Newly described or emerging human species of nontuberculous mycobacteria

Pacemaker infection at generator site by Mycobacterium mageritense: A case report and review of the literature

We herein report an unusual case of Mycobacterium mageritense pacemaker infection at generator site in a 62-year old female with no pertinent past medical history. Pacemaker-related infections caused by nontuberculous mycobacteria are rare but can lead to significant morbidity and mortality. Mycobacterium mageritense is rarely reported in pacemaker infections and is challenging to treat due to resistance to many antimicrobial agents. In our case, the patient's pacemaker infection did not respond to standard treatment, leading to complete device removal. Our case highlights the challenges in treating Mycobacterium Mageritense, especially that our patient had a more resistant organism than those reported previously in literature. To our knowledge, such cases are infrequently reported in the literature.

Mycobacterial periprosthetic joint infection after primary total knee arthroplasty

PURPOSE

Mycobacterial periprosthetic joint infection (PJI) is very rare and is generally associated with an immunosuppressive environment. Few large-scale studies of this unusual PJI have been conducted. The current study was performed to assess the clinical features and outcomes following two-stage re-implantation for mycobacterial PJI after primary total knee arthroplasty (TKA).

METHODS

We conducted a retrospective review of data collected from our database involving ten cases of two-stage re-implantation manifesting mycobacterial PJI. Patients were followed for at least five years or until recurrent infection. The mean follow-up duration in patients who remained free of infection was 7.5 years (range 5-9.5 years).

RESULTS

Seven patients (70%) belonged to the American Society of Anesthesiologists' grade 3 or 4. The surgical protocol entailed resection arthroplasty and cement spacer insertion with vigorous debridement, followed by at least six weeks of systemic antimicrobial therapy and delayed re-implantation in all patients. The median duration from resection arthroplasty to re-implantation was 5.3 months (range 2-10.5 months). Following re-implantation, five patients with Mycobacterium fortuitum were treated with amikacin for six weeks and oral clarithromycin for three months. Five patients infected with M. tuberculosis received anti-tuberculosis medications immediately after pathogen isolation, for a period of 12 months.

CONCLUSION

Mycobacterial PJI can be treated successfully via resection arthroplasty and delayed re-implantation combined with proper antimicrobial agents. Suspicious infection or loosening after primary TKA, particularly in an immunosuppressive environment, warrants the attention of an orthopedic surgeon to consider the possibility of unusual PJI.

Mycobacterium malmoense: an unusual pathogen causing endocarditis, a case report and literature review

Non-tuberculous mycobacterias (NTM) are important pathogens responsible for a broad spectrum of diseases in humans. Although exposure is widespread since they are distributed in the environment, the development of the disease is rare. It will depend on the specific species, their virulence (only 50 have been found to cause disease), and the host’s immune response. M Mycobacterium Malmoense is a NTM first reported in 1977 at Malmö, Sweden, based on four cases of lung infections. After these, other infections have been reported mainly involving the respiratory tract. Extrapulmonary infections are limited to cervical adenitis, and rarely to tenosynovitis and disseminated disease. We are hence reporting, to our knowledge, the first case of M. malmoense as the cause of bacterial endocarditis in the world.

Mycobacterium branderi Infection in a Horse with Granulomatous Mesenteric Lymphadenitis

Although relatively uncommon in horses, infections caused by Mycobacterium spp. may affect the gastrointestinal tract. Mycobacterium branderi is a non-tuberculous Mycobacterium (NTM) that causes respiratory infections in man. Non-tuberculous mycobacteria may also affect horses; however, infection by M. branderi has not yet been reported in this species. This report describes the clinical, pathological, microbiological and molecular findings of M. branderi infection in a horse, causing granulomatous mesenteric lymphadenitis. A 17-year-old Thoroughbred stallion had a 3-month history of chronic diarrhoea, cachexia and ventral and cervical oedema. Necropsy examination revealed severe mesenteric lymphadenomegaly, together with mesenteric lymphangiectasia and diffuse small intestinal mucosal thickening. Microscopically, the mesenteric lymph node had diffuse granulomatous inflammatory infiltration, replacing most of the nodal parenchyma, with multiple acid-fast bacilli within the cytoplasm of macrophages. There was also diffuse lymphangiectasia. Fresh samples of mesenteric lymph nodes yielded no bacterial growth; however, nested polymerase chain reaction products obtained from the mesenteric lymph node samples were consistent with M. branderi. This infection should be included as a differential diagnosis in cases of chronic diarrhoea in horses, especially when granulomatous enteritis and lymphadenitis are also observed.

Lack of association between rrl and erm(41) mutations and clarithromycin resistance in Mycobacterium abscessus complex

BACKGROUND

Mycobacterium abscessus complex (MABC) includes species with high resistance rates among mycobacterial pathogens. In fact, MABC infections may not respond to clarithromycin treatment, which has historically been very effective against MABC infection. Molecular markers have been proposed to detect both acquired (rrl polymorphisms) and inducible (erm(41) polymorphisms) clarithromycin resistance in MABC isolates.

