Candida auris Outbreak in a Multidisciplinary Hospital in Romania during the Post-Pandemic Era: Potential Solutions and Challenges in Surveillance and Epidemiological Control.

Candida auris is a newly emerging yeast, which is raising public health concerns due to its outbreak potential, lack of protocols for decontamination and isolation of patients or contacts, increased resistance to common antifungals, and associated high mortality. This research aimed to describe the challenges related to identifying the outbreak, limiting further contamination, and treating affected individuals. We retrospectively analyzed all cases of C. auris detected between October 2022 and August 2023, but our investigation focused on a three-month-long outbreak in the department of cardio-vascular surgery and the related intensive care unit. Along with isolated cases in different wards, we identified 13 patients who became infected or colonized in the same area and time, even though the epidemiological link could only be traced in 10 patients, according to the epidemiologic investigation. In conclusion, our study emphasizes the substantial challenge encountered in clinical practice when attempting to diagnose and limit the spread of an outbreak. Therefore, it is crucial to promptly apply contact precaution measures and appropriate environmental cleaning, from the first positive case detected.

Outbreak of Severe Acute Respiratory Syndrome Coronavirus 2 in a Rural Community Hospital during Omicron Predominance.

Healthcare-associated infections due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has increased since the discovery of the Omicron variant. We describe a SARS-CoV-2 outbreak in the medicine-surgery unit of a rural community hospital at the time of high community transmission of Omicron variant in our county. The outbreak occurred in the medicine-surgery unit of an 89-bed rural community hospital in northern Maine. The characteristics of the patients and healthcare workers (HCWs) affected by the outbreak are described. Patient and HCW data collected as part of the outbreak investigation were used in this report. The outbreak control measures implemented are also described. A total of 24 people tested positive for SARS-CoV-2 including 11 patients and 13 HCWs. A total of 12 of the 24 (50%) persons were symptomatic, and rhinorrhea was the most common symptom noted (8/12, 67%). None of the symptomatic persons had gastrointestinal symptoms or symptoms of a loss of sense of smell or taste. All HCWs were vaccinated and 8 of the 11 patients were vaccinated. Outbreak control measures in the affected unit included implementation of full PPE (N95 respirators, eye protection, gowns and gloves) during all patient care, serial testing of employees and patients in the affected unit, cohorting positive patients, closing visitation and thorough environmental cleaning including use of ultraviolet (UV) light disinfection. This outbreak exemplifies the high transmissibility of the Omicron variant of SARS-CoV-2. The outbreak occurred despite a well-established infection control program. We noted that serial testing, use of N95 respirators during all patient care and UV disinfection were some of the measures that could be successful in outbreak control.

Stenotrophomonas riyadhensis sp. nov., isolated from a hospital floor swab.

During the analysis of a collection of Pseudomonas strains linked to an outbreak in an intensive care unit at King Faisal Specialist Hospital and Research Center in 2019, one isolate (CFS3442T) was identified phenotypically as Pseudomonas aeruginosa. However, whole-genome sequencing revealed its true identity as a member of the genus Stenotrophomonas, distinct from both P. aeruginosa and Stenotrophomonas maltophilia. The isolate demonstrated: (i) a significant phylogenetic distance from P. aeruginosa; (ii) considerable genomic differences from several S. maltophilia reference strains and other Stenotrophomonas species; and (iii) unique phenotypic characteristics. Based on the combined geno- and phenotypic data, we propose that this isolate represents a novel species within the genus Stenotrophomonas, for which the name Stenotrophomonas riyadhensis sp. nov. is proposed. The type strain is CFS3442T (=NCTC 14921T=LMG 33162T).

Urinary tract infection associated with bacteremia caused by vancomycin-resistant enterococcus following continent urinary diversion.

