to differences in antimicrobial susceptibility profiles and molecular virulence determinants.

Detection and phylogeny of Staphylococcus aureus sequence type 398 in Taiwan

Background

Methicillin-resistant Staphylococcus aureus (MRSA) ST398 is a livestock associated-bacterium that is most prevalent in Europe. Human-adapted MRSA ST398 was recently reported from China, but there is no data available yet for Taiwan.

Methods

To identify S. aureus ST398 isolates, we examined 6413 S. aureus isolates (5632 MRSA and 781 susceptible strains) that were collected in Taiwan between 1995 and 2017. If isolates could not be typed by pulsed-field gel electrophoresis upon Sma I digestion, we performed further characterization and complete genome sequencing.

Results

We identified 18 ST398 S. aureus isolates from 16 subjects (0.28%), including 6 sensitive and 12 resistant strains. Of these, 14 were colonizing isolates, 3 were clinical (infecting) isolates and one isolate was from a pork specimen. All 3 infecting isolates were MSSA strains identified in 2015 from two children with recurrent otitis media or sinusitis. The other 3 MSSA isolates were identified from workers handling pork (2) or pork meat (1) in 2015. The first 5 MRSA colonizing isolates were identified from residents in two nursing homes in 2012. Six MRSA isolates were identified from residents and foreign employees at a nursing home in 2016 and one MRSA from a foreign worker in 2017. Phylogenetic analysis of genome sequences indicated that all 12 local ST398 MRSA strains cluster together, human-adapted and phylogenetically related to a human MRSA strain identified in China in 2002. Two local MSSA isolates could be linked to isolates from livestock. The toxin profiles were similar for the MRSA and MSSA isolates.

Conclusions

Our results demonstrate that S. aureus ST398 was present in Taiwan in 2012 and potentially earlier. Although some isolates could be linked to livestock, most ST398 S. aureus isolates identified in Taiwan, particularly MRSA, represent human-adapted strains. Local transmission of human-adapted MRSA ST398 strains has occurred in nursing homes in Taiwan, possibly after import from China. Further surveillance is needed.

Molecular characteristics of methicillin-resistant Staphylococcus aureus isolated from skin and soft tissue infections collected in the Japanese nationwide surveillance

Skin and soft tissue infections (SSTI) are a common infection among both outpatients and inpatients. The most frequently isolated bacterium in SSTI was Staphylococcus aureus, a quarter of which was methicillin-resistant S. aureus (MRSA). In this study, to investigate molecular epidemiology of the 141 MRSA strains collected in the Japanese nationwide surveillance, we performed multiplex real-time polymerase chain reaction to detect staphylococcal cassette chromosome mec (SCCmec) type and virulence genes. The percentage of SCCmec types I, II, III and IV was 1.4%, 52.5%, 5.7% and 40.4%, respectively. According to the SCCmec type, we classified the strains into health-care-associated (HA)-MRSA (n = 84) and community-associated (CA)-MRSA (n = 57). Among the virulence genes, the percentage of enterotoxin C gene-positive strains was significantly higher in CA-MRSA than in HA-MRSA. No significant differences were detected between the two groups in terms of antibiotic susceptibility and patients' background information, classification of SSTI or symptoms of SSTI.

Comparison of Methicillin-Resistant Staphylococcus aureus Isolates from Cellulitis and from Osteomyelitis in a Taiwan Hospital, 2016-2018

Methicillin-resistant Staphylococcus aureus (MRSA) causes superficial infections such as cellulitis or invasive infections such as osteomyelitis; however, differences in MRSA isolates from cellulitis (CL-MRSA) and from osteomyelitis (OM-MRSA) at the same local area remain largely unknown. A total of 221 MRSA isolates including 106 CL-MRSA strains and 115 OM-MRSA strains were collected at Chang-Gung Memorial Hospital in Taiwan between 2016 and 2018, and their genotypic and phenotypic characteristics were compared. We found that OM-MRSA isolates significantly exhibited higher rates of resistance to multiple antibiotics than CL-MRSA isolates. Genotypically, OM-MRSA isolates had higher proportions of the SCCmec type III, the sequence type ST239, and the spa type t037 than CL-MRSA isolates. Besides the multidrug-resistant lineage ST239-t037-SCCmecIII more prevalent in OM-MRSA, higher antibiotic resistance rates were also observed in several other prevalent lineages in OM-MRSA as compared to the same lineages in CL-MRSA. Furthermore, when prosthetic joint infection (PJI) associated and non-PJI-associated MRSA strains in osteomyelitis were compared, no significant differences were observed in antibiotic resistance rates between the two groups, albeit more diverse genotypes were found in non-PJI-associated MRSA. Our findings therefore suggest that deep infections may allow MRSA to evade antibiotic attack and facilitate the convergent evolution and selection of multidrug-resistant lineages.

Vascular access infection by Staphylococcus aureus from removed dialysis accesses

Hemodialysis patients are particularly vulnerable to Staphylococcus aureus infection, with the vascular access serving as the site of entry for this formidable pathogen. Patients with arteriovenous grafts (AVGs) and tunneled‐cuffed catheters (TCCs) are at elevated risk of S. aureus infection. In this study, we investigated the correlation between the clinical characteristics of S. aureus vascular access infection (VAI), molecular profiles, and the biofilm formation abilities of clinical isolates of S. aureus. We collected samples of methicillin‐resistant S. aureus (MRSA), methicillin‐sensitive S. aureus (MSSA), and methicillin‐sensitive S. argenteus (MSSAg) from patients with S. aureus VAI and patients with other infections. The molecular profiles of the clinical isolates were determined using disk diffusion testing and molecular typing. The biofilm formation ability was determined by microtiter plate assay. In total, 63 S. aureus and 10 S. argenteus isolates were identified: 40 MRSA, 23 MSSA, and ten MSSAg. MRSA was highly prevalent (77.8%) in TCC isolates and was multidrug resistant. Of the 40 MRSA isolates, ST239‐SCCmec III was the predominant clone. SCCmec type IV was the predominant type (35%) in isolates from AVGs, while SCCmec type III was prevalent in TCC infection and showed significantly higher biofilm formation ability than types IV and V. In dialysis VAI by S. aureus, patients with TCC were more often infected with MRSA than patients with AVG, and MRSA in TCC–VAI was predominantly SCCmec type III, which had the strongest drug resistance and biofilm formation ability.

