Actinobacillus Actinomycetemcomitans and Hemophilus Aphrophilus

Invasive Aggregatibacter infection: shedding light on a rare pathogen in a retrospective cohort analysis

Introduction. Aggregatibacter are Gram-negative, facultatively anaerobic rods or coccobacilli that are infrequently encountered as pathogens causing infection.Hypothesis/Gap Statement. The range of invasive infection that Aggregatibacter cause is poorly described. The pathogenicity of species such as Aggregatibacter segnis is debated.Aim. To identify invasive infection due to Aggregatibacter species in a large healthcare organization and to characterize clinical syndromes, co-morbidities and risk factors.Methodology. All microbiological samples positive for Aggregatibacter species were identified by conventional culture or 16S rRNA PCR between October 2017 and March 2021. Electronic records for all patients with positive samples were reviewed and the infection syndrome classified for patients with invasive disease.Results. Twenty-seven patients with invasive infection were identified, with a statistically significant difference in species-specific patterns of invasive infection (P=0.02) and a statistically significant association with residence in the 30 % most deprived households in the UK by postcode (P<0.01). The three most common co-morbidities were periodontitis or recent dental work (29.6%), cardiovascular disease (25.9%) and diabetes (18.5 %).Conclusion. We describe a novel association of Aggregatibacter segnis with skin and soft tissue infection. The propensity of the Aggregatibacter species to cause invasive infection at different body sites and be associated with deprivation is reported. Aggregatibacter actinomycetemcomitans bacteraemia was associated with infective endocarditis, and Aggregatibacter aphrophilus was implicated in severe appendicitis and noted to cause brain abscess. Areas warranting future research include exploring the risk-factors required for invasive infection and those that may determine the species-specific differences in patterns of invasive disease.

Aggregatibacter Actinomycetemcomitans: Clinical Significance of a Pathobiont Subjected to Ample Changes in Classification and Nomenclature

Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium that is part of the oral microbiota. The aggregative nature of this pathogen or pathobiont is crucial to its involvement in human disease. It has been cultured from non-oral infections for more than a century, while its portrayal as an aetiological agent in periodontitis has emerged more recently. A. actinomycetemcomitans is one species among a plethora of microorganisms that constitute the oral microbiota. Although A. actinomycetemcomitans encodes several putative toxins, the complex interplay with other partners of the oral microbiota and the suppression of host response may be central for inflammation and infection in the oral cavity. The aim of this review is to provide a comprehensive update on the clinical significance, classification, and characterisation of A. actinomycetemcomitans, which has exclusive or predominant host specificity for humans.

Rheumatoid Arthritis-Associated Mechanisms of Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans

Rheumatoid arthritis (RA) is an autoimmune disease of unknown etiology characterized by immune-mediated damage of synovial joints and antibodies to citrullinated antigens. Periodontal disease, a bacterial-induced inflammatory disease of the periodontium, is commonly observed in RA and has implicated periodontal pathogens as potential triggers of the disease. In particular, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans have gained interest as microbial candidates involved in RA pathogenesis by inducing the production of citrullinated antigens. Here, we will discuss the clinical and mechanistic evidence surrounding the role of these periodontal bacteria in RA pathogenesis, which highlights a key area for the treatment and preventive interventions in RA.

Whole-Genome Sequencing of Aggregatibacter Species Isolated from Human Clinical Specimens and Description of Aggregatibacter kilianii sp. nov

Aggregatibacter species are commensal bacteria of human mucosal surfaces that are sometimes involved in serious invasive infections. During the investigation of strains cultured from various clinical specimens, we encountered a coherent group of 10 isolates that could not be allocated to any validly named species by phenotype, mass spectrometry, or partial 16S rRNA gene sequencing. Whole-genome sequencing revealed a phylogenetic cluster related to but separate from Aggregatibacter aphrophilus The mean in silico DNA hybridization value for strains of the new cluster versus A. aphrophilus was 56% (range, 53.7 to 58.0%), whereas the average nucleotide identity was 94.4% (range, 93.9 to 94.8%). The new cluster exhibited aggregative properties typical of the genus Aggregatibacter Key phenotypic tests for discrimination of the new cluster from validly named Aggregatibacter species are alanine-phenylalanine-proline arylamidase, N-acetylglucosamine, and β-galactosidase. The name Aggregatibacter kilianii is proposed, with PN_528 (CCUG 70536^T or DSM 105094^T) as the type strain.

Serotypes of Aggregatibacter actinomycetemcomitans in relation to periodontal status and assessment of leukotoxin in periodontal disease: A clinico-microbiological study

Context:

Aggregatibacter actinomycetemcomitans (A.a) serotypes may add some important information of the pathogenetic background of periodontal infections. A.a leukotoxin is an important virulence factor in the pathogenesis of periodontal disease and its rate of progression. When compared to minimally leukotoxic strains, variants of A.a highly leukotoxic strains produce 10–20 times more leukotoxin.

Aims:

The aim of the present study was to detect serotypes a, b, c, d, and e of A.a its leukotoxin and find its correlation with periodontal status.

Settings and Design:

Microbiological analysis and cross-sectional study.

Materials and Methods:

A total of 80 subjects (40 chronic periodontitis and 40 aggressive periodontitis) in the age range of 14–55 years were selected. Subgingival plaque samples were collected and checked for the presence of A.a. Following isolation of the organism, detection of the serotypes and leukotoxin assessment was done.

Statistical Analysis Used:

The proportions of A.a were calculated using descriptive statistics in terms of percentage. Chi-square test was used to find association between serotype, leukotoxin, and periodontal disease in individual group.

Results:

Out of 80 plaque samples, 45% tested positive for A.a. serotype b was detected in 33.33%, whereas serotype e in 8.33% samples and serotype c in 2.77% samples. Serotypes a and d were not detected in any of the samples. A combination of serotypes was seen in 47.22% of the sites. Of these 76.47% showed a combination of 2 serotypes, while 23.52%showed a combination of 3 serotypes. 8.33% showed untypable serotype. All samples had low-toxic variants of A.a.