OBJECTIVES

This study aimed to evaluate the susceptibility profile and molecular markers of clarithromycin resistance in MABC.

METHODS

The clarithromycin susceptibility profile was determined by broth microdilution with reads on days 3, 5, 7 and 14. Mutations in the rrl and erm(41) genes were evaluated by polymerase chain reaction (PCR) using specific primers, followed by sequencing.

FINDINGS

A total of 14 M. abscessus subsp. abscessus isolates and 28 M. abscessus subsp. massiliense isolates were evaluated, and clarithromycin resistance was observed in all isolates for up to three days of incubation. None of the 42 isolates exhibited a point mutation in the rrl gene, while all the isolates had a T28 polymorphism in the erm(41) gene. Moreover, all 28 M. abscessus subsp. massiliense isolates had a deletion in the erm(41) gene.

MAIN CONCLUSIONS

While all the MABC isolates exhibited acquired clarithromycin resistance, no isolates exhibited a point mutation in the rrl gene in this study. The M. abscessus subsp. massiliense isolates demonstrated clarithromycin resistance, which is an uncommon phenotype. The molecular data for the rrl and erm(41) genes were not consistent with the phenotypic test results of clarithromycin susceptibility, indicating a lack of correlation between molecular clarithromycin resistance markers for both acquired and inducible resistance.

Selection of Resistance to Clarithromycin in Mycobacterium abscessus Subspecies

Mycobacterium abscessus is an emerging pathogen against which clarithromycin is the main drug used. Clinical failures are commonly observed and were first attributed to acquired mutations in rrl encoding 23S rRNA but were then attributed to the intrinsic production of the erm(41) 23S RNA methylase. Since strains of M. abscessus were recently distributed into subspecies and erm(41) sequevars, we investigated acquired clarithromycin resistance mechanisms in mutants selected in vitro from four representative strains. Mutants were sequenced for rrl, erm(41), whiB, rpIV, and rplD and studied for seven antibiotic MICs. For mutants obtained from strain M. abscessus subsp. abscessus erm(41) T28 sequevar and strain M. abscessus subsp. bolletii, which are both known to produce effective methylase, rrl was mutated in only 19% (4/21) and 32.5% (13/40) of mutants, respectively, at position 2058 (A2058C, A2058G) or position 2059 (A2059C, A2059G). No mutations were observed in any of the other genes studied, and resistance to other antibiotics (amikacin, cefoxitin, imipenem, tigecycline, linezolid, and ciprofloxacin) was mainly unchanged. For M. abscessus subsp. abscessus erm(41) C28 sequevar and M. abscessus subsp. massiliense, not producing effective methylase, 100% (26/26) and 97.5% (39/40) of mutants had rrl mutations at position 2058 (A2058C, A2058G, A2058T) or position 2059 (A2059C, A2059G). The remaining M. abscessus subsp. massiliense mutant showed an 18-bp repeat insertion in rpIV, encoding the L22 protein. Our results showed that acquisition of clarithromycin resistance is 100% mediated by structural 50S ribosomal subunit mutations for M. abscessus subsp. abscessus erm(41) C28 and M. abscessus subsp. massiliense, whereas it is less common for M. abscessus subsp. abscessus erm(41) T28 sequevar and M. abscessus subsp. bolletii, where other mechanisms may be responsible for failure.

Keim oder kein Keim: Herausforderungen bei der Diagnose mykobakterieller Infektionen der Haut

Kutane Mykobakteriosen sind in Deutschland selten. Dennoch ist es für eine frühzeitige Diagnose und anschließende wirksame Behandlung erforderlich, dass diese Krankheitsbilder im ärztlichen Bewusstsein verankert sind. Darüber hinaus stehen Infektionen mit Mykobakterien auf der Liste der Differentialdiagnosen vieler Hautkrankheiten. Diagnosen kutaner Mykobakteriosen beruhen auf klinischen Merkmalen und auf Laboruntersuchungen, einschließlich bakterieller Kulturen, histopathologischer Untersuchungen und PCR-basierten Verfahren. Das Wissen um Möglichkeiten und Grenzen dieser Laboruntersuchungen ist von zentraler Bedeutung, um eine angemessene klinische Entscheidung zu treffen. In diesem Beitrag diskutieren wir die aktuellen diagnostischen Möglichkeiten, die in Verdachtsfällen kutaner Mykobakteriosen zur Verfügung stehen.

Acute necrotizing pneumonia combined with parapneumonic effusion caused by Mycobacterium lentiflavum: a case report

Background

Mycobacterium lentiflavum (M. lentiflavum), a slow growing nontuberculous mycobacterium (NTM), has recently been described as an emerging human pathogen regardless of the immune status of the host. Previous reports have demonstrated that cervical lymphadenitis of children is the most frequent pathology of M. lentiflavum. However, there are little reports regarding pulmonary diseases by M. lentiflavum specifically in immunocompetent patients.

