Laboratory diagnosis of leptospirosis: A challenge

Abstract

Leptospirosis is caused by pathogenic bacteria called leptospires that are transmitted directly or indirectly from animals to humans. It occurs worldwide but is most common in tropical and subtropical areas. It is a potentially serious but treatable disease. Its symptoms may mimic those of a number of other unrelated infections such as influenza, meningitis, hepatitis, dengue, or other viral hemorrhagic fevers. The spectrum of the disease is extremely wide, ranging from subclinical infection to a severe syndrome of multiorgan infection with high mortality. Laboratory diagnosis tests are not always available, especially in developing countries. Numerous tests have been developed, but availability of appropriate laboratory support is still a problem. Direct observation of leptospires by darkfield microscopy is unreliable and not recommended. Isolation of leptospires can take up to months and does not contribute to early diagnosis. Diagnosis is usually performed by serology; enzyme-linked immunosorbent assay and the microscopic agglutination tests are the laboratory methods generally used, rapid tests are also available. Limitation of serology is that antibodies are lacking at the acute phase of the disease. In recent years, several real-time polymerase chain reaction assays have been described. These can confirm the diagnosis in the early phase of the disease prior to antibody titers are at detectable levels, but molecular testing is not available in restricted resources areas.

A Review of Laboratory Diagnosis and Treatment of Leptospirosis

“…Samples for culture should be collected prior to the administration of antibiotics [21]. Samples should be stored and transported at ambient temperatures since low temperatures are detrimental to pathogenic leptospires [22].…”

“…PCR detects DNA in blood in the first 5-10 d after the onset of the disease and up to the 15th day and allows detection of leptospires in culture negative blood if the patient has received an effective antimicrobial drug but have not cleared nonviable organism [21]. Leptospiral DNA has been amplified from serum, urine, aqueous humor, CSF, water and a number of organs post mortem.…”

“…MAT detects both class M and class G antibodies and cannot differentiate between current recent or past infections [21]. It was reported to have a sensitivity of 41% during the 1st week, 82% during the 2nd to 4th week and 96% beyond the 4th week of illness [21].…”

“…It was reported to have a sensitivity of 41% during the 1st week, 82% during the 2nd to 4th week and 96% beyond the 4th week of illness [21]. The method has a good specificity because the presence of heterologous antibodies is not interfering in the results [10].…”

“…The range of antigens used should include serovars representative of all serogroups moreover all locally common serovars and panels of live leptospires belonging to different serovars must be maintained in the laboratory [1,21]. At the Leptospirosis National Reference Center (French acronym CNRL) (Pasteur Institute) 24 strains are used including non-pathogenic strain Leptospira biflexa strain Patoc1 which has for particularity to cross-react with several antigens of pathogenic serogroups.…”