Conclusions:

Serotype b and serotype e were predominant in chronic periodontitis, and serotype b was predominant in aggressive periodontitis. An association could be present between serotype and periodontal disease.

[Cutaneous infection with Aggregatibacter actinomycetemcomitans]

BACKGROUND

Aggregatibacter actinomycetemcomitans is a small, gram-negative, non-motile, coccobacillus. Aggregatibacter actinomycetemcomitans is known to cause periodontal disease and to be associated with actinomycosis.

CASE REPORT

We report a patient developed a chronic wound following trauma about the right heel. The lesion resolved after oral antibiotic therapy with cefpodoxime und surgical debridement. Bacterial cultures grew abundant Aggregatibacter actinomycetemcomitans, but no actinomyces species.

OBJECTIVE

The importance of Aggregatibacter actinomycetemcomitans in chronic wounds needs to be explored.

Classification, identification, and clinical significance of Haemophilus and Aggregatibacter species with host specificity for humans

The aim of this review is to provide a comprehensive update on the current classification and identification of Haemophilus and Aggregatibacter species with exclusive or predominant host specificity for humans. Haemophilus influenzae and some of the other Haemophilus species are commonly encountered in the clinical microbiology laboratory and demonstrate a wide range of pathogenicity, from life-threatening invasive disease to respiratory infections to a nonpathogenic, commensal lifestyle. New species of Haemophilus have been described (Haemophilus pittmaniae and Haemophilus sputorum), and the new genus Aggregatibacter was created to accommodate some former Haemophilus and Actinobacillus species (Aggregatibacter aphrophilus, Aggregatibacter segnis, and Aggregatibacter actinomycetemcomitans). Aggregatibacter species are now a dominant etiology of infective endocarditis caused by fastidious organisms (HACEK endocarditis), and A. aphrophilus has emerged as an important cause of brain abscesses. Correct identification of Haemophilus and Aggregatibacter species based on phenotypic characterization can be challenging. It has become clear that 15 to 20% of presumptive H. influenzae isolates from the respiratory tracts of healthy individuals do not belong to this species but represent nonhemolytic variants of Haemophilus haemolyticus. Due to the limited pathogenicity of H. haemolyticus, the proportion of misidentified strains may be lower in clinical samples, but even among invasive strains, a misidentification rate of 0.5 to 2% can be found. Several methods have been investigated for differentiation of H. influenzae from its less pathogenic relatives, but a simple method for reliable discrimination is not available. With the implementation of identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry, the more rarely encountered species of Haemophilus and Aggregatibacter will increasingly be identified in clinical microbiology practice. However, identification of some strains will still be problematic, necessitating DNA sequencing of multiple housekeeping gene fragments or full-length 16S rRNA genes.

Infective endocarditis due to Eikenella corrodens: Case report and review of the literature

Eikenella corrodens is an uncommon cause of bacterial endocarditis. In the 11 reported cases in the literature, the disease was associated with predisposing factors and was clinically indolent or subacute. A case is reported which in contrast to the reported literature was acute in onset with severe heart failure, requiring urgent valve replacement.

Invasive infections of Aggregatibacter (Actinobacillus) actinomycetemcomitans

BACKGROUND/PURPOSE

Aggregatibacter (Actinobacillus) actinomycetemcomitans, part of the normal flora of the mouth, is frequently found in human periodontal cultures and is an important pathogen causing various invasive infections, particularly infective endocarditis. In this study, we describe the clinical course and outcome of patients with A. actinomycetemcomitans infection.

METHODS

All patients suffering invasive A. actinomycetemcomitans infections at the National Taiwan University Hospital from January 1985 to December 2004 were included in this study. Relevant data regarding clinical presentation, antimicrobial treatment and outcome of these patients were analyzed.

RESULTS

During the study period, there were 11 patients with invasive A. actinomycetemcomitans infections, including eight patients with infective endocarditis, one with osteonecrosis and two with pneumonia and chest wall lesions. Among the patients with infective endocarditis, four had prosthetic valve replacement, four suffered from rheumatic heart disease and one had undergone surgical repair of ventricular septal defect. Lesions in the oral cavity were the probable portals of entry of the microorganism, and included carious teeth, periodontitis or radiotherapy of the ear-nose-throat field, and were noted in nine patients. Transthoracic echocardiography and/or transesophageal echocardiography were performed on the patients with probable infective endocarditis but growth was demonstrated in only four of these patients. Blood culture yielded A. actinomycetemcomitans after prolonged incubation. Three isolates were resistant to penicillin and two of these were also resistant to ampicillin.

CONCLUSION

The diagnosis of invasive A. actinomycetemcomitans infection was delayed due to the indolent clinical course, non-specific presentation and slow growth of the organism. Antibiotic therapy using amoxicillin/clavulanic acid, ampicillin, ampicillin/sulbactam, ceftriaxone, clindamycin, cefotaxime, or levofloxacin was successful in all patients. None of the patients demonstrated recurrence of infection 2-36 months following treatment.

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.

Reclassification of Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Haemophilus paraphrophilus and Haemophilus segnis as Aggregatibacter actinomycetemcomitans gen. nov., comb. nov., Aggregatibacter aphrophilus comb. nov. and Aggregatibacter segnis comb. nov., and emended description of Aggregatibacter aphrophilus to include V factor-dependent and V factor-independent isolates