Case presentation

A 60-year-old man having prolonged productive cough and dyspnea with fever was initially diagnosed as pneumonia with parapneumonic effusion. Imaging studies showed that the radiologic abnormality was acute bronchopneumonic infiltration with abscess formation in the left lower lobe and parapneumonic pleural effusion. M. lentiflavum was identified in the cultured pleural tissues. On the basis of these findings, he was diagnosed as pulmonary infection and pleurisy caused by M. lentiflavum, which was treated with a combination of antibiotics covering NTM. His clinical manifestations were dramatically improved by the treatment targeting NTM, while those were refractory to empirical antibiotic therapy.

Conclusion

In this report, we introduce the isolation of M. lentiflavum from pleural tissues associated with acute necrotizing pneumonia combined with parapneumonic effusion in an immunocompetent host, suggesting that the M. lentiflavum can be a human pathogen invovled in pulmonary infectious diseases and pleurisy with poor response to empirical antibiotic treatment.

The management of non-tuberculous cervicofacial lymphadenitis in children: A systematic review and meta-analysis

OBJECTIVES

Cervicofacial lymphadenitis is the most common manifestation of infection with non-tuberculous mycobacteria (NTM) in immunocompetent children. Although complete excision is considered standard management, the optimal treatment remains controversial. This study reviews the evidence for different management options for NTM lymphadenitis.

METHODS

A systematic literature review and meta-analysis were performed including 1951 children from sixty publications. Generalised linear mixed model regressions were used to compare treatment modalities.

RESULTS

The adjusted mean cure rate was 98% (95% CI 97.0-99.5%) for complete excision, 73.1% (95% CI 49.6-88.3%) for anti-mycobacterial antibiotics, and 70.4% (95% CI 49.6-88.3%) for 'no intervention'. Compared to 'no intervention', only complete excision was significantly associated with cure (OR 33.1; 95% CI 10.8-102.9; p < 0.001). Complete excision was associated with a 10% risk of facial nerve palsy (2% permanent). 'No intervention' was associated with delayed resolution.

CONCLUSIONS

Complete excision is associated with the highest cure rate in NTM cervicofacial lymphadenitis, but also had the highest risk of facial nerve palsy. In the absence of large, well-designed RCTs, the choice between surgical excision, anti-mycobacterial antibiotics and 'no intervention' should be based on the location and extent of the disease, and acceptability of prolonged time to resolution.

Disseminated infection with Mycobacterium tilburgii in a male immunocompromised patient

Mycobacterium tilburgii is a nonculturable nontuberculous mycobacterium identifiable only by molecular methods. We report a case of disseminated M. tilburgii infection illustrating the importance of 16S rRNA gene sequencing to determine the responsible mycobacterial pathogen and the difficulties in tailoring antimycobacterial treatment in the absence of a culturable organism.

Identification and distribution of nontuberculous mycobacteria from 2005 to 2011 in cheonan, Korea

Background

Nontuberculous mycobacteria (NTM) are considered opportunistic pathogens, and several species of NTM are associated with human diseases that typically involve the pulmonary, skin/soft tissue, or lymphatic systems; such infection may also cause disseminated diseases. Recent studies have reported increasing rates of NTM-induced disease worldwide.

Methods

Respiratory samples are being analyzed for acid-fast bacilli (AFB) culture and NTM identification at Dankook University Hospital in Cheonan, Korea, from September 2005 to September 2011. Identification is performed by using polymerase chain reaction-restriction fragment length polymorphism analysis targeting a novel region of the rpoB gene.

Results

A total of 25,133 specimens were received for AFB culture, of which 1,014 (4.0%) were NTM-positive. A total of 267 samples from 186 patients were tested for NTM identifications, and 232 samples from 157 patients were positive for NTM species. Among the patients who tested positive for NTM, 65.6% were men and the average age was 63.3 years. Mycobacterium avium complex, the most commonly detected NTM pathogen, was found in 65.9% of the 232 samples. The annual average percentage of NTM isolates from AFB culture-positive specimens was 31.3%: the highest rate was seen in 2011 (44.3%), followed by 2009 (37.4%) and 2010 (37.2%). An upward trend in NTM incidence was found during the study period.

Conclusion

The prevalence of pulmonary NTM isolates continues to increase in Cheonan, suggesting that pulmonary NTM disease is becoming increasingly common.

[Identification of Nontuberculous Mycobacteria by Sequence Analysis of the 16S Ribosomal RNA, the Heat-shock Protein 65 and the RNA Polymerase beta-Subunit Genes.]

BACKGROUND

The diagnosis of diseases caused by nontuberculous mycobacteria (NTM) is difficult, because NTM are prevalent in the environment such as soil and water, and because they have fastidious properties. In this study we investigated clinical isolates of NTM for their distribution pattern and accurate species identification.

METHODS

We selected presumptive NTM isolates negative for probe hybridization for M. tuberculosis complex, cultured in a third referral hospital from 21 January 2003 to 20 January 2004. Ninety seven-isolates were identified to the species level by direct sequencing of fragments of 16S rRNA, hsp65 and rpoB genes. A total of 120 isolates were studied for the distribution analysis.

