Emergence of Mycobacterium simiae in respiratory specimens

Nontuberculous mycobacteria in cystic fibrosis patients on the Island of Gran Canaria. A population study

OBJECTIVE

To determine the prevalence of nontuberculous mycobacteria (NTM) colonization and disease in cystic fibrosis (CF) patients.

PATIENTS AND METHODS

All the CF patients followed-up from 2002 to 2012 with three acid-fast bacilli (AFB) cultures were included. The American Thoracic Society (ATS) criteria for NTM lung disease were applied.

RESULTS

Forty-four of the 53 patients being followed-up were included. The mean time of follow-up was 7.0 years. A total of 18 patients (40.9%) were NTM positive. The NTN mean annual prevalence was 14.1%. The risk of Mycobacterium abscessus complex was higher in the group of 10-14 years-old (p < 0.001). Ten patients (22.7% of the entire cohort) met the ATS microbiological criteria. The mean annual prevalence of NTM disease was 10.4%. Seven patients (four with Mycobacterium simiae and three with M. abscessus complex) with multiple positive cultures, positive AFB smears and clinical worsening were treated. Three patients with M. simiae and none of those with M. abscessus were cured.

CONCLUSIONS

Overall NTM prevalence of colonization and disease were high in our CF patients. Patients <15 years old had a higher risk of M. abscessus complex colonization. Multiple positive cultures or positive AFB smears were associated with disease.

Changing Epidemiology of the Respiratory Bacteriology of Patients With Cystic Fibrosis

BACKGROUND

Monitoring potential changes in the epidemiology of cystic fibrosis (CF) pathogens furthers our understanding of the potential impact of interventions.

METHODS

We performed a retrospective analysis using data reported to the Cystic Fibrosis Foundation Patient Registry (CFFPR) from 2006 to 2012 to determine the annual percent changes in the prevalence and incidence of selected CF pathogens. Pathogens included Pseudomonas aeruginosa, methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S aureus (MRSA), Haemophilus influenzae, Burkholderia cepacia complex, Stenotrophomonas maltophilia, and Achromobacter xylosoxidans. Changes in nontuberculous mycobacteria (NTM) prevalence were assessed from 2010 to 2012, when the CFFPR collected NTM species.

RESULTS

In 2012, the pathogens of highest prevalence and incidence were MSSA and P aeruginosa, followed by MRSA. The prevalence of A xylosoxidans and B cepacia complex were relatively low. From 2006 to 2012, the annual percent change in overall (as well as in most age strata) prevalence and incidence significantly decreased for P aeruginosa and B cepacia complex, but significantly increased for MRSA. From 2010 to 2012, the annual percent change in overall prevalence of NTM and Mycobaterium avium complex increased.

CONCLUSIONS

The epidemiology of CF pathogens continues to change. The causes of these observations are most likely multifactorial and include improvements in clinical care and infection prevention and control. Data from this study will be useful to evaluate the impact of new therapies on CF microbiology.

Molecular epidemiology of nontuberculous mycobacteria isolates from clinical and environmental sources of a metropolitan city

INTRODUCTION

While NTM infection is mainly acquired from environmental exposure, monitoring of environmental niches for NTM is not a routine practice. This study aimed to find the prevalence of environmental NTM in soil and water in four highly populated suburbs of Tehran, Iran.

MATERIAL AND METHODS

A total of 4014 samples from soil and water resources were collected and studied. Sediments of each treated sample were cultured in Lowenstein-Jensen medium and observed twice per week for growth rate, colony morphology, and pigmentation. Colonies were studied with phenotypic tests. Molecular analysis was performed on single colonies derived from subculture of original isolates. Environmental samples were compared with 34 NTM isolates from patients who were residents of the study locations.

RESULTS

Out of 4014 samples, mycobacteria were isolated from 862 (21.4%) specimens; 536 (62.1%) belonged to slow growing mycobacteria (SGM) and 326 (37.8%) were rapid growing mycobacteria (RGM). The five most frequent NTM were M. farcinogens (105/862; 12.1%), M. fortuitum (72/862; 8.3%), M. senegalense (58/862; 6.7%), M. kansasii (54/862; 6.2%), and M. simiae (46/862; 5.3%). In total, 62.5% (539/862) of mycobacterial positive samples were isolated from water and only 37.4% (323/862) of them were isolated from soil samples (P<0.05). Out of 5314 positive clinical samples for mycobacteria, 175 (3.2%) isolates were NTM. The trend of NTM isolates increased from 1.2% (13 out of 1078) in 2004 to 3.8% (39 out of 1005) in 2014 (P = 0.0001). The major clinical isolates were M. simiae (51; 29.1%), M. kansasii (26; 14.8%), M. chelonae (28; 16%), and M. fortuitum (13; 7.4%).

CONCLUSIONS

Comparing the distribution pattern of environmental NTM isolates with clinical isolates suggests a possible transmission link, but this does not apply to all environmental NTM species. Our study confirms an increasing trend of NTM isolation from clinical samples that needs further investigation.

