Characterization of Actinomyces species isolated from failed dental implant fixtures.

In the oral cavity, Actinomyces form a fundamental component of the indigenous microflora, being among initial colonizers in polymicrobial biofilms. However, some differences may exist between different species in terms of their attachment not only to teeth but also to biomaterials. In this study we investigated the distribution of Actinomyces in 33 dental implant fixtures explanted from 17 patients. The identification was based on comprehensive biochemical testing and gas-liquid chromatography and when needed, 16S rRNA sequencing. Actinomyces was the most prevalent bacterial genus in these failed implants, colonizing 31/33 (94%) of the fixtures. Proportions of Actinomyces growth of the total bacterial growth in the Actinomyces-positive fixtures varied from 0.01% up to 75%. A. odontolyticus was the most common Actinomyces finding, present in 26/31 (84%) Actinomyces-positive fixtures. Actinomyces naeslundii and A. viscosus were both detected in 10/31 (32%) and A. israelii in 7/31 (23%) fixtures. Other Actinomyces species, including A. georgiae, A. gerencseriae and A. graevenitzii, were detected less frequently. Our results suggest that Actinomyces species are frequent colonizers on failed implant surfaces, where A. odontolyticus was the far most prominent Actinomyces species.

Porphyromonas uenonis sp. nov., a pathogen for humans distinct from P. asaccharolytica and P. endodontalis.

Three Porphyromonas species (Porphyromonas asaccharolytica, P. endodontalis, and the novel species that is the subject of the present report, P. uenonis) are very much alike in terms of biochemical characteristics, such as enzyme profiles and cellular fatty acid contents. P. asaccharolytica is distinguished from the other two species by virtue of production of alpha-fucosidase and glyoxylic acid positivity. The novel species is difficult to differentiate from P. endodontalis phenotypically and was designated a P. endodontalis-like organism for some time. However, P. endodontalis is recovered almost exclusively from oral sources and also grows poorly on Biolog Universal Agar, both characteristics that are in contrast to those of the other two organisms. Furthermore, P. uenonis is glycerol positive in the Biolog AN Microplate system. Both P. asaccharolytica and P. uenonis are positive by 13 other tests in the Biolog system, whereas P. endodontalis is negative by all of these tests. P. asaccharolytica grew well in both solid and liquid media without supplementation with 5% horse serum, whereas the other two species grew poorly without supplementation. Sequencing of 16S rRNA revealed about 10% divergence between the novel species and P. endodontalis but less than 2% sequence difference between the novel species and P. asaccharolytica. Subsequent DNA-DNA hybridization studies documented that the novel organism was indeed distinct from P. asaccharolytica. We propose the name Porphyromonas uenonis for the novel species. We have recovered P. uenonis from four clinical infections in adults, all likely of intestinal origin, and from the feces of six children.

Evaluation of four commercial test systems for identification of actinomyces and some closely related species.

We evaluated four commercially available kits for rapid identification of Actinomyces and related species. The kits identified correctly 26 to 65% of "classical" Actinomyces strains to the species level and 13 to 49% of newly described Actinomyces strains to the genus level, thus indicating relatively poor applicability and a need to update these kits.

Orally administered targeted recombinant Beta-lactamase prevents ampicillin-induced selective pressure on the gut microbiota: a novel approach to reducing antimicrobial resistance.

Antibiotics that are excreted into the intestinal tract promote antibiotic resistance by exerting selective pressure on the gut microbiota. Using a beagle dog model, we show that an orally administered targeted recombinant beta-lactamase enzyme eliminates the portion of parenteral ampicillin that is excreted into the small intestine, preventing ampicillin-induced changes to the fecal microbiota without affecting ampicillin levels in serum. In dogs receiving ampicillin, significant disruption of the fecal microbiota and the emergence of ampicillin-resistant Escherichia coli and TEM genes were observed, whereas in dogs treated with ampicillin in combination with an oral beta-lactamase, these did not occur. These results suggest a new strategy for reducing antimicrobial resistance in humans.

Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus in systemic and nonoral infections in Finland.

The oral cavity is the ecological niche for Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus, but occasionally they cause severe nonoral infections. In this study we present 20 systemic or nonoral infections due to A. actinomycetemcomitans and H. aphrophilus, comprising all isolates of these species forwarded to and stored in Finnish reference laboratories during the years 1988-2000. The time from specimen collection to correct species identification was 9.3 days for A. actinomycetemcomitans and 10.7 days for H. aphrophilus. A. actinomycetemcomitans strains represented serotypes a, b, c, and d. Arbitrarily primed PCR distinguished four A. actinomycetemcomitans and six H. aphrophilus genotypes. Antimicrobial susceptibility testing with benzylpenicillin, amoxicillin, tetracycline, metronidazole, azithromycin, and trovafloxacin showed generally good activities against the present strains, and the susceptibility patterns closely resembled those of oral strains. The prolonged time to recover and identify A. actinomycetemcomitans and H. aphrophilus from systemic and nonoral infections may delay the correct diagnosis of the patient, but the good antimicrobial efficacies of antimicrobial agents against these pathogens give a good prognosis for the patients and advance the treatment of severe infections caused by these fastidious organisms of oral origin.

