Carreamento nasal/oral de Staphylococcus aureus em populações indígenas do norte e sudeste do brasil: resistência antimicrobiana, virulência, fatores de risco e epidemiologia molecular
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Data
2017-02-23
Autores
Abraão, Lígia Maria [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A origem racial representa um dos principais determinantes dos riscos de colonização e infecção por Staphylococcus aureus. Há algum tempo, comunidades indígenas têm se mostrado mais propensas em relação a tais riscos, apresentando linhagens de S. aureus com perfis distintos dos quais normalmente se encontram em populações não-nativas. Características peculiares entre diferentes populações, tais como viver em condições de superlotação, assistência em saúde prejudicada e condições precárias de higiene podem ser mais relevantes na patogênese de algumas formas de infecções por S. aureus. Deste modo, os indígenas inegavelmente se enquadram no grupo de risco para o carreamento de microrganismos resistentes, estando suscetíveis tanto à aquisição quanto à disseminação de infecções. O presente estudo objetivou a identificação da prevalência e de fatores de risco para carreamento nasal e oral de S. aureus sensíveis e resistentes à meticilina (Methicilinsensitive Staphylococcus aureus MSSA e Methicilin-resistant Staphylococcus aureus MRSA, respectivamente) em indígenas de comunidades do Norte e Sudeste do Brasil, avaliando a diversidade genética, disseminação, fatores de virulência e resistência antimicrobiana, associados às questões étnicas, demográficas, ambientais e comportamentais. Para tanto, foram coletadas amostras nasais e de orofaringe de 400 indígenas (116 da região sudeste e 284 da região norte) através de swabs estéreis e posteriormente elas foram semeadas em meio de cultura e identificadas pelos métodos tradicionais. Concomitantemente, foram levantados dados demográficos e clínicos dos sujeitos da pesquisa. Isolados de S. aureus foram submetidos a testes fenotípicos e genotípicos de suscetibilidade antimicrobiana e à caracterização do cassete cromossômico SCCmec. Para detecção dos genes de virulência, foi realizada a técnica da reação em cadeia de polimerase (PCR). A análise do perfil clonal se procedeu através da técnica Pulsed-Field Gel Electrophoresis – PFGE a fim de se identificar os clusters endêmicos na população. Com o intuito de se identificar grupos de genótipos relacionados, foi realizada a tipagem por Multilocus sequence typing – MLST. Os resultados evidenciaram taxa de prevalência geral de S. aureus de 47,6% (IC 95%: 42,64-52,64), enquanto que na região sudeste obteve-se um total de 43,1 % (IC 95% 33.94-52.62) e na região da Amazônia 49,4 % (IC 95% 43.50-55-45). Quando realizada a distribuição por sítios de colonização, as taxas foram 31,8% (IC 95%: 27,23 -36,82) de carreamento nasal e 25,7 (IC 95%: 21,53-30,55) oral. Em relação ao gene mecA de resistência à meticilina, 3 isolados foram positivos, sendo todos orais. Todas as amostras mecA positivas albergaram o SCCmec IV. Desse modo, a prevalência de MRSA no estudo foi de 0,7% (IC 95%: 0,19-2,37). Nenhuma amostra resistente foi identificada na região sudeste. Tratando-se da detecção dos genes de virulência, pôde-se evidenciar maior percentual dos genes relacionados às hemolisinas hla 96,3 e hld 80,6% e dos genes associados à produção do biofilme icaA 82,2 e icaD 72,7%. A identificação do perfil clonal através da análise por PFGE evidenciou presença de 21 clusters (>80% de similaridade) entre as populações nativas de ambos os estados, nos quais 5 clones principais agruparam amostras tanto das populações do sudeste quanto da região amazônica. Quando realizada análise pelo MSLT, identificou-se prevalência do complexo clonal ST 5, o qual reuniu amostras tanto de MSSA quanto MRSA, o quê sugere uma provável origem comum. Os resultados epidemiológicos mostraram associação do fator etnia com prevalência de S. aureus. Esse trabalho traz dados pioneiros acerca da epidemiologia de Staphylococcus aureus e MRSA em meio aos indígenas brasileiros. A análise do perfil clonal impulsiona a elucidação de questões relacionadas ao processo de evolução da bactéria estudada, sugerindo uma provável origem comum entre as diferentes estirpes encontradas. Por fim, os resultados epidemiológicos permitem inferir que o fator etnia está relacionado à prevalência de S. aureus em populações humanas.
