389 in our laboratory of samples from the same batches were negative. None of the affected babies was exclusively suckled. Of those breast fed, all took expressed breast milk at some stage, and samples were negative at that time. Later Cl. butyricum was isolated from the trap of the breast pump and the tubing distal to it, but not from the collecting bottle and tubing or breast shield. There should be no backflow from the trap into the expressed milk and we do not know the significance of the finding. The organism has also been isolated from the hypochlorite solution (1% ’Milton’) used to disinfect rubber teats, although only after 12 h use, and from the floor of the special-care baby unit. Although we believe that Cl. butyricum is important in the pathogenesis of necrotising enterocolitis (N.E.C.) we are not yet able to differentiate between a newly introduced, especially invasive strain of the organism and a ubiquitous strain rendered more pathogenic, perhaps because of some enhancing factor such as chemical alteration in the ingested milk (hence our inquiry into the possible ingestion of abnormal substances by the cattle from which the ’SMA’ was manufactured). We were interested to see the letter from Dr Gothefors and Mr Blenkharn (Jan. 7, p. 52). We agree that Cl. butyricum is reported to be non-toxigenic but we know of no work, based on advanced methods of analysis, which substantiates this

preparations, and examination

Serum concentrations of nortriptyline. Venous blood

(0) and

in blood

from the outlet blood line (8) during

hmmoperfusion. Charcoal

hxmoperfusion, although moderately effective as the extraction ratio of nortriptyline across the apparatus, does not remove significant amounts of the drug from the body. judged by

Renal Unit, Medical Department A, and Clinical Pharmacology Unit, Laboratory of Clinical Biochemistry, Haukeland Sykehus,

BJARNE M. IVERSEN YNGVAR WILLASSEN OLAV M. BAKKE

Bergen, Norway

CLOSTRIDIA IN NECROTISING ENTEROCOLITIS

SIR,-Two features of the necrotising enterocolitis (N.E.C.) described

al. suggest the possibility of a comof contaminated solutions. 7 of the 12 affected babies were otherwise normal full-term infants, and the 5 premature babies were otherwise well at the time of onset of N.E.C. The spontaneous syndrome of N.E.C. usually presents in sick, premature babies. Although Howard et al. suggest that loss of natural factors from breast milk during artificial feeding may have been responsible, many of the affected babies had been having some breast feeding immediately before the onset of rr. E. c. Might not the Clostridium butyricum which seemed to cause the outbreak of N.E.C. have been acquired in the newborn nursery from a common source? A common source for infection can be difficult to detect, as we and others have found.2 Such a mechanism would not detract from the main point of the article-namely, that Cl. butyricum may be a cause of N.E.c.-but it would explain the appearance of a cluster of cases in all of which this organism was implicated. mon

by

Howard

source, such

as

et

ingestion

Veterans Administration Hospital, Houston, Texas 77031, U.S.A.

*