Mycobacterium abscessus: an emerging rapid-growing potential pathogen. Review article

Screening of Preselected Libraries Targeting Mycobacterium abscessus for Drug Discovery

Mycobacterium abscessus is intrinsically resistant to many antimycobacterial antibiotics, which presents serious problems in therapy. Here, we describe the development of a novel phenotype-based microscopic and computerized imaging drug screening approach. A pilot screen of 568 compounds from two libraries identified 17 hits. Eleven of these compounds are described for the first time as active against M. abscessus The impact of growth media on the activity of these compounds was tested, revealing that cation-adjusted Mueller-Hinton broth (MHII) supports better growth of actively replicating M. abscessus and improves the activity of associated compounds.

Mycobacterium abscessus subspecies massiliense infection after skin graft and cholecystectomy in a burn patient

Diagnosing skin and soft tissue infections due to rapidly growing mycobacteria (RGM) can often prove difficult, leading to delays in treatment. Postoperative infections caused by RGM are increasingly recognized both within and outside the USA, but are rarely encountered in burn units. We report a case of postoperative skin and soft tissue infection along a cholecystectomy incision in a burn patient caused by Mycobacterium abscessus subsp. massiliense. Postoperative infections caused by RGM require a high index of suspicion, often necessitating biopsy for definitive diagnosis. Physicians should consider this diagnosis when postoperative infections arise later than typically seen for routine bacterial infections and fail to respond to first-line therapy.

Mycobacterium abscessus subsp. massiliense mycma_0076 and mycma_0077 Genes Code for Ferritins That Are Modulated by Iron Concentration

Mycobacterium abscessus complex has been characterized in the last decade as part of a cluster of mycobacteria that evolved from an opportunistic to true human pathogen; however, the factors responsible for pathogenicity are still undefined. It appears that the success of mycobacterial infection is intrinsically related with the capacity of the bacteria to regulate intracellular iron levels, mostly using iron storage proteins. This study evaluated two potential M. abscessus subsp. massiliense genes involved in iron storage. Unlike other opportunist or pathogenic mycobacteria studied, M. abscessus complex has two genes similar to ferritins from M. tuberculosis (Rv3841), and in M. abscessus subsp. massiliense, those genes are annotated as mycma_0076 and mycma_0077. Molecular dynamic analysis of the predicted expressed proteins showed that they have a ferroxidase center. The expressions of mycma_0076 and mycma_0077 genes were modulated by the iron levels in both in vitro cultures as well as infected macrophages. Structural studies using size-exclusion chromatography, circular dichroism spectroscopy and dynamic light scattering showed that r0076 protein has a structure similar to those observed in the ferritin family. The r0076 forms oligomers in solution most likely composed of 24 subunits. Functional studies with recombinant proteins, obtained from heterologous expression of mycma_0076 and mycma_0077 genes in Escherichia coli, showed that both proteins were capable of oxidizing Fe2+ into Fe3+, demonstrating that these proteins have a functional ferroxidase center. In conclusion, two ferritins proteins were shown, for the first time, to be involved in iron storage in M. abscessus subsp. massiliense and their expressions were modulated by the iron levels.

Multistate US Outbreak of Rapidly Growing Mycobacterial Infections Associated with Medical Tourism to the Dominican Republic, 2013-2014(1)

Infections in 6 states were linked to persons traveling to undergo cosmetic surgical procedures.

During 2013, the Maryland Department of Health and Mental Hygiene in Baltimore, MD, USA, received report of 2 Maryland residents whose surgical sites were infected with rapidly growing mycobacteria after cosmetic procedures at a clinic (clinic A) in the Dominican Republic. A multistate investigation was initiated; a probable case was defined as a surgical site infection unresponsive to therapy in a patient who had undergone cosmetic surgery in the Dominican Republic. We identified 21 case-patients in 6 states who had surgery in 1 of 5 Dominican Republic clinics; 13 (62%) had surgery at clinic A. Isolates from 12 (92%) of those patients were culture-positive for Mycobacterium abscessus complex. Of 9 clinic A case-patients with available data, all required therapeutic surgical intervention, 8 (92%) were hospitalized, and 7 (78%) required ≥3 months of antibacterial drug therapy. Healthcare providers should consider infection with rapidly growing mycobacteria in patients who have surgical site infections unresponsive to standard treatment.

A temperature sensitive Mycobacterium paragordonae induces enhanced protective immune responses against mycobacterial infections in the mouse model

Recently, we introduced a temperature sensitive Mycobacterium spp., Mycobacterium paragordonae (Mpg). Here, we checked its potential as a candidate for live vaccination against Mycobacterium tuberculosis and Mycobacterium abscessus. Intravenous infections of mice with Mpg led to lower colony forming units (CFUs) compared to infection with BCG, suggesting its usefulness as a live vaccine. The analyses of immune responses indicated that the highly protective immunity elicited by Mpg was dependent on effective dendritic maturation, shift of cytokine patterns and antibody production toward a Th1 phenotype, and enhanced cytotoxic T cell response. Compared to BCG, Mpg showed a more effective protective immune response in the vaccinated mice against challenges with 2 different mycobacterial strains, M. tuberculosis H37Ra or M. abscessus Asan 50594. Our data suggest that a temperature sensitive Mpg may be a potentially powerful candidate vaccine strain to induce enhanced protective immune responses against M. tuberculosis and M. abscessus.

New Insights in to the Intrinsic and Acquired Drug Resistance Mechanisms in Mycobacteria

Infectious diseases caused by clinically important Mycobacteria continue to be an important public health problem worldwide primarily due to emergence of drug resistance crisis. In recent years, the control of tuberculosis (TB), the disease caused by Mycobacterium tuberculosis (MTB), is hampered by the emergence of multidrug resistance (MDR), defined as resistance to at least isoniazid (INH) and rifampicin (RIF), two key drugs in the treatment of the disease. Despite the availability of curative anti-TB therapy, inappropriate and inadequate treatment has allowed MTB to acquire resistance to the most important anti-TB drugs. Likewise, for most mycobacteria other than MTB, the outcome of drug treatment is poor and is likely related to the high levels of antibiotic resistance. Thus, a better knowledge of the underlying mechanisms of drug resistance in mycobacteria could aid not only to select the best therapeutic options but also to develop novel drugs that can overwhelm the existing resistance mechanisms. In this article, we review the distinctive mechanisms of antibiotic resistance in mycobacteria.

