Synthesis and characterization of zinc oxide nanocrystals and histologic evaluation of their biocompatibility by means of intraosseous implants.

AIM: To synthesize and characterize zinc oxide (ZnO) nanocrystals and assess their biological properties for applications in dentistry, particularly in endodontics, by means of intraosseous implants. METHODOLOGY: ZnO nanocrystals were synthesized and characterized by micro-Raman spectroscopy and X-ray Diffraction. Ten guinea pigs were divided into two groups representing experimental periods of 4 and 12 weeks and received implants on both sides of the mandible in the region of the symphysis. The connective tissue response along the lateral wall outside the cup served as the negative control. The animals were euthanized at the end of each observation period and prepared for routine histological examinations which evaluated inflammatory response and material biocompatibility. RESULTS: ZnO nanocrystals were highly pure, crystalline, and averaged 21 nm in size. After 12 weeks, tissue analysis revealed the presence of a thin layer of connective tissue with some giant cells between the implanted material and underlying bone tissue. While signs of mild inflammation could be seen, bone resorption and remodeling were not apparent. CONCLUSION: ZnO nanocrystals were biocompatible, well tolerated and allowed new bone formation and bone remodelling.

A bacteriological and histological evaluation of 58 periapical lesions.

Periapical tissue from 58 cases requiring periapical surgery was examined histologically and cultured for the presence of microbes. Twenty-nine had a possible oral cavity communication and 29 did not. Approximately one-half of each biopsy was submitted for culture while the other portion was examined histologically. Cultures were positive for the presence of bacteria in 51 of 58 cases while bacteria were seen histologically in only 8 of 58 cases. A total of 50 different species of bacteria were isolated from the 58 cultures of periapical tissue. Of 133 isolates, 87 were strict anaerobes, 37 were facultative anaerobes, and 9 were aerobes. Bacteroides species were found in 17 cultures, always with additional bacteria. Seventeen of 58 biopsies contained foreign particulate matter thought to be root canal sealer. Bacteria were found in periapical granulomas, radicular cysts, and a periapical abscess. According to our data, bacteria, foreign material, missed canals, vertical root fractures, and periodontal disease may all contribute to the chronic, non-healing periradicular lesion.

Vibriophage VcA-3 as an epidemic strain marker for the U.S. Gulf Coast Vibrio cholerae O1 clone.

Toxigenic and nontoxigenic Vibrio cholerae O1, El Tor biotype strains, which are endemic to the U.S. Gulf Coast, can be lysogenic for bacteriophage VcA-3. To evaluate the presence of VcA-3 as an indicator of toxigenicity and as an epidemic strain marker, phage production and the presence of phage and cholera toxin genes were assayed in 98 strains of V. cholerae O1 (35 U.S. and 63 foreign strains). By using a HindIII chromosomal digest for Southern blot analysis, 39 of the study strains hybridized with the VcA-3 probe in 10 banding patterns. The 15 toxigenic and 6 of the 20 nontoxigenic U.S. isolates gave four VcA-3-related patterns. Among the foreign isolates, 12 of 12 toxigenic classical biotype strains, 1 of 43 toxigenic El Tor biotype strains, and 3 of 8 nontoxigenic atypical strains gave six patterns that were clearly distinct from that of VcA-3. Compared with Southern blot analysis, the phage production assay had a sensitivity of 1.0 and a specificity of 0.48, while the colony hybridization assay had a sensitivity of 1.0 and a specificity of 0.77 for identification of VcA-3. Neither assay reliably identified the toxigenic Gulf Coast clone. The presence of VcA-3, as defined by Southern blot analysis, always separated toxigenic U.S. from foreign isolates and often from nontoxigenic U.S. isolates of V. cholerae O1.

Comparison of a latex agglutination assay and an enzyme-linked immunosorbent assay for detecting cholera toxin.

To determine the pandemic potential of Vibrio cholerae, one must demonstrate both the presence of O1 antigen and the production of enterotoxin (CT). Tissue culture or enzyme-linked immunosorbent assays (ELISAs) for CT have been limited to research and reference laboratories. A kit for detecting CT by reversed passive latex agglutination is now commercially available and was used to test 168 strains of V. cholerae O1 and non-O1. When compared with the routine ELISA, the latex test was 98% accurate (86 of 88) for serogroup O1 strains and 100% accurate (80 of 80) for non-O1 strains. For both O1 and non-O1 study strains, the sensitivity of the latex agglutination test was 0.97 and the specificity was 1.00 when results were compared with ELISA results. The latex test is commercially available and has the advantages of being less complicated and less time-consuming than the ELISA.

Comparison of adherence and urine growth rate properties of Staphylococcus saprophyticus and Staphylococcus epidermidis.

