Point Mutations in the folP Gene Partly Explain Sulfonamide Resistance of Streptococcus mutans.

Cotrimoxazole inhibits dhfr and dhps and reportedly selects for drug resistance in pathogens. Here, Streptococcus mutans isolates were obtained from saliva of HIV/AIDS patients taking cotrimoxazole prophylaxis in Uganda. The isolates were tested for resistance to cotrimoxazole and their folP DNA (which encodes sulfonamide-targeted enzyme dhps) cloned in pUC19. A set of recombinant plasmids carrying different point mutations in cloned folP were separately transformed into folP-deficient Escherichia coli. Using sulfonamide-containing media, we assessed the growth of folP-deficient bacteria harbouring plasmids with differing folP point mutations. Interestingly, cloned folP with three mutations (A37V, N172D, R193Q) derived from Streptococcus mutans 8 conferred substantial resistance against sulfonamide to folP-deficient bacteria. Indeed, change of any of the three residues (A37V, N172D, and R193Q) in plasmid-encoded folP diminished the bacterial resistance to sulfonamide while removal of all three mutations abolished the resistance. In contrast, plasmids carrying four other mutations (A46V, E80K, Q122H, and S146G) in folP did not similarly confer any sulfonamide resistance to folP-knockout bacteria. Nevertheless, sulfonamide resistance (MIC = 50 µ M) of folP-knockout bacteria transformed with plasmid-encoded folP was much less than the resistance (MIC = 4 mM) expressed by chromosomally-encoded folP. Therefore, folP point mutations only partially explain bacterial resistance to sulfonamide.

Root and canal morphology of maxillary first and second permanent molar teeth in a Ugandan population.

AIM: To investigate the root and canal morphology of permanent maxillary molar teeth from a Ugandan population. METHODOLOGY: Maxillary first (n = 221) and second molar (n = 221) teeth were collected from patients attending dental clinics in Kampala. Teeth were prepared using a clearing technique: the pulp chambers were accessed and the teeth placed consecutively into 5% sodium hypochlorite, 10% nitric acid, then methyl salicylate. Indian ink was injected into the pulp chambers to demonstrate the canal system. RESULTS: In the first molars, 95.9% of the teeth had separate roots. The mesiobuccal root was fused with the palatal root in 3% of specimens and with the distobuccal root in 0.5% of teeth. In the second molars, 86% of the teeth had separate roots. The mesiobuccal root was fused with the palatal root in 6.3% of specimens and with the distobuccal root in 6.8% of teeth. Apical deltas were more frequent in the mesiobuccal root when compared with distobuccal and palatal roots of both the first and second molars. A type I canal configuration (>75%) was the most frequent in all the roots of both the first and second molars. Canal intercommunications and lateral canals were more frequent in the mesiobuccal root when compared with other roots. CONCLUSIONS: The mesiobuccal root tended to have more variations in the canal system followed by the distobuccal root, whereas the palatal root had the least. The findings in root and canal morphology of this Ugandan population were different from previous studies, which may partly be attributed to racial differences.

Oral manifestations of HIV/AIDS in clients attending TASO clinics in Uganda.

The objective of the study is to establish the prevalence of oral manifestations and their influence on oral functions. A total of 514 subjects aged 18 to 58 years (mean 42 years) were randomly recruited from five The AIDS Support Organization (TASO) clinics in Uganda. They were clinically examined for oral lesions under field conditions by four trained dentists based on World Health Organization criteria. Women constituted 74.5% of the study population. Oral manifestations were recorded in 72% of the subjects, out of which 70% had candidiasis of pseudomembranous, erythematous, and angular cheilitis variants. Non-Hodgkin's lymphoma, atypical ulcers, necrotizing periodontitis, and hairy leucoplakia were least frequently observed in the subjects. Of those who had oral lesions (n = 370), 68.4% had some form of discomfort in the mouth. Tooth brushing, chewing, and swallowing were frequently associated with discomfort. Reported forms of discomfort were dry mouth, increased salivation, and burning sensation especially on taking salty and spicy foods or acidic drinks. Only 8.5% (n = 44) of the subjects were taking medications specifically for oral lesions, which included antifungal, antiviral, and antibacterial agents. None of the subjects were on antiretroviral therapy. Oral lesions associated with human immunodeficiency virus/acquired immunodeficiency syndrome in TASO clients is a major public health problem requiring education in recognition and appropriate management.

Dental caries among 10- to 14-year-old children in Ugandan rural areas with 0.5 and 2.5 mg fluoride per liter in drinking water.

The purpose of this study was to report on dental caries among Ugandan children residing in rural areas with either a low or high fluoride concentration in the drinking water, and to assess factors associated with caries. A random sample of 481 children aged 10-14 years was selected from Mpondwe (n = 81) and Kyabayenze (n = 82) in the Kasese district with 0.5 mg and from Mutolere/Kagera (n = 163) and Kabindi (n = 155) in Kisoro with 2.5 mg fluoride/l in the drinking water. The children were examined for caries using the DMFT index as described by the World Health Organization in 1987. The mean DMFT was 0.34 in the whole material. In one low fluoride area, Kyabayenze, all children were caries-free compared to 75% to 86% in the other areas. In Kyabayenze, tea with sugar was taken significantly less frequently than in the other low-fluoride area. In the high-fluoride district, age and consumption of tea with sugar were positively and significantly correlated with caries. Multivariate analyses showed age to be the only significant risk indicator.

