Pulse field gel electrophoresis: Lane 1 Lamda marker; lanes 2 to 5 K pneumoniae isolates from cases 3 to 6; lane 6 isolate from case 7; lane 7 ESBL negative K pneumoniae control; lane 8 ESBL positive K pneumoniae control. Pulse field gel electrophoresis: Lane 1 Lamda marker; lanes 2 to 5 K pneumoniae isolates from cases 3 to 6; lane 6 isolate from case 7; lane 7 ESBL negative K pneumoniae control; lane 8 ESBL positive K pneumoniae control. Jennifer Royle et al. Arch Dis Child Fetal Neonatal Ed 1999;80:F64-F68 Copyright © BMJ Publishing Group Ltd & Royal College of Paediatrics and Child Health. All rights reserved.