Reclassification of Bacteroides putredinis (Weinberg et al., 1937) in a new genus Alistipes gen. nov., as Alistipes putredinis comb. nov., and description of Alistipes finegoldii sp. nov., from human sources.

During studies on the bacteriology of appendicitis in children, we often isolated from inflamed and non-inflamed tissue samples, an unusual bile-resistant pigment-producing strictly anaerobic gram-negative rod. Phenotypically this organism resembles members of Bacteroides fragilis group of species, as it is resistant to bile and exhibits a special-potency-disk pattern (resistance to vancomycin, kanamycin and colistin) typical for the B. fragilis group. However, the production of brown pigment on media containing haemolysed blood and a cellular fatty acid composition dominated by iso-C15:0, suggests that the organism most closely resembles species of the genus Porphyromonas. However, the unidentified organism differs from porphyromonads by being bile-resistant and by not producing butyrate as a metabolic end-product. Comparative 16S ribosomal RNA gene sequencing studies show the unidentified organism represents a distinct sub-line, associated with but distinct from, the miss-classified species Bacteroides putredinis. The clustering of the unidentified bacterium with Bacteroides putredinis was statistically significant, but they displayed > 4% sequence divergence with each other. Chromosomal DNA-DNA pairing studies further confirmed the separateness of the unidentified bacterium and Bacteroides putredinis. Based on phenotypic and phylogenetic considerations, it is proposed that Bacteroides putredinis and the unidentified bacterium from human sources be classified in a new genus Alistipes, as Alistipes putredinis comb. nov. and Alistipes finegoldii sp. nov., respectively. The type strain of Alistipes finegoldii is CCUG 46020(T) (= AHN243(T)).

Nasopharyngeal carriage of anaerobes during health and acute otitis media by two years of age.

The nasopharyngeal acquisition of anaerobic bacteria was longitudinally examined among a homogeneous group of Caucasian infants by 2 years of age. Nasopharyngeal swab (NP) samples were collected at scheduled healthy visits at 2, 6, 12, 18, and 24 months of age, and nasopharyngeal aspirates (NPA) during every visit for acute otitis media (AOM). The infants were divided into 4 groups according to the number (0, 1, 2-3, and > 3) of AOM episodes experienced by 2 years of age. At 2 years, the cumulative carriage rates of anaerobic species in these infant groups were 29%, 62%, 89%, and 89%, respectively. Anaerobic species were found in 15/220 (6.8%) of the NP samples and in 34/71 (47.9%) of the NPA samples. Our present results indicate that anaerobic species do not belong to the indigenous nasopharyngeal microflora but only transiently colonize the nasopharynx during AOM.

Susceptibilities of different Actinobacillus actinomycetemcomitans strains to lactoperoxidase-iodide-hydrogen peroxide combination and different antibiotics.

Actinobacillus actinomycetemcomitans has an important aetiological role in localized juvenile periodontitis and in progressive periodontitis in adults. A. actinomycetemcomitans is found mainly in periodontal pockets but also in whole saliva, a potential transmission medium. It is sensitive to peroxidase-halide systems, but the differences between periodontitis associated clinical isolates and type strains are unclear. The sensitivities of these 2 strain groups to lactoperoxidase (LP)-iodide (I(-))-hydrogen peroxide (H(2)O(2)) combinations were investigated, and the sensitivities were compared with the susceptibilities to four antibiotics. There was great variation between the sensitivities of different strains, but the 2 strain groups responded similarly. The LP (75 microg)-I(-) (100 nmol)-H(2)O(2) (1000 nmol) combination produced a similar degree of inhibition as 2 microg ampicillin. The LP-I(-) system might be a potential antimicrobial agent against A. actinomycetemcomitans transmission via saliva.

Fluoroquinolone resistance in Campylobacter jejuni isolates in travelers returning to Finland: association of ciprofloxacin resistance to travel destination.

Ciprofloxacin resistance was analyzed in 354 Campylobacter jejuni isolates collected during two study periods (1995-1997 and 1998-2000) from travelers returning to Finland. The increase in resistance between the two periods was significant among all isolates (40% vs. 60%; p<0.01), as well as among those from Asia alone (45% vs. 72%; p<0.01).