Assessment of the validity and consequences of different methods of expressing the severity of dental fluorosis in a subject.

The aim was to assess the validity and consequences of different methods of expressing severity of dental fluorosis in a subject. The analyses were based on Ugandan children (n = 481), aged 10-14 years, with life-long consumption of drinking water with either 0.5 or 2.5 mg fluoride per liter. Fluorosis was assessed using the Thylstrup and Fejerskov (TF) index. All children (n = 219) with 28 teeth and fluorosis on at least 1 tooth pair were selected to test methods of expressing fluorosis, e.g. the TF score on the most severely affected tooth, a maxillary central incisor, the median and the mean scores. A test group (n = 40), the 10 most and the 10 least severely affected children in each district, was used to evaluate the methods and a reference group (n = 179) to confirm or refute the findings in the test group. To evaluate consequences of the different methods of expressing severity of fluorosis in a subject, children from the low (n = 130) and the high fluoride (n = 132) districts not included in the test or reference group formed the community comparison groups. Comparison between the median (gold standard) and mean scores showed a significant deviation in the reference group only. Most of the partial recording methods, such as the score for the most severely affected tooth, were significantly and systematically higher than the median. While for all recording methods the median score was zero in both communities, the distribution of the subjects according to severity differed significantly between the communities.

Age as a determinant of severity of dental fluorosis in children residing in areas with 0.5 and 2.5 mg fluoride per liter in drinking water.

The purpose of this study was to investigate the influence of age on the severity of dental fluorosis in children exposed to drinking water with either low or high fluoride concentrations. The children selected for this study were aged 10-14 years, with 28 permanent teeth and at least 1 tooth pair with fluorosis. The children were permanent residents of districts in western Uganda with either 0.5 mg (n = 33) or 2.5 mg fluoride/l in drinking water (n = 186). All vestibular tooth surfaces were examined for fluorosis using the modified Thylstrup and Fejerskov (TF) index. In the high fluoride community, the proportion of teeth per child with TF scores > or = 4, and > or = 5 was significantly higher among children aged 13-14 years compared to those aged 10-12 years. Children's chronological age correlated positively and significantly with the median TF scores for all teeth, including early erupting (first molars and incisors) and late erupting teeth (canines, premolars and second molars). In linear regression analyses, the median TF score for all teeth, as well as for early erupting and late erupting teeth, increased significantly with age. On the other hand, in the low fluoride community there was no significant association between age and the severity of fluorosis. This study showed a significant increase in the severity of fluorosis with increasing age in a high fluoride community, whereas no change in severity with age was observed in a low fluoride community.

Dental variables associated with differences in severity of fluorosis within the permanent dentition.

The aim of this study was to assess the influence of age at start, duration, and completion of enamel formation, as well as of tooth-eruption age and enamel thickness on the severity of dental fluorosis within the permanent dentition. The material comprised Ugandan children (n = 219), aged 10-14 years, with 28 teeth and at least 1 tooth with fluorosis. The children were permanent residents in districts with either 0.5 mg or 2.5 mg fluoride/l in the drinking water. Fluorosis was assessed on the vestibular surfaces of all teeth using the modified Thylstrup and Fejerskov (TF) index. In order to relate fluorosis to the dental variables, the material was divided into a test group (n = 103), with fluorosis on all teeth, and a reference group (n = 116), with fluorosis on up to 27 teeth. The reference group was used to confirm or refute the findings in the test group. Paired comparisons showed significantly higher median TF scores for the late than for the early mineralizing and erupting teeth. In multiple regression analyses, the age at start, duration, and completion of enamel formation as well as tooth eruption was significantly related to the severity of fluorosis after controlling for enamel thickness (P < 0.05, n = 14). The effect (R2change) of the dental variables on the variation in severity of fluorosis within the dentition was in decreasing order: the duration of enamel formation, age at completion of enamel formation, tooth-eruption age, and the start of enamel formation.

Altitude as a risk indicator of dental fluorosis in children residing in areas with 0.5 and 2.5 mg fluoride per litre in drinking water.

The purpose of this study was to assess the association between altitude and dental fluorosis among Ugandan children in two fluoride (F) districts while controlling for other factors related to fluorosis. A random sample of 481 children aged 10-14 years was examined for fluorosis using the Thylstrup and Fejerskov (TF) index. The prevalence and severity of dental fluorosis increased significantly with increase in altitude (900 vs. 2,200 m in the low- and 1,750 vs. 2,800 m in the high-F district) and in F concentration in the drinking water. In bivariate correlation analyses, F exposure from liquid (FEL), altitude, infant formula, vegetarianism and storing of drinking water in earthenware pots were significantly associated with the tooth prevalence of fluorosis (TPF), i.e. at a severity of TF score >/=1 (p<0.05); age and gender were not. The stepwise multiple linear regression explained 35 and 55% of the variance in TPF within the low- and high-F districts, respectively. The change in R2 due to FEL was 28 and 51% points compared with 5 and 4% points due to altitude. The significant effect of FEL and altitude was confirmed by multiple logistic regression analyses. Thus, although most of the variation in the prevalence and severity of dental fluorosis was explained by the F intake from liquid, altitude was a significant risk indicator after controlling for potential confounders.