ABSTRACT. Serratia marcescens is a Gram negative rod which for a century and a half was considered a harmless saphrophyte. However, medical technology and the use of antibacterial agents have created ecological niches for this bacterium, which is now a medical problem. The bacterium is encountered in connection with contact lens keratitis, often associated with contaminated contact lens solutions. The concentrations of chlorhexidin and thiomersal required in contact lens solution to suppress the bacterium have been proved toxic to the eye. Modern contact lens solutions with biguanids have rapid killing kinetics, while in solutions with polyquaternium S. marcescens can survive in reduced numbers for up to 72 hours. The adherence of a specific isolate of Serratia to hydrogel lenses increased with decreased water content of the lenses. However, there has been no correlation between hydrophobicity markers or hemagglutinins and adherence to contact lenses or urinary tract epithelium. When handling medical plastic devices, such as contact lenses, strictly inforced hygiene remains the most important method to combat environmental bacteria such as Serratia marcescens.

In March 1999, an outbreak of gastroenteritis occurred affecting 30 day-care centres served by the same caterer. A retrospective cohort study was performed in 13 randomly selected day-care centres to determine the source and mode of transmission. Electron microscopy and PCR were used to verify the diagnosis. The overall attack rate (AR) was 37% (195/524): 30% in children and 62% in adults. Modified by the age of the patient, eating pumpkin salad served on 1 March was associated with becoming an early case (odds ratio = 3.9; 95% confidence interval 1.8-8.8). No significant association was found between food consumption and becoming a late case. The primary food-borne AR was 27% and the secondary AR was 14%. The same genotype of Norwalk-like virus was found in 5 cases and in 1 ill and 1 asymptomatic food-handler. Contamination by 1 of the food-handlers seems the most likely route of spread of the virus and underlines the importance of strict hygienic routines.

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Samples of five different solutions for disinfection of soft contact lenses were experimentally inoculated with a strain of Pseudomonas aeruginosa or Serratia marcescens. No bacteria could be detected after one hour in solutions with biguanids, while they survived in reduced number up to 72 h in solutions with polyquaternium as active substance. However, prolonged survival after one week could not be detected. Lenses treated with polyquaternium based contact lens disinfectant solutions overnight may still harbour bacteria, which might increase the risk for bacterial complications, such as keratitis.

Universal varicella-zoster virus (VZV) childhood vaccination is still debated, but adult chickenpox may be severe. It could be prevented by vaccination of seronegative adolescents. This study aimed to determine the feasibility of coadministration of a VZV vaccine and the measles-mumps-rubella (MMR) booster at 12 y of age. Guardians of 1231 12-y-old pupils where asked about the history of chickenpox in their children. 190 had no chickenpox history and 12 of 62 of them lacked VZV antibodies. Additional history-negative children were also recruited. 199 history-positive children received only MMR and 98 history-negative children received an MMR vaccine and a VZV vaccine. Serum samples were drawn before vaccination and after 8 weeks. Viral antibodies were measured by immunofluorescence (VZV) and enzyme-linked immunosorbent assays (VZV, MMR). All 184 history-positive children tested had VZV antibodies. 17/89 VZV-vaccinated and tested children (19%) lacked VZV antibodies before vaccination. 12 (71%) seroconverted after 1 dose. Cell-mediated immunity (CMI) against varicella was tested in 3/5 children who did not seroconvert after 1 dose of VZV vaccine. They seroconverted after a second dose and had measurable CMI. VZV vaccination did not affect the MMR response and there were no severe side-effects. A history of varicella infection, as reported by the guardian, is reliable, but a negative history was incorrect in 81% of the cases. This population of 12-y-old children may require 2 doses of VZV vaccine, at least when given simultaneously with the MMR vaccine.