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L G Visser

Publications and source records attributed to L G Visser.

36 records · Page 2Linked to original sources
PubMed2000

Outbreak of amebiasis in a family in The Netherlands.

Human-to-human transmission of Entamoeba histolytica is rare in industrialized countries. We describe an outbreak of amebiasis in a family in The Netherlands, demonstrating that even with Western standards of hygiene, persistent cyst passage may result in the transmission of E. histolytica to household contacts. If E. histolytica is isolated from a person living in an area of nonendemicity, it may be worthwhile to test all family members for cyst passage.

Adult↗
PubMed2000

Typhoid fever in group travelers: opportunity for studying vaccine efficacy.

BACKGROUND: Typhoid fever (TF) is a rare disease among travelers to endemic areas, and little is known about its travel-related epidemiology. In addition, efficacy data on TF vaccines in travelers is scanty. During 3 months of 1994/95, six cases of TF were reported in The Netherlands among participants of four package tours to Indonesia provided by the same operator. The present study was designed to describe the epidemiology of TF in these groups, and to assess whether travel groups can be used for studying the efficacy of TF vaccines in travelers. METHOD: Questionnaire-based historical cohort study of participants of 4 groups that stayed in the same hotels along their tours (n=156). TF was defined as blood culture-confirmed Salmonella typhi infection. Submitted isolates were typed by antigen and phage typing. Immunization status was considered documented if ascertained by written records. RESULTS: Among 110 participants (71%), six cases of TF were identified (group specific attack rate AR 5.4%), three of which were from one travel group (AR 12.0%). There were no significant differences by age or sex. Three submitted S. typhi isolates showed three different types, two of which were in the same group. Eighty-three percent of respondents reported documented TF vaccination in the preceding 3 years. All cases occurred in recipients of the oral Ty21a vaccine (AR 10.2%, 95% CI 3.8-20.8%), but differences with nonvaccinees and recipients of the heat-inactivated whole cell or Vi-antigen polysaccharide vaccines were not significant. CONCLUSIONS: Although TF is rare in travelers, infections with different strains of S. typhi can occur in one travel group. Travel groups offer an opportunity for retrospective assessment of vaccine efficacy, provided that equal chance of exposure is largely guaranteed; case ascertainment is maximally specific and similar in the vaccine groups; vaccine status is ascertained accurately; and prior immunity by previous exposures to and use of antibiotics effective against the infection are excluded from, or controlled for in, the analysis.

Adult↗
PubMed1999

Yops of Yersinia enterocolitica inhibit receptor-dependent superoxide anion production by human granulocytes.

The virulence plasmid-borne genes encoding Yersinia adhesin A (YadA) and several Yersinia secreted proteins (Yops) are involved in the inhibition of phagocytosis and killing of Yersinia enterocolitica by human granulocytes. One of these Yops, YopH, dephosphorylates multiple tyrosine-phosphorylated proteins in eukaryotic cells and is involved in the inhibition of phagocytosis of Y. enterocolitica by human granulocytes. We investigated whether antibody- and complement-opsonized plasmid-bearing (pYV+) Y. enterocolitica inhibits O2- production by human granulocytes in response to various stimuli and whether YopH is involved. Granulocytes were preincubated with mutant strains unable to express YadA or to secrete Yops or YopH. O2- production by granulocytes during stimulation was assessed by measuring the reduction of ferricytochrome c. PYV+ Y. enterocolitica inhibited O2- production by granulocytes incubated with opsonized Y. enterocolitica or N-formyl-Met-Leu-Phe (f-MLP). This inhibitory effect mediated by pYV did not affect receptor-independent O2- production by granulocytes in response to phorbol myristate acetate, indicating that NADPH activity remained unaffected after activation of protein kinase C. The inhibition of f-MLP-induced O2- production by granulocytes depends on the secretion of Yops and not on the expression of YadA. Insertional inactivation of the yopH gene abrogated the inhibition of phagocytosis of antibody- and complement-opsonized Y. enterocolitica by human granulocytes but not of the f-MLP-induced O2- production by granulocytes or tyrosine phosphorylation of granulocyte proteins. These findings suggest that the specific targets for YopH are not present in f-MLP receptor-linked signal transduction and that other Yop-mediated mechanisms are involved.

Actins↗
PubMed1997

Detection of the circulating antigens CAA and CCA in a group of Dutch travellers with acute schistosomiasis.

Detection of circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) in serum and urine is a highly specific and sensitive alternative for the diagnosis of schistosome infections in endemic areas. However, it is not known how soon after the onset of infection these antigens can be detected in humans. Neither has there been much research on the detection of these antigens in individuals normally living in non-endemic areas. We studied the kinetics of CAA and CCA in serum and urine of a group of 28 Dutch tourists, shortly after accidental exposure to a Schistosoma infection during a visit to Mali. Twenty-seven were found to be positive for Schistosoma eggs and/or specific antibodies. From each individual, 1-4 serum samples were tested for circulating antigen level, 4-15 weeks after exposure, and urine samples were also tested from 22 subjects. CAA and CCA levels were quantified by monoclonal antibody-based ELISAs and TRIFMAs. In serum, 23 individuals (85%) were positive at least once for one or both antigens, but titres were generally very low. CAA and CCA could be detected 5 and 6 weeks after exposure, respectively. Urines were all found to be negative. Almost all cases were negative at 7 months' follow-up.