Key Clinical Message: Even in a country where vancomycin-resistant enterococcus is rare, multidrug-resistant organism precautions are necessary when admitting patients with a history of medical exposure in other countries. On admission, screening is necessary and if infection is confirmed, a multidisciplinary approach involving different specialists is required. Abstract: The patient was a 49-year-old Japanese female living in the United States. Total pelvic exenteration for cervical carcinoma, Miami pouch formation, and ileostomy had been performed in the United States. She returned to Japan to undergo postoperative adjuvant chemotherapy. Fever and abdominal pain occurred 42 days after surgery. She consulted the fever outpatient clinic, and a diagnosis of urinary retention-associated acute renal failure and pyelonephritis was made. We detected vancomycin-resistant enterococcus on urine/blood culture 5 days after admission. Infection control measures were implemented, and the ward was closed for 3 days. We administered linezolid, which was effective for pyelonephritis and bacteremia.

The Outbreak of SARS-CoV-2 in a Medical Ward and Its Containment: An Experience From a Tertiary Care Centre in North India.

Background Periodic outbreaks of SARS-CoV-2 in hospital settings amidst the recent pandemic are well known. However, the timely control of such outbreaks was key to preventing morbidity among vulnerable patients as well as reducing sickness absenteeism among healthcare workers. This is the first study of its kind in India. Methods An outbreak investigation was conducted between June 12 and July 18, 2020, at the All India Institute of Medical Sciences, New Delhi, India, during the first wave of COVID-19. Results A total of 27 individuals were infected during this time, including people visiting the hospital and healthcare workers. A thorough investigation led us to the epidemiological link between cases and allowed us to bring reforms to the existing hospital policy of screening and admission of COVID-19 patients and those suspected to have the infection. This experience helped us avoid future outbreaks during the second wave of COVID-19 in our hospital. Conclusion The SARS-CoV-2 virus is highly transmissible, especially in hospital settings due to the high burden of patients and close proximity between patients. Timely intervention is the key to effective control of hospital outbreaks, as it can avoid morbidity in patients and reduce sickness absenteeism among healthcare workers.

Detailed analysis of in-hospital transmission of SARS-CoV-2 using whole genome sequencing.

BACKGROUND: Hospital transmission of SARS-CoV-2 has proved difficult to control, with healthcare-associated infections troublesome throughout. AIM: To understand factors contributing to hospital transmission of infections, which is necessary for containing spread. METHODS: An outbreak of 56 staff and patient cases of COVID-19 over a 31-day period in a tertiary referral unit is presented, with at least a further 29 cases identified outside of the unit and the hospital by whole genome sequencing (WGS). FINDINGS: Transmission is documented from staff to staff, staff to patients, and patients to staff, showing disruption of a tertiary referral service, despite implementation of nationally recommended control measures, superior ventilation, and use of personal protective equipment. There was extensive spread from the index case, despite this patient spending only 10 h bed bound on the ward in strict cubicle isolation and with an initial single target low level (CT = 32) polymerase chain reaction test. CONCLUSION: This investigation highlights how effectively and rapidly SARS-CoV-2 can spread in certain circumstances. It raises questions about infection control measures in place at the time and calls into question the premise that transmissibility can be reliably detected by using lower sensitivity rapid antigen lateral flow tests. We also highlight the value of early intervention in reducing impact as well as the value of WGS in understanding outbreaks.

Evaluation of physical and psychological status of health care workers infected with COVID-19 during a hospital outbreak in Japan.