To compare the adherence properties of Staphylococcus saprophyticus and Staphylococcus epidermidis in vitro studies were conducted with clinical isolates and cell culture monolayers (Hela, Vero, MDCK). Staphylococcus saprophyticus exhibited greater cell adherence, but no significant difference in mean urine growth rate. Its cell-adherence properties seem to explain in part its virulence.

Rapid recognition of methicillin-resistant Staphylococcus aureus by use of automated test systems.

The ability to rapidly recognize methicillin-resistant Staphylococcus aureus by use of two automated instrument systems, the MS-2 system (Abbott Laboratories, Diagnostics Division, Irving, Tex.) and the AutoMicrobic system (Vitek Systems, Hazelwood, Mo.), was evaluated on a collection of 95 methicillin-resistant S. aureus isolates recovered from at least six geographical areas of the United States. Isolates were simultaneously tested with both systems, and the results were compared with MIC tests performed by the National Committee for Clinical Laboratory Standards agar dilution method. Methicillin-resistant S. aureus isolates were defined as those with a methicillin MIC greater than or equal to 8 micrograms/ml by the reference procedure. Overall, with the AutoMicrobic system, 94.7% of 95 methicillin-resistant S. aureus isolates were detected, and with the MS-2 system, 91.6% of the isolates were detected. Isolates with methicillin MICs greater than or equal to 32 micrograms/ml were readily detected with both systems (41 of 42 isolates). Of 53 isolates from three locales with methicillin MICs of 8 or 16 micrograms/ml, 90.6% (48) were detected by the AutoMicrobic system, whereas 86.8% (46) were detected by the MS-2 system. A program update which has been added to the MS-2 system prints a warning message indicating possible methicillin-resistant S. aureus with isolates which demonstrate multiple antibiotic resistance (greater than or equal to four drugs other than methicillin). This warning message would have provided presumptive recognition of six of eight isolates with discrepant results for methicillin by the MS-2 system.

Identification of coagulase-negative staphylococci with the API STAPH-IDENT system.

A group of 300 clinically derived isolates of coagulase-negative staphylococci were tested in parallel with the API STAPH-IDENT system (Analytab Products) and 14 conventional biochemical tests contained in Kloos and Schleifer's simplified scheme for identification of human Staphylococcus species. STAPH-IDENT is a miniaturized biochemical test strip that incorporates four synthetic chromogenic substrates, urea, arginine, and four carbohydrates and that requires only a 5-h test period. Use of the STAPH-IDENT system alone allowed correct or partly correct classification of 67% (201 of 300) of the study isolates. However, if a supplemental test was performed (most often novobiocin susceptibility), correct classification of an additional 25.7% (77) was possible, for a total of 92.7% of isolates identified to the species level. Species correctly identified included 94% (116 of 123) of Staphylococcus epidermidis isolates, 98% (63 of 64) of S. saprophyticus, 71% (34 of 48) of S. hominis, 100% (22) of S. simulans, 100% (18) of S. haemolyticus, 100% (17) of S. warneri, and 100% (8) of S. capitis. Fourteen percent (42 of 300) of profile codes encountered in this study were not included in the STAPH-IDENT profile register, but were included in Analytab Products' expanded computer data base.

Evaluation of the automicrobic system gram-positive identification card for species identification of coagulase-negative staphylococci.

The AutoMicrobic system Gram-Positive Identification Card (Vitek Systems, Inc., Hazelwood, Mo.) was evaluated for identification of a group of 150 isolates of coagulase-negative staphylococci. Identifications obtained with the Gram-Positive Identification Card were compared with reference identifications derived from 15 conventional biochemical tests. The AutoMicrobic system correctly identified only 67.3% (101 of 150) of the test isolates. The greatest accuracy was achieved with Staphylococcus epidermidis isolates (95.7%), whereas Staphylococcus hominis isolates were least often correctly identified (26.7%).

Rapid determination of novobiocin resistance of coagulase-negative staphylococci with the MS-2 system.

Special novobiocin elution disks were prepared for testing of coagulase-negative staphylococci in the MS-2 system (Abbott Laboratories, Diagnostics Div., Irving, Tex.). The MS-2 system correctly classified 91.5% of 82 isolates as either susceptible or resistant to novobiocin in an average time of 5.8 h.

Use of Mueller-Hinton agar to determine novobiocin susceptibility of coagulase-negative staphylococci.

A group of 254 isolates of coagulase-negative staphylococci were tested in parallel for novobiocin susceptibility by using P agar and Mueller-Hinton agar. Zones of inhibition of 16 mm or less around a 5-micrograms novobiocin disk on Mueller-Hinton agar indicated novobiocin resistance, as demonstrated by Staphylococcus saprophyticus.