Environmental analysis in the workplace; development of airborne monitoring systems for potentially harmful pharmaceuticals: An improved rapid ELISA for ceftazidime

Ceftazidime is a β-lactam antibiotic of the cephalosporin family. In common with other β-lactam antibiotics it is a respiratory sensitiser and occupational exposure limits have been set for workers who may inhale the drug in the workplace. Polyclonal antibodies have been raised in rabbits which specifically recognise this compound. These have been purified using immunoaffinity chromatography and the resulting anti-drug antibodies used with alkaline-phosphatase labelled anti-rabbit antibodies to generate a single reagent ELISA for ceftazidime which can be used in a rapid semi-quantitative mode to screen samples from conventional filters following monitoring of worker exposure. Presence of the drug in excess of the occupational exposure limit (OEL) (3 μg of captured ceftazidime eluted into 1 ml prior to assay) results in a lack of colour at the endpoint of the assay while samples with levels less than the OEL produce a yellow colour. The ELISA can process 45 samples in duplicate in 40 min. The sensitivity of the assay is 110 pg in a 50 μl sample volume. The assay has good precision with coefficients of variation less than 10% and it exhibits insignificant interference with a range of penicillin and cephalosporin antibiotics and other compounds tested. The assay is better suited than liquid chromatography for use on site by semi-skilled operatives immediately following the monitoring period when exposure of workers above the OEL can be rapidly ascertained and action taken.