Microbiological and molecular epidemiological analyses of community-associated methicillin-resistant Staphylococcus aureus at a tertiary care hospital in Japan

Impact of control measures including decolonization and hand hygiene for orthopaedic surgical site infection caused by MRSA at a Japanese tertiary-care hospital

BACKGROUND

Meticillin-resistant Staphylococcus aureus (MRSA) is the most common pathogen in orthopaedic surgical site infections (SSIs). However, few studies have investigated the transmission process of orthopaedic MRSA SSI.

AIM

To investigate the transmission process of orthopaedic MRSA SSI using epidemiological and molecular analyses and to determine a method to prevent MRSA SSI in nosocomial orthopaedic surgery.

METHODS

Active MRSA surveillance, preoperative decolonization and contact precautions for MRSA-positive cases was performed at our institution. Changes in epidemic strains were evaluated and the possibility of transmission from patients in an orthopaedic ward of a Japanese tertiary-care hospital was assessed by genotyping stored MRSA strains. In addition, data on the prevalence of MRSA SSI, MRSA colonization, and use of an alcohol antiseptic agent (mL/patient-days) during 2005-2022 were retrospectively assessed.

FINDINGS

SCCmec type II strain in the SSI group decreased over time, associated with fewer outbreaks. Even during a period of high infection rates, no cases of transmission-induced SSI from nasal MRSA carriers were identified. The infection rate correlated negatively with the use of an alcohol antiseptic agent (r = -0.82; P < 0.0001). Two cases among five nasal carriers developed MRSA SSI caused by strains different from those related to nasal colonization.

CONCLUSION

The infection control measures for transmission from the hospital reservoirs including strict adherence to hand hygiene and decolonization of carriers is likely to be important for the prevention of orthopaedic MRSA SSI. However, the need for contact precautions for decolonized nasal carriers might be low.

The clinical characteristics and molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) among very elderly people in Japan

AIM

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial infection-causing pathogen. The clonal shift from staphylococcal cassette chromosome mec (SCCmec) type II MRSA to SCCmec type IV MRSA has occurred rapidly in acute-care hospitals. However, the epidemiology and clinical impacts of MRSA in geriatric hospitals are poorly documented. We performed a molecular epidemiological analysis of the clinical isolates and retrospectively investigated the clinical characteristics of SCCmec type IV MRSA in elderly individuals.

METHODS

MRSA isolates were grouped according to the SCCmec type and virulence genes (tst, sea, seb, sec, and lukS/F-PV), and multi-locus sequence typing (MLST) was performed.

RESULTS

Of the 145 MRSA isolates obtained from patients with a median age of 85 years, 100 (69.0%) were obtained from sputum samples, 22 (15.2%) from skin and soft tissues, and seven (4.8%) from blood samples. The most prevalent clone was SCCmec type IV/clonal complex (CC)1/sea+ (59.3%), followed by SCCmec type I/sequence type (ST) 8 (17.3%). Of the 17 (11.7%) strains to which an anti-MRSA drug was administered by a physician, only three were SCCmec type IV/CC1/sea+ (17.6%) and five were SCCmec type I/ST8 (29.4%). SCCmec type IV/CC1/sea+ MRSA was more frequently isolated in long-term care wards than were SCCmec type I/ST8 strains (odds ratio: 2.85, 95% confidence interval: 1.08-7.54) and was less frequently treated as the cause of MRSA infections (odds ratio: 0.15, 95% confidence interval: 0.03-0.73).

CONCLUSIONS

SCCmec type IV/CC1/sea+ MRSA was the predominant clone and could be easily transmissible and be capable of colonization. Geriatr Gerontol Int 2023; 23: 744-749.

Estimated medical costs of methicillin-resistant Staphylococcus aureus infection classified by polymerase chain reaction-based open reading frame typing in Japan

