Routine postoperative antibiotic prophylaxis is not recommended for third molar extractions. However, amoxicillin still continues to be used customarily in several clinical practices worldwide to prevent infections. A prospective cohort study was conducted in cohorts who underwent third molar extractions with (group EA, n = 20) or without (group E, n = 20) amoxicillin (250 mg three times daily for 5 days). Further, a control group without amoxicillin and extractions (group C, n = 17) was included. Salivary samples were collected at baseline, 1-, 2-, 3-, 4-weeks and 3 months to assess the bacterial shift and antibiotic resistance gene changes employing 16S rRNA gene sequencing (Illumina-Miseq) and quantitative polymerase chain reaction. A further 6-month follow-up was performed for groups E and EA. Seven operational taxonomic units reported a significant change from baseline to 3 months for group EA (adjusted p 0.05). In conclusion, the salivary microbiome is resilient to an antibiotic challenge by a low-dose regimen of amoxicillin. Further studies evaluating the effect of routinely used higher dose regimens of amoxicillin on gram-negative bacteria and antibiotic resistance genes are warranted.
We investigated the molecular epidemiology of HIV-1 subtypes in Malaysia among injecting drug users (IDUs) and sexual transmission risk groups, using serologic and genetic techniques. Frozen sera collected at a general hospital, a blood bank, several drug treatment centers, and an STD clinic in Kuala Lumpur, between 1992 and 1996, were investigated retrospectively. V3 peptide serotyping and monomeric gp120 capture serotyping were used to study 89 known HIV-1-infected subjects. The methods differentiate subtypes B, E, and C. V3 peptide and gp120 capture results were comparable. No subtype C-specific reactive sera were found; one specimen was dually reactive for subtypes C and B, using the V3 peptide ELISA; and four were durally reactive for subtypes E and C using this assay. Genotypic analysis of HIV-1 gag RNA in serum was done on a subset of subjects and confirmed serologic findings. HIV-1 subtypes differed significantly by risk category: of 53 IDUs, 29 (55%) were infected with subtype B and 19 (36%) were infected with subtype E, 3 (6%) were dually reactive, and 2 (4%) were not typable. Of 36 persons with heterosexual risks, 29 (81%) were infected with subtype E, 5 (14%) were infected with subtype B, and 2 (5%) were not typable. Persons with IDU risks were significantly more likely to be infected with subtype B than were those with sexual risks (OR 5.89; 95% CI, 1.94-18.54; p < 0.001). Subtypes B and E of HIV-1 appear to predominate in Malaysia; subtype B was more prevalent among IDUs; subtype E was more prevalent among all other groups. These results may have important HIV-1 vaccine implications.