The racial origin is one of the main risk determinants of Staphylococcus aureus colonization and infection. For some time now, indigenous communities have been shown to be more prone to these risks as they present S. aureus strains different from those usually found in non-native populations. Culturally typical characteristics among different populations, such as overcrowded living conditions, lack of health assistance, and poor hygiene conditions can be more relevant to the pathogenesis of some S. aureus infections. Therefore, the indigenous people are definitively a risk group for the carriage of resistant microorganisms, and are susceptible to both acquisition and dissemination of infections. This study aimed to identify the prevalence and the risk factors for nasal and oral carriage of methicillin-sensitive and methicillin-resistant S. aureus (MSSA and MRSA) in indigenous communities from the North and Southeast regions of Brazil by evaluating the genetic diversity, dissemination, virulence factors, and antimicrobial resistance associated to ethnic, demographic, environmental, and behavioral issues. To this end, nasal and oropharyngeal samples of 443 indigenous people (116 from the Southeast and 284 from the North) were collected with sterile swabs. Then, such samples were seeded in culture medium and identified by conventional methods. Meanwhile, clinical and demographic data from the subjects were collected. S. aureus isolates were phenotypically and genetically tested for oxacillin/methicillin susceptibility and the staphylococcal cassette chromosome mec (SCCmec) was characterized. The virulence genes identification was carried out by Polymerase Chain Reaction (PCR). The characterization of the clonal profile was performed by The Pulsed Field Gel Electrophoresis (PFGE) to identify the endemic clusters in the population. In order to identify clusters of related genotypes, Multilocus Sequence Typing (MLST) was performed. The results showed a general prevalence rate of S. aureus of 47.6% (CI 95%: 42.64-52.64), while in the Southeast region there was a total of 43.1% (CI 95%: 33.94-52.62) and in the Amazon region 49.4% (CI 95%: 43.50-55-45). When the colonization sites were distributed, the rates were 31.8% (CI 95%: 27.23-36.82) of nasal carriage and 25.7 (CI 95%: 21.53-30.55) of oral carriage. Regarding the mecA gene detection, 3 isolates were positive, being 3 oral isolates. All the positive mecA samples harbored the SCCmec IV. Thus, the prevalence of MRSA in the study was 0.7% (CI 95%: 0.19-2.37). No resistant sample was identified in the Southeast region. With the detection of virulence genes, a higher percentage of genes related to hemolysins hla 96.3 and hld 80.6% and genes associated with the production of biofilm icaA 82.2 and icaD 72.7% could be evidenced. The identification of the clonal profile through the characterization by PFGE evidenced 21 clusters (>80% similarity) among the native populations of both states in which 5 major clones clustered samples both from the Southeast and from the Amazon. When the MSLT analysis was carried out, a prevalence of clonal complex ST 5 was identified, which clustered samples both from MSSA and MRSA, suggesting a probable common origin. The epidemiological results showed an association between the ethnicity factor and the prevalence of S. aureus. This study brings pioneering data about the epidemiology of Staphylococcus aureus and MRSA among Brazilian indigenous populations. The analysis of the clonal profile promotes the elucidation of questions related to the evolution process of the bacterium studied, suggesting a probable common origin among the different strains found. Finally, the epidemiological results allow us to infer that the factor ethnicity factor is related to the prevalence of S. aureus in human populations.
The racial origin is one of the main risk determinants of Staphylococcus aureus colonization and infection. For some time now, indigenous communities have been shown to be more prone to these risks as they present S. aureus strains different from those usually found in non-native populations. Culturally typical characteristics among different populations, such as overcrowded living conditions, lack of health assistance, and poor hygiene conditions can be more relevant to the pathogenesis of some S. aureus infections. Therefore, the indigenous people are definitively a risk group for the carriage of resistant microorganisms, and are susceptible to both acquisition and dissemination of infections. This study aimed to identify the prevalence and the risk factors for nasal and oral carriage of methicillin-sensitive and methicillin-resistant S. aureus (MSSA and MRSA) in indigenous communities from the North and Southeast regions of Brazil by evaluating the genetic diversity, dissemination, virulence factors, and antimicrobial resistance associated to ethnic, demographic, environmental, and behavioral issues. To this end, nasal and oropharyngeal samples of 443 indigenous people (116 from the Southeast and 284 from the North) were collected with sterile swabs. Then, such samples were seeded in culture medium and identified by conventional methods. Meanwhile, clinical and demographic data from the subjects were collected. S. aureus isolates were phenotypically and genetically tested for oxacillin/methicillin susceptibility and the staphylococcal cassette chromosome mec (SCCmec) was characterized. The virulence genes identification was carried out by Polymerase Chain Reaction (PCR). The characterization of the clonal profile was performed by The Pulsed Field Gel Electrophoresis (PFGE) to identify the endemic clusters in the population. In order to identify clusters of related genotypes, Multilocus Sequence Typing (MLST) was performed. The results showed a general prevalence rate of S. aureus of 47.6% (CI 95%: 42.64-52.64), while in the Southeast region there was a total of 43.1% (CI 95%: 33.94-52.62) and in the Amazon region 49.4% (CI 95%: 43.50-55-45). When the colonization sites were distributed, the rates were 31.8% (CI 95%: 27.23-36.82) of nasal carriage and 25.7 (CI 95%: 21.53-30.55) of oral carriage. Regarding the mecA gene detection, 3 isolates were positive, being 3 oral isolates. All the positive mecA samples harbored the SCCmec IV. Thus, the prevalence of MRSA in the study was 0.7% (CI 95%: 0.19-2.37). No resistant sample was identified in the Southeast region. With the detection of virulence genes, a higher percentage of genes related to hemolysins hla 96.3 and hld 80.6% and genes associated with the production of biofilm icaA 82.2 and icaD 72.7% could be evidenced. The identification of the clonal profile through the characterization by PFGE evidenced 21 clusters (>80% similarity) among the native populations of both states in which 5 major clones clustered samples both from the Southeast and from the Amazon. When the MSLT analysis was carried out, a prevalence of clonal complex ST 5 was identified, which clustered samples both from MSSA and MRSA, suggesting a probable common origin. The epidemiological results showed an association between the ethnicity factor and the prevalence of S. aureus. This study brings pioneering data about the epidemiology of Staphylococcus aureus and MRSA among Brazilian indigenous populations. The analysis of the clonal profile promotes the elucidation of questions related to the evolution process of the bacterium studied, suggesting a probable common origin among the different strains found. Finally, the epidemiological results allow us to infer that the factor ethnicity factor is related to the prevalence of S. aureus in human populations.
Descrição
Palavras-chave
Colonização nasal/oral, Epidemiologia molecular, MRSA, Populações indígenas, Nasal and oral colonization, Molecular epidemiology, Indigenous populations