In vitro biological evaluation of new antimycobacterial salicylanilide-tuftsin conjugates

Tuberculosis is caused by Mycobacterium tuberculosis, an intracellular pathogen that can survive in host cells, mainly in macrophages. An increase of multidrug-resistant tuberculosis qualifies this infectious disease as a major public health problem worldwide. The cellular uptake of the antimycobacterial agents by infected host cells is limited. Our approach is to enhance the cellular uptake of the antituberculars by target cell-directed delivery using drug-peptide conjugates to achieve an increased intracellular efficacy. In this study, salicylanilide derivatives (2-hydroxy-N-phenylbenzamides) with remarkable antimycobacterial activity were conjugated to macrophage receptor specific tuftsin based peptide carriers through oxime bond directly or by insertion of a GFLG tetrapeptide spacer. We have found that the in vitro antimycobacterial activity of the salicylanilides against M. tuberculosis H₃₇Rv is preserved in the conjugates. While the free drug was ineffective on infected macrophage model, the conjugates were active against the intracellular bacteria. The fluorescently labelled peptide carriers that were modified with different fatty acid side chains showed outstanding cellular uptake rate to the macrophage model cells. The conjugation of the salicylanilides to tuftsin based carriers reduced or abolished the in vitro cytostatic activity of the free drugs with the exception of the palmitoylated conjugates. The conjugates degraded in the presence of rat liver lysosomal homogenate leading to the formation of an oxime bond-linked salicylanilide-amino acid fragment as the smallest active metabolite.

Antimicrobial susceptibility testing of rapidly growing mycobacteria isolated in Japan

Background

Difficult-to-treat infections caused by rapidly growing mycobacteria (RGM) are increasingly observed in clinical settings. However, studies on antimicrobial susceptibilities and effective treatments against RGM in Japan are limited.

Methods

We conducted susceptibility testing of potential antimicrobial agents, including tigecycline and tebipenem, against RGM. Clinical RGM isolates were collected from a university hospital in Japan between December 2010 and August 2013. They were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and the sequencing of 16S rRNA, rpoB, and hsp65 genes. The samples were utilized for susceptibility testing using 16 antimicrobials, with frozen broth microdilution panels.

Results

Forty-two isolates were obtained: 13, Mycobacterium abscessus complex; 12, Mycobacterium chelonae; 9, Mycobacterium fortuitum; and 8, M. fortuitum group species other than M. fortuitum. Different antimicrobial susceptibility patterns were observed between RGM species. Clarithromycin-susceptible strain rates were determined to be 0, 62, and 100% for M. fortuitum, M. abscessus complex, and M. chelonae, respectively. M. abscessus complex (100%) and >80% M. chelonae isolates were non-susceptible, while 100% M. fortuitum group isolates were susceptible to moxifloxacin. Linezolid showed good activity against 77% M. abscessus complex, 89% M. fortuitum, and 100% M. chelonae isolates. Regardless of species, all tested isolates were inhibited by tigecycline at very low minimal inhibitory concentrations (MICs) of ≤0.5 μg/mL. MICs of tebipenem, an oral carbapenem, were ≤4 μg/mL against all M. fortuitum group isolates.

Conclusions

Our study demonstrates the importance of correct identification and antimicrobial susceptibility testing, including the testing of potential new agents, in the management of RGM infections.

Granulomatous Lobular Mastitis Associated with Mycobacterium abscessus in South China: A Case Report and Review of the Literature

Mycobacteria, which are known as rapidly growing bacteria, are pathogens that are responsible for cutaneous or subcutaneous infections that especially occur after injection, trauma, or surgery. In this report, we describe a species of Mycobacterium abscessus that was isolated from a breast abscess in a patient who was previously diagnosed with granulomatous lobular mastitis (GLM). This current case is the first ever presented case of GLM associated with M. abscessus documented in South China. The case presentation highlights the role of M. abscessus in GLM. The association of M. abscessus and GLM is discussed and a summary of breast infection due to Mycobacteria is given.

Mycobacteria Clumping Increase Their Capacity to Damage Macrophages

The rough morphotypes of non-tuberculous mycobacteria have been associated with the most severe illnesses in humans. This idea is consistent with the fact that Mycobacterium tuberculosis presents a stable rough morphotype. Unlike smooth morphotypes, the bacilli of rough morphotypes grow close together, leaving no spaces among them and forming large aggregates (clumps). Currently, the initial interaction of macrophages with clumps remains unclear. Thus, we infected J774 macrophages with bacterial suspensions of rough morphotypes of M. abscessus containing clumps and suspensions of smooth morphotypes, primarily containing isolated bacilli. Using confocal laser scanning microscopy and electron microscopy, we observed clumps of at least five rough-morphotype bacilli inside the phagocytic vesicles of macrophages at 3 h post-infection. These clumps grew within the phagocytic vesicles, killing 100% of the macrophages at 72 h post-infection, whereas the proliferation of macrophages infected with smooth morphotypes remained unaltered at 96 h post-infection. Thus, macrophages phagocytose large clumps, exceeding the bactericidal capacities of these cells. Furthermore, proinflammatory cytokines and granuloma-like structures were only produced by macrophages infected with rough morphotypes. Thus, the present study provides a foundation for further studies that consider mycobacterial clumps as virulence factors.

Mycobacterium abscessus: causing fatal endocarditis after cardiac catheterization

Mycobacterium abscessus is an unusual cause of infection in immunocompetent patients. The intrinsic and acquired resistance of this organism to multiple antibiotics is a major issue in planning treatment regimens. We report a case of M. abscessus endocarditis of the native aortic valve in an immunocompetent patient following coronary angiography with a fatal outcome. The case highlights an unfortunate intervention – related nosocomial infection and the difficulties in chemotherapeutic options for this organism, particularly in the presence of renal failure.

