Evaluation of Staphylococcus pseudintermedius isolated from clinical samples of dogs from a clinic in Hong Kong

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Evaluation of Staphylococcus pseudintermedius isolated from clinical samples of dogs from a clinic in Hong Kong


Author: Wong, Kang-lung Kevin
Title: Evaluation of Staphylococcus pseudintermedius isolated from clinical samples of dogs from a clinic in Hong Kong
Degree: M.Sc.
Year: 2011
Subject: Staphylococcus.
Veterinary medicine.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: xi, 74 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2451602
URI: http://theses.lib.polyu.edu.hk/handle/200/6221
Abstract: Staphylococci are part of the normal flora of humans and dogs. Staphylococcus pseudintermedius (SP) are opportunistic pathogens and most methicillin resistant strains are multi-drug resistant. MRSP is not directly related to human health, but there is a potential threat of infection, especially in veterinary staff and dog owners. In this study the prevalence of SP in clinical specimens of dogs was investigated in samples from a veterinary clinic in Hong Kong between 2008 to 2010. Twenty-six dogs suffering from pyoderma were included in the study. They were administrated cephalosporin and specimens were collected from the three body sites (skin wound, nose and anus) at first presentation and one month later after cephalosporin administration. Sixty three SP isolates, including 38 methicillin susceptible S. pseudintermedius (MSSP) and 25 Methicillin resistant S. pseudintermedius (MRSP) were obtained and twelve dogs had MRSP infection. This study also aimed to determine if the S. pseudintermedius at carriage sites (nose and anus) matched with the infection sites (skin). SP and MRSP isolates were more likely found in skin wound and anus together (OR = 9.39 95%, CI 1.7-52.1; OR = 2.40, 95% CI 0.2-34.9 respectively) rather than skin wound and nose. It also investigated the effectiveness of a panel of antibiotic for treatment of Staphylococcus aureus (SA) and Methicillin resistant Staphylococcus aureus (MRSA) against all SP isolates. An MRSP isolates were susceptible to drugs used for treatment of severe MRSA infections included vancomycin, fusidic acid, and linezolid, quinupristin/dalfopristin, and tigecycline. The cephalosporin treatment was supposed to have successfully eradicated the MSSP infection in many cases as the dogs were not brought back at one month follow up.
The Clinical and Laboratory Standards Institute (CLSI) had published a new interpretive guideline 2008 for the identification of methicillin resistant staphylococcal isolates. Screening for MRSP was performed by oxacillin and cefoxitin disk diffusion method using 2005 CNS CLSI guideline followed by mecA PCR confirmation. For detection of MRSP, use of CNS CLSI 2005 guideline for oxacillin disk diffusion had much better sensitivity (100%) than that of 2009 guideline (80-92%) for detection of MRSP. The findings also suggested that cefoxitin disk diffusion is not a suitable screening test for MRSP. All mecA confirmed MRSP were further investigated via SCCmec typing (i.e. SCCmec type I to V, type II-III and VII). This part of the study provides the information, which is the dominant SCCmec type of the MRSP isolates from the dog sample groups suffering pyoderma in Hong Kong. The distribution of SCCmec type of MRSP did not associated with any sampling sites and most MRSP isolates belonged to SCCmec types II-III, V and VII. The genetic polymorphism of SP isolates was also investigated in this study via PFGE. Sixty-three isolates from nose, anus and skin wound of 26 dogs at first presentation and 11 follow up dogs were lysed with proteinase K and digested with SmaI. The restriction products were analyzed by PFGE together with lambda ladder DNA markers. A dendrogram was drawn up and all isolates showed at least 33% similarity. Thirty-one different PFGE band patterns with 10 clusters were found in this study indicating high genetic diversity of SP in the dogs sample group. The SP isolates found in individual dogs had a tendency to be from the same PFGE cluster within different sampling sites and between first presentation and follow up specimen. In conclusion, SP is a dominant pathogen associated with dogs suffering from pyoderma. SP isolates from anus and skin wound were highly correlated and further study is required to investigate this finding. The induction of antimicrobial resistance in SP did not demonstrated in this study. A large samples study is required to analyze the induction of drug resistance in SP.

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