Bacteremia after plate removal and tooth extraction.

Our aim was to investigate the occurrence of bacteremia associated with removal of a semirigid osteosynthesis plate and an adjacent third molar. Ten patients with fixed mandibular angle fracture were bacteriologically sampled from the second molar's distal gingival pocket, from the third molar's extraction socket and from the osteosynthesis plate. Blood samples from the ante-cubital vein were taken 10 times until 30 min postoperatively. Established culture, isolation and identification methods for the bacterial species were used. Bacteremia was detected in 60% of the subjects, most frequently 1.5 min after removal of the plate (20%) and 1.5 and 5 min after extraction of the tooth (20%), but also 10 min (10%) and 30 min (10%) postoperatively. 13 different bacterial species or groups were isolated, mean 2.5 +/- 1.9 per bacteremia-positive subject. The majority (85%) were anaerobes with Actinomyces, Campylobacter and Lactobacillus species predominating. In all the blood culture-positive cases the corresponding species was also recovered from one or more of the oral samples. These results show that oral surgical procedures are associated with a high frequency of longstanding anaerobic bacteremia, which could be harmful in patients at risk.

Bacteremia following surgical dental extraction with an emphasis on anaerobic strains.

Our aim was to investigate bacteremia caused by surgical extraction of partly erupted mandibular third molars. From 16 young adults, bacterial samples were taken from the third-molar pericoronal pocket and post-operatively from the extraction socket, and blood samples were drawn from the ante-cubital vein up to 30 min after surgery. Of the subjects, 88% had detectable bacteremia-50% 1 min after the incision, 44% immediately after extraction. The respective percentages at 10, 15, and 30 min were 44%, 25%, and 13%. Blood cultures contained 31 species (74% anaerobes), with 3.9 +/- 2.6 species isolated per subject. Most prevalent were the anaerobes Prevotella, Eubacterium, and Peptostreptococcus sp. and the aerobes viridans-group streptococci and Streptococcus milleri group. Any species found in the blood was also isolated from the mouth, from 93% of the pericoronal pockets and from 43% of the extraction sockets. Surgical dental extraction clearly causes bacteremia of a high frequency and lasting longer than thus far assumed.

Age-related frequency of penicillin resistance of oral Veillonella.

Veillonella spp. are early colonizing inhabitants in the mouth. As part of studies on penicillin resistance among oral indigenous anaerobic microbiota in childhood, the aim of the present longitudinal study was to examine the emergence of resistant strains in Veillonella populations. Altogether 305 Veillonella isolates from saliva of 49 healthy infants followed from 2 to 24 months of age were examined for their in vitro susceptibility to penicillin G and, further, 20 penicillin-resistant isolates representing 5 MIC categories to ampicillin, amoxicillin, amoxicillin/clavulanate, cefoxitin, and beta-lactamase production. In infants positive for oral Veillonella, the recovery rate of penicillin-resistant (MIC >/=2 microg/ml) strains increased with age up to 68%, however, most infants simultaneously harbored penicillin-susceptible strains. During the follow-up, the MIC(50) increased from 0.5 microg/ml to 2 microg/ml. In addition to penicillin G, 8/20 strains also showed reduced susceptibility to ampicillin and/or amoxicillin but none produced beta-lactamase. Our study suggests other mechanisms than enzymatic degradation of beta-lactam ring for resistance of oral Veillonella to penicillin.

Establishment of streptococci in the upper respiratory tract: longitudinal changes in the mouth and nasopharynx up to 2 years of age.

