Phylogeography and host specificity of Pasteurellaceae pathogenic to sea-farmed fish in the north-east Atlantic

The present study was undertaken to address the recent spate of pasteurellosis outbreaks among sea-farmed Atlantic salmon (Salmo salar) in Norway and Scotland, coinciding with sporadic disease episodes in lumpfish (Cyclopterus lumpus) used for delousing purposes in salmon farms. Genome assemblies from 86 bacterial isolates cultured from diseased salmon or lumpfish confirmed them all as bona fide members of the Pasteurellaceae family, with phylogenetic reconstruction dividing them into two distinct branches sharing <88% average nucleotide identity. These branches therefore constitute two separate species, namely Pasteurella skyensis and the as-yet invalidly named "Pasteurella atlantica". Both species further stratify into multiple discrete genomovars (gv.) and/or lineages, each being nearly or fully exclusive to a particular host, geographic region, and/or time period. Pasteurellosis in lumpfish is, irrespective of spatiotemporal origin, linked almost exclusively to the highly conserved "P. atlantica gv. cyclopteri" (Pac). In contrast, pasteurellosis in Norwegian sea-farmed salmon, dominated since the late-1980s by "P. atlantica gv. salmonicida" (Pas), first saw three specific lineages (Pas-1, -2, and -3) causing separate, geographically restricted, and short-lived outbreaks, before a fourth (Pas-4) emerged recently and became more widely disseminated. A similar situation involving P. skyensis (Ps) has apparently been unfolding in Scottish salmon farming since the mid-1990s, where two historic (Ps-1 and -2) and one contemporary (Ps-3) lineages have been recorded. While the epidemiology underlying all these outbreaks/epizootics remains unclear, repeated detection of 16S rRNA gene amplicons very closely related to P. skyensis and "P. atlantica" from at least five cetacean species worldwide raises the question as to whether marine mammals may play a part, possibly as reservoirs. In fact, the close relationship between the studied isolates and Phocoenobacter uteri associated with harbor porpoise (Phocoena phocoena), and their relatively distant relationship with other members of the genus Pasteurella, suggests that both P. skyensis and "P. atlantica" should be moved to the genus Phocoenobacter.

A cohort study of gill infections, gill pathology and gill-related mortality in sea-farmed Atlantic salmon (Salmo salar L.): A descriptive analysis

Gill disease is an important cause of economic losses, fish mortality and reduced animal welfare in salmonid farming. We performed a prospective cohort study, following groups of Atlantic salmon in Western Norway with repeated sampling and data collection from the hatchery phase and throughout the 1st year at sea. The objective was to determine if variation in pathogen prevalence and load, and zoo- and phytoplankton levels had an impact on gill health. Further to describe the temporal development of pathogen prevalence and load, and gill pathology, and how these relate to each other. Neoparamoeba perurans appeared to be the most important cause of gill pathology. No consistent covariation and no or weak associations between the extent of gill pathology and prevalence and load of SGPV, Ca. B. cysticola and D. lepeophtherii were observed. At sea, D. lepeophtherii and Ca. B. cysticola persistently infected all fish groups. Fish groups negative for SGPV at sea transfer were infected at sea and fish groups tested negative before again testing positive. This is suggestive of horizontal transmission of infection at sea and may indicate that previous SGPV infection does not protect against reinfection. Coinfections with three or more putative gill pathogens were found in all fish groups and appear to be the norm in sea-farmed Atlantic salmon in Western Norway.

Evaluation of Immune Status in Two Cohorts of Atlantic Salmon Raised in Different Aquaculture Systems (Case Study)

Assessment of immune competence of farmed Atlantic salmon is especially important during smoltification and the first several months in the sea. Recently developed tools were applied to salmon raised in a traditional flow-through facility (FT, cohort 1) and in a recirculation aquaculture system (RAS, cohort 2). Fish were sampled at four time-points: parr, smolt, and at three weeks and three months after seawater transfer (SWT); expression of 85 selected immune and stress genes, IgM transcripts (Ig-seq), and circulating antibodies were analyzed. A steady increase in gene expression was seen over time in gill and spleen in both cohorts, and especially in antiviral and inflammatory genes in the gill. Differences between the cohorts were greatest in the dorsal fin but later leveled off. Comparison with a gill reference dataset found a deviation in only three of 85 fish, suggesting a good immune status in both cohorts. Levels of both specific and nonspecific antibodies were higher in cohort 2 in smolts and in growers three weeks after SWT; however, levels evened out after three months in the sea. Ig-seq indicated association between antibody production, expansion of the largest clonotypes, and massive migration of B cells from spleen to gill in smolts. The results suggested greater agitation and higher reactivity of the immune system in RAS-produced salmon, but the difference between the cohorts leveled off over time.

Salmon gill poxvirus disease in Atlantic salmon fry as recognized by improved immunohistochemistry also demonstrates infected cells in non-respiratory epithelial cells

Gill diseases cause serious losses in farming of Atlantic salmon and the number of agents involved increases. Salmon gill poxvirus (SGPV) and the gill disease in causes where SGPV apparently was the only disease-causing agent were initially characterized. Recently, it was further shown that SGPV can be a common denominator in widely different multifactorial gill diseases. Here, we present the challenge of diagnosing gill disease with SGPV in salmon fry of 0,3-5 grams. Apoptosis of gill lamellar epithelial cells and hemophagocytosis was also observed in fry similar to findings in smolts and grow-out fish. Using our newly developed immunohistochemistry method, we further demonstrate that some of the apoptotic epithelial cells covering the oral cavity were positive for SGPV. Thus, SGPV is not restricted to respiratory epithelium alone and may infect the fish at very early life stages. Furthermore, as the cases examined here are from Norway, Faroe Island and Scotland, we show that SGPV is more widespread than previously reported.

