Genomic characterization of Staphylococcus aureus isolated from patients admitted to intensive care units of a tertiary care hospital: epidemiological risk of nasal carriage of virulent clone during admission.

We conducted a molecular epidemiological study of Staphylococcus aureus using whole-genome sequence data and clinical data of isolates from nasal swabs of patients admitted to the intensive care unit (ICU) of Hiroshima University hospital. The relationship between isolate genotypes and virulence factors, particularly for isolates that caused infectious diseases during ICU admission was compared with those that did not. The nasal carriage rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in patients admitted to the ICU were 7.0% and 20.1%, respectively. The carriage rate of community-acquired (CA)-MRSA was 2.3%, accounting for 32.8% of all MRSA isolates. Whole-genome sequencing analysis of the MRSA isolates indicated that most, including CA-MRSA and healthcare-associated (HA)-MRSA, belonged to clonal complex (CC) 8 [sequence type (ST) 8] and SCCmec type IV. Furthermore, results for three disease foci (pneumonia, skin and soft tissue infection, and deep abscess) and the assessment of virulence factor genes associated with disease conditions [bacteremia, acute respiratory distress syndrome (ARDS), disseminated intravascular coagulopathy (DIC), and septic shock] suggested that nasal colonization of S. aureus clones could represent a risk for patients within the ICU. Particularly, MRSA/J and MSSA/J may be more likely to cause deep abscess infection; ST764 may cause ventilation-associated pneumonia, hospital-acquired pneumonia and subsequent bacteremia, and ARDS, and tst-1-positive isolates may cause DIC onset.IMPORTANCENasal colonization of MRSA in patients admitted to the intensive care unit (ICU) may predict the development of MRSA infections. However, no bacteriological data are available to perform risk assessments for Staphylococcus aureus infection onset. In this single-center 2-year genomic surveillance study, we analyzed all S. aureus isolates from nasal swabs of patients admitted to the ICU and those from the blood or lesions of in-patients who developed infectious diseases in the ICU. Furthermore, we identified the virulent clones responsible for causing infectious diseases in the ICU. Herein, we report several virulent clones present in the nares that are predictive of invasive infections. This information may facilitate the design of preemptive strategies to identify and eradicate virulent MRSA strains, reducing nosocomial infections within the ICU.

Complete genome sequence of cfr(B)-carrying Enterococcus raffinosus isolated from bile in a patient in Japan.

OBJECTIVES: Linezolid is an antibiotic used to treat infectious diseases caused by vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus. Recently, Enterococcus Spp.-carrying mobile linezolid resistance genes were reported. Herein, we report the complete genome sequence of Enterococcus raffinosus JARB-HU0741, which was isolated from a bile sample of a patient in Japan on May 5, 2021, and carries a linezolid resistance gene, cfr(B). Nevertheless, this isolate was susceptible to linezolid. METHODS: Whole-genome sequencing was performed using HiSeq X FIVE (Illumina) and GridION (Oxford Nanopore Technologies). The sequence reads were assembled using Unicycler v0.4.8, and the complete genome was annotated using DFAST v1.2.18. Antimicrobial resistance genes were detected with Abricate v1.0.1, using the ResFinder database. The minimum inhibitory concentrations (MICs) were determined using broth microdilution and interpreted according to the guidelines of the Clinical and Laboratory Standards Institute. RESULTS: E. raffinosus JARB-HU0741 contained a 3 248 808-bp chromosome and a 1 156 277-bp megaplasmid. cfr(B) was present in the Tn6218-like transposon, which was inserted into a gene encoding a PRD domain-containing protein present in the megaplasmid, but the isolate was susceptible to linezolid (MIC, 0.5 µg/mL). The Tn6218-like transposon was similar to the Tn6218 of Clostridioides difficile Ox3196 and the Tn6218-like transposon of Enterococcus faecium UW11733; however, three genes encoding a topoisomerase, an S-adenosylmethionine-dependent methyltransferase, and a TetR family transcriptional regulator were present in the previous Tn6218- or Tn6218-like transposon. CONCLUSION: This is the first report of the complete genome sequence of E. raffinosus carrying cfr(B). E. raffinosus carrying cfr(B) without linezolid resistance poses a threat, as it could serve as a reservoir for mobile linezolid resistance genes.

