ABSTRACT
The spatial distribution and abundance of suspected microplastics (SMPs) in the surface water of a metropolitan city, as represented by four Hong Kong rivers, was studied during the dry season. Shing Mun River (SM), Lam Tsuen River (LT), and Tuen Mun River (TM) are located in urbanized areas, and SM and TM are tidal rivers. The fourth river, Silver River (SR) is situated in a rural area. TM had a significantly higher SMP abundance (53.80 ± 20.67 n/L) than the other rivers. The SMP abundance increased from upstream to downstream in non-tidal rivers (LT and SR), but not in tidal rivers (TM and SM), probably due to the tidal influence and a more homogeneous urban development along the tidal rivers. Inter-site differences in the SMP abundance were strongly correlated with the built area ratio (defined as the percentage of surrounding developed land area), human activities, and the nature of the river. About half (48.72 %) of the SMPs were <250 µm. Fibers and fragments were most abundant (>98 %), with most of them being transparent (58.54 %), black (14.68 %), or blue (12.12 %). Polyethylene terephthalate (26.96 %) and polyethylene (20.70 %) were the most common polymers. However, the MP abundance could be overestimated due to the presence of natural fibers. By contrast, an underestimation of the MP abundance could result from a smaller volume of water samples collected, due to a low filtration efficiency caused by high organic content and particle concentrations in the water. A more effective solid waste management strategy and upgrading of the sewage treatment facilities for removing microplastics are recommended to ameliorate the microplastic pollution in local rivers.
ABSTRACT
This study investigated the transmission dynamics of meticillin-resistant Staphylococcus aureus (MRSA) in a tertiary referral surgical unit with 300 beds. All adult patients were actively screened for MRSA by culture at hospital admission and twice weekly thereafter during hospitalisation from 1 October to 31 December 2008. The colonisation pressure per 1000 patient-days and the incidence density of nosocomial MRSA transmission per 1000 colonisation-days were calculated for the different spa types of MRSA. In total, 6619 nasal swabs were obtained from 2289 patients. One-hundred and forty-eight (7%) patients had MRSA in nasal swabs at admission screening, of which 68/148 (46%) were residents of elderly care homes. Fifty-two of 2141 (2%) patients had conversion of nasal MRSA carriage status from negative to positive during hospitalisation. Among the 200 patients with MRSA, spa types t1081 and t037 were found in 99 (50%) and 30 (15%) patients, respectively. The colonisation pressure per 1000 patient-days was 40.9 for t0181, 22.2 for t037 and 26.3 for the less common spa types. The incidence densities of nosocomial MRSA transmission per 1000 colonisation-days were significantly higher for t1081 (28.5 vs 4.0, P<0.01) and t037 (21.5 vs 4.0, P=0.03) compared with the less common spa types. Proactive screening of MRSA in patients from elderly care homes and targeted isolation of these patients, especially those carrying spa types with high transmissibility, are important for the control of MRSA in hospitals.