As part of a series of longitudinal studies on the development of the indigenous microflora of the upper respiratory tract, the establishment of streptococci in the oral cavity and nasopharynx and IgA1 protease production by the early streptococcal flora was examined in 50 healthy Caucasian infants at the ages of 2, 6, 12, 18 and 24 months. In the oral cavity, streptococci were found in all infants on every sampling occasion, Streptococcus mitis biovar 1 being the main finding in each age group. S. salivarius and S. mitis biovar 2 reached their highest prevalence during the first year of life, whereas the prevalence of S. oralis and S. sanguis showed no significant increase before 12 months of age. Salivary streptococci mainly consisted of the above-mentioned species during the follow-up period. In contrast to the oral cavity, no stable colonisation pattern was observed for viridans streptococci in the nasopharynx. S. mitis biovar 1 and S. pneumoniae, a traditional respiratory pathogen, were the principal streptococcal species among nasopharyngeal isolates. IgA1 protease production by early streptococci was common in infancy. Among the oral streptococcal microflora, S. mitis biovar 1 (especially during the first year of life) and S. oralis and S. sanguis constituted the main species responsible for this enzyme activity. In the nasopharynx, IgA1 protease was produced by S. mitis biovar 1, S. oralis and S. pneumoniae. In conclusion, streptococcal colonisation differs in these two close habitats in the upper respiratory tract.

Bacteriologic findings associated with chronic bacterial maxillary sinusitis in adults.

An open-label, multicenter study was performed to assess bacteriologic findings associated with chronic bacterial maxillary sinusitis in adults. Seventy aerobic (52.2%) and 64 anaerobic (47.8%) pathogens were recovered from clinically evaluable patients at baseline (before therapy). The most commonly isolated anaerobes were Prevotella species (31.1%), anaerobic streptococci (21.9%), and Fusobacterium species (15.6%). The aerobes most frequently recovered included Streptococcus species (21.4%), Haemophilus influenzae (15.7%), Pseudomonas aeruginosa (15.7%), and Staphylococcus aureus and Moraxella catarrhalis (10.0% each). Recurrences of signs or symptoms of bacterial maxillary sinusitis associated with anaerobes were twice as frequent as were those associated with aerobes when counts of anaerobes were > or =10(3) cfu/mL. A pathogenic role for Granulicatella species in cases of chronic sinusitis was documented for the first time.

Matrilysin (matrix metalloproteinase-7) expression in human junctional epithelium.

Matrilysin is a matrix metalloproteinase expressed in exocrine and mucosal epithelium in many human tissues. Immunohistochemical staining showed that matrilysin is expressed in suprabasal cells of junctional epithelium facing the teeth and in epithelial cell rests of Malassez. No matrilysin expression was seen in the periodontal pocket tissue. In a tissue culture model mimicking junctional epithelium, matrilysin expression was also observed in suprabasal epithelial cells. Of 13 anaerobic oral bacterial species tested, F. nucleatum, F. necrophorum, P. endodontalis, and P. denticola stimulated matrilysin expression in porcine periodontal ligament epithelial cells from 2.5- to 5.7-fold, compared with untreated cells. The enzyme was localized in intracytoplasmic vesicles that also reacted with antibodies against lysosomal membrane protein h-lamp-1. The results indicate that matrilysin may play an important role in the normal physiology of junctional epithelium.

Ethanol-derived microbial production of carcinogenic acetaldehyde in achlorhydric atrophic gastritis.

BACKGROUND: Acetaldehyde is a local carcinogen in the digestive tract in humans. Atrophic gastritis leads to microbial colonization of the stomach, which could enhance microbial production of acetaldehyde from ethanol. The aim of the study was to study microbial ethanol metabolism and acetaldehyde production in the stomach of achlorhydric atrophic gastritis patients. METHODS: For the in vivo study, glucose or ethanol was infused via a nasogastric tube to the stomach of seven achlorhydric atrophic gastritis patients and five healthy controls. Gastric juice samples for ethanol and acetaldehyde determinations and microbial analysis were obtained at 30 and 60 min after the infusions. For the in vitro study, gastric juice samples from 14 atrophic gastritis patients and 16 controls were obtained during gastroscopy, whereafter the samples were incubated for 2 h with 1% ethanol at 37 degrees C and acetaldehyde was determined. RESULTS: Minor endogenous ethanol and acetaldehyde concentrations were detected after glucose infusion in the gastric juice of four atrophic gastritis patients. After ethanol infusion, the mean intragastric acetaldehyde level of the atrophic gastritis patients was 4.5-fold at 30 min and 6.5-fold at 60 min compared to controls. In vitro, the difference between the study groups was even higher, 7.6-fold. A vast selection of oral bacterial species and some Enterobacteriaceae and yeasts were presented in the gastric juice of atrophic gastritis patients. CONCLUSIONS: Microbial ethanol metabolism leads to high intragastric acetaldehyde levels after ethanol drinking in achlorhydric atrophic gastritis patients. This could be one of the factors responsible for enhanced gastric cancer risk among atrophic gastritis patients.

