Mycobacterium ulcerans Experimental Dormancy

Whether Mycobacterium ulcerans, the etiological agent of Buruli ulcer in numerous tropical countries, would exist in a dormant state as reported for closely related Mycobacterium species, has not been established. Six M. ulcerans strains were exposed to a progressive depletion in oxygen for 2 months, using the Wayne model of dormancy previously described for M. tuberculosis, and further examined by microscopy after staining of dynamic, dormant, and dead mycobacteria (DDD staining), microcalorimetry and subculture in the presence of dead and replicative M. ulcerans as controls. Mycobacterium ulcerans CU001 strain died during the progressive oxygen depletion and four of five remaining strains exhibited Nile red-stained intracellular lipid droplets and a 14- to 20-day regrowth when exposed to ambient air, consistent with dormancy. A fifth M. ulcerans 19423 strain stained negative in DDD staining and slowly regrew in 27 days. Three tested M. ulcerans strains yielded microcalorimetric pattern similar to that of the negative (dead) homologous controls, differing from that of the homologous positive (replicative) controls. The relevance of these experimental observations, suggesting a previously unreported dormancy state of M. ulcerans, warrants further investigations in the natural ecological niches where M. ulcerans thrive as well as in Buruli ulcer lesions.

Fecal Excretion of Mycobacterium leprae, Burkina Faso

Mycobacterium leprae was detected by optical microscopy, fluorescent in situ hybridization, and molecular detection in feces collected for the diagnosis of Entamoeba coli enteritis in a leprosy patient in Burkina Faso. This observation raises questions about the role of fecal excretion of M. leprae in the natural history and diagnosis of leprosy.

The puzzle of the evolutionary natural history of tuberculosis

Several pieces of the puzzle of the natural history of tuberculosis are assembled in this review to illustrate the potential reservoirs and sources of the Mycobacterium tuberculosis complex (MTBC) mycobacteria, their transmission to animals and humans, and their fate in populations, in a co-evolutionary perspective. Millennia-old companions of mammalian and human populations, MTBC are detected in the soil, in which they infect and survive within vegetative amoebae and cysts, except for Mycobacterium canettii. Never detected in the sphere of plants, they are transmissible by transcutaneous, digestive and respiratory routes and cause an infection of the lymphatic system with secondary dissemination in most tissues, in which they determine a specific and non-pathognomonic granulomatous inflammatory reaction; in which MTBC survives in dormant form irrespective of MTBC species and mammalian species; indicating that the current epidemiology in mammalian populations is essentially governed by the probabilities of contact between mammalian species and MTBC species. Individual variabilities in clinical expression of tuberculosis are related to MTBC species, strain and inoculum; host genetic factors; acquired modulations of the inflammatory response; and probably human microbiota. This review of the literature suggests an evolutionary natural history of telluric environmental mycobacteria, satellites of unicellular eukaryotes, transmissible to mammals via the digestive and then respiratory tracts, in which they determine a fatal contagious infection that is primarily lymphatic and a quiescence-mimicking encysted form. This review opens perspectives for microbiological and translational medical research.

Microscopic detection of bacillus Calmette-Guérin mycobacteria in bladder biopsy using fluorescence in situ hybridization: Détection microscopique des Bacilles biliés de Calmette et Guérin (BCG) dans une biopsie vésicale par hybridation in situ en fluorescence

Intravesical instillation of Bacilli Calmette Guérin (BCG) as a superficial bladder cancer treatment is generally well tolerated, but local or systemic complications may occur, some of which may be life-threatening. Following the suspicion of post-BCG cystitis in a 72-year-old man with a history of urothelial carcinoma treated by intravesical BCG instillation, we used fluorescence in situ hybridization (FISH) targeting the rpoB gene of the Mycobacterium tuberculosis complex to detect Mycobacterium bovis BCG in paraffin-embedded bladder biopsy sections. FISH yielded specific detection of BCG mycobacteria in the bladder biopsy section, appearing as red-fluorescent bacilli. Treatment with rifampicin, ethambutol and isoniazid is then initiated in combination with corticosteroid therapy.

Methanobrevibacter smithii archaemia in febrile patients with bacteremia, including those with endocarditis

BACKGROUND

The spectrum of infections caused by the emerging opportunistic pathogens methanogens which escape routine detection remains to be described. To determine the prevalence of archaemia, we searched for methanogens in the blood of febrile patients using specific tools.

METHODS

We conducted a prospective study at Institut Hospitalier Universitaire Méditerranée Infection, Marseille, France, September 2018 - April 2020, enrolling 7,716 blood culture samples routinely collected in patients with fever. Blood samples were screened by specific PCR assays for the presence of methanogens. Positive samples were observed by autofluorescence and electron microscopy, analyzed by metagenomics and cultured using previously developed methods. Blood culture bottles experimentally inoculated were used as controls. The presence of methanogens in vascular and cardiac tissues was assessed by indirect immunofluorescence, fluorescent in situ hybridization and PCR-based investigations.