PURPOSE: COVID-19 causes physical and psychological impacts on health care workers (HCWs), especially when it occurs during an outbreak. As there are few reports on outcomes of HCWs infected with COVID-19 during a hospital outbreak, we investigated the physical and psychological impacts on HCWs infected with COVID-19 during an outbreak in our hospital. METHODS: During the outbreak in our hospital, 231 people were infected with COVID-19 including patients, HCWs and their families. Among them, 83 HCWs were enrolled in this study. Current quality of life (QOL) was assessed with the EuroQol-visual analogue scales (EQ-VAS), and motivation to keep on working was evaluated by a 10-point analogue scale. Physiological recovery rates including return to work (RTW) period were also analyzed. RESULTS: One nurse quit work due to anxiety regarding re-infection with COVID-19. The median period to RTW from the diagnosis was 14.0 (12.0-17.0) days. Motivation to keep on working was slightly reduced, and the EQ-VAS was 75.0 (65.0-83.6). There were no significant differences in QOL and motivation between male and female HCWs, nurses and other HCWs, treatment and non-treatment group, and supplemental and non-supplemental oxygen group. The most frequent persistent symptoms at 1,3 and 6 months after infection were anosmia followed by fatigue. CONCLUSION: Although QOL and motivation to keep on working were slightly reduced, only one HCW quit work. No severe persistent symptoms were observed, and the RTW period was relatively short.

Use of Statistical Process Control Methods for Early Detection of Healthcare Facility-Associated Nontuberculous Mycobacteria Outbreaks: A Single-Center Pilot Study.

BACKGROUND: Nontuberculous mycobacteria (NTM) are emerging pathogens increasingly implicated in healthcare facility-associated (HCFA) infections and outbreaks. We analyzed the performance of statistical process control (SPC) methods in detecting HCFA NTM outbreaks. METHODS: We retrospectively analyzed 3 NTM outbreaks that occurred from 2013 to 2016 at a tertiary care hospital. The outbreaks consisted of pulmonary Mycobacterium abscessus complex (MABC) acquisition, cardiac surgery-associated extrapulmonary MABC infection, and a bronchoscopy-associated pseudo-outbreak of Mycobacterium avium complex (MAC). We analyzed monthly case rates of unique patients who had positive respiratory cultures for MABC, non-respiratory cultures for MABC, and bronchoalveolar lavage cultures for MAC, respectively. For each outbreak, we used these rates to construct a pilot moving average (MA) SPC chart with a rolling baseline window. We also explored the performance of numerous alternative control charts, including exponentially weighted MA, Shewhart, and cumulative sum charts. RESULTS: The pilot MA chart detected each outbreak within 2 months of outbreak onset, preceding actual outbreak detection by an average of 6 months. Over a combined 117 months of pre-outbreak and post-outbreak surveillance, no false-positive SPC signals occurred (specificity, 100%). Prospective use of this chart for NTM surveillance could have prevented an estimated 108 cases of NTM. Six high-performing alternative charts detected all outbreaks during the month of onset, with specificities ranging from 85.7% to 94.9%. CONCLUSIONS: SPC methods have potential to substantially improve HCFA NTM surveillance, promoting early outbreak detection and prevention of NTM infections. Additional study is needed to determine the best application of SPC for prospective HCFA NTM surveillance in other settings.

Stenotrophomonas maltophilia outbreak with a commercial blood gas injector as the culprit and interventions for source and prevention: A possible passage between patient and ECMO water heater device.

BACKGROUND: Despite low virulence of Stenotrophomonas maltophilia, it represents one of the leading drug-resistant bacteria. We report a large outbreak of S. maltophilia infection associated with an unexpected source, which turned out to be a commercial needleless blood gas injector. METHODS: Over a period from January 1 to December10, 2021, 113 patients were identified to have S. maltophilia infection as documented by positive cultures from the clinical samples, extracorporeal membrane oxygenation (ECMO) water heater devices and commercial needleless blood gas injectors. RESULTS: Sixty-seven isolates (59 clinical, 4 ECMO, 4 blood gas injectors) were sent for molecular analysis. Both arbitrarily primed polymerase chain reaction and pulsed-field gel electrophoresis analyses showed 12 distinct genotypes. Of 67 isolates, 58 were clonally related (86.6%), with 52 indistinguishable strains from 4 blood gas needleless injectors, 46 patients' samples (78%), and 2 ECMO samples (50%). Two ECMO samples and 1 clinical sample were clonally identical. CONCLUSIONS: In the event that eradication of infections would not be possible despite taking all environmental disinfection measures including the ECMO devices, unexpected sources, such as a commercial needleless blood gas injector, should not be omitted from the list for surveillance. In addition, obtaining surveillance cultures of ECMO water reservoirs should be placed in the routine clinical practice.