The aim of this study was to reinvestigate the relationships and the generic affiliations of the species Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Haemophilus paraphrophilus and Haemophilus segnis. The nicotinamide phosphoribosyltransferase gene (nadV) conferring V factor-independent growth was identified in Haemophilus aphrophilus. The gene encodes a polypeptide of 462 amino acids that shows 74.5 % amino acid sequence identity to the corresponding enzyme from Actinobacillus actinomycetemcomitans. Ten isolates of Haemophilus paraphrophilus all carried a nadV pseudogene. DNA from Haemophilus aphrophilus was able to transform Haemophilus paraphrophilus into the NAD-independent phenotype. The transformants carried a full-length nadV inserted in the former locus of the pseudogene. The DNA–DNA relatedness between the type strains of Haemophilus aphrophilus and Haemophilus paraphrophilus was 77 %. We conclude that the division into two species Haemophilus aphrophilus and Haemophilus paraphrophilus is not justified and that Haemophilus paraphrophilus should be considered a later heterotypic synonym of Haemophilus aphrophilus. Forty strains of Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus and Haemophilus segnis were investigated by multilocus sequence analysis. The 40 strains form a monophyletic group clearly separate from other evolutionary lineages of the family Pasteurellaceae. We propose the transfer of Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus and Haemophilus segnis to a new genus Aggregatibacter gen. nov. as Aggregatibacter actinomycetemcomitans comb. nov. (the type species; type strain ATCC 33384T=CCUG 13227T=CIP 52.106T=DSM 8324T=NCTC 9710T), Aggregatibacter aphrophilus comb. nov. (type strain ATCC 33389T=CCUG 3715T=CIP 70.73T=NCTC 5906T) and Aggregatibacter segnis comb. nov. (type strain HK316T=ATCC 33393T=CCUG 10787T=CCUG 12838T=CIP 103292T=NCTC 10977T). The species of the genus Aggregatibacter are independent of X factor and variably dependent on V factor for growth in vitro.

Detachment of Actinobacillus actinomycetemcomitans biofilm cells by an endogenous beta-hexosaminidase activity

When cultured in broth, fresh clinical isolates of the gram-negative periodontal pathogen Actinobacillus actinomycetemcomitans form tenaciously adherent biofilm colonies on surfaces such as plastic and glass. These biofilm colonies release adherent cells into the medium, and the released cells can attach to the surface of the culture vessel and form new colonies, enabling the biofilm to spread. We mutagenized A. actinomycetemcomitans clinical strain CU1000 with transposon IS903phikan and isolated a transposon insertion mutant that formed biofilm colonies which were tightly adherent to surfaces but which lacked the ability to release cells into the medium and disperse. The transposon insertion in the mutant strain mapped to a gene, designated dspB, that was predicted to encode a secreted protein homologous to the catalytic domain of the family 20 glycosyl hydrolases. A plasmid carrying a wild-type dspB gene restored the ability of biofilm colonies of the mutant strain to disperse. We expressed A. actinomycetemcomitans DspB protein engineered to contain a hexahistidine metal-binding site at its C terminus in Escherichia coli and purified the protein by using Ni affinity chromatography. Substrate specificity studies performed with monosaccharides labeled with 4-nitrophenyl groups showed that DspB hydrolyzed the 1-->4 glycosidic bond of beta-substituted N-acetylglucosamine, which is consistent with the known functions of other family 20 glycosyl hydrolases. When added to culture medium, purified DspB protein, but not heat-inactivated DspB, restored the ability of the mutant strain to release cells and disperse. DspB protein also caused the detachment of cells from preformed biofilm colonies of strain CU1000 grown attached to plastic and the disaggregation of highly autoaggregated clumps of CU1000 cells in solution. We concluded that dspB encodes a soluble beta-N-acetylglucosaminidase that causes detachment and dispersion of A. actinomycetemcomitans biofilm cells.

Biofilm growth and detachment of Actinobacillus actinomycetemcomitans

The gram-negative, oral bacterium Actinobacillus actinomycetemcomitans has been implicated as the causative agent of several forms of periodontal disease in humans. When cultured in broth, fresh clinical isolates of A. actinomycetemcomitans form tenacious biofilms on surfaces such as glass, plastic, and saliva-coated hydroxyapatite, a property that probably plays an important role in the ability of this bacterium to colonize the oral cavity and cause disease. We examined the morphology of A. actinomycetemcomitans biofilm colonies grown on glass slides and in polystyrene petri dishes by using light microscopy and scanning and transmission electron microscopy. We found that A. actinomycetemcomitans developed asymmetric, lobed biofilm colonies that displayed complex architectural features, including a layer of densely packed cells on the outside of the colony and nonaggregated cells and large, transparent cavities on the inside of the colony. Mature biofilm colonies released single cells or small clusters of cells into the medium. These released cells adhered to the surface of the culture vessel and formed new colonies, enabling the biofilm to spread. We isolated three transposon insertion mutants which produced biofilm colonies that lacked internal, nonaggregated cells and were unable to release cells into the medium. All three transposon insertions mapped to genes required for the synthesis of the O polysaccharide (O-PS) component of lipopolysaccharide. Plasmids carrying the complementary wild-type genes restored the ability of mutant strains to synthesize O-PS and release cells into the medium. Our findings suggest that A. actinomycetemcomitans biofilm growth and detachment are discrete processes and that biofilm cell detachment evidently involves the formation of nonaggregated cells inside the biofilm colony that are destined for release from the colony.

Sequence diversity in the major fimbrial subunit gene (flp-1) of Actinobacillus actinomycetemcomitans

Cells of the periodontal pathogen Actinobacillus actinomycetemcomitans exhibit tight adherence to surfaces such as glass, plastic and hydroxyapatite, a property that probably plays an important role in the ability of this bacterium to colonize teeth and other surfaces. Tight adherence is mediated by long fibrils of bundled pili (fimbriae) that form on the surface of the cell. The flp-1 gene encodes the major pilin protein component of A. actinomycetemcomitans fimbriae. In this study we compared flp-1 DNA sequences from 43 strains of A. actinomycetemcomitans isolated in Europe, Japan and the United States and identified seven distinct flp-1 allelic classes. DNA and predicted protein sequences were almost completely conserved within each flp-1 class but were highly divergent between classes. Most amino acid substitutions occurred in the C-terminus of the pilin protein, a region that has been shown to be important for the bundling and adhesive properties of the pili. flp-1 classes correlated with serotypes and 16S rRNA genotypes in most strains. At least five strains showed evidence of horizontal transfer of flp-1 between strains of different serotypes and 16S rRNA genotypes. Four of the seven flp-1 classes were present in geographically diverse isolates. Strains representing all seven flp-1 classes, but not a strain carrying a transposon insertion in flp-1, bound avidly to polystyrene in an in vitro adherence assay. Strains representing six of the seven flp-1 classes were isolated from localized juvenile periodontitis patients, suggesting that phylogenetically diverse strains carry pathogenic potential. Our findings provide a framework for future biochemical, immunological and genetic studies of A. actinomycetemcomitans fimbriae.