Complete genome sequence of optrA-carrying Enterococcus faecalis isolated from open pus in a Japanese patient.

OBJECTIVES: The occurrence of linezolid resistance in enterococci has recently increased. Here, we report the genomic characterization of Enterococcus faecalis strain JARB-HU0796-isolated from the open pus of a patient in Hiroshima, Japan-which shows nonsusceptibility to linezolid (MIC of 4 µg/mL). METHODS: JARB-HU0796 whole-genome sequencing was performed using short-read sequencing with Illumina Hiseq X Five and long-read sequencing using GridION. These reads were collected using the assembly pipeline Unicycler and annotated with DFAST. Antimicrobial resistance genes were detected using the Abricate and ResFinder databases, and the sequence type identified using PubMLST. The antimicrobial susceptibility of JARB-HU0796 was determined with the Eiken dry-plate QH02 system. RESULTS: The JARB-HU0796 complete genome contained a circular chromosome (2 722 585 bp) and two circular plasmids (85 996 bp and 58 872 bp). The chromosome harbours the optrA gene, which confers resistance to oxazolidinones and phenicols. JARB-HU0796 showed nonsusceptibility to linezolid and multidrug resistance to other antibiotics. MLST analysis identified JARB-HU0796 as ST476, similar to the optrA-positive E. faecalis ST476 isolates from swine (South Korea, 2020) and pet food (Switzerland, 2022). The optrA region of JARB-HU0796 is nearly identical to that of ST476 E. faecalis strain TZ2, isolated from humans (China, 2013). CONCLUSIONS: To the best of our knowledge, this is the first report of the complete genome sequence of E. faecalis ST476 carrying optrA on a chromosome isolated from a patient in Japan. The strain may have originated in animals, suggesting that the organisms acquired resistance to linezolid because the optrA gene may be closely spread between animals and humans.

A case of bloodstream infection caused by Ruminococcus gnavus without gastrointestinal involvement.

We report a case of bloodstream infection due to Ruminococcus gnavus (R. gnavus) associated with pelvic abscess in a 74-year-old female patient undergoing radiotherapy for cervical cancer. Gram staining of positive anaerobic blood cultures revealed short chains of gram-positive cocci. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry was performed directly on the blood culture bottle, and 16S rRNA sequencing identified the bacterium as R. gnavus. There was no leakage from the sigmoid colon to rectum on enterography, and R. gnavus was not found in the culture of her pelvic abscess. After the administration of piperacillin/tazobactam, her condition markedly improved. This patient with R. gnavus infection demonstrated no gastrointestinal involvement, whereas past published cases reported diverticulitis or intestinal damage. It is possible that bacterial translocation of R. gnavus occurred from the gut microbiota, due to damage to the intestinal tract caused by radiation.

Prevalence of Mycoplasma hominis, Ureaplasma urealyticum, and Ureaplasma parvum detection in urine and respiratory tract samples in Hiroshima, Japan.

