Transmission of methicillin-resistant staphylococcus aureus in the long term care facilities in Hong Kong

Background The relative contribution of long term care facilities (LTCFs) and hospitals in the transmission of methicillin-resistant Staphylococcus aureus (MRSA) is unknown. Methods Concurrent MRSA screening and spa type analysis was performed in LTCFs and their network hospitals to estimate the rate of MRSA acquisition among residents during their stay in LTCFs and hospitals, by colonization pressure and MRSA transmission calculations. Results In 40 LTCFs, 436 (21.6%) of 2020 residents were identified as ‘MRSA-positive’. The incidence of MRSA transmission per 1000-colonization-days among the residents during their stay in LTCFs and hospitals were 309 and 113 respectively, while the colonization pressure in LTCFs and hospitals were 210 and 185 per 1000-patient-days respectively. MRSA spa type t1081 was the most commonly isolated linage in both LTCF residents (76/121, 62.8%) and hospitalized patients (51/87, 58.6%), while type t4677 was significantly associated with LTCF residents (24/121, 19.8%) compared with hospitalized patients (3/87, 3.4%) (p < 0.001). This suggested continuous transmission of MRSA t4677 among LTCF residents. Also, an inverse linear relationship between MRSA prevalence in LTCFs and the average living area per LTCF resident was observed (Pearson correlation −0.443, p = 0.004), with the odds of patients acquiring MRSA reduced by a factor of 0.90 for each 10 square feet increase in living area. Conclusions Our data suggest that MRSA transmission was more serious in LTCFs than in hospitals. Infection control should be focused on LTCFs in order to reduce the burden of MRSA carriers in healthcare settings.published_or_final_versio

Studying the transmission dynamics of meticillin-resistant Staphylococcus aureus in Hong Kong using spa typing

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. © 2011 The Healthcare Infection Society.link_to_subscribed_fulltex

Epidemiology of Klebsiella oxytoca-associated diarrhea detected by simmons citrate agar supplemented with inositol, tryptophan, and bile salts

We studied the clinical and epidemiological characteristics of Klebsiella oxytoca-associated diarrhea in hospitalized patients in Hong Kong. Between 1 November 2009 and 30 April 2011, all inositol-fermenting colonies found on Simmons citrate agar supplemented with inositol, tryptophan, and bile salts (SCITB agar) used for the culturing of diarrheal stool samples were screened by a spot indole test for K. oxytoca. The overall sensitivity of SCITB agar plus the spot indole test (93.3%) for the detection of K. oxytoca in stool samples was superior to that of MacConkey agar (63.3%), while the specificities were 100% and 60.4%, respectively. The former achieved a 23-fold reduction in the workload and cost of subsequent standard biochemical identifications. Cytotoxin production and the clonality of K. oxytoca were determined by a cell culture cytotoxicity neutralization assay using HEp-2 cells and pulsed-field gel electrophoresis (PFGE), respectively. Of 5,581 stool samples from 3,537 patients, K. oxytoca was cultured from 117/5,581 (2.1%) stool samples from 104/3,537 (2.9%) patients. Seventy-six of 104 (73.1%) patients with K. oxytoca had no copathogens in their diarrheal stool samples. Twenty-four (31.6%) of 76 patients carried cytotoxin-producing strains, which were significantly associated with antibiotic therapy after hospital admission (50% versus 21.2%; P = 0.01). Health care-associated diarrhea was found in 44 (42%) of 104 patients with K. oxytoca, but there was no epidemiological linkage suggestive of a nosocomial outbreak, and PFGE showed a diverse pattern. None of the patients with cytotoxin-producing K. oxytoca developed antibiotic-associated hemorrhagic colitis, suggesting that K. oxytoca can cause a mild disease manifesting as uncomplicated antibiotic-associated diarrhea with winter seasonality. Copyright © 2012, American Society for Microbiology. All Rights Reserved.link_to_OA_fulltex

The clinical utility of two high-throughput 16S rRNA gene sequencing workflows for taxonomic assignment of unidentifiable bacterial pathogens in matrix-assisted laser desorption ionization-time of flight mass spectrometry

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