Biofilm dispersal of Neisseria subflava and other phylogenetically diverse oral bacteria

Polystyrene petri dishes containing liquid medium were inoculated with single-cell suspensions of a fresh clinical isolate of Neisseria subflava and were incubated under conditions of low vibration. N. subflava colonies grew firmly attached to the surface of the dish, while the broth remained clear. Growing colonies released cells into the medium, resulting in the appearance of 10(2) to 10(4) small satellite colonies attached to the surface of the dish in an area adjacent to each mature colony after 24 h. Satellite colonies grew in patterns of streamers shaped like jets and flares emanating from mature colonies and pointing toward the center of the dish. This dispersal pattern evidently resulted from the surface translocation of detached biofilm cells by buoyancy-driven convection currents that were generated due to slight temperature gradients in the medium. Streamers of satellite colonies ranged from 2 to >40 mm in length. Satellite colonies in very long streamers were relatively uniform in size regardless of their distance from the mature colony, suggesting that mature colonies released single cells or small clusters of cells into the medium and that the detachment, surface translocation, and subsequent surface reattachment of released cells were a transitory process. Incubation of N. subflava single cells in a perfused biofilm fermentor resulted in a large spike of the number of CFU in the perfusate after 9.5 h of growth, consistent with a rapid release of cells into the medium. Biofilm colonies of several other phylogenetically diverse oral bacteria, including Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Streptococcus mitis, and a prevalent but previously uncultured oral Streptococcus sp., exhibited similar temperature-dependent dispersal patterns in broth culture. This in vitro spreading phenotype could be a useful tool for studying biofilm dispersal in these and other nonflagellated bacteria and may have physiological relevance to biofilm dispersal in the oral cavity.

Population structure and genetic diversity of Actinobacillus actinomycetemcomitans strains isolated from localized juvenile periodontitis patients

The phylogeny of 20 Actinobacillus actinomycetemcomitans strains isolated from patients with localized juvenile periodontitis (LJP) was investigated by using partial sequence analysis of 16S rRNA genes, arbitrarily primed PCR (AP-PCR), and four additional PCR assays that amplified polymorphic regions in the leukotoxin (lkt), cytolethal distending toxin (cdt), major fimbrial subunit (flp-1), and serotype-specific O polysaccharide gene clusters. Our analysis also included four strains isolated from healthy subjects and nine reference strains. We found that A. actinomycetemcomitans strains comprised three major phylogenetic lineages. One lineage consisted of serotype b strains, a second lineage consisted of serotype c strains, and a third lineage consisted of serotype a, d, e, and f strains. 16S rRNA sequences within each lineage were highly conserved (<1% base substitutions), whereas sequences between lineages were exceptionally divergent (1.9 to 5.0% substitutions). Two strains exhibited 16S rRNA sequences that were even more distantly related to those of the three major lineages (2.7 to 6.7% substitutions), indicating that additional minor lineages or variants exist. The distribution of 16S rRNA sequences and lkt, cdt, flp-1, and AP-PCR genotypes was consistent with a clonal population structure, with little evidence of assortative recombination between strains of different serotypes. Strains from all three major lineages were recovered from LJP patients, suggesting that phylogenetically diverse strains of A. actinomycetemcomitans carry pathogenic potential.

Beyond the specific plaque hypothesis: are highly leukotoxic strains of Actinobacillus actinomycetemcomitans a paradigm for periodontal pathogenesis?

Actinobacillus actinomycetemcomitans is a facultative anaerobe implicated in a variety of periodontal diseases. Its presence is most closely associated with localized juvenile periodontitis (LIP), although the exact role of the organism in this and other periodontal diseases is not entirely clear. While A. actinomycetemcomitans produces several different putative virulence factors, the most widely studied is the leukotoxin. The leukotoxin selectively kills polymorphonuclear leukocytes and macrophages in vitro, constituting the host's first line of defense. Interestingly, even though all strains of A. actinomycetemcomitans have the genes encoding the leukotoxin, there is variability in leukotoxin expression. Differences in the structure of the promoter region of the leukotoxin gene operon were shown to correlate directly with levels of leukotoxin production. Highly leukotoxic forms appear to exhibit increased pathogenic potential, as evidenced by recent studies that have shown a significant association between the prevalence of such strains and the occurrence of LIP in several different populations. This represents the first demonstration of an association between a particular subset of a pathogenic species and a specific periodontal disease. Early identification of A. actinomycetemcomitans by microbial and genetic assays to evaluate leukotoxicity may enhance the efficacy of preventive and/or therapeutic techniques. Future investigations should continue to evaluate pathogenic variations of additional virulence factors expressed in vivo, not only of A. actinomycetemcomitans, but also of other periodontal bacteria and infectious disease pathogens.