Background: Mycoplasma hominis, Ureaplasma parvum, and Ureaplasma urealyticum are commensal bacteria that are associated with colonization and infection of the urogenital tract. However, colonization of the respiratory tract by these microorganisms in adults has not been fully investigated. Methods: Urine and respiratory tract samples (sputum, tracheal aspirates, and bronchoalveolar lavage) of patients aged 20-80 years were analyzed to detect the presence of M. hominis, U. parvum, and U. urealyticum using a conventional PCR method. The samples were submitted to the microbiological clinical laboratory of Hiroshima University Hospital from December 1, 2021 to May 31, 2022. Results: In total, 334 urine and 238 respiratory tract samples were analyzed. The overall detection rates of M. hominis, U. parvum, and U. urealyticum were 2.9%, 1.7%, and 2.3% in male urine; 7.0%, 13.8%, and 1.9% in female urine; 2.2%, 0%, and 2.2% in male respiratory tract; and 0%, 2.0%, and 0% in female respiratory tract, respectively. In urine samples, the detection rates of M. hominis, U. parvum, and U. urealyticum were significantly higher (p < 0.001) for women (29/159; 18.2%) than for men (10/175; 5.7%); however, in respiratory tract samples, the detection rates were not significantly different (p = 0.70) between women (2/101; 2.0%) and men (5/137; 3.7%). Further, both the urine and respiratory samples of 83 patients were analyzed. Three male samples were positive for M. hominis or U. urealyticum, and M. hominis and U. urealyticum were matched in both the urine and respiratory tract samples: M. hominis (n = 1), U. urealyticum (n = 1), M. hominis + U. urealyticum (n = 1). Conclusion: M. hominis, U. parvum, and U. urealyticum were detected in the respiratory tract of not only the young patients, but also of patients aged 50-60 years. Further studies are required to understand the relationship of these microorganisms in urogenital and respiratory tract samples with extra-genital infections.

Verification of quality assurance for blood culture surveillance using 6 years of data from the Japan Infection Prevention and Control Conference for National and Public University Hospitals.

The importance of blood culture has been widely recognized, and there is a need for monitoring to evaluate the accuracy of blood culture that reflects domestic healthcare systems. In this study, we assessed 6-year trends in blood culture quality assurance data. The Japan Infection Prevention and Control Conference for National and Public University Hospitals conducted yearly blood culture surveillance at 52 national public university hospitals from 2015 to 2020. Statistical analysis showed that comparison with the previous year showed significant differences in the number of blood cultures per 1000 patient-days in all years. The number of blood cultures per 1000 admissions was not significantly different in 2017 and 2018, but significant differences were shown in all other years. The multiple blood culture set rate was significantly different between non-pediatric inpatients and outpatients but not between pediatric inpatients and outpatients. The contamination rate did not differ significantly. For all parameters, significant differences were found when comparing 2015 and 2020. Our survey showed that although the sample number improved over time, even the most recent values for 2020 were lower than Cumitech's targets. It is difficult to assess whether these sample numbers are appropriate because target values have not been set for the various types of hospitals in Japan. Surveillance is a useful tool for monitoring quality assurance for blood culture. All parameters improved over the 6-year period, but it is necessary to establish a benchmark for evaluating optimization. We will continue to monitor quality assurance and work on setting benchmarks.

Different CprABC amino acid sequences affect nisin A susceptibility in Clostridioides difficile isolates.

Clinical isolates of Clostridioides difficile sometimes exhibit multidrug resistance and cause diarrhea after antibiotic administration. Metronidazole and vancomycin are often used as therapeutic agents, but resistance to these antibiotics has been found clinically. Therefore, the development of alternative antimicrobial agents is needed. Nisin A, produced by Lactococcus lactis, has been demonstrated to be effective against C. difficile infection. In this study, we evaluated the susceptibility of 11 C. difficile clinical isolates to nisin A and found that they could be divided into 2 groups: high and low susceptibility. Since CprABC and DltDABC, which are responsible for nisin A efflux and cell surface charge, respectively, have been reported to be related to nisin A susceptibility, we investigated the expression of cprA and dltA among the 11 strains. cprA expression in all strains was induced by nisin A, but dltA expression was not. The expression levels of both genes did not correlate with nisin A susceptibility in these clinical isolates. To evaluate cell surface charge, we performed a cytochrome C binding assay and found no relationship between charge and nisin A susceptibility. Then, we determined the whole genome sequence of each clinical isolate and carried out phylogenetic analysis. The 11 isolates separated into two major clusters, which were consistent with the differences in nisin A susceptibility. Furthermore, we found common differences in several amino acids in the sequences of CprA, CprB, and CprC between the two clusters. Therefore, we speculated that the different amino acid sequences of CprABC might be related to nisin A susceptibility. In addition, C. difficile strains could be divided in the same two groups based on susceptibility to epidermin and mutacin III, which are structurally similar to nisin A. These results suggest that genotypic variations in C. difficile strains confer different susceptibilities to bacteriocins.

