- Volume 41, Issue 4, 1994

Liver disease is a common finding after organ transplantation and might in part be due to transmission of hepatitis C virus (HCV). The aim of this study was to determine the prevalence of positive results with different anti-HCV tests and HCV-RNA in a local donor pool and to clarify to what extent HCV was transmitted to organ recipients. Serum samples from 207 consecutive organ donors were analysed retrospectively with anti-HCV ELISA (2nd and 3rd generation), anti-HCV RIBA (2nd generation) and HCV polymerase chain reaction (PCR). Organ recipients at risk were identified and followed up serologically and clinically. Anti-HCV seroprevalance in organ donors was 4 3 % for 2nd generation ELISA, 4 8 % for 3rd generation ELISA and 1-9 % for 2nd generation RIBA. HCV-PCR was positive in 1 4 %. Nine organs from four RIBA-positive donors were transplanted into eight recipients of whom four became anti-HCV and PCR positive after transplantation. HCV-PCR became positive several days after transplantation whereas anti-HCV seroconversion took place after 8-9 months. Two recipients developed acute liver disease and another two showed features of mild chronic liver disease but no serious complications due to HCV infection were observed.

The polymerase chain reaction (PCR) was used to identify the aacA-aphD, aphA3 and aadC genes, encoding the aminoglycoside-modifying enzymes AAC(6′)-APH(2″), APH(3′)III and ANT(4′ 4″), respectively, and the methicillin resistance determinant mecA, in epidemic aminoglycoside and methicillin-resistant isolates of Staphylococcus aureus. In total, 37 isolates collected in the period 1980–1985 and 81 isolates from the period 1991–1992 were obtained from 10 different Belgian hospitals. Epidemic isolates from the earlier period were characterised by phage type C (6/47/54/75) of phage group III, whereas two other epidemic phage types of group III—types A (77) and B (47/54/75/77/84/85)—were commonest in isolates from the second period. The bifunctional AAC(6′)-APH(2//) was the enzyme encountered most frequently. The prevalence of APH(3 )III decreased significantly in the 1991–1992 period, while ANT(4′, 4″) was found solely in isolates from this period. Resistance mechanisms were more complex in isolates from the 1991–1992 period and the mecA gene was detected in all isolates. The PCR results corresponded well with those obtained in the radiochemical phosphocellulose paper binding assay. Isolates from the 1991–1992 period were shown to express significantly higher levels of acetyltransferase activity than isolates from the 1980s.

A tissue culture assay system to detect Campylobacter jejuni cytotoxin was developed, and the effect of culture conditions on cytotoxin production was examined. Brothculture filtrates from clinical isolates were used. The expression of cytotoxicity was dependent on the presence of serum in the culture medium. Although the titre of cytotoxin was low, the greatest cytotoxicity was revealed when newborn calf(NCS), adult bovine or goat serum was added to minimum essential medium. Moderate or weak cytotoxicity was observed when fetal calf(FCS), swine or human serum was added, and no cytotoxicity was seen with the addition of horse, rabbit, cat or chicken serum. Furthermore, the cytotoxic titre in serum-free culture (SFC) for Chinese hamster ovary (CHO) cells was higher than that with serum supplementation. CHO cells showed the highest sensitivity in FCS, NCS and SFC assay systems, whereas HeLa, Vero, HEp-2 and Intestine 407 cells were sensitive only in the NCS assay. Brucella broth was excellent for cytotoxin production, but iron supplementation had no effect. Cytotoxic expression in the three assay systems differed between stationary and stirred cultures. Our results on cytotoxin production by reference strains of C. jejuni did not agree with the original reports. These findings suggest that several different cytotoxins may be produced by C. jejuni, and that the assay system may be important for the expression of cytotoxic activity.

Candida krusei is an emerging pathogen, especially in immunocompromised hosts. As the adherence of this organism both to host epithelial surfaces and to catheter and prosthetic surfaces appears to be important in the pathogenesis of superficial as well as systemic candidoses, the adhesion of 20 oral isolates of C. krusei and five oral isolates of C. albicans was compared with the following substrates: cultured (HeLa) epithelial cells, buccal epithelial cells (BEC) from healthy adults and bone marrow transplant patients, and acrylic (polymethylmethacrylate) surfaces. Animal experiments in Sprague Dawley rats were also conducted to evaluate the relative oral carriage rate of the two Candida spp. C. krusei isolates adhered in far greater numbers to acrylic surfaces than to either of the cell surfaces. Significant intra-species differences in C. krusei adhesion for acrylic surfaces were noted between 74 (39 %) of 190 pair comparisons in contrast to 18 (9.5 %) of 190 with HeLa surfaces (p < 0.05). A positive correlation was also observed between the adhesion of C. krusei isolates to HeLa cells and acrylic surfaces. Five isolates of C. albicans showed very low adherence to HeLa surfaces when compared with BEC obtained from either healthy individuals or bone marrow transplant patients. The adherence of C. albicans to BEC from the healthy individuals was c. 12-fold greater than that of C. krusei, a figure similar to the relative murine oral carriage rate of the two Candida spp. However, the adhesion of C. albicans to BEC from bone marrow transplant patients was three-fold less than to BEC of healthy individuals whilst C. krusei adhesion remained the same, reflecting a possible selective colonisation process which may operate in these patient groups, possibly as a result of drug therapy. The current data, while confirming the inter- and intra-species differences in adherence of Candida spp. to host surfaces, illustrate that adherence-related factors may operate during colonisation of C. krusei on mucosal, catheter and prosthetic surfaces, in vivo in both health and disease.

To assess the applicability of a whole-cell ELISA (WCE) with monoclonal antibodies (MAbs) for lipo-oligosaccharide (LOS) immunotyping of Neisseria meningitidis, 675 meningococcal isolates obtained in 1989 and 1990 in the Netherlands and 57 isolates collected in 1974, of which the immunotype had been determined previously by microprecipitation, were analysed. Despite the lack of specific MAbs for L2 and L4, an algorithm was developed for the assignment of immunotypes on the basis of the reaction patterns of the reference strains and these isolates to a combination of 14 MAbs. The immunotypes found by WCE were in accordance with those obtained by microprecipitation and the results from WCE were reproducible. The distribution of immunotypes among isolates of the various serogroups in the Netherlands in 1989–1990 is presented. Based on the reaction patterns of the isolates, two main categories of related immunotypes could be distinguished among isolates of serogroups B and C: L2/L4 and L3/L1/L8. Some isolates of the latter category were of one immunotype, but many isolates expressed one or two additional immunotypes, either strongly or weakly, indicating that the differences in this category are quantitative rather than qualitative. The results of this study have demonstrated that the WCE method for LOS immunotyping is easily applicable and provides better definition of test strains for in-vitro bactericidal assays and research into pathogenesis.

Synthetic oligonucleotide primers were used in the polymerase chain reaction (PCR) to amplify a sequence of the spaP gene, which encodes the surface protein antigen I/II of Streptococcus mutans. A DNA fragment of c. 192 bp was amplified from lysed S. mutans cells or isolated DNA. With S. mutans cells, the lower limit of detection was 4–40 cfu. With these primers, 13 reference and 50 clinical strains of S. mutans were identified. Amplification of the 192-bp product was not demonstrated when 41 strains of other streptococcal and non-streptococcal species were tested. The spaP gene PCR has potential for the rapid diagnosis of S. mutans infections.