Haemophili and related bacteria in the human oral cavity

Essential genes for Haemophilus parainfluenzae survival and biofilm growth

Haemophilus parainfluenzae ( Hp ) is a Gram-negative, pleomorphic rod, highly prevalent and abundant as a commensal in the human oral cavity, and an infrequent extraoral opportunistic pathogen. Hp occupies multiple niches in the oral cavity, including the tongue dorsum, keratinized gingiva, and the supragingival plaque biofilm. As a member of the HACEK group, Hp is also known to cause infective endocarditis. Additionally, case reports have identified Hp as the causative agent of meningitis, septic arthritis, chronic osteomyelitis, septicemia, and a variety of other infectious diseases. Little is known about how Hp interacts with its neighbors in the healthy biofilm nor about its mechanisms of pathogenesis as an extraoral opportunistic pathogen. To address these unknowns, we identified the essential genomes of two Hp strains and the conditionally essential genes for their growth in in vitro biofilms aerobically and anaerobically. Using transposon insertion sequencing (TnSeq) with a highly saturated mariner transposon library in two strains, the ATCC33392 type-strain ( Hp 392) and a commensal oral isolate EL1 ( Hp EL1), we show that the essential genome of Hp 392 and Hp EL1 is composed of 395 and 384 genes, respectively. The core essential genome, consisting of 341 essential genes conserved between both strains, was composed of genes associated with genetic information processing, carbohydrate, protein, and energy metabolism. We also identified conditionally essential genes for aerobic and anaerobic biofilm growth, which were associated with carbohydrate and energy metabolism in both strains of Hp . Additionally, RNAseq analysis determined that most genes upregulated during anaerobic growth are not essential for Hp 392 anaerobic biofilm survival. The completion of this library and analysis under these conditions gives us a foundational insight into the basic biology of H. parainfluenzae in differing oxygen conditions, similar to its in vivo oral habitat. Further, the creation of this library presents a valuable tool for further investigation into conditionally essential genes for an organism that lives in close contact with many microbial species in the human oral habitat.

Whole-genome sequence of Haemophilus parainfluenzae EL1 isolated from healthy supragingival plaque

Haemophilus parainfluenzae is a Gram-negative bacterium that colonizes the mouth and the upper respiratory tract. Here, we report the genome sequence of H. parainfluenzae strain EL1 isolated from healthy supragingival plaque. This strain is used as a representative commensal of the oral microbiota.

The human oral phageome

Oral bacteriophages (or phages), especially periodontal ones, constitute a growing area of interest, but research on oral phages is still in its infancy. Phages are bacterial viruses that may persist as intracellular parasitic deoxyribonucleic acid (DNA) or use bacterial metabolism to replicate and cause bacterial lysis. The microbiomes of saliva, oral mucosa, and dental plaque contain active phage virions, bacterial lysogens (ie, carrying dormant prophages), and bacterial strains containing short fragments of phage DNA. In excess of 2000 oral phages have been confirmed or predicted to infect species of the phyla Actinobacteria (>300 phages), Bacteroidetes (>300 phages), Firmicutes (>1000 phages), Fusobacteria (>200 phages), and Proteobacteria (>700 phages) and three additional phyla (few phages only). This article assesses the current knowledge of the diversity of the oral phage population and the mechanisms by which phages may impact the ecology of oral biofilms. The potential use of phage-based therapy to control major periodontal pathogens is also discussed.

Diversity patterns of bacteriophages infecting Aggregatibacter and Haemophilus species across clades and niches

Aggregatibacter and Haemophilus species are relevant human commensals and opportunistic pathogens. Consequently, their bacteriophages may have significant impact on human microbial ecology and pathologies. Our aim was to reveal the prevalence and diversity of bacteriophages infecting Aggregatibacter and Haemophilus species that colonize the human body. Genome mining with comparative genomics, screening of clinical isolates, and profiling of metagenomes allowed characterization of 346 phages grouped in 52 clusters and 18 superclusters. Less than 10% of the identified phage clusters were represented by previously characterized phages. Prophage diversity patterns varied significantly for different phage types, host clades, and environmental niches. A more diverse phage community lysogenizes Haemophilus influenzae and Haemophilus parainfluenzae strains than Aggregatibacter actinomycetemcomitans and “Haemophilus ducreyi”. Co-infections occurred more often in “H. ducreyi”. Phages from Aggregatibacter actinomycetemcomitans preferably lysogenized strains of specific serotype. Prophage patterns shared by subspecies clades of different bacterial species suggest similar ecoevolutionary drivers. Changes in frequencies of DNA uptake signal sequences and guanine–cytosine content reflect phage-host long-term coevolution. Aggregatibacter and Haemophilus phages were prevalent at multiple oral sites. Together, these findings should help exploring the ecoevolutionary forces shaping virus-host interactions in the human microbiome. Putative lytic phages, especially phiKZ-like, may provide new therapeutic options.

Plaque pH in caries-free and caries-active young individuals before and after frequent rinses with sucrose and urea solution

OBJECTIVE

To examine pH in the approximal dental biofilm after acid and alkali formation from sucrose and urea, after an adaptation period to these substances, in caries-free (CF) and caries-active (CA) individuals. Saliva flow and buffer capacity, and aciduric bacteria in saliva and plaque were also examined.

MATERIAL AND METHODS

Twenty adolescents and young adults (15-21 years) with no caries (n = 10, D(m + i)MFS = 0) or ≥1 new manifest lesions/year (n = 10, DmMFS = 3.4 ± 1.8) participated. After plaque sampling, interproximal plaque pH was measured using the strip method before (baseline) and up to 30 min (final pH) after random distribution of a 1-min rinse with 10 ml of 10% sucrose or 0.25% urea. This procedure was repeated after a 1-week adaptation period of rinsing 5 times/day with 10 ml of the selected solution. After a 2-week washout period the second solution was similarly tested. Mutans streptococci, lactobacilli and pH 5.2-tolerant bacteria were analyzed by culturing.

RESULTS

In the CF group, acid adaptation resulted in lowering of baseline and final plaque pH values after a sugar challenge, and in increased numbers of bacteria growing at pH 5.2, which was increased also after alkali adaptation. In the CA group, the final pH was decreased after acid adaptation. No clear effects of alkali adaptation were seen in this group.

CONCLUSION

One-week daily rinses with sucrose and urea had the most pronounced effect on the CF group, resulting in increased plaque acidogenicity from the sugar rinses and increased number of acid-tolerant plaque bacteria from both rinses.