Application of a MALDI-TOF analysis platform (ClinProTools) for rapid and preliminary report of MRSA sequence types in Taiwan

Background

The accurate and rapid preliminarily identification of the types of methicillin-resistant Staphylococcus aureus (MRSA) is crucial for infection control. Currently, however, expensive, time-consuming, and labor-intensive methods are used for MRSA typing. By contrast, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a potential tool for preliminary lineage typing. The approach has not been standardized, and its performance has not been analyzed in some regions with geographic barriers (e.g., Taiwan Island).

Methods

The mass spectra of 306 MRSA isolates were obtained from multiple reference hospitals in Taiwan. The multilocus sequence types (MLST) of the isolates were determined. The spectra were analyzed for the selection of characteristic peaks by using the ClinProTools software. Furthermore, various machine learning (ML) algorithms were used to generate binary and multiclass models for classifying the major MLST types (ST5, ST59, and ST239) of MRSA.

Results

A total of 10 peaks with the highest discriminatory power (m/z range: 2,082–6,594) were identified and evaluated. All the single peaks revealed significant discriminatory power during MLST typing. Moreover, the binary and multiclass ML models achieved sufficient accuracy (82.80–94.40% for binary models and >81.00% for multiclass models) in classifying the major MLST types.

Conclusions

A combination of MALDI-TOF MS analysis and ML models is a potentially accurate, objective, and efficient tool for infection control and outbreak investigation.

Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus among nasal carriage strains isolated from emergency department patients and healthcare workers in central Taiwan

BACKGROUND AND OBJECTIVE

Screening and identification of methicillin-resistant Staphylococcus aureus (MRSA) carriage are helpful for controlling MRSA dissemination in hospitals. The aim of our study was to determine the prevalence of nasal carriages and diversity of MRSA among patients and healthcare workers (HCWs) at two regional hospitals in Taiwan.

METHODS

Nasal swabs were obtained prospectively from 204 patients visiting the emergency department (ED) and 326 HCWs in two regional hospitals in Changhua, Taiwan, between February 2015 and June 2015. All the MRSA isolates were further molecularly characterized.

RESULTS

Of the 204 participating patients, the nasal carriage rates of S. aureus and MRSA were 22.1% and 7.8%, respectively. For HCWs, the S. aureus and MRSA carriage rates were 26.1% and 6.1%, respectively. There was no statistically significant difference in MRSA carriage rate between patients and HCWs (P = 0.447). Patients receiving hemodialysis were significantly associated with MRSA colonization (P = 0.012). The leading three sequence types (ST) were ST59 (16, 44.4%), ST45 (11, 30.6%), and ST239 (3, 8.3%) for all 36 MRSA isolates. ST59/SCCmec IV/t437/PVL-negative and ST45/SCCmec V/t1081/PVL-negative were the predominant clones among HCWs (30%) and participating patients (19%), respectively.

CONCLUSION

Overall, a substantial proportion of patients visiting the ED and HCWs harbored CA-MRSA, mostly ST59 strains, in their nares. It is noteworthy that MRSA ST45 strains supplanted ST239 as the second leading nasal MRSA colonization strain in our study.

Molecular Characteristics of Community-Associated Staphylococcus aureus Isolates From Pediatric Patients With Bloodstream Infections Between 2012 and 2017 in Shanghai, China

Staphylococcus aureus is known as an invasive human pathogen, resulting in significant morbidity and mortality worldwide; however, information on community-associated S. aureus (CA-SA) from bloodstream infections (BSI) in children in China remains scarce. This study aimed to investigate the molecular characteristics of 78 CA-SA isolates recovered from pediatric patients with BSI between 2012 and 2017 in Shanghai. All isolates including 51 (65.4%) methicillin-susceptible S. aureus (MSSA) and 27 (34.6%) methicillin-resistant S. aureus (MRSA) isolates were characterized based on antimicrobial resistance, virulence genes, multilocus sequence typing (MLST), spa, and SCCmec typing. A total of 18 distinct sequence types (STs) and 44 spa types were identified. ST188 and ST7 were the predominant MSSA clones and ST59-MRSA-SCCmecIV/V was the most common MRSA clone. Spa t189 (9.0%, 7/78) was the most common spa type. SCCmec types IV and V were observed at frequencies of 59.3 and 40.7%, respectively. Notably, 40 (51.3%) S. aureus BSI strains were multidrug resistant (MDR), and these were mostly resistant to penicillin, erythromycin, and clindamycin. MRSA strains were associated with substantially higher rates of resistance to multiple antibiotics than MSSA strains. Fifty (64.1%, 50/78) isolates, including 19 (70.3%) MRSA isolates, harbored ≥ 10 tested virulence genes, as evaluated in this study. Ten (37.0%) MRSA isolates and four (7.8%) MSSA isolates harbored the gene encoding Panton-Valentine leukocidin (PVL). Virulence genes analysis showed diversity in different clones; the seb-sek-seq genes were present in all ST59 strains, whereas the seg-sei-sem-sen-seo genes were present in different clones including ST5, ST20, ST22, ST25, ST26, ST30, ST121, and ST487 strains. In conclusion, this study revealed that community-associated S. aureus strains from BSI in children demonstrated considerable genetic diversity, and identified major genotypes of CA-MRSA and CA-MSSA, with a high prevalence of CA-MRSA. Furthermore, major genotypes were frequently associated with specific antimicrobial resistance and toxin gene profiles. Understanding the molecular characteristics of those strains might provide further insights regarding the spread of BSI S. aureus among children between communities in China.