Adult↗
PubMed1996

Role of YadA in resistance to killing of Yersinia enterocolitica by antimicrobial polypeptides of human granulocytes.

The virulence plasmid pYVe of Yersinia enterocolitica codes for the production of the outer membrane protein YadA and the secretion of several proteins, called Yops, which may protect this bacterium against killing by human granulocytes. Granulocytes kill ingested microorganisms by oxygen-dependent and oxygen-independent mechanisms, the latter including antimicrobial polypeptides. The aim of this study was to determine whether virulent (pYVe+) Y. enterocolitica and plasmid-cured avirulent (pYVe-) Y. enterocolitica differ in susceptibility to antimicrobial polypeptides extracted from granules of human granulocytes. The acetic acid granule extract contained several polypeptides with antimicrobial activity against Y. enterocolitica as determined by gel overlay and radial diffusion assays. Two of these polypeptides were identified as lysozyme and defensins. pYVe+ Y. enterocolitica was less susceptible than pYVe- Y. enterocolitica to the antimicrobial activity of granule extract, lysozyme, and defensins as determined in a suspension assay, which indicated that the pYVe plasmid mediates a reduced susceptibility to these polypeptides. The role of YadA in the resistance to antimicrobial polypeptides was analyzed by using mutants of Y. enterocolitica that specifically lack or express YadA. The results demonstrated that YadA conferred resistance to the killing of Y. enterocolitica by the granule extract. Together, these results indicate that the plasmid-encoded factor YadA contributes to the resistance of Y. enterocolitica to the killing by antimicrobial polypeptides of human granulocytes.

Adhesins, Bacterial↗
PubMed1995

Outbreak of schistosomiasis among travelers returning from Mali, West Africa.

Schistosomiasis in travelers often remains unrecognized because doctors are unfamiliar with the clinical presentation and diagnosis of this imported disease. We describe the epidemiological, clinical, and laboratory characteristics associated with an outbreak of schistosomiasis among nonimmune travelers. Of 30 travelers in two consecutive groups, 29 who had swum in freshwater pools in the Dogon area of Mali, West Africa, were followed for 12 months. Twenty-eight (97%) of those 29 became infected; 10 (36%) of the 28 had cercarial dermatitis, and in 15 (54%), Katayama fever developed. Eggs were found in 22 (79%) of the infected travelers: eggs of Schistosoma mansoni or terminally spined eggs (probably of Schistosoma intercalatum) were in the stools of 19 and 10 patients, respectively, and eggs of Schistosoma haematobium were in the urine of 7 patients. The eggs of 2 of these Schistosoma species were present in 6 cases, and in 4 cases eggs of all 3 species were found. The limited exposure of this group of travelers resulted in a high rate of infection with all three of the Schistosoma species that are prevalent in Africa. A diagnosis of schistosomiasis should be considered for any traveler with a history of exposure to fresh water in an area of endemicity. The only effective method of prevention is avoiding all contact with fresh water in these areas.

Adult↗
PubMed1995

Role of Yops in inhibition of phagocytosis and killing of opsonized Yersinia enterocolitica by human granulocytes.

The virulence plasmid of Yersinia enterocolitica codes for the production of the outer membrane protein YadA and the secretion of several proteins, called Yops, which may play a role in the interaction between granulocytes and this bacterium. We investigated whether the expression of YadA or the secretion of Yops affected the phagocytosis and killing of opsonized Y. enterocolitica by human granulocytes. The rates of phagocytosis and killing of Y. enterocolitica by granulocytes in suspension in the presence of rabbit Yersinia antibodies and complement were determined by microbiological assays. In addition, noningested cell-adherent bacteria were differentiated from ingested yersiniae by immunofluorescence microscopy. Plasmid-bearing opsonized Y. enterocolitica was able to inhibit phagocytosis and killing by human granulocytes. The inhibition of phagocytosis was specific for the plasmid-bearing strain of Y. enterocolitica, since granulocytes were still able to phagocytose and kill Staphylococcus aureus in the presence of Y. enterocolitica. Plasmid-cured Y. enterocolitica was readily phagocytosed and killed by these cells. To investigate the role of YadA or Yops in the inhibition of phagocytosis by granulocytes, the phagocytosis of mutant strains unable to express YadA or to secrete Yops was studied. A Y. enterocolitica mutant unable to secrete Yops lost its ability to inhibit phagocytosis; a mutant expressing only YadA was readily ingested by granulocytes. These results indicate that after attachment of opsonized Y. enterocolitica to granulocytes, Yops play an important role in inhibiting the ingestion of Y. enterocolitica by human granulocytes.