Impact of the early phase of COVID-19 on the trends of isolated bacteria in the national database of Japan: an interrupted time-series analysis.

OBJECTIVES: During the coronavirus disease 2019 (COVID-19) pandemic, a change in the trend of infections was observed. However, there are few reports comprehensively assessing the impact of the early phase of COVID-19 on the trend of bacteria isolated. METHODS: We extracted the number of positive cultures of hospitalized patients for approximately 200 institutions using the Japanese national database. The outcome was the ratio of 10 species isolated in comparison to the total isolates for each month. Interrupted time-series analyses were conducted between 13 (from Jan-2019 to Jan-2020) and 8 (from May-2020 to Dec-2020) monthly data points. RESULTS: A total of 369,210 isolates were involved. Differences in the level change for Streptococcus pneumoniae, Haemophilus influenzae, and Streptococcus pyogenes decreased significantly by 0.272 (95% confidence interval [CI]:0.192-0.352), 0.244 (95%CI:0.174-0.314), and 0.324 (95%CI:0.06-0.589), respectively. Bacteria transmitted by contact infection, such as Staphylococcus aureus, did not decrease. Differences in slope change were not significant in all species. CONCLUSIONS: The ratios of isolated bacteria transmitted by droplet infection decreased immediately after the early phase of COVID-19 and maintained the same level. The awareness and behavioral changes toward increased COVID-19 prevention might have a substantial impact on the prevention of bacterial infections, especially droplet infections.

Bacterial susceptibility changes post national shortage of first cephalosporin in Japan: a longitudinal retrospective database study using interrupted time series analysis.

OBJECTIVES: The clinical evidence for the effect of narrow-spectrum antimicrobial shortages on bacterial susceptibility is limited. Our purposes were to determine the affects of the disruption of most of the cefazolin (CEZ) supply in Japan on the susceptibility of pathogens and to analyze how long these changes persisted after the shortage of CEZ. METHODS: We performed an interrupted time series analysis using the Japanese Infectious Disease Nationwide database. We analyzed each pathogen before and after CEZ shortage in 52 university hospitals from 2018 to 2020. May to November 2019 was designated as the implementation term for CEZ shortage. The primary outcome was the susceptibility to CEZ and other antimicrobial agents. Amongst all pathogens isolated from facilities, we identified pathogens that were tested for susceptibility to CEZ. RESULTS: Of the 26 pathogens identified, analysis was performed on a total of 36,346 isolates of five pathogens (Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Proteus mirabilis, and Staphylococcus aureus). Amongst four Gram-negative pathogens with low susceptibility, there were no significant immediate changes after the CEZ shortage; however, the slope change significantly increased by 1.29 to 2.69% per month and continued to improve one year after the shortage. Regarding S. aureus, which was highly susceptible at the baseline, neither immediate change nor slope was significant. CONCLUSION: This quasi-experimental analysis using a nationwide-large database revealed that restriction of use because of narrow-spectrum antimicrobial shortages may lead to improved susceptibility over the subsequent year. The results suggest that temporary switching of antimicrobial agents on a national scale could be effective.

Clinical characteristics of Actinotignum schaalii bacteremia in a Japanese tertiary hospital.

We retrospectively analyzed seven patients with Actinotignum schaalii bacteremia in a tertiary hospital in Japan. Pyelonephritis was the most frequent source of bacteremia, followed by Fournier's gangrene and pyometra. All patients with pyelonephritis had underlying urological conditions, ureteral stents, nephrostomy, ureteral stones, or ureterocele.

Case Report: Emphysematous Pyelonephritis With a Congenital Giant Ureterocele.