[Infections due to Mycobacterium simiae]

Mycobacterium simiae is a slow-growing photochromogenic environmental mycobacterium, first described in 1965. Rarely associated with human infections, possibly due to its limited pathogenicity, it mainly produces lung infection in immunocompetent elderly patients with underlying lung disease, and in disseminated infections in immunosuppressed young patients with AIDS. A microbiological culture is needed to confirm the clinical suspicion, and genetic sequencing techniques are essential to correctly identify the species. Treating M. simiae infections is complicated, owing to the multiple resistance to tuberculous drugs and the lack of correlation between in vitro susceptibility data and in vivo response. Proper treatment is yet to be defined, but must include clarithromycin combined with other antimicrobials such as moxifloxacin and cotrimoxazole. It is possible that M. simiae infections are undiagnosed.

The changing microbial epidemiology in cystic fibrosis

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Amoebal pathogens as emerging causal agents of pneumonia

Despite using modern microbiological diagnostic approaches, the aetiological agents of pneumonia remain unidentified in about 50% of cases. Some bacteria that grow poorly or not at all in axenic media used in routine clinical bacteriology laboratory but which can develop inside amoebae may be the agents of these lower respiratory tract infections (RTIs) of unexplained aetiology. Such amoebae-resisting bacteria, which coevolved with amoebae to resist their microbicidal machinery, may have developed virulence traits that help them survive within human macrophages, i.e. the first line of innate immune defence in the lung. We review here the current evidence for the emerging pathogenic role of various amoebae-resisting microorganisms as agents of RTIs in humans. Specifically, we discuss the emerging pathogenic roles of Legionella-like amoebal pathogens, novel Chlamydiae (Parachlamydia acanthamoebae, Simkania negevensis), waterborne mycobacteria and Bradyrhizobiaceae (Bosea and Afipia spp.).

Multicenter cross-sectional study of nontuberculous mycobacterial infections among cystic fibrosis patients, Israel

This 2-year cross-sectional evaluation of nontuberculous mycobacterial (NTM) infections involved all Israeli medical centers that treat cystic fibrosis patients. The study comprised 186 patients whose sputum was analyzed for NTM. The prevalence of NTM isolates was 22.6%, and 6.5% and 10.8% of the patients fulfilled the 1997 and 2007 American Thoracic Society criteria for NTM lung disease, respectively. Mycobacterium simiae (40.5%), M. abscessus (31.0%), and M. avium complex (14.3%) were the most prevalent. Presence of Aspergillus spp. in sputum and the number of sputum specimens processed for mycobacteria were the most significant predictors for isolation of NTM (odds ratio [OR] = 5.14, 95% confidence interval [CI] 1.87-14.11 and OR = 1.47, 95% CI 1.17-1.85, respectively). The incidence of NTM pulmonary infections is increasing among cystic fibrosis patients, reflecting the increase in longevity of such patients as well as environmental exposure to various species of mycobacteria.

Pulmonary Mycobacterium simiae infection: comparison with pulmonary tuberculosis

To identify the clinical and radiological features distinguishing Mycobacterium simiae respiratory infection from pulmonary tuberculosis, the demographics, underlying conditions, and clinical and radiological findings of 121 consecutive patients with pulmonary tuberculosis and 102 with M. simiae respiratory infection were compared retrospectively. In the M. simiae group, the patients were older (mean age 69 +/- 16 years vs. 47 +/- 21 years, p = 0.0001), with a female predominance (62% vs. 45%, p = 0.008). Only 4% were of Ethiopian origin compared to 25% of the tuberculosis group (p = 0.0001). M. simiae infection was associated with significantly higher rates of smoking history, underlying chronic obstructive pulmonary disease, zero human immunodeficiency virus (HIV) infection compared to 10% in the tuberculosis group (p = 0.001), blunted symptoms, and noncavitary infiltrates in the lower/middle lobes on chest X-ray. HIV-negative patients with M. simiae respiratory infection are distinguishable from patients with pulmonary tuberculosis by several demographic, clinical, and radiological features. These findings have important diagnostic and therapeutic implications.

Infection withMycobacterium simiaecomplex in four captive Micronesian kingfishers

CASE DESCRIPTION

4 captive adult Micronesian kingfishers (Halcyon cinnamomina cinnamomina) at 3 zoologic institutions were examined routinely or because of dyspnea or lethargy.

CLINICAL FINDINGS

All birds had marked hepatomegaly. Two birds had dyspnea caused by compression of air sacs by the enlarged liver, and 1 bird had generalized weakness and lethargy. Three birds had distended coelomic cavities, and 3 birds were thin or had lost weight. There were no consistent abnormalities in blood analytes. Results of most ancillary diagnostic tests such as acid-fast staining of cloacal or fecal swab specimens and culture of feces for acid-fast bacteria were negative. Results of examination of hepatic biopsy specimens in 2 of 4 birds were suggestive of mycobacteriosis.

TREATMENT AND OUTCOME

3 birds died or were euthanized soon after diagnosis. One kingfisher was isolated and monitored for 4 months without treatment and died during anesthesia for disease monitoring. Postmortem histologic examination revealed histiocytic hepatitis and acid-fast bacteria in all 4 birds. Bacteriologic culture of liver specimens yielded Mycobacterium simiae complex in all 4 birds.

CLINICAL RELEVANCE

Infection with M simiae complex should be considered in ill Micronesian kingfishers, and further monitoring is warranted to determine whether this is an emerging pathogen in this species.