Characterisation of aerobic gram-negative bacteria from subgingival sites of dogs--potential bite wound pathogens.

Ninety-eight aerobic, gram-negative bacterial isolates from subgingival samples from family-owned dogs with naturally occurring periodontitis were characterised phenotypically by conventional biochemical testing, by cellular fatty acid profiling and by the use of commercial identification systems. The majority (48, 81%) of the fermentative isolates but only 18% of the non-fermenters were identified by conventional biochemical testing alone. With additional cellular fatty acid profiling, another 7 (12%) fermentative and 23 (59%) non-fermentative isolates were identified to genus or group level. Cellular fatty acid analysis was essential for the identification of most non-fermenters, many of which are difficult to identify due to a paucity of positive reactions in routine biochemical tests. Commercial identification systems were less useful and did not contribute to further identification of these problematic isolates. This study underlines the difficulties encountered in the identification of canine oral bacteria--a group of potential bite wound pathogens--and presents schemes for microbiology laboratories to characterise such isolates.

Phenotypic identification of Actinomyces and related species isolated from human sources.

Recent advancements in chemotaxonomic and molecular biology-based identification methods have clarified the taxonomy of the genus Actinomyces and have led to the recognition of several new Actinomyces and related species. Actinomyces-like gram-positive rods have increasingly been isolated from various clinical specimens. Thus, an easily accessible scheme for reliable differentiation at the species level is needed in clinical and oral microbiology laboratories, where bacterial identification is mainly based on conventional biochemical methods. In the present study we designed a two-step protocol that consists of a flowchart that describes rapid, cost-efficient tests for preliminary identification of Actinomyces and closely related species and an updated more comprehensive scheme that also uses fermentation reactions for accurate differentiation of Actinomyces and closely related species.

Differences between patients with or without the need for intensive care due to severe odontogenic infections.

PURPOSE: Despite greatly improved dental health in industrialized countries, severe odontogenic infections still occasionally lead to hospitalization. The aim of the present study was to determine whether what symptoms, signs, or laboratory parameters on hospital admission were associated with the need for treatment in the intensive care unit (ICU). PATIENTS AND METHODS: Over an 18-month period, 100 consecutive patients (59 male, 41 female) were included in the study. Twenty percent of the patients required ICU treatment because of cardiorespiratory problems or severe complications of their infection. Both ICU and non-ICU patients were examined clinically and blood samples were taken and studied in respect to several parameters associated with infection, including C-reactive protein (CRP) levels. The findings were analyzed statistically for differences between the groups. RESULTS: No particular anamnestic background variable was associated with the need for intensive care. However, a particularly high CRP level on admission was found to be associated with a more severe course of the infection. CONCLUSIONS: This study showed that determination of CRP levels may be useful in clinical decision-making in patients with severe odontogenic infections.

Acetaldehyde production and other ADH-related characteristics of aerobic bacteria isolated from hypochlorhydric human stomach.