A 14-year-old girl noticed malodorous urine and experienced left flank pain. The patient was presented to our hospital with gradually increasing pain. She had no underlying disease but had a history of pain on micturition for several days. Hematologic examination indicated low white blood cell and platelet counts and a high serum lactate level. Computed tomography showed that a part of the parenchyma of the left kidney had poor contrast and was deteriorated, with fluid and gas retention from the perirenal region to the retroperitoneal cavity. A left hydroureter and large ureterocele were observed in the bladder. She was diagnosed with emphysematous pyelonephritis (EPN) with a giant congenital ureterocele. Vasopressors and blood transfusion failed to maintain normal circulatory dynamics, and an open left nephrectomy and transurethral ureterocele fenestration were performed. The excised outer portion of the left kidney was dissolved by the infection and replaced with blood clots and necrotic tissue. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identified the inflammatory, gas-producing bacteria Actinotignum schaalii, Peptoniphilus asaccharolyticus, and Actinomyces odontolyticus. Meropenem was administered for 4 days postoperatively and then de-escalated to sulbactam/ampicillin for another 10 days. The patient was discharged on day 17 of hospitalization, and the postoperative course remained favorable. EPN is extremely rare in pediatric patients, and it is believed that nephrectomy is sometimes necessary if the patient does not have normal circulatory dynamics despite the use of catecholamines.

The effect of pulsed-xenon ultraviolet disinfection on surfaces contaminated with vancomycin-resistant Enterococci in a Japanese hospital.

INTRODUCTION: Recently, a worldwide outbreak of vancomycin-resistant Enterococci (VRE) was reported. However, due to the low incidence of VRE infection and colonization, VRE contamination of hospital environments has not been fully investigated in Japan. METHODS: Surfaces were swabbed, before and after manual cleaning and after pulsed xenon ultraviolet (PX-UV) disinfection, in five patient rooms that had been occupied by patients colonized with VRE. Difference in the number of VRE-positive samples and VRE colony forming units (CFUs), before and after disinfection, for each cleaning method was estimated. RESULTS: We detected VRE contamination in 22/60 (37%) and 14/60 (23%) samples collected before and after manual cleaning, respectively. In contrast, VRE contamination was not detected in the samples collected after PX-UV disinfection. In addition, 3/5 (60%) spray nozzles of electric warm-water bidet toilet seats were found to be contaminated with VRE before terminal cleaning. Manual cleaning caused a significant decrease in the number of VRE CFUs compared with that before cleaning (P = 0.031). PX-UV disinfection also caused a significant decrease in the number of VRE CFUs compared to that of manual cleaning (P < 0.001). CONCLUSION: We identified hot spots of severe contamination, such as private bathrooms in patient rooms and areas around the bed of patients using diapers and required assistance. VRE contamination persisted even after terminal disinfection; PX-UV disinfection in addition to terminal disinfection was effective at eliminating VRE contamination. These results can be useful in controlling the spread of VRE infections in Japanese hospitals.

Clinical and microbiological characteristics of Eggerthella lenta bacteremia at a Japanese tertiary hospital.

Eggerthella lenta is an important cause of anaerobic bloodstream infections and is associated with high mortality. However, there are few reports of E. lenta infection in Japan. This study aimed to evaluate the clinical and microbiological characteristics of bacteremia caused by E. lenta in Hiroshima, Japan. We retrospectively analyzed E. lenta bacteremia patients at the Hiroshima University Hospital between January 2012 and December 2020. During the study period, 14 patients with E. lenta bacteremia were identified. All E. lenta isolates were cultured in anaerobic bottles, and the median time to blood culture positivity was 52.9 h. In most cases (85.6%), the source of E. lenta bacteremia was associated with intra-abdominal infections, and colon perforation was the most frequent source of E. lenta bacteremia (42.9%, n = 6). Antimicrobial susceptibility testing showed high minimal inhibitory concentrations (MIC) of piperacillin-tazobactam (TZP) and 100% susceptibility to ampicillin-sulbactam, carbapenems, and metronidazole. This study demonstrates that E. lenta bacteremia is associated with intra-abdominal infections, particularly colon perforation, and a high MIC of TZP. When gram-positive anaerobes are detected in the blood cultures of patients with severe intra-abdominal infections, clinicians should suspect E. lenta, and it may be better to change antimicrobial agents from TZP.

