Expanding the Diagnostic Use of PCR in Leptospirosis: Improved Method for DNA Extraction from Blood Cultures

Charité-Universitätsmedizin Berlin, Germany
PLoS ONE (Impact Factor: 3.23). 08/2010; 5(8):e12095. DOI: 10.1371/journal.pone.0012095
Source: PubMed


Leptospirosis is a neglected zoonosis of ubiquitous distribution. Symptoms are often non-specific and may range from flu-like symptoms to multi-organ failure. Diagnosis can only be made by specific diagnostic tests like serology and PCR. In non-endemic countries, leptospirosis is often not suspected before antibiotic treatment has been initiated and consequently, relevant samples for diagnostic PCR are difficult to obtain. Blood cultures are obtained from most hospitalized patients before antibiotic therapy and incubated for at least five days, thus providing an important source of blood for PCR diagnosis. However, blood cultures contain inhibitors of PCR that are not readily removed by most DNA-extraction methods, primarily sodium polyanetholesulfonate (SPS).
In this study, two improved DNA extraction methods for use with blood cultures are presented and found to be superior in recovering DNA of Leptospira interrogans when compared with three previously described methods. The improved methods were easy and robust in use with all tested brands of blood culture media. Applied to 96 blood cultures obtained from 36 patients suspected of leptospirosis, all seven patients with positive convalescence serology were found positive by PCR if at least one anaerobic and one aerobic blood culture, sampled before antibiotic therapy were tested.
This study suggests that a specific and early diagnosis can be obtained in most cases of severe leptospirosis for up to five days after initiation of antimicrobial therapy, if PCR is applied to blood cultures already sampled as a routine procedure in most septic patients.

Download full-text


Available from: Karen Angeliki Krogfelt
  • Source
    • "The BCs were subjected to an improved benzyl alcohol and column based DNA extraction protocol as previously described (Villumsen et al., 2010). By this method the DNA from the blood culture is diluted to 49 to 66% of the input concentration. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In the acute phase of leptospirosis, the diagnosis can be established with high sensitivity by testing blood and urine samples with polymerase chain reaction (PCR). However, only few real-time PCR assays have been validated for diagnostic use. The diagnostic accuracy of a novel TaqMan® PCR (LipL32 real-time PCR) targeting the lipl32 gene (or hap-1) and a previously described TaqMan® PCR (16S real-time PCR) targeting the rrs gene coding for 16S rRNA was evaluated when applied to both urine and blood specimens from humans suspected of leptospirosis. Applied to at least two blood cultures LipL32 real-time PCR had a sensitivity of 86%, and a specificity of 100%; and 16S real-time PCR had a sensitivity of 100%, and a specificity of 97%. Applied to urine samples, patients that were positive by the reference methods were also positive by both real-time PCR assays (n=4). For LipL32 real-time PCR the specificity was 100%, while for 16S real-time PCR it was only 91.5% due to unexpected cross-reactions with other bacteria. The analytical sensitivity was close to the theoretical limit-of-detection for both assays detecting all described human pathogenic species. We report a specific real-time PCR assay for detection of Leptospira, i.e., LipL32 real-time PCR that has been validated for diagnostic application in both urine and blood specimens from humans. We further show that a previously described 16S real-time PCR no longer can be recommended for diagnostic use due to a low specificity.
    Full-text · Article · Jun 2012 · Journal of microbiological methods
  • Source

    Preview · Article · Jan 2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: The use of broad range PCR and DNA sequencing of bacterial 16S ribosomal RNA genes for routine diagnostics of bacterial infections was evaluated. Here, the results from more than 2600 analyses during a 6-year period (2003-2009) are presented. Almost half of the samples were from joints and bones, and the second most frequent origin of samples was from the central nervous system. Overall, 26% of all samples were positive for bacterial DNA and bacterial identification was obtained in 80% of the PCR-positive samples by subsequent DNA sequencing. Ambiguous species identification was noticed among non-haemolytic streptococci, especially within the mitis group. The data show that ribosomal PCR with subsequent DNA sequencing of the PCR product is a most valuable supplement to culture for identifying bacterial agents of both acute and prolonged infections. However, some bacteria, including non-haemolytic streptococci, may not be precisely identified.
    No preview · Article · Jul 2013 · Apmis
Show more