A long-lasting Sphingomonas paucimobilis outbreak: A potential for pathogens to persist on environmental devices despite disinfection measures.

BACKGROUND: Sphingomonas paucimobilis, an aerobic, non-fermentative, Gram-negative opportunistic bacillus, can colonize everywhere in hospital settings where water is used. We reported a hospital S paucimobilis outbreak that persisted for nearly 2 years despite all necessary preventive measures. METHODS: Over a period from February 13, 2020 to December 3, 2021, 67 patients were identified to have S paucimobilis as documented by positive cultures from clinical samples, along with 19 positive environmental samples. RESULTS: Bacterial regrowth for molecular analysis could be obtained in 49 isolates (39 clinical, 4 extracorporeal membrane oxygenation (ECMO) water heater devices, 1 unused mouthwash solution, 5 water samples from thoracic drainage aspirators). Two distinct clonally indistinguishable genotypes were detected in AP-PCR and PFGE analyses, with 100% consistency. The main cluster was obtained consistently throughout the outbreak from 30 samples (61.2%: 24 clinical, 4 ECMO, 1 unused mouthwash solution, 1 water sample from the thoracic drainage aspirator). The other cluster involved 15 clinical samples and 4 water samples from the thoracic drainage aspirators. CONCLUSIONS: Given that waterborne pathogens can spread to a wide range of equipment used in healthcare environments, the pathogens can persist on the surfaces of environmental devices even after recommended disinfection measures have been applied. Therefore, individual tracking of all devices used in critical care settings, such as thoracic drainage aspirators and ECMO water heater devices, with records of pre- and post-disinfection procedures is of paramount importance for complete elimination of the source of infection.

Investigating a pulmonary Mycobacterium abscessus infection outbreak among elderly inpatients in the intensive care ward.

INTRODUCTION: Mycobacterium abscessus is an opportunistic nontuberculous mycobacteria pathogen; however, the prevalence of nosocomial and community infections is increasing. In January 2016, several bedridden inpatients in the intensive care unit of a hospital had positive sputum smears for acid-fast bacilli, suggesting a mycobacteria outbreak. METHODOLOGY: Acid-fast bacilli smear microscopy, isolation, and culturing were performed twice using sputa from each suspected intensive care unit inpatient (n = 13); in addition, medical history was obtained for each inpatient with suspected infection. Furthermore, environmental specimens were surveyed, collected, and cultured. We used DNA microarray chip analysis to identify positive mycobacterial isolates at the species level and performed whole-genome sequencing and phylogenetic tree construction. RESULTS: Seven inpatients had M. abscessus pulmonary infection, confirmed by 2 positive cultures; five of the inpatients had only one positive culture, while one had two negative cultures. Six of 13 ventilator condensate samples were mycobacterial culture-positive, identified as M. abscessus; the other environmental samples were negative. The M. abscessus isolates (15 sputa and 4 environmental samples) clustered together in the phylogenic analysis with only one single-nucleotide polymorphism difference. All patients were symptom-free after 8 months of multi-drug treatment. CONCLUSIONS: We confirmed a pulmonary M. abscessus outbreak among 12 bedridden patients in the intensive care unit through microbiological, molecular epidemiological, and environmental investigations. The possible infection source was contaminated ventilator condensate. This outbreak reemphasizes the importance of standardized ventilator maintenance and disinfection for preventing ventilator-associated pneumonia and is a reminder that nontuberculous mycobacteria-related ventilator-associated pneumonia is possible.

Clonal Spread of Carbapenem-Resistant Klebsiella pneumoniae Sequence Type 11 in Chinese Pediatric Patients.

