Abstract
ObjectiveToxin-producing Klebsiella oxytoca causes antibiotic-associated haemorrhagic colitis (AAHC). The disease-relevant cytotoxins tilivalline and tilimycine produced by certain K. oxytoca isolates are encoded by the non-ribosomal peptide synthetase genes A (npsA) and B (npsB). In this study, the new LightMix® Modular kit for the detection of relevant K. oxytoca sensu lato (s.l.) toxin genes was evaluated. MethodsDNA was extracted on the automated EMAG® platform. Amplification was done on the Light Cycler® 480 II instrument. In total, 130 residual faecal specimens collected from patients with antibiotic-associated diarrhoea were studied to determine the clinical sensitivity and specificity. Toxigenic culture served as reference method. ResultsWith the new kit, the limit of detection was 15 CFU/mL for all targets. For the pehX target specific to K. oxytoca s.l., 65 of 130 clinical specimens were positive, while toxin-specific targets (npsA/npsB) were positive in 47 of 130. The npsA/npsB PCR targets showed a clinical sensitivity of 100% (95%CI 80.5–100%) and a specificity of 73.5% (95%CI 64.3–81.3%) with a positive predictive value of 16.5% (95%CI 12.7–21.2%) and a negative predictive value of 100%. ConclusionCompared with culture, additional clinical specimens positive for K. oxytoca s.l. were detected with real-time PCR. The specificity of the toxin targets appears moderate due to the inferior sensitivity of the culture-based reference method. Since the developed assay is highly sensitive, it may be used as first-line method to improve the diagnosis of AAHC.
Highlights
Antibiotic-associated diarrhoea (AAD) occurs in 5-35% of patients receiving antibiotic therapy
Klebsiella oxytoca was identified as another causative agent of antibiotic-associated haemorrhagic colitis (AAHC)
Key enzymes for tilimycin synthesis are two nonribosomal synthetases encoded by the genes non-ribosomal peptide synthetase genes A (npsA) and npsB [8,9]
Summary
Antibiotic-associated diarrhoea (AAD) occurs in 5-35% of patients receiving antibiotic therapy. Klebsiella oxytoca was identified as another causative agent of antibiotic-associated haemorrhagic colitis (AAHC). This special form of AAD presents with bloody diarrhoea and segmental colitis mainly during therapy with beta-lactam antibiotics, especially penicillins [3,4]. In Europe, the prevalence of toxin producing K. oxytoca in healthy individuals is reported in a range from 2 to 9% [3,4]. K. oxytoca is naturally resistant to penicillins; antibiotic therapy results in an overgrowth of this bacterium with subsequent overproduction of the toxins tilimycin and tilivalline causing severe tissue damage. It has been demonstrated that those cytotoxins are the causative mechanism for the development of AAHC [10,11]
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