Measuring and Improving the Quality of Preprocedural Assessments

BACKGROUND

Preprocedural assessments are used by anesthesia providers to optimize perioperative care for patients undergoing invasive procedures. When these assessments are performed in advance by providers who are not caring for the patient during the procedure, there is an additional layer of complexity in ensuring that the workup meets the needs of the primary anesthesia care team. In this study, anesthesia providers were asked to rate the quality of preprocedural assessments prepared by other providers to evaluate anesthesia care team satisfaction.

METHODS

Quality ratings for preprocedural assessments were collected from anesthesia providers on the day of surgery using an electronic quality assurance tool from January 9, 2014 to October 21, 2014. Users could rate assessments as "exemplary," "satisfactory," or "unsatisfactory." Free text comments could be entered for any of the quality ratings chosen. A reviewer trained in clinical anesthesia categorized all comments as "positive," "constructive," or "neutral" and conducted in-depth chart reviews triggered by 67 "constructive" comments submitted during the first 3 months of data collection to further subcategorize perceived deficiencies in the preprocedural assessments. In May 2014, providers were asked to participate in a midpoint survey and provide general feedback about the preprocedural process and evaluations.

RESULTS

37,611 procedures requiring anesthesia were analyzed. Of the 17,522 (46.6%) cases with a rated preprocedural assessment, anesthesia providers rated 3828 (21.8%) as "exemplary," 13,454 (76.8%) as "satisfactory," and 240 (1.4%) as "unsatisfactory." The monthly proportion of "unsatisfactory" ratings ranged from 3.1% to 0% over the study period, whereas the midpoint survey showed that anesthesia providers estimated that the number of unsatisfactory evaluations was 11.5%. Preprocedural evaluations performed on inpatients received significantly better ratings than evaluations performed on outpatients by the preadmission testing clinic or phone program (P < .0001). The most common reason given for "unsatisfactory" ratings was a perception of "missing information" (49.2%). Chart reviews revealed that inadequate documentation was in reality the most common deficiency in preprocedural evaluations (35 of 67 reviews, 52.2%).

CONCLUSIONS

The overwhelming majority of preprocedural assessments performed at our institution were considered satisfactory or exemplary by day-of-surgery anesthesia providers. This was demonstrated by both the case-by-case ratings and midpoint survey. However, the perceived frequency of "unsatisfactory" evaluations was worse when providers were asked to reflect on the quality of preprocedural evaluations generally versus rate them individually. Analysis of comments left by providers allowed us to identify specific and actionable areas for improvement. This method can be used by other institutions to identify systemic deficiencies in the preprocedural evaluation process.

Cheyne-Stokes respiration due to chronic heart failure abates with coronary artery revascularization

A 78-year-old man presented with dyspnea and mild heart failure with Cheyne-Stokes respiration (CSR). Workup revealed inferolateral ischemia in the setting of significant triple vessel coronary disease, and nil else to adequately explain his dyspnea and eventual respiratory failure. After he underwent surgical revascularization, his ventricular function improved, leading to resolution of his respiratory failure and, of interest, his CSR. CSR is a central sleep apnea common in heart failure patients and has been associated with increased mortality. Here, we present the first English-literature report of CSR abating with surgical coronary revascularization, and briefly review the literature.

Profiles of destructive periodontal disease in different populations

In this study we evaluated the traditional view that the severity of periodontal disease varies between populations in that African and Asian populations are more severely affected than other populations. Our data on periodontal destruction in two random samples of a Kenyan and a Chinese adult population were recalculated to conform with the methods of examination and data presentation utilized in each of 6 other studies of attachment loss levels in different populations. The adult Kenyan and the adult Chinese group, who had very poor oral hygiene conditions and massive gingival inflammation, had attachment loss levels which were quite similar to those in a Japanese population (31), in a Norwegian population (27) and in a New Mexico group of adults (30). Attachment losses were similar in a population of young US adults (26) aged between 35 and 60 years relative to the corresponding Kenyan and Chinese groups while young US citizens had higher and elderly US citizens had lower mean attachment levels than either Kenyans and Chinese. Higher attachment loss levels beyond the age of 27 years were reported for a population of Sri Lankan Tamil tea workers (27) and across all ages in two South Pacific island populations (29). Overall, the analysis indicates that the periodontal attachment loss profiles may differ between populations, but that these differences do not conform with the traditional generalization that African and Asian populations suffer more severe periodontal breakdown than other populations.

