Pseudooutbreak of rapidly growing mycobacteria due to Mycobacterium abscessus subsp bolletii in a digestive and respiratory endoscopy unit caused by the same clone as that of a countrywide outbreak

Sources, transmission and hospital-associated outbreaks of nontuberculous mycobacteria: a review

Nontuberculous mycobacteria (NTM) are widespread environmental organisms found in both natural and man-made settings, such as building plumbing, water distribution networks and hospital water systems. Their ubiquitous presence increases the risk of transmission, leading to a wide range of human infections, particularly in immunocompromised individuals. NTM primarily spreads through environmental exposures, such as inhaling aerosolized particles, ingesting contaminated food and introducing it into wounds. Hospital-associated outbreaks have been linked to contaminated medical devices and water systems. Furthermore, the rising global incidence, prevalence and isolation rates highlight the urgency of addressing NTM infections. Gaining a thorough insight into the sources and epidemiology of NTM infection is crucial for devising novel strategies to prevent and manage NTM transmission and infections.

Bronchoscopy-related outbreaks and pseudo-outbreaks: A systematic review

OBJECTIVE

To identify and report the pathogens and sources of contamination associated with bronchoscopy-related outbreaks and pseudo-outbreaks.

DESIGN

Systematic review.

SETTING

Inpatient and outpatient outbreaks and pseudo-outbreaks after bronchoscopy.

METHODS

PubMed/Medline databases were searched according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, using the search terms "bronchoscopy," "outbreak," and "pseudo-outbreak" from inception until December 31, 2022. From eligible publications, data were extracted regarding the type of event, pathogen involved, and source of contamination. Pearson correlation was used to identify correlations between variables.

RESULTS

In total, 74 studies describing 23 outbreaks and 52 pseudo-outbreaks were included in this review. The major pathogens identified in these studies were Pseudomonas aeruginosa, Mycobacterium tuberculosis, nontuberculous mycobacteria (NTM), Klebsiella pneumoniae, Serratia marcescens, Stenotrophomonas maltophilia, Legionella pneumophila, and fungi. The primary sources of contamination were the use of contaminated water or contaminated topical anesthetics, dysfunction and contamination of bronchoscopes or automatic endoscope reprocessors, and inadequate disinfection of the bronchoscopes following procedures. Correlations were identified between primary bronchoscope defects and the identification of P. aeruginosa (r = 0.351; P = .002) and K. pneumoniae (r = 0.346; P = .002), and between the presence of a contaminated water source and NTM (r = 0.331; P = .004) or L. pneumophila (r = 0.280; P = .015).

CONCLUSIONS

Continued vigilance in bronchoscopy disinfection practices remains essential because outbreaks and pseudo-outbreaks continue to pose a significant risk to patient care, emphasizing the importance of stringent disinfection and quality control measures.

Non-tuberculous mycobacteria hybridisation profiles in the GenoType MTBDRplus assay: experience from a diagnostic routine of a high-throughput laboratory

Introduction. Disease caused by non-tuberculous mycobacteria (NTM) is an emergent problem. Because NTM pulmonary disease and tuberculosis (TB) have similar clinical presentations, many cases of NTM may be misdiagnosed as TB before laboratory identification of the NTM species.Hypothesis/Gap Statement. Clinical laboratories should always perform differentiation between Mycobacterium tuberculosis complex (MTBC) and NTM to guide patients' correct treatment.Aim. To describe the characteristics and to identify mycobacterial isolates presumptively classified as MTBC by macroscopic characteristics in culture media that tested negative in GenoType MTBDRplus.Methodology. All cultures from February 2019 to December 2021 showing MTBC macroscopic characteristics were processed by GenoType MTBDRplus. MTBC-negative cultures underwent species identification by immunochromatography, line probe assays and PRA-hsp65. Patients' data were obtained from Brazilian surveillance systems.Results. Only 479 (3.1%) of 15 696 isolates presumptively identified as MTBC were not confirmed by GenoType MTBDRplus and were then subjected to identification. A total of 344 isolates were shown to be NTM, of which 309 (64.5%) and 35 (7.3%) were identified to the species and genus levels, respectively. Of the 204 NTM isolates with MTBC characteristics, the most frequent species were M. fortuitum (n=52, 25.5%), M. abscessus complex (MABC; n=27, 13.2%) and M. avium complex (MAC; n=26, 12.7%). Regarding the GenoType MTBDRplus results from NTM isolates, there were diverse hybridisation profiles with rpoB gene's different wild-type (WT) probes. Seventy-six (16.1%) of the 473 patients were classified as having NTM disease, the most frequent being MAC (n=15, 19.7%), MABC (n=13, 17.1%), M. kansasii (n=10, 13.2%) and M. fortuitum (n=6, 7.9%).Conclusion. Because the signs and symptoms of pulmonary TB are similar to those of pulmonary mycobacteriosis and treatment regimens for TB and NTM are different, identifying the disease-causing species is paramount to indicate the correct management. Thus, in the laboratory routine, when an isolate presumptively classified as MTBC is MTBC-negative, it is still essential to perform subsequent identification.

