- Volume 50, Issue 11, 2001

Whilst the diversity of organisms present in the oral cavity is well accepted, there remains considerable controversy as to whether Staphylococcus spp. play a role in the ecology of the normal oral flora. Surprisingly little detailed work has been performed on the quantitative and qualitative aspects of colonisation or infection either by coagulase-negative staphylococci (CNS) or S. aureus. The latter is especially interesting in the light of present difficulties in eradicating carriage of methicillin-resistant S. aureus (MRSA) from the oropharynx in affected individuals. This paper reviews the current knowledge of staphylococcal colonisation and infection of the oral cavity in health and disease. S. aureus has been isolated from a wide range of infective oral conditions, such as angular cheilitis and parotitis. More recently, a clinical condition classified as staphylococcal mucositis has emerged as a clinical problem in many debilitated elderly patients and those with oral Crohn's disease. Higher carriage rates of both CNS or S. aureus, or both, in patients prone to joint infections raises the interesting possibility of the oral cavity serving as a potential source for bacteraemic spread to compromised joint spaces. In conclusion, there is a surprising paucity of knowledge regarding the role of oral staphylococci in both health and disease. Further work in this area may lead to benefits, such as improved decolonisation regimens for eradication of MRSA and acknowledgement of the mouth as a source of bacteraemic staphylococci.

A novel antigen that induces nitric oxide (NO) synthesis by murine peritoneal exudate cells (PEC) was prepared from a culture supernate of Streptococcus anginosus NCTC 10713 in dialysed medium by column chromatography with DEAE-Sephacel followed by size-exclusion high performance liquid chromatography (HPLC). A chemical analysis of the S. anginosus antigen (SAA) revealed that it mainly consisted of carbohydrates (rhamnose, N-acetylglucosamine, glucose and galactose), smaller quantities of protein and a trace amount of phosphorus. The SAA stimulated PEC from C57BL/6N mice to produce NO and accumulate induced NO synthetase (iNOS) mRNA in a dose-dependent manner, reaching a plateau with 10–30 μg/ml. Furthermore, a reverse transcription-PCR assay revealed that SAA 10 μg/ml could induce mRNA accumulation of tumour necrosis factor-α, interleukin (IL)-1β and IL-6 as well as iNOS. In contrast, Rantz-Randall antigen (RRA), a carbohydrate antigen prepared from the organisms, could not induce NO synthesis or cause the accumulation of iNOS mRNA, although cytokine production was observed after stimulation. The SAA-induced NO synthesis, but not the cytokine production, was sensitive to heat. Furthermore, an immunoblot analysis of SAA indicated that the 43-kDa protein band reacted with anti-SAA but not anti-RRA antibodies. In immunodiffusion, SAA reacted with both anti-SAA and anti-RRA antibodies, and the precipitin bands formed crossing lines, suggesting that SAA could possess two different antigenic components – one that reacts specificially with anti-SAA antibodies and another that has an identity similar to that of RRA. Taken together, SAA, a novel antigen of S. anginosus, was found to induce NO synthesis as well as produce inflammatory cytokines in murine PEC. It is suggested that the protein molecule of SAA may exclusively induce NO synthesis, and its carbohydrate component(s) could have a relationship to cytokine production.

An international external quality assessment (EQA) scheme has been established so as to evaluate the proficiency of specialist, national diphtheria reference laboratories in the laboratory diagnosis of diphtheria. Six simulated clinical specimens were freeze-dried and distributed to 23 participants in 20 countries. Participants were asked to isolate, identify and perform toxigenicity testing on any corynebacteria present and to complete a simple questionnaire describing the procedures and reagents used. Only three laboratories obtained correct biochemical and toxigenicity results for all six specimens. The majority of laboratories performed better with toxigenicity testing than with the biochemical identification. Of concern were the results from three laboratories that failed to isolate any corynebacteria from four or more of the specimens. In one centre this was shown to be due to lack of availability of ‘in-date’ media and, in the other two, was presumed to be due to lack of experience in primary laboratory diagnostics for this organism. It is essential that countries, globally, maintain awareness and laboratory capabilities in this specialised area of microbiology. EQA is an invaluable process, which enables laboratories to monitor, evaluate and improve their own performance in such areas.

Enteroaggregative Escherichia coli (EAggEC) isolates were identified as a cause of traveller's diarrhoea in 50 (9%) of 517 patients and their antimicrobial susceptibility was determined. Molecular epidemiological characterisation and investigation of the mechanisms of acquisition of quinolone resistance among nalidixic acid-resistant EAggEC strains was performed. Seventeen (34%) of 50 patients needed antimicrobial therapy, because of persistence of symptoms in nine cases and the severity of symptoms in eight cases. Ampicillin and tetracycline resistance was high, whereas chloramphenicol and co-trimoxazole showed moderate activity and amoxicillin plus clavulanic acid, nalidixic acid and ciprofloxacin showed very good activity. Resistance to nalidixic acid was demonstrated in three isolates, two from patients who had travelled to India. In all three strains the resistance was linked to mutations in the gyrA gene alone or in both gyrA and parC genes. Although ciprofloxacin shows excellent in-vitro activity and could be useful in the treatment of traveller's diarrhoea in patients travelling abroad, it may not be useful in patients who have journeyed to India or to Mexico.

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.

Antigenic and immunochemical properties of Yersinia pestis fraction I (FI) preparations extracted by different methods were studied with polyclonal and monoclonal antibodies. The existence of mature FI in a form of a complex antigen whose subunits have different genetic control was demonstrated. Galactolipid was shown, with caf1 product, to be the second species-specific component of the FI complex molecule and is probably encoded by chromosomal genes. It, like caf1 product, was expressed in higher quantities at 37°C than at 28°C. Among FI subunits there were at least two proteins of 28 ± 2 kDa and 43 ± 2 kDa which were not specific for Y. pestis but were found also in all Yersinia spp. and some other bacteria. These proteins were synthesised independently of the incubation temperature (4°–40°C) and are possibly encoded chromosomally but outside the caf operon and galactolipid-encoding genes. Both proteins together with galactolipid comprise an envelope antigen found in pFra− or plasmidless Y. pestis strains. Organisation of Y. pestis FI (mature capsular antigen) in the form of a complex of the envelope antigen and the caf1 product is discussed.

During a period of increasing meningococcal disease incidence in Belgium, all 538 serogroup B and all 87 serogroup C strains isolated between 1996 and 1998 were investigated by PCR with the arbitrary primer D8635, which is able to identify lineage III strains. In all, 399 strains (64%) were attributed to lineage III on the basis of PCR-based typing. Since their introduction in the Belgian population in the early 1990s, lineage III strains have become increasingly variable in phenotype. Currently, they are represented by strains belonging to 38 different phenotypes, of which 25 were not found in the period 1990–1995. The 87 serogroup C strains were further investigated by pulsed-field gel electrophoresis (PFGE), and a subset of 30 strains was also investigated by multilocus sequence typing (MLST). Strains of phenotype C:2b:P1.5,2, which currently constitute the majority of the serogroup C strains, were demonstrated to belong to cluster A4. Comparison of the discriminatory ability of D8635-primed PCR, PFGE and MLST revealed that D8635-primed PCR was the least discriminatory method and PFGE the most discriminatory method. However, the MLST data were more readily interpreted than the PFGE fingerprint patterns and can be compared easily with data obtained in other studies. In conclusion, the ongoing increase of meningococcal disease in Belgium could be attributed not only to the further expansion of lineage III, but also to the introduction of C:2b:P1.5,2 strains of cluster A4 in to the Belgian population.