Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/36760
Title: Longitudinal carriage of staphylococcus aureus in families of non-healthcare workers in Hong Kong
Authors: Lo, D
Boost, MV
Cheng, E
O'Donoghue, MM 
Issue Date: 2008
Source: 18th European Congress of Clinical Microbiology & Infectious Diseases, Barcelona, Spain, 19-22 April, 2008 How to cite?
Abstract: Objectives: Overall 25% of humans carry S. aureus, but this colonisation may be transient or persistent, and a high proportion is never colonised. Transmission of S. aureus has been documented in families of healthcare workers (HCW). This study investigated longitudinal carriage and transmission of S. aureus in families without HCWs.
Methods: Nasal samples from 100 non HCW associated families, each with at least three persons living together, were obtained at monthly intervals for 3 months. Swabs were cultured on blood agar, mannitol salt agar (MSA), MSA with 6gg/ ml oxacillin, and enriched in brain heart infusion broth with 5% salt. Colonies showing staphylococcal morphology were confirmed as S. aureus using Staphaurex. Susceptibility to oxacillin and cefoxitin and other antibiotics was determined by disc diffusion. Strains appearing meticillin resistant were examined for the presence of mecA by PCR, and characterised for PVL gene carriage, SCCmec and agr type.
Results: Of 342 subjects, 27.4%, 24.9% and 19.3% were colonised on the first, second, and third sampling respectively. Overall, 11.4% were colonised persistently, 26.9% transiently, and 61.7% never colonised. Persistent carriage was more common in those aged <10 and >60. Only non-carriers were observed in 29 families and two families consisted only of persistent carriers. Mothers were the most frequently colonised family member. Of 57 families with at least one colonised member on the first occasion, 16 had at least one other family member with the same strain (12 of 57 families on the second, and 10 of 48 on the third). Between first and second, and second and third samplings, in 7 and 6 of the colonised families respectively, another family member had become colonised with the same strain on the subsequent sampling. MRSA was isolated from 4 subjects in the first collection, including a mother and son with the same strain resistant to b-lactams only (SCCmec type IV variant). The second collection yielded only one MRSA with SCCmec type IV, but on the third, 3 subjects were MRSA-colonised, including a different mother and son pair with a type IV variant displaying erythromycin resistance. All MRSA strains were agr type I and none harboured PVL genes.
Conclusions: Transmission occurred in 10 ± 12% of families over a one month period. Although MRSA colonisation remained low in families without HCWs (range 0.3–1.1%), transmission of MRSA between a mother and son occurred on two occasions.
URI: http://hdl.handle.net/10397/36760
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