RESULTS

PCR detection attempted in 7,716 blood samples, was negative in all 1,312 aerobic bottles and 810 bacterial culture-negative anaerobic bottles. PCRs were positive in 27/5,594 (0.5%) bacterial culture-positive anaerobic bottles that contained cultures collected from 26 patients. Sequencing confirmed Methanobrevibacter smithii associated with staphylococci in 14 patients, fermentative Enterobacteriaceae in nine patients and streptococci in three patients. Metagenomics confirmed M. smithii in five blood samples, and M. smithii was isolated via culture in broth from two samples; the genomes of these two isolates were sequenced. Blood cultures experimentally inoculated with Enterobacteriaceae, Staphylococcus epidermidis or Staphylococcus hominis yielded hydrogen, but no methane, authentifying observational data.Three patients, all diagnosed with infectious mitral endocarditis, were diagnosed by microscopy, PCR-based detections and culture: we showed M. smithii microscopically and by a specific PCR followed by sequencing method in two of three cardiovascular tissues.

CONCLUSIONS

Using appropriate methods of detection, M. smithii is demonstrated as causing archaemia and endocarditis in febrile patients who are coinfected by bacteria.

Translocation of Mycobacterium tuberculosis after experimental ingestion

Human tuberculosis is a life-threatening infection following the inhalation of Mycobacterium tuberculosis, while the closely related bacteria Mycobacterium bovis and Mycobacterium canettii are thought to be transmitted by ingestion. To explore whether M. tuberculosis could also infect individuals by ingestion, male BALBc mice were fed 2 x 10⁶ CFUs of M. tuberculosis Beijing or phosphate-buffered saline as a negative control, over a 28-day experiment. While eight negative control mice remained disease-free, M. tuberculosis was identified in the lymph nodes and lungs of 8/14 mice and in the spleens of 4/14 mice by microscopy, PCR-based detection and culture. Whole-genome sequencing confirmed the identity of the inoculum and the tissue isolates. In these genetically identical mice, the dissemination of M. tuberculosis correlated with the results of the culture detection of four intestinal bacteria. These observations indicate that ingested M. tuberculosis mycobacteria can translocate, notably provoking lymphatic tuberculosis.

Blood Culture-Negative Cardiovascular Infection in a Patient With Multiple Sclerosis

A patient with multiple sclerosis presented with seronegative C. burnetii endocarditis diagnosed using C. burnetii–specific polymerase chain reaction and fluorescence in situ hybridization on cardiovascular biopsy. This case supports the necessity of a systematic polymerase chain reaction testing of removed cardiac valves because blood culture–negative endocarditis can be pauci-symptomatic, and serological tests can be negative in cases of immunosuppression.

Decrypting the environmental sources of Mycobacterium canettii by high-throughput biochemical profiling

Mycobacterium canettii is a smooth bacillus related to the Mycobacterium tuberculosis complex. It causes lymph nodes and pulmonary tuberculosis in patients living in countries of the Horn of Africa, including Djibouti. The environmental reservoirs of M. canettii are still unknown. We aimed to further decrypt these potential reservoirs by using an original approach of High-Throughput Carbon and Azote Substrate Profiling. The Biolog Phenotype profiling was performed on six clinical strains of M. canettii and one M. tuberculosis strain was used as a positive control. The experiments were duplicated and authenticated by negative controls. While M. tuberculosis metabolized 22/190 (11%) carbon substrates and 3/95 (3%) nitrogen substrates, 17/190 (8.9%) carbon substrates and three nitrogen substrates were metabolized by the six M. canettii strains forming the so-called corebiologome. A total at 16 carbon substrates and three nitrogen substrates were metabolized in common by M. tuberculosis and the six M. canettii strains. Moreover, at least one M. canettii strain metabolized 36/190 (19%) carbon substrates and 3/95 (3%) nitrogen substrates for a total of 39/285 (13%) substrates. Classifying these carbon and nitrogen substrates into ten potential environmental sources (plants, fruits and vegetables, bacteria, algae, fungi, nematodes, mollusks, mammals, insects and inanimate environment) significantly associated carbon and nitrogen substrates metabolized by at least one M. canettii strain with plants (p = 0.006). These results suggest that some plants endemic in the Horn of Africa may serve as ecological niches for M. canettii. Further ethnobotanical studies will indicate plant usages by local populations, then guiding field microbiological investigations in order to prove the definite environmental reservoirs of this opportunistic tuberculous pathogen.