Relationship between CPITN and periodontal attachment loss findings in an adult population

This study investigates the relationship between CPITN findings and the prevalence and severity of periodontal attachment loss in a rural Kenyan population comprising 1131 persons aged 15-65 years. All persons were examined for calculus, gingival bleeding, pocket depths and attachment loss levels on 4 sites of each tooth present. Recordings of bleeding, calculus and pocket depths were used to compute CPITN scores based on the 10 index teeth originally proposed, and these CPITN scores were subsequently related to the attachment loss findings derived from the full-mouth assessment. In most cases, persons with a CPITN score < or = 1 did not have attachment loss > or = 4 mm. However, among 40+ year-old persons with CPITN score 2 over 90% had attachment loss > or = 4 mm and over 50% of the 50+ year-olds with CPITN score 3 had attachment loss > or = 6 mm. Less than 20% of the 15-29 year-olds with CPITN score 3 had attachment loss > or = 6 mm, and usually the attachment loss levels ranged between 0 and 3 mm. Beyond the age of 35 years over 10% of the sextants with CPITN score 0 had attachment loss > or = 4 mm. Below the age of 35 years more than one third of all sextants with CPITN score 3 had attachment loss levels < or = 3 mm. Thus, the CPITN findings overestimate both prevalence and severity of periodontal attachment loss among the younger age groups and underestimate these parameters among elderly subject.

Caries prevalence in Africa and the People's Republic of China

Problems arise when attempting to compare caries data collected in both Africa and the People's Republic of China. These difficulties are not only the result of differences in the criteria used for the diagnosis of caries but are also due to the diversity of cultural and social conditions existing within each of the geographical areas. However, interpreted with caution, the data seem to suggest that caries experience among children is still fairly stable and at a low level, in contrast to the predictions of a decade ago. When comparing data from adult and elderly cohorts, however, caries is seen to be a widespread disease with continuing slow progression throughout life.

Validity of CPITN's assumptions of hierarchical occurrence of periodontal conditions in a Kenyan population aged 15-65 years

In order to study the validity of the hierarchical principle of the CPITN we used data originating in a cross-sectional study of periodontal disease in a random sample comprising 1131 Kenyans aged 15-65 yr to determine, for each tooth present in each individual, the absence or presence of gingival bleeding, of dental calculus, of a pocket of 4-5 mm or a pocket of 6+ mm, such that each tooth had a separate recording for bleeding, calculus, pocket 4-5 mm and pocket 6+ mm. According to the hierarchical principle of CPITN a tooth with pockets as the most severe finding is assumed positive also for calculus and bleeding, and a tooth with calculus as the most severe finding is assumed positive also for bleeding. Our analysis showed that calculus as the most severe finding of a tooth overestimates the occurrence of bleeding by up to 18%, depending on age of the individuals and the set of teeth examined. Pockets as the most severe finding in a tooth overestimates the occurrence of bleeding by up to 13%, and overestimates calculus by up to 54%, most pronounced in the younger age groups. The effect of these overestimations on prevalence and severity estimates was the most pronounced for the severity measures, particularly regarding the severity of bleeding, whereas prevalence estimates remained relatively unaffected. Undoubtedly, this result should be seen in the light of a very high prevalence and severity of both bleeding and calculus in this population.

Influence of CPITN partial recordings on estimates of prevalence and severity of various periodontal conditions in adults

This study compares the results of a full mouth examination with the results of examining only the CPITN selection of 10 index teeth 17/16, 11, 26/27, 47/46, 31 and 36/37 for estimates of prevalence and severity of the conditions assessed with the CPITN, i.e. gingival bleeding, dental calculus, pockets 4-5 mm deep and pockets 6+ mm deep. The mean number of sextants recorded with bleeding or with calculus was generally overestimated when examinations were based on the CPITN selection of index teeth, whereas the mean number of sextants with pockets, whether moderate or deep, were generally underestimated. Similarly, the prevalence of pockets, whether moderate or deep, was underestimated in virtually all age groups while the prevalence of calculus was overestimated in all age groups and the prevalence of bleeding was overestimated among persons below 30 yr of age. We conclude that the partial recording approach of the CPITN methodology is reasonably well suited for identifying persons who are relatively healthy according to the hierarchy of the CPITN parameters. There is, however, a considerable risk that persons presenting with the more severe conditions, i.e. pockets, will be overlooked if only partial recordings are performed.

Impact of user fees on attendance at a referral centre for sexually transmitted diseases in Kenya

We investigated the impact of a short-lived policy of charging fees to patients attending public-sector outpatient health facilities in Kenya by collecting data on attendance at Nairobi's Special Treatment Clinic for sexually transmitted diseases (STDs) before (23 months), during (9 months), and after (15 months) the user-charge period. During the user-charge period, the seasonally adjusted total mean monthly attendance of men decreased significantly to 40% (95% CI 36-45) of that before fees were levied. Attendance rose in the post-user-charge period, but reached only 64% (59-68) of the pre-user-charge level. For women, the adjusted total mean monthly attendance during the user-charge period was reduced significantly to 65% (55-77) of the pre-user-charge level. Mean monthly attendance by women rose in the post-user-charge period to 22% (9-37) above the pre-user-charge level. There was no evidence of an increase in attendance over the course of the user-charge period among either men or women. The introduction of user fees probably increased the number of untreated STDs in the population, with potentially serious long-term health implications. The user-fee experience in Kenya should be carefully evaluated before similar measures are introduced elsewhere.