The clinical significance of silent mutations with respect to ciprofloxacin resistance in MRSA

Background

The aim of this study was to investigate the genotypic differences between different sequence type MRSA isolates, especially focusing on silent rpoB474 mutations and the relationship between such mutations and ciprofloxacin resistance.

Methods

Seventy-nine MRSA isolates were obtained for antibiotic susceptibility tests and molecular study.

Results

Among these isolates, we found that the MIC₅₀, MIC₉₀, and minimum inhibitory concentration (MIC) range of ciprofloxacin were much higher for the isolates without the rpoB474 mutation than for isolates with the rpoB474 mutation. A total of 87.5% of the isolates with the rpoB474 mutation were susceptible to ciprofloxacin, but none of the isolates without the rpoB474 mutation were susceptible to ciprofloxacin. For 27 MRSA isolates without rpo474 silent mutation but with gyrA86/126 silent mutation, all of them belonged to SCCmec III, and had high ciprofloxacin MIC levels. For another 44 MRSA isolates with rpo474 silent mutation but without gyrA86/126 silent mutation, all of them showed low ciprofloxacin MIC levels, all of them belonged to either SCCmec IV or V. Furthermore, MRSA ciprofloxacin resistance was found to be associated with the mutations gyrA S84L/parC S80F or gyrA S84L, and S85P/parC S80Y.

Conclusion

Most occurrences of this rpoB474 silent mutation were found in community acquired-MRSA (CA-MRSA) isolates with susceptibility to most antibiotics, especially for ciprofloxacin and vice versa. Thus, this mutation may help to differentiate the different microbiologic characteristics of MRSA clinical isolates.

Emergence, transmission and phylogeny of meticillin-resistant Staphylococcus aureus sequence type 8 (USA300) in Taiwan

Twenty-seven (0.51%) USA300 isolates were identified from a pool of 5308 meticillin-resistant Staphylococcus aureus (MRSA) isolates collected in Taiwan between 1995 and October 2015, including 12 infecting isolates from 10 patients. The first two isolates were identified in 2005, and 23 isolates have been collected since 2010. Phylogenetic analysis revealed that all the local isolates were closely related to those in North America, and there was a clade consisting of 13 local isolates from 10 patients. MRSA USA300 existed in Taiwan in 2005 or earlier, with increasing identification since 2010. Local transmission of USA300 has occurred in Taiwan after importation from North America.

Nasal methicillin-resistant Staphylococcus aureus colonization among otherwise healthy children aged between 2 months and 5 years in northern Taiwan, 2005-2010

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have been increasingly reported worldwide and are associated with nasal colonization. In Taiwan, available data disclosed a similar trend. We conducted a study for the updated childhood nasal MRSA carriage.

METHODS

From July 2005 to December 2010, children aged between 2 months and 5 years who presented for a well-child health care visit to a medical center or from kindergarten/daycare center were invited and a nasal swab specimen was obtained for the detection of MRSA. All MRSA isolates were characterized.

RESULTS

A total of 3226 children were included and the rate of nasal MRSA carriage was 10.2%. Children aged 2-6 months and >3 years were significantly associated with MRSA carriage, while pneumococcus colonization (p = 0.033) and breastfeeding (p = 0.025) were negatively associated with MRSA carriage. Of the 330 MRSA isolates, a total of 13 pulsotypes with two major patterns (type C, 47.0% and D, 29%) were identified. Most MRSA isolates belonged to two major clones, characterized as sequence type 59 (ST59)/pulsotype C/staphylococcal cassette chromosome (SCCmec) IV/Panton-Valentine leukocidin (PVL)-negative (45.8%) and ST59/pulsotype D/SCCmec V_T/PVL-positive (22.7%). Two new clones as ST 508/SCCmec IV (9.7%) and ST573/SCCmec IV (7.3%) emerged and increased markedly since 2007.

CONCLUSION

Between 2005 and 2010, 10.2% of healthy children in northern Taiwan carried MRSA in anterior nares, with the highest carriage rate for infants aged 2-6 months. Two emerging clones, ST 508 and ST 573, were identified and the clinical significance needs further surveillance.

Clinical features and molecular characteristics of childhood community-associated methicillin-resistant Staphylococcus aureus infection in a medical center in northern Taiwan, 2012

Background

Since first reported in 2002, the rate of methicillin-resistant Staphylococcus aureus (MRSA) among childhood community-associated (CA) S. aureus infection in Taiwan increased significantly up to 2005. There have been no reports on this issue since then.

Methods

We prospectively collected clinical S. aureus isolates from the patients <19 years of age in a university-affiliated hospital in 2012. Only first isolate from each patient was included. The medical records were retrospectively reviewed and the patients were classified as CA or healthcare-associated (HA) by the standard epidemiologic criteria. Isolates as CA-MRSA were further characterized by pulsed-field gel electrophoresis, staphylococcal cassette chromosome (SCCmec) typing, and multilocus sequence typing.