Nine Cases of Methanogenic Archaea in Refractory Sinusitis, an Emerging Clinical Entity

The authors report the cases of 9 patients eventually diagnosed with methanogenic archaea refractory or recalcitrant chronic rhinosinusitis, a condition known to involve various anaerobic bacteria but in which the role of methanogenic archaea is unknown. The authors retrospectively searched these microorganisms by PCR in surgically-collected sinusal pus specimens from patients diagnosed with refractory sinusitis, defined by the persistance of sinus inflammation and related-symptoms for more than 12 weeks despite appropriate treatment. Of the 116 tested sinus surgical specimens, 12 (10.3%) from 9 patients (six females, three males; aged 20-71 years) were PCR-positive. These specimens were further investigated by fluorescence in-situ hybridization, PCR amplicon-sequencing and culture. Methanobrevibacter smithii was documented in four patients and Methanobrevibacter oralis in another four, one of whom was also culture-positive. They were associated with a mixed flora including Gram-positive and Gram-negative bacteria. In the latter patient, "Methanobrevibacter massiliense" was the sole microorganism detected. These results highlight methanogenic archaea as being part of a mixed anaerobic flora involved in refractory sinusitis, and suggest that the treatment of this condition should include an antibiotic active against methanogens, notably a nitroimidazole derivative.

Leprosy in French Polynesia

Leprosy is a neglected endemic infectious disease in the Pacific region. In French Polynesia (FP), leprosy is no longer a public health problem at the national level, defined by the World Health Organization as a prevalence rate below 1 case per 10,000 population. However, even if its incidence has dramatically declined in FP in the last decades, leprosy is still endemic at a low level. Here we present a case of leprosy in a 34-year-old man from FP diagnosed in 2018. Clinical and microbiologic examinations, including fluorescence in-situ hybridization, led to the diagnosis of a multibacillary leprosy, and multidrug therapy was initiated. There is a need to maintain leprosy surveillance and trained medical staff for the detection and treatment of new cases.

Co-culture models illustrate the digestion of Gemmata spp. by phagocytes

Gemmata spp. bacteria thrive in the same aquatic environments as free-living amoebae. DNA-based detection of Gemmata spp. sequences in the microbiota of the human digestive tract and blood further questioned the susceptibility of Gemmata spp. to phagocytes. Here, Gemmata obscuriglobus and Gemmata massiliana were co-cultured with the amoebae Acanthamoeba polyphaga, Acanthamoeba castellanii, Acanthamoeba griffini and THP-1 macrophage-like phagocytes. All experiments were performed in five independant replicates. The ratio amoeba/bacteria was 1:20 and the ratio THP-1/bacteria was 1:10. After a 2-hour co-culture, extracellular bacteria were killed by kanamycin or amikacin and eliminated. The intracellular location of Gemmata bacteria was specified by confocal microscopy. Microscopic enumerations and culture-based enumerations of colony-forming units were performed at T = 0, 1, 2, 3, 4, 8, 16, 24, 48 and 72 hours post-infection. Then, Gemmata bacteria were engulfed into the phagocytes’ cytoplasmic vacuoles, more than (98 ± 2)% of Gemmata bacteria, compared to controls, were destroyed by phagocytic cells after a 48-h co-culture according to microscopy and culture results, and no positive culture was observed at T = 72-hours. Under our co-culture conditions, Gemmata bacteria were therefore susceptible to the environmental and host phagocytes here investigated. These data suggest that these Acanthamoeba species and THP-1 cells cannot be used to isolate G. massiliana and G. obscuriglobus under the co-culture conditions applied in this study. Although the THP-1 response can point towards potential responses that might occur in vivo, these responses should first bevalidated by in vivo studies to draw definite conclusions.

Fluorescence in situ hybridization microscopic detection of Bacilli Calmette Guérin mycobacteria in aortic lesions: A case report

RATIONALE

To improve the diagnosis of life-threatening Bacilli Calmette Guérin (BCG) arterial aneurysm in patients treated by intravesical instillation of BCG vaccine as adjunctive therapy for non-muscular bladder carcinoma, is a life-threatening condition. Its diagnosis remains cumbersome.

PATIENT CONCERNS

One patient with a history of intravesical BCG installation presented with aortic aneurysm with routine microscopic examination after Ziehl-Neelsen staining remaining negative.

DIAGNOSES

We used fluorescence in situ hybridization (FISH) to target the Mycobacterium tuberculosis complex rpob gene in a fresh aortic specimen. FISH yielded fluorescent mycobacteria in aortic lesions; mycobacteria were further confirmed as Mycobacterium bovis BCG mycobacteria by polymerase chain reaction (PCR) sequencing.

INTERVENTIONS

The patient benefited from an antituberculous treatment combining rifampicin, isoniazid, and ethambunol.

OUTCOME

A 9-month follow-up indicated a favorable outcome.

LESSONS

This case report teaches that FISH targeting the M tuberculosis complex rpoB gene should be incorporated in the laboratory investigation of aortic aneurysm in patients with a history of bladder carcinoma.