Inhibition of peptidase and glycosidase activities of Porphyromonas gingivalis, Bacteroides intermedius and Treponema denticola by plant extracts

Aqueous extracts from 5 plants used widely in Kenya as chewing sticks (mswaki) for the control of oral hygiene were tested for their ability to inhibit extracellular peptidase and glycosidase enzyme activities produced by the periodontopathic bacteria Porphyromonas gingivalis (formerly Bacteroides gingivalis), Bacteroides intermedius and Treponema denticola. The plants studied were Rhus natalensis, Cupressus hisitanica, Sida cordifolia, Olea africana and Euclea divinorum. Protease activities, including glycylprolyl dipeptidase and trypsin-like activities of P. gingivalis, chymotrypsin-like and glycylprolyl dipeptidase activities of B. intermedius and the trypsin-like activity of T. denticola, were particularly affected by extracts from Rhus natalensis and Euclea divinorum. Glycosidase activities were generally less affected with the notable exceptions of the inhibition of beta-mannosidase activity of P. gingivalis by all extracts and the inhibition of neuraminidase activity of T. denticola by Rhus natalensis and Euclea divinorum. Generally, these same proteolytic and glycosidic activities were inhibited by tannic acid and to lesser extents by gallic acid and gallic acid methyl ester. An inhibitory component, present in all extracts, exhibited physical and chemical properties identical to those of tannic acid. The inhibition of these enzyme activities is likely to reduce the virulence of these periodontophathic bacteria and to reduce the rate of dental plaque formation.

Putative periodontopathogens in “diseased” and “non-diseased” persons exhibiting poor oral hygiene

The aim of the study was to assess the occurrence of some putative periodonto-pathogens in "test" and "control" sites in "diseased" and "non-diseased" persons, respectively, from an adult rural Kenyan population exhibiting poor oral hygiene and widespread loss of attachment (LA). 14 persons (less than 35 years) were assigned to a "diseased" category on the basis of at least 4 sites with LA greater than or equal to 4 mm; at least 5 mm LA and a pocket greater than or equal to 4 mm interproximally in a lower incisor ("test" site): and less than 2 mm LA and no pocket greater than or equal to 4 mm distal to a lower canine or mesial to a lower first premolar ("control" site). Age-matched "non-diseased" persons were identified on the basis of no sites with LA greater than 2 mm and no pockets greater than or equal to 4 mm associated with LA. Paperpoint samples from test and control sites as well as a scraping sample from the dorsum of tongue were examined for presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Bacteroides intermedius, B. melaninogenicus group, Capnocytophaga, Selenomonas spp., and Wolinella recta. P. gingivalis was found in 79% of test sites and 36% of control sites in "diseased" persons, and in 18% and 35% of test and control sites, respectively, in "non-diseased" persons. "No other bacterial group discriminated significantly between test and control sites or between diseased and non-diseased subjects. The surprisingly high occurrence of P. gingivalis in non-diseased subjects, both subgingivally and on tongue, indicates that deep periodontal pockets are not prerequisite ecological environments for P. gingivalis establishment.

The effect of sucrose on plaque pH in the primary and permanent dentition of caries-inactive and -active Kenyan children

The hypothesis that the Stephan pH responses of dental plaque would be different in caries-active and -inactive individuals was tested in 20 seven-year-old and 19 14-year-old Kenyan children. In each age group, half the children had greater than or equal to 2 dentin cavities; the other half had no such lesions. With a palladium-touch microelectrode, interdental plaque pH was monitored between m1/m2 in each quadrant in the primary dentition and in the four molar/premolar regions in the permanent dentition. pH was also monitored in caries cavities in the occlusal surfaces of lower first molars and on the tongue. pH was measured before and up to 60 min after the children rinsed with 10 mL of 10% sucrose. Caries status of the individual was unrelated to plaque pH in comparable non-carious sites in both of the age groups. The pH minimum in the maxilla was about 0.5 pH units lower than that in the mandible. Active occlusal caries lesions had a resting pH value of about 5.5, about 1 pH unit lower than that of sound surfaces. The pH dropped to about 4.5 in caries lesions and recovered slowly. In sound occlusal sites, a pH drop to about 6.0 was followed by a relatively rapid return to the resting value. Thus, when the mean values were considered, the classic Stephan curve response was evident. However, when the pH changes at single sites were considered at various time intervals, a substantial, erratic fluctuation was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of palladium touch microelectrodes under field conditions for in vivo assessment of dental plaque pH in children

The aim of this study was to assess the applicability of palladium touch microelectrodes, connected to battery-run pH meters, for in vivo plaque pH measurements in children. The pH was assessed in 20 7-year-old and in 19 14-year-old caries-active and caries-inactive rural Kenyan children. The resting pH was measured at non-carious interproximal and occlusal sites and in open dentine cavities. Independent repeated measurements were performed at given sites at intervals of 15 s and 5 min and on different days. The resting plaque pH varied widely among the children, and there was no significant difference between caries-active and caries-inactive groups. The most striking feature was the considerable erratic fluctuations of pH at a given site with time, both in resting and in sucrose-challenged plaque. These fluctuations were sensitively recorded by palladium touch microelectrodes. After a sucrose rinse, not all sites in the same mouth behaved in a similar fashion, and thus the classical 'Stephan curve' was not always apparent. In conclusion, the palladium touch microelectrodes are highly applicable for plaque pH measurements in children, even under extreme field conditions.

