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Biomedical subjects

R J van Ketel

Publications and source records attributed to R J van Ketel.

At least 19 recordsLinked to original sources
PubMed2000

Apparent culture-negative prosthetic valve endocarditis caused by Peptostreptococcus magnus.

In two patients with prosthetic valve endocarditis due to Peptostreptococcus magnus, blood cultures in the BacT/Alert and BACTEC 9240 systems were signal negative. The capability of the BacT/Alert system to detect various Peptostreptococcus species was assessed. P. magnus and P. anaerobius could not be detected, and subcultures remained negative. The growth in conventional media of these two species and other Peptostreptococcus species was similar.

Adult↗
PubMed1997

Circadian variations in serum levels and the renal toxicity of aminoglycosides in patients.

Animals show a faster clearance and a lower incidence of nephrotoxicity and ototoxicity when aminoglycosides are administered during the activity period. Human data on a circadian rhythm in pharmacokinetics are conflicting, and there are no data on a circadian rhythm in toxicity. When aminoglycosides are administered once daily, as is often done, a circadian rhythm in pharmacokinetics or toxicity could have clinical implications. In a prospective study we investigated the influence of drug administration time on serum drug levels and the incidence of nephrotoxicity in 221 patients with serious infections treated with gentamicin or tobramycin once daily. We did not find statistically significant differences in trough or peak levels for the three time periods (midnight to 7:30 AM, 8 AM to 3:30 PM, and 4 to 11:30 PM). Nephrotoxicity occurred significantly more frequently when the aminoglycosides were administered during the rest period (midnight to 7:30 AM; p = 0.004). In addition to the coadministration of high-dose furosemide or other nephrotoxic antibiotics and the duration of treatment, the time of administration was still an independent risk factor in a multivariate analysis.

Adolescent↗
PubMed1996

Validation and nephrotoxicity of a simplified once-daily aminoglycoside dosing schedule and guidelines for monitoring therapy.

There is no established dosing schedule for once-daily aminoglycoside dosing regimens, and accepted guidelines for monitoring therapy are lacking. We derived a simplified schedule from the Hull and Sarubbi (J. H. Hull and F. A. Sarubbi, Ann. Intern. Med. 85:183-189, 1976) nomogram, for which efficacy and safety in a once-daily dosing regimen were previously demonstrated, and prospectively followed serum aminoglycoside levels in patients. The standard treatment was gentamicin or tobramycin at 4 mg/kg of body weight given intravenously once daily. When the renal function was decreased, the daily dose was reduced, as follows: for an estimated creatinine clearance of between 50 and 80 ml/min, the daily dose was 3.25 mg/kg, for an estimated creatinine clearance of between 30 and 50 ml/min, the daily dose was 2.5 mg/kg, and for an estimated creatinine clearance of below 30 ml/min, the daily dose was 2 mg/kg. A total of 221 patients were studied (184 received gentamicin and 37 received tobramycin). First trough levels above 2 mg/liter were recorded in 11% of the patients, and they all had a baseline creatinine clearance below 50 ml/min, or a substantial decrease in clearance between enrollment and the day that the trough level was obtained. A peak level below 6 mg/liter was recorded in 6% of the patients, and half of them received the lowest daily dose. Twenty-five of the 179 evaluable patients (14%; 95% confidence interval, 9 to 19%) fulfilled the criteria for nephrotoxicity. In a multiple regression analysis, the duration of treatment and the use of other nephrotoxic antibiotics or high-dose furosemide, but not trough levels, were significant risk factors. Since the meaning of low peak levels is unclear and since most studies with multiple daily regimens confirm the lack of an association between trough levels and toxicity, we believe that monitoring of serum drug levels can be restricted to monitoring of trough levels in patients with a creatinine clearance below 50 ml/min or with a deteriorating renal function.

Adolescent↗
PubMed1993

Legionella monitoring: a continuing story of nosocomial infection prevention.