Structural and genetic analyses of O polysaccharide from Actinobacillus actinomycetemcomitans serotype f

The oral bacterium Actinobacillus actinomycetemcomitans is implicated as a causative agent of localized juvenile periodontitis (LJP). A. actinomycetemcomitans is classified into five serotypes (a to e) corresponding to five structurally and antigenically distinct O polysaccharide (O-PS) components of their respective lipopolysaccharide molecules. Serotype b has been reported to be the dominant serotype isolated from LJP patients. We determined the lipopolysaccharide O-PS structure from A. actinomycetemcomitans CU1000, a strain isolated from a 13-year-old African-American female with LJP which had previously been classified as serotype b. The O-PS of strain CU1000 consisted of a trisaccharide repeating unit composed of L-rhamnose and 2-acetamido-2-deoxy-D-galactose (molar ratio, 2:1) with the structure -->2)-alpha-L-Rhap-(1-3)-2-O-(beta-D-GalpNAc)-alpha-L-Rhap-(1-->* O-PS from strain CU1000 was structurally and antigenically distinct from the O-PS molecules of the five known A. actinomycetemcomitans serotypes. Strain CU1000 was mutagenized with transposon IS903phikan, and three mutants that were deficient in O-PS synthesis were isolated. All three transposon insertions mapped to a single 1-kb region on the chromosome. The DNA sequence of a 13.1-kb region surrounding these transposon insertions contained a cluster of 14 open reading frames that was homologous to gene clusters responsible for the synthesis of A. actinomycetemcomitans serotype b, c, and e O-PS antigens. The CU1000 gene cluster contained two genes that were not present in serotype-specific O-PS antigen clusters of the other five known A. actinomycetemcomitans serotypes. These data indicate that strain CU1000 should be assigned to a new A. actinomycetemcomitans serotype, designated serotype f. A PCR assay using serotype-specific PCR primers showed that 3 out of 20 LJP patients surveyed (15%) harbored A. actinomycetemcomitans strains carrying the serotype f gene cluster. The finding of an A. actinomycetemcomitans serotype showing serological cross-reactivity with anti-serotype b-specific antiserum suggests that a reevaluation of strains previously classified as serotype b may be warranted.

Infective endocarditis complicated with progressive heart failure due to beta-lactamase-producing Cardiobacterium hominis

We describe a 66-year-old woman with infective endocarditis due to Cardiobacterium hominis whose condition, complicated by severe aortic regurgitation and congestive heart failure, necessitated aortic valve replacement despite treatment with ceftriaxone followed by ciprofloxacin. The blood isolate of C. hominis produced beta-lactamase and exhibited high-level resistance to penicillin (MIC, >==256 microgram/ml) and reduced susceptibility to vancomycin (MIC, 8 microgram/ml).

Virulence factors of Actinobacillus actinomycetemcomitans

A. actinomycetemcomitans has clearly adapted well to its environs; its armamentarium of virulence factors (Table 2) ensures its survival in the oral cavity and enables it to promote disease. Factors that promote A. actinomycetemcomitans colonization and persistence in the oral cavity include adhesins, bacteriocins, invasins and antibiotic resistance. It can interact with and adhere to all components of the oral cavity (the tooth surface, other oral bacteria, epithelial cells or the extracellular matrix). The adherence is mediated by a number of distinct adhesins that are elements of the cell surface (outer membrane proteins, vesicles, fimbriae or amorphous material). A. actinomycetemcomitans enhances its chance of colonization by producing actinobacillin, an antibiotic that is active against both streptococci and Actinomyces, primary colonizers of the tooth surface. The fact that A. actinomycetemcomitans resistance to tetracyclines, a drug often used in the treatment of periodontal disease, is on the rise is an added weapon. Periodontal pathogens or their pathogenic products must be able to pass through the epithelial cell barrier in order to reach and cause destruction to underlying tissues (the gingiva, cementum, periodontal ligament and alveolar bone). A. actinomycetemcomitans is able to elicit its own uptake into epithelial cells and its spread to adjacent cells by usurping normal epithelial cell function. A. actinomycetemcomitans may utilize these remarkable mechanisms for host cell infection and migration to deeper tissues. A. actinomycetemcomitans also orchestrates its own survival by elaborating factors that interfere with the host's defense system (such as factors that kill phagocytes and impair lymphocyte activity, inhibit phagocytosis and phagocyte chemotaxis or interfere with antibody production). Once the organisms are firmly established in the gingiva, the host responds to the bacterial onslaught, especially to the bacterial lipopolysaccharide, by a marked and continual inflammatory response, which results in the destruction of the periodontal tissues. A. actinomycetemcomitans has at least three individual factors that cause bone resorption (lipopolysaccharide, proteolysis-sensitive factor and GroEL), as well as a number of activities (collagenase, fibroblast cytotoxin, etc.) that elicit detrimental effects on connective tissue and the extracellular matrix. It is of considerable interest to know that A. actinomycetemcomitans possesses so many virulence factors but unfortunate that only a few have been extensively studied. If we hope to understand and eradicate this pathogen, it is critical that in-depth investigations into the biochemistry, genetic expression, regulation and mechanisms of action of these factors be initiated.

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.

Investigation of the Actinobacillus actinomycetemcomitans genome by pulsed field gel electrophoresis

Pulsed field gel electrophoresis was used to investigate nineteen strains of Actinobacillus actinomycetemcomitans. The genome was found to contain a single chromosome whose size we estimate to be 2300 kb from the sum of restriction fragments generated with rare cutting endonucleases. We detected the presence of large plasmids with sizes ranging from 35 to 300 kb. In some strains, extrachromosomal elements constitute over 20% of the total genome. Comparison of the profiles of ApaI digests of the 19 strains showed a high degree of polymorphism with 13 different profiles, providing a new tool for epidemiological studies.

BACTERIAL ENDOCARDITIS DUE TO AN ACTINOBACILLUS

A case of subacute bacterial endocarditis due to Actinobacillus actinomycetemcomitans followed dental extraction under penicillin cover. Isolation of the organism was only achieved by incubating blood cultures in a CO(2)-enriched atmosphere. The patient was successfully treated with streptomycin.