Effect of sugarcane chewing on plaque pH in rural Kenyan children

In 5 rural Kenyan children, the effect of sugarcane chewing on plaque pH was compared with the effect of a mouthrinse with 10% sucrose at various intraoral sites. They all had poor oral hygiene and at least two carious cavities in occlusal surfaces of molars. pH measurements were conducted under field conditions using paladium touch microelectrodes connected to a battery-operated pH meter. There was a marked difference in pH response of non-carious approximal sites between maxilla and mandible, with the lowest values in the maxilla. However, the pH recovery following the instantaneous drop occurred in parallel even if most pH values had not returned to baseline values 30 min after the sucrose rinse. Following the sugarcane chewing, the pH fall was less pronounced on all sites, and within 5-10 min the values had returned to resting pH and even exceeded this. In carious cavities, a similar pattern was observed, although the acidity in these sites was more pronounced, also reflected in a lower resting mean pH. The main conclusion from this study is that sugarcane chewing yields a less pronounced pH drop and a quicker pH recovery in dental plaque than is seen following a mouthrinse with 10% sucrose. This difference probably results from stimulation of salivary flow associated with the chewing.

A random effects model for some epidemiological features of dental caries

We describe a random effects model for caries lesion development and progression based on considering the effects of the pH fluctuations over time in microbial dental plaque as a Wiener process with a single absorptive barrier. The model predicts that the period of greatest risk to developing caries occurs shortly after eruption, but thereafter the longer a surface survives without developing a lesion, the less likely will it be that a lesion will subsequently develop. The model is able to anticipate why the effect of water fluoridation on caries prevalence is most pronounced when caries is diagnosed at cavity level. This model offers one way in which the variability which characterizes the complex ecosystem associated with dental caries may be considered a subject of interest for enhancing our understanding of its pathogenesis and epidemiology.

Changes in dental caries experience of 12-year olds in low fluoride urban and rural areas of Tanzania

This report is a 2-year follow-up of a baseline study conducted in Tanzania in 1984. 377 and 448 twelve-year old primary school children were examined in Dar es Salaam (urban) and rural areas respectively. The same criteria and examiners were employed to replicate conditions in 1984 as closely as possible. The mean DMFT score has remained stable over the 2-year period in both the urban (1984: 0.67 (s.d. 1.20); 1986: 0.64 (s.d. 1.32) and rural (1984: 0.51 (s.d. 1.07); 1986: 0.40 (s.d 0.93) areas. However, a significant decrease in the mean DMFS score in Dar es Salaam from 1.19 (s.d. 2.71) in 1984 to 0.81 (s.d. 1.96) in 1986, and in rural areas from 0.78 (s.d. 1.98) in 1984 to 0.48 (s.d. 1.44) in 1986 was observed. In 1986 significantly fewer children with caries had more than 5 involved surfaces in both urban and rural areas than in 1984. In the two areas the difference in caries prevalence observed between 1984 and 1986 affected different surfaces types to varying extents. The results do not support the finding that caries is increasing in all developing countries.

From development to sustained crisis: structural adjustment, equity and health

We argue that the nature of the economic crises in sub-Saharan Africa cannot be understood outside the context of the legacy of colonialism and class formation. Structural adjustment programmes serve to exacerbate inequalities and threaten to reverse the social gains of the majority achieved through the struggle for independence, in the interest of the indigenous capitalist class. Under such circumstances social scientists have a social responsibility to take a stand against the current policies that have led to an unprecedented decline of the health status of the poor; their skills must be put at the disposal of the oppressed with a view to giving voice to the experiences and needs of the majority.

Transition dynamics of HIV disease in a cohort of African prostitutes: a Markov model approach

The progression of HIV-related disease from infection to death is represented as a staged Markov model. Transitions between stages are considered reversible. The model is fitted to data from a cohort of African prostitutes by means of maximum likelihood. It appears that the progression to symptomatic disease (Centers for Disease Control stage IV) in this population is considerably more rapid than that reported from studies in Western countries.

A new approach to investigating associations in periodontal disease data

This paper presents a method for the analysis of data originating from studies of destructive periodontal disease. The proposed method is an extension of the Mantel-Haenszel technique for the analysis of case-control studies and allows for expression of the site-specificity of destructive periodontal disease while maintaining the individual as the unit of analysis. Using data originating from a cross-sectional study of periodontal breakdown and oral hygiene parameters in a random sample of adult rural Kenyans, the proposed method is illustrated and the results compared with results obtained when two alternative analytical methods are used. The results demonstrate that the choice of analytical strategy may have profound implications for the conclusions to be drawn. Depending on the strategy chosen, one may draw conclusions which are qualitatively different and the present study indicates that the direction of these differences is not predictable.

Fluoride binding capacity of bone charcoal and its effects on selected micro-organisms

Water is a major source of fluoride ions in areas where skeletal and dental fluorosis are endemic. We investigated the capacity of bone char to remove fluoride from water and its effects on selected bio-indicator organisms. Under static and dynamic conditions, the capacity of bone char was in the order of 2.5 mg of fluoride per g of bone char. Bone charcoal did not appear to support growth of yeast and S. aureus. E. coli and S. faecalis counts in the filtrate decreased with time but there was substantive growth in the bone charcoal.