Results

A total of 409 S. aureus isolates were included, and 260 (63.6%) were MRSA. The proportion of MRSA among all S. aureus isolates in 2012 increased significantly (p < 0.001) compared to that in 2004–2005. Of the 181 CA-MRSA isolates, 86.2% were identified from pus or wound. Nine pulsotypes were identified with two major types (type D, 119 (65.7%); type C, 27 (14.9%). Most of the isolates carried either SCCmec IV (66 isolates, 36%) or V_T (112 isolates, 62%). 128 isolates (71%) carried Panton-Valentine leukocidin (PVL) genes. Clonal complex (CC) 59 accounted for 146 isolates (80.7%) of two major pulsotypes, CC45 for 19 isolates, ST30 for 6 isolates and ST8 (USA 300) for 4 isolates. In addition to penicillin (100%), most isolates were resistant to erythromycin (81%) and clindamycin (79.3%).

Conclusions

Around two-thirds of childhood community-associated S. aureus infections in northern Taiwan were MRSA. Though CC59 is still the prevalent community clone, several new clones emerged in northern Taiwan.

Persistent nasal carriers of Acinetobacter baumannii in long-term-care facilities

BACKGROUND

Acinetobacter baumannii and Staphylococcus aureus have persisted as 2 major pathogens worldwide.

AIM

We designed a prevalence study to investigate the prevalence of nasal carriage of S aureus and A baumannii in long-term-care facilities (LCTFs) and their collaborative community hospitals. In addition, we aimed to clarify persistent or nonpersistent carriage of the 2 organisms among residents of LTCFs.

METHODS

We performed a prevalence study concerning nasal carriers of A baumannii and S aureus in 3 LTCFs and 1 collaborative community hospital.

RESULTS

Seventy subjects were enrolled and clustered into 3 groups: the elderly sick group (n = 24), the elderly healthy group (n = 33), and the healthy health care worker group (n = 13). Nasal samples were collected, and the nuc and mecA genes of S aureus and the bla_OXA gene of A baumannii were analyzed by polymerase chain reaction. Among the 3 groups, the rate of nasal carriage of S aureus was approximately 0%-15%. However, the rate for A baumannii was approximately 54%-92%. Notably, the persistent carrier rate of A baumannii in the elderly sick group was 83.3% (20 out of 24) despite a 12.5% (3 out of 24) rate of carbapenem-resistant A baumannii.

CONCLUSIONS

We emphasized that the persistent nasal carriage of A baumannii in LTCFs could be another portal of exit to cause A baumannii infection in Taiwan.

Nasal Staphylococcus aureus and methicillin-resistant Staphylococcus aureus carriage among college student athletes in northern Taiwan

Of 259 college students in northern Taiwan surveyed, nasal carriage rate of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) was 22.4% and 1.54%, respectively and no significant difference was found between athlete students and non-athlete students. Three of four MRSA isolates belonged to sequence type 59, the endemic community clone.

Prevalence of and risk factors for nasal methicillin-resistant Staphylococcus aureus colonization among children in central Taiwan

BACKGROUND/PURPOSE

Staphylococcus aureus (S. aureus) causes diseases ranging from mild skin infections to invasive diseases. Carriage of S. aureus, including methicillin-resistant S. aureus (MRSA), is a significant risk factor for subsequent staphylococcal infection. Several studies discussed MRSA colonization in Taiwan, but mostly in northern Taiwan. This is the first study that estimates the prevalence of MRSA nasal colonization in healthy children and identifies the potential risk factors in central Taiwan.

METHODS

A total of 3144 healthy children aged 2-60 months who visited Taichung Veterans General Hospital (TCVGH) were screened for nasal S. aureus carriage from July 2005 to December 2010. Questionnaires included demographic information and potential risk factors for carriage of S. aureus were completed by parents/guardians.

RESULTS

Prevalence of MSSA and MRSA were 12.09% and 5.25%, respectively. The youngest group aged 2-6 months had the highest S. aureus carriage rate, and the carriage rate revealed a peak in summer. The nasal colonization of Streptococcus pneumoniae (S. pneumoniae) was a protective factor against S. aureus colonization. 85% of the MRSA colonizing isolates belonged to clonal complex 59/staphylococcal cassette chromosome type IV or V_T, the local community clone in Taiwan.

CONCLUSION

An increasing trend of MRSA nasal carriage rate in Taiwan had been brought forward, however, it was not observed in central Taiwan during the period of 2005-2010. We found a summer peak on both MRSA and MSSA carriages.

Nasal colonization and bacterial contamination of mobile phones carried by medical staff in the operating room

Background

Mobile phones (MPs) have been an essential part of the lives of healthcare professionals and have improved communication, collaboration, and sharing of information. Nonetheless, the widespread use of MPs in hospitals has raised concerns of nosocomial infections, especially in areas requiring the highest hygienic standards such as operating rooms (ORs). This study evaluated the incidence of bacterial contamination of the MPs carried by medical staff working in the OR and determined its association with bacterial colonization of this personnel.

Methods

This is an observational cohort study. Medical staffs working in the OR were asked to take bacterial cultures from their MPs, anterior nares, and dominant hands. To identify the relation between MP contamination and bacterial colonization of the medical staff, genotyping of Staphylococcus aureus (SA) was done via Staphylococcus protein A gene (spa) typing and pulsed-field gel electrophoresis (PFGE).

Results

A total of 216 swab samples taken from 72 medical-staff members were analyzed. The culture-positive rate was 98.1% (212/216). In 59 (27.3%) samples, the bacteria were possible clinical pathogens. The anterior nares were the most common site of colonization by clinical pathogens (58.3%, 42/72), followed by MPs (13.9%, 10/72) and the dominant hand (9.7%, 7/72). SA was the most commonly isolated clinical pathogen and was found in 43 (19.9%) samples. In 66 (94.3%) of the 70 staff members for whom bacteria were detected on their MPs, the same bacteria were detected in nares or hand. Among 31 medical staff who were carriers of SA in the anterior nares or dominant hand, 8 (25.8%) were found to have SA on their MPs, and genotyping confirmed the same SA strain in 7 (87.5%) of them.