Gastric lap-band infection due to Mycobacterium abscessus presenting as new-onset ascites in a cirrhotic patient

Nontuberculous mycobacteria are ubiquitous environmental organisms that are infrequently implicated as pathogens. Peritoneal infection with nontuberculous mycobacteria is rare and published reports are most commonly associated with peritoneal dialysis. This study describes a case of a 41-year-old woman with cirrhosis who had Mycobacterium abscessus peritonitis and an abdominal abscess resulting from infection of a remotely placed gastric band (Lap-Band; Apollo Endosurgery, Inc).

Resazurin Microtiter Assay for Clarithromycin Susceptibility Testing of Clinical Isolates of Mycobacterium abscessus Group

BACKGROUND

Mycobacterium abscessus group has heterogeneous susceptibility pattern among species. The species is most common cause of nosocomial infections. Macrolides minimum Inhibitory concentration (MIC) determination is essential for the treatment.

METHODS

Thirty-six strains were randomly selected for performing Resazurin Microtiter Assay (REMA) for clarithromycin testing in comparison to MIC test according to Clinical and Laboratory Standards Institute (2011) recommendation. REMA has been used for detection of drug resistance in M. tuberculosis. Extended incubation was performed to detect induced resistance.

RESULTS

Thirty microliters of resazurin (0.01%) was added after visually taking MIC reading. Resistance was observed in 11.1% of M. bolletti and 4.8% of M. abscessus strains; and induced resistance was detected in 77.8% and 95.2% of M. bolletti and M. abscessus strains, respectively. All strains of M. massiliense were susceptible. The samples presented same MIC value both by visual reading and through resazurin.

CONCLUSION

The present study showed 100% concordance between both readings, with REMA providing easier to read and report results benefit. This change in reading can also reflect on the MIC determination and report, improving the test.

Pacemaker pocket infection due to environmental mycobacteria: Successful management of an outbreak and steps for prevention in future

Background

An outbreak of surgical site infection (SSI) due to environmental mycobacteria (EMB) occurred in a hospital in Eastern India.

Method

A quality improvement project (QIP) was undertaken to analyze the causes and prevent further outbreak. Step (1) Proof of the need: Four patients who had undergone pacemaker implantation consecutively during a 10-day period developed SSI. Step (2) Diagnostic journey: Since all patients developed SSI within 2 months of implantation, a common source of infection was likely. Atypical mycobacteria (AMB) were grown from surgical sites as well as from the surface of operation table, image intensifier, and lead aprons. It was a rapid growing variety that lacked pigment, a characteristic of EMB with pathogenic potential. The EMB was finally traced to its source, the overhead water tank. Step (3) Remedial journey: By thorough cleaning of the water tank and enriching its chlorine content, the EMB was eliminated from its source. Step (4) Holding the gains: Protocol for cleaning the water tank once in 3 months was made. A checklist was prepared to ensure compliance to asepsis protocol in the operation theater. In the ensuing 5 years, the infection did not recur.

Result

The bacteria that caused SSI were identified as EMB that grew in the water tank and contaminated the operation room. It could be eliminated by appropriate measures.

Interpretation

Water is a potential reservoir for EMB. Use of the term ‘environmental mycobacteria’ instead of ‘atypical mycobacteria’ will generate awareness about contamination as the cause of SSI.

High-throughput transcriptomics reveals common and strain-specific responses of human macrophages to infection with Mycobacterium abscessus Smooth and Rough variants

Background

Mycobacterium abscessus (MAB) is an emerging pathogen causing pulmonary infections in those with inflammatory lung disorders, such as Cystic Fibrosis (CF), and is associated with the highest fatality rate among rapidly growing mycobacteria (RGM). Phenotypically, MAB manifests as either a Smooth (MAB-S) or a Rough (MAB-R) morphotype, which differ in their levels of cell wall glycopeptidolipids (GPLs) and in their pathogenicity in vivo. As one of the primary immune cells encountered by MAB, we sought to examine the early transcriptional events within macrophages, following infection with both MAB-S or MAB-R.

Results

We sampled the transcriptomes (mRNA and miRNA) of THP-1-derived macrophages infected with both MAB-R and MAB-S at 1, 4 and 24 h post-infection (hpi) using RNA-seq. A core set of 606 genes showed consistent expression profiles in response to both morphotypes, corresponding to the early transcriptional response to MAB. The core response is type I Interferon (IFN)-driven, involving the NF-κB and MAPK signaling pathways with concomitant pro-inflammatory cytokine production, and network analysis identified STAT1, EGR1, and SRC as key hub and bottleneck genes. MAB-S elicited a more robust transcriptional response at both the mRNA and miRNA levels, which was reflected in higher cytokine levels in culture supernatants. The transcriptional profiles of macrophages infected with both morphotypes were highly correlated, however, and a direct comparison identified few genes to distinguish them. Most of the induced miRNAs have previously been associated with mycobacterial infection and overall miRNA expression patterns were similarly highly correlated between the morphotypes.

Conclusions

The report here details the first whole transcriptome analysis of the early macrophage response to MAB infection. The overall picture at the early stages of macrophage infection is similar to that of other mycobacteria, reflected in a core type I IFN and pro-inflammatory cytokine response. Large-scale transcriptional differences in the host response to the different MAB morphotypes are not evident in the early stages of infection, however the subset of genes with distinct expression profiles suggest potentially interesting differences in internal trafficking of MAB within macrophages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2246-1) contains supplementary material, which is available to authorized users.