Pseudo-outbreak of Mycobacterium lentiflavum at a general hospital in Japan

BACKGROUND

Mycobacterium lentiflavum is a slow-growing nontuberculous mycobacterium that is widely distributed in soil and water systems, but it is sometimes pathogenic to humans. Although cases of M. lentiflavum infections are rare, 22 isolates of M. lentiflavum were identified at a single hospital in Japan. We suspected a nosocomial outbreak; thus, we conducted transmission pattern and genotype analyses.

METHODS

Cases of M. lentiflavum isolated at Kushiro City General Hospital in Japan between May 2020 and April 2021 were analyzed. The patient samples and environmental culture specimens underwent whole-genome sequencing (WGS). Additionally, we retrospectively collected clinical data from patient medical records.

RESULTS

Altogether, 22 isolates of M. lentiflavum were identified from sputum and bronchoalveolar lavage samples. Clinically, the instances with M. lentiflavum isolates were considered contaminants. In the WGS analysis, 19 specimens, including 18 patient samples and 1 environmental culture from the hospital's faucet, showed genetic similarity. The frequency of M. lentiflavum isolation decreased after we prohibited the use of taps where M. lentiflavum was isolated.

CONCLUSIONS

WGS analysis identified that the cause of M. lentiflavum pseudo-outbreak was the water used for patient examinations, including bronchoscopy.

Development of multiplex real-time PCR for detection of clarithromycin resistance genes for the Mycobacterium abscessus group

Introduction. The M. abscessus molecular identification and its drug-resistance profile are important to choose the correct therapy.Aim. This work developed a multiplex real-time PCR (mqPCR) for detection of clarithromycin resistance genes for the Mycobacterium abscessus group.Methodology. Isolates received by Adolfo Lutz Institute from 2010 to 2012, identified by PCR restriction enzyme analysis of a fragment of the hsp65 gene (PRA-hsp65) as M. abscessus type 1 (n=135) and 2 (n=71) were used. Drug susceptibility test (DST) for CLA were performed with reading on days 3 and 14. Subespecies identification by hsp65 and rpoB genes sequencing and erm(41) and rrl genes for mutation detection and primer design were performed. erm(41) gene deletion was detected by conventional PCR. Primers and probes were designed for five detections: erm(41) gene full size and with deletion; erm(41) gene T28 and C28; rrl gene A2058.Results. In total, 191/206 (92.7 %) isolates were concordant by all methods and 13/206 (6.3 %) were concordant only between molecular methods. Two isolates (1.0 %) were discordant by mqPCR compared to rrl gene sequencing. The mqPCR obtained 204/206 (99.0 %) isolates in agreement with the gold standard, with sensitivity and specificity of 98 and 100 %, respectively, considering the gold standard method and 92 and 93 % regarding DST.Conclusion. The mqPCR developed by us proved to be an easy-to-apply tool, minimizing time, errors and contamination.

Mycobacterium abscessus Cluster in Cardiac Surgery Patients Potentially Attributable to a Commercial Water Purification System

BACKGROUND

Nontuberculous mycobacteria are water-avid pathogens that are associated with nosocomial infections.

