Hospital outbreak of trimethoprim resistance in pathogenic coliform bacteria.

In an investigation of outbreak of infection caused by coliform bacilli with plasmid-mediated trimethoprim (TMP) resistance many patients were found to be asymptomatic carriers of TMP-resistant coliform bacilli. Analysis of factors predisposing to rectal carriage of these organisms showed that the most important was previous treatment with co-trimoxazole, a sulphonamide, or ampicillin. The outbreak was controlled by a policy restricting the antibiotics given. Geriatric units are an important source of hospital infection. When an outbreak occurs the logical sequence of steps to be taken is to monitor cases, identify the outbreaks, analyse the causative factors, plan corrective action jointly with laboratory staff, and monitor the outcome.