An unprecedented outbreak investigation for nosocomial and community-acquired legionellosis in Hong Kong.

BACKGROUND: The environmental sources associated with community-acquired or nosocomial legionellosis were not always detectable in the mainland of China and Hong Kong, China. The objective of this study was to illustrate the control measures implemented for nosocomial and community outbreaks of legionellosis, and to understand the environmental distribution of legionella in the water system in Hong Kong, China. METHODS: We investigated the environmental sources of two cases of legionellosis acquired in the hospital and the community by extensive outbreak investigation and sampling of the potable water system using culture and genetic testing at the respective premises. RESULTS: The diagnosis of nosocomial legionellosis was suspected in a patient presenting with nosocomial pneumonia not responsive to multiple beta-lactam antibiotics with subsequent confirmation by Legionella pneumophila serogroup 1 antigenuria. High counts of Legionella pneumophila were detected in the potable water supply of the 70-year-old hospital building. Another patient on continuous ambulatory peritoneal dialysis presenting with acute community-acquired pneumonia and severe diarrhoea was positive for Legionella pneumophila serogroup 1 by polymerase chain reaction (PCR) testing on both sputum and nasopharyngeal aspirate despite negative antigenuria. Paradoxically the source of the second case was traced to the water system of a newly commissioned office building complex. No further cases were detected after shock hyperchlorination with or without superheating of the water systems. Subsequent legionella counts were drastically reduced. Point-of-care infection control by off-boiled or sterile water for mouth care and installation of water filter for showers in the hospital wards for immunocompromised patients was instituted. Territory wide investigation of the community potable water supply showed that 22.1% of the household water supply was positive at a mean legionella count of 108.56 CFU/ml (range 0.10 to 639.30 CFU/ml). CONCLUSIONS: Potable water systems are open systems which are inevitably colonized by bacterial biofilms containing Legionella species. High bacterial counts related to human cases may occur with stagnation of flow in both old or newly commissioned buildings. Vigilance against legionellosis is important in healthcare settings with dense population of highly susceptible hosts.

Risk factors for community-associated methicillin-resistant Staphylococcus aureus infection in Hong Kong.

OBJECTIVES: The risk factors for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection were not well understood. The objective of this study was to identify risk factors associated with CA-MRSA infection in Hong Kong. METHODS: We carried out a matched case control study. Cases and controls were recruited from 14 acute public hospitals in Hong Kong. One control was individually matched to one case based on sex, age, admission date and ward location. We interviewed each case and control by telephone using a standard questionnaire. We used a conditional logistic regression model for multivariate analysis. RESULTS: We successfully recruited 127 pairs of matched case and control. We found that sharing of personal items with other persons had a higher risk of CA-MRSA infection (Adjusted matched odds ratio [aOR]: 4.71, 95% confidence interval [CI] 1.43-15.59). On the other hand, patients who had frequent hand washing practice (aOR: 0.21, 95%CI 0.06-0.72) and those who reported history of acne (aOR: 0.12, 95%CI 0.02-0.74) had a lower risk of CA-MRSA infection. CONCLUSIONS: We concluded that sharing of personal items with other persons is a risk factor for CA-MRSA infection while frequent hand washing is a protective factor against the infection.

Prevalence of subclinical infection by the SARS coronavirus among general practitioners in Hong Kong.

Eight general practitioners had severe acute respiratory distress syndrome (SARS) in Hong Kong during the epidemic, and others may have been infected by the SARS coronavirus without developing the full syndrome. We conducted a serological and questionnaire survey to determine the prevalence of subclinical infection by SARS coronavirus among general practitioners in Hong Kong. Participants had to be doctors actively practising in family medicine and who did not have SARS. Approximately 3200 general practitioners were invited to participate and the results of 574 were eligible for analysis. 29 samples were tested positive by enzyme-linked immunosorbent assay, but all these samples had titre < 25 by immunoflorescence assay. The prevalence for seropositivity was thus 0% (95% CI, 0.0%-0.6%). This finding documents the lack of subclinical infection by SARS coronavirus in an at-risk group in the community.