Of 21 cases of legionellosis, 14 were of nosocomial origin and 6 others had a possible nosocomial source. The hot and cold water systems, respiratory therapy equipment, puddles of rain water on flat roofs and in gutters, and demineralized water systems were all excluded as a source of nosocomial infection. By subtyping it was shown that Legionella pneumophila serogroup 1 isolates from 11 patients and from the cooling towers were indistinguishable. Because of this result the cooling towers were considered to be the infection source. After effective chlorination of the cooling towers, the frequency of legionellosis declined.

Adult↗
PubMed1992

[Routine screening for syphilis in neurology is not useful].

In a retrospective study the results of the screening for syphilis in one of the neurological wards of the Academic Medical Centre in Amsterdam were analysed. The Venereal Disease Research Laboratory test (VDRL) and the Treponema Pallidum Haemagglutination Assay (TPHA) in serum were used for screening. The data for analysis were obtained via the hospital computer data base and via the medical files of the department of neurology. During the 5-year study period (1986-1990) 2378 adult patients were admitted and 1247 (52.4%) of them were screened. In seven (0.56%) patients both tests were positive. Three of them had been treated for syphilis in the past and showed no symptoms of active syphilis. Four (0.32%) patients suffered from active neurosyphilis. In three of these four patients syphilis was suspected on admission and confirmed by the tests. In one patient the diagnosis of syphilis was not considered. The positive test results became available shortly before she died of pneumonia and were without consequences. None of the 32 (2.6%) patients with a positive TPHA and a negative VDRL was diagnosed as having (neuro-)syphilis. Two (0.16%) patients had a false-positive VDRL. We conclude that routine serological examination for syphilis of every patient admitted to a neurological ward is not useful. We advise a limited screening of patients who belong to a group with high risk for syphilis and patients with symptoms and signs that can be caused by syphilis, such as dementia or ischaemic strokes at a relatively young age.

Adult↗
PubMed1992

Itraconazole compared with amphotericin B plus flucytosine in AIDS patients with cryptococcal meningitis.

OBJECTIVE: We conducted a comparison of itraconazole versus amphotericin B plus flucytosine in the initial treatment of cryptococcal meningitis in patients with AIDS and established the efficacy of itraconazole as maintenance treatment. DESIGN: The trial was a prospective, randomized, and non-blinded study. SETTING: The study was performed at an academic centre for AIDS, Amsterdam, The Netherlands. PATIENTS, PARTICIPANTS: Twenty-eight HIV-1-seropositive men with a presumptive diagnosis of cryptococcal meningitis, randomized between 5 February 1987 and 1 January 1990, were included for analysis. INTERVENTIONS: Oral itraconazole (200 mg twice daily), versus amphotericin B (0.3 mg/kg daily) intravenously plus oral flucytosine (150 mg/kg daily) was administered for 6 weeks followed by maintenance therapy with oral itraconazole (200 mg daily) to all patients. MAIN OUTCOME MEASURES: Outcome measures were a complete or partial response, recrudescence and relapse. RESULTS: A complete response was observed in five out of the 12 patients who completed 6 weeks of initial treatment with itraconazole versus all 10 patients who completed treatment with amphotericin B plus flucytosine (P = 0.009). A partial response was observed in seven out of the 14 patients assigned to itraconazole. During maintenance therapy, recrudescence (n = 6) or relapse (n = 1) occurred in seven out of the 12 patients initially assigned to itraconazole, whereas two relapses occurred among nine patients initially treated with amphotericin B plus flucytosine (P = 0.22); recurrence of clinical symptoms was significantly related to a positive cerebrospinal fluid culture at 6 weeks (P = 0.003). CONCLUSION: Itraconazole is less effective compared with amphotericin B plus flucytosine in achieving a complete response in initial therapy in AIDS patients with cryptococcal meningitis.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Clinical significance of small-intestinal microsporidiosis in HIV-1-infected individuals.