Role of alpha beta T cells and gamma delta T cells in protective immunity to Actinobacillus actinomycetemcomitans in mutant mice by targeted gene disruption

The relative roles of alpha beta or gamma delta T cells in protection against Actinobacillus actinomycetemcomitans were analysed by using mutant mice deficient in alpha beta or gamma delta T cell receptor (TCR). The dose of A. actinomycetemcomitans producing lethality for the TCR-alpha deficient mice was 25% of that for control C57BL/6 mice, while that of TCR-delta deficient mice was similar to that of C57BL/6 mice. Reverse transcription (RT)-PCR revealed that gamma delta T cells from the A. actinomycetemcomitans-infected alpha beta TCR deficient mice expressed significant levels of interferon (IFN)-gamma, interleukin (IL)-5 and IL-6 mRNA, whereas alpha beta T cells from A. actinomycetemcomitans-infected gamma delta TCR deficient mice exhibited significant levels of IFN-gamma and IL-2 mRNA. Delayed-type hypersensitivity (DTH) reactions against heat shock protein (HSP) 60 were prominently observed in A. actinomycetemcomitans-infected TCR-delta mutant and C57BL/6 mice, but were absent in TCR-alpha mutant mice, suggesting that the DTH response is exclusively dependent on HSP60-specific alpha beta T cells producing IFN-gamma and IL-2 mRNA. It was found that all the mice used exhibited similar levels of serum IgG and IgM responses against A. actinomycetemcomitans-specific antigens (whole cells and HSP60), suggesting that alpha beta as well as gamma delta T cells participate in the serum immune responses. In addition, the humoral antibody responses displayed in the TCR-alpha deficient mice implies resistance to A. actinomycetemcomitans infection. Thus, the resistance to A. actinomycetemcomitans infection may be ascribed mainly to alpha beta T cells, while gamma delta T cells can partially compensate for the alpha beta T cell defect.

Fastidious gram-negative bacteria: meeting the diagnostic challenge with nucleic acid analysis

The extended panorama of fastidious Gram-negative bacteria (FGNB) as opportunistic etiological agents of infectious diseases in immunocompromised patients is largely due to improved medical expertise and technology. The heightened awareness of infectious diseases due to FGNB species mandates comprehensive classification and identification systems as a basis for rapid and reliable diagnostics. The most useful approaches are combinations of nucleic acid techniques such as hybridization, genetic transformation, amplification and base sequence analysis with selected conventional criteria. Among these approaches, the widely distributed feature of natural competence in these organisms facilitates the use of the biological method of genetic transformation as a valuable addition to the more common nucleic acid techniques. We describe the development of the taxonomy of FGNB through the last four decades, with particular emphasis on the families Neisseriaceae, Moraxellaceae, and Pasteurellaceae.

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.

Actinobacillus actinomycetemcomitans pneumonia with chest wall and subphrenic abscess

A 14-year-old girl had progressive dyspnea and right lower chest pain for about 1 1/2 months and a weight loss of 3 kg in 2 months. Chest X-ray revealed right pleural effusion and a round infiltration over the right lower chest, initially suspected to be malignant. Image study revealed consolidation in the right middle and lower lobes with abscess-like lesions around the right lower pleura and transdiaphrenic involvement to the subphrenic region. The lesion had also invaded the intercostal muscle. The pleural abscess was obtained by fiberoptic thoracoscopy, and culture of the pus grew typical colonies of Actinobacillus actinomycetemcomitans. After the causative microorganism had been identified, cefoxitin was given for 2 weeks followed by oral amoxicillin (250 mg/6 h) for a total period of 3 months. Follow-up chest X-ray revealed resolution of the lung lesions and the patient recovered gradually without any sequelae.

Malate dehydrogenase and glucose-6-phosphate dehydrogenase, key markers for studying the genetic diversity of Actinobacillus actinomycetemcomitans

Cell-free extracts of strains belonging to the 5 serotypes of A. actinomycetemcomitans were screened for several enzymes. Enzymes representative of the pentose phosphate pathway/hexose monophosphate shunt and the TCA cycle were present. Of these glucose-6-phosphate dehydrogenase (G6PDH) and malate dehydrogenase (MDH) were the most readily detected and stable. MDH and G6PDH retained more than 50% of their activities at alkaline pHs (10-11) for up to 6 h and 3 h at 25 degrees C, respectively, while at pH 6.5, 50% of their activities were lost within 2-3 h. The Km for malate oxidation catalysed by MDH was 5.8 x 10(-4) M while that for glucose-6-phosphate oxidation was 2.0 x 10(-4) M. The pH optima for MDH and G6PDH oxidation activities were 10 and 9.5, respectively. Among the 5 designated serotypes of A. actinomycetemcomitans three groups were delineated by multilocus enzyme electrophoresis using MDH and G6PDH.

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.

Identification of Actinobacillus actinomycetemcomitans by leukotoxin gene-specific hybridization and polymerase chain reaction assays

Eleven strains of Actinobacillus actinomycetemcomitans isolated from cases of systemic infections, local abscesses, and periodontitis were identified by genetic assays using the leukotoxin gene as the target. We have developed a polymerase chain reaction (PCR) assay, based on the leukotoxin structural gene of this pathogen, which clearly identified all tested strains of A. actinomycetemcomitans and separated them from the closely related Haemophilus aphrophilus as well as other bacterial species. Furthermore, DNA-DNA hybridization was performed with the cloned partial leukotoxin structural gene (lktA) as a probe, which again clearly distinguished A. actinomycetemcomitans from H. aphrophilus, parts of the normal oral flora, and species harboring RTX (repeats in toxin) family-related cytotoxins. The PCR fragment amplified from the leukotoxin structural gene gave results similar to those given by the cloned leukotoxin gene when used as a probe in hybridization experiments. The hybridization and PCR assays described here are fundamental improvements for the identification of A. actinomycetemcomitans.

Multivariate chemosystematics demonstrate two groups of Actinobacillus actinomycetemcomitans strains

Chemical analysis by us has indicated that Actinobacillus actinomycetemcomitans is not a homogeneous species. The present study used chemometric methods and a multitude of chemical characters to examine this further. Strains were characterized by cell sugar and fatty acid contents, lysis kinetics during EDTA and EDTA plus lysozyme exposure, methylene blue reduction, and API ZYM enzymatic assessment of whole cells and outer membrane vesicles/fragments. In total, 41 quantitative variables were analyzed from each of 9 strains and treated with principal component analysis and soft independent modeling of class analogy. These methods divided A. actinomycetemcomitans into 2 strain groups. One group contained ATCC 33384, ATCC 29522, FDC 2112 and FDC 2043; the other comprised ATCC 29524, ATCC 29523, FDC 2097, FDC 511 and FDC Y4. With an F-test, the groups (classes) of A. actinomycetemcomitans strains could be distinguished at 95% confidence limits. Both groups were distinct from members of the genera Haemophilus and Pasteurella (Haemophilus aphrophilus, Haemophilus paraphrophilus, Haemophilus influenzae, Pasteurella multocida and Pasteurella haemolytica).