In Vitro Antimicrobial Susceptibility of Nontuberculous Mycobacteria in Iran

Many species of nontuberculous mycobacteria (NTM) have long been identified as important causes of human disease, the incidence of which is rising. Several reports have suggested increasing trend of both in vitro and in vivo resistance to available treatment regimes. The aim of this study was to evaluate antibiotic susceptibility of clinically relevant NTM isolates using standard microbroth dilution test. Antimicrobial susceptibility testing was performed following National Committee for Clinical Laboratory Standards methods for NTM isolates, including 85 Mycobacterium fortuitum, 39 Mycobacterium chelonae, and 30 Mycobacterium abscessus subsp. abscessus as rapidly growing mycobacteria and 48 Mycobacterium simiae and 40 Mycobacterium kansasii as slowly growing mycobacteria. All isolates were recovered from various types of clinical samples and identified by multilocus sequence analysis. Trimethoprim-sulfamethoxazole (TMP-SMZ), amikacin, tobramycin, clarithromycin, moxifloxacin, linezolid, and imipenem showed better activity against M. fortuitum rather than meropenem, ciprofloxacin, cefoxitin, and doxycycline. Amikacin was active against 93% of M. abscessus subsp. abscessus. Linezolid, clarithromycin, cefoxitin, ciprofloxacin, imipenem, moxifloxacin, tobramycin, TMP-SMZ, doxycycline, and meropenem showed some activities on M. abscessus subsp. abscessus as well. The majority of M. abscessus subsp. abscessus and M. chelonae strains were multidrug resistant. Among the 40 isolates of M. kansasii, all were susceptible to ethambutol, isoniazid, clarithromycin, moxifloxacin, and linezolid. These isolates were also resistant to doxycycline and 50% were resistant to rifampicin and ciprofloxacin. M. simiae was resistant to clarithromycin, doxycycline, isoniazid, and TMP-SMZ, and the majority of isolates showed high levels of resistance to linezolid, ethambutol, ciprofloxacin, streptomycin, and rifampicin. The majority of M. simiae isolates were multidrug resistant. Our data confirm the need for performing of standard susceptibility testing of any clinically important NTM isolate.

Rapid prediction of inducible clarithromycin resistance in Mycobacterium abscessus

We have developed a single tube TaqMan(®) real-time PCR assay that differentiates the full-length and truncated erm(41) gene to predict inducible resistance to clarithromycin in Mycobacterium abscessus. A study of 87 clinical isolates found this assay to be 90.8% concordant to conventional drug susceptibility testing results for the prediction of inducible clarithromycin drug resistance.

Otomastoiditis caused by non-tuberculous mycobacteria: report of 16 cases, 3 with infection intracranially

Objective:

To analyse the clinical presentation, treatment and outcome in patients diagnosed with otomastoiditis caused by non-tuberculous mycobacteria.

Methods:

A retrospective case review of 16 patients diagnosed with otomastoiditis caused by non-tuberculous mycobacteria from 2000 to 2012 was conducted in a hospital and tertiary referral centre in Sweden. The main outcome measures were microbiology findings, and surgical and medical interventions and outcomes. In addition, the relevant literature was reviewed.

Results:

In three patients with otomastoiditis, the disease had spread intracranially. The bacteriological findings revealed Mycobacterium abscessus (n = 12), Mycobacterium fortuitum (n = 2) and Mycobacterium avium complex (n = 2). Surgical treatment was undertaken in all but three patients, including exploration of the temporal lobe in one patient. Systemic antibiotic treatment was given to all but one patient. Eight patients healed completely. Eight patients developed hearing loss. Two patients had relapse of the mycobacterial infection several months after the antibiotic treatment had been discontinued.

Conclusion:

Non-tuberculous otomastoiditis is a severe ear disease with challenging considerations, and should be treated aggressively in order to avoid morbidity.

Combating highly resistant emerging pathogen Mycobacterium abscessus and Mycobacterium tuberculosis with novel salicylanilide esters and carbamates

In the Mycobacterium genus over one hundred species are already described and new ones are periodically reported. Species that form colonies in a week are classified as rapid growers, those requiring longer periods (up to three months) are the mostly pathogenic slow growers. More recently, new emerging species have been identified to lengthen the list, all rapid growers. Of these, Mycobacterium abscessus is also an intracellular pathogen and it is the most chemotherapy-resistant rapid-growing mycobacterium. In addition, the cases of multidrug-resistant Mycobacterium tuberculosis infection are also increasing. Therefore there is an urgent need to find new active molecules against these threatening strains. Based on previous results, a series of salicylanilides, salicylanilide 5-chloropyrazinoates and carbamates was designed, synthesized and characterised. The compounds were evaluated for their in vitro activity on M. abscessus, susceptible M. tuberculosis H37Rv, multidrug-resistant (MDR) M. tuberculosis MDR A8, M. tuberculosis MDR 9449/2006 and on the extremely-resistant Praha 131 (XDR) strains. All derivatives exhibited a significant activity with minimum inhibitory concentrations (MICs) in the low micromolar range. Eight salicylanilide carbamates and two salicylanilide esters exhibited an excellent in vitro activity on M. abscessus with MICs from 0.2 to 2.1 μM, thus being more effective than ciprofloxacin and gentamicin. This finding is potentially promising, particularly, as M. abscessus is a threateningly chemotherapy-resistant species. M. tuberculosis H37Rv was inhibited with MICs from 0.2 μM, and eleven compounds have lower MICs than isoniazid. Salicylanilide esters and carbamates were found that they were effective also on MDR and XDR M. tuberculosis strains with MICs ≥1.0 μM. The in vitro cytotoxicity (IC50) was also determined on human MonoMac-6 cells, and selectivity index (SI) of the compounds was established. In general, salicylanilide derivatives substituted by halogens on both salicyl and aniline rings showed better activity, than 4-benzoylaniline derivatives. The ester or carbamate bond formation of parent salicylanilides mostly retained or improved antimycobacterial potency with moderate selectivity.

Susceptibility testing of Mycobacterium abscessus by isothermal microcalorimetry

We evaluated a new method for susceptibility testing of a rapidly growing mycobacterium using real-time measurement of heat (microcalorimetry). MICs of 2 clinical Mycobacterium abscessus isolates were determined by microbroth dilution and E-test. For microcalorimetry, Middlebrook-7H10 agar+10% oleic acid-albumin-dextrose-catalase, containing amikacin, clarithromycin, linezolid, and ciprofloxacin was inoculated with ~10(5)CFU/mL. Heat production was measured at 37°C for 72h. Minimal heat inhibition concentration (MHIC) was defined as the lowest antibiotic concentration inhibiting growth-related heat production. Growth of M. abscessus was detected after a median of 16.5h (range, 8.5-26.9h). Heat detection was proportionally delayed with increasing concentration of antibiotics. MHICs for the tested strains were 16 to >16mg/L for amikacin, >8mg/L for clarithromycin, 4 to >16mg/L for ciprofloxacin, 24 to >32mg/L for linezolid. MHICs were in agreement within two 2-fold dilutions with conventional MICs. Microcalorimetry may accelerate antimicrobial susceptibility testing in mycobacteria and provide additional real-time information on the drug effect.