This retrospective, observational cohort study investigated the economic impact of genotype by classifying methicillin-resistant Staphylococcus aureus (MRSA) by using the polymerase chain reaction-based open reading frame typing (POT) method. Using administrative claims and bacteriological data for April 2016 to March 2021 from the University of Yamanashi Hospital, we ascertained the POT1 numbers and classified MRSA as either "hospital-derived" or "community-derived". We defined MRSA-associated medical practices and estimated the associated medical costs. After applying inverse probability of treatment weighting (IPTW)-based adjustment for patient characteristics between the two groups, we estimated the differences in medical costs during the "total therapy period" (defined as the interval from specimen submission to Day 42 after the susceptibility report) and the "definitive therapy period" (defined as the interval from susceptibility reporting to Day 42). Among the 135 MRSA-infected patients, 54 and 81 were classified as having hospital-derived and community-derived MRSA infections, respectively. Significant differences in patient characteristics were observed with regard to age (p = 0.0478), sex (p = 0.0422), surgery (p = 0.0349), chemotherapy (p = 0.0457) and immunosuppressive drug use (p = 0.0222). The median duration of the definitive therapy was 29 and 27 days, and the mortality rate during this period was 11% and 5% for the hospital-derived and community-derived types, respectively. After IPTW-based adjustment, the medical costs for the total therapy period were 324,480 and 296,462 Japanese yen (JPY) per patient for the hospital-derived and community-derived types, respectively, whereas the medical costs for the definitive therapy period were 279,635 and 256,542 JPY per patient for the hospital-derived and community-derived types, respectively. No statistically significant difference was detected (p = 0.5813 and p = 0.6355, respectively). In this study, MRSA healthcare costs were compared according to the POT scores, and no statistically significant differences were observed between hospital-derived and community-derived MRSA infections.

Clinical characteristics and molecular analysis of USA300 and ST 764 methicillin-resistant Staphylococcus aureus isolates from outpatients in Japan by PCR-Based open reading frame typing

INTRODUCTION

USA300 is the most common community-acquired methicillin-resistant Staphylococcus aureus (MRSA) strain. Sequence type (ST) 764 MRSA is a new local variant of the ST 5 lineage. The objective of this study was to determine the clinical characteristics of USA300 and ST 764 infections among outpatients in Japan.

METHODS

We obtained MRSA isolates from 132 outpatients who visited our hospital from January 2016 to December 2017 and compared USA300 infection group to ST 764 infection group. Molecular analysis, including that of various toxins and other virulence factors, of the MRSA isolates were performed. In particular, we investigated the relationships among PCR-based open reading frame typing (POT) scores, MRSA clones, and virulence factors.

RESULTS

Twenty-seven USA300 isolates (20.5%) and 16 ST 764 isolates (12.1%) were identified. Although USA300 and ST 764 had lower rates of risk factors, their infection rates were higher. USA300-infected patients had higher rates of deep skin and soft tissue infections compared with the non-USA300 CA-MRSA-infected patients. Notably, the USA300 and ST 764 isolates had unique POT scores.

CONCLUSIONS

Our results indicated that USA300 MRSA was spreading in an area 120 km west of Tokyo, Japan. We observed multiple cases of ST 764 MRSA infection, raising concerns about the antimicrobial resistance of ST 764, as it limits the choices of antibiotics to treat infection. The POT score can predict the presence of toxins and virulence factors, as well as the clone identity of MRSA with high accuracy.

The increased frequency of methicillin-resistant Staphylococcus aureus with low MIC of beta-lactam antibiotics isolated from hospitalized patients

Methicillin-resistant Staphylococcus aureus (MRSA) causes severe infectious diseases and can be life-threatening in healthcare-settings. MRSA is classified into health-care associated (HA)-MRSA strains and community acquired (CA)-MRSA strains based on genotype and phenotype. CA-MRSA has been reported to show the lower minimal inhibitory concentration (MIC) of some antibiotics as compared to HA-MRSA. Recently, the prevalence of CA-MRSA has been increased in worldwide. CA-MRSA is isolated not only from the healthy individuals in a community but also from the patients in healthcare settings. However, the changing trend in frequency of HA-MRSA and CA-MRSA in the hospital setting is not clear. Therefore, we analyzed the trend of MIC to speculate the frequency of HA-MRSA and CA-MRSA in the facility. Moreover, gene mutations were evaluated on resistant gene loci with next generation sequencer. The frequency of strains with low MIC of beta-lactam antibiotics was gradually increased in isolated MRSA strains from the hospitalized patients. Whole genome analysis revealed the frequency of gene mutation was also decreased in some resistant loci, such as blaZ and blaR1. These findings highlight the changing trend of MRSA strains isolated from hospitalized patients.

