Published selective media were evaluated for the isolation of Aeromonas spp. from environmental samples by membrane filtration. Satisfactory recoveries were obtained only with mA agar (Rippey & Cabelli) and dextrin-fuchsin-sulphite agar (Schubert), but neither was sufficiently selective. The positive aspects of these two media were combined in a new medium, ampicillin-dextrin agar. Recovery from pure cultures and environmental samples was optimal at an ampicillin concentration of 10 mg/l and incubation for 24 h at 30 degrees C under aerobic conditions, and specificity was high (i.e. confirmation rate usually greater than 90%, no false negative colonies encountered). The medium can also be used for isolation of Aeromonas spp. from sea water provided that the vibriostatic agent 0/129 is added at 50 mg/l.

To determine the role of respiratory syncytial virus (RSV)-specific cell-mediated immunity during natural reinfection, we investigated whether RSV-specific T-cell responses protect against reinfection and, subsequently, whether reinfection boosts virusspecific memory. In a cohort of 55 infants who were hospitalized for RSV bronchiolitis, RSV-specific lymphoproliferative responses in the peripheral blood were measured at three time-points: on admission, 4 wk after admission, and 1 y later, after the second winter season. Memory was defined as a stimulation index (SI) Ͼ2. During the second winter season, nasal secretions were collected in every case of a runny nose. Reinfection was diagnosed if immunofluorescence or PCR was positive for RSV. Virus-specific memory was found in one child on admission for primary RSV infection, whereas 4 wk later 44 infants (80%) had memory. Reinfection with RSV was found in 23 infants (43%) during the second winter season. After the second season, memory was found in 20 infants (38%). No differences in SI after the second winter season were found between infants with and without reinfection (2.3 versus 2.1). However, a highly significant correlation was found between SI measured 4 wk after primary RSV infection and SI after the second winter season (r ϭ 0.40, p ϭ 0.001). In conclusion, RSV-specific T-cell responses did not provide protection against reinfection. Moreover, reinfection did not boost RSV-specific T-cell proliferation. To explain both findings, it is hypothesized that RSV-specific T cells fail to expand in vivo upon reinfection. RSV is one of the most important respiratory pathogens in infancy causing the majority of lower respiratory tract infections during the winter season. Hospitalization rates for RSV illness are 1-30 cases per 1000 infants Ͻ1 y of age (1-3). In hospitalized infants with RSV bronchiolitis, mechanical ventilation is required in 7-21% of cases (4 -6). Mortality in RSV-infected infants with lower respiratory tract symptoms is Ͻ1% (7).Reinfection with RSV occurs frequently and usually has a mild character with symptoms of uncomplicated upper respiratory tract infection (8). Neutralizing antibodies induced by primary RSV infection appear to provide only partial protection for a limited period of time, which does probably not last until the subsequent RSV season (8,9). Evidence that intact cell-mediated responses play a role in clearance of the virus and protection against reinfection was derived from animal studies (10). In humans, little information is available on the role of virus-specific CMI induced during primary infection in the protection against reinfection with RSV.Currently, no vaccine for RSV is available. In the 1960s, a formalin-inactivated vaccine was used in infants (11). No protection against naturally acquired RSV was observed. In contrast, enhanced disease and increased mortality were observed during RSV infection after vaccination. CMI has been implicated in the pathogenesis of this phenomenon (12

To evaluate the applicability of disability adjusted life-years (DALYs) as a measure to compare positive and negative health effects of drinking water disinfection, we conducted a case study involving a hypothetical drinking water supply from surface water. This drinking water supply is typical in The Netherlands. We compared the reduction of the risk of infection with Cryptosporidium parvum by ozonation of water to the concomitant increase in risk of renal cell cancer arising from the production of bromate. We applied clinical, epidemiologic, and toxicologic data on morbidity and mortality to calculate the net health benefit in DALYs. We estimated the median risk of infection with C parvum as 10-3/person-year. Ozonation reduces the median risk in the baseline approximately 7-fold, but bromate is produced in a concentration above current guideline levels. However, the health benefits of preventing gastroenteritis in the general population and premature death in patients with acquired immunodeficiency syndrome outweigh health losses by premature death from renal cell cancer by a factor of > 10. The net benefit is approximately 1 DALY/million person-years. The application of DALYs in principle allows us to more explicitly compare the public health risks and benefits of different management options. In practice, the application of DALYs may be hampered by the substantial degree of uncertainty, as is typical for risk assessment. Key work: bromate, Cryptosporidium parvum, disinfection, drinkmg water, ozone, quality of life, risk assessment. Environ Health Perspect 108: 315-321 (2000).[Online 21 February 2000] htp:/lle/hpnetl.nie,hs.nih.gov/docs/2OOO/108p315-321havelaar/abstract.htmIThe microbiologic safety of drinking water is of paramount importance to public health (1). Source protection is generally accepted as the primary strategy to obtain microbiologically safe drinking water. However, many sources (surface waters in particular) are highly polluted and need extensive treatment before distribution to the consumer. Chemical disinfection is prominent in these treatment schemes. Highly oxidizing chemicals such as chlorine and ozone kill a variety of pathogenic microorganisms during treatment, and chlorine is applied in many countries as an additional safeguard in the distribution system. An important drawback of the use of these chemicals is the generation of disinfection by-products, which have suspected adverse effects on human health. This situation calls for a formal quantitative framework to compare the positive and negative health effects of drinking water disinfection and to assist in the design and operation of treatment plants (2).Microbiologic risks are expressed as the annual individual probability of infection for a given consumption of drinking water. Chemical risks related to genotoxic carcinogens are usually associated with an increase in cancer incidence attributable to a lifetime exposure. The public health impact of these disease end points is very different and cannot be compared directly. Hen...

Over the next few decades, many Western European countries will undergo a large demographic transformation introduced by the retirement of the "baby boomers" and the possibility of striking increases in longevity. The aim of this study was to estimate the effect of a growing and ageing Dutch population on the future consumption of pharmaceuticals, so as to be able to anticipate the potential future emissions of these pharmaceuticals and their residues to surface waters. A total of 354 prescribed pharmaceuticals from 40 therapeutic groups was selected for study. These constitute 1.251 metric tonnes (98%) of the total Dutch consumption of prescribed pharmaceuticals in 2007. Calculations based on a fixed consumption rate (2007) predict that demographic developments can be expected to push consumption up to 1.504 metric tonnes in 2020 (+17%) and 1.851 metric tonnes by 2050 (+37%). Therapeutic groups showing the largest increase are related to illnesses associated with old age. The only groups showing a decrease are the antivirals and drugs for addiction treatments as well as ethinylestradiol, an active compound in contraceptives.