Outbreak of coagulase negative staphylococcus highly resistant to ciprofloxacin in a leukaemia unit

Abstract

Objective - To define an outbreak of bacteraemia due to coagulase negative staphylococci highly resistant to ciprofloxacin in a leukaemia unit, investigate the source and mode of spread of the outbreak strain, and assess control measures. Design - The outbreak strain was characterised by five different typing methods. Surveillance of patients, staff, and environment was carried out during the outbreak and five months after control measures were introduced. Setting - A unit with 10 beds for adults with leukaemia and patients receiving bone marrow transplants. The outbreatk occurred during a trial of ciprofloxacin for empirical treatment of neutropenic fevers. Interventions - Ciprofloxacin was withdrawn from use in the unit and daily bathing with chlorhexidine gluconate solution started. Main outcome measure - The absence of bacteraemia due to the outbreak strain for five months after control measures. Results - During the study 49 patients developed 21 episodes of bacteraemia due to the outbreak strain, which was ciprofloxacin resistant (minimum inhibitory concentration ≥ 128 mg/l), susceptible to phage 155 A9C, and SII biotype and had characteristic immunoblot and DNA fingerprint features. There was a high amount of colonisation of patients but not staff with this strain, which was also widespread in the environment. The control measures led to rapid resolution of the outbreak and disappearnace of the strain from the unit. Conclusions - In areas where coagulase negative staphylococcal infections are common doctors must be aware of the possibility of cross infection with a single strain, and the availability of more discriminatory methods of typing will facilitate the identification and control of such episodes.