Effect of cigarette smoking on the transition dynamics in experimental gingivitis

This paper reports the findings of an experimental gingivitis study conducted in smokers and non-smokers. 33 volunteers were examined and underwent prophylaxis during a period of 4 weeks. 28 subjects who showed a plaque index less than 0.20 on all prophylaxis occasions were permitted to continue in the study. Subjects then had their gingival status recorded, had their teeth polished and were requested to abstain from all oral hygiene measures for the following 21 days. After 5 days, 10 days and 21 days, plaque and gingival status were recorded using the criteria of the plaque index and gingival index. After the examination on day 21, the teeth were polished and oral hygiene was re-instituted. Following 2 weeks of supervised oral hygiene, recordings of plaque and gingival status were performed. At the initial examination, there was no difference between the clinical assessment of plaque and gingival status in smokers and non-smokers. Similar amounts of plaque accumulated in the 2 groups during the period of no oral hygiene, but smokers exhibited less gingival inflammation assessed clinically than non-smokers. This difference occurred as a result of an apparently lowered incidence rate and a markedly higher recovery rate in smokers compared to non-smokers. These findings may indicate that smokers for reasons yet unknown have a reduced capacity to mount and maintain an effective defense reaction to a given plaque challenge.

Dental caries in developing countries in relation to the appropriate use of fluoride

Although it is widely believed that caries prevalence in developing countries is increasing rapidly, a review of studies from Africa and China provides equivocal evidence. Data from child and adult populations indicate that the disease is almost ubiquitous but with a slow rate of progression. Theoretically, administration of fluoride in such populations should result in reducing caries progression rates, but too little is known about the magnitude of the effect, and therefore about the cost-effectiveness of different methods of fluoride administration. The lack of a developed infrastructure and of trained personnel in many developing countries limits the applicability of many strategies. Methods of fluoride administration that minimize systemic exposure are to be recommended where affordable or practical. In the light of economic constraints and slow caries lesion progression rates, however, improvements in oral hygiene practices may be the most important method of controlling the disease whether or not fluoride is available or accessible.

The nature and mechanisms of dental fluorosis in man

Any use of fluorides, whether systemic or topical, in caries prevention and treatment in children results in ingestion and absorption of fluoride into the blood circulation. The mineralization of teeth under formation may be affected so that dental fluorosis may occur. Dental fluorosis reflects an increasing porosity of the surface and subsurface enamel, causing the enamel to appear opaque. The clinical features represent a continuum of changes ranging from fine white opaque lines running across the tooth on all parts of the enamel to entirely chalky white teeth. In the latter cases, the enamel may be so porous (or hypomineralized) that the outer enamel breaks apart posteruptively and the exposed porous subsurface enamel becomes discolored. These changes can be classified clinically by the TF index to reflect, in an ordinal scale, the histopathological changes associated with dental fluorosis. Compared with Dean's and the TSIF index, we consider the TF index to be more precise. Recent studies on human enamel representing the entire spectrum of dental fluorosis have demonstrated a clear association between increasing TF score and increasing fluoride content of the enamel. So far, no useful data on dose (expressed in mg fluoride/kg b.w.)-response (dental fluorosis) relationships are available. In this paper, we have, therefore, re-evaluated the original data by Dean et al. (1941, 1942), Richards et al. (1967), and Butler et al. (1985) from the USA, by applying the equation of Galagan and Vermillion (1957) which permits the calculation of water intake as a function of temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of protease activities of periodontopathic bacteria by extracts of plants used in Kenya as chewing sticks (mswaki)

Extracts from five plants used as chewing sticks, and tannic acid, gallic acid and methyl ester of gallic acid, were tested for their ability to inhibit proteolytic activities of three strains of Bacteroides gingivalis, three strains of Bacteroides intermedius and two strains of Treponema denticola. Aqueous extract from the plants Rhus natalensis and Euclea divinorum were the most inhibitory of those tested, inhibiting by 50% the proteolytic activity of the test organisms, at concentrations of up to 200 micrograms/ml. Tannic and gallic acids had similar effects at concentrations of less than 10 micrograms/ml, while the methyl ester of gallic acid was less inhibitory. These findings suggest that extracts from plants used as chewing sticks may possess enough inhibitory components to interfere with the virulence and growth of periodontopathic bacteria in vivo, provided they are able to gain access to the subgingival sites such bacteria preferentially inhabit.

Low prevalence of oral mucosal lesions in HIV-1 seropositive African women

In Nairobi (Kenya) 334 women prostitutes of whom 80.5% were HIV-1 positive, were examined for oral mucosal lesions; 15.6% of seropositive, and 4.6% of seronegative, women had oral mucosal lesions, predominantly oral candidiasis. In the seropositives, 8.6% had erythematous, 1.1% had hyperplastic candidiasis, and 0.4% had hairly leukoplakia as the only oral lesions; 0.4% had a combination of erythematous and hyperplastic candidiasis, and 1.5% had combinations of pseudomembranous and erythematous candidiasis in the presence of hairly leukoplakia. Of the 211 seropositive women for whom we knew the first date on which a positive serologic test was obtained, the likelihood of developing an oral mucosal lesion was found to be dependent on the duration of seropositivity. The low incidence of oral mucosal lesions in this population may be due to the relatively recent acquisition of HIV-1 infection.

