Broad-range bacterial detection and the analysis of unexplained death and critical illness

Abstract

Broad-range rDNA polymerase chain reaction (PCR) provides an alternative, cultivation-independent approach for identifying pathogens. In 1995, the Centers for Disease Control and Prevention initiated population-based surveillance for unexplained life-threatening infections (Unexplained Death and Critical Illness Project [UNEX]). To address the causes of UNEX cases, we examined 59 specimens from 46 cases by using broad-range bacterial 16S rDNA PCR and phylogenetic analysis of amplified sequences. Specimens from eight cases yielded sequences from Neisseria meningitidis (cerebrospinal fluid from two patients with meningitis), Streptococcus pneumoniae (cerebrospinal fluid from one patient with meningitis2 and pleural fluid from two patients with pneumonia), or Stenotrophomonas maltophilia (bone marrow aspirate from one patient with pneumonia). Streptococcus pneumoniae rDNA sequence microheterogeneity was found in one pleural fluid specimen, suggesting the presence of multiple strains. In conclusion, known bacterial pathogens cause some critical illnesses and deaths that fail to be explained with traditional diagnostic methods.

Figure

Phylogenetic analysis of the bacterial 16S rDNA sequences obtained from cases XEB44 and XMN22. The tree was rooted with Staphylococcus aureus and Escherichia coli as outgroups and constructed with a maximum-likelihood algorithm using 468 homologous sequence positions that were selected from a sequence dataset of 497 total positions. Streptococcus pneumoniae clinical isolates sequenced for this study are marked as SF10175, SF10314, and SF10014. GenBank database accession numbers for published sequences are given in parentheses. All six sequences from the case XCA73 cerebrospinal fluid were identical to those of the S. pneumoniae reference strain (accession no. AJ001246). PCR = polymerase chain reaction.