- Volume 41, Issue 5, 1994

Early reports of Candida krusei in man describe the organism as a transient, infrequent isolate of minor clinical significance inhabiting the mucosal surfaces. More recently it has emerged as a notable pathogen with a spectrum of clinical manifestations such as fungaemia, endophthalmitis, arthritis and endocarditis, most of which usually occur in compromised patient groups in a nosocomial setting. The advent of human immunodeficiency virus infection and the widespread use of the newer triazole fluconazole to suppress fungal infections in these patients have contributed to a significant increase in C. krusei infection, particularly because of the high incidence of resistance of the yeast to this drug. Experimental studies have generally shown C. krusei to be less virulent than C. albicans in terms of its adherence to both epithelial and prosthetic surfaces, proteolytic potential and production of phospholipases. Furthermore, it would seem that C. krusei is significantly different from other medically important Candida spp. in its structural and metabolic features, and exhibits different behaviour patterns towards host defences, adding credence to the belief that it should be re-assigned taxonomically. An increased awareness of the pathogenic potential of this yeast coupled with the newer molecular biological approaches to its study may facilitate the continued exploration of the epidemiology and pathogenesis of C. krusei infections.

The immunodominant and T-cell epitopes within the fimbrial subunit protein (fimbrilin) of Porphyromonas gingivalis strain 381 were analysed by multi-pin peptide synthesis technology. Six regions with immunodominant epitopes within a sequence of 337 amino acids that reacted with the serum of patients with adult periodontitis were detected. T cells from mice immunised with P. gingivaĭis fimbriae exhibited proliferative responses to P. gingivalis fimbriae or to six 10.mer synthetic peptides from the amino-acid sequence of the fimbrillin. Three synthetic peptides that contained the regions responsible for the immunodominant epitopes as well as those which coincided with a T-cell epitope of P. gingivalis fimbrial molecules—FP381(142–161), FP381(202–221) and FP381(216–243)—were selected and synthesised. When guinea-pigs were immunised with fimbriae or one of the three synthetic peptide segments and an adjuvant in Freund’s incomplete adjuvant, enhanced production of the antigen-specific IgG antibodies was induced in the serum of the animals. Furthermore, of the three synthetic peptides tested, FP381(202–221) produced the greatest protective immune response in guinea-pigs infected with P. gingivaĭis and this was more effective than the native fimbrial protein.

The prevalence of trimethoprim resistance in enterobacterial urinary pathogens from hospitalised patients in the Angus district of northern Scotland (22.8 %) was twice that found in similar isolates from patients attending general practitioners (11.2%). Thirty-three of the 143 trimethoprim-resistant strains were shown to harbour transferable plasmids conferring high-level trimethoprim resistance. In total, 17 different plasmid types were distinguished. Two plasmids, pUK1184 and pUK1185, accounted for 36% of the trimethoprim resistance plasmids and were shown by restriction endonuclease digestion fingerprints to be closely related to plasmid pUK28, previously demonstrated to be endemic in urinary pathogens in the Edinburgh area. Only 21 % of the plasmids were shown to encode the type la trimethoprim-resistant dihydrofolate reductase, whereas 70 % of the trimethoprim resistance plasmids were found to encode the type Ib dihydrofolate reductase. Hybridisation of the trimethoprim resistance plasmids identified in this study with gene probes specific for the integrase genes of transposons Tn7 and Tn21 indicates that the dhfrIa is rarely present within Tn7 or related transposons in these plasmids and may be more prevalent within Tn21-like transposons. In contrast, with the exception of the two endemic plasmids that harboured the dhfrIb gene within a Tn7-like transposon, the majority of dhfrIb genes were not found to be associated with either Tn7- or Tn21-like structures.

The aim of the study was to determine whether patients with meningococcal disease carry meningococci in the throat both before and after treatment for the disease. During the 7 months of the study 106 patients with confirmed meningococcal disease were admitted to Danish hospitals, of whom 77 (73 %) had a throat swab examined at least once and were included in the study. Sixty-two patients were examined on admission and 52 were examined on discharge; 37 were examined on both occasions. On admission, meningococci were isolated from 18 (49%) of 37 throat specimens examined selectively for pathogenic Neisseria spp. Meningococci were not isolated from any throat specimen taken on discharge from hospital; 47 (90%) of 52 of these specimens had been examined adequately. From an observed carriage rate of 0 out of 47 it can be judged that the carrier rate does not exceed 6.4 % (95 % confidence limit). From these results we conclude that it is unlikely that patients who have been treated for meningococcal disease according to the regimens used in Denmark can be the source of infection for secondary cases.

The growth of 24 Aspergillus isolates at low oxygen tensions was assessed. Isolates selected included A.fumigatus (10), A. terreus (6), A. niger (6), A. nidulans (1) and A. flavus (1). Three different agar media were used—potato dextrose agar (PDA), pH 5.6; brain heart infusion (BHI), pH 7.4; and a specially developed medium (Hall’s) containing resazurin— with oxygen concentrations of 0, 0.025, 0.1, 0.5 and 2.5 %. The CO2 concentration was 5 %. Agar plates were inoculated with 2 × 107 conidia/ml, loaded into jars and flushed with a special gas mixture at 37°C. The plates were inspected at intervals of 3, 5 and 10 days. On Hall’s medium, none of the isolates grew at oxygen concentrations of 0 or 0.025 %, but 21 (88 %) of 24 grew at 01 %. On PDA and BHI, all 14 isolates tested grew at oxygen concentrations of 0.5 and 2.5 %. Three of these 14 conidiated on PDA at oxygen 0.5 % and 12 of 14 conidiated on PDA at oxygen 2.5%. None grew without oxygen on these media. Thus, pathogenic Aspergillus spp. are capable of growth at low oxygen tensions, and this may have implications for pathogenicity and antifungal activity.

Patterns of agglutination of 124 clinical isolates of β-haemolytic streptococci (30 group A and 94 group B isolates) by 21 commercial lectins are reported. Cell suspensions were untreated. Nine (30%) of the group A isolates, and 23 (24%) of the group B isolates, were agglutinated by at least one of the lectins. Ten different patterns of agglutination were observed with group A and 15 with group B streptococci. No pattern, except that of nonagglutination by any lectin, was common to group A and group B isolates. In view of the growing interest in the use of lectin typing there is a need for standardisation of assay procedures to enable meaningful comparison of the results of different research groups.

Stool samples (355 from 350 patients) were examined in a new commercial assay, the ToxA test, for the rapid diagnosis of Clostridium difficile-associated diarrhoea. The results were compared with direct assay of cytotoxin in McCoy cell tissue culture, and detection of toxigenic C. difficile by culture and cytotoxin testing of isolates. Discordant results were resolved by consultation of clinical records. Test sensitivities were 84.6% for the ToxA test, 78.5 % for the direct cytotoxicity assay and 95.4% for culture. The specificity was 100% for all the tests. The ToxA test is a rapid and reliable alternative for the detection of toxigenic C. difficile where tissue culture facilities are unavailable.