Identification of haemolytic Haemophilus species isolated from human clinical specimens and description of Haemophilus sputorum sp. nov

Haemolytic Haemophilus strains with no requirement for X factor are regularly isolated from sputum and throat swabs and occasionally from invasive infections, but the classification of such strains is not clear. We characterized 56 strains with a phenotype concordant with Haemophilus parahaemolyticus (V, but not X factor-dependent; urease-positive; tryptophanase-negative; ornithine decarboxylase-negative) by extended phenotypic testing and 16S rRNA gene sequencing. In addition, 31 of the strains and representative type strains were investigated by multilocus sequence analysis based on 3 housekeeping gene fragments. Most strains could be assigned to H. parahaemolyticus and were characterized by expression of IgA1 protease and a negative test for β-galactosidase. Isolation of H. parahaemolyticus from various infections and its absence among more than 300 commensal Haemophilus isolates suggests a pathogenic potential of this organism. The majority of haemolytic strains with β-galactosidase activity did not cluster with the type strain of H. paraphrohaemolyticus, but constituted a distinct and coherent novel taxon. Ten strains of this new taxon proved to be genetically and phenotypically homogeneous. Few biochemical characters discriminate the new taxon from related Haemophilus species, but identification is easily accomplished by routine matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Genetic, biochemical, and spectrometry data show that the taxon merits recognition as a novel species of Haemophilus. The name Haemophilus sputorum is proposed, with CCUG 13788(T) (=DSM 24472(T)=NCTC 13537(T)) as the type strain.

Opportunistic respiratory pathogens in the oral cavity of the elderly

The oral cavity of the hospitalized or bedridden elderly is often a reservoir for opportunistic pathogens associated with respiratory diseases. Commensal flora and the host interact in a balanced fashion and oral infections are considered to appear following an imbalance in the oral resident microbiota, leading to the emergence of potentially pathogenic bacteria. The definition of the process involved in colonization by opportunistic respiratory pathogens needs to elucidate the factors responsible for the transition of the microbiota from commensal to pathogenic flora. The regulatory factors influencing the oral ecosystem can be divided into three major categories: the host defense system, commensal bacteria, and external pathogens. In this article, we review the profile of these categories including the intricate cellular interaction between immune factors and commensal bacteria and the disturbance in homeostasis in the oral cavity of hospitalized or bedridden elderly, which facilitates oral colonization by opportunistic respiratory pathogens.

Prevalence of genetic differences in phosphorylcholine expression between nontypeable Haemophilus influenzae and Haemophilus haemolyticus

BACKGROUND

Although non-typeable (NT) Haemophilus influenzae and Haemophilus haemolyticus are closely related human commensals, H. haemolyticus is non-pathogenic while NT H. influenzae is an important cause of respiratory tract infections. Phase-variable phosphorylcholine (ChoP) modification of lipooligosaccharide (LOS) is a NT H. influenzae virulence factor that, paradoxically, may also promote complement activation by binding C-reactive protein (CRP). CRP is known to bind more to ChoP positioned distally than proximally in LOS, and the position of ChoP within LOS is dictated by specific licD alleles (designated here as licDI, licDIII, and licDIV) that are present in a lic1 locus. The lic1 locus contains the licA-licD genes, and ChoP-host interactions may also be influenced by a second lic1 locus that allows for dual ChoP substitutions in the same strain, or by the number of licA gene tetranucleotide repeats (5'-CAAT-3') that reflect phase-variation mutation rates.

RESULTS

Using dot-blot hybridization, 92% of 88 NT H. influenzae and 42.6% of 109 H. haemolyticus strains possessed a lic1 locus. Eight percent of NT H. influenzae and none of the H. haemolyticus strains possessed dual copies of lic1. The licDIII and licDIV gene alleles were distributed similarly (18-22%) among the NT H. influenzae and H. haemolyticus strains while licDI alleles were present in 45.5% of NT H. influenzae but in less than 1% of H. haemolyticus strains (P < .0001). NT H. influenzae had an average of 26.8 tetranucleotide repeats in licA compared to 14.8 repeats in H. haemolyticus (P < .05). In addition, NT H. influenzae strains that possessed a licDIII allele had increased numbers of repeats compared to NT H. influenzae with other licD alleles (P < .05).

CONCLUSIONS

These data demonstrate that genetic similarities and differences of ChoP expression exist between NT H. influenzae and H. haemolyticus and strengthen the hypothesis that, at the population level, these differences may, in part, provide an advantage in the virulence of NT H. influenzae.

A novel selective medium for isolation of Aggregatibacter (Actinobacillus) actinomycetemcomitans

BACKGROUND AND OBJECTIVE

Conventional selective media have been used for the selection of Aggregatibacter (Actinobacillus) actinomycetemcomitans in clinical samples. The proportion of A. actinomycetemcomitans grown on the selective media in vitro may not reflect the true counts in vivo because of the low selectivity. A novel selective medium, designated AASM, was developed for the isolation of A. actinomycetemcomitans.

MATERIAL AND METHODS

AASM was prepared by adding of 200 microg/mL of vancomycin and 10 U/mL of bacitracin to AAGM, which contains dextrose, sodium bicarbonate, trypticase soy, yeast extract and agar. Clinical efficacy was evaluated by the recovery, on AASM, of A. actinomycetemcomitans from subgingival samples of 44 periodontally healthy subjects and 76 patients with chronic periodontitis.

RESULTS

All serotypes (a-f) of A. actinomycetemcomitans strains grew well, and the average growth recovery of A. actinomycetemcomitans on AASM medium was 94.4% (80.0-109.7%) of that on AAGM. The exclusive rate of other bacteria was 99.9% in clinical samples cultured on AASM. A. actinomycetemcomitans was not detected in periodontally healthy persons but was detected in 25 (32.9%) patients with chronic periodontitis. The predominant serotype was c, detected in 11 subjects.

CONCLUSION

The new selective medium, AASM, was highly selective for A. actinomycetemcomitans, eliminated possible false-positive results and was useful for the isolation of A. actinomycetemcomitans from clinical samples.

Diversity of antibiotic resistance integrative and conjugative elements among haemophili

The objective of this study was to investigate the sequence diversity in a single country of a family of integrative and conjugative elements (ICEs) that are vectors of antibiotic resistance in Haemophilus influenzae and Haemophilus parainfluenzae, and test the hypothesis that they emerged from a single lineage. Sixty subjects aged 9 months – 13 years were recruited and oropharyngeal samples cultured. Up to 10 morphologically distinct Pasteurellaceae spp. were purified, and then the species were determined and differentiated by partial sequence analysis of 16S rDNA and mdh, respectively. ICEs were detected by PCR directed at five genes distributed evenly across the ICE. These amplicons were sequenced and aligned by the neighbour-joining algorithm. A total of 339 distinguishable isolates were cultured. ICEs with all 5 genes present were found in 9 of 110 (8 %) H. influenzae and 21 of 211 (10 %) H. parainfluenzae, respectively. ICEs were not detected among the other Pasteurellaceae. A total of 20 of 60 (33 %) children carried at least 1 oropharyngeal isolate with an ICE possessing all 5 genes. One of the five genes, integrase, however, consisted of two lineages, one of which was highly associated with H. influenzae. The topology of neighbour-joining trees of the remaining four ICE genes was compared and showed a lack of congruence; though, the genes form a common pool among H. influenzae and H. parainfluenzae. This family of antibiotic resistance ICEs was prevalent among the children studied, was genetically diverse, formed a large gene pool, transferred between H. influenzae and H. parainfluenzae, lacked population structure and possessed features suggestive of panmixia, all indicating it has not recently emerged from a single source.

