Objective The diagnosis of sepsis in a twin presents a clinical dilemma regarding optimal management of the apparently well co-twin. The authors present the case of extremely preterm twins who both developed life-threatening coliform sepsis in second postnatal week within a short time period of each other.

Methods Case report.

Results Dichorionic diamniotic twins were delivered vaginally at 27 weeks' gestation following spontaneous onset of labour. Twin 2 presented with overt signs of sepsis on day 10 and required reventilation. At this time, twin 1 was not treated with antibiotics because she was clinically well and C-reactive protein was normal. However, 34 h later she also developed life-threatening Escherichia coli septicaemia, including meningitis. Serious complications ensued, including pulmonary haemorrhage, hypotension, impaired renal function, thrombocytopenia, necrotising enterocolitis with intestinal perforation and digital ischaemic injury. The E coli strain isolated from the blood of twin 2, and both blood and CSF of twin 1 had similar antibiotic susceptibility patterns. Typing confirmed the same strains of E coli in both twins, namely, serotype 031 K1. Perinatal colonisation of the organism was suspected.

Conclusions This case supports concurrent evaluation and consideration of empirical antibiotic treatment of an apparently well preterm co-twin when a twin sibling presents with late-onset sepsis within the first 2 weeks postnatal. Reliance solely on enhanced clinical surveillance for infection in an asymptomatic twin may be insufficient.