PCR primers that target the bacterial 16S rRNA genes (or the tuf gene for the genus Enterococcus) were used to identify 10 putative bacterial pathogens in root canals with necrotic pulp. In addition, the associations of these microorganisms with symptoms and a history of diabetes mellitus were investigated. Microbial samples from the root canals of 24 teeth with necrotic pulp were included in the study. PCR with universal bacterial primers identified bacterial DNA in 22 specimens; the remaining 2 specimens were from intact teeth that had been traumatized 6 months prior to treatment. PCR with specific primers showed that preoperative symptoms were significantly associated with the presence of Streptococcus spp. (P < 0.001 by chi-square analysis). There was also a nonsignificant trend for symptoms to be associated with Fusobacterium nucleatum and Porphyromonas gingivalis (odds ratio, >2) and for diabetes mellitus to be associated with P. gingivalis and Porphyromonas endodontalis (odds ratio, >2). Cloning and sequencing of the universal PCR product in one specimen revealed the presence of an organism related to the genus Olsenella, which has not previously been described in endodontic infections.

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A total of 122 human and animal Salmonella Typhimurium DT104 isolates and 6 epidemiologically related DT104b isolates from human and animal products were analysed by pulsed-field gel electrophoresis (PFGE). Genomic DNA was subjected to macrorestriction with three enzymes, SpeI, SfiI and XbaI. A total of 14 restriction fragment length polymorphism (RFLP) profiles were identified when the PFGE patterns from the three enzymes were combined. The majority of isolates (81.2%) exhibited the same RFLP profile. Six animal DT104 isolates, susceptible to enrofloxacin and resistant to naladixic acid, were identified from the antibiotic susceptibility test. Four of these isolates had a different PFGE profile from the common RFLP. In addition, 4 of the 6 isolates were geographically clustered in one region. It was concluded that there was one predominant strain of S. Typhimurium DT104 in Ireland and that the potential and selection pressures for emergence of fluoroquinolone-resistant isolates were present.

Uncontrolled or poorly controlled diabetes mellitus may be a risk factor for the development of large and/or debilitating periapical infections. The objectives of this investigation were to: (i) determine the effect of diabetes mellitus on the pathogenesis of periapical lesions with or without specific bacterial inoculations at the exposure sites, and (ii) test the sensitivities of two microbiological techniques in detecting the persistence of the bacterial inoculum in exposed pulps of nonobese diabetic (NOD) mice. Periapical lesions were induced in first molars of 29 female NOD mice and 31 BALB/c controls. Acute (1-2 wk) or chronic (5 wk) exposures were either inoculated with a mixture of facultative and anaerobic bacteria or exposed to oral flora without inoculations. After death the teeth in the chronic groups were analyzed for the presence of the inoculated bacteria by culturing and by polymerase chain reaction amplification of 16S rDNA. Periapical lesion size was measured histomorphometrically and the interleukin-6 content was measured immunohistochemically. The mortality among NOD mice with inoculated and sealed exposures was 83%, compared with 29% for BALB/c mice. In the inoculated and uninoculated chronic NOD mice groups, 38% of the animals versus none of the BALB/c mice died. The chronic uninoculated NOD mice lost significantly more weight at the time of death than controls. Polymerase chain reaction was more sensitive than culturing in detecting the inoculated anaerobic bacteria. In the animals that survived to the predetermined time periods, lesion size and interleukin-6 content in NOD and BALB/c mice were not statistically different.