Adhesins, Bacterial↗
PubMed1993

[Ameboma of the large intestine and rectum].

Amoeboma was diagnosed in three patients: a Bengal seaman aged 40 and two Dutch citizens who had lived in the tropics, a man aged 41 and a woman aged 56. The first-mentioned patient had a rectal tumour easily inspected by sigmoidoscopy; a biopsy sample contained Entamoeba histolytica. The faeces contained no cysts. The two other patients had coecal amoebomas. They had been operated elsewhere on suspicion of appendicitis and had been treated with metronidazole, which had failed to eliminate the amoebae. The faeces still contained cysts. One patient had trophozoites in a biopsy sample. The serum of all three patients contained anti-amoeba antibodies. Two patients were treated successfully with a combination of metronidazole (a tissue amoebicide) and diloxanide (a lumenal amoebicide). In one patient this combination failed, and emetine had to be substituted for the metronidazole, also because of an allergic reaction. Amoeboma of colon or rectum is one of the many manifestation forms of amoebiasis, but it is rare. While in amoebic colitis tissue necrosis (histolysis) is encountered almost exclusively, in amoeboma there is a violent inflammatory reaction with formation of a pseudotumour by granulation tissue, possibly due to secondary bacterial infection. Endoscopy and determination of circulating antibodies against the causative agent E. histolytica have by now improved the diagnosis so much that adequate treatment without surgical intervention is possible in principle. As with so many exotic diseases, a stay in the tropics is the key to the diagnosis.

Adult↗
PubMed1993

[Mycetoma of the foot; a disease from the tropics].

Two patients, a Surinamese man aged 50 and a Surinamese woman aged 56 exhibited a mycetoma of the foot, 30 and 28 years, respectively, after a local injury. Pathological examination revealed an aspecific chronic granulomatous inflammation. As causative agents a Fusarium species and a Cladosporium normodendrum, respectively, were cultured. The treatment consisted of curettage of fistulous ducts and administration of itraconazole.

Antifungal Agents↗
PubMed1993

Clinical pharmacokinetics of continuous intravenous administration of penicillins.

Theoretically, continuous intravenous administration of beta-lactam antibiotics has advantages over intermittent administration because of the close relationship between efficacy and the time the plasma concentration remains above the minimal inhibitory concentration that has been found in vitro. The aim of the present study was to establish the pharmacokinetic parameters of benzylpenicillin and cloxacillin administration in patients receiving high-dose benzylpenicillin or cloxacillin therapy by continuous infusion. A major part of the interindividual variation in the plasma concentrations at steady-state was attributable to variation in renal function, as estimated by the creatinine clearance. On the basis of these results, a nomogram was constructed that can be used to determine on an individualized basis the total daily dose of benzylpenicillin or cloxacillin necessary for each patient to obtain therapeutic plasma concentrations.

Adolescent↗
PubMed1992

Unusual manifestations of Yersinia enterocolitica infections diagnosed using novel methods.

We report the cases of two patients who had infections due to Yersinia enterocolitica. The first patient exhibited chronic recurrent fever, hepatic and splenic granulomas, and bone marrow abnormalities, and the second patient presented with enterocolitis with leukocytoclastic vasculitis of the skin. Cultures and agglutination titers were negative. Indirect immunofluorescence techniques with use of serotype-specific antisera and antisera to Yersinia outer-membrane proteins (Yops) were applied to biopsy specimens, and immunoblotting techniques for determining class-specific circulating antibodies to Yops were used for demonstrating these unusual manifestations of Y. enterocolitica infections.

Adult↗
PubMedDate not supplied

Measurement of antibody response to keyhole limpet haemocyanin was not adequate for early diagnosis of schistosomiasis in a group of Dutch visitors to Mali.

The detection of antibodies against keyhole limpet haemocyanin (KLH) (extracted from Megathura crenulata) has been described as a reliable tool for serological diagnosis of acute, but not chronic, schistosomiasis. We evaluated the immunoglobulin (Ig) G and IgM anti-KLH enzyme-linked immunosorbent assay (ELISA) for the serological diagnosis of light schistosome infections and to follow response after treatment, using sera from a group of Dutch travellers returning from Mali with acute schistosomiasis. Before chemotherapy, the sensitivities of the anti-KLH IgM and IgG ELISAs were 74% and 63%, respectively. In contrast, a sensitivity of 100% was found with an immunofluorescence assay for determination of IgM antibodies against gut-associated glycoconjugates. There was no significant difference in the anti-KLH response before, and one year after, therapy. These results indicate that, for travellers from non-endemic areas like The Netherlands with generally light schistosome infections, detection of antibody response against KLH is not a useful tool for serodiagnosis of acute schistosomiasis.

Acute Disease↗