Scrotal ulcer due to community-acquired methicillin-resistant Staphylococcus aureus USA300 clone in an HIV-positive man who has sex with men in Japan: a case report

A genital ulcer can be associated with sexually transmitted infections, such as syphilis and herpes, and sexually transmitted organisms, such as Chlamydia trachomatis. We report a case of scrotal ulcer caused by Staphylococcus aureus clone USA300 in a 56-year-old man living with human immunodeficiency virus in Osaka, Japan. It is important to enhance the awareness and surveillance regarding the potential of spread of this organism in the community of men who have sex with men in this district.

Prosthetic Valve Endocarditis Caused by ST8 SCCmecIVl Type Community-associated Methicillin-resistant Staphylococcus aureus

The emergence of a Japan-intrinsic community associated methicillin-resistant Staphylococcus aureus strain (CA-MRSA/J) has been reported. A 70-year-old man with recurrent colon cancer and a history of mitral valve replacement was admitted to the hospital in a state of shock. He was diagnosed with prosthetic valve endocarditis (PVE) caused by MRSA and underwent cardiac surgery. The MRSA isolates belonged to multilocus sequence type 8 and carried staphylococcal cassette chromosome mec IVl and the genes of toxic shock syndrome toxin-1, enterotoxin C, and enterotoxin L. These characteristics indicated a CA-MRSA/J clone. This is the first reported case of PVE caused by CA-MRSA/J.

Prevalence and Genetic Characteristics of Methicillin-Resistant Staphylococcus aureus and Coagulase-Negative Staphylococci Isolated from Oral Cavity of Healthy Children in Japan

Prevalence and genetic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci in oral cavity of healthy children were studied in Hokkaido, northern main island of Japan. From saliva of 526 children, a total of 248 staphylococcal isolates comprising S. aureus (n = 143), S. epidermidis (n = 84), S. warneri (n = 13), S. haemolyticus (n = 5), S. hominis (n = 2), and S. intermedius (n = 1) were recovered. Presence of mecA was confirmed in 6.3% of S. aureus, 50% of S. epidermidis, and 7.7% in S. warneri. SCCmec was mostly classified into type IV, and ACME (arginine catabolic mobile element)-arcA was detected in S. epidermidis (23.8%) and S. intermedius. Nine MRSA isolates belonged to staphylocoagulase gene (coa) type Ia, IIa, IIIa, VIIb/sequence type 1 (ST1), ST5, ST8, ST89, ST120, and were negative for PVL (Panton-Valentine leukocidin) genes. These isolates included two clones of emerging community-acquired MRSA (CA-MRSA) that had been described recently in Japan: ST5/SCCmec IVc, which resembles the "Pediatric clone," and ST8/SCCmec IVl belonging to coa-IIIa/agr-I with sasL gene, designated "CA-MRSA/J" clone. Various enterotoxin genes were found in all the MRSA and some methicillin-susceptible S. aureus (MSSA) isolates examined, while tst-1 was detected in four MRSA isolates. Notably, a variant of elastin-binding protein gene (ebpS-v) was identified in ST120 MRSA and ST45 MSSA isolates, and exfoliative toxin D gene (etd) was detected in an MSSA isolate. The present study revealed the presence of MRSA, including the novel CA-MRSA clones, and high prevalence of methicillin-resistant S. epidermidis in oral cavity of healthy children in Japan.

Molecular analysis, biofilm formation, and susceptibility of methicillin-resistant Staphylococcus aureus strains causing community- and health care-associated infections in central venous catheters

INTRODUCTION

The behavior of methicillin-resistant Staphylococcus aureus (MRSA) isolated from central venous catheter-related infection was evaluated to determine its biofilm potential, antimicrobial resistance, and adhesion genes.

METHODS

A total of 1,156 central venous catheters (CVC) were evaluated to screen for pathogens. Antimicrobial sensitivity, biofilm formation potential, and molecular analysis of MRSA were examined following standard guidelines.

RESULTS

Of the 1,156 samples, 882 (76%) were colonized by bacteria or candida. Among the infected patients, 69% were male and 36% were female with median age of 32 years. Staphylococcus aureus infected 39% (344/882) of CVCs in patients. Of the 59% (208/344) of patients with MRSA, 57% had community acquired MRSA and 43% had hospital acquired MRSA. Linezolid and vancomycin killed 100% of MRSA; resistance levels to fusidic acid, doxycycline, clindamycin, azithromycin, amikacin, trimethoprim-sulfamethoxazole, gentamycin, tobramycin, and ofloxacin were 21%, 42%, 66%, 68%, 72%, 85%, 95%, 97%, and 98% respectively. Strong biofilm was produced by 23% of samples, moderate by 27%, and weak by 50% of MRSA. The presence of adhesion genes, sdrC and sdrD (90%), eno (87%), fnbA (80%), clfA and sdrE (67%), fnbB, sdrD (61%), and cna (51%), in most MRSA samples suggested that the adhesion genes are associated with biofilm synthesis.