BACKGROUND: Acetaldehyde is a known local carcinogen in the digestive tract in humans. Bacterial overgrowth in the hypochlorhydric stomach enhances production of acetaldehyde from ethanol in vivo after alcohol ingestion. Therefore, microbially produced acetaldehyde may be a potential risk factor for alcohol-related gastric and cardiac cancers. This study was aimed to investigate which bacterial species and/or groups are responsible for acetaldehyde formation in the hypochlorhydric human stomach and to characterize their alcohol dehydrogenase (ADH) enzymes. METHODS: After 7 days of treatment with 30 mg of lansoprazole twice a day, a gastroscopy was performed on eight volunteers to obtain hypochlorhydric gastric juice. Samples were cultured and bacteria were isolated and identified; thereafter, their acetaldehyde production capacity was measured gas chromatographically by incubating intact bacterial suspensions with ethanol at 37 degrees C. Cytosolic ADH activities, Km values, and protein concentration were determined spectrophotometrically. RESULTS: Acetaldehyde production of the isolated bacterial strains (n = 51) varied from less than 1 to 13,690 nmol of acetaldehyde/10(9) colony-forming units/hr. ADH activity of the strains that produced more than 100 nmol of acetaldehyde/10(9) colony-forming units/hr (n = 23) varied from 3.9 to 1253 nmol of nicotinamide adenine dinucleotide per minute per milligram of protein, and Km values for ethanol ranged from 0.65 to 116 mM and from 0.5 to 3.1 M (high Km). There was a statistically significant correlation (r = 0.64, p < 0.001) between ADH activity and acetaldehyde production from ethanol in the tested strains. The most potent acetaldehyde producers were Neisseria and Rothia species and Streptococcus salivarius, whereas nearly all Stomatococcus, Staphylococcus, and other Streptococcus species had a very low capacity to produce acetaldehyde. CONCLUSIONS: This study demonstrated that certain bacterial species or groups that originate from the oral cavity are responsible for the bulk of acetaldehyde production in the hypochlorhydric stomach. These findings provide new information with the respect to the local production of carcinogenic acetaldehyde in the upper digestive tract of achlorhydric human subjects.

Bacteriology of histopathologically defined appendicitis in children.

BACKGROUND: Acute appendicitis is the most common surgical emergency in childhood. However, the pathogenesis and detailed microbiology are obscure. OBJECTIVE: To determine in detail the bacterial etiology of appendicitis in children in relation to the histologic tissue pathology. STUDY DESIGN: Tissue samples obtained at surgery from 41 children with suspected acute appendicitis were examined histologically and by culture for aerobic and anaerobic bacteria. The patients were analyzed according to histopathologic and clinical findings. RESULTS: Aerobic and anaerobic species were isolated from 40 of 41 (98%) samples; on average, 14.1 isolates per specimen (10.4 anaerobes and 3.7 aerobes). Specimens from patients with gangrenous appendices yielded significantly higher numbers of anaerobic isolates per specimen than did specimens from patients with healthy appendices (11.7 vs. 7.7; P < 0.01). Bacteria belonging to the Bacteroides fragilis group were the most frequently isolated anaerobic microorganisms (95%). Other organisms frequently isolated in all histology groups were Peptostreptococcus micros (66%), Bilophila wadsworthia (63%), Fusobacterium nucleatum (44%), Eggerthella lenta (44%) and a hitherto undescribed bile-resistant, pigment-producing Gram-negative rod (41%). Of the aerobes Escherichia coli (88%) and Streptococcus anginosus group (former Streptococcus "milleri" group) organisms (61%) were the most frequent findings. CONCLUSIONS: The shift from histologically normal toward gangrenous appendices was clearly associated with markedly elevated anaerobic bacterial counts in terms of species. The unusually high frequencies of B. wadsworthia (75%) and the hitherto undescribed bile-resistant, pigment-producing Gram-negative rod (56%) in gangrenous appendices represent unique and different findings from those reported in adults.

Hypochlorhydria induced by a proton pump inhibitor leads to intragastric microbial production of acetaldehyde from ethanol.