Klebsiella pneumoniae often causes life-threatening infections in patients globally. Despite its notability, little is known about potential nosocomial outbreak and spread of K. pneumoniae among pediatric patients in low- and middle-income countries. Ninety-eight K. pneumoniae strains isolated from pediatric patients in a large general hospital in China between February 2018 and May 2019 were subjected to nanopore and Illumina sequencing and genomic analysis to elucidate transmission and genetic diversity. The temporal distribution patterns of K. pneumoniae revealed a cluster of sequence type 11 (ST11) strains comprising two clades. Most inferred transmissions were of clade 1, which could be traced to a common ancestor dating to mid-2017. An infant in the coronary care unit played a central role, potentially seeding transmission clusters in other wards. Major genomic changes during the outbreak included chromosomal mutations associated with virulence and gains and losses of plasmids encoding resistance. In summary, we report a nosocomial outbreak among pediatric patients caused by clonal dissemination of KPC-2-producing ST11 K. pneumoniae. Our findings highlight the value of whole-genome sequencing during outbreak investigations and illustrate that transmission chains can be identified during hospital stays. IMPORTANCE We report a nosocomial outbreak among pediatric patients caused by clonal dissemination of blaKPC-2-carrying ST11 K. pneumoniae. Strains of various sequence types coexist in the complex hospital environment; the quick emergence and spread of ST11 strains were mainly due to the plasmid-mediated acquisition of resistance genes. The spread of hospital infection was highly associated with several specific wards, suggesting the importance of genomic surveillance on wards at high risk of infection.

Investigating COVID-19 transmission in a tertiary hospital in Hanoi, Vietnam using social network analysis.

OBJECTIVES: In March 2020, a COVID-19 outbreak in a major referral hospital in Hanoi, Vietnam led to 7664 patients and staff being sent into lockdown for 2 weeks, and more than 52,200 persons across 49 provinces being quarantined. We assessed SARS-CoV-2 transmission patterns during this to-date largest hospital outbreak in Vietnam using social network analysis (SNA). METHODS: We constructed a directed relational network and calculated network metrics for 'degree', 'betweenness', 'closeness' and 'eigenvector' centrality to understand individual-level transmission patterns. We analysed network components and modularity to identify sub-network structures with disproportionately big effects. RESULTS: We detected 68 connections between 46 confirmed cases, of whom 27 (58.7%) were ancillary support staff, 7 (15.2%) caregivers, 6 (13%) patients and 2 (4.4%) nurses. Among the 10 most important cases selected by each SNA network metric, transmission dynamics clustered in 17 cases, of whom 12 (70.6%) cases were ancillary support staff. Ancillary support staff also constituted 71.1% of cases in the dominant sub-network and 68.8% of cases in the three largest sub-communities. CONCLUSIONS: We identified non-clinical ancillary support staff, who are responsible for room service and food distribution in hospital wards in Vietnam, as a group with disproportionally big impacts on transmission dynamics during this outbreak. Our findings call for a holistic approach to nosocomial outbreak prevention and response that includes both clinical and non-clinical hospital staff. Our work also shows the potential of SNA as a complementary outbreak investigation method to better understand infection patterns in hospitals and similar settings.

Controlling an Unprecedented Outbreak with Vancomycin-Resistant Enterococcus faecium in Germany, October 2015 to November 2019.

Hospital outbreaks with vancomycin-resistant enterococci (VRE) pose a serious health threat and a challenge to infection prevention and control (IPC). We herein report on a VRE outbreak of unprecedented extent in Southern Germany (October 2015-November 2019). We used descriptive epidemiology and whole-genome sequencing (WGS) for a detailed outbreak investigation. Of the 2905 cases, 2776 (95.3%) were colonized, whereas from 127 (3.7%), VRE could be isolated from otherwise sterile body fluids or sites unlikely for enterococci colonization. Cases had a median age of 78 years (IQR 68-84) and 1339/2905 (46%) were female. The majority of isolates sequenced belonged to the clonal lineage ST80/CT1013 (212/397, 53%). Nosocomial transmission was observed as well as the constant import of VRE into the hospital. Extensive IPC measures were implemented and terminated the outbreak in late 2019, eventually. Our study shows that the combination of epidemiological and genomic analyses is indispensable for comprehensive outbreak investigations. The adaptation of IPC measures to these findings, their timely implementation, and strict execution also allow containment of large VRE outbreaks in hospital settings.