To assess the importance of microsporidiosis of the small intestine in the pathogenesis of chronic diarrhoea in HIV-1-infected individuals, duodenal biopsy samples from the following three patient groups were prospectively evaluated for bacterial, viral, and parasitic pathogens by standard methods, and for microsporidia by light microscopy: 55 consecutive HIV-1-antibody-positive subjects with unexplained diarrhoea of at least 3 weeks duration (group A); 38 HIV-1-seropositive subjects without diarrhoea (group B) who consecutively underwent upper gastrointestinal endoscopy for various reasons; and 7 patients without known risk factors for HIV infection with chronic unexplained diarrhoea (group C). In groups A and B most subjects had had previous AIDS-defining opportunistic infections and the median peripheral blood CD4 lymphocyte count was less than 0.1 x 10(9)/l. Microsporidia were detected as the single pathogen in 15 of the group A compared with 1 (in whom diarrhoea subsequently developed) of the group B patients (p = 0.001) and none of the group C patients. With the exception of 4 of the group A patients, no other intestinal pathogens were identified in any of the patients. The median peripheral blood CD4 count was significantly lower in patients with detectable microsporidia than in those without microsporidiosis (0.03 x 10(9)/l vs 0.06 x 10(9)/l; p = 0.03); in all patients with microsporidiosis, the CD4 count was equal to or less than 0.1 x 10(9)/l. 13 patients with microsporidiosis were treated with metronidazole, in 10 of whom treatment led to a substantial improvement or disappearance of diarrhoea within days of starting therapy, but did not result in eradication of the parasite in the 5 patients who underwent repeat biopsy. The findings suggest that small-intestinal microsporidiosis is an important cause of chronic unexplained diarrhoea in HIV-1-infected individuals with pronounced cellular immune deficiency. This infection should therefore be added to the list of AIDS-defining opportunistic infections.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Incidence and clinical epidemiology of streptococcal septicemia during treatment of acute myeloid leukemia.

The incidence and outcome of streptococcal septicemia was analyzed in 76 consecutive patients with newly diagnosed and relapsed acute myeloid leukemia. They received 215 courses of remission induction or intensive consolidation treatment. There were 31 different episodes of streptococcal septicemia in 27 patients, making these microorganisms the most frequently encountered bacteria in blood cultures. This high incidence coincided with the introduction of selective intestinal decontamination. In 24 episodes (20 patients) there was a fast recovery, but 7 patients developed pulmonary symptoms resulting in death due to respiratory failure in 5 of them. The infections all occurred in the phase of maximum bone marrow suppression 1-3 weeks after the start of the chemotherapy. Streptococcal septicemia was not limited to patients treated with cytosine arabinoside but also occurred in patients treated with other regimens of intensive chemotherapy. In 28 episodes there were no focal signs of infection, but in half there were symptoms of treatment induced gastrointestinal toxicity. The streptococci probably invade through oral and gastrointestinal mucosa damaged by the chemotherapy. Selective decontamination may play a promoting role.

Adult↗
PubMed1990

Detection of Haemophilus influenzae in cerebrospinal fluids by polymerase chain reaction DNA amplification.

Two primer sets were chosen for the detection of Haemophilus influenzae in cerebrospinal fluid by polymerase chain reaction (PCR) DNA amplification. One primer set was selected from sequences encoding a capsulation-associated protein and reacted with target DNA from all 15 capsulate H. influenzae strains (all serotypes) examined. The other primer set was selected from the DNA sequence of a gene encoding for outer-membrane protein P6 and reacted with the 15 capsulate and 10 non-capsulate strains of H. influenzae tested. This primer set also reacted with the closely related species H. haemolyticus and H. aegyptius, and with two of nine H. parainfluenzae strains. In reconstruction experiments, PCR DNA amplification was able to detect as few as five H. influenzae cells when 40 cycles of amplification were used. Two hundred cerebrospinal fluid (CSF) samples collected consecutively from patients suffering from meningitis were investigated by PCR; 40 were culture-positive for H. influenzae and 39 of these were also clearly positive in the PCR test with both primer sets. Contamination occurred to some extent with 40 cycles of amplification but was completely eliminated when the number of cycles was reduced to 35. We conclude that the two primer sets are appropriate for the detection of H. influenzae by PCR, each having its own specificity. When these two primer sets are used, PCR is a technique of equivalent sensitivity to culture for the detection of H. influenzae in CSF.