BACKGROUND: Acetaldehyde, produced locally in the digestive tract, has recently been shown to be carcinogenic in humans. AIM: To examine the effect of iatrogenic hypochlorhydria on intragastric acetaldehyde production from ethanol after a moderate dose of alcohol, and to relate the findings to the changes in gastric flora. METHODS: Eight male volunteers ingested ethanol 0.6 g/kg b.w. The pH, acetaldehyde level and microbial counts of the gastric juice were then determined. The experiment was repeated after 7 days of lansoprazole 30 mg b.d. RESULTS: The mean (+/- S.E.M.) pH of the gastric juice was 1.3 +/- 0.06 and 6.1 +/- 0.5 (P < 0.001) before and after lansoprazole, respectively. This was associated with a marked overgrowth of gastric aerobic and anaerobic bacteria (P < 0. 001), by a 2.5-fold (P=0.003) increase in gastric juice acetaldehyde level after ethanol ingestion, and with a positive correlation (r=0. 90, P < 0.001) between gastric juice acetaldehyde concentration and the count of aerobic bacteria. CONCLUSIONS: Treatment with proton pump inhibitors leads to hypochlorhydria, which associates with intragastric overgrowth of aerobic bacteria and microbially-mediated acetaldehyde production from ethanol. Since acetaldehyde is a local carcinogen in the concentrations found in this study, long-term use of gastric acid secretory inhibitors is a potential risk-factor for gastric and cardiac cancers.

Acetaldehyde production and metabolism by human indigenous and probiotic Lactobacillus and Bifidobacterium strains.

Many human gastrointestinal facultative anaerobic and aerobic bacteria possess alcohol dehydrogenase (ADH) activity and are therefore capable of oxidizing ethanol to acetaldehyde. We examined whether human gastrointestinal lactobacilli (three strains), bifidobacteria (five strains) and probiotic Lactobacillus GG ATCC 53103 are also able to metabolize ethanol and acetaldehyde in vitro. Acetaldehyde production by bacterial suspensions was determined by gas chromatography after a 1-h incubation with 22 mM ethanol. To determine the acetaldehyde consumption, the suspensions were incubated with 50 microM or 500 microM acetaldehyde as well as with 500 microM acetaldehyde and 22 mM ethanol, i.e. under conditions resembling those in the human colon after alcohol intake. The influence of growth media and bacterial concentration on the ability of lactobacilli to metabolize acetaldehyde and to produce acetate from acetaldehyde were determined. ADH and aldehyde dehydrogenase (ALDH) activities were determined spectrophotometrically. Neither measurable ADH nor ALDH activities were found in aerobically grown Lactobacillus GG ATCC 53103 and Lactobacillus acidophilus ATCC 4356 strains. All the lactobacilli and bifidobacteria strains revealed a very limited capacity to oxidize ethanol to acetaldehyde in vitro. Lactobacillus GG ATCC 53103 had the highest acetaldehyde-metabolizing capacity, which increased significantly with increasing bacterial concentrations. This was associated with a marked production of acetate from acetaldehyde. The type of the growth media had no effect on acetaldehyde consumption. Addition of ethanol to the incubation media diminished the acetaldehyde-metabolizing capacity of all strains. However, in the presence of ethanol, Lactobacillus GG ATCC 53103 still demonstrated the highest capacity for acetaldehyde metabolism of all strains. These data suggest a beneficial impact of Lactobacillus GG ATCC 53103 on high gastrointestinal acetaldehyde levels following alcohol intake. The possible clinical implications of this finding remain to be established in in vitro studies.

Metronidazole increases intracolonic but not peripheral blood acetaldehyde in chronic ethanol-treated rats.