Microevolution and patterns of dissemination of the JP2 clone of Aggregatibacter (Actinobacillus) actinomycetemcomitans

The natural history, microevolution, and patterns of interindividual transmission and global dissemination of the JP2 clone of Aggregatibacter (Actinobacillus) actinomycetemcomitans were studied by population genetic analysis. The JP2 clone is strongly associated with aggressive periodontitis in adolescents of African descent and differs from other clones of the species by several genetic peculiarities, including a 530-bp deletion in the promoter region of the leukotoxin gene operon, which results in increased leukotoxic activity. Multilocus sequence analysis of 82 A. actinomycetemcomitans strains, 66 of which were JP2 clone strains collected over a period of more than 20 years, confirmed that there is a clonal population structure with evolutionary lineages corresponding to serotypes. Although genetically highly conserved, as shown by alignment of sequences of eight housekeeping genes, strains belonging to the JP2 clone had a number of point mutations, particularly in the pseudogenes hbpA and tbpA. Characteristic mutations allowed isolates from individuals from the Mediterranean area and from West Africa, including the Cape Verde Islands, to be distinguished. The patterns of mutations indicate that the JP2 clone initially emerged as a distinct genotype in the Mediterranean part of Africa approximately 2,400 years ago and subsequently spread to West Africa, from which it was transferred to the American continents during the transatlantic slave trade. The sustained exclusive colonization of individuals of African descent despite geographical separation for centuries suggests that the JP2 clone has a distinct host tropism. The colonization of family members by JP2 clone strains with unique point mutations provides strong evidence that there is intrafamilial transmission and suggests that dissemination of the JP2 clone is restricted to close contacts.

In vitro antimicrobial susceptibility of oral strains of Actinobacillus actinomycetemcomitans to seven antibiotics

BACKGROUND/AIMS

Periodontal infections with Actinobacillus actinomycetemcomitans seem to be refractory to conventional therapy. The aim of the present study was to test the in vitro susceptibilities of A. actinomycetemcomitans strains to a panel of seven orally administrable antibiotics.

METHODS

A total of 60 isolates of A. actinomycetemcomitans recovered from 43 individuals with gingivitis or periodontitis were tested. In addition, laboratory strains UP-6 and JP2 were analysed. The E-test was employed in order to determine minimal inhibitory concentrations (MIC) of antibiotics ampicillin/sulbactam, roxithromycin, azithromycin, doxycycline, metronidazole, ciprofloxacin, and moxifloxacin.

RESULTS

A. actinomycetemcomitans was highly susceptible to both fluoro-quinolones (MIC90 of 0.006 microgram/mL of ciprofloxacin and 0.032 microgram/mL of moxifloxacin). Good susceptibilities were found for ampicillin/sulbactam and doxycycline (MIC90 of 0.75 microgram/mL and 1 microgram/mL, respectively), and moderate susceptibilities for azithromycin (MIC90 of 3 microgram/mL). Most strains were resistant to metronidazole and roxithromycin. Cluster analysis revealed two larger clusters of A. actinomycetemcomitans strains with the smaller cluster assembling isolates with significantly higher MICs of most antibiotics.

CONCLUSIONS

Due to reported favourable pharmacokinetics, the fluoro-quinolone moxifloxacin appeared to be a promising candidate for adjunctive systemic antibiotic therapy in periodontal infections with A. actinomycetemcomitans.

Airway inflammation and etiology of acute exacerbations of chronic bronchitis

STUDY OBJECTIVES

The etiologic role of bacterial pathogens isolated from sputum culture in 40 to 50% of acute exacerbations of chronic bronchitis (AECB) is controversial. If bacterial pathogens cause these AECB, they should be associated with greater neutrophilic airway inflammation than pathogen-negative exacerbations.

DESIGN

This hypothesis was tested by comparing levels of interleukin (IL)-8, tumor necrosis factor (TNF)-alpha, and neutrophil elastase (NE) in 81 sputum samples obtained from 45 patients with AECB. Four groups were compared. In the first three groups, nontypable Haemophilus influenzae (n = 20), Haemophilus parainfluenzae (n = 27), and Moraxella catarrhalis (n = 14) were isolated as sole pathogens, respectively. In the fourth group, only normal flora was isolated (n = 20). Paired samples, obtained from individual patients at different times, that differed in their culture results were also compared.

SETTING

An outpatient research clinic at a Veterans Affairs Medical Center.

PATIENTS

These patients were participating in a prospective, longitudinal study of the dynamics of bacterial infection in chronic bronchitis, for which they were seen in the study clinic on a monthly basis as well as when they were experiencing symptoms suggestive of AECB.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

H influenzae exacerbations were associated with significantly higher sputum IL-8, TNF-alpha, and NE. M catarrhalis exacerbations demonstrated significantly higher sputum TNF-alpha and NE when compared to pathogen-negative exacerbations. H parainfluenzae-associated exacerbations had an inflammatory profile similar to pathogen-negative exacerbations. Sputum elastase level distinguished bacterial from nonbacterial AECB and correlated with clinical severity of the AECB.

CONCLUSIONS

Increased airway inflammation associated with isolation of H influenzae and M catarrhalis supports an etiologic role of these pathogens in AECB.

Actinobacillus actinomycetemcomitans in the human oral microflora

In this paper, the frequency of the microaerophilic gram-negative bacterium Actinobacillus actinomycetemcomitans (Ac) which is a component of the normal human oral microflora was investigated. Ac could be cultivated from oral material (molar sulcus and/or mucous membrane of the cheek) from 55 out of 405 healthy adults examined. This overall Ac frequency of 13.6% corresponds well to the few other reports existing in literature. A short discussion about the possible pathogenic potential of Ac is given at the end of the paper.

Clinical significance of Actinobacillus actinomycetemcomitans in young individuals during orthodontic treatment. A 3-year longitudinal study

The aim of the present study was: (1) to assess longitudinally the occurrence of Actinobacillus actinomycetemcomitans (Aa) in young subjects wearing fixed orthodontic appliances compared to matched appliance-free controls; (2) to determine whether the presence of the micro-organism at baseline could influence the periodontal status assessed 3 years later. 70 subjects, 27 male and 43 female, aged between 12 and 20 years participated in the study: 35 subjects under orthodontic treatment with fixed appliances for at least 6 months, and 35 appliance-free individuals matched for age and gender. All subjects were free of clinically demonstrable loss of attachment. They all received oral hygiene instructions 2x during the 2 months preceding the first clinical and microbiological examination. No subgingival instrumentation was performed between baseline and the 3-year examination. Clinical parameters included gingival bleeding index (GBI), pocket probing depth (PPD) and measurements of attachment level (AL). Statistically significant differences were reported regarding frequency of detection of Aa between both groups at each examination. The %s of orthodontic subjects infected with Aa at the baseline and at the 3-year examination were 86% and 80%, respectively, while the corresponding figures for control subjects were 16.6% and 26.6%. The frequency distribution of %s of Aa in the total anaerobic subgingival flora among control subjects remained fairly stable, whereas the proportion of orthodontic subjects yielding Aa at a concentration > or = 1.0% dropped significantly from 32% at baseline to 19% at the 3-year visit. Calculations of the relative risk for increasing GBI and PPD in both groups when Aa was present at baseline, revealed that the orthodontic subjects positive for Aa had a negligible relative risk of experiencing worse periodontal conditions compared to orthodontic patients where Aa was not detected at baseline. In contrast, control subjects initially infected with Aa presented with a risk for increased GBI 6.6x higher than that for subjects without Aa. In conclusion, the present study confirmed previous cross-sectional findings reporting that young individual with an integer periodontium wearing fixed orthodontic appliances harbor Aa with a statistically significant greater frequency than appliance-free matched controls. However, although orthodontic patients exhibited more inflammation, their deteriorated clinical conditions could not be accounted for by the sole presence of Aa in their sulci. In contrast, appliance-free young subjects initially infected with Aa had a higher risk of experiencing more gingival inflammation than subjects without the bacterium during a 3-year observation period.