Emergence of penicillin resistance among Fusobacterium nucleatum populations of commensal oral flora during early childhood.

Penicillin resistance due to beta-lactamase production is surprisingly common among oral bacteria in childhood. Fusobacterium nucleatum, a Gram-negative anaerobic bacillus, is a member of the developing oral commensal flora. As part of the investigation on the emergence of oral bacterial resistance, the aim of the present study was to examine longitudinally the penicillin resistance among salivary F. nucleatum populations as related to age, day care attendance and sibling history, and exposure to antimicrobial agents. Altogether 1492 F. nucleatum isolates from saliva of 44 healthy infants followed at a study clinic at 2, 6, 12, 18 and 24 months of age were tested for beta-lactamase production. Furthermore, the 276 beta-lactamase-positive isolates were examined for their in vitro susceptibility to penicillin G by the NCCLS-approved agar dilution method. Statistical analysis of the associations between penicillin-resistant isolates and infants' age, day care attendance, number of siblings and their ear infections, and exposure to antimicrobial agents was performed by SPSS Windows Version 10. The prevalence of infants harbouring beta-lactamase-producing F. nucleatum strains increased from 2% to 49% during the follow-up time. In nearly all cases beta-lactamase-producing F. nucleatum isolates were found simultaneously with beta-lactamase-negative isolates. Most beta-lactamase-producing isolates (80%) showed an MIC of > or =8 mg/L. In conclusion, the prevalence of infants harbouring penicillin-resistant F. nucleatum due to beta-lactamase production increased with age and usage of antimicrobial agents during the first year of life.

A newborn with domestically acquired legionnaires disease confirmed by molecular typing.

Legionella pneumophila serogroup 6 was recovered from a bronchoalveolar lavage specimen from a 1-week-old, full-term newborn with pneumonia, as well as from water samples from the maternity hospital and the newborn's home (an apartment). Amplified fragment-length polymorphism typing revealed that the strains isolated from the newborn and her home were indistinguishable from each other but were clearly different from the hospital and control strains. To our knowledge, this is the first report of domestic acquisition of legionnaires disease in a newborn to have been confirmed by molecular typing.

Recent taxonomic changes and terminology update of clinically significant anaerobic gram-negative bacteria (excluding spirochetes).

Because of access to 16S rDNA sequencing, changes in the taxonomy and nomenclature of anaerobic gram-negative bacteria have occurred lately. New genera and species have been described, and existing taxa have been reclassified. The present article compiles a list of clinically relevant anaerobes and provides synonyms as well as the old nomenclature used for these bacteria. Although names and classifications of anaerobic bacteria are changing quickly, it is important to keep track of new bacterial names to work toward better description and recognition of bacterium-disease associations.

gyrA polymorphism in Campylobacter jejuni: detection of gyrA mutations in 162 C. jejuni isolates by single-strand conformation polymorphism and DNA sequencing.

Mutations in the quinolone resistance-determining region of the gyrA gene from 138 ciprofloxacin-resistant (MIC, > or =4 microg/ml) and 24 ciprofloxacin-susceptible (MIC, < or =1 microg/ml) clinical Campylobacter jejuni isolates were subjected to single-strand conformation polymorphism analysis and sequencing. All of the isolates could be assigned to three genotypic clusters based on silent mutations. All resistant isolates had a point mutation at codon 86.

Characterisation of Eubacterium-like strains isolated from oral infections.

The genus Eubacterium currently includes a heterogeneous group of gram-positive, non-spore-forming anaerobic bacilli, many of which are slow growing, fastidious and generally unreactive in biochemical tests. As a consequence, cultivation and identification of isolates are difficult and the taxonomy of the group remains indifferent. In this study, 105 isolates from odontogenic infections, infections associated with dental implants or saliva from healthy subjects and provisionally assigned to the genus Eubacterium were subjected to phenotypic and genotypic analysis. Ninety-one of the isolates were identified as belonging to one of 14 previously described species: Atopobium parvulum (5 isolates), A. rimae (29), Bulleidia extructa (2), Cryptobacterium curtum (1), Dialister pneumosintes (1), Eubacterium saburreum (2), E. sulci (8), E. yurii subsp. yurii (1), Filifactor alocis (3), Lactobacillus uli (1), Mogibacterium timidum (13), M. vescum (6), Pseudoramibacter alactolyticus (6) and Slackia exigua (13). The remaining 14 isolates did not correspond to existing species. This study confirms the diversity of organisms provisionally assigned to the genus Eubacterium by conventional identification methods. This group of organisms is frequently isolated from oral infections but their role in the aetiology of these conditions has yet to be determined.