OBJECTIVE

To describe the analysis and mitigation of a cluster of Mycobacterium abscessus infections in cardiac surgery patients.

DESIGN

Descriptive study.

SETTING

Brigham and Women's Hospital, Boston, Massachusetts.

PARTICIPANTS

Four cardiac surgery patients.

INTERVENTION

Commonalities among cases were sought, potential sources were cultured, patient and environmental specimens were sequenced, and possible sources were abated.

MEASUREMENTS

Description of the cluster, investigation, and mitigation.

RESULTS

Whole-genome sequencing confirmed homology among clinical isolates. Patients were admitted during different periods to different rooms but on the same floor. There were no common operating rooms, ventilators, heater-cooler devices, or dialysis machines. Environmental cultures were notable for heavy mycobacterial growth in ice and water machines on the cluster unit but little or no growth in ice and water machines in the hospital's other 2 inpatient towers or in shower and sink faucet water in any of the hospital's 3 inpatient towers. Whole-genome sequencing confirmed the presence of a genetically identical element in ice and water machine and patient specimens. Investigation of the plumbing system revealed a commercial water purifier with charcoal filters and an ultraviolet irradiation unit leading to the ice and water machines in the cluster tower but not the hospital's other inpatient towers. Chlorine was present at normal levels in municipal source water but was undetectable downstream from the purification unit. There were no further cases after high-risk patients were switched to sterile and distilled water, ice and water machine maintenance was intensified, and the commercial purification system was decommissioned.

LIMITATION

Transmission pathways were not clearly characterized.

CONCLUSION

Well-intentioned efforts to modify water management systems may inadvertently increase infection risk for vulnerable patients.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Delineating Mycobacterium abscessus population structure and transmission employing high-resolution core genome multilocus sequence typing

Mycobacterium abscessus is an emerging multidrug-resistant non-tuberculous mycobacterium that causes a wide spectrum of infections and has caused several local outbreaks worldwide. To facilitate standardized prospective molecular surveillance, we established a novel core genome multilocus sequence typing (cgMLST) scheme. Whole genome sequencing data of 1991 isolates were employed to validate the scheme, re-analyze global population structure and set genetic distance thresholds for cluster detection and taxonomic identification. We confirmed and amended the nomenclature of the main dominant circulating clones and found that these also correlate well with traditional 7-loci MLST. Dominant circulating clones could be linked to a corresponding reference genome with less than 250 alleles while 99% of pairwise comparisons between epidemiologically linked isolates were below 25 alleles and 90% below 10 alleles. These thresholds can be used to guide further epidemiological investigations. Overall, the scheme will help to unravel the apparent global spread of certain clonal complexes and as yet undiscovered transmission routes.

A Comparison of Three Culture Media for the Detection of Rapid-Growing Nontuberculous Mycobacteria in Environmental Samples

Nontuberculous mycobacteria (NTM) are common in the environment and certain species can cause serious infections. Improved environmental surveillance methods are needed to combat the increased incidence of NTM disease. Recently, two methods were developed to improve NTM detection. The MYChrOme™ Culture Plate (patent-pending, Phigenics, LLC, Reno, NV, USA) is the first chromogenic medium for rapid-growing NTM detection in water samples. NTM Elite agar (Biomerieux, Marcy-l’Étoile, France), was developed for rapid-growing NTM detection in clinical samples. Fifty water samples (25 potable and 25 non-potable) with three technical replicates were analyzed by each method and Middlebrook 7H11 selective medium (7H11S) (ASTM E2563-07 method modified for water). The MYChrOme method was overall equivalent to or better than 7H11S medium and NTM Elite agar for the detection of rapid-growing NTM in potable water. All three methods detected similar amounts of NTM in non-potable water samples. The chromogenic property of MYChrOme allowed NTM colonies to be quickly identified and differentiated from other bacteria. Additional analysis is required for colony confirmation on 7H11S medium and NTM Elite agar. The use of innovative environmental NTM diagnostics, in addition to proper water management, can greatly reduce the risk of NTM disease.

