Fluorescent Hybridization of Mycobacterium leprae in Skin Samples Collected in Burkina Faso

Fluorescence In Situ Hybridization (FISH) Tests for Identifying Protozoan and Bacterial Pathogens in Infectious Diseases

Diagnosing and treating many infectious diseases depends on correctly identifying the causative pathogen. Characterization of pathogen-specific nucleic acid sequences by PCR is the most sensitive and specific method available for this purpose, although it is restricted to laboratories that have the necessary infrastructure and finance. Microscopy, rapid immunochromatographic tests for antigens, and immunoassays for detecting pathogen-specific antibodies are alternative and useful diagnostic methods with different advantages and disadvantages. Detection of ribosomal RNA molecules in the cytoplasm of bacterial and protozoan pathogens by fluorescence in-situ hybridization (FISH) using sequence-specific fluorescently labelled DNA probes, is cheaper than PCR and requires minimal equipment and infrastructure. A LED light source attached to most laboratory light microscopes can be used in place of a fluorescence microscope with a UV lamp for FISH. A FISH test hybridization can be completed in 30 min at 37 °C and the whole test in less than two hours. FISH tests can therefore be rapidly performed in both well-equipped and poorly-resourced laboratories. Highly sensitive and specific FISH tests for identifying many bacterial and protozoan pathogens that cause disease in humans, livestock and pets are reviewed, with particular reference to parasites causing malaria and babesiosis, and mycobacteria responsible for tuberculosis.

Whole genome sequence of bacteremic Clostridium tertium in a World War I soldier, 1914

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This original article is the first report of isolate and culture of a bacterium from ancient human samples and dental pulp in particular.

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The dental pulp is a mirror of the individual's infectious state at the time of death.

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Ancient dental pulp culture yielded to the identification and isolation of the bacterium Clostridium tertium responsible for septicaemia during World War I,.

Background

Dental pulp, encapsulating a blood drop, could be used to diagnose pathogen bacteraemia in archaeological materials using DNA-based techniques. We questioned the viability of such ancient pathogens preserved in ancient dental pulp.

Methods

After meticulous decontamination of 32 teeth collected from 31 World War I soldiers exhumed in Spincourt, France, dental pulps were extracted and cultured under strict anaerobiosis. Colonies were identified by mass spectrometry and whole genome sequencing. Fluorescent in situ hybridisation (FISH) was used for the direct microscopic detection of pathogens of interest in the dental pulp. All the experimental procedures included negative controls, notably sediments in contact with individual SQ517 to ensure that results did not arise from contamination.

Findings

Clostridium tertium was detected by FISH in two dental pulp specimens taken from a 1914 soldier. After a two-day incubation period, both dental pulp samples grew colonies identified by mass spectrometry and genome sequencing as C. tertium; whereas negative controls remained free of C. tertium in all the observations, and no C. tertium was founded in sediments. Skeletal remains of this soldier exhibited two notches in the left tibia evocative of a cold steel wound, and a probably fatal unhealed bullet impact in the hip bone.

Interpretation

Data indicated the presence of C. tertium in the dental pulp at the time of the death of one World War I soldier, in 1914. This observation diagnosed C. tertium bacteraemia, with war wounds as the probable portal of entry for C. tertium. Our C. tertium strains ante-dated by three years, the princeps description of this deadly opportunistic pathogen.

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.

Mycobacterium leprae: Pathogenesis, diagnosis, and treatment options

Mycobacterium leprae is known to cause leprosy, a neurological and dermatological disease. In the past 20 years, 16 million leprosy cases have been recorded and more than 200,000 new cases were registered each year, indicating that the disease is still progressing without hindrance. M. leprae, an intracellular bacterium, infects the Schwann cells of the peripheral nervous system. Several types of leprosy have been described, including indeterminate, tuberculoid, borderline tuberculoid, mid-borderline, borderline lepromatous and lepromatous, and three different forms of leprosy reactions, namely type 1, 2 and 3, have been designated. Microscopic detection, serological diagnostic test, polymerase chain reaction and flow tests are employed in the diagnosis of leprosy. The recommended treatment for leprosy consists of rifampicin, dapsone, clofazimine, ofloxacin and minocycline and vaccines are also available. However, relapse may occur after treatment has been halted and hence patients must be educated on the signs of relapse to allow proper treatment and reduce severity. In this review, we depict the current understanding of M. leprae pathogenicity, clinical aspects and manifestations. Transmission of leprosy, diagnosis and treatment are also discussed.