Genetic relationship of strains of Haemophilus aphrophilus, H. paraphrophilus, and Actinobacillus actinomycetemcomitans studied by ribotyping

Strains of H. aphrophilus, H. paraphrophilus, and A. actinomycetemcomitans are phenotypically very similar. Ribotyping of 24 strains of H. aphrophilus, 22 strains of H. paraphrophilus, 8 strains of A. actinomycetemcomitans, and one strain each of the species Pasteurella aerogenes, H. parahaemolyticus, and the genus Capnocytophaga was studied using a non-radioactive digoxigenin labelled probe based on E. coli 16S- and 23S-ribosomal RNA. Restriction fragments were generated using restriction enzyme EcoRI. The ribotypes were analysed by a numerical approach using UPGMA clustering. Two major clusters were seen: One contained all A. actinomycetemcomitans strains, the other all H. aprophilus and all except one H. paraphrophilus strain intermingled between each other. The H. paraphrophilus strain not found in the H. aphrophilus/H. paraphrophilus cluster, the H. parahaemolyticus, P. aerogenes, and the Capnocytophaga strains clustered separately from each other and the two major clusters. The H. paraphrophilus strain with the deviating ribotype was atypical in other respects: it neither did ferment lactose nor mannose and it was isolated from a deer in contradiction to the remaining H. paraphrophilus strains, which were human isolates. This study supports the view that H. aphrophilus and H. paraphrophilus should be regarded as one species separated from A. actinomycetemcomitans.

Review of chemosystematics: multivariate approaches to oral bacteria and yeasts

There are several problems related to the classification and identification of bacterial and yeast species assigned to the genera Actinobacillus, Haemophilus, Pasteurella, Bacteroides, Prevotella, Porphyromonas, Campylobacter, Wolinella, Treponema, Candida, Torulopsis, and Saccharomyces, most of which belong to the resident oral microflora. The present review was written to demonstrate how multivariate analyses of data on cellular fatty acids, sugars, enzyme activities, and lysis kinetics during ethylenediaminetetraacetic acid (EDTA) and EDTA plus lysozyme treatment can be used to distinguish closely related species of these bacterial and yeast genera. With the exception of the Actinobacillus-Haemophilus-Pasteurella group, fatty acids were more discriminating than sugars. Enzymes from whole cells and outer membrane vesicles also contributed to taxonomic distinction. Apparently, chemosystematics, involving multivariate analyses, is a useful adjunct in oral microbial taxonomy.

Frequency and stability of mono- or poly-infection by Actinobacillus actinomycetemcomitans serotypes a, b, c, d or e

The aims of the study were to determine the prevalence of simultaneously multiple Actinobacillus actinomycetemcomitans serotypes in one individual, stability of infection by the same serotype and the occurrence of previously not described serotypes of A. actinomycetemcomitans. The serotypes of 515 clinical isolates of A. actinomycetemcomitans from 91 Finnish, Caucasian subjects, including 321 follow-up samples from 51 subjects, were determined with immunodiffusion assay. Most subjects (n = 86, 95%) were infected with one serotype only; 466 (91%) isolates from 80 subjects belonged to serotype a (25% of isolates/25 subjects), b (25% of isolates/27 subjects) or c (41% of isolates/30 subjects). Fifteen isolates from 4 subjects reacted with the antiserum raised against previously untypable clinical strain IDH 781 (serotype d) and 18 isolates from 5 subjects with the antiserum raised against strain IDH 1705 or IDH 3096 (serotype e). Sixteen (3%) isolates from 5 subjects remained untypable. The same infecting A. actinomycetemcomitans serotype(s) persisted for the 1-6 years of follow-up. In conclusion, the study indicates a rare simultaneous occurrence of multiple oral A. actinomycetemcomitans serotypes, the stability of infection by the same serotype(s) and the existence of serotypes of A. actinomycetemcomitans not previously described.

Pericarditis, pneumonia and brain abscess due to a combined Actinomyces--Actinobacillus actinomycetemcomitans infection

A patient is described in whom there developed a pulmonary infiltrate and constrictive pericarditis caused by a combined Actinomyces and Actinobacillus actinomycetemcomitans infection, presumably originating from his poor dentition. The diagnosis was only made following repeated thoracotomy. After surgery, long-term treatment with antibiotics led to complete clinical recovery. None the less, some months later he was found to have a brain abscess which resolved during a further course of antibiotics. The variable clinical picture of actinomycosis is discussed, as well as the role of other bacteria frequently associated with actinomycotic infection, in particular Actinobacillus actinomycetemcomitans. The therapeutic implications are described.

Treatment of Haemophilus aphrophilus endocarditis with ciprofloxacin

A patient with Haemophilus aphrophilus endocarditis was successfully treated with ciprofloxacin. The response to treatment with cefotaxime and netilmicin for 12 days was poor but was satisfactory to a 6 weeks' course of ciprofloxacin.

Actinobacillus actinomycetemcomitans pneumonia with chest wall involvement and rib destruction

There are four cases of Actinobacillus actinomycetemcomitans pulmonary infections reported in the English literature prior to 1990. We report a case of A actinomycetemcomitans pulmonary infection with invasion of overlying soft tissue, rib, and sternum. This manifestation has not been previously reported. The clinical manifestation is similar to that of Actinomyces israelii, which may be misinterpreted as malignancy initially. The portal of entry of A actinomycetemcomitans may be via hematogenous spread or aspiration. The diagnosis depends on culture after prolonged incubation of the involved tissue obtained by aspiration or biopsy. Elevated serum antibody is helpful for diagnosis of active infection. A actinomycetemcomitans is susceptible to most antibiotics, but is frequently resistant to penicillin, vancomycin, clindamycin, and erythromycin. Isolation of the organism and an in vitro drug sensitivity testing are important in managing the patient. Our patient recovered after a three-month regimen of penicillin.