Virulence Mechanisms of Mycobacterium abscessus: Current Knowledge and Implications for Vaccine Design

Mycobacterium abscessus is a member of the non-tuberculous mycobacteria (NTM) group, responsible for chronic infections in individuals with cystic fibrosis (CF) or those otherwise immunocompromised. While viewed traditionally as an opportunistic pathogen, increasing research into M. abscessus in recent years has highlighted its continued evolution into a true pathogen. This is demonstrated through an extensive collection of virulence factors (VFs) possessed by this organism which facilitate survival within the host, particularly in the harsh environment of the CF lung. These include VFs resembling those of other Mycobacteria, and non-mycobacterial VFs, both of which make a notable contribution in shaping M. abscessus interaction with the host. Mycobacterium abscessus continued acquisition of VFs is cause for concern and highlights the need for novel vaccination strategies to combat this pathogen. An effective M. abscessus vaccine must be suitably designed for target populations (i.e., individuals with CF) and incorporate current knowledge on immune correlates of protection against M. abscessus infection. Vaccination strategies must also build upon lessons learned from ongoing efforts to develop novel vaccines for other pathogens, particularly Mycobacterium tuberculosis (M. tb); decades of research into M. tb has provided insight into unconventional and innovative vaccine approaches that may be applied to M. abscessus. Continued research into M. abscessus pathogenesis will be critical for the future development of safe and effective vaccines and therapeutics to reduce global incidence of this emerging pathogen.

Bronchoscopist's perception of the quality of the single-use bronchoscope (Ambu aScope4™) in selected bronchoscopies: a multicenter study in 21 Spanish pulmonology services

BACKGROUND

The disposable bronchoscope is an excellent alternative to face the problem of SARS-CoV-2 and other cross infections, but the bronchoscopist's perception of its quality has not been evaluated.

METHODS

To evaluate the quality of the Ambu-aScope4 disposable bronchoscope, we carried out a cross-sectional study in 21 Spanish pulmonology services. We use a standardized questionnaire completed by the bronchoscopists at the end of each bronchoscopy. The variables were described with absolute and relative frequencies, measures of central tendency and dispersion depending on their nature. The existence of learning curves was evaluated by CUSUM analysis.

RESULTS

The most frequent indications in 300 included bronchoscopies was bronchial aspiration in 69.3% and the median duration of these was 9.1 min. The route of entry was nasal in 47.2% and oral in 34.1%. The average score for ease of use, image, and aspiration quality was 80/100. All the planned techniques were performed in 94.9% and the bronchoscopist was satisfied in 96.6% of the bronchoscopies. They highlighted the portability and immediacy of the aScope4TM to start the procedure in 99.3%, the possibility of taking and storing images in 99.3%. The CUSUM analysis showed average scores > 70/100 from the first procedure and from the 9th procedure more than 80% of the scores exceeded the 80/100 score.

CONCLUSIONS

The aScope4™ scored well for ease of use, imaging, and aspiration. We found a learning curve with excellent scores from the 9th procedure. Bronchoscopists highlighted its portability, immediacy of use and the possibility of taking and storing images.

Mycobacterium abscessus Infection after Breast Lipotransfer: A Report of 2 Cases

Mycobacterium abscessus is a rare, non-tuberculous, rapidly growing mycobacterium. Although it has been usually associated with chronic pulmonary infections in cystic fibrosis patients, the second most frequent infection sites are the skin and subcutaneous tissue. Most of the cutaneous infections described in the literature occur secondary to cosmetic invasive procedures, many of them in the context of medical tourism. Its atypical presentation and antibiotic-resistant nature make its diagnosis and therapeutics challenging. In this case report, we present 2 cases of M. abscessus infections secondary to breast lipotransfer reported in the same private center. Case 1 patient underwent surgery to treat scar contracture resulting from previous quadrantectomy. Case 2 patient underwent breast augmentation with lipotransfer. Both of them developed lesions in the breast and in the donor site (abdomen). The therapeutic regimen used was amikacin (1 g/24 h) + tigecycline (50 mg/12 h). In case 1, we performed a simple mastectomy, and in case 2, periodical ultrasound-guided drainages were performed as additional procedures. To our knowledge, these are the first 2 cases that describe an infection secondary to breast lipotransfer. The aim of our report was to illustrate the presentation, diagnosis, therapeutic management, and strategies available to prevent this complication.