Rapid identification of Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, and Haemophilus paraphrophilus by restriction enzyme analysis of PCR-amplified 16S rRNA genes

Restriction enzyme analysis of PCR-amplified 16S rRNA genes was used to distinguish among clinical isolates of Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, and Haemophilus paraphrophilus which were originally identified by conventional phenotypic methods. This PCR-based method is a reliable and rapid alternative to conventional methods for identification of these bacterial species.

Development of resistance to metronidazole and minocycline in vitro

By local delivery of antibiotics to periodontal pockets, very high initial concentrations are often quickly succeeded by subinhibitory concentrations, which may facilitate development of bacterial resistance. The purpose of the present study was to investigate possible development of resistance in suspected periodontal pathogens after exposure to subinhibitory concentrations of metronidazole and minocycline. The minimal inhibitory concentration (MIC) of 18 reference strains and 12 clinical isolates was determined by a broth dilution method. Subsequently, all strains with MIC < 8 micrograms/ml were exposed to serial passage on plates containing subinhibitory and gradually increasing concentrations of antibiotics, until growth was inhibited. Initially, most strains were inhibited at < or = 0.250 microgram/ml of minocycline and < or = 0.5 microgram/ml of metronidazole, though A. actinomycetemcomitans was resistant to metronidazole. After growth at subinhibitory concentrations, 8 strains survived 1-2 x and 11 stains survived 8-32 x their initial MIC of metronidazole, growing at up to 8 micrograms/ml. All A. actinomycetemcomitans survived 8-64 x their initial MIC of minocycline, growing at > or = 2 micrograms/ml, while all other strains were inhibited at < or = 0.250 microgram/ml, corresponding to a 1-8 x increase in their initial MIC. Thus, development of resistance was observed for periodontal bacteria growing at up to 64 x their initial MIC, but the final level of resistance was moderate.

Stoichiometry of oxygen consumption and sugar, organic acid and amino acid utilization in salivary sediment and pure cultures of oral bacteria

In each of 23 numerically or metabolically significant oral micro-organisms, and in each of the salivary sediments of 10 humans, oxygen uptake was determined quantitatively with various sugar and organic and amino acid substrates. With relatively few exceptions, the salivary sediments rapidly consumed oxygen with the array of substrates (23) tested. On the other hand, the individual pure cultures oxidized fewer substrates and did so selectively from this menu. The observation that the Gram-positive bacteria readily used oxygen when sugar substrates were provided, but were unable to use oxygen with all but one of the organic and none of the amino acids was significant. The Gram-negative bacteria, in contrast, used oxygen poorly with the sugars but most readily with many of the organic and amino acids, was significant. Only two of the Gram-positive but most of the Gram-negative micro-organisms tested showed oxygen uptake with L(+)-lactate; the Gram-negative bacteria were also active with D(-)-lactate, formate and succinate. Propionate was also tested and showed oxygen uptake only with the Gram-negative micro-organism, Neisseria subflava; acetate showed none or almost none with all of the examined bacteria. Where oxygen consumption occurred with the various pure or mixed cultures and substrates tested, the quantities of oxygen consumed were less than theoretically possible. For example, they ranged on average in the sediment results from 1.78 mumol oxygen per mumol of L(+)-lactate catabolized to 5.17 mumol oxygen per mumol of lactose. This was consistent with substrate oxidation by the oral bacteria being less than complete as in aerobic glycolysis, and with compounds other than water and carbon dioxide (such as acetate) being prominent amongst the end-products produced. The pure-culture oxygen data and other reports from this laboratory have made it possible to propose a speculative scheme as to which bacterial species might be involved in the various metabolic pathways used when different substrates are catabolized and oxidized by the mixed bacteria in salivary sediment or dental plaque. Also, it made it possible to suggest which bacteria and substrates are likely to be involved in the oxygen depletion that enables plaque to achieve anaerobiosis.

Occurrence of Actinobacillus actinomycetemcomitans in patients wearing orthodontic appliances. A cross-sectional study

The aim of the present study was to assess: (1) the occurrence of Actinobacillus actinomycetemcomitans (Aa) in subgingival plaque from young patients undergoing orthodontic treatment with fixed appliances; (2) a possible relationship between the presence of Aa and the clinical conditions; (3) a relation between the duration of orthodontic treatment and the microbiological and clinical parameters; (4) whether differences exist when taking into consideration the different type of appliances, i.e., bands or brackets. 34 subjects aged between 12 and 20 years participated in the study. Of these, 20 subjects had worn orthodontic appliances (test group), while the remaining 14 subjects served as matched control (control group). 4 to 8 sites in each patient were available for clinical and microbiological examination. Clinical parameters consisted of presence/absence of plaque and gingival bleeding index (GBI). Microbiological sampling was performed in the same sites as in the clinical examination. A statistically significant difference was present when comparing %s of GBI positive scores between teeth from the test group (57.5%) and teeth from the control group (25%). Plaque was present in 53% of test sites and 37% of control sites, but this difference was not statistically significant. Aa was detected from at least one site in 85% of test subjects and in 15% of the control subjects (p < 0.001). Among the subjects, 41% harboured Aa at a concentration between 0.1% and 1.0%, whereas another 40% yielded Aa at a concentration greater than 1.0%. Finally, a positive correlation was noted between the % of sites positive for Aa and the % of sites displaying a positive GBI score (r = 0.41; p < 0.005). No relation was found between the duration of orthodontic treatment and the microbiological or clinical parameters; neither were statistically significant differences found when we compared results from sites wearing bands or brackets. In conclusion, the present study showed that young subjects wearing orthodontic appliances harbour Aa with a remarkable frequency of detection, although plaque levels do not significantly differ from those of a matched control group.

Microflora in adult periodontitis

The subgingival microflora of adult periodontitis was studied in 8 adults (36-47 years) and compared with that of 10 periodontally healthy individuals (36-43 years). A total of 64 periodontal lesions were examined, and classified according to the attachment level in three categories: attachment loss > 6 mm, attachment loss 4-6 mm and attachment loss < 4 mm. Also for comparative purposes 20 gingival sulci were evaluated. Samples were taken using three standardized paper points and were incubated anaerobically in selective and non-selective media. The results showed a statistically significant association of Capnocytophaga gingivalis and Capnocytophaga sputigena with moderate periodontal lesions, while Haemophilus segnis has been correlated to severe periodontal lesions. We concluded that C. gingivalis, C. sputigena and H. segnis might be potentially conductive to periodontal deterioration in adult periodontitis.