Combining pulsed xenon ultraviolet disinfection with terminal manual cleaning helps reduce the acquisition rate of methicillin-resistant Staphylococcus aureus.

BACKGROUND: The clinical effectiveness of ultraviolet light (UV) disinfection remains unclear. This study aimed to investigate the effect of adding pulsed xenon UV (PX-UV) disinfection to the terminal cleaning protocol on the rate of methicillin-resistant Staphylococcus aureus (MRSA) acquisition at a Japanese hospital. METHODS: The use of a PX-UV disinfection device was added to the manual terminal cleaning protocol applied after the discharge or transfer of patients treated in the intensive and high care units. We used a Poisson regression model to examine the incidence of MRSA acquisition, based on the study period, PX-UV intervention status, unit type, and the rate of consumption of alcohol-based hand rub (ABHR). RESULTS: Approximately 86% of the rooms in the intervention units were terminally disinfected with the PX-UV device. In the intervention units, the incidence of MRSA acquisition decreased from 3.56 per 1,000 patient-days in the nonintervention period to 2.21 per 1,000 patient-days in the intervention period. Moreover, the use of PX-UV disinfection decreased the risk of MRSA acquisition (incident rate ratio: 0.556; 95% confidence interval, 0.309-0.999; P = .0497). ABHR consumption did not affect the risk of MRSA acquisition. CONCLUSIONS: Adding PX-UV disinfection to terminal manual cleaning reduced the rate of MRSA acquisition.

Effectiveness of pulsed xenon ultraviolet disinfection for Clostridioides (Clostridium) difficile surface contamination in a Japanese hospital.

BACKGROUND: Contaminated environmental surfaces are important sources of transmission for healthcare-associated pathogens, including Clostridioides (Clostridium) difficile. The effectiveness of manual bleach cleaning and pulsed xenon ultraviolet (PX-UV) disinfection on C. difficile contamination of hospital room high-touch surfaces in Japan was evaluated. METHODS: The environmental surfaces of 20 C. difficile infection (CDI) isolation rooms were sampled immediately after CDI patients were discharged or transferred. High-touch surfaces were sampled before and after either bleach cleaning or PX-UV disinfection in addition to nonbleach cleaning. Changes in the number of C. difficile-positive samples and bacterial counts for each cleaning method were assessed. RESULTS: Overall, 286 samples were collected (bleach cleaning, 144 samples; PX-UV disinfection, 142 samples). Before cleaning, the positive rates of C. difficile were 27.8% and 31.0% in bleach cleaning and PX-UV disinfection, respectively. Both bleach cleaning and PX-UV disinfection significantly reduced overall C. difficile-positive samples (P = .018 and P = .002, respectively) and C. difficile colony-forming unit counts (P = .002 and P = .001, respectively). CONCLUSIONS: PX-UV disinfection in addition to manual nonbleach cleaning effectively reduces C. difficile contamination from high-touch surfaces. Further studies are warranted to evaluate the effect of PX-UV disinfection on CDI rates in Japanese hospitals.

Clinical evaluation of a non-purified direct molecular assay for the detection of Clostridioides difficile toxin genes in stool specimens.

Recently, a new rapid assay for the detection of tcdB gene of Clostridioides difficile was developed using the GENECUBE. The assay can directly detect the tcdB gene from stool samples without a purification in approximately 35 minutes with a few minutes of preparation process. We performed a prospective comparative study of the performance of the assay at eight institutions in Japan. Fresh residual stool samples (Bristol stool scale ≥5) were used and comparisons were performed with the BD MAX Cdiff assay and toxigenic cultures. For the evaluation of 383 stool samples compared with the BD MAX Cdiff assay, the sensitivity, and specificity of the two assays was 99.0% (379/383), 98.1% (52/53), 99.1% (327/330), respectively. In the comparison with toxigenic culture, the total, sensitivity, and specificity were 96.6% (370/383), 85.0% (51/60), and 98.8% (319/323), respectively. The current investigation indicated the GENECUBE Clostridioides difficile assay has equivalent performance with the BD MAX Cdiff assay for the detection of tcdB gene of C. difficile.