Associations between salivary levels of Streptococcus mutans, Streptococcus sobrinus, lactobacilli, and caries experience in Kenyan adolescents

Salivary levels of mutans streptococci (S. mutans and S. sobrinus) and lactobacilli were determined in a random sample of rural Kenyans between 15 and 19 years of age (n = 149). It is possible for the natural history of dental caries in this population to be studied since it is characterized by a limited access to conventional dental treatment. Using a short set of biochemical tests, we identified from seven to ten presumptive mutans streptococcus colonies--cultured from the saliva of each individual--to differentiate between S. mutans and S. sobrinus. No colonies resembling S. rattus (S. mutans serotype b) were isolated. Lactobacilli were identified as Gram-positive, catalase-negative rods. The mean D1-4MFS and D3-4MFS were 7.03 +/- 6.43 and 1.46 +/- 3.44, respectively. The mean mutans streptococcus and lactobacillus levels were 8.7 x 10(4) and 6.7 x 10(4), respectively. The salivary mutans streptococcus and lactobacillus levels were significantly correlated (p less than 0.01). Of the subjects, 64% harbored only S. mutans, 4% only S. sobrinus, 30% both species, and 2% neither. Lactobacilli were ubiquitous. The caries experience of the group was significantly (p less than 0.001) correlated with both the total salivary level of mutans streptococci and the salivary S. mutans levels, but not with the salivary S. sobrinus level.

Transition dynamics in experimental gingivitis in humans

This study was conducted in order to investigate the dynamics of the gingival inflammatory status during periods of plaque accumulation and thorough oral hygiene. After a period of prophylaxis, 42 volunteers were asked to abstain from all oral hygiene measures for 2 weeks, whereafter oral hygiene was reinstituted. In the absence of oral hygiene, plaque was found at virtually all sites after 7 days and the number of sites with gingivitis increased simultaneously. A reduction in gingival inflammation occurred subsequent to plaque removal. During phases of both plaque accumulation and thorough oral hygiene, sites were found to convert from non-inflamed to inflamed status concurrently, as in the reverse direction. No association between plaque and gingivitis was revealed. The gingival status of a single site was a poor predictor of its status on the subsequent occasion. The proportion of inflamed sites converting to non-inflamed status was greater than the proportion of non-inflamed sites converting to inflamed status at any time. The estimated incidence rate remained fairly constant during both the plaque accumulation phase and the oral hygiene phase, whereas the estimated recovery rate was considerable lower during the plaque accumulation phase compared to oral hygiene phase. The clinical appearance is the outcome of the dynamics between these rates. The steady-state prevalences derived from the estimated "incidence" and "recovery" rates were quite similar to the actual findings after 14 d of plaque accumulation and the subsequent 10 d of thorough oral hygiene.

A stochastic model for periodontal breakdown

This paper considers a possible explanation for the occurrence of periodontal breakdown in bursts and remissions. We show that such bursts and remissions, apart from being the result of major biological events, can also be generated by a stationary process of Brownian motion.

Fluctuation of fluoride concentrations in drinking waters: a collaborative study

The aim of this study was to describe the variations with time in the concentrations of fluoride in drinking water sources in Greenland, Kenya, Greece, Denmark and Ireland. Water samples were collected monthly and shipped to laboratories in Aarhus for electrometric analyses. In Narssaq, Greenland the fluoride concentration of a single piped water supply ranged from 0.3 to 2.8 ppm, the variations being related to climate, precipitation and temperature over the year. Water from the Athi River, Kenya had a fluoride content ranging from 0.3 to 1.2 ppm, the higher concentrations being associated with the dry seasons. The fluoride concentration in piped water from mountain rivers in Mourjes, Greece, ranged over the year between 1.3 to 2.0 ppm, the changes being apparently unrelated to rainfall. Marked variations in fluoride concentrations from 0.5 to over 3.5 ppm were observed in water from artesian wells in Assiros, Greece. In drinking waters from boreholes in Boennerup Strand, Denmark, fluoride concentrations ranged with time from 1.4 to 2.4 ppm, the variations being unrelated to climate or precipitation, while little variation in fluoride concentrations was found in water from boreholes in either Roedvig or Egens, Denmark. Water obtained from two sources of artificially fluoridated water supplies from Ireland showed considerable variations with time, although pooled samples indicated relatively constant levels over the year. The study indicates that the results of single fluoride ion measurement from any given source should not be taken as being a reliable indicator of fluoride exposure from drinking water.(ABSTRACT TRUNCATED AT 250 WORDS)

Black-pigmented Bacteroides species and Actinobacillus actinomycetemcomitans in subgingival plaque of adult Kenyans

A microbiological study was performed of the subgingival plaque on 2 sites in each of 20 adults originating from a rural area 40 km outside Nairobi, Kenya. The recovery rate of B. gingivalis was 70%, of B. intermedius 100% and of A. actinomycetemcomitans 40% of the subjects, and 50%, 90% and 28%, respectively, of the sites. The isolated strains exhibited similar biochemical characteristics and antibiotic susceptibility pattern as type strains of these species. The high recovery rate of these 3 bacterial species in adult Kenyans was a rather surprising finding, since pathological pocketing was found only sporadically. Furthermore, the results of 2 methodological approaches tested demonstrated that such microbiological studies can be carried out in countries with limited laboratory facilities.

