Comparison of three different PCR-based methods to predict the penicillin nonsusceptibleStreptococcus pneumoniaeisolates from China

Time window for positive cerebrospinal fluid broad-range bacterial PCR and Streptococcus pneumoniae immunochromatographic test in acute bacterial meningitis

BACKGROUND

Reliable microbiological tests are essential for the diagnosis of acute bacterial meningitis (ABM). In this study we investigated the time period after the start of antibiotic therapy during which culture, polymerase chain reaction (PCR) and the immunochromatographic test (ICT) are able to detect bacteria in cerebrospinal fluid (CSF).

METHODS

The study was performed on CSF samples from adults with ABM admitted to the Department of Infectious Diseases, Sahlgrenska University Hospital, Gothenburg, Sweden, from January 2007 to April 2014. In addition to the initial lumbar puncture (LP), the participants underwent one or two more LPs during 10 days following the start of antibiotics. The analyses performed on the CSF samples were culture, PCR and ICT.

RESULTS

The study comprised 70 CSF samples from 25 patients with ABM. A bacterium could be identified by CSF culture in 44%, by blood culture in 58% and by PCR in 100% of the patients. There were no positive CSF cultures in samples taken later than the day of starting antibiotics. PCR was positive in 89% on days 1-3, 70% on days 4-6 and 33% on days 7-10. For cases of pneumococcal meningitis, the ICT was positive in 88% on days 1-3, 90% on days 4-6 and 75% on days 7-10.

CONCLUSIONS

This study shows that PCR is highly sensitive for bacterial detection in CSF samples taken up to 1 week into antibiotic therapy. The ICT is highly sensitive for the detection of pneumococci in CSF samples taken during the first week of antibiotic treatment.

Molecular analysis of pbp2b in Streptococcus pneumonia isolated from clinical and normal flora samples

Streptococcus pneumoniae is an important bacterial pathogen responsible for respiratory infections, bacteraemia, and meningitis remains an important cause of disease and mortality in infants and younger children around the world, with penicillin being considered the drug of choice for the treatment of infections. However, penicillin-resistant S. pneumonia is now becoming endemic worldwide. In this study, a total of 80 pneumococcal isolates were collected from different clinical sources as well as normal flora. These isolates were subjected to antimicrobial susceptibility testing and MIC determination. The penicillin-binding proteins, pbp2b, were amplified by PCR, and they were sequenced. The genetic relationship of the penicillin-resistant isolates was performed by BOX PCR. Overall, 36 pneumococcal (45 %) isolates were found to be resistant to penicillin with different MICs. The majority of them (80 %) were intermediately resistant with MIC of 0.12-1 µg/ml, whereas 20 % of isolates were penicillin resistant with MICs of >2 µg/ml. The results identified seven groups which were based on the amino acid substitutions of pbp2b. Sequencing analysis revealed that the most prevalent mutation was the substitution of Adenine for Thymine at the position 445 which is next to the second PBP2b-conserved motif (SSN). This study indicates that resistance to penicillin appears to be dependent on specific mutations in pbp2b, and the substitution in S620 → T near to the third PBP2b-conserved motif appears to be important in developing highly antibiotic-resistant isolates. Moreover, there was a positive correlation between the mutations in pbp2b gene and MIC.