Isolation of Enterobacter sakazakii from Midgut of Stomoxys calcitrans

To the Editor: Enterobacter saka-zakii, a gram-negative rod-shaped bacterium, is an emerging foodborne pathogen that can cause meningitis, sepsis, or necrotizing enterocolitis in newborns, particularly affecting premature or other immunocompromised infants. Although an environmental reservoir and mode of transmission for E. sakazakii has not been clearly identified, a growing number of reports suggest that powdered milk–based infant formulas can be a vehicle for infection. We report the isolation of E. sakazakii from the guts of larvae of the stable fly, Stomoxys calcitrans, demonstrating an environmental reservoir for E. sakazakii and raising the possibility that environmental contamination by insects may be important in the spread of this opportunistic organism. The first two cases of neonatal meningitis caused by E. sakazakii were reported in the United Kingdom in 1961; both infants died (1). Subsequently, cases of meningitis, septicemia, necrotizing enterocolitis, brain abscesses, cerebral infarctions and dermoid cysts of the posterior fossa caused by E. sakazakii have been reported worldwide. Although most documented cases involve infants, reports also describe adult infections. Adults with E. sakazakii infections usually have serious underlying diseases or malignan-cies, but adult meningitis caused by E. sakazakii infection has never been reported. Concern is growing regarding antibiotic resistance in E. sakaza-kii. Recently, an E. sakazakii wound infection in an adult patient has been reported, which was resistant to multiple antibiotics and required prolonged treatment with broad-spectrum antibiotics (2). Illness and death associated with E. sakazakii infection in neonates vary considerably, and mortality rates as high as 80% have been recorded (3). Implicated infection sources include incubators, the birth canal, a blender in a milk kitchen where powdered infant formula was reconstituted and hospital environments (E. sakazakii growth on an agar plate in a ward specifically under infection control against multidrug-resistant Staphylococcus aureus [MRSA]). The presence of E. sakazakii in powdered infant formula has been reported often. An investigation of Entero-bacteriaceae found in powdered substitutes for breast milk from 35 countries indicated that 52.2% of the 141 samples tested contained members of this family. E. agglomerans, E. cloa-cae, E. sakazakii, and Klebsiella pneu-moniae were the most frequently isolated organisms (4). More recently, E. sakazakii has been detected in ultra–heat-treated milk, spoiled tofu, lettuce, and traditional fermented bread (khamir), and in beer mugs rinsed mechanically or in open vats. Although more vehicles for transmission are being identified, the environmental reservoir has remained elusive. A study in 1990 did not isolate this organism …