Occurrence of Actinobacillus actinomycetemcomitans and anti-leukotoxin antibodies in some members of an extended family affected by Papillon-Lefèvre syndrome

Eighteen (18) members of an extended family in which numerous individuals have Papillon-Lefèvre syndrome (PLS) were examined. In all, 6 affected members and 12 non-affected members were included. All patients underwent a clinical examination which, in the dentate persons, included plaque index, bleeding on probing, probing depth, and periodontal attachment loss and a set of full mouth periapical x-rays. Subgingival bacterial samples were also collected from 2 teeth in the dentate patients for cultures and identification of Actinobacillus actinomycetemcomitans. Serum samples were collected from all participants and assayed for antileukotoxin antibodies. The results indicate that there is a high prevalence of leukotoxic strains of A. actinomycetemcomitans in persons suffering from PLS, as well as in unaffected family members. The ubiquitous presence of A. actinomycetemcomitans in the family units suggests a close association between A. actinomycetemcomitans and the periodontal disease associated with the syndrome; it also suggests that A. actinomycetemcomitans by itself is not sufficient for the expression of periodontal disease and that other factors, some of which must be genetic, are necessary for lesion development.

Simultaneous isolation of Actinobacillus actinomycetemcomitans from subgingival and extracrevicular locations of the mouth

In the present study, a total of 619 subgingival and extracrevicular samples from 66 early-onset periodontitis, 42 adult periodontitis/gingivitis and 36 treated Actinobacillus actinomycetemcomitans-associated periodontitis patients were selectively cultivated for presence of A. actinomycetemcomitans. The organism was recovered from 68% cases with early-onset periodontitis, 24% cases with adult periodontitis/gingivitis and 50% of treated patients. Associations between recovery from pooled subgingival plaque and samples from extracrevicular locations as well as between different extracrevicular samples, were not heterogeneous with regard to different groups with the exception for cheek/saliva comparisons (odds ratios: early-onset periodontitis 825; adult periodontitis 8.1; treated patients 117; 0.05 < p < 0.1). For associations between recovery of A. actinomycetemcomitans from pooled subgingival plaque/extracrevicular samples, Mantel-Haenszel's odds ratios of between 12.2 and 21.6 were calculated (p < 0.0001). The organism was isolated from 17 cheek mucosa samples of 18 patients identified as still harboring the organism after therapy. Present results point to the considerable value of cheek mucosa samples especially in treated patients to diagnose persistent A. actinomycetemcomitans colonization of the oral cavity.

Evidence for absence in northern Europe of especially virulent clonal types of Actinobacillus actinomycetemcomitans

Genetic analysis of an Actinobacillus actinomycetemcomitans population consisting of 88 clinically well characterized Finnish isolates performed by multilocus enzyme electrophoresis confirmed that the five serotypes divide into two phylogenetic lineages, one comprising serotypes b and c and one comprising serotypes a, d, and e. There was no association between any subpopulation and the periodontal health status of the subject from whom the isolates originated, suggesting that the role of A. actinomycetemcomitans in periodontitis is largely opportunistic in the population examined. Southern blot analyses of genomic DNA digested with each of the restriction endonucleases MspI, RsaI, and TaqI revealed extremely limited genetic polymorphism of the structural leukotoxin gene, ltxA, and its associated promoter. All isolates hybridized to a 530-bp DNA fragment derived from the promoter region of the leukotoxin gene operon of a minimally leukotoxic A. actinomycetemcomitans strain. Deletion of the 530-bp sequence has been associated with significantly increased toxin production detected among isolates from patients with juvenile periodontitis in North America but was detected neither among the 88 isolates in the present collection analyzed nor among more than 60 strains in another population of northern European A. actinomycetemcomitans isolates analyzed previously.

Binding of human high-molecular-weight salivary mucins (MG1) to Hemophilus parainfluenzae

In human saliva, two different mucin populations can be distinguished, viz., high-molecular-weight mucins (MG1, mol. wt > 1 x 10(6)) and low-molecular-weight mucins (MG2, mol. wt approximately 125 kD). The carbohydrate moiety of MG1 displays a wide spectrum of oligosaccharide structures, varying in composition, length, branching, and acidity. The biological significance of the heterogeneity in carbohydrate structures of mucins is unclear. The present investigation focused on the question whether MG1, because of its diverse carbohydrate side-chain population, can bind to a large variety of oral micro-organisms. A replica plate technique, in combination with immunochemical detection with monoclonal antibodies against MG1, was used to screen in vivo human oral microflora for the presence of micro-organisms which could bind the high-molecular-weight salivary mucin MG1. Binding to purified MG1 was established for Hemophilus (para)influenzae species, whereas other species, including Streptococcus and Staphylococcus, were negative. MG1 binding to Hemophilus parainfluenzae could be abolished by protease treatment of MG1. In contrast, periodate acid treatment, partial deglycosylation, or addition of monosaccharides did not affect MG1 binding to H. parainfluenzae, indicating that MG1 carbohydrate side-chains were not directly involved in the binding. The binding was pH-dependent, showing an increase when the pH was lowered from 8.0 to 4.0. These data indicate that MG1 can be bound in a selective manner by Hemophilus spp. and suggest that the 'naked' unglycosylated polypeptide moiety of MG1 is involved in its binding to Hemophilus parainfluenzae.

Evaluation of the antimicrobial effects of sodium benzoate and dichlorobenzyl alcohol against dental plaque microorganisms. An in vitro study

Evaluation of antimicrobial agents is based on in vivo and in vitro studies. The minimum inhibitory concentrations (MICs) of sodium benzoate and dichlorobenzyl alcohol to 115 strains of plaque microorganisms were determined by a broth-dilution method. Sodium benzoate did not inhibit growth of any gram-positive cocci (MIC > 106,590 microM). MICs for Porphyromonas gingivalis and two strains of Treponema socranskii were 26,650 microM. The MIC of dichlorobenzyl alcohol to the reference strain of Actinobacillus actinomycetemcomitans was 723 microM and to P. gingivalis, two strains of T. socranskii, and Candida albicans 1,446 microM. MICs for other organisms were 2,892 to 5,784 microM. Saliva samples from 10 volunteers, collected at various times after toothbrushing with a dentifrice containing 10% sodium benzoate and 0.3% dichlorobenzyl alcohol, were analyzed gas-chromatographically. Immediately after toothbrushing mean levels of sodium benzoate and dichlorobenzyl alcohol were 372,626 microM and 7,529 microM, respectively. After 5 min mean levels were 38,700 microM and 734 microM. In conclusion, the concentrations of both antimicrobials dropped rapidly during the first 30 min, but for 5-10 min they were high enough to inhibit growth of potential periodontal pathogens.