Iatrogenic Mycobacterium abscessus infection in a trigger finger

An immunocompetent 63-year-old lady developed Mycobacterium abscessus soft tissue infection of the hand following local corticosteroid injection for trigger finger. The patient was successfully treated with repeated radical debridement and prolonged antimicrobial therapy. Atypical mycobacterial infections, including those caused by M. abscessus, albeit rare, should be considered in cases of late-onset indolent infection following local injury surgical procedures, and injections. Clinical vigilance, timely diagnosis, combined directed antimicrobial treatment, coupled with adequate surgical debridement are key for successful management.

Microbial indicators, pathogens and methods for their monitoring in water environment

Water is critical for life, but many people do not have access to clean and safe drinking water and die because of waterborne diseases. The analysis of drinking water for the presence of indicator microorganisms is key to determining microbiological quality and public health safety. However, drinking water-related illness outbreaks are still occurring worldwide. Moreover, different indicator microorganisms are being used in different countries as a tool for the microbiological examination of drinking water. Therefore, it becomes very important to understand the potentials and limitations of indicator microorganisms before implementing the guidelines and regulations designed by various regulatory agencies. This review provides updated information on traditional and alternative indicator microorganisms with merits and demerits in view of their role in managing the waterborne health risks as well as conventional and molecular methods proposed for monitoring of indicator and pathogenic microorganisms in the water environment. Further, the World Health Organization (WHO) water safety plan is emphasized in order to develop the better approaches designed to meet the requirements of safe drinking water supply for all mankind, which is one of the major challenges of the 21st century.

Gallium Compounds Exhibit Potential as New Therapeutic Agents against Mycobacterium abscessus

The rapidly growing nontuberculous mycobacterial species Mycobacterium abscessus has recently emerged as an important pathogen in patients with cystic fibrosis (CF). Treatment options are limited because of the organism's innate resistance to standard antituberculous antibiotics, as well as other currently available antibiotics. New antibiotic approaches to the treatment of M. abscessus are urgently needed. The goal of the present study was to assess the growth-inhibitory activity of different Ga compounds against an American Type Culture Collection (ATCC) strain and clinical isolates of M. abscessus obtained from CF and other patients. In our results, using Ga(NO3)3 and all of the other Ga compounds tested inhibited the growth of ATCC 19977 and clinical isolates of M. abscessus. Inhibition was mediated by disrupting iron uptake, as the addition of exogenous iron (Fe) restored basal growth. There were modest differences in inhibition among the isolates for the same Ga chelates, and for most Ga chelates there was only a slight difference in potency from Ga(NO3)3. In contrast, Ga-protoporphyrin completely and significantly inhibited the ATCC strain and clinical isolates of M. abscessus at much lower concentrations than Ga(NO3)3. In in vitro broth culture, Ga-protoporphyrin was more potent than Ga(NO3)3. When M. abscessus growth inside the human macrophage THP-1 cell line was assessed, Ga-protoporphyrin was >20 times more active than Ga(NO3)3. The present work suggests that Ga exhibits potent growth-inhibitory capacity against the ATCC strain, as well as against antibiotic-resistant clinical isolates of M. abscessus, including the highly antibiotic-resistant strain MC2638. Ga-based therapy offers the potential for further development as a novel therapy against M. abscessus.

Mycobacterium abscessus pulmonary infection complicated with vertebral osteomyelitis in a heart transplant recipient: case report and literature review

Infections produced by Mycobacterium abscessus are emerging in immunosuppressed patients, such as solid organ transplant recipients. We report the first case, to our knowledge, of a vertebral osteomyelitis caused by M. abscessus in a heart transplant recipient, and review the risk factors, manifestations, and therapeutic approaches to this uncommon disease.

Induction of heme oxygenase-1 contributes to survival of Mycobacterium abscessus in human macrophages-like THP-1 cells

Mycobacterium abscessus (M.abs) is a rapidly growing mycobacterial species that infects macrophages, and is an important pathogen in patients with cystic fibrosis. We studied the early stages of M.abs infection of macrophages, with emphasis on the role of heme-oxygenase-1 (HO-1) in this infection. THP-1 cells were activated using TPA into macrophage-like cells and infected with M.abs for different time points. M.abs infection robustly induced HO-1 expression in the THP-1 cells. Production of HO-1 was p38 MAPK-dependent, as p38 inhibitors suppressed HO-1 induction. Pretreatment with HO-1 inhibitors tin-protoporphyrin (SnPP) significantly inhibited M.abs growth inside macrophages. Furthermore, inhibiting HO-1 using HO-1 siRNA or the HO-1 upstream signaling molecule; Nrf2 using Nrf2 siRNA resulted in similar inhibition of M.abs. In contrast, inducing HO-1 did not increase M.abs intracellular growth above control. Products of HO-1 metabolism of heme are bilirubin, biliverdin, carbon monoxide (CO) and iron. The addition of either bilirubin or biliverdin, but not CO, completely restored the SnPP inhibitory effect and partially that with HO-1 siRNA. To understand the mechanisms, we used Syto-62 labeled M.abs to infect macrophages. Interestingly, HO-1 inhibition promoted M.abs-containing phagosome fusion with lysosomes, which should enhance M.abs killing. M.abs infection enhanced THP-1 ROS production as demonstrated by increased DHE, DCF fluorescence, and EPR signal. HO-1 inhibition further increased ROS production in infected macrophages. Our results indicate that HO-1 induction is important for M.abs growth during the early stages of infection, and that the HO-1 products bilirubin and biliverdin, perhaps through modulation of intracellular ROS levels, may be involved.

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HO-1 induction is important for Mycobacterium abscessus growth inside infected macrophages during the early stages of infection.

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Reducing HO-1 products may enhance the ability of the macrophage to control Mycobacterium abscessus infection.

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HO-1 inhibition increases phagosome–lysosome fusion and thus Mycobacterium abscessus killing.

