Peter H J van Keulen

Publications (7)78.68 Total impact

• Source

  Available from: PubMed Central

  Article: Methicillin-resistant Staphylococcus aureus in meat products, the Netherlands.

  Inge H M van Loo, Bram M W Diederen, Paul H M Savelkoul, Joyce H C Woudenberg, Robert Roosendaal, Alex van Belkum, Nicole Lemmens-den Toom, Carlo Verhulst, Peter H J van Keulen, Jan A J W Kluytmans
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  ABSTRACT: A new methicillin-resistant Staphylococcus aureus (MRSA) clone related to pig and cattle farming was detected in the Netherlands. We investigated the extent of S. aureus presence in meat and found 36 S. aureus strains in 79 samples. Two strains were MRSA; 1 was multilocus sequence type 398, the clone related to farming.
  Emerging infectious diseases 12/2007; 13(11):1753-5. · 6.17 Impact Factor
• Article: Comparative evaluation of the VITEK 2, disk diffusion, etest, broth microdilution, and agar dilution susceptibility testing methods for colistin in clinical isolates, including heteroresistant Enterobacter cloacae and Acinetobacter baumannii strains.

  Jerome R Lo-Ten-Foe, Anne Marie G A de Smet, Bram M W Diederen, Jan A J W Kluytmans, Peter H J van Keulen
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  ABSTRACT: Increasing antibiotic resistance in gram-negative bacteria has recently renewed interest in colistin as a therapeutic option. The increasing use of colistin necessitates the availability of rapid and reliable methods for colistin susceptibility testing. We compared seven methods of colistin susceptibility testing (disk diffusion, agar dilution on Mueller-Hinton [MH] and Isosensitest agar, Etest on MH and Isosensitest agar, broth microdilution, and VITEK 2) on 102 clinical isolates collected from patient materials during a selective digestive decontamination or selective oral decontamination trial in an intensive-care unit. Disk diffusion is an unreliable method to measure susceptibility to colistin. High error rates and low levels of reproducibility were observed in the disk diffusion test. The colistin Etest, agar dilution, and the VITEK 2 showed a high level of agreement with the broth microdilution reference method. Heteroresistance for colistin was observed in six Enterobacter cloacae isolates and in one Acinetobacter baumannii isolate. This is the first report of heteroresistance to colistin in E. cloacae isolates. Resistance to colistin in these isolates seemed to be induced upon exposure to colistin rather than being caused by stable mutations. Heteroresistant isolates could be detected in the broth microdilution, agar dilution, Etest, or disk diffusion test. The VITEK 2 displayed low sensitivity in the detection of heteroresistant subpopulations of E. cloacae. The VITEK 2 colistin susceptibility test can therefore be considered to be a reliable tool to determine susceptibility to colistin in isolates of genera that are known not to exhibit resistant subpopulations. In isolates of genera known to (occasionally) exhibit heteroresistance, an alternative susceptibility testing method capable of detecting heteroresistance should be used.
  Antimicrobial Agents and Chemotherapy 11/2007; 51(10):3726-30. · 4.84 Impact Factor
• Article: Pseudo-outbreak of hepatitis B virus infection associated with contamination of a semiautomatic cap remover.

  Bram M W Diederen, Carlo Verhulst, Annemarie van't Veen, Peter H J van Keulen, Jan A J W Kluytmans
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  ABSTRACT: A pseudo-outbreak of hepatitis B virus caused by cross-contamination from a semiautomatic cap remover for blood collection tubes is reported. The source of the outbreak was elucidated by using basic epidemiological methods. Laboratories should always be critical about their results in order to identify contamination problems.
  Infection Control and Hospital Epidemiology 12/2006; 27(11):1258-60. · 3.67 Impact Factor
• Source

  Available from: Jan Kluytmans

  Article: Performance of MRSA ID, a new chromogenic medium for detection of methicillin-resistant Staphylococcus aureus.

  Bram M W Diederen, Marie-Louise van Leest, Inge van Duijn, Piet Willemse, Peter H J van Keulen, Jan A J W Kluytmans
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  ABSTRACT: MRSA ID was evaluated for its ability to identify methicillin-resistant Staphylococcus aureus. A well-defined collection of staphylococci was used (n = 998). The sensitivity after 24 h was 96.4%, increasing to 98.8% after 48 h. The specificity was 98.2% after 24 h and decreased to 89.7% after 48 h.
  Journal of Clinical Microbiology 03/2006; 44(2):586-8. · 4.15 Impact Factor
• Source

  Available from: Jan Kluytmans

  Article: Emergence and persistence of macrolide resistance in oropharyngeal flora and elimination of nasal carriage of Staphylococcus aureus after therapy with slow-release clarithromycin: a randomized, double-blind, placebo-controlled study.