RESULTS

Frequently identified NTM species were M. avium (30.8%), M. intracellulare (23.3%) and M. abscessus (18.3%). Others were M. gordonae, M. senegalense, M. fortuitum, M. peregrinum, M. kansasii, M. terrae complex, M. lentiflavum, M. chelonae, and M. szulgai. Three M. tuberculosis complex (2.5%) were also identified among the presumptive NTM isolates. The identification rate by sequencing of 16S rRNA, rpoB, and hsp65 were 65%, 82% and 87%, respectively. The hsp65 or rpoB gene was more efficient than 16S rRNA for the identification of NTM by sequencing.

CONCLUSIONS

Some NTM are increasingly considered to be the causative organisms in clinical diseases. Thus, direct sequencing could be adapted to routine work of clinical laboratories for accurate identification of NTM to the species level.

Mycobacterium avium complex--the role of potable water in disease transmission

Mycobacterium avium complex (MAC) is a group of opportunistic pathogens of major public health concern. It is responsible for a wide spectrum of disease dependent on subspecies, route of infection and patients pre-existing conditions. Presently, there is limited research on the incidence of MAC infection that considers both pulmonary and other clinical manifestations. MAC has been isolated from various terrestrial and aquatic environments including natural waters, engineered water systems and soils. Identifying the specific environmental sources responsible for human infection is essential in minimizing disease prevalence. This paper reviews current literature and case studies regarding the wide spectrum of disease caused by MAC and the role of potable water in disease transmission. Potable water was recognized as a putative pathway for MAC infection. Contaminated potable water sources associated with human infection included warm water distribution systems, showers, faucets, household drinking water, swimming pools and hot tub spas. MAC can maintain long-term contamination of potable water sources through its high resistance to disinfectants, association with biofilms and intracellular parasitism of free-living protozoa. Further research is required to investigate the efficiency of water treatment processes against MAC and into construction and maintenance of warm water distribution systems and the role they play in MAC proliferation.

IL-2 simultaneously expands Foxp3+ T regulatory and T effector cells and confers resistance to severe tuberculosis (TB): implicative Treg-T effector cooperation in immunity to TB

The possibility that simultaneous expansion of T regulatory cells (Treg) and T effector cells early postinfection can confer some immunological benefits has not been studied. In this study, we tested the hypothesis that early, simultaneous cytokine expansion of Treg and T effector cells in a tissue infection site can allow these T cell populations to act in concert to control tissue inflammation/damage while containing infection. IL-2 treatments early after Mycobacterium tuberculosis infection of macaques induced simultaneous expansion of CD4(+)CD25(+)Foxp3(+) Treg, CD8(+)CD25(+)Foxp3(+) T cells, and CD4(+) T effector/CD8(+) T effector/Vγ2Vδ2 T effector populations producing anti-M. tuberculosis cytokines IFN-γ and perforin, and conferred resistance to severe TB inflammation and lesions. IL-2-expanded Foxp3(+) Treg readily accumulated in pulmonary compartment, but despite this, rapid pulmonary trafficking/accumulation of IL-2-activated T effector populations still occurred. Such simultaneous recruitments of IL-2-expanded Treg and T effector populations to pulmonary compartment during M. tuberculosis infection correlated with IL-2-induced resistance to TB lesions without causing Treg-associated increases in M. tuberculosis burdens. In vivo depletion of IL-2-expanded CD4(+)Foxp3(+) Treg and CD4(+) T effectors during IL-2 treatment of M. tuberculosis-infected macaques significantly reduced IL-2-induced resistance to TB lesions, suggesting that IL-2-expanded CD4(+) T effector cells and Treg contributed to anti-TB immunity. Thus, IL-2 can simultaneously activate and expand T effector cells and Foxp3(+) Treg populations and confer resistance to severe TB without enhancing M. tuberculosis infection.

First Canadian Reports of Cervical Adenitis Due to Mycobacterium Malmoense and a 10-year Review of Nontuberculous Mycobacterial Adenitis

The present report reviews a decade of experience with nontuberculous mycobacterial adenitis at a pediatric referral centre, noting that patients are often subjected to multiple ineffective antibiotic courses, and that delays in diagnosis and referral for appropriate therapy are common. Notable clinical features include a mean age of presentation of 3.4 years, a male-to-female ratio of 1:1.5 and a gradual onset of painless, unilateral cervical adenopathy. Fever was absent in most patients (77%), and the disease failed to respond to antistaphylococcal antibiotics. The mean time to correct diagnosis was longer than three months (15 weeks). The clinical features of the disease are highlighted and presented with a practical diagnostic approach to the child with subacute/chronic adenitis. New molecular diagnostic tools and emerging mycobacteria are discussed, including the first reports of Mycobacterium malmoense adenitis in Canada.