Vertebral Osteomyelitis Caused by Mycobacterium abscessus Surgically Treated Using Antibacterial Iodine-Supported Instrumentation

Mycobacterium abscessus infections rarely develop in healthy individuals, and mostly they occur in immunocompromised hosts. Vertebral osteomyelitis due to Mycobacterium abscessus is very rare and only three previous cases of spinal infection caused by Mycobacterium abscessus have been reported. Mycobacterium abscessus isolates are uniformly resistant to antituberculous agents and can display a virulent biofilm-forming phenotype. The patient was a 67-year-old woman with vertebral osteomyelitis of the L1-2. She was healthy without immune-suppressed condition, history of trauma, or intravenous drug use. The smear examination of the specimen harvested by CT-guided puncture of the paravertebral abscess revealed Mycobacterium abscessus. Her disease condition did not abate with conservative treatment using antimicrobial chemotherapy. Radical debridement of the vertebral osteomyelitis and anterior reconstruction from T12 to L2 using antibacterial iodine-supported instrumentation were performed. Chemotherapy using clarithromycin, amikacin, and imipenem was applied for 6 months after surgery as these antibiotics had been proven to be effective to Mycobacterium abscessus after surgery. Two years after surgery, the infected anterior site healed and bony fusion was successfully achieved without a recurrence of infection.

Management of Mycobacterium abscessus post abdominoplasty

Atypical mycobacterium is the source of a recent outbreak of cosmetic surgery infections [1]. Such an infection is difficult to eradicate and presents unique challenges in its management after esthetic surgery. Delays in appropriate treatment are frequent because of difficulty in diagnosis and unfamiliarity with this type of infection. We present cases of our management of Mycobacterial abscessus abdominoplasty infections following cosmetic surgery in the Dominican Republic. Rapid initial recognition of this problem and the frequent need for surgical treatment of atypical mycobacterium abdominoplasty infection may aid in the treatment of this rare but increasingly encountered infection.

LEVEL OF EVIDENCE V

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A rare native mitral valve endocarditis successfully treated after surgical correction

Mycobacterium abscessus and Kocuria species are rare causes of infections in humans. Endocarditis by these agents has been reported in only 11 cases. M. abscessus is a particularly resistant organism and treatment requires the association of antibiotics for a prolonged period of time. We report a case of native mitral valve bacterial endocarditis due to M. abscessus and Kocuria species in a 48-year-old man with a history of intravenous drug use. The case was complicated by a perforation of the posterior mitral valve leaflet, leading to surgical mitral valve replacement. Cultures from the blood and mitral valve disclosed M. abscessus and Kocuria species. The patient was treated for 6 months with clarithromycin, imipenem and amikacin, with resolution of symptoms. Repeated blood cultures were negative. Acid-fast staining should be done in subacute endocarditis in order to identify rapidly growing mycobacteria.

A shorter treatment duration may be sufficient for patients with Mycobacterium massiliense lung disease than with Mycobacterium abscessus lung disease

BACKGROUND

Mycobacterium abscessus complex is the second most common organism isolated from patients with nontuberculous mycobacterial (NTM) lung disease in South Korea. This study aimed to compare clinical features and treatment outcomes of M. abscessus and Mycobacterium massiliense lung disease.

METHODS

We retrospectively identified stored clinical isolates of M. abscessus complex as either M. abscessus or M. massiliense and reviewed medical records to compare clinical characteristics and treatment responses. All patients were treated empirically over several months with multidrug regimens, including a macrolide and one or more parenteral agents.

RESULTS

Of the 249 patient isolates tested, 128 (59 with M. abscessus and 69 with M. massiliense) met the American Thoracic Society diagnostic criteria for NTM pulmonary disease, and treatment outcomes were analyzed in 48 patients (26 with M. abscessus and 22 with M. massiliense). The clinical and radiologic findings were similar between the two groups. Although the durations of parenteral and total treatment were significantly shorter in patients with M. massiliense than in those with M. abscessus (4.7 months vs 7.4 months, P = .006, and 12.1 months vs 16.3 months, P = .043), the treatment success rate was significantly higher in patients with M. massiliense (95.5%) than in M. abscessus cases (42.3%, P < .001).

CONCLUSION

Patients with M. massiliense pulmonary infection responded better to this antibiotic strategy than those with M. abscessus infection. A shortened duration of treatment may be sufficient for M. massiliense pulmonary infection.

Mycobacteriophage-drived diversification of Mycobacterium abscessus

Background

Mycobacterium abscessus is an emerging opportunistic pathogen which diversity was acknowledged by the recent description of two subspecies accommodating M. abscessus, Mycobacterium bolletii and Mycobacterium massiliense isolates.

Results

Here, genome analysis found 1–8 prophage regions in 47/48 M. abscessus genomes ranging from small prophage-like elements to complete prophages. A total of 20,304 viral and phage proteins clustered into 853 orthologous groups. Phylogenomic and phylogenetic analyses based on prophage region homology found three main clusters corresponding to M. abscessus, M. bolletii and M. massiliense. Analysing 135 annotated Tape Measure Proteins found thirteen clusters and four singletons, suggesting that at least 17 mycobacteriophages had infected M. abscessus during its evolution. The evolutionary history of phages differed from that of their mycobacterial hosts. In particular, 33 phage-related proteins have been horizontally transferred within M. abscessus genomes. They comprise of an integrase, specific mycobacteriophage proteins, hypothetical proteins and DNA replication and metabolism proteins. Gene exchanges, loss and gains which occurred in M. abscessus genomes have been driven by several mycobacteriophages.

Conclusions

This analysis of phage-mycobacterium co-evolution suggests that mycobacteriophages are playing a key-role in the on-going diversification of M. abscessus.

Reviewers

This article was reviewed by Eric Bapteste, Patrick Forterre and Eugene Koonin.

Prevalence and drug resistance of mycobacteria in Turkish cystic fibrosis patients

BACKGROUND

Isolation of mycobacteria in cystic fibrosis (CF) patients is increasingly being reported. Because of having long term antimicrobial treatment, CF patients are at risk of pulmonary infection with especially resistant nontuberculous mycobacteria (NTM) strains. The aim of the present study is to determine the prevalence of mycobacterium spp. and antimicrobial susceptibility in Turkish CF patients.

METHODS

During a 5.5 year study period, 376 sputa from 130 CF patients were analyzed. Antimycobacterial susceptibility testing was performed by the Bactec 460 TB System and the E test method.