BACKGROUND: Metronidazole leads to the overgrowth of aerobic flora in the large intestine by reducing the number of anaerobes. According to our previous studies, this shift may increase intracolonic bacterial acetaldehyde formation if ethanol is present. Metronidazole is also reported to cause disulfiram-like effects after alcohol intake, although the mechanism behind this is obscure. Therefore, the aim was to study the effect of long-term metronidazole and alcohol treatment on intracolonic acetaldehyde levels and to explore the possible role of intestinal bacteria in the metronidazole related disulfiram-like reaction. METHODS: A total of 32 rats were divided into four groups: controls (n = 6), controls receiving metronidazole (n = 6), ethanol group (n = 10), and ethanol and metronidazole group (n = 10). All rats were pair-fed with the liquid diet for 6-weeks, whereafter blood and intracolonic acetaldehyde levels and liver and colonic mucosal alcohol (ADH) and aldehyde dehydrogenase (ALDH) activities were analyzed. RESULTS: The rats receiving ethanol and metronidazole had five times higher intracolonic acetaldehyde levels than the rats receiving only ethanol (431.4 +/- 163.5 microM vs. 84.7 +/- 14.4 microM,p = 0.0035). In contrast, blood acetaldehyde levels were equal. Cecal cultures showed the increased growth of Enterobacteriaceae in the metronidazole groups. Metronidazole had no inhibitory effect on hepatic or colonic mucosal ADH and ALDH activities. CONCLUSIONS: The increase in intracolonic acetaldehyde after metronidazole treatment is probably due to the replacement of intestinal anaerobes by ADH-containing aerobes. Unlike disulfiram, metronidazole neither inhibits liver ALDH nor increases blood acetaldehyde. Thus, our findings suggested that the mechanism behind metronidazole related disulfiram-like reaction might be located in the gut flora instead of the liver.

Oral colonization with Actinomyces species in infants by two years of age.

In early childhood, the human mouth is already colonized by actinomycetes. Due to recent taxonomic changes within the genus Actinomyces, up-to-date data are warranted on the time and succession of different Actinomyces species in the oral cavity. By using a longitudinal study design and culture techniques, we examined the age-related occurrence of Actinomyces species in saliva from 39 healthy infants at 2, 6, 12, 18, and 24 months of age. Altogether 428 Actinomyces isolates were available for this study. Identification was based on biochemical tests and gas chromatographic demonstration of metabolic end-products, and when needed, cellular fatty acid profiles were determined. The frequency of the total actinomycetal flora increased from 31% to 97% within 2 years. A. odontolyticus was the most prominent Actinomyces colonizer at all five sampling occasions. A. naeslundii was the second most common Actinomyces sp. but was not detected before the age of 1 year. As a novel observation, we found A. graevenitzii in the oral cavity. The number of A. graevenitzii isolates indicates that this species is not just occasionally present in infants' mouths. We also found A. viscosus, A. gerencseriae, A. israelii, and A. georgiae. Based on the present results, we suggest that A. odontolyticus is the main primary Actinomyces species on oral mucosal surfaces in infants up to 2 years of age.

Increased salivary acetaldehyde levels in heavy drinkers and smokers: a microbiological approach to oral cavity cancer.

The pathogenetic mechanisms behind alcohol-associated carcinogenesis in the upper digestive tract remain unclear, as alcohol is not carcinogenic. However, there is increasing evidence that a major part of the tumour-promoting action of alcohol might be mediated via its first, toxic and carcinogenic metabolite acetaldehyde. Acetaldehyde is produced from ethanol in the epithelia by mucosal alcohol dehydrogenases, but much higher levels derive from microbial oxidation of ethanol by the oral microflora. In this study we investigated factors that might alter the composition and quantities of the oral microflora and, consequently, influence microbial acetaldehyde production. Information about dental health, smoking habits, alcohol consumption and other factors was obtained by a questionnaire from 326 volunteers with varying social backgrounds and health status, e.g. oral cavity malignancy. Paraffin-induced saliva was collected and the microbial production of acetaldehyde from ethanol was measured. Smoking and heavy drinking were the strongest factors increasing microbial acetaldehyde production. Whether poor dental status may alter local acetaldehyde production from ethanol remained unanswered. Bacterial analysis revealed that mainly gram-positive aerobic bacteria and yeasts were associated with higher acetaldehyde production. Increased local microbial salivary acetaldehyde production due to ethanol among smokers and heavy drinkers could be a biological explanation for the observed synergistic carcinogenic action of alcohol and smoking on upper gastrointestinal tract cancer. It offers a new microbiological approach to ethanol-associated carcinogenesis at these anatomic sites.

Age, dental infections, and coronary heart disease.