Base Sequence↗
PubMed1989

Nonculture detection of Haemophilus influenzae in sputum with monoclonal antibodies specific for outer membrane lipoprotein P6.

Isolation of Haemophilus influenzae from sputum is hampered by overgrowth by other microorganisms or by antibiotic treatment of the patient. To overcome this problem in the detection of H. influenzae, an in situ immunoperoxidase staining technique was developed with monoclonal antibody (MAb) 8BD9, immunoglobulin subclass G2a. MAb 8BD9 appeared to be directed to an epitope on the outer membrane lipoprotein P6 of H. influenzae. The species specificity of MAb 8BD9 was analyzed by staining isolates from different bacterial species. MAb 8BD9 reacted with all 300 H. influenzae strains tested and with H. aegyptius and H. haemolyticus. Twenty-six of 30 H. parainfluenzae strains, other Haemophilus species, and other bacterial species often isolated from sputum were not stained. The staining technique was compared with culture of 845 routinely obtained sputum samples from patients with respiratory tract infections. In 829 sputa (98.1%), the results of both techniques were in agreement; 173 were positive for H. influenzae, and 656 were negative. With 14 sputum samples, the staining method gave a positive result for H. influenzae, but the bacterium was not cultured. This could be ascribed to antibiotic treatment of the patient (n = 7), the presence of other MAb 8BD9-positive Haemophilus species in the sputum (n = 5), and overgrowth by swarming Proteus mirabilis or by Branhamella catarrhalis. In the immunoperoxidase- and Gram-stained smears of two sputum samples, no bacteria were seen, although some H. influenzae was cultured. On the basis of these results, we conclude that immunoperoxidase staining with MAb 8BD9 is a fast and reliable extension of the available detection techniques for H. influenzae.

Antibodies, Monoclonal↗
PubMed1989

Genetic typing in a cluster of Legionella pneumophila infections.

Legionella pneumophila strains isolated from six patients, three air-conditioning- and cooling tower-derived strains, and three hot water supply-derived strains were analyzed by three genetic typing methods. The results of the whole-cell DNA restriction endonuclease analysis and the restriction patterns based on genes coding for rRNA correlated with each other and demonstrated that the patient isolates were indistinguishable from the air-conditioning- and cooling tower-derived isolates but differed markedly from the hot water supply-derived isolates. The patient and air-conditioning- and cooling tower-derived strains contained plasmids of the same molecular weight; the hot water supply-derived strains were plasmidless. These results indicated that the cooling tower or the air-conditioning system was the environmental source for the examined cluster of Legionnaires disease strains.

Air Conditioning↗
PubMed1988

Similar DNA restriction endonuclease profiles in strains of Legionella pneumophila from different serogroups.

DNA of strains of Legionella pneumophila serogroups 1, 3, 4, and 6, isolated from patients and environmental sources, was examined by restriction endonuclease analysis (REA). Major differences in profiles enabled subtyping in many strains with the same serogroup antigen. However, a cluster of L. pneumophila strains, originating from all the examined serogroups, had similar restriction endonuclease profiles, sometimes with minor differences. This suggests that the genetic similarity between strains of L. pneumophila of different serogroups is sometimes closer than in strains with the same serogroup antigen. Seven environmental sources harbored two L. pneumophila strains with various serogroup antigens; six sources had similar restriction endonuclease profiles. The resolution of small differences in profiles is hampered in REA by the great magnitude of DNA fragments; even upon extensive analysis, these differences are not always readily visualized. Double digestions with the restriction enzymes HpaI and HpaII showed the best results and sometimes revealed differences not evident by digestions with a single endonuclease. REA has a great capacity for accurate epidemiological typing of L. pneumophila, in addition to classical serogrouping; it appeared that the results of the two techniques do not necessarily correlate. On the other hand, it should be stressed that small differences in profiles are not easily detected by REA.

DNA Restriction Enzymes↗