Conclusion

A high rate of bacterial nasal colonization and MPs contamination were found among the OR medical staff. An MP may be a reservoir for pathogen contamination in the OR.

Nucleotide Sequence Variations in Autolysis Genes of ST59 Methicillin-Resistant Staphylococcus aureus Isolates

Biofilm formation is a virulence factor of bacteria. The goal of this study was to understand the mechanisms of biofilm formation by methicillin-resistant Staphylococcus aureus (MRSA). Whole-genome sequencing of eight MRSA strains was performed to identify sequence variations in genes related to biofilm formation. Thirty-one genes involved in MRSA biofilm formation were analyzed and 11 amino acid sequence variations in four genes related to autolysis were found. These variations include E121D and H387 N in ArlS; Q117K, T424S, K428T, A509S, V752E, A754V, and T771A in Atl; T184K in CidC; and D251N in CidR. Among the 26 clinical MRSA isolates studied, 13 isolates were nonbiofilm producers and were found to harbor these mutations. Furthermore, all of these 13 isolates belonged to ST59. Ten of these 13 ST59 isolates became able to produce biofilms when they were incubated with extracellular DNA from MRSA N315. Results of this study suggest that sequence variations in arlS, atl, cidC, and cidR genes may render MRSA unable to produce biofilms. Further investigations are needed to correlate these sequence variations with the biofilm-forming ability of MRSA isolates.

Antimicrobial Resistance and Molecular Characterization of Staphylococcus aureus Causing Childhood Pneumonia in Shanghai

Staphylococcus aureus or methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen causing pneumonia among children. To estimate the prevalence and molecular properties of S. aureus in children pneumonia in Shanghai, China, 107 hospitalized children with S. aureus pneumonia from two children's hospitals from January 2014 through June 2015 were studied. S. aureus isolates from the respiratory specimens were characterized by antimicrobial susceptibility, agr typing, toxin genes, multilocus sequence typing (MLST), spa, and SCCmec typing. Fifty-eight (54.2%, 58/107) were MSSA (methicillin-susceptible Staphylococcus aureus) and 49 (45.8%, 49/107) were MRSA. No isolates were found resistant to teicoplanin, sulfamethoxazole/trimethoprim, rifampicin, quinupristin/dalfopristin, linezolid, or vancomycin. However, these isolates showed high resistant rates to erythromycin, fosfomycin-trometamol and clindamycin. The agrI (87/107, 81.3%) was the most common agr allele, followed by agrIII(10/107, 9.3%), agrII(9/107, 8.4%), and agrIV(1/107, 0.9%). Six pvl-positive isolates (3 MRSA and 3 MSSA) and 7 isolates of livestock associated clone ST398 (4 MRSA, 3 MSSA) were identified. CC59 was found in 35 isolates (33 MRSA and 2 MSSA), constituting majority of MRSA (33/49, 67.35%). The dominant CC were CC59 (32.7%), CC188 (13.1%), CC7 (12.1%) and CC398 (9.3%) while t172 (16.8%), t189 (12.1%), t437 (9.3%), and t091 (9.3%) were the most common spa types. In conclusion, more particular concern should appeal to ST59-SCCmecIV-t172/t437 as it is the most common epidemic clone causing pneumonia among children in Shanghai.

Antimicrobial Resistance and Molecular Characteristics of Methicillin-Resistant Staphylococcus aureus Isolates from Child Patients of High-Risk Wards in Shenzhen, China

Methicillin-resistant Staphylococcus aureus (MRSA) strains are responsible for high rates of mortality and thus pose a substantial burden to public health worldwide. Here, we investigated the antimicrobial susceptibility and molecular characteristics of MRSA isolated from child patients at Shenzhen Children's Hospital. We characterized 140 MRSA strains through antimicrobial susceptibility testing. We further performed spa typing, multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) analysis, pvl gene analysis, and pulsed-field gel electrophoresis (PFGE). The analyzed MRSA strains were found to be sensitive to most non-β-lactam antimicrobial agents. Sequence type (ST) 59 was found to be the most common MLST lineage (54.3%). Most MRSA isolates belonged to the SCCmec IV (64.3%) and V (22.8%) types. The MRSA-ST59-SCCmec IV-t437 clone was the most predominant strain that infected 28.6% of all patients studied. Moreover, 50.7% of MRSA isolates were found to be pvl-positive. We report preliminary data on the prevalence and distribution of MRSA genotypes in Shenzhen Children's Hospital. We characterized MRSA colonization dynamics in child patients in China, and our findings can serve as the basis for the development of strategies to prevent MRSA infection and transmission.

Longitudinal investigation of nasopharyngeal methicillin-resistant Staphylococcus aureus colonization in early infancy: The PATCH birth cohort study

OBJECTIVES

The study aimed to determine the long-term Staphylococcus aureus colonization patterns and strain relatedness, and the association between maternal and infant colonization in infancy.

METHODS

A birth cohort study was conducted from January 2012 to November 2014. Nasopharyngeal swabs for S. aureus detection were collected from infants at the age of 1, 2, 4, 6 and 12 months and from mothers when their children were 1-month-old.

RESULTS

In total, 254 samples were collected at each planned visit during the first 12-month study. The prevalence of S. aureus colonization decreased in the first year of life, ranging from 61.0% (155/254) at the age of 1 month to 12.2% (31/254) at 12 months. Persistent colonization, defined as a positive culture on four or five occasions, was detected in only 13.8% (35/254) of carriers. Most of the persistent carriers were colonized with methicillin-resistant S. aureus (MRSA) only, and among persistent MRSA carriers, 61.1% (11/18) had indistinguishable genotypes. Of the mothers with MRSA colonization, 77.1% (27/35) had infants who were concomitantly colonized at the age of 1 month; 70.4% (19/27) of the infant-mother paired isolates belonged to indistinguishable or related subtypes, which suggests that surrounding carriers, probably their mothers, may be the possible source for MRSA acquisition in early infancy.

