Laboratory diagnosis, treatment and prevention of Leptospira interrogans


Leptospira interrogans is a spirochete bacterium that causes leptospirosis, a zoonotic disease that affects humans and animals. Leptospirosis can manifest as a mild flu-like illness or a severe multisystemic infection that can lead to organ failure and death. The diagnosis of leptospirosis is challenging because of the nonspecific clinical presentation, the wide range of potential sources of exposure, and the diversity of serological and molecular methods available. In this article, we will review the main laboratory techniques for the detection and identification of Leptospira interrogans in clinical specimens.

The laboratory diagnosis of leptospirosis can be divided into two main approaches: direct and indirect. Direct methods aim to detect the presence of the bacterium or its components in the specimens, while indirect methods measure the host immune response to the infection.

Direct methods include microscopy, culture, and molecular techniques. Microscopy involves the examination of specimens under darkfield or immunofluorescence microscopy to visualize the thin and motile spirochetes. However, microscopy has several limitations, such as low sensitivity, low specificity, and dependence on skilled personnel and equipment. Culture involves the inoculation of specimens into special media that support the growth of Leptospira interrogans. Culture is considered the gold standard for direct diagnosis, as it allows for isolation and identification of the bacterium at the serovar level. However, culture is also time-consuming, labor-intensive, and prone to contamination. Molecular techniques involve the amplification and detection of specific DNA sequences of Leptospira interrogans by polymerase chain reaction (PCR) or other methods. Molecular techniques offer high sensitivity and specificity, rapid results, and potential for genotyping and epidemiological studies. However, molecular techniques are also expensive, require specialized equipment and trained personnel, and may not be widely available in endemic areas.

Indirect methods include serology and antigen detection. Serology involves the measurement of antibodies against Leptospira interrogans in serum samples by various tests, such as microscopic agglutination test (MAT), enzyme-linked immunosorbent assay (ELISA), latex agglutination test (LAT), or immunochromatographic test (ICT). Serology is the most widely used method for diagnosis of leptospirosis, as it is relatively simple, inexpensive, and widely available. However, serology also has some drawbacks, such as cross-reactivity with other pathogens, variability in antibody response among individuals and serovars, and difficulty in distinguishing between acute and past infections. Antigen detection involves the identification of specific antigens of Leptospira interrogans in urine or serum samples by immunological methods, such as ELISA or ICT. Antigen detection offers an advantage over serology in that it can detect active infection before antibody response develops. However, antigen detection also suffers from low sensitivity and specificity, limited availability of commercial kits, and potential interference from other substances in the specimens.

In summary, laboratory diagnosis of leptospirosis requires a combination of different methods that depend on various factors, such as the stage of infection, the type of specimen, the availability of resources, and the purpose of testing. A comprehensive approach that integrates clinical history, epidemiological data, and laboratory results is essential for accurate diagnosis and management of leptospirosis cases.