RESULTS

Totaly 28 (7.44%) Mycobacterium spp. were isolated from eight (6.15%) CF patients. Five isolates (17.9%) were identified as Mycobacterium tuberculosis complex (MTBC), 14 (50%) as Mycobacterium abscessus and nine (32.1%) as Mycobacterium lentiflavum. All MTBC isolates were found to be susceptible to streptomycin, isoniazid, rifampicin, and ethambutol. Resistance to some antibiotics was detected in some NTM strains. These are the first data about the prevalence of mycobacteria in CF patients from Turkey.

CONCLUSIONS

In pediatric CF patients, specific mycobacterial analysis of sputum specimens and susceptibility testing should be performed for allowing early detection, identification and the possibility of eradication of these bacteria.

Genome analysis reveals three genomospecies in Mycobacterium abscessus

Background

Mycobacterium abscessus complex, the third most frequent mycobacterial complex responsible for community- and health care-associated infections in developed countries, comprises of M. abscessus subsp. abscessus and M. abscessus subsp. bolletii reviously referred as Mycobacterium bolletii and Mycobacterium massiliense. The diversity of this group of opportunistic pathogens is poorly described.

Results

In-depth analysis of 14 published M. abscessus complex genomes found a pan-genome of 6,153 proteins and core-genome of 3,947 (64.1%) proteins, indicating a non-conservative genome. Analysing the average percentage of amino-acid sequence identity (from 94.19% to 98.58%) discriminates three main clusters C1, C2 and C3: C1 comprises strains belonging to M. abscessus, C2 comprises strains belonging to M. massiliense and C3 comprises strains belonging to M. bolletii; and two sub-clusters in clusters C2 and C3. The phylogenomic network confirms these three clusters. The genome length (from 4.8 to 5.51-Mb) varies from 5.07-Mb in C1, 4.89-Mb in C2A, 5.01-Mb in C2B and 5.28-Mb in C3. The mean number of prophage regions (from 0 to 7) is 2 in C1; 1.33 in C2A; 3.5 in C2B and five in C3. A total of 36 genes are uniquely present in C1, 15 in C2 and 15 in C3. These genes could be used for the detection and identification of organisms in each cluster. Further, the mean number of host-interaction factors (including PE, PPE, LpqH, MCE, Yrbe and type VII secretion system ESX3 and ESX4) varies from 70 in cluster C1, 80 in cluster C2A, 74 in cluster C2B and 93 in clusters C3A and C3B. No significant differences in antibiotic resistance genes were observed between clusters, in contrast to previously reported in-vitro patterns of drug resistance. They encode both penicillin-binding proteins targeted by β-lactam antibiotics and an Ambler class A β-lactamase for which inhibitors exist.

Conclusions

Our comparative analysis indicates that M. abscessus complex comprises three genomospecies, corresponding to M. abscessus, M. bolletii, and M. massiliense. The genomics data here reported indicate differences in virulence of medical interest; and suggest targets for the refined detection and identification of M. abscessus.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-359) contains supplementary material, which is available to authorized users.

In vivo assessment of drug efficacy against Mycobacterium abscessus using the embryonic zebrafish test system

Mycobacterium abscessus is responsible for a wide spectrum of clinical syndromes and is one of the most intrinsically drug-resistant mycobacterial species. Recent evaluation of the in vivo therapeutic efficacy of the few potentially active antibiotics against M. abscessus was essentially performed using immunocompromised mice. Herein, we assessed the feasibility and sensitivity of fluorescence imaging for monitoring the in vivo activity of drugs against acute M. abscessus infection using zebrafish embryos. A protocol was developed where clarithromycin and imipenem were directly added to water containing fluorescent M. abscessus-infected embryos in a 96-well plate format. The status of the infection with increasing drug concentrations was visualized on a spatiotemporal level. Drug efficacy was assessed quantitatively by measuring the index of protection, the bacterial burden (CFU), and the number of abscesses through fluorescence measurements. Both drugs were active in infected embryos and were capable of significantly increasing embryo survival in a dose-dependent manner. Protection from bacterial killing correlated with restricted mycobacterial growth in the drug-treated larvae and with reduced pathophysiological symptoms, such as the number of abscesses within the brain. In conclusion, we present here a new and efficient method for testing and compare the in vivo activity of two clinically relevant drugs based on a fluorescent reporter strain in zebrafish embryos. This approach could be used for rapid determination of the in vivo drug susceptibility profile of clinical isolates and to assess the preclinical efficacy of new compounds against M. abscessus.

Gene replacement in Mycobacterium chelonae: application to the construction of porin knock-out mutants

Mycobacterium chelonae is a rapidly growing mycobacterial opportunistic pathogen closely related to Mycobacterium abscessus that causes cornea, skin and soft tissue infections in humans. Although M. chelonae and the emerging mycobacterial pathogen M. abscessus have long been considered to belong to the same species, these two microorganisms considerably differ in terms of optimum growth temperature, drug susceptibility, pathogenicity and the types of infection they cause. The whole genome sequencing of clinical isolates of M. chelonae and M. abscessus is opening the way to comparative studies aimed at understanding the biology of these pathogens and elucidating the molecular bases of their pathogenicity and biocide resistance. Key to the validation of the numerous hypotheses that this approach will raise, however, is the availability of genetic tools allowing for the expression and targeted mutagenesis of genes in these species. While homologous recombination systems have recently been described for M. abscessus, genetic tools are lacking for M. chelonae. We here show that two different allelic replacement methods, one based on mycobacteriophage-encoded recombinases and the other on a temperature-sensitive plasmid harboring the counterselectable marker sacB, can be used to efficiently disrupt genes in this species. Knock-out mutants for each of the three porin genes of M. chelonae ATCC 35752 were constructed using both methodologies, one of which displays a significantly reduced glucose uptake rate consistent with decreased porin expression.

Rapid molecular detection of inducible macrolide resistance in Mycobacterium chelonae and M. abscessus strains: a replacement for 14-day susceptibility testing?