Use of a nonradioactive genetic probe identified, synthesized, and labeled in the polymerase chain reaction

This study introduces a strategy to identify and produce sequences useful as genetic markers, or native genetic probes for DNA-DNA hybridization in bacterial strains where the genetics is not well described. Actinobacillus actinomy-cetemcomitans (A.a.) was used as an example. Fifty ng genomic DNA from A.a. ATCC 33384 and Haemophilus aphrophilus ATCC 33389 was amplified in a thermocycler using a single 10-mer primer. The PCR products were separated by electrophoresis on a 1% submarine agarose gel containing ethidium bromide and visualized by UV illumination, and the strain-specific amplitypes were compared. DNA from two bands, 0.9 and 4 kb, unique for the A.a. strain, was cut out, amplified under high stringency with the same primer and labeled by replacing 33.3 microM dTTP with digoxigenin-labeled dUTP in the reaction mixture. The labeled probe was then repeatedly used for hybridization to DNA from various A.a., H. aphrophilus, and other bacterial strains of the Pasteurellaceae family. The results showed that the 0.9-kb probe detected all A.a. tested, and distinguished it from other closely related bacterial species. We conclude that the described strategy is useful for identifying and selecting genetic sequences useful as genetic markers in A.a.

Recent approaches to the chemotaxonomy of the Actinobacillus-Haemophilus-Pasteurella group (family Pasteurellaceae)

Many members of the Actinobacillus-Haemophilus-Pasteurella group (family Pasteurellaceae) have been misclassified. This article reviews the chemotaxonomic characters that recently have been provided to improve the taxonomy of Pasteurellaceae. These include fatty acids of whole cells, of lipopolysaccharides and of single colonies, together with sugar contents of whole cells, of whole defatted cells, of lipopolysaccharides and of single colonies. This article also reviews taxonomy aided by distribution of proteins in whole cells and outer membranes, distribution of enzymes in outer membrane vesicles and in whole cells, bacteriolysis induced by ethylenediaminetetraacetic acid and hen eggwhite lysozyme and the distribution of respiratory quinones. Furthermore, an overview of characters obtained through studies on genetic transformation, restriction enzyme analysis, restriction fragment length polymorphism, DNA-DNA hybridization, DNA-rRNA hybridization, and 16S rRNA sequencing is given.

Polymorphonuclear leukocyte chemiluminescence induced by Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus in serum and saliva

The ability of different strains of Actinobacillus actinomycetemcomitans (A.a.) and Haemophilus aphrophilus (H.a.) to trigger activation of an oxidative burst in human polymorphonuclear leukocytes (PMNL) was examined by measuring the luminol-amplified light emission--chemiluminescence (CL)--from these cells. Bacterial cells were incubated with PMNL from one healthy subject, in the presence of either active serum, heat-inactivated serum, saliva, or saliva and active serum. In the presence of active serum, all five H.a. strains and two out of five A.a. strains triggered a CL response. The CL induced in the presence of heat-inactivated serum was considerably less than that achieved with fresh serum. In the presence of only saliva, all strains induced considerably weaker CL responses than those induced in the presence of saliva with active serum. In the presence of serum, intracellular reactions appeared to be the main source of CL, while addition of saliva and active serum increased the extracellular CL. The results indicate that strain-dependent differences exist among A.a. strains in their ability to trigger the oxygen-dependent bactericidal mechanisms of human PNML. In contrast, the CL patterns of H.a. strains were equivalent. Various factors in the environment, such as activated complement and salivary compounds, affect the interaction of these species with neutrophils.

Ribotyping shows intrafamilial similarity in Actinobacillus actinomycetemcomitans isolates

This study reports ribosomal RNA gene restriction patterns of 54 Actinobacillus actinomycetemcomitans isolates obtained from 9 families (12 children and 11 parents). The isolates represented serotypes a, b, c and d. The chromosomal DNA extracted from A. actinomycetemcomitans isolates was digested with the restriction endonucleases EcoRI, BamHI, HindIII, ClaI and Bg/I. The DNA fragments were hybridized to the rrnB ribosomal RNA operon of the Escherichia coli chromosome. In 5 families, isolates belonging to the same family (mother and/or father and the children) had identical hybridization patterns when analyzed with all 5 enzymes. In 3 families, each family member harbored only one ribotype of A. actinomycetemcomitans, but at least one member harbored isolates that were of a different ribotype than the other members of the family. In one family, the mother harbored 2 ribotypes (and serotypes), one common with the daughter and one different. In conclusion, the study confirms the previous results that A. actinomycetemcomitans is transmitted intrafamilially.

An analysis of the diversity of Haemophilus parainfluenzae in the adult human respiratory tract by genomic DNA fingerprinting

A method for typing Haemophilus species is described, based on the analysis of genomic DNA from Haemophilus parainfluenzae. The DNA was extracted by a rapid method and digested with the restriction enzyme BamHI to provide a characteristic 'fingerprint'. The pattern of fragments in the ranges 1-1.6 kb, 1.6-2 kb and 2-3 kb were used to produce a numerical profile of each isolate. In total 97 isolates were examined; 88 from throat swab material isolated from the 15 members of a British Antarctic Survey base and 9 type strains. Seventy-two of the 88 antarctic isolates were H. parainfluenzae and were found to be very diverse, comprising 41 identifiable strains with up to 5 strains being isolated from a single throat swab sample. There was evidence for both carriage and transmission within the isolated community. The technique provided a highly discriminatory method for characterizing Haemophilus strains which is suitable for epidemiological studies.

Killing of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus by human polymorphonuclear leukocytes in serum and saliva

The ability of polymorphonuclear leukocytes from human peripheral blood to kill Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus was examined with fresh isolates and laboratory strains from each species (5 strains within each group) under different conditions. Bacterial cells were mixed with a polymorphonuclear leukocyte suspension in the presence of either active serum or heat-inactivated serum or active serum together with sterile-filtered saliva. Surviving bacteria were determined by counting the number of bacterial colony-forming units in the mixtures after a 60-min incubation at 37 degrees C. Mixtures without polymorphonuclear leukocytes served as controls for the evaluation of the degree of killing of the bacteria. In general, A. actinomycetemcomitans resisted phagocytic killing to a greater extent than H. aphrophilus, and the killing of the former species mainly depended on the presence of heat-labile serum components, probably complement factors. Laboratory strains of A. actinomycetemcomitans were more easily killed than fresh isolates. The presence of saliva in the reaction mixtures decreased the degree of killing. However, strain-dependent variations in the killing were found under either condition. The leukotoxic activity of A. actinomycetemcomitans strains, determined by a [51Cr]-release assay, was not correlated with the resistance of these strains to the phagocytic killing. The results point out a strain-dependent difference in the ability of A. actinomycetemcomitans to evade the inflammatory response associated with polymorphonuclear leukocytes. This difference may constitute a potential virulence factor for this periodontopathogen. Furthermore, the leukotoxicity of the strains is not the main determinant that modifies the interaction of A. actinomycetemcomitans with human neutrophils.

