Evaluation of Mast-ID 15 system for identification of fresh clinical isolates of Enterobacteriaceae and Acinetobacter.

AIMS: To assess the accuracy of the Mast-ID 15 system compared with API 20 E for the identification of stock and fresh clinical strains of Enterobacteriaceae and Acinetobacter spp; to compare the accuracy of 19 pin and 36 pin multipoint inoculator heads. METHODS: One hundred frozen stock cultures of Enterobacteriaceae and Acinetobacter spp which had previously been identified by the API 20E were classified by the Mast-ID using 19 and 36 pin multipoint inoculator heads. Reproducibility was determined by testing 36 randomly selected organisms in duplicate. Four hundred and sixty nine consecutive fresh clinical isolates of Enterobacteriaceae and Acinetobacter spp were identified by the Mast-ID using a 36 pin multipoint inoculator and by the API 20E. Reproducibility for the fresh isolates was determined by testing 96 randomly selected strains in duplicate. RESULTS: The Mast-ID 15 identified 82% and 85% of frozen strains to species level and reproducibility was 80% and 86% using 19 and 36 pin inoculator heads, respectively. Of the 469 fresh clinical isolates, the Mast-ID identified 70% of strains to species level; 19% were not identified and 11% were identified incorrectly by comparison with the API 20E. The Mast-ID achieved a reproducibility level of 80% with the fresh clinical isolates. CONCLUSIONS: The use of a 36 pin multipoint inoculator head in preference to the standard 19 pin head for the Mast-ID was advantageous as it allowed greater numbers of strains to be identified at a reduced cost. Unfortunately, in our hands, the Mast-ID system was insufficiently accurate for routine use in the clinical laboratory. Modifications to some of the problematic tests may result in a sufficient increase in accuracy and reproducibility to make the system beneficial in the routine clinical laboratory.

Comparison of three-compartment Petri dishes and individual plates for routine culture of vaginal swabs.

Recovery of aerobes and facultative anaerobes from 200 consecutive randomly selected high vaginal swabs was evaluated using three-compartment Petri dishes containing Sabouraud, dextrose agar, GC selective agar, and chocolate agar. The method was compared with the traditional method using individual Petri dishes. The two methods produced comparable results both in terms and quantities of organisms recovered from the specimens. As three-compartment Petri dishes use less agar, save time in culturing specimens, yet still maintain the same standard of culture, they provide a more economical alternative to the traditional method for routine culture of vaginal swabs.

The comparative cariogenicity and plaque-forming ability in vivo of four species of the bacterium Actinomyces in gnotobiotic rats.

Gnotobiotic WAG/RIJ rats on a high sucrose diet were monoinfected with 12 strains of Actinomyces spp. Moderate levels of caries were induced by a single strain of Actinomyces naeslundii and low levels by two strains of Actinomyces viscosus, three strains of A. naeslundii and one strain of Actinomyces israelii. No caries was induced by single strains of A. viscosus and A. israelii or by three Actinomyces odontolyticus strains. Only fissure caries was observed. Scanning electron microscopy showed that all strains colonized the fissures and most colonized the lingual surface of the teeth, but to a limited extent. Production of abundant and dense plaque was not always accompanied by caries.

The production of dental plaque and caries by the bacterium Streptococcus salivarius in gnotobiotic WAG/RIJ rats.

The abilities of ten strains of Streptococcus salivarius to colonize rat molars and to induce caries were determined using mono-infected germ-free rats. Scanning electron microscopy revealed the production of micro-colonies and spheroids by Strep. salivarius on exposed surfaces of molar teeth, and abundant dense plaque formation in fissures. Most strains colonized fissures and smooth surfaces as effectively as Streptococcus mutans NCTC 10832, yet produced no buccal or lingual lesions. The four K- strains of Strep. salivarius produced more approximal lesions than the K+ strains but fewer lesions than Strep. mutans. All but one Strep. salivarius strain fell into the high-caries category, together with Strep. mutans. They were all more cariogenic than either Streptococcus milleri NCTC 11169 or Streptococcus faecalis 47.

In-vivo dental plaque-forming ability and relative cariogenicity of the bacteria Streptococcus mitis and Streptococcus sanguis I and II in mono-infected gnotobiotic rats.

Sixteen strains of Streptococcus mitis, Streptococcus sanguis I and Strep. sanguis II were tested for cariogenic potential and in-vivo plaque-forming ability in a gnotobiotic WAG/RIJ rat test system. All strains produced far less fissure plaque in vivo than strains of Streptococcus milleri or Streptococcus mutans. There was less extracellular matrix around cells of Strep. mitis or Strep. sanguis than around Strep. mutans, in the fissures. Dense sheets of cells were observed only with Strep. mutans. Some localized colonization of exposed smooth surfaces occurred with most strains. Strep. mitis produced no caries in three tests, low-caries scores in two tests and high-caries scores in one test. A single strain of Strep. mitis produced a highly-cariogenic variant able to ferment raffinose. Strep. sanguis I induced low-levels of caries in 12 tests; one test of NCTC 7865 produced moderate levels of caries, and another test of 311 produced no caries. Strep. sanguis 311 was dextran-negative. Strep. sanguis II strains induced no caries in three tests, low caries scores in six tests and moderate levels of caries with Strep. sanguis 402. No strain of Strep. mitis or Strep. sanguis was able to induce smooth-surface lesions.