CONCLUSIONS

The superbug MRSA is a major cause of CVC-related infection. Antibiotic resistance to major classes of antibiotics and biofilm formation potential enhanced superbug MRSA virulence, leading to complicated infection. MRSA causes infection in hospitals, communities, and livestock.

Polymerase chain reaction-based open reading frame typing (POT) method analysis for a methicillin-resistant Staphylococcus aureus (MRSA) outbreak through breast-feeding in the neonatal intensive care unit

Introduction

The route of methicillin-resistant Staphylococcus aureus (MRSA) transmission in the neonatal intensive care unit (NICU) is not clearly explained. We investigate an MRSA outbreak involving five babies in the NICU. The molecular investigation using polymerase chain reaction-based open reading frame typing (POT) method was performed.

Presentation of outbreak

A MRSA outbreak occurred in a six-bed NICU affecting 5 babies. Within 13 days of the emergence of index case, all five babies including triplets and other two babies were found to colonize MRSA by the active surveillance culture. Environmental surveillance cultures revealed that the preserved breast milk provided by the triplets' mother was the only item in the NICU that was positive for MRSA. The mother had a bite wound on the nipples, and the breast milk was not pasteurized. The POT method revealed that MRSA strains detected from the triplets, the breast milk, and the other baby who was fed the triplets' mother's milk were genetically identical (POT index: 106-247-33). The all strains of MRSA carried Staphylococcal cassette chromosome mec (SCCmec) IV and had good susceptibility for the non-ß-lactam antimicrobial agents, suggesting the strains were community-acquired MRSA.

Conclusions

The mother’s milk contaminated with community-origin MRSA is serving as the reservoir of MRSA and one of the sources of MRSA outbreaks in the NICU. It is important to closely monitor the condition of the mothers of the children in the NICU. Pasteurization of breast milk should be considered when the skin on the nipple is broken.

Characterization of SCCmec type IV methicillin-resistant Staphylococcus aureus clones increased in Japanese hospitals

Recently, the prevalence of staphylococcal cassette chromosome mec (SCCmec) type IV isolates, which are the major community-acquired methicillin-resistant Staphylococcus aureus (MRSA), have increased in Japanese hospitals. The aim of this study was to elucidate the detailed molecular epidemiological features of the SCCmec type IV clones in Japanese hospitals. When 2589 MRSA isolated from four hospitals in Tokyo, Japan between 2010 and 2014 were analysed, the proportion of SCCmec type IV overtook that of type II, which was the major type of hospital-acquired MRSA in 2014. Multilocus sequence typing showed that CC1 was the most predominant clone in the SCCmec type IV isolates. The clinical departments that the patients belonged to, pulsed-field gel electrophoresis analysis and antimicrobial susceptibility profiles suggested that the origin of the CC1-SCCmec type IV (CC1-IV) clone was a community setting. Our data show that the CC1-IV clone is becoming a predominant MRSA clone in Japanese hospitals.

Persistent methicillin-resistant Staphylococcus aureus bacteremia owing to placental abscess

Staphylococcus aureus as a pathogen in human gestational membranes, a rather rare phenomenon, has recently been the focus of several researches. S. aureus forms biofilms on these membranes and potentially causes chorioamnionitis in pregnant women. We report a case of persistent methicillin-resistant S. aureus (MRSA) bacteremia owing to placental infection, causing chorioamnionitis and preterm birth. A 29-year-old Japanese woman at the 27th gestational week was diagnosed with acute promyelocytic leukemia and underwent all-trans retinoic acid therapy. Soon after hospitalization, the patient presented with persistent MRSA bacteremia of unknown origin. Despite various antimicrobial therapies, she experienced 12 MRSA bacteremia episodes over 6 weeks. However, after child birth, MRSA bacteremia disappeared without any complications. A pathologic examination of her placenta revealed placenta abscess, resulting in a diagnosis of MRSA-associated chorioamnionitis. Molecular analysis proved that a single MRSA strain (SCCmec Type IVa), which tested negative for Panton-Valentine leukocidin and toxic shock syndrome toxin-1, caused the obstinate infection. We should be aware that persistent MRSA bacteremia in pregnant women can originate from placental abscess.