Pseudo-outbreak of Mycobacterium fortuitum in a hospital bronchoscopy unit

BACKGROUND

Mycobacterium fortuitum survive in different environmental conditions, biofilm formation and resistance to chlorinated disinfectants makes its isolation frequent in hospital environments, even being involved in outbreaks by contamination of medical equipment such as bronchoscopes. We describe a pseudo-outbreak by M fortuitum isolated in samples from 9 patients who underwent bronchoscopy in the pneumology bronchoscopy unit of the University Hospital Complex of the Canary Islands from December 2016 to March 2017.

METHODS

We proceeded to investigate the pseudo-outbreak with a combination of epidemiologic, environmental, and molecular typing data.

RESULTS

The source/reservoir of pseudo-outbreak was the hospital water used by the bronchoscope automatic washing machine (without antibacterial filter), so control measures were taken. Molecular typing was performed on 7 strains from 7 patients, and a sample of water was collected from a tap in the pneumology bronchoscopy unit: all of which had the same pattern.

CONCLUSIONS

Our study demonstrates the presence of nontuberculous mycobacteria in the hospital water supply, and thus the need to take measures against them because they compromise patients' health. We also suggest the need for hospital water quality guidelines in which methods to control and/or eliminate them are established.

A systematic review and cost effectiveness analysis of reusable vs. single-use flexible bronchoscopes

The cost effectiveness of reusable vs. single‐use flexible bronchoscopy in the peri‐operative setting has yet to be determined. We therefore aimed to determine this and hypothesised that single‐use flexible bronchoscopes are cost effective compared with reusable flexible bronchoscopes. We conducted a systematic review of the literature, seeking all reports of cross‐contamination or infection following reusable bronchoscope use in any clinical setting. We calculated the incidence of these outcomes and then determined the cost per patient of treating clinical consequences of bronchoscope‐induced infection. We also performed a micro‐costing analysis to quantify the economics of reusable flexible bronchoscopes in the peri‐operative setting from a high‐throughput tertiary centre. This produced an accurate estimate of the cost per use of reusable flexible bronchoscopes. We then performed a cost effectiveness analysis, combining the data obtained from the systematic review and micro‐costing analysis. We included 16 studies, with a reported incidence of cross‐contamination or infection of 2.8%. In the micro‐costing analysis, the total cost per use of a reusable flexible bronchoscope was calculated to be £249 sterling. The cost per use of a single‐use flexible bronchoscope was £220 sterling. The cost effectiveness analysis demonstrated that reusable flexible bronchoscopes have a cost per patient use of £511 sterling due to the costs of treatment of infection. The findings from this study suggest benefits from the use of single‐use flexible bronchoscopes in terms of cost effectiveness, cross‐contamination and resource utilisation.

Top Questions in the Diagnosis and Treatment of Pulmonary M. abscessus Disease

Mycobacterium abscessus disease is particularly challenging to treat, given the intrinsic drug resistance of this species and the limited data on which recommendations are based, resulting in a greater reliance on expert opinion. We address several commonly encountered questions and management considerations regarding pulmonary Mycobacterium abscessus disease, including the role of subspecies identification, diagnostic criteria for determining disease, interpretation of drug susceptibility test results, approach to therapy including the need for parenteral antibiotics and the role for new and repurposed drugs, and the use of adjunctive strategies such as airway clearance and surgical resection.

Global Environmental Nontuberculous Mycobacteria and Their Contemporaneous Man-Made and Natural Niches

Seminal microbiological work of environmental nontuberculous mycobacteria (NTM) includes the discovery that NTM inhabit water distribution systems and soil, and that the species of NTM found are geographically diverse. It is likely that patients acquire their infections from repeated exposures to their environments, based on the well-accepted paradigm that water and soil bioaerosols - enriched for NTM - can be inhaled into the lungs. Support comes from reports demonstrating NTM isolated from the lungs of patients are genetically identical to NTM found in their environment. Well documented sources of NTM include peat-rich soils, natural waters, drinking water, hot water heaters, refrigerator taps, catheters, and environmental amoeba. However, NTM have also been recovered in biofilms from ice machines, heated nebulizers, and heater-cooler units, as well as seat dust from theaters, vacuum cleaners, and cobwebs. New studies on the horizon aim to significantly expand the current knowledge of environmental NTM niches in order to improve our current understanding of the specific ecological factors driving the emergence of NTM lung disease. Specifically, the Hawaiian Island environment is currently being studied as a model to identify other point sources of exposure as it is the U.S. state with the highest number of NTM lung disease cases. Because of its geographic isolation and unique ecosystem, the Hawaiian environment is being probed for correlative factors that may promote environmental NTM colonization.