Identification of Actinobacillus actinomycetemcomitans: polymerase chain reaction amplification of lktA-specific sequences

Actinobacillus actinomycetemcomitans has been strongly implicated in the etiology of localized juvenile periodontitis. Techniques used in the identification of this periodontal pathogen include cultural, biochemical, immunological and DNA hybridization analysis. In this study, we report the use of polymerase chain reaction (PCR) to amplify unique sequences of A. actinomycetemcomitans. Specific oligonucleotide primers LKT2 and LKT3 were designed to hybridize to the A. actinomycetemcomitans lktA gene, which encodes leukotoxin, a putative A. actinomycetemcomitans virulence factor. The LKT2 and LKT3 primers amplified lktA-specific sequences from all 12 A. actinomycetemcomitans strains tested. In another set of experiments, 13 other bacterial species, most of which are normal residents of the oral cavity, were tested with these primers. These PCR amplifications also contained 2 additional primers, RRN4 and RRN5, which served as positive controls; RRN4 and RRN5 were designed to amplify specific sequences of eubacterial 16S ribosomal DNA (rDNA). PCR amplifications of all bacterial species tested, including A. actinomycetemcomitans, yielded 16S rDNA-specific DNA fragments. Furthermore, each bacterial species tested, with the exception of A. actinomycetemcomitans, failed to amplify lktA sequences. The LKT and RRN primers were used in further PCR experiments to detect A. actinomycetemcomitans directly from gingival fluid samples. The results clearly demonstrate the simplicity, rapidity, specificity and accuracy of the LKT primers in the identification of A. actinomycetemcomitans.

Ecology of Haemophilus influenzae and Haemophilus parainfluenzae in sputum and saliva and effects of antibiotics on their distribution in patients with lower respiratory tract infections

Nine patients with lower respiratory tract infections were used to study in detail the effect of ampicillin or erythromycin on the colonization patterns of Haemophilus influenzae and Haemophilus parainfluenzae in sputum and saliva. H. influenzae was isolated from purulent sputum of eight patients before the start of treatment. Ampicillin was more effective than erythromycin at clearing H. influenzae from sputum and in decreasing purulence. By careful characterization of multiple strains, the changes in biotype distribution and antibiotic susceptibility patterns were shown. Five biotypes of H. influenzae were associated with chest infection, with type II predominating. Mixed biotype infections occurred in five patients. Most saliva contained multiple biotypes of H. parainfluenzae. Neither antibiotic selected resistant haemophili in saliva or sputum. After treatment with ampicillin, the mucoid sputum was colonized with ampicillin-susceptible H. parainfluenzae biotypes previously found in saliva. We postulate that as inflammation decreases at the bronchial mucosa, the ampicillin concentration drops, allowing ampicillin-susceptible oral H. parainfluenzae isolates to seed the residual mucoid sputum.

Local and systemic antibody response to putative periodontopathogens in patients with chronic periodontitis: correlation with clinical indices

Specific immunoglobulin G (IgG), IgA and IgM antibody titres to Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans were measured by enzyme-linked immunosorbent assay in serum and gingival crevicular fluid at 5 sites in each of 20 chronic periodontitis patients. Specific serum antibody titres correlated with mean gingival crevicular fluid titres. The 3 immunoglobulin subclass responses (IgA, IgG and IgM) to P. gingivalis correlated. A comparison of sites with probing depth < 4 mm and > or = 4 mm showed that the latter group had significantly lower gingival crevicular fluid IgG titres to P. gingivalis. Sites with a gingival index of 3 had significantly lower gingival crevicular fluid IgG titres to this organism than those with a gingival index of less than 3. These findings support the concept that the humoral immune response is protective, as chronic periodontitis patients with greater pocket depths and more gingival inflammation had paradoxically lower antibody titres to suspected periodontopathogens.

Hybridization patterns of Actinobacillus actinomycetemcomitans serotypes a-e detected with an rRNA gene probe

This study reports a genetic characterization of Actinobacillus actinomycetemcomitans strains in relation to serotypes by using rRNA gene restriction patterns. Eighty-eight clinical strains were isolated from 20 unrelated subjects at one or several occasions. The strains were serotyped by using serotype-specific rabbit antisera against serotypes a, b, c, d or e. Three subjects harbored 2 A. actinomycetemcomitans serotypes, 15 subjects 1 serotype and 2 subjects untypable strains. Chromosomal DNA was digested with restriction endonuclease ClaI, BamHI, BglI or HindIII and hybridized to the rrnB ribosomal RNA operon of the Escherichia coli chromosome. Isolates belonging to the same serotype were genetically identical in the same individual but nonidentical if they belonged to different serotypes. Isolates of the same or different serotypes were genetically nonidentical in different individuals. The banding patterns of A. actinomycetemcomitans isolates recovered from the same individuals during several years always remained identical. The hybridization method using pKK3535 as a probe seemed suitable as an epidemiological tool for comparing the clonal identity of A. actinomycetemcomitans strains.

Microbiology of early supragingival plaque development after delmopinol treatment

The aim of this double blind, cross-over, microbiological study was to compare the effect of topical application of the plaque control agent 0.5% delmopinol HCl with placebo on early supragingival plaque formation. Six subjects underwent 7 periods (0.5, 1, 2, 8 and 24 h and 3 and 7 days) of placebo and delmopinol application, respectively. At the start of each study period the teeth were professionally cleaned and 2 ml of placebo and delmopinol 0.5%, respectively, were applied on all teeth (twice daily for periods lasting 24 h or more). At the end of each period, supragingival plaque samples of one upper and one lower buccal tooth surface were collected separately and cultured on anaerobically incubated Brucella blood agar, on aerobically incubated blood agar and on selective media for the enumeration of Streptococcus spp., Haemophilus spp., Actinomyces spp., Veillonella spp., Neisseria spp. and Fusobacterium spp. The total anaerobic cultivable microflora after delmopinol use was 10-100 times lower than after placebo use. Compared with placebo, the proportion of cultivable aerobes (61.3%), Streptococcus spp. (104.8%) and Haemophilus spp. (82.3%) increased and the proportion of Actinomyces spp. (86.1%), Veillonella spp. (60.5%), Neisseria spp. (96.9%) and Fusobacterium spp. (60.6%) decreased after 7 days. Short-term application of 0.5% delmopinol HCl on supragingival dental plaque regrowth resulted in a reduction of the number of cultivable microorganisms in the plaque and produced a shift in the cultivable plaque composition.

Sub-gingival microflora in Macaca mulatta species of rhesus monkey

The Macaca mulatta species of rhesus monkey is one of several non-human primate (nhp) models for periodontal disease. This report presents the bacteriology of the gingival sulci in M. mulatta monkeys. Three sub-gingival sites (maxillary right central incisor, the disto-buccal of the mandibular left second molar and mesio-buccal of the mandibular right second molar) of 9 monkeys were evaluated clinically before scaling and 7 days after scaling. Plaque samples were obtained from sub-gingival sites before clinical examination and studied bacteriologically by dark field microscopy, selective and non-selective culture, and by primary phenotypic characterizations of culture isolates. Several gingival sites presented with mild gingival inflammation. Anaerobic and facultatively anaerobic bacteria were the predominant flora colonizing the gingival sulci. The major microbial groups were Haemophilus species (100% of sites; percentage of total anaerobic count (TAC): 21-51), Peptostreptococcus micros (89%, 7.5-29.5), Actinomyces sp. (85%, 7-27), Fusobacterium nucleatum (90%, 5-8), Actinobacillus actinomycetemcomitans (73%, 1.3-12), black-pigmented anaerobic rods (BPAR) (80%, 0.6-6.5) and oral streptococci (80%, 0.2-1.0). Microbial groups detected less often were Wolinella sp. (66%, 0-2.6), Capnocytophaga sp. (30%), Eikenella corrodens (4.7%, 0), Campylobacter sp. (28%, 0-0.1) and spirochetes (4.7%, 0-0.07). Seven days after gingival sites were scaled, the plaque score and indices for gingival inflammation declined significantly. The gingival flora after scaling were characterized by lower proportions of the Actinomyces sp., P. micros and BPAR; and increased proportions of the oral streptococci, relative to pre-scaling levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid identification of Actinobacillus actinomycetemcomitans based on analysis of 23S ribosomal RNA