Epidemiological and intervention studies have suggested that infections are risk factors for coronary heart disease (CHD). Dental infections have appeared as cardiovascular risk factors in cross-sectional and in follow-up studies, and the association has been independent of the "classic" coronary risk factors. This case-control study aimed at detailed assessment of the dental pathology found in various CHD categories (including elderly patients). Altogether, 85 patients with proven coronary heart disease and 53 random controls, matched for sex, age, geographic area, and socio-economic status, were compared with regard to dental status, assessed blindly with four separate scores, and to the "classic" coronary risk factors (seven of the controls had CHD, and they were not included in the analyses). The dental indices were higher among CHD patients than in the controls, but, contrary to previous studies, the differences were not significant (between the CHD patients and their matched controls or among the different CHD categories). This result could not be explained by potential confounding factors. The participants in the present study were older and had more often undergone recent dental treatment in comparison with subjects in our earlier studies. Age correlated with the severity of dental infections only in the random controls but not in the coronary patients who, although young, already had high dental scores. We believe that the higher age of the participants in the present study is the most likely reason for the results. Other possible explanations include an age-related selection bias among older CHD patients, and the fact that those participating in studies like this may have better general health and thus also less severe dental infections. Thus, the role of dental infections as a coronary risk factor varies according to the characteristics of the population studied.

Altered antigenicity is seen in the lipopolysaccharide profile of non-serotypeable Actinobacillus actinomycetemcomitans strains.

Non-serotypeable Actinobacillus actinomycetemcomitans strains may be derived from the serotypeable ones. In the present study, we compared the outer membrane proteins (OMPs) and lipopolysaccharides (LPSs) of serotypeable and non-serotypeable A. actinomycetemcomitans strains (n=24) of the same genotype in the same subject (n=6) to find out if alterations on the cell-surface contribute to the non-serotypeability. Serotypeable and non-serotypeable A. actinomycetemcomitans strains showed great similarity in the OMP patterns both within and between subjects. Using serotype-specific antisera, clear immunoblotting LPS profiles in the O-antigenic region were seen in serotype b and c strains but not in non-serotypeable strains from the same subjects. The results suggest that changes in LPS lead to the altered antigenicity of non-serotypeable A. actinomycetemcomitans strains.

Heterogeneity of Actinobacillus actinomycetemcomitans strains in various human infections and relationships between serotype, genotype, and antimicrobial susceptibility.

Actinobacillus actinomycetemcomitans, an oral pathogen, only occasionally causes nonoral infections. In this study 52 A. actinomycetemcomitans strains from 51 subjects with nonoral infections were serotyped and genotyped by arbitrarily primed PCR (AP-PCR) to determine whether a certain clone(s) is specifically associated with nonoral infections or particular in vitro antimicrobial susceptibility patterns. The promoter structure of leukotoxin genes was additionally investigated to find the deletion characteristic of highly leukotoxic A. actinomycetemcomitans strains. The nonoral A. actinomycetemcomitans strains included all five known serotypes and nonserotypeable strains, the most common serotypes being b (40%) and c (31%). AP-PCR distinguished 10 different genotypes. A. actinomycetemcomitans serotype b strains were more frequently found in blood samples of patients with bacteremia or endocarditis than in patients with focal infections. One AP-PCR genotype was significantly more frequently found among strains originating in focal infections than in blood samples. Resistance to benzylpenicillin was significantly more frequent among A. actinomycetemcomitans serotype b strains than among strains of other serotypes. No differences in the leukotoxin gene promoter region or benzylpenicillin resistance between nonoral and oral A. actinomycetemcomitans strains were observed. Nonoral A. actinomycetemcomitans strains showed great similarity to the oral strains, confirming that the oral cavity is the likely source of nonoral A. actinomycetemcomitans infections. The predominance of serotype b strains in endocarditis and bacteremia supports the hypothesis of a relationship between certain A. actinomycetemcomitans clones and some nonoral infections. The mechanisms behind the exceptionally high rate of occurrence of benzylpenicillin resistance among A. actinomycetemcomitans serotype b strains are to be elucidated in further studies.