The Clarithromycin Susceptibility Genotype Affects the Treatment Outcome of Patients with Mycobacterium abscessus Lung Disease

Mycobacterium abscessus accounts for a large proportion of lung disease cases caused by rapidly growing mycobacteria. The association between clarithromycin sensitivity and treatment outcome is clear. However, M. abscessus culture and antibiotic susceptibility testing are time-consuming. Clarithromycin susceptibility genotyping offers an alternate, rapid approach to predicting the efficacy of clarithromycin-based antibiotic therapy. M. abscessus lung disease patients were divided into two groups based upon the clarithromycin susceptibility genotype of the organism isolated. A retrospective analysis was conducted to compare the clinical features, microbiological characteristics, and treatment outcomes of the two groups. Several other potential predictors of the response to treatment were also assessed. Sixty-nine patients were enrolled in the clarithromycin-resistant genotype group, which included 5 infected with rrl 2058-2059 mutants and 64 infected with erm(41)T28-type M. abscessus; 31 were in the clarithromycin-sensitive group, i.e., 6 and 25 patients infected with genotypes erm(41)C28 and erm(41) M type, respectively. The results showed that lung disease patients infected with clarithromycin-sensitive and -resistant M. abscessus genotypes differed significantly in clarithromycin-based combination treatment outcomes. Patients infected with the clarithromycin-sensitive genotype exhibited higher initial and final sputum-negative conversion and radiological improvement rates and better therapeutic outcomes. Multivariate analysis demonstrated that genotyping was a reliable and, more importantly, rapid means of predicting the efficacy of clarithromycin-based antibiotic treatment for M. abscessus lung disease.

Infections and outbreaks of nontuberculous mycobacteria in hospital settings

Purpose of review

Non-tuberculous mycobacterial [NTM] infections in the hospital setting are a complex and often challenging entity. The goal of this review is to discuss diagnostic and treatment strategies for established as well as emerging nosocomial NTM infections.

Recent findings

NTM outbreaks have been documented in a variety of hospital settings. Contamination of medical devices or aqueous solutions is often implicated in the spread of infection. More recently, the slow grower M. chimaera has been reported in the setting of contaminated heater-cooler devices used for cardiopulmonary bypass and extracorporeal membrane oxygenation. In addition, increases in medical tourism for cosmetic surgery have led to outbreaks of rapidly growing mycobacteria.

Summary

Diagnosis and treatment of nosocomial NTM pose many challenges for the clinician. Surgical resection or debridement as well as combination antimycobacterial therapy are a mainstay in therapeutic management. Strict infection control and prevention practices are critical to the identification and cessation of outbreaks.

Diagnostics and laboratory role in outbreaks

PURPOSE OF REVIEW

The review describes the investigative benefits of traditional and novel molecular epidemiology techniques, while acknowledging the limitations faced by clinical laboratories seeking to implement these methods.

RECENT FINDINGS

Pulse-field gel electrophoresis and other traditional techniques remain powerful tools in outbreak investigations and continue to be used by multiple groups. Newer techniques such as matrix-assisted laser desorption/ionization-time of flight mass-spectrometry and whole genome sequencing show great promise. However, there is a lack of standardization regarding definitions for genetic relatedness, nor are there established criteria for accuracy and reproducibility. There are also challenges regarding availability of trained bioinformatics staff, and concerns regarding reimbursement.

SUMMARY

There are many tools available for molecular epidemiologic investigation. Epidemiologists and clinical laboratorians should work together to determine which testing methods are best for each institution.

