Members of the family Enterobacteriaceae were cultured from 52.5% of 141 milk substitute infant formulas which were obtained in 35 countries. The concentration did not exceed a level of 1 CFU/g in any product. The species which were isolated most frequently were Enterobacter agglomerans, Enterobacter cloacae, Enterobacter sakazakii, and Klebsiella pneumoniae. If infections due to these organisms occur, it can be useful to include a check of the hygienic precautions which are taken during the preparation and storage of the formula. Milk powders without members of the Enterobacteriaceae might offer extra protection to the newborn if some multiplication does occur in the formula.

Eight cases of neonatal meningitis due to Enterobacter sakazakii (formerly known as yellow-pigmented Enterobacter cloacae) which occurred in The Netherlands during the last 6 years were investigated retrospectively. Two patients had necrotizing enterocolitis and meningitis simultaneously. Despite treatment (in most cases with ampicillin and gentamicin), the fatality rate was 75%. Strains were much more susceptible to some of the new beta-lactam antibiotics than to ampicillin. A mode of transmission other than passage through the birth canal was likely, at least for some patients. A cluster of four patient strains in one hospital had almost identical plasmid DNA profiles. However, two strains isolated from formula at the same hospital 2 days after the onset of one case had different profiles, as did the strains from patients in other hospitals.

Summary: Topical mupirocin was routinely applied to insertion sites of central venous catheters (CVC) of neonates in a neonatal intensive care unit. After five years, mupirocin resistance was recorded in 42% of clinical isolates of coagulase-negative staphylococci (CNS). This decreased to 21% during a mupirocin-free interval of five months. We performed a prospective study on the significance of mupirocin use on the staphylococcal skin flora of 15 newly admitted neonates. During treatment, mupirocin-susceptible strains were replaced by highly resistant ones. After treatment, all but one neonate harboured at least one resistant strain; 29% of all strains were moderately resistant (mupirocin minimum inhibitory concentrations (MICs) 16mg/L) and 55% were highly resistant (MICs >1024mg/L). One CVC (7%) became colonized with a resistant strain, One year after stopping routine mupirocin application the incidence of resistance had dropped to 13%; CVC colonization was recorded in 2*4%.

An agar dilution method was used to measure the minimal inhibitory concentrations of ciprofloxacin (Bay o 9867), norfloxacin, pipemidic acid, and nalidixic acid against 496 clinical isolates. Ciprofloxacin and norfloxacin were active against all species tested (90o minimal inhibitory concentrations c 8 ,ug/ml), although ciprofloxacin was somewhat more active, e.g., against gram-positive cocci. Pipemidic acid and nalidixic acid were active against most of the members of the Enterobacteriaceae, but Klebsiella species and Providencia stuartii were only inhibited by a high concentration of nalidixic acid.

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