Lessons learned from an outbreak of COVID-19 in the head and neck surgery ward of a Japanese cancer center during the sixth wave by Omicron.

INTRODUCTION: We describe a coronavirus disease (COVID-19) outbreak in a cancer center's head and neck surgery ward and the interventions to halt ongoing exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among healthcare workers and patients with cancer. METHODS: Case definition included all healthcare workers and all patients associated to the ward from January 27 to January 31, 2022 with a positive SARS-COV-2 antigen test. This retrospective descriptive study was conducted between January 27, 2022, and February 14, 2022. RESULTS: From January 28, 2022, to February 9, 2022, 84 cases (36 healthcare workers, 48 patients) were screened, and 26 (12 healthcare workers, 14 patients) were identified as SARS-CoV-2-positive. The proportion of healthcare providers who performed aerosol generating procedures on positive patients was 91% for positive cases and 49% for non-cases. Room sharing with patients with COVID-19 was 64% for positive cases and 21% for non-cases (57% vs. 21% with positive tracheostomy patients; 43% vs. 9% with positive cases using a nebulizer; 50% vs. 15% with positive cases requiring sputum suctioning, respectively). Compliance with the universal masking policy for patients was 36% of positive cases and 79% of non-cases. CONCLUSIONS: This is the first report of a nosocomial outbreak of COVID-19 in a head and neck surgery ward during the Omicron pandemic. Notably, there were a high number of positive cases among healthcare workers who performed aerosol generating procedures for positive patients and patients who shared the room with a patient with COVID-19 with the potential to generate aerosols.

Pseudomonas aeruginosa countrywide outbreak in hospitals linked to pre-moistened non-sterile washcloths, Norway, October 2021 to April 2022.

In November 2021, a clonal outbreak of Pseudomonas aeruginosa of novel sequence type ST3875 was detected in three patients who died of bloodstream infections in one hospital. By 25 April 2022, the outbreak included 339 cases from 38 hospitals across Norway. Initial hospital reports indicate Pseudomonas infection as the main contributing cause in seven deaths. In March 2022, the outbreak strain was identified in non-sterile pre-moistened disposable washcloths, used to clean patients, from three lots from the same international manufacturer.

An outbreak of Ralstonia pickettii bloodstream infection and clinical outcomes.

INTRODUCTION: Ralstonia pickettii infections are rare and may be mistaken for other bacteria. This study aims to report a hospital outbreak of R. pickettii at a tertiary hospital, which was initially misidentified as Ralstonia insidiosa, along with its clinical consequences. METHODOLOGY: A bacteraemia outbreak occurred between August 14 and October 4, 2019, infecting 22 patients admitted to diverse intensive care units. All isolates were identified with the use of the automated VITEK 2 Compact system and were then subjected to a microbial identification system, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Bacterial identification and genomic DNA typing was made using pulsed-field gel electrophoresis. Investigation covered all potential sources of the outbreak. RESULTS: An index patient and five additional patients developed fever while receiving care. Blood cultures of these patients yielded R. insidiosa by the VITEK 2 Compact system. Culture isolates were then submitted to a reference centre for confirmation by the MALDI-TOF MS system, where the bacterium turned out to be R. pickettii. No pathogen was isolated in the commercial products except for three samples of unopened sterile distilled water. Despite its discontinuation, 16 new cases were identified, in which blood cultures grew R. pickettii by the MALDI-TOF MS system. Attempts to uncover the source of the outbreak failed. Clinical manifestation was confined to fever in all the patients. CONCLUSIONS: During this outbreak, R. pickettii infections ran a relatively mild course without clinical deterioration or mortality, possibly due to low virulence.