Mycobacterial prosthetic valve endocarditis

Prosthetic valve endocarditis (PVE) due to mycobacteria is a rare but frequently fatal complication that may occur early after the surgical procedure, or even years later. Infection has been described with both mechanical and biologic valvular prosthesis. The most commonly implicated mycobacterial species belong to the rapid-grower group (M. chelonei, M. fortuitum, and M. abscessus) of nontuberculous mycobacteria (NTM). The source of infection in this context is thought to be nosocomial, likely related to preoperative or intraoperative contamination of the prosthesis by contact with aqueous solutions containing the organisms. These infections are difficult to diagnose because blood cultures are often negative. Clinically, it is important to recognize the possibility of NTM-PVE in the differential diagnosis of culture-negative patients who develop signs and symptoms of endocarditis, whether they present early or late in onset after the surgical procedure. These patients should be treated with surgical removal of the infected valve, followed by adequate antimicrobial therapy based on the susceptibility of the species isolated from the valve or perivalvular tissue culture. In a significant number of patients, however, an unstable hemodynamic condition ensues, precluding surgical intervention, and therefore leading to a high mortality rate.

Non-tuberculous mycobacterial infections

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms in contrast to those belonging to the M. tuberculosi complex (MTB). NTM infects and causes disease only in hosts with local or general predisposing factors. Lung infection following inhalation of NTM is the most common NTM disease but soft tissue infections may occur in connection with contaminated trauma or surgery. Microbiological diagnosis is obtained by microscopy for acid-fast bacteria (AFB) on secretions or biopsies, and by culture on special media. With the high specificity of MTB- polymerase chain reaction (PCR), a positive AFB smear combined with negative MTB-PCR denotes infection with NTM. Sophisticated species diagnosis of cultured NTM is attained by various molecular methods, where 16S rDNA-sequencing remains the gold standard. The panorama of infection with different rapidly growing (RGM) or slowly growing mycobacteria (SGM) in Sweden is described. Sensitivity testing in vitro to antimycobacterial drugs against NTM does not always preclude the in vivo efficacy. Standard antimycobacterial treatment regimens have been defined for infection with several NTM species. Sensitivity testing should be performed in selected cases only, as in case of relapse or suspected development of resistance of the NTM strain. The spectrum of disease caused by NTM species that display a very low pathogenic potential is likely to widen over time as severe immunosuppression will continue to be prevalent in several patient categories.

Identification of non-tuberculous mycobacteria: utility of the GenoType Mycobacterium CM/AS assay compared with HPLC and 16S rRNA gene sequencing

Non-tuberculous mycobacteria (NTM) causing clinical disease have become increasingly common and more diverse. A new reverse line probe assay, GenoType Mycobacterium CM/AS (Hain Lifescience), was evaluated for identification of a broad range of NTM. It was compared with phenotypic (HPLC) and molecular (DNA probes, in-house real-time multiplex species-specific PCR, 16S rRNA gene PCR and sequencing) identification techniques, which together provided the reference 'gold standard'. A total of 131 clinical isolates belonging to 31 Mycobacterium species and 19 controls, including 5 non-Mycobacterium species, was used. Concordant results between the GenoType Mycobacterium assay and the reference identification were obtained in 119/131 clinical isolates (90.8 %). Identification of Mycobacterium abscessus and Mycobacterium lentiflavum by the assay was problematic. The GenoType Mycobacterium assay enables rapid identification of a broad range of potentially clinically significant Mycobacterium species, but some species require further testing to differentiate or confirm ambiguous results.

A novel gene, erm(41), confers inducible macrolide resistance to clinical isolates of Mycobacterium abscessus but is absent from Mycobacterium chelonae

Mycobacterium abscessus infections tend to respond poorly to macrolide-based chemotherapy, even though the organisms appear to be susceptible to clarithromycin. Circumstantial evidence suggested that at least some M. abscessus isolates might be inducibly resistant to macrolides. Thus, the purpose of this study was to investigate the macrolide phenotype of M. abscessus clinical isolates. Inducible resistance to clarithromycin (MIC > 32 microg/ml) was found for 7 of 10 clinical isolates of M. abscessus previously considered susceptible; the remaining 3 isolates were deemed to be susceptible (MIC <or= 0.5 microg/ml). Inducible resistance was conferred by a novel erm gene, erm(41), which was present in all 10 isolates and in an isolate of Mycobacterium bolletii (M. abscessus type II). However, the erm(41) alleles were nonfunctional in the three susceptible M. abscessus isolates. No evidence of erm(41) was found in Mycobacterium chelonae, and an isolate of Mycobacterium massiliense appeared to be an erm(41) deletion mutant. Expression of erm(41) in M. abscessus conferred resistance to clarithromycin and erythromycin and the ketolide HMR3004. However, this species was found to be intrinsically resistant, independent of erm(41), to clindamycin, quinupristin (streptogramin B), and telithromycin. The ability to confer resistance to clindamycin and telithromycin, but not quinupristin, was demonstrated by expressing erm(41) in Maycobacterium smegmatis. Exposure of M. abscessus to the macrolide-lincosamide-streptogramin B-ketolide agents increased the levels of erm(41) mRNA 23- to 250-fold within 24 h. The inducible macrolide resistance phenotype of some M. abscessus isolates may explain the lack of efficacy of macrolide-based chemotherapy against this organism.

Comparison of DNA pyrosequencing with alternative methods for identification of mycobacteria

Identification of mycobacterial clinical isolates by pyrosequencing within the hypervariable A region of the 16S rRNA gene was compared to other identification methods. For >90% of isolates, these identifications correlated to the level of complex or species. For identification of many mycobacteria, pyrosequencing offers an inexpensive alternative to traditional sequencing.