The erm(41) gene causes inducible macrolide resistance in Mycobacterium abscessus but not Mycobacterium chelonae. erm(41) sequencing of 285 M. abscessus and 45 M. chelonae isolates was compared to 14-day susceptibility; agreement percentages were 98.9% and 100%, respectively. Extended incubation may not be necessary for M. chelonae, and the erm(41) genotype is a useful adjunct for M. abscessus.

Inventory study of non-tuberculous mycobacteria in the European Union

Background

Since non-tuberculous mycobacteria (NTM) disease is not notifiable in most European Union (EU) and European Economic Area (EEA) countries, the epidemiological situation of the >150 NTM species is largely unknown. We aimed to collect data on the frequency of NTM detection and NTM species types in EU/EEA countries.

Methods

Officially nominated national tuberculosis reference laboratories of all EU/EEA countries were asked to provide information on: laboratory routines for detection and identification of NTM, including drug sensitivity testing (DST) methods; data on the number and type of NTM species identified; coverage and completeness of the provided data on NTM; type and number of human specimens tested for NTM; and number of specimens tested for Mycobacterium tuberculosis complex and NTM. This information was summarized and the main results are described.

Results

In total, 99 different NTM species were identified with M. avium, M. gordonae, M. xenopi , M. intracellulare, and M. fortuitum identified most frequently. Seven percent of the NTM species could not be identified. NTM was cultured from between 0.4-2.0% of the specimens (data from four countries). The laboratories use culturing methods optimised for M. tuberculosis complex. Identification is mainly carried out by a commercial line probe assay supplemented with sequencing. Most laboratories carried out DST for rapid growers and only at the explicit clinical request for slow growers.

Conclusion

It is likely that the prevalence of NTM is underestimated because diagnostic procedures are not optimized specifically for NTM and isolates may not be referred to the national reference laboratory for identification. Due to the diagnostic challenges and the need to establish the clinical relevance of NTM, we recommend that countries should concentrate detection and identification in only few laboratories.

Sacroiliitis secondary to catheter-related bacteremia due to Mycobacterium abscessus (sensu stricto)

We describe a case of sacroiliitis secondary to catheter-related bacteremia due to Mycobacterium abscessus (sensu stricto). This case confirms that MultiLocus sequence typing and variable-number tandem-repeat methods are very robust techniques to identify the pathogen species and to validate molecular epidemiological links among complex M. abscessus isolates.

Antimicrobial susceptibility of standard strains of nontuberculous mycobacteria by microplate Alamar Blue assay

In this study, 24 standard nontuberculous mycobacteria (NTM) species strains including 12 slowly growing mycobacteria strains and 12 rapidly growing mycobacteria strains were subjected to drug susceptibility testing using microplate Alamar Blue assay-based 7H9 broth. The most active antimicrobial agents against the 24 NTM strains were streptomycin, amikacin, the fluoroquinolones, and the tetracyclines. Mycobacterium chelonae, Mycobacterium abscessus, Mycobacterium bolletii, and Mycobacterium simiae are resistant to most antimicrobial agents. The susceptibility results of this study from 24 NTM standard strains can be referenced by clinicians before susceptibility testing for clinical isolates is performed or when conditions do not allow for susceptibility testing. The application of broth-based methods is recommended by the Clinical and Laboratory Standards Institute, and the documentation of the susceptibility patterns of standard strains of mycobacteria can improve the international standardization of susceptibility testing methods.

Nontuberculous mycobacteria in guadeloupe, martinique, and French Guiana from 1994 to 2012

Nontuberculous mycobacteria (NTM) are ubiquitous environmental organisms able to cause severe opportunistic human infections. Their distribution patterns are subject to geographical variations. This study describes their isolation frequencies from clinical specimen in the three French overseas departments of the Americas, namely, Guadeloupe, Martinique, and French Guiana during 1994-2012. A total of 651 strains from as many patients (one isolate per species per patient) were analysed regarding regional isolation patterns and potential pattern changes over time. The Mycobacterium avium complex was the most common group of NTM in Guadeloupe and French Guiana. In Martinique it was the second most common after the rapidly growing mycobacteria. M. fortuitum was the most commonly isolated species in all three departments. Some species (M. kansasii, M. xenopi, and M. terrae complex) displayed a clear regional preference. Furthermore a change in isolation frequency was observed for M. intracellulare (increase) and M. kansasii (decrease) in Guadeloupe. In conclusion, marked regional differences in isolation frequencies of NTM species were observed in the study area. Results are discussed in context of variables such as study populations, risk factors, methodology employed, isolation from pulmonary versus sterile isolation sites (blood, urine, and CSF), and in vitro drug-susceptibility patterns.

Complete Genome Sequence of Mycobacterium massiliense Clinical Strain Asan 50594, Belonging to the Type II Genotype

We report the complete genome sequence of the Mycobacterium massiliense clinical strain Asan 50594, which was grouped into the M. massiliense type II genotype, isolated from a Korean patient. This genome sequence will serve as a valuable reference for understanding the disparity in virulence and epidemiological traits between strains belonging to the Mycobacterium abscessus complex.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry can accurately differentiate between Mycobacterium masilliense (M. abscessus subspecies bolletti) and M. abscessus (sensu stricto)

Among 36 Mycobacterium masilliense and 22 M. abscessus isolates identified by erm(41) PCR and sequencing analysis of rpoB and 23S rRNA genes, the rate of accurate differentiation between these two subspecies was 100% by cluster analysis of spectra generated by Bruker Biotyper matrix-assisted laser desorption ionization-time of flight mass spectrometry.

Atypical mycobacterial infection mimicking metastatic cholangiocarcinoma

Mycobacterial infections are rare in developed countries. Isolated involvement of the liver and biliary tree by mycobacterial infection is extremely rare. We report a case of a 45-year-old Caucasian female presenting with obstructive jaundice with a common bile duct stricture and multiple hypodense liver lesions raising suspicion of a metastatic cholangiocarcinoma. Percutaneous core biopsies of the liver lesions however suggested granulomatous process and histology at surgical excision confirmed this finding. Atypical mycobacteria (M. abcessus) sensitive to Amikacin were cultured from the surgical specimen proving the diagnosis. With the resurgence of tubercular and atypical mycobacterial infections in the developed world, it is important not to overlook these in differential diagnosis of various malignancies.