Localized outbreaks of Pseudomonas aeruginosa belonging to international high-risk clones in a south Indian hospital.

Introduction. Pseudomonas aeruginosa is now considered as a major bacterial pathogen associated with hospital infections. Frequently, multidrug-resistant (MDR) and extensively drug-resistant (XDR) P. aeruginosa are being encountered. Unusual increase in the P. aeruginosa infections led to the suspicion of outbreaks in the urology ward and cardiothoracic and vascular surgery intensive care unit (CTVS-ICU).Hypothesis. We hypothesize that the localized outbreaks may have originated from environmental sources within the hospital premises. An alternative possibility is the transmission from a previously infected patient or hospital attendant. Understanding the drug-resistance profile and genome characteristics of these clinical samples would determine the likely source of infection and spread.Aim. To perform epidemiological and molecular investigations on the suspected outbreaks of P. aeruginosa in the study centre and identify potential sources of infection.Methodology. Fourteen drug-resistant P. aeruginosa isolated from patients of the urology ward, CTVS-ICU and tap waters collected during the suspected outbreaks were subjected to microbiological and genomic analysis. Comparative genome (CG) analysis of these 14 study genomes with 284 complete P. aeruginosa genomes was performed.Results. Multilocus sequence typing analysis revealed that the isolates belonged to five different sequence types (ST235, ST357, ST639, ST654 and ST1203) and clustered into three distinct groups while two CTVS-ICU isolates remained as singletons. Genome analysis distinguished that the outbreaks in the urology ward and CTVS-ICU are independent, epidemiologically unrelated to each other and with the tap-water isolates.Conclusion. This study highlights the presence of distinct, clonally unrelated, drug-resistant P. aeruginosa within a hospital setting. The genome analysis of the two localized outbreaks revealed their distinct genetic background and phylogenetically unrelated origin. Vigilant screening and effective implementation of infection control measures led to the successful containment of potential environmental reservoirs of P. aeruginosa within the premises.

Genomic Analysis of a Hospital-Associated Outbreak of Mycobacterium abscessus: Implications on Transmission.

Whole-genome sequencing (WGS) has recently been used to investigate acquisition of Mycobacterium abscessus. Investigators have reached conflicting conclusions about the meaning of genetic distances for interpretation of person-to-person transmission. Existing genomic studies were limited by a lack of WGS from environmental M. abscessus isolates. In this study, we retrospectively analyzed the core and accessory genomes of 26 M. abscessus subsp. abscessus isolates collected over 7 years. Clinical isolates (n = 22) were obtained from a large hospital-associated outbreak of M. abscessus subsp. abscessus, the outbreak hospital before or after the outbreak, a neighboring hospital, and two outside laboratories. Environmental M. abscessus subsp. abscessus isolates (n = 4) were obtained from outbreak hospital water outlets. Phylogenomic analysis of study isolates revealed three clades with pairwise genetic distances ranging from 0 to 135 single-nucleotide polymorphisms (SNPs). Compared to a reference environmental outbreak isolate, all seven clinical outbreak isolates and the remaining three environmental isolates had highly similar core and accessory genomes, differing by up to 7 SNPs and a median of 1.6% accessory genes, respectively. Although genomic comparisons of 15 nonoutbreak clinical isolates revealed greater heterogeneity, five (33%) isolates had fewer than 20 SNPs compared to the reference environmental isolate, including two unrelated outside laboratory isolates with less than 4% accessory genome variation. Detailed genomic comparisons confirmed environmental acquisition of outbreak isolates of M. abscessus subsp. abscessus. SNP distances alone, however, did not clearly differentiate the mechanism of acquisition of outbreak versus nonoutbreak isolates. We conclude that successful investigation of M. abscessus subsp. abscessus clusters requires molecular and epidemiologic components, ideally complemented by environmental sampling.