A low incidence of nontuberculous mycobacterial infections in pediatric hematopoietic stem cell transplantation recipients

Hematopoietic stem cell transplantation (HSCT) is being used to treat a wide spectrum of clinical disorders but opportunistic infection remains an important factor determining outcomes for these patients. Nontuberculous mycobacterial (NTM) infections are being reported more frequently in HSCT recipients and the incidence of NTM infections in adult recipients is reported to be 0.4%-4.9%. However, the incidence and severity of NTM infections are less well described in pediatric HSCT recipients. Centers for Disease Control and Prevention guidelines were used to define definite and probable NTM infection among 132 children undergoing 169 HSCT between January 2000 and December 2004 at our institution. NTM infection was diagnosed in 5 of 132 pediatric recipients (3.8%). There were no NTM infections diagnosed in the autologous HSCT recipients and the incidence of NTM in allogeneic HSCT recipients was 6.4% (95% confidence interval, 0.8-11.9). The mean age of the HSCT recipients who developed NTM infections was 8 years (range, 2-19 years); 3 were male and 2 were female. Four conditioning regimens included alemtuzumab and 3 had antithymocyte globulin. Of the 5 patients with NTM infections, 2 met the criteria for definite infection and 3 for probable infection. Of the 2 patients with definite NTM infection, 1 had disseminated disease with Mycobacterium avium complex and the other had Mycobacterium chelonae catheter-related bloodstream infection. The probable NTM infections were 1 skin infection with Mycobacterium kansasii and 2 lower respiratory tract infections with M avium complex. Median time to NTM infection was 115 days (range, 14-269 days) after HSCT. Two patients had graft-versus-host disease at the time of NTM infection. All 5 patients received 3-4 antimycobacterial drugs and all NTM infections resolved. In summary, the incidence of NTM infection in pediatric HSCT recipients appears similar to that described in adult HSCT recipients and the outcome appears to be excellent with the proper antibiotic therapy. The increased use of anti-T cell antibodies appears to be associated with an increased risk of NTM infections in pediatric HSCT recipients. Multicenter studies are needed to identify the risk factors, early diagnostic criteria, and optimal therapy.

Mycobacterial antigens may be important in sarcoidosis pathogenesis

PURPOSE OF REVIEW

To describe the most recent epidemiologic, molecular and immunologic literature related to the role of infectious antigens in sarcoidosis pathogenesis, with a focus upon Mycobacterium and Proprionibacterium species.

RECENT FINDINGS

Recent studies of successful molecular analysis for and humoral immunity to mycobacterial antigens from sarcoidosis patients have renewed interest in a potential role of mycobacteria in sarcoidosis. One study provided molecular and immunologic evidence for mycobacteria among sarcoidosis subjects from the United States. These studies, while preliminary, provide the groundwork for more in-depth studies of the potential role of mycobacteria in sarcoidosis pathogenesis. Proprionibacteria have also been proposed as a cause of sarcoidosis; a study of the detection of Proprionibacterium species nucleic acids throughout the lung of sarcoidosis and control subjects, however, suggests that these organisms are less likely to be causal.

SUMMARY

While the studies to date do not fulfill Koch's postulates, they do add further support to the hypothesis that infectious antigens, particularly those from mycobacteria, may have a causal role in some sarcoidosis cases. In future studies that purport to show an association of microbial antigen(s) with sarcoidosis, investigation of genetic risk factors contributing to risk will be important, in order to explain why some patients are found to have an association with microbial antigens and others are not.

Intrinsic macrolide resistance in rapidly growing mycobacteria

This study reports the discovery of erm genes in seven species of rapidly growing mycobacteria (RGM): Mycobacterium boenickei, M. goodii, M. houstonense, M. mageritense, M. neworleansense, M. porcinum, and M. wolinskyi. This study further substantiates the role of erm genes in intrinsic macrolide resistance in RGM.

Pneumonia lipóide exógena: importância da história clínica no diagnóstico

A pneumonia lipóide é uma doença rara, resultante da microaspiração de formulações lipídicas. Para seu diagnóstico, o grau de suspeição clínica deve ser elevado. Relata-se o caso de uma mulher com passado de câncer de mama, apresentando dispnéia e tosse progressivas e infiltrado pulmonar bilateral na radiografia. A suspeita de linfangite carcinomatosa com indicação de quimioterapia foi questionada por achados não usuais na tomografia computadorizada de alta resolução e história de ingestão crônica de laxantes contendo óleo mineral. A biópsia pulmonar confirmou pneumonia lipóide, que deve ser considerada em pacientes com pneumopatia difusa e exposição a potenciais agentes causadores.

