Multiplex PCR on leptospiral isolates from Kolenchery, Kerala, India

Real-time PCR method for the detection of the gene encoding surface lipoprotein LipL32 of pathogenic Leptospira: use in the laboratory diagnosis of the acute form of leptospirosis

BACKGROUND

The aims of this work were to replace the obsolete PCR method for the laboratory diagnosis of the acute form of leptospirosis using the G1, G2 and B64 I, B64 II primers, and to improve the PCR detection time.

METHODS

We introduced a real-time PCR method for the detection of the gene encoding the surface lipoprotein LipL32 of pathogenic Leptospira into our laboratory diagnosis of the acute form of leptospirosis. The positive and negative analytical specificities of the real-time PCR method were both equal to 100%; the detection limit was determined to be 1-5 genome copies/1 ml of liquid biological material. The method was further validated on 230 laboratory strains of leptospires.

RESULTS

All laboratory strains of pathogenic Leptospira were evaluated as LipL32-positive and all non-pathogenic strains as LipL32-negative. In addition, 455 biological materials (253 plasma, 121 urine, 72 cerebrospinal fluid (CSF), 7 bronchoalveolar lavage, and 2 sputum) from 295 patients with suspected leptospirosis were examined. From this set of patients, 9 were evaluated to be LipL32-positive, from 15 positive biological materials (10 urine, 4 blood plasma, and 1 CSF).

CONCLUSIONS

This real-time PCR method for the detection of the gene encoding the surface lipoprotein LipL32 is a reliable, sensitive, and rapid method for the detection of the acute form of leptospirosis.

Leptospirosis: possibilities of early laboratory and clinical diagnosis

This retrospective study aims to identify and describe the problems associated with the laboratory and clinical diagnosis of leptospirosis. A total of 4,813 patients with suspected leptospirosis from an area of the Czech Republic, with a total population of 1.15 million, were examined during the period 2002–2010. Our study included only 855 patients: 545 men (mean age 41.03 ± 19.24) and 310 women (mean age 41.47 ± 20.3) who were examined using microscopic agglutination test (MAT) and a polymerase chain reaction (PCR). All patients and their physicians filled in questionnaires, which included anamnestic data, clinical symptoms and the results of laboratory tests. Out of total suspected, 89 patients (1.85%), tested positive for leptospirosis, of which 50 have been examined only serologically by MAT. Of 855 patients in our study undergoing both PCR and MAT tests, 39 have tested positive for leptospirosis. The most frequent symptom in patients with leptospirosis included fever (91.6%) and headache (69.4%). The correct laboratory diagnosis of leptospirosis depends on biological material being tested before the start of antibiotic treatment, since leptospires are extremely sensitive to antibiotics. Consequently, the PCR results alone may produce a false negative result after 24 hours following treatment with antibiotics.

FlaB PCR-based identification of pathogenic leptospiral isolates

BACKGROUND/PURPOSE

The genus Leptospira comprises pathogenic and saprophytic strains. Conventional methods for the identification of pathogenic leptospiral isolates are cumbersome and laborious. In view of these limitations, the search for alternative methods have been focused on DNA based techniques. In this study, we have developed an effective method for the rapid identification of pathogenic and saprophytic leptospiral isolates based on DNA-based techniques.

METHODS

A polymerase chain reaction(PCR)-based approach was developed using specific primer sets (flaB, G1-G2, B64I-II, and A-B) to differentiate pathogenic and saprophytic leptospiral strains. Fifty-five leptospiral isolates were used for this study. The pathogenic status of the isolates was compared with the results obtained using conventional techniques, which included growth in the presence of 8-azaguanine and growth at 13 degrees C.

RESULTS

In this analysis, 46 leptospiral isolates were confirmed as pathogenic and nine were confirmed as saprophytic. PCR with the A-B primer set yielded an amplified product of 331 bp in all of the pathogenic and saprophytic isolates. The other primer sets, G1-G2, B64I-II and flaB, yielded products of 258 bp, 568 bp, and 793 bp, respectively, exclusively for the pathogenic leptospiral strains. None of the saprophytic strains yielded products with these primer sets.

CONCLUSION

The flaB-specific primers consistently yielded an amplification product for all of the pathogenic leptospiral isolates, indicating the presence of the flaB gene only among pathogenic leptospires, and making this a useful tool for distinguishing between pathogenic and saprophytic leptospires. The efficiency of PCR-based identification corroborates the implementation of these techniques for the identification of pathogenic and saprophytic leptospiral strains.

Nested polymerase chain reaction for detection of pathogenic leptospires

Leptospirosis is a widespread zoonosis caused by pathogenic members of the genus Leptospira that has a great impact on human and veterinary public health. Early diagnosis of leptospirosis is important because severe lepto spiral infection can have a fulminant course. The available serological techniques for the diagnosis of leptospirosis have low sensitivity during the early stage of the disease. Efforts are being made to develop simpler, effective, efficient, and inexpensive diagnostic methods. In this work, we first evaluate a polymerase chain reaction (PCR) based method for diagnosis of leptospirosis. Primers were designed to amplify a 264 bp region within the lipL32 gene that is conserved among pathogenic Leptospira and absent in nonpathogenic species. The sensitivity and specificity of the assay were evaluated using 7 saprophytic serovars, 37 pathogenic serovars, and 15 other microorganisms. The method was very specific for pathogenic serovars, however, it lacked sensitivity. To enhance the sensitivity, another primer pair was designed to amplify a 183 bp region within the 264 bp region of the lipL32 gene and was used in a nested PCR assay. This approach was much more sensitive than conventional PCR.Key words: leptospirosis, diagnosis, nested PCR, lipL32.