Raman spectroscopy-based identification of nosocomial outbreaks of the clonal bacterium Escherichia coli.

DNA-based techniques are frequently used to confirm the relatedness of putative outbreak isolates. These techniques often lack the discriminatory power when analyzing closely related microbes such as E. coli. Here the value of Raman spectroscopy as a typing tool for E. coli in a clinical setting was retrospectively evaluated.

Chlamydia trachomatis respiratory infection in Dutch infants.

Chlamydia trachomatis is the most common bacterial pathogen causing sexually transmitted infections in Dutch adults. As prenatal screening for C trachomatis and treatment of pregnant women is not routine practice in The Netherlands, perinatal transmission of C trachomatis may therefore occur. The presence of C trachomatis in infants less than 6 months of age who presented with respiratory complaints to the Erasmus MC-Sophia hospital was evaluated. Respiratory specimens, primarily nasopharyngeal swabs, were tested for C trachomatis, respiratory viruses and Mycoplasma pneumoniae using PCR, viral isolation in cell cultures and direct immunofluorescence. C trachomatis respiratory tract infection was confirmed to be relatively common with detection in 10 of 148 (7%) infants tested. C trachomatis had not been tested for by the attending physicians, but was the second most frequently detected respiratory pathogen after human Respiratory Syncitial Virus, which was found in 41 (28%) infants.

Use of pooled urine samples and automated DNA isolation to achieve improved sensitivity and cost-effectiveness of large-scale testing for Chlamydia trachomatis in pregnant women.

The success of large-scale screening for Chlamydia trachomatis depends on the availability of noninvasive samples, low costs, and high-quality testing. To evaluate C. trachomatis testing with pregnant women, first-void urine specimens from 750 consecutive asymptomatic pregnant women from the Rotterdam area (The Netherlands) were collected. Initially, we investigated the performance of three different DNA isolation methods with 350 of these urines and 70 pools of 5 of the same subset of urine samples. The routinely used COBAS AMPLICOR test was compared to the COBAS AMPLICOR test with prior DNA isolation by use of the MagNA Pure large-volume kit and the MagNA Pure bacterial DNA isolation kit. The latter combination provided the best DNA test for pooled urines, with a sensitivity twice that of the other methods. Next, using all 750 urines, the COBAS AMPLICOR performance for individual testing was compared to pooled testing with the standard COBAS AMPLICOR procedure and subsequently to pooled testing with COBAS AMPLICOR in combination with the MagNA Pure bacterial DNA isolation kit. The sensitivity of COBAS AMPLICOR was 65% on individual and 42% on pooled urines but improved to 92% on pooled urines with the MagNA Pure bacterial DNA isolation kit, making this combination the best screening method. The C. trachomatis prevalence in this population appeared to be 6.4%. Additionally, the cost of the combined MagNA Pure bacterial DNA isolation kit and COBAS AMPLICOR method on pooled urines was only 56% of the cost of the standard COBAS AMPLICOR test applied to individual urines. Costs per positive case detected in the combined method were 39% of standard costs.

Detection of Mycoplasma pulmonis in experimentally infected laboratory rats by 16S rRNA amplification.

Recently, an rRNA-based polymerase chain reaction (PCR) has been developed for the detection of murine mycoplasmas at both the genus and species level (F. J. M. van Kuppeveld, J. T. M. van der Logt, A. F. Angulo, M. J. van Zoest, W. G. V. Quint, H. G. Niesters, J. M. D. Galama, and W. J. G. Melchers, Appl. Environ. Microbiol. 58:2606-2615, 1992). In this study, the diagnostic value of this PCR assay for the detection of Mycoplasma pulmonis in infected rats was studied. For this purpose, 25 Wistar rats were infected intranasally with M. pulmonis strain M72-138 and investigated for the presence of this pathogen by both in vitro isolation and PCR. Five rats were monitored longitudinally by screening of throat swabs at several time points for up to 248 days postinfection. The remaining 20 rats were killed between 3 and 87 days postinfection, and organism recovery from both throat and urogenital tract specimens was attempted. M. pulmonis could be detected in the throat for up to 248 days postinfection but not in the urogenital tract, either by culture or by PCR. PCR proved to be the optimal method for testing throat samples. All samples in which M. pulmonis was detected by culture were also positive by PCR. By PCR, M. pulmonis was also detected in 3.7% of the samples which were culture negative and in 9.9% of the samples from which cultures were overgrown with bacteria. The results of this study demonstrate the suitability of PCR for the detection of mycoplasmal infection in rodents.