Chewing sticks, toothpaste, and plaque removal

The aim of the present study was to assess the efficacy of brushing with chewing sticks in removing plaque and to evaluate whether toothpaste has any additional effect on the removal of established dental plaque. Kenyan schoolchildren had their plaque deposits disclosed by means of disclosing tablets and subsequently recorded on four buccal sites of all permanent teeth. The children were then allocated to two groups in a crossover design; in one group the children brushed with chewing sticks and toothpaste; the other group brushed with chewing sticks only. Substantial amounts of plaque were recorded at base line in most children. Brushing with a chewing stick for 5 min resulted in a net reduction of the proportion of plaque deposit sites per child. Toothpaste resulted in no additional effect.

Dental caries in 12-year-old urban and rural children in Zimbabwe

608 12-yr-old children in Harare, and 556 in rural areas of Mashonaland and Central Province, Zimbabwe, were examined for dental caries in 1985. 27.6% of children in the urban area, and 20.9% in the rural, had caries (P less than 0.01). The mean DMFT in urban and rural areas was 0.57 (+/- 1.13) and 0.49 (+/- 1.42), respectively (P = 0.29). Girls had higher levels of caries than boys. Most of the caries occurred on occlusal surfaces, and first molars were the most affected of all teeth. Caries experience was similar to that reported 10 yr previously in Zimbabwe, and similar to that found recently in 12-yr-olds in Kenya and Tanzania. The authors question whether in fact developing countries having high or increasing levels of caries in 12-yr-olds constitute the exception or the rule with regard to trends in dental caries prevalence.

Pattern of dental caries in an adult rural population

A study was conducted amongst 1,131 randomly selected persons aged 15-65 years in a rural area of Kenya, having minimal access to dental care. A relatively low prevalence of frank cavitation was found in the 15- to 24-year-old cohort, but in the older age groups over 80% were so affected. Caries in the youngest cohort was characterized by a predominance of enamel lesions. At the age of 25-34 years, however, involvement of pulpal tissues and loss of teeth due to caries was more common, and this age group exhibited the largest number of dentinal lesions. The 35- to 44-year-old cohort exhibited fewer enamel and dentinal lesions, but more pulpally involved lesions and more extracted teeth. In the group aged 45-54 years, enamel and dentinal lesions were less common, and at the age of 55-65 years, such lesions were less common in comparison to their occurrence in younger cohorts. The 55- to 65-year cohort could generally be characterized as having larger numbers of root surface lesions, lesions involving the pulp, and extracted teeth. Root surface lesions were principally associated with age over 35 years. In all age groups caries exhibited a skewed distribution, most of the lesions occurring in a minority of individuals. This study demonstrates that caries activity continues throughout life and is not a phenomenon confined to any one period of life.

Caries experience in urban Tanzanian children 1973-84

In 1973 and 1984 the caries status of 624 and 394 children, respectively, was recorded in an urban area of northern Tanzania where the water fluoride content was 2.0-3.5 ppm. Although slightly different scoring criteria were used, the data showed very low levels of caries, and little evidence of increases in caries experience over the 10-yr period. The distribution of caries lesions was markedly skewed, such that a minority of individuals account for most of the caries. The levels of caries were low by international standards and equivalent to those found in children from low fluoride areas of Tanzania.

Periodontal diseases in adult Kenyans

This study comprised 1131 persons who constitute a stratified random sample of the entire population aged 15-65 years in Machakos District, Kenya. Each person was examined for tooth mobility, plaque, calculus, gingival bleeding, loss of attachment and pocket depth on the mesial, buccal, distal and lingual surface of each tooth. The oral hygiene was poor with plaque on 75-95% and calculus on 10-85% of the surfaces depending on age. Irrespective of age, pockets greater than or equal to 4 mm was seen on less than 20% of the surfaces, whereas 10-85% of the surfaces had loss of attachment greater than or equal to 1 mm. The proportion of surfaces per individual with loss of attachment greater than or equal to 4 mm or greater than or equal to 7 mm, and pocket depths greater than or equal to 4 mm or greater than or equal to 7 mm, respectively, showed a pronounced skewed distribution, indicating that in each age group, a subfraction of individuals is responsible for a substantial proportion of the total periodontal breakdown. The individual teeth within the dentition also showed a marked variation in the severity of periodontal breakdown. Our findings provide additional evidence that destructive periodontal disease should not be perceived as an inevitable consequence of gingivitis which ultimately leads to considerable tooth loss. A more specific characterization of the features of periodontal breakdown in those individuals who seem particularly susceptible is therefore warranted.

Tooth mortality in an adult rural population in Kenya

This paper reports on the pattern of tooth loss in a random sample of 1131 adults aged from 15 to 65 years in a rural area of Kenya in which access to formal dental care is minimal. We found that the majority of the population retained most of their dentition in a functional state even up to the age of 65 years: In all age groups, more than 50% had at least 26 teeth present, and more than 90% had at least 16 teeth present. The prevalence of edentulousness was less than 0.3%. The principal cause of tooth loss in all age groups was caries, and this was true for all tooth-types except incisors, for which periodontal disease was the main cause of tooth loss. The cultural practice of removing lower central incisors was observed only in those over 40 years of age. More teeth were lost due to caries among women than among men, while the reverse was true for teeth lost due to periodontal diseases. In view of the fact that most people retain most of their teeth throughout life, it is suggested that the most appropriate strategies for dental health care in this population should be those promoting self care, rather than the introduction of a formal treatment-oriented approach provided by dentists.