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dc.contributorFaculty of Health and Social Sciencesen_US
dc.contributor.advisorLeung, H. M. Polly (HTI)en_US
dc.creatorLeung, Chi Man-
dc.publisherHong Kong Polytechnic Universityen_US
dc.rightsAll rights reserveden_US
dc.titleEpidemiology of acinetobacter species in Hong Kongen_US
dcterms.abstractIt is now recognised that Acinetobacter species play a significant role in colonisation and infection of patients. The importance of these organisms is mainly related to their major features such as clonal diversity, resistance to desiccation and capability of acquiring resistance to antibiotics. Organisms in the genus Acinetobacter have long been known as saprophytes in the environment, but now they are known to be an important nosocomial pathogen. Within the genus, A. baumannii has been well documented to be associated with severe infections that cause hospital outbreaks worldwide. The cross-transmission of this organism from patient to patient and the possibility of outbreak extension by patient transfer has been demonstrated. Further to the increase in the occurrence of Acinetobacter infections, a substantial increase in the incidence of multidrug-resistant A. baumannii infections in Hong Kong has been reported. Hong Kong is currently endemic for Acinetobacter infections that pose a major therapeutic challenge. The current understanding is that acinetobacters can be encountered on human skin. The existence of an extra-hospital reservoir of Acinetobacter species, especially A. baumannii, and the implication of this potential reservoir in the role of infection are still controversial. This study aimed to investigate the epidemiology of Acinetobacter species in clinical samples, human skin flora and the community environment. The Acinetobacter isolates were characterised for species identities, antimicrobial susceptibility, multilocus sequence typing (MLST) and resistance genes. The additional information gathered could contribute to a better understanding of the dynamics of spread of multidrug-resistant A. baumannii in Hong Kong. A major finding of this study was the emergence of carbapenem-resistant A. baumannii ST195 harbouring OXA-23 carbapenemase in one of the major hospitals in Hong Kong. In particular, the isolates also carried insertion sequences ISAba1 located upstream to the OXA-23, thus contributing to the carbapenem resistance. In addition, the prevalence of Acinetobacter baumannii in a skin carriage study was found to be 7.6%, and that in the community environment was 26%. Upon further characterisation of the isolates, it was found that two isolates from the community environment and one isolate from skin were carbapenem resistant. This result may indicate the potential spread of drug-resistant pathogens within and outside hospitals. Although we did not isolate a predominant clone of A. baumannii in human skin carriage and the community environment we investigated in this study, we did discover that one genotype of carbapenem-resistant A. baumannii from nonclinical sources was closely related to the predominant genotype ST195 in clinical samples with double-locus variants (DLVs). This observation may provide some evidence that some epidemiological mixing and spread of the bacteria from the hospital to the community is happening. Because this was a small-scale epidemiological study, this finding should be verified by further study involving molecular epidemiological tracing from different sources of samples.en_US
dcterms.extentxvii, 130 pages : color illustrationsen_US
dcterms.isPartOfPolyU Electronic Thesesen_US
dcterms.educationalLevelAll Doctorateen_US
dcterms.LCSHAcinetobacter infections -- China -- Hong Kongen_US
dcterms.LCSHNosocomial infections -- China -- Hong Kongen_US
dcterms.LCSHHong Kong Polytechnic University -- Dissertationsen_US
dcterms.accessRightsrestricted accessen_US

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