CONCLUSIONS

Staphylococcus aureus colonization including MRSA was commonly observed in our cohort. Strains of persistent MRSA among infant-mother pairs were usually of indistinguishable genotypes. Therefore, horizontal spread within households is possibly an important factor related to infant MRSA colonization.

Molecular Evolutionary Pathways toward Two Successful Community-Associated but Multidrug-Resistant ST59 Methicillin-Resistant Staphylococcus aureus Lineages in Taiwan: Dynamic Modes of Mobile Genetic Element Salvages

Clonal complex 59 (CC59) Staphylococcus aureus in Taiwan includes both methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). As the most prominent community-associated MRSA (CA-MRSA) in Taiwan, CC59 has two major clones characterized as PVL-negative SCCmec IV (carrying the staphylococcal cassette chromosome mec IV but Panton-Valentine leukocidin-negative) and PVL-positive SCCmec V (5C2&5). We investigated the drug resistance, phylogeny and the distribution and sequence variation of SCCmec, staphylococcal bacteriophage φSA3, genomic island νSaβ and MES (an enterococcal mobile genetic element conferring multidrug resistance) in 195 CC59 S. aureus. Sequencing and PCR mapping revealed that all of the CC59/SCCmec V (5C2&5) MRSA strains had acquired MES_PM1 or its segregants, and obtained a φSA3-related fragment in νSaβ. In contrast, MES_6272-2 and MES₄₅₇₈, which showed gentamicin resistance that was not encoded by MES_PM1, were dominant in SCCmec IVg MRSA. Translocation of a whole φSA3 into νSaβ instead of only a φSA3-related fragment was common in SCCmec IVg MRSA. However, the non-subtype-g SCCmec IV MRSA (SCCmec IVa is the major) still carried MES and νSaβ structures similar to those in SCCmec V (5C2&5) MRSA. A minimum spanning tree constructed by multiple-locus variable-number tandem repeat analysis revealed that SCCmec IVg MRSA and SCCmec V (5C2&5) MRSA grouped respectively in two major clades. The CC59 MSSA was equally distributed among the two clades, while the non-subtype-g SCCmec IV MRSA mostly clustered with SCCmec V (5C2&5) MRSA. Our findings strongly suggest that CC59 MSSA acquired divergent mobile genetic elements and evolved to SCCmec IVg MRSA and SCCmec V (5C2&5) MRSA/non-subtype-g SCCmec IV MRSA independently. The evolutionary history of CC59 S. aureus explains how mobile genetic elements increase the antimicrobial resistance and virulence and contribute to the success of CA-MRSA in Taiwan.

Identification of source and sink populations for the emergence and global spread of the East-Asia clone of community-associated MRSA

BACKGROUND

Our understanding of the factors influencing the emergence, dissemination and global distribution of epidemic clones of bacteria is limited. ST59 is a major epidemic clone of community-associated MRSA in East Asia, responsible for extensive morbidity and mortality, but has a much lower prevalence in other parts of the world. The geographic origin of ST59 and its international routes of dissemination are unclear and disputed in the literature.

RESULTS

To investigate the origin and spread of the ST59 clone, we obtained whole genome sequences of isolates from four continents, sampled over more than a decade, and carried out a time-scaled phylogeographic analysis. We discover that two distinct ST59 clades emerged concurrently, in East Asia and the USA, but underwent clonal expansion at different times. The East Asia clade was strongly enriched for gene determinants associated with antibiotic resistance, consistent with regional differences in antibiotic usage. Both clones spread independently to Australia and Europe, and we found evidence of the persistence of multi-drug resistance following export from East Asia. Direct transfer of strains between Taiwan and the USA was not observed in either direction, consistent with geographic niche exclusion.

CONCLUSIONS

Our results resolve a longstanding controversy regarding the origin of the ST59 clone, revealing the major global source and sink populations and routes for the spread of multi-drug resistant clones. Additionally, our findings indicate that diversification of the accessory genome of epidemic clones partly reflects region-specific patterns of antibiotic usage, which may influence bacterial fitness after transmission to different geographic locations.

Musculoskeletal Sepsis Associated with Deep Vein Thrombosis in a Child

Deep vein thrombosis (DVT) is a rare disease in pediatric patients. We report a pediatric patient who developed DVT in association with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia complicated with septic arthritis, osteomyelitis, and myositis extensively. It is crucial to consider musculoskeletal infection associated with DVT in any child who presents with severe swollen limbs and limitations of motion. Prompt antibiotic and anticoagulant treatments should be initiated to reduce the risk of fatal complications.