Efficacy of pulsed xenon ultraviolet disinfection of multidrug-resistant bacteria and Clostridioides difficile spores.

BACKGROUND: Contamination of healthcare environments by multidrug-resistant organisms (MDRO) and Clostridioides difficile is a risk for healthcare-associated infections. The efficacy of pulsed xenon ultraviolet (PX-UV) disinfection in healthcare environments has been described previously. However, there are few reports about PX-UV disinfection in Japan. The aim of this study was to investigate in vitro the efficacy of PX-UV disinfection of MDRO and C. difficile spores commonly isolated in Japanese hospitals. METHODS: We investigated reductions in microbial counts after exposure to PX-UV of the following clinically-isolated organisms on seeding agar plates: methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium, carbapenemase-producing Klebsiella pneumoniae, extended spectrum ß-lactamase-producing Escherichia coli, multidrug resistant Acinetobacter baumannii, and C. difficile spores. We also visually assessed the attenuation of disinfection by shielding of MRSA and carbapenemase-producing K. pneumoniae from PX-UV exposure. RESULTS: PX-UV disinfection for 5 min induced >5-log colony-forming units (CFU)/cm2 growth inhibition of all the MDRO. PX-UV disinfection for 15 min induced >3-log CFU/cm2 growth inhibition of C. difficile spores. Where a plate was shielded from PX-UV exposure the bacteria showed confluent growth, but no colonies were observed on unshielded (exposed) parts of the plates. CONCLUSION: This study shows the efficacy of PX-UV disinfection against clinical MDROs. C. difficile spores were more resistant to PX-UV disinfection than vegetative bacteria. Further evaluation of the efficacy of PX-UV disinfection in reducing the contamination of real-world surfaces and the incidence of healthcare-associated infections is needed.

Oral colonisation by antimicrobial-resistant Gram-negative bacteria among long-term care facility residents: prevalence, risk factors, and molecular epidemiology.

BACKGROUND: For residents of long-term care facilities (LTCFs), antimicrobial-resistant bacteria (ARB) are a risk factor, yet their oral colonisation, potentially leading to aspiration pneumonia, remains unclear. This study was undertaken to survey the prevalence, phenotypic characteristics, and molecular epidemiology of antimicrobial-resistant Gram-negative bacteria in the oral cavity of LTCF residents, and to analyse the risk factors for such carriers. METHODS: This study involved 98 residents of a LTCF in Hiroshima City, Japan, aged between 55 and 101 years. Oropharyngeal swabs were collected and plated on screening media for ESBL-producing and carbapenem-resistant bacteria; isolates were identified and tested for antibiotic susceptibility; biofilm formation was tested in vitro; identification of epidemic clones were pre-determined by PCR; resistance genes, sequence types, and whole-genome comparison of strains were conducted using draft genome sequences. Demographic data and clinical characterisations were collected and risk factors analysed. RESULTS: Fifty-four strains from 38% of the residents grew on screening media and comprised predominantly of Acinetobacter spp. (35%), Enterobacteriaceae spp. (22%), and Pseudomonas spp. (19%). All Escherichia coli isolates carried CTX-M-9 group and belonged to the phylogroup B2, O25:H4 ST131 fimH30 lineage. Six Acinetobacter baumannii isolates presented identical molecular characteristics and revealed more biofilm production than the others, strongly suggesting their clonal lineage. One Acinetobacter ursingii isolate displayed extensive resistance to various ß-lactams due to multiple acquired resistance genes. One Pseudomonas aeruginosa isolate showed exceptional resistance to all ß-lactams including carbapenems, aminoglycosides, and a new quinolone, showing a multidrug-resistant Pseudomonas aeruginosa (MDRP) phenotype and remarkable biofilm formation. Genome sequence analysis revealed this isolate was the blaIMP-1-positive clone ST235 in Japan. Strokes (cerebral infarction or cerebral haemorrhage) and percutaneous endoscopic gastrostomy tubes were recognised as risk factors for oral colonisation by ARB in the LTCF residents. CONCLUSIONS: ARB, as defined by growth on screening agar plates, which carried mobile resistance genes or elements or conferred high biofilm formation, were already prevalent in the oral cavity of LTCF residents. Health-care workers involved in oral care should be aware of antimicrobial resistance and pay special attention to transmission prevention and infection control measures to diminish ARB or mobile resistance elements dissemination in LTCFs.