Outbreaks of nontuberculous mycobacteria

PURPOSE OF REVIEW

The purpose of this review is to summarize the emerging literature on nontuberculous mycobacteria outbreaks in healthcare settings. As our ability to identify mycobacterial species develops, we are better able to recognize epidemiologic connections and better understand the prevalence and importance of these outbreaks and pseudo-outbreaks in healthcare settings.

RECENT FINDINGS

The number of outbreaks related to nontuberculous outbreaks is increasing because of heightened awareness and better diagnostic tests for species level identification of mycobacteria. Outbreaks in healthcare settings have been related to cardiac surgery, plastic surgery, including medical tourism, colonized humidifiers and heater-cooler devices, imperfect disinfection, and hospital water sources. Mycobacteria have a predilection to form biofilms, are resistant to disinfection and are prevalent in hospital water systems. Patients with structural lung disease like cystic fibrosis patients are at particularly high risk for mycobacterial infection. It has been thought that acquisition in this patient population is from common environmental exposure; however, there is increasing evidence that transmission in this patient population can occur through either direct or indirect patient-to-patient spread.

SUMMARY

Mycobacteria outbreaks in healthcare settings have been underrecognized. As we identify additional clusters of infection with better diagnostic tools and heightened awareness, we will likely need better infection control practices to prevent infections in healthcare settings.

Antagonism between Front-Line Antibiotics Clarithromycin and Amikacin in the Treatment of Mycobacterium abscessus Infections Is Mediated by the whiB7 Gene

Combinations of antibiotics, each individually effective against Mycobacterium abscessus, are routinely coadministered based on the concept that this minimizes the spread of antibiotic resistance. However, our in vitro data contradict this assumption and instead document antagonistic interactions between two antibiotics (clarithromycin and amikacin) used to treat M. abscessus infections. Clinically relevant concentrations of clarithromycin induced increased resistance to both amikacin and itself. The induction of resistance was dependent on whiB7, a transcriptional activator of intrinsic antibiotic resistance that is induced by exposure to many different antibiotics. In M. abscessus, the deletion of whiB7 (MAB_3508c) resulted in increased sensitivity to a broad range of antibiotics. WhiB7 was required for transcriptional activation of genes that confer resistance to three commonly used anti-M. abscessus drugs: clarithromycin, amikacin, and tigecycline. The whiB7-dependent gene that conferred macrolide resistance was identified as erm(41) (MAB_2297), which encodes a ribosomal methyltransferase. The whiB7-dependent gene contributing to amikacin resistance was eis2 (MAB_4532c), which encodes a Gcn5-related N-acetyltransferase (GNAT). Transcription of whiB7 and the resistance genes in its regulon was inducible by subinhibitory concentrations of clarithromycin but not by amikacin. Thus, exposure to clarithromycin, or likely any whiB7-inducing antibiotic, may antagonize the activities of amikacin and other drugs. This has important implications for the management of M. abscessus infections, both in cystic fibrosis (CF) and non-CF patients.

Genomic epidemiology of a national outbreak of post-surgical Mycobacterium abscessus wound infections in Brazil

An epidemic of post-surgical wound infections, caused by a non-tuberculous mycobacterium, has been on-going in Brazil. It has been unclear whether one or multiple lineages are responsible and whether their wide geographical distribution across Brazil is due to spread from a single point source or is the result of human-mediated transmission. 188 isolates, collected from nine Brazilian states, were whole genome sequenced and analysed using phylogenetic and comparative genomic approaches. The isolates from Brazil formed a single clade, which was estimated to have emerged in 2003. We observed temporal and geographic structure within the lineage that enabled us to infer the movement of sub-lineages across Brazil. The genome size of the Brazilian lineage was reduced relative to most strains in the three subspecies of Mycobacterium abscessus and contained a novel plasmid, pMAB02, in addition to the previously described pMAB01 plasmid. One lineage, which emerged just prior to the initial outbreak, is responsible for the epidemic of post-surgical wound infections in Brazil. Phylogenetic analysis indicates that multiple transmission events led to its spread. The presence of a novel plasmid and the reduced genome size suggest that the lineage has undergone adaptation to the surgical niche.