Fungi, mycobacteria, zoonotic and other organisms in prosthetic joint infection

A systematic review of the presentation and management of prosthetic joint infection (PJI) due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms is not available. We therefore sought to provide a resource for the practicing orthopaedic surgeon which will serve as a guide for making appropriate decisions in managing such rare, but potentially problematic conditions. We conducted a Medline search of all case reports of PJI due to these unusual microorganisms. Our review of the current literature showed the diagnosis of PJI due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms typically necessitates specialized diagnostic tests. Maintaining a high index of suspicion in diagnosis of such unusual microorganisms and requesting the appropriate laboratory tests at the time of surgical débridement is crucial for determining the microbiologic etiology of these infections. The appropriate medical and surgical management of such infections is complex and often requires the use of special antimicrobials with which the orthopaedist may not be familiar. Collaboration with an infectious disease specialist is advisable when treating these infections.

A cord blood transplant recipient with Mycobacterium mucogenicum central venous catheter infection after infusion of tap water

Mycobacterium mucogenicum is an unusual cause of central venous catheter and wound infections in immunocompromised persons. The organism is often found in drinking water and is resistant to many disinfectants. We report a cord blood transplant recipient who developed a central venous catheter infection after the patient herself had flushed her catheter with tap water. The infection was successfully treated by removal of the central venous catheter and administration of antimicrobial therapy.

Diagnostic application of genotypic identification of mycobacteria

This study evaluated conventional methods, GLC and three molecular tests, including 16S rRNA sequencing, for the identification of mycobacteria, and the experiences of the authors with the integration of these methods into a diagnostic clinical laboratory were also recorded. Of 1067 clinical isolates of mycobacteria identified by conventional tests, 365 were tested by Accuprobe hybridization assays and PCRs specific for Mycobacterium tuberculosis (MTB) complex or Mycobacterium avium complex (MAC), 202 were tested by 16S rRNA sequencing, and 142 were tested by GLC. Three runs of all tests were performed on a weekly basis. The identifications for 209 MTB complex and 118 MAC isolates obtained by species-specific PCR were in complete agreement with AccuProbe hybridization and conventional test results. The 16S rRNA sequence-based identification, at a similarity of > or =99 %, for 132 of 142 isolates was concordant with the identifications made by the biochemical methods, and for 134 isolates was concordant with the identifications made by GLC at species, group or complex level. 16S rRNA sequencing resulted in fewer incorrectly identified or unidentified organisms than GLC or conventional tests. For the slowly growing non-tuberculous mycobacteria, the mean turnaround times for identification were 4-5 days for 16S rRNA sequencing, 14-29 days for GLC and 22-23 days for conventional methods. Considering the large proportion of some species among clinical isolates, a strategy of initial screening with species-specific PCR (or AccuProbe assays) for the MTB complex and MAC, followed by direct sequencing of the strains that yield negative results, should make 16S rRNA sequencing more affordable for routine application in diagnostic laboratories.

Effectiveness of fluoroquinolones against Mycobacterium abscessus in vivo

PURPOSE

To determine the effectiveness of fluoroquinolones against Mycobacterium abscessus in vivo.

METHODS

M. abscessus growth was determined quantitatively in rabbit corneas after intrastromal bacterial injection (10(4) CFU/cornea; n >or= 4 corneas per group). Eyes were treated topically with 0.3% ciprofloxacin, 0.5% levofloxacin, or 0.5% moxifloxacin by three protocols: (1) 1 drop of antibiotic applied hourly for 10 hr on day 3 postinfection (PI); (2) 1 drop applied every 2 hr for 10 hr on days 2 and 3 PI; or (3) 1 drop applied every 2 hr for 10 hr on days 1, 2, and 3 PI. Corneas were cultured 1 hr after the last topical drop. Results are expressed as the log CFU.

RESULTS

Bacteria in control group reached maximal numbers in vivo by day 3 PI (approximately 6 logs CFU/cornea). Treatment of infected eyes on day 3 with moxifloxacin or levofloxacin resulted in approximately 2.0 log decrease in CFU/cornea relative to the untreated control. Treatment on days 2 and 3 with moxifloxacin or levofloxacin resulted in approximately 3.0 and 2.5 log CFU/cornea decrease, respectively. Ciprofloxacin had no effect on bacterial load. Treatment on days 1, 2, and 3 with moxifloxacin resulted in a 5.5 log CFU decrease, whereas treatment with levofloxacin or ciprofloxacin resulted in a approximately 4.0 log CFU decrease.

CONCLUSIONS

Moxifloxacin, and to a lesser extent levofloxacin and ciprofloxacin, demonstrated significant effectiveness for reducing the number of M. abscessus in vivo, suggesting the potential usage of these agents in prevention of M. abscessus keratitis.

Non-tuberculous mycobacteria disease as a cause of hospitalization in HIV-infected subjects

OBJECTIVES

The present study characterized and determined the prevalence of mycobacterial diseases (tuberculosis (TB) and non-tuberculous mycobacteria (NTM)) as a cause of hospitalization among HIV-infected subjects consecutively admitted to a large metropolitan hospital during 2001/2002.

METHODS

Hospital discharge diagnoses were established for 521 HIV-positive patients.