Aeromonas dhakensis is not a rare cause of Aeromonas bacteremia in Hiroshima, Japan.

Aeromonas dhakensis, a newly recognized species, is often misidentified as A. hydrophila, A. veronii, or A. caviae by commercial phenotypic tests. Limited data about A. dhakensis are available in Japan. We retrospectively analyzed the patients with monomicrobial Aeromonas bacteremia at Hiroshima University Hospital from January 2011 to December 2017, and species re-identification was conducted using rpoD and gyrB gene sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) system. Of the 19 strains from blood isolates, A. caviae (n = 9, 47.4%), A. dhakensis (n = 4, 21.1%), A. hydrophila (n = 3, 15.8%), and A. veronii (n = 3, 15.8%) were re-identified. A. dhakensis was phenotypically misidentified as A. hydrophila (n = 3, 75%) or A. sobria (n = 1, 25%). A. dhakensis was also misidentified as A. caviae (n = 2, 50%), A. hydrophila (n = 1, 25%), and A. jandaei (n = 1, 25%) in MALDI-TOF MS system. Malignancies (n = 12, 63.2%) and liver cirrhosis (n = 7, 36.8%) were common comorbidities. Biliary tract infection was the most frequent source of Aeromonas bacteremia (n = 11, 57.9%). The major source of A. dhakensis bacteremia was also biliary tract infection (n = 3, 75%), and the 14-day infection-related mortality of A. dhakensis was 25%. A. dhakensis isolates showed similar clinical characteristics, antimicrobial susceptibility, and mortality with those of other Aeromonas species isolates. This study demonstrated that A. dhakensis is not a rare cause of Aeromonas bacteremia, but is often misidentified as A. hydrophila in Hiroshima, Japan. Further studies should be conducted to identify the geographical distribution and clinical impact of A. dhakensis in Japan.

Effect of pulsed xenon ultraviolet disinfection on methicillin-resistant Staphylococcus aureus contamination of high-touch surfaces in a Japanese hospital.

BACKGROUND: The hospital environment is an important source of multidrug-resistant organisms such as methicillin-resistant Staphylococcus aureus (MRSA). Here, we evaluated the efficacy of pulsed xenon ultraviolet (PX-UV) disinfection in addition to manual cleaning in a Japanese hospital. METHODS: Environmental samples were collected from inpatient rooms that had been occupied for at least 48 hours by patients infected or colonized with MRSA. High-touch surfaces from 11 rooms were sampled before and after manual cleaning and then after PX-UV disinfection. Changes in bacterial counts and in the number of aerobic bacteria (AB)- and MRSA-positive samples between sampling points were assessed. The time taken to complete PX-UV treatment of patient rooms was also recorded. RESULTS: A total of 306 samples were collected. PX-UV disinfection resulted in a significant decrease in abundance of AB and MRSA (mean colony-forming units 14.4 ± 38.7 to 1.7 ± 6.1, P < .001 and 1.1 ± 3.9 to 0.3 ± 2.0, P < .001, respectively) and in the number of AB- and MRSA-positive samples (58.8%-28.4%, P = .001 and 19.6%-3.9%, P < .001, respectively) compared with manual cleaning. The median time of in-room use of the PX-UV device was 20 minutes. CONCLUSIONS: The addition of PX-UV disinfection to the manual cleaning process significantly reduced AB and MRSA contamination of high-touch surfaces in hospital inpatient rooms.