Molecular characteristics of community-acquired methicillin-resistant Staphylococcus aureus strains isolated from outpatients with skin and soft tissue infections in Wuhan, China

This study aims to investigate the antimicrobial susceptibility, molecular characteristics and virulence genes of community-acquired methicillin-resistant ITALIC! Staphylococcus aureus(CA-MRSA) isolates with skin and soft tissue infections (SSTIs). Outpatients with SSTIs visiting five medical and health institutions were enrolled from 2011 to 2013. Available ITALIC! S. aureus isolates were characterized by antimicrobial susceptibility testing, and detection of PVL genes. For CA-MRSA isolates, we performed typing of staphylococcal cassette chromosome ITALIC! mec(SCC ITALIC! mec), multi locus sequence typing (MLST) and carriage of 27 virulence genes. A total of 203 ITALIC! S. aureusstrains were isolated from 1400 outpatients with SSTIs, and 21 (10.3%) were CA-MRSA isolates. The positive rate of PVL genes among ITALIC! S. aureus, CA-MRSA and methicillin-susceptible ITALIC! S. aureus(MSSA) isolates were 39.4%, 71.4% and 35.7%, respectively. CA-MRSA strains had greater sensitivity to non-β-lactam antimicrobial agents. All CA-MRSA isolates belonged to SCC ITALIC! mecIV and V, accounting for 47.6% and 52.4%, respectively. ST59 was the most common lineage accounting for 76.2%; ST59-SCC ITALIC! mecIVa-PVL-positive clone was found to be the predominant clone, accounting for 38.1%. All CA-MRSA isolates were found to be positive for one or more virulence genes, 28.6% of isolates carried PVL, ITALIC! seb, ITALIC! sek, ITALIC! seq, ITALIC! hla, ITALIC! hlb, ITALIC! hldand ITALIC! hlg-2. CA-MRSA infections were relatively uncommon in outpatients with SSTIs, but they carried many virulence genes, ST59-SCC ITALIC! mecIV a-PVL-positive clone was the predominant clone in Wuhan, China.

Comparative Molecular Characteristics of Community-Associated and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Isolates From Adult Patients in Northern Taiwan

Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen in hospitals, and increases rapidly in the community, named as community-associated MRSA (CA-MRSA). We conducted a prospective/retrospective study to understand the epidemiology, antimicrobial susceptibility, and molecular characteristics of MRSA infections in adult patients in Taiwan.From March to June, 2012, all clinical MRSA isolates were prospectively collected from adult patients in a tertiary hospital in northern Taiwan. Selective isolates were further characterized. We reviewed the detailed medical record of each case retrospectively.A total of 857 clinical isolates were collected from 555 patients. A total of 749 isolates from 453 patients were classified as healthcare-associated (HA)-MRSA and 108 isolates from 102 patients as CA-MRSA by the epidemiologic criteria. Compared to HA-MRSA, CA-MRSA isolates were significantly more frequently identified from pus (78% vs 28%, P < 0.001) and less frequently from sputum (4.6% vs 43.8%, P < 0.001) and blood (3.7% vs 15%, P = 0.002). CA-MRSA isolates were more susceptible to all antibiotics tested. A total of 102 CA-MRSA and 101 HA-MRSA isolates were characterized, showing significantly different molecular characteristics between CA and HA isolates (P < 0.001). The clone of sequence type (ST) 59/t437 complex, with 2 pulsotypes, accounted for 70% of CA isolates. Three major clones were identified from HA-MRSA isolates, namely clonal complex (CC) 59 (32.7%), CC239 (29.7%), and CC5 (24.8%). Among HA isolates, a significant difference was also seen between community-onset and hospital-onset MRSA isolates in terms of the source of specimens, antibiotic susceptibility patterns, and molecular characteristics.CA-MRSA isolates from adults in northern Taiwan were genetically significantly different from HA isolates. The community clones, CC59, spread into hospitals.

Methicillin-Resistant Staphylococcus aureus Ocular Infection in Taiwan: Clinical Features, Genotying, and Antibiotic Susceptibility

Methicillin-resistant Staphylococcus aureus (MRSA) infection is an important public health issue. This observational study aimed to characterize clinical features, antibiotic susceptibility, and genotypes of ocular infections caused by MRSA based on the clinical and molecular definitions of community-associated (CA) and healthcare-associated (HA) strains.Fifty-nine patients with culture-proven S aureus ocular infection were enrolled from January 1, 2010 to December 31, 2011 at Chang Gung Memorial Hospital, Taiwan. Antibiotic susceptibility was verified using disk diffusion/E test. For characterization, staphylococcal cassette chromosome mec (SCCmec), pulsed-field gel electrophoresis (PFGE), multilocus sequence type (MLST), and Panton-Valentine leukocidin (PVL) gene, were performed. MRSA isolates from the patients with HA factors were classified as clinically defined HA-MRSA, and those carrying SCCmec type I to III as molecularly defined HA-MRSA.Thirty-four patients with MRSA ocular infection were identified. The most common clone of CA-MRSA and HA-MRSA isolates was ST59/PFGE type D/SCCmec IV,VT/PVL (+) (n = 12) and CC 239/PFGE type A/SCCmec III, IIIA/PVL(-) (n = 10), respectively. All the 11 patients with molecularly defined HA-MRSA infections and 50% of the 22 patients with molecularly defined CA-MRSA infections were found to have HA factors (P = .005). CA-MRSA tended to cause lid infections, whereas HA-MRSA tended to cause corneal infections. Contrary to HA-MRSA isolates, nearly all the CA-MRSA isolates were susceptible to trimethoprim/sulfamethoxazole and fluoroquinolones under either clinical or molecular classifications.In Taiwan, CA-MRSA isolates exhibited considerably higher susceptibility to fluoroquinolones when compared with HA-MRSA isolates. A strong correlation was observed between the HA factors and molecularly defined HA-MRSA isolates.

Nasal Staphylococcus aureus and Methicillin-Resistant S. aureus Carriage among Janitors Working in Hospitals in Northern Taiwan

BACKGROUND

Staphylococcus aureus is an important cause of infection, and brings additional concern with methicillin resistance. In addition, nasal methicillin-resistant Staphylococcus aureus (MRSA) colonization rates among health care workers are higher than that for general population. To determine the prevalence rate and risk factors for the colonization of S. aureus, including MRSA, among janitors working in hospitals in northern Taiwan, we conducted this study.