RESULTS

Respiratory disease accounted for 49% of the admissions. Community acquired pneumonia (CAP) was the main cause of respiratory disease (52%) followed by Pneumocystis carinii (PCP, 24%), non-tuberculous mycobacteria (NTM, 11%) and Mycobacterium tuberculosis (TB, 9%). Mycobacterium tuberculosis disease was established using bacteriological, clinical and radiographic criteria. NTM disease was defined following the American Thoracic Society criteria. NTM was disseminated in the majority of cases (19 Mycobacterium avium complex (MAC), one Mycobacterium kansasii). Nine patients had respiratory disease (seven MAC, one Mycobacterium fortuitum, one Mycobacterium kansasii) and one had gastrointestinal disease caused by MAC. Mortality was 10% for NTM disseminated cases; none of the TB patients died over the course of the study. The length of hospitalization for NTM patients was longer (15+/-13 days) than for other respiratory cases (10+/-10, p=0.04).

CONCLUSIONS

NTM disease along with its related mortality is a significant pathology as a cause of hospitalization among HIV-infected individuals.

Species identification of mycobacteria in paraffin-embedded tissues: frequent detection of nontuberculous mycobacteria

Diagnosis of infections caused by mycobacteria, especially nontuberculous mycobacteria still represents a difficult task both in microbiology and pathology. The aim of this study was to determine the frequency of mycobacterial DNA detectable by PCR in formalin-fixed paraffin-embedded tissues showing suspicious granulomatous lesions. A total of 190 archival specimens were analyzed, using a nested PCR protocol, which amplifies a fragment of the mycobacterial 65-kDa heat-shock protein gene. Restriction fragment-length polymorphisms and sequencing were utilized to further analyze the obtained PCR products. Corresponding microbiological culture results were available for 41 cases. We detected mycobacterial DNA in 119 cases (63%), of which 71 (60%) were positive for Mycobacterium tuberculosis complex DNA and 41 (34%) for DNA of nontuberculous mycobacteria. Seven cases (6%) could not be subtyped for technical reasons. The largest group of nontuberculous mycobacteria comprised 29 cases (25% of the 119 positive cases), which were assigned to Mycobacterium fortuitum complex. Mycobacterium avium-intracellulare complex was detected in eight (7%) cases, Mycobacterium gordonae in three (2.5%) and Mycobacterium rhodesiae in a single case (0.8%). All cases of Mycobacterium tuberculosis were unequivocally identified by restriction fragment-length polymorphism analysis. In contrast, sequencing provided a gain of information over restriction fragment-length polymorphism analysis in 37% of the nontuberculous mycobacteria cases (15 of 41). Alignment studies on DNA of nontuberculous mycobacteria showed frequent sequence variations, supporting the existence of sequevars. Comparison of molecular data to available results of microbiological culture assays showed a good concordance of 83%. In conclusion, amplification and sequencing of the mycobacterial 65-kDa heat-shock protein gene is an excellent tool for species identification of mycobacteria, especially nontuberculous mycobacteria, in formalin-fixed paraffin-embedded tissues.

Molecular basis of intrinsic macrolide resistance in clinical isolates of Mycobacterium fortuitum

OBJECTIVES

Some clinical isolates of Mycobacterium fortuitum are naturally resistant to macrolides, e.g. clarithromycin. Thus, the aim of this study was to identify the gene(s) conferring this resistance.

METHODS

M. fortuitum ATCC 6841T DNA libraries were screened for plasmids that complemented the macrolide-susceptible phenotype of Mycobacterium smegmatis variant ermKO4 [erm(38)-negative]. Macrolide-resistant M. smegmatis transformants were selected on agar containing 128 mg/L erythromycin.

RESULTS

Genetic complementation identified an M. fortuitum rRNA methylase gene, termed erm(39), 69% identical to erm(38) of M. smegmatis. In addition, erm(39) was found to be in the same chromosomal location as erm(38) in their respective hosts. Like erm(38), erm(39) conferred resistance (MIC >128 mg/L) to macrolide-lincosamide (ML) agents, but not to streptogramin B. Analysis of erm gene expression in M. fortuitum showed that ML agents increased erm(39) RNA levels, reaching a steady state level approximately 20-fold higher than baseline. Screening of 32 M. fortuitum clinical isolates by PCR showed that all were positive for erm(39), irrespective of clarithromycin susceptibility. A majority of clarithromycin-susceptible (MIC < or = 2 mg/L) isolates were postulated to carry a disabled erm(39) gene as they had a GTG-->CTG mutation in the putative initiation codon of the erm(39) gene.

CONCLUSIONS

The similarity of the erm genes of M. smegmatis and M. fortuitum suggests that they were inherited from a common ancestor. Although the clinical impact of erm(39) on the therapeutic utility of clarithromycin is unclear, induction of this gene is consistent with the trailing end-points commonly seen during susceptibility testing of M. fortuitum isolates against macrolides.

Hernia repair mesh-associated Mycobacterium goodii infection

We report on a patient with an abdominal wall abscess that developed after an inguinal hernia repair that utilized synthetic mesh. Mycobacterium goodii, a recently recognized, rapidly growing mycobacterium related to M. smegmatis, was isolated both from the abdominal wall aspirate and from surgically drained material. Infection resolved following thorough debridement, mesh removal, and prolonged antimicrobial therapy. This case report extends our understanding of the spectrum of M. goodii infection.