[Poliovirus uptake into and excretion from oysters: a model experiment for elimination of Norwalk-like viruses from oysters].

Outbreaks of gastroenteritis caused by Norwalk-like viruses are often induced by the consumption of raw shellfish such as oysters. Incidences reach a peak during the cold season in Japan, when seawater temperatures fall below 10 degrees C. We investigated oysters' uptake and excretion of viruses, over varying lengths of exposure, monitoring the effects of changes in temperature and flow rate of seawater, and the presence of plankton. The study was performed using a poliovirus and an experimental circulatory system, which was framed on the same principle as a model practically used for the depuration of oysters. Polioviruses present in the seawater were taken rapidly into the midgut gland of oysters. However, virus levels detected in oysters at both 10 degrees C and 20 degrees C were decreased to approximately 1/1,000 to 1/10,000 within 6 hrs after the circulatory seawater was replaced by UV irradiated seawater. These results demonstrate the effectiveness of the circulatory depuration system for the elimination of poliovirus from oysters, and indicate that controlling the temperature and flow rate of the circulatory system could decrease the risk of NLV infection.

[Two nosocomial outbreaks of sepsis caused by Serratia marcescens, which occurred in July 1999 and January 2002--Tokyo].

Two nosocomial outbreaks of sepsis caused by Serratia marcescens, which occurred in Tokyo were the following cases. CASE A: In July 1999, 10 inpatients admitted to the third floor ward of the General Hospital A, developed sudden onset of high fever, coagulation disorders (disseminated intravascular coagulation), and acute renal failure, of which 5 died. Twenty-one strains of Serratia marcescens were isolated from the inpatient's blood and urine, nurse fingers and environmental samples from floor and cooling tower. Serratia infection was strongly suspected as the cause of sepsis. These cases were defined as "inpatients who developed fever 38 degrees C or more during July 26 to 29 and from whom S. marcescens was isolated by blood culture". Ten isolates were detected from the blood. In order to investigate the background of S. marcescens isolation in the hospital and to compare molecular and biochemical characteristics of S. marcescens, cultures were attempted from samples of other inpatients and staffs and hospital environment. Those were classified into 9 groups by various different typings: biotyping with Api Rapid 20; susceptibility typing of antimicrobial agents tested; pulsed-field gel electrophoresis (PFGE) typing of SpeI- or Xba I-restricted chromosome. All 10 isolates causing sepsis were found to be in the same group. CASE B: In January 2002, 24 inpatients, admitted to Neurosurgical Hospital B, developed sudden onset of high fever, of which 7 died. S. marcescens was isolated from a towel, environmental samples and inpatients. These cases were defined as "inpatients who developed fever of 38.5 degrees C and S. marcescens isolated by blood culture". Twelve strains were isolated from the blood samples in 12 cases. In order to investigate the background of S. marcescens isolation in the hospital, cultures were attempted from other inpatient's urine and environmental samples from medical tape, Tshake and a towel. These isolates were classified into 3 groups by the previous typings; biotyping with Api Rapid 20; susceptibility typing of antimicrobial agents tested; and PFGE typing. All 12 isolates in 12 cases were found to be in the same group. These cases of 2 nosocomial outbreaks of sepsis were defined as "in-patient who developed high fever and S. marcescens isolated by blood culture". However in both cases transmission routes of Serratia infection remain unknown by field investigation.

Experimental confirmation of Serratia marcescens contamination in multiple-dose vials of heparin-saline solution.

The initial contamination of heparin-saline solution (HS) in multiple-dose vials (MDVs) by Serratia marcescens was experimentally investigated using various isolates. Isolates I2 and S1 were from blood specimens from patients with a hospital-acquired infection (HAI). Isolates I13 and FHSM9043 were from urine and blood specimens, respectively, from patients without HAI. Isolate I124, with a pulsed-field get electrophoresis pattern identical to that of isolate I2, was from the hospital environment. Viable cells of isolate I2 were carried over into the HS of MDVs when the contaminated rubber septum was pierced with a syringe needle. When the outside surface of the septum was contaminated by inoculating it with wet-cell suspensions in HS or Müller-Hinton broth, the viable cells carried over were detected at a minimum inoculum size (MIS) of 10(3) s cfu/ml. However, when the surface was contaminated by inoculating it with dry-cell suspensions, the viable cells carried over were detected at an MIS of 10(7) s cfu/ml. The viable cells in the internal lumen of the needle much more than those on its outside surface spread to the HS of MDVs. For exposures of 24 h and 72 h at 4 degrees C to HS with 1% benzyl alcohol as a preservative in MDVs, viable cells of all isolates tested were detected at MIS values of 1 s and 10 s cfu/ml, respectively, increases three orders of magnitude smaller than those of reference strain IFO3736. These results suggest that S. marcescens isolates are readily carried over into the HS of MDVs by piercing a wet, contaminated rubber septum with a syringe needle. Also, despite the sterilization action of 1% benzyl alcohol, the organism persistently survived at 4 degrees C, even when initial contamination was with a small amount of inoculum.