Actinobacillus actinomycetemcomitans is a key microorganism in the pathogenesis of several different forms of periodontal diseases. Identification of this bacterium from clinical specimens may often be complicated by the fact that the colony morphology on TSBV selective medium closely resembles that of Haemophilus aphrophilus and a key differentiating characteristic, catalase reaction, may be variable. Recent genetic studies have shown that the 23S ribosomal RNA molecule is split into two smaller forms in A. actinomycetemcomitans, but is intact in H. aphrophilus. Based on this finding, we describe a new, rapid method for identifying A. actinomycetemcomitans in which single colonies isolated from culture on TSBV agar in 5% CO2 in air are lysed, electrophoresed on 1.5% submarine agarose gels and visualized by staining with ethidium bromide. Using this assay, A. actinomycetemcomitans can be easily distinguished from morphologically similar colonies such as H. aphrophilus strains by differences in 23S rRNA within 2 h.

Comparative clinical and microbiological effects of topical subgingival application of metronidazole 25% dental gel and scaling in the treatment of adult periodontitis

The aim of the study was to compare the clinical and microbiological effects of topical application of a metronidazole gel and a single session of subgingival scaling in the treatment of adult periodontitis. An open, randomized controlled clinical study design was employed. Each of 24 subjects received the 2 treatments simultaneously each in 2 randomly selected quadrants of the dentition. The metronidazole, 25% gel was applied subgingivally on days 0 and 7. Scaling was carried out in one quadrant on day 0 and in one quadrant on day 7. Clinical and microbiological examinations were carried out before treatment and on days 21, 49, 91, 133, and 175 of the experimental period. The microbiological analyses included determination of total anaerobically cultivable bacteria, and relative proportions of anaerobes, aerobes, black-pigmented anaerobic Gram negative rods, Actinobacillus actinomycetemcomitans, streptococci, and spirochetes. Both treatments were effective in reducing probing pocket depth and bleeding on probing. Metronidazole tended to be a little better than scaling during the study period and the clinical effects of both treatments persisted during the whole 6 months observation period. Local metronidazole treatment induced a significant and long-lasting shift in the subgingival flora towards a composition more compatible with health and comparable to that obtained by mechanical debridement. Proportions of black pigmented anaerobes including Prevotella intermedia, and the number of spirochetes were significantly reduced after both treatments with a concomitant increase in the proportions of streptococci. While scaling resulted in a statistically significant increase in the proportion of A. actinomycetemcomitans, this was avoided after metronidazole treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

A follow-up case report of Actinobacillus actinomycetemcomitans in human periodontal disease

The purpose of this investigation was to compare clinical and microbial parameters in a follow-up case report of adult subjects harboring Actinobacillus actinomycetemcomitans (Aa) with clinically matched subjects who did not have detectable Aa. 16 subjects with Aa and 16 subjects without Aa at the baseline examination were re-examined at an average of 46 months following collection of baseline data. Clinical measurements were recorded and subgingival plaque sampled and evaluated for microbial flora from each maxillary first molar. In 16 subjects with Aa at baseline, 4 sites in 3 subjects had detectable actinobacilli at the follow-up appointment. 26 sites in 13 individuals with Aa at baseline had a significantly increased gingival index at the follow-up visit (p less than or equal to 0.05), but there was no significant increase in probing depth or attachment loss. 32 sites in the 16 subjects without Aa at baseline still did not have detectable levels of this microorganism at the follow-up examination nor was there any significant difference between baseline and the follow-up appointment for the gingival index, probing depth and attachment level measurements. In subjects with Aa at baseline, 1 of 12 teeth without Aa and 5 of 20 teeth with Aa had been extracted prior to the follow-up visit. In this population group, having sites where Aa was detected, 6 of 9 teeth which had a probing depth greater than or equal to 5 mm were lost before the follow-up data collection appointment. In the control group, which did not have detectable Aa at baseline, 9 teeth with probing depths greater than or equal to 5 mm were not lost. These observations, although not proving, suggest in this population group, that deeper probing depths taken together with the presence of Aa may have placed an individual at greater risk of tooth loss.

Cell surface hydrophobicity and electrokinetic potential of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus

Laboratory strains and fresh isolates of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus were examined for cell surface hydrophobicity and for electrokinetic properties under different experimental conditions. Fresh isolates of A. actinomycetemcomitans and H. aphrophilus were hydrophobic. Laboratory strains of A. actinomycetemcomitans were 20-30% less hydrophobic than fresh isolates. No difference was observed between laboratory and fresh isolates of H. aphrophilus. The pH of the suspending buffer, growth phase or incubation atmosphere did not significantly affect the hydrophobicity of the 2 species, whereas agar cultures of H. aphrophilus were less hydrophobic than broth cultures. All A. actinomycetemcomitans strains treated with sterile filtered saliva showed a concentration-dependent decrease in hydrophobicity of at most 30%. H. aphrophilus strains were not affected by the same treatment. Laboratory strains of H. aphrophilus were more negatively charged than A. actinomycetemcomitans, whereas fresh isolates of the 2 species exhibited similar surface charge. In the presence of saliva the mean cell surface charge of laboratory strains decreased by 56% for A. actinomycetemcomitans and by 73% for H. aphrophilus. The results indicate that the 2 species differ in expression of cell structures accounting for hydrophobicity and surface charge and that environmental factors might differently influence the physical properties of the two species analyzed.

Are certain oral pathogens part of normal oral flora in denture-wearing edentulous subjects?

A complete loss of teeth may eliminate some pathogenic bacteria for lack of a suitable habitat for colonization. The occurrence of Actinobacillus actinomycetemcomitans, black-pigmented Bacteroides, mutans streptococci, lactobacilli and yeasts was investigated in 51 edentulous subjects with complete denture(s); mean age 74 years (range 44-92 years). None of the subjects had received antibiotics during the preceding 6 months. Four swab samples per subject were taken from the fitting surface of the upper denture, from the palate, buccal mucosae and dorsum of the tongue. At least 0.5 ml of stimulated saliva was collected into a sterile tube. The samples were cultivated aerobically and anaerobically using nonselective and selective media. A. actinomycetemcomitans was not found in any of the samples. Black-pigmented Bacteroides were found in 49 (96%) and yeasts in 25 (49%) of the subjects. Of the 49 saliva samples, 41 (84%) yielded mutans streptococci and 45 (92%) lactobacilli. In contrast to black-pigmented Bacteroides, mutans streptococci and lactobacilli, A. actinomycetemcomitans may not belong to the normal oral flora of edentulous subjects wearing dentures.