Aspirated intracranial fluid, in the surgical management of intracranial sepsis, may not culture an organism due to the previous administration of antibiotics. We have sought to utilise polymerase chain reaction (PCR) to determine the cause of culture-negative sepsis and in monitoring response to therapy.
This was a retrospective review of five cases of Streptococcus pneumoniae intracranial sepsis. Samples were analysed using real-time quantitative PCR targeting the pneumococcal lytA gene and the number of genome copies per microlitre of sample determined.
Streptococcus pneumoniae sepsis was diagnosed by PCR in five culture-negative cases comprising: ventriculitis (×3), subdural empyema and meningitis. Serial serum inflammatory markers (CRP and WBC) and number of genome copies were graphically plotted over the duration of inpatient stay for cases requiring surgical drainage of recurrent collections or external ventricular drainage. A correlation was demonstrated between change in bacterial genomic load and serum inflammatory markers, reflecting similar changes in clinical state.
This is the first report of the use of serial quantitative PCR in monitoring the course of intracranial sepsis secondary to S. pneumoniae. Further work is required to determine the precise relationship between serum inflammatory markers, clinical state and bacterial load: do changes in one precede the other? Furthermore, a threshold value for number of genome copies in cerebrospinal fluid/aspirate samples has yet to be defined.
[Show abstract][Hide abstract] ABSTRACT: We report the case of a 1-year-old boy with an infected subdural hematoma due to Streptococcus pneumoniae identified by latex agglutination test and polymerase chain reaction amplification of a bacteria-specific gene. The present case demonstrated the need to include infected subdural hematoma in the differential diagnosis of suspected subdural empyema, and suggested the usefulness of combining these methods to identify a causative organism.
Japanese journal of infectious diseases 10/2008; 61(5):412-4. · 1.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Molecular surveillance of pathogens has shown the need for rapid and dependable methods for the identification of organisms of clinical and epidemiological importance. As the leading cause of community-acquired pneumonia, Streptococcus pneumoniae was used as a model organism to develop and refine a real-time fluorescence PCR assay and enhanced DNA purification method. Seventy clinical isolates of S. pneumoniae, verified by latex agglutination, were screened against 26 negative control clinical isolates employing a TaqMan assay on a thermocycler (LightCycler). The probe, constructed from the lytA gene, correctly detected all S. pneumoniae genomes without cross-reaction to negative controls. The speed and ease of this approach will make it adaptable to identification of many bacterial pathogens and provide potential for adaptation to direct detection from patient specimens.
[Show abstract][Hide abstract] ABSTRACT: We have developed a duplex real-time PCR for the rapid diagnosis of Streptococcus pneumoniae infection from culture-negative clinical samples with the simultaneous determination of penicillin susceptibility. The assay amplifies a lytA gene target and a penicillin binding protein 2b (pbp2b) gene target in penicillin-susceptible organisms. The assay was shown to be sensitive (detects 0.5 CFU per PCR) and specific for the detection of S. pneumoniae DNA. The assay was validated by comparing pbp2b PCR results with MIC data for 27 S. pneumoniae isolates. All 5 isolates with penicillin MICs of > 1.0 mg/liter were pbp2b real-time PCR negative, as were 9 of the 10 isolates with penicillin MICs of 0.12 to 1.0 mg/liter. One isolate with a penicillin MIC of 0.12 to 1.0 mg/liter gave an equivocal pbp2b real-time PCR result. Twelve isolates were penicillin susceptible (MICs of < or = 0.06 mg/liter) and pbp2b real-time PCR positive. These data were used to establish an algorithm for the interpretation of penicillin susceptibility from the duplex PCR result. pbp2b real-time PCR results were also compared to an established PCR-restriction fragment length polymorphism (RFLP) method previously applied to these 27 isolates and 46 culture-negative clinical samples (containing S. pneumoniae DNA by broad-range 16S rRNA gene PCR). Discordant results were seen for four isolates and six culture-negative clinical samples, as PCR-RFLP could not reliably detect penicillin MICs of 0.12 to 1.0 mg/liter. We report prospective application of the duplex PCR assay to the diagnosis of S. pneumoniae infection from 200 culture-negative clinical specimens sent to the laboratory for diagnostic broad-range 16S rRNA gene PCR. One hundred six were negative in the duplex PCR. Ninety-four were lytA PCR positive, and 70 of these were also pbp2b PCR positive and interpreted as penicillin susceptible. Fourteen were pbp2b PCR negative and interpreted as having reduced susceptibility to penicillin. For the remaining 10 samples, susceptibility to penicillin was not determined.
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