Sensitivity of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus to oxidative killing

We examined the killing of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus by oxygen metabolites generated by the xanthine-xanthine oxidase (X-XO) system. This system generates a mixture of oxidants, including superoxide radical, hydrogen peroxide, hydroxyl radical, and possibly singlet oxygen. Differential sensitivity to the X-XO system was observed among strains of A. actinomycetemcomitans; notably, 2 catalase-deficient strains and 2 strains representative of serotypes b and c were the most susceptible. H. aphrophilus was not sensitive. The amount of oxidants produced by the X-XO system more closely correlated with killing than the ratio of oxidant production. Cytochrome c, superoxide dismutase, catalase, dimethyl sulfoxide, and desferrioxamine were used to determine the role of superoxide radical, hydrogen peroxide and hydroxyl radical in the bactericidal process. Hydrogen peroxide was the major bactericidal agent against A. actinomycetemcomitans. Superoxide anion participated in killing of A. actinomycetemcomitans to varying but lesser degrees. The intracellular generation of hydroxyl radical was implicated in the killing of several strains. We conclude that (i) strains of A. actinomycetemcomitans are differentially sensitive to the bactericidal effects of the X-XO system and (ii) of the oxidants produced by the X-XO system, hydrogen peroxide is the most bactericidal against A. actinomycetemcomitans.

Prevention of infective endocarditis: a review of the medical and dental literature

This paper is a review of what is presently known about the cause and prevention of infective endocarditis. Systemic antibiotics alone are not always enough for an effective prevention of infective endocarditis. Non-streptococcus bacteria frequently found in the periodontal pocket are now reported as causing infective endocarditis; these bacteria are not uniformly susceptible to the antibiotics recommended for prophylaxis. Animal studies indicate that periodontal disease does increase the incidence of infective endocarditis and that the number of microbes entering the blood stream may not be as important in the production of infective endocarditis as other qualities, such as the microbe's ability to adhere. Antibiotics may affect the ability of a microorganism to adhere to tissues of the heart, but this association is yet unclear and may vary with the antibiotic and species of bacteria. Reduction of inflammation of the periodontal tissues is of the utmost importance in the prevention of infective endocarditis; however, mouthrinses have a very limited effect in a periodontal pocket of more than 3 mm in depth and irrigation of a periodontal pocket may create a dangerous bacteremia. Nevertheless, in addition to systemic antibiotics, local antimicrobial agents followed by routine dental treatment and maintenance show promise as an effective means for the prevention of infective endocarditis. Future research in the prevention of infective endocarditis should include placement of antimicrobials in the periodontal pocket and systemic agents that reduce platelet adhesion. The suggestions presented in this review are only recommendations for further research and are not to be construed as a substitute for the current guidelines.

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.

Haemophilus aphrophilus isolated from blood

H. aphrophilus was isolated from 11 successively cultivated blood samples of a male (72) with a fatal atypical endocarditis. Identification and differential diagnosis from Actinobacillus (Haemophilus) actinomycetemcomitans was done on the basis of phenotypic characters of the microorganism.

Identification of Haemophilus aphrophilus and Actinobacillus actinomycetemcomitans by DNA-DNA hybridization and genetic transformation

DNA-DNA hybridization was used to identify clinical isolates as Haemophilus aphrophilus or Actinobacillus actinomycetemcomitans. Some of the isolates were naturally competent for genetic transformation and were also used as DNA recipients for identification of other isolates. The results obtained by hybridization were supported by interstrain-to-intrastrain transformation ratios. Distinction between the closely related species H. aphrophilus and A. actinomycetemcomitans was generally clear-cut by both methods. Distinction of H. aphrophilus and A. actinomycetemcomitans from type and reference strains of a diversity of species in the family Neisseriaceae and other gram-negative species was also demonstrated by both methods. This is the first description of the identification of clinical isolates of H. aphrophilus or A. actinomycetemcomitans by using them as recipients in genetic transformation. The results suggest that this is a reliable system for identification of new clinical isolates belonging to these taxonomic entities.

Molecular genetic analysis of Actinobacillus actinomycetemcomitans epidemiology

Research over the past decade has identified many of the microorganisms involved in the etiology of human periodontitis such as Actinobacillus actinomycetemcomitans. Efforts are now directed toward defining these species' role in the pathogenic process. Since microbial colonization of host tissues is a key first step in developing a bacterial infection, determining the source of the periodontal pathogens and their route of transmission is likely to be crucial in formulating preventive strategies. Recently, a technique from molecular biology, restriction endonuclease analysis, has been used to track bacterial infections. In the present study, this method was used to investigate the epidemiology of A. actinomycetemcomitans infection. One hundred twenty-four human subgingival plaque isolates of A. actinomycetemcomitans were examined including bacterial strains from the United States, Korea, and Norway as well as 15 strains from cynomolgus (Macaca fascicularis) and spider monkeys (Macaca iris) and 4 reference strains. The genomic DNA from each strain was purified, digested with each of 16 restriction endonucleases, and the DNA digests were resolved by electrophoresis. The resulting patterns of DNA fragments were compared and also correlated with the A. actinomycetemcomitans serotype determined using serotype-specific antisera in immunofluorescence. Human isolates of A. actinomycetemcomitans even from disparate geographic sources showed little diversity by restriction endonuclease analysis. Three major restriction patterns were found. Restriction pattern I was common to all 20 of the serotype a isolates, restriction pattern II was associated with 58% of the 73 serotype b isolates examined, while restriction pattern III was associated with the remaining serotype b strains and with all 15 of the serotype c strains.(ABSTRACT TRUNCATED AT 250 WORDS)