  Hans F Berg, Jeroen H T Tjhie, Gert-Jan Scheffer, Marcel F Peeters, Peter H J van Keulen, Jan A J W Kluytmans, Ellen E Stobberingh
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  ABSTRACT: To investigate the effect of slow-release (SR) clarithromycin on colonization and the development of resistance in oropharyngeal and nasal flora, a double-blind, randomized, placebo-controlled trial was performed with 8 weeks of follow-up. A total of 296 patients with documented coronary artery disease were randomized in the preoperative outpatient clinic to receive a daily dose of SR clarithromycin (500 mg) (CL group) or placebo tablets (PB group) until the day of surgery. Nose and throat swabs were taken before the start of therapy, directly after the end of therapy, and 8 weeks later. The presence of potential pathogenic bacteria was determined, and if they were isolated, MIC testing was performed. Quantitative culture on media with and without macrolides was performed for the indigenous oropharyngeal flora. In addition, analysis of the mechanism of resistance was performed with the macrolide-resistant indigenous flora. Basic patient characteristics were comparable in the two treatment groups. The average number of tablets taken was 15 (standard deviation = 6.4). From the throat swabs, Haemophilus parainfluenzae was isolated and carriage was not affected in either of the treatment groups. Nasal carriage of Staphylococcus aureus, however, was significantly reduced in the CL group (from 35.3 to 4.3%) compared to the PB group (from 32.4 to 30.3%) (P < 0.0001; relative risk [RR], 7.0; 95% confidence interval [CI], 3.1 to 16.0). Resistance to clarithromycin was present significantly more frequently in H. parainfluenzae in the CL group after treatment (P = 0.007; RR, 1.6; 95% CI, 1.1 to 2.3); also, the percentage of patients with resistance to macrolides in the indigenous flora after treatment was significantly higher in the CL group (31 to 69%) (P < 0.0001; RR, 1.9; 95% CI, 1.4 to 2.5). This persisted for at least 8 weeks. This study shows that besides the effective elimination of nasal carriage of S. aureus, treatment with SR clarithromycin for approximately 2 weeks has a marked and sustained effect on the development of resistance in the oropharyngeal flora for at least 8 weeks.
  Antimicrobial Agents and Chemotherapy 12/2004; 48(11):4183-8. · 4.84 Impact Factor
• Source

  Available from: Andreas Voss

  Article: Mupirocin prophylaxis against nosocomial Staphylococcus aureus infections in nonsurgical patients: a randomized study.

  Heiman F L Wertheim, Margreet C Vos, Alewijn Ott, Andreas Voss, Jan A J W Kluytmans, Christina M J E Vandenbroucke-Grauls, Marlene H M Meester, Peter H J van Keulen, Henri A Verbrugh
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  ABSTRACT: Staphylococcus aureus nasal carriage is a major risk factor for nosocomial S. aureus infection. Studies show that intranasal mupirocin can prevent nosocomial surgical site infections. No data are available on the efficacy of mupirocin in nonsurgical patients. To assess the efficacy of mupirocin prophylaxis in preventing nosocomial S. aureus infections in nonsurgical patients. Randomized, double-blind, placebo-controlled trial. 3 tertiary care academic hospitals and 1 nonacademic hospital. 1602 culture-proven S. aureus carriers hospitalized in nonsurgical departments. Therapy with mupirocin 2% nasal ointment (n = 793) or placebo ointment (n = 809), twice daily for 5 days, started 1 to 3 days after admission. Nosocomial S. aureus infections according to defined criteria, in-hospital mortality, duration of hospitalization, and time to nosocomial S. aureus infection. Staphylococcus aureus isolates were genotyped to assess whether infection was caused by endogenous strains. The mupirocin and placebo groups did not statistically differ in the rates of nosocomial S. aureus infections (mupirocin, 2.6%; placebo, 2.8%; risk difference, 0.2 percentage point [95% CI, -1.5 to 1.9 percentage points]), mortality (mupirocin, 3.0%; placebo, 2.8%; risk difference, -0.2 percentage point [CI, -1.9 to 1.5 percentage points]), or duration of hospitalization (median for both, 8 days). However, time to nosocomial S. aureus infection was decreased in the mupirocin group from 12 to 25 days (P > 0.2). A total of 77% of S. aureus nosocomial infections were endogenous. A few infections in both groups may have been missed because investigators assessed a patient for infection only if microbiology culture results were positive for S. aureus. Routine culture for S. aureus nasal carriage at admission and subsequent mupirocin application does not provide effective prophylaxis against nosocomial S. aureus infections in nonsurgical patients.
  Annals of internal medicine 03/2004; 140(6):419-25. · 16.73 Impact Factor
• Article: Risk and outcome of nosocomial Staphylococcus aureus bacteraemia in nasal carriers versus non-carriers.

  Heiman F L Wertheim, Margreet C Vos, Alewijn Ott, Alex van Belkum, Andreas Voss, Jan A J W Kluytmans, Peter H J van Keulen, Christina M J E Vandenbroucke-Grauls, Marlene H M Meester, Henri A Verbrugh
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  ABSTRACT: Staphylococcus aureus is the second most frequent cause of nosocomial blood infections. We screened 14008 non-bacteraemic, non-surgical patients for S aureus nasal carriage at admission, and monitored them for development of bacteraemia. Nosocomial S aureus bacteraemia was three times more frequent in S aureus carriers (40/3420, 1.2%) than in non-carriers (41/10588, 0.4%; relative risk 3.0, 95% CI 2.0-4.7). However, in bacteraemic patients, all-cause mortality was significantly higher in non-carriers (19/41, 46%) than in carriers (seven/40, 18%, p=0.005). Additionally, S aureus bacteraemia-related death was significantly higher in non-carriers than in carriers (13/41 [32%] vs three/40 [8%], p=0.006). S aureus nasal carriers and non-carriers differ significantly in risk and outcome of nosocomial S aureus bacteraemia. Genotyping revealed that 80% of strains causing bacteraemia in carriers were endogenous.
  The Lancet 364(9435):703-5. · 38.28 Impact Factor