Infection Prevention Strategy in Hospitals in the Era of Community-Associated Methicillin-Resistant Staphylococcus aureus in the Asia-Pacific Region: A Review

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as an important cause of healthcare-associated infection. CA-MRSA clones have replaced classic hospital MRSA clones in many countries and have shown higher potential in transmission and virulence than hospital MRSA clones. In particular, the emergence of CA-MRSA in the Asia-Pacific region is concerning owing to insufficient infection control measures in the region. The old strategies for infection prevention and control of MRSA comprised adherence to standard precaution and policy of active screening of MRSA carriers and decolonization, and it has been controversial which strategy is better in terms of outcome and cost-effectiveness. Epidemiological changes in MRSA has made the development of infection prevention strategy more complicated. Based on the literature review and the questionnaire survey, we considered infection prevention strategies for healthcare settings in the Asia-Pacific region in the era of CA-MRSA.

The changing face of community-acquired methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of infection, both in hospitalised patients with significant healthcare exposure and in patients without healthcare risk factors. Community-acquired methicillin-resistant S. aureus (CA-MRSA) are known for their rapid community transmission and propensity to cause aggressive skin and soft tissue infections and community-acquired pneumonia. The distinction between the healthcare-associated (HA)-MRSA and CA-MRSA is gradually fading owing to the acquisition of multiple virulence factors and genetic elements. The movement of CA-MRSA strains into the nosocomial setting limits the utility of using clinical risk factors alone to designate community or HA status. Identification of unique genetic characteristics and genotyping are valuable tools for MRSA epidemiological studies. Although the optimum pharmacotherapy for CA-MRSA infections has not been determined, many CA-MRSA strains remain broadly susceptible to several non-β-lactam antibacterial agents. This review aimed at illuminating the characteristic features of CA-MRSA, virulence factors, changing clinical settings and molecular epidemiology, insurgence into the hospital settings and therapy with drug resistance.

Rapid containment of nosocomial transmission of a rare community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone, responsible for the Staphylococcal Scalded Skin Syndrome (SSSS)

Background

The aims of this study were to identify the source and the transmission pathway for a Staphylococcal Scalded Skin Syndrome (SSSS) outbreak in a maternity setting in Italy over 2 months, during 2014; to implement appropriate control measures in order to prevent the epidemic spread within the maternity ward; and to identify the Methicillin-Resistant Staphylococcus aureus (MRSA) epidemic clone.

Methods

Epidemiological and microbiological investigations, based on phenotyping and genotyping methods, were performed. All neonates involved in the outbreak underwent clinical and microbiological investigations to detect the cause of illness. Parents and healthcare workers were screened for Staphylococcus aureus to identify asymptomatic carriers.

Results

The SSSS outbreak was due to the cross-transmission of a rare clone of ST5-CA-MRSA-SCCmecV-spa type t311, exfoliative toxin A-producer, isolated from three neonates, one mother (from her nose and from dermatological lesions due to pre-existing hand eczema) and from a nurse (colonized in her nose by this microorganism). The epidemiological and microbiological investigation confirmed these as two potential carriers.

Conclusions

A rapid containment of these infections was obtained only after implementation of robust swabbing of mothers and healthcare workers. The use of molecular methodologies for typing was able to identify all carriers and to trace the transmission.

Changing epidemiology of community-associated methicillin-resistant Staphylococcus aureus in the Asia-Pacific region

INTRODUCTION

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has become an important threat to public health in the Asia-Pacific region, which is characterized by a large population and relatively insufficient resources. Better understanding on the current status of CA-MRSA in the region is of paramount importance. Areas covered: This article reviews the published literatures on the prevalence, molecular epidemiology, colonization, and hospital spread of CA-MRSA. Expert commentary: The burden of CA-MRSA has been increasing in the past two decades. The molecular epidemiology of CA-MRSA in the Asia-Pacific region shows a marked diversity in each country. Still, some strains - multilocus sequence type (MLST) ST59, ST30, ST72, ST8, and ST772 - are unique clones that have successfully established themselves as predominant, often spreading into nosocomial settings. More coordinated and comprehensive surveillance to understand the true epidemiology of CA-MRSA in the Asia-Pacific region is urgently needed.