METHODS

Between June and August, 2014, a total of 186 janitors, 111 working in hospitals and 75 working in non-medical institutions, were recruited. Specimens were obtained from the nares of the subjects for the detection of S. aureus, with a questionnaire completed for each subject. All the S. aureus isolates, including MRSA and methicillin-susceptible S. aureus (MSSA), were further molecularly characterized.

RESULTS

The nasal carriage rate of S. aureus was 15.3% for hospital janitors and 13.3% for non-medical janitors. The carriage rate of MRSA was 3.6% for hospital janitors and 1.3% for non-medical janitors. No statistically significant difference was found in the nasal carriage rate of S. aureus (p = 0.707) and MRSA (p = 0.65) between hospital janitors and non-medical janitors. Hospital janitors working in hospital more than 6 years and cleaning microbiologic laboratories were significantly associated with nasal S. aureus colonization. All 5 MRSA isolates carried either staphylococcal cassette chromosome type IV or V and three of them belonged to sequence type (ST) 59, the community clone prevailing in Taiwan. Of the 22 MSSA isolates, six pulsotypes were identified, with one major type for 14 isolates (shared by five STs) and another type for 4 isolates (all belonged to ST 188).

CONCLUSION

Exposure to the hospital environment may not increase the nasal carriage rate of S. aureus, including MRSA, among janitors in hospitals in Taiwan. However, for janitors in the hospital setting, working for more than six years in hospital and cleaning laboratories may be risks factors for carrying S. aureus.

Vancomycin dosing and target attainment in children

BACKGROUND/PURPOSE

The aim of this study is to determine the best dosing strategy for vancomycin by studying the associated factors and examining correlations between the area under the plasma concentration-time curve (AUC) values and trough concentrations in children.

METHODS

Children aged 3 months to 18 years were included if they received vancomycin for more than three doses between January 1, 2010 and December 31, 2012 and had one or more serum vancomycin trough concentrations. Vancomycin clearance (CL) was calculated using the following model: CL = 0.248*Wt^0.75*(0.48/serum creatinine)^0.361*[ln (age)/7.8]^0.995. The AUC (mg-h/L) was calculated by 24-hour dose (mg/kg/d)/CL(L/h). The value of AUC divided by the minimum inhibitory concentration (MIC) of vancomycin was AUC/MIC.

RESULTS

A total of 218 children were included. The mean age was 6.0 ± 5.1 years and the mean body weight was 20 ± 11.7 kg. Vancomycin trough concentrations were moderately correlated with AUC values (r² = 0.232, p < 0.01). Dosing of 15 mg/kg/dose q6h produced significantly higher AUC values (p < 0.001) and vancomycin trough concentrations (p < 0.001) compared to dosing of 10 mg/kg/dose q6h. In children receiving a 10-mg/kg/dose q6h, 5.6% (5/90) achieved the target trough concentrations of 15-20 μg/mL and 9.5% (5/90) achieved the goal AUC/MIC ≥ 400. In children receiving a 15-mg/kg/dose q6h, 13% (6/46) achieved the target trough concentrations of 15-20 μg/mL, whereas 54.3% (25/46) achieved the goal AUC/MIC ≥ 400.

CONCLUSION

A 15-mg/kg/dose q6h compared to a 10-mg/kg/dose q6h is more likely to achieve target trough concentrations of 15-20 μg/mL and the goal AUC/MIC ≥ 400.

Clinical and microbiological characteristics of purulent and non-purulent cellulitis in hospitalized Taiwanese adults in the era of community-associated methicillin-resistant Staphylococcus aureus

BACKGROUND

The risk factors, microbial etiology, differentiation, and clinical features of purulent and non-purulent cellulitis are not well defined in Taiwan.

METHODS

We conducted a retrospective cohort study of hospitalized adults with cellulitis in Taiwan in 2013. The demographic characteristics, underlying diseases, clinical manifestations, laboratory and microbiological findings, treatments, and outcomes were compared for patients with purulent and non-purulent cellulitis.

RESULTS

Of the 465 patients, 369 had non-purulent cellulitis and 96 had purulent cellulitis. The non-purulent group was significantly older (p = 0.001) and was more likely to have lower limb involvement (p < 0.001), tinea pedis (p = 0.003), stasis dermatitis (p = 0.025), a higher Charlson comorbidity score (p = 0.03), and recurrence at 6 months post-infection (p = 0.001) than the purulent group. The purulent group was more likely to have a wound (p < 0.001) and a longer hospital stay (p = 0.001) and duration of antimicrobial therapy (p = 0.003) than the non-purulent group. The etiological agent was identified in 35.5 % of the non-purulent cases, with β-hemolytic streptococci the most frequent cause (70.2 %). The etiological agent was identified in 83.3 % of the purulent cases, with Staphylococcus aureus the predominant pathogen (60 %): 50 % of these were methicillin-resistant S. aureus (MRSA). In multivariable analysis, purulent group (odds ratio (OR), 5.188; 95 % confidence interval (CI), 1.995-13.493; p = 0.001) was a positive predictor of MRSA. The prescribed antimicrobial agents were significantly different between the purulent and non-purulent groups, with penicillin the most frequently used antimicrobial agent in the non-purulent group (35.2 %), and oxacillin the most frequent in the purulent group (39.6 %). The appropriate antimicrobial agent was more frequently prescribed in the non-purulent group than in the purulent group (83.2 % vs. 53.8 %, p < 0.001).

CONCLUSIONS

The epidemiology, clinical features, and microbiology of purulent and non-purulent cellulitis were significantly different in hospitalized Taiwanese adults. Purulence was a positive predictor of MRSA as the causal agent of cellulitis. These findings provide added support for the adoption of the IDSA guidelines for empirical antimicrobial therapy of cellulitis in Taiwan.