Infections with beta-haemolytic streptococci: detection by a universal PCR for bacterial DNA and DNA sequencing

Advantages and limitations of ribosomal RNA PCR and DNA sequencing for identification of bacteria in cardiac valves of danish patients

Studies on the value of culture-independent molecular identification of bacteria in cardiac valves are mostly restricted to comparing agreement of identification to what is obtained by culture to the number of identified bacteria in culture-negative cases. However, evaluation of the usefulness of direct molecular identification should also address weaknesses, their relevance in the given setting, and possible improvements.

In this study cardiac valves from 56 Danish patients referred for surgery for infective endocarditis were analysed by microscopy and culture as well as by PCR targeting part of the bacterial 16S rRNA gene followed by DNA sequencing of the PCR product. PCR and DNA sequencing identified significant bacteria in 49 samples from 43 patients, including five out of 13 culture-negative cases. No rare, exotic, or intracellular bacteria were identified. There was a general agreement between bacterial identity obtained by ribosomal PCR and DNA sequencing from the valves and bacterial isolates from blood culture. However, DNA sequencing of the 16S rRNA gene did not discriminate well among non-haemolytic streptococci, especially within the Streptococcus mitis group.

Ribosomal PCR with subsequent DNA sequencing is an efficient and reliable method of identifying the cause of IE, but exact species identification of some of the most common causes, i.e. non-haemolytic streptococci, may be improved with other molecular methods.

Osteitis in the dens of axis caused by Treponema pallidum

Background

Syphilis has been referred to as “the great imitator” due to its ability to imitate other diseases. Untreated syphilis becomes a systemic infection that can involve almost every organ systems. Treponema pallidum has a high affinity for bone tissue, but osteitis has mainly been described in late stages of the disease. Vertebral involvement is rare, and this is to our knowledge the first case describing syphilitic spondylitis in early acquired syphilis.

Case presentation

We here describe destructive osteitis in the vertebral column as the initial manifestation of early acquired syphilis in a 24-year-old caucasian homosexual male with HIV infection. The diagnosis was reached by universal bacterial PCR and DNA sequencing of the DNA product. It was confirmed by PCR specific for Treponema pallidum, immunohistochemistry and detection of increasing antibody titer.

Conclusions

As syphilis has re-emerged in Western countries and remains a worldwide common disease it is important to have in mind as a causative agent of skeletal symptoms, especially among HIV-infected individuals or men who have sex with men (MSM).

Ribosomal PCR and DNA sequencing for detection and identification of bacteria: experience from 6 years of routine analyses of patient samples

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.