7 MATERIAL E MÉTODOS
Foto 2 Amostras 27 e 156 Teste de adição de ácido clavulânico
CTX-Cefotaxima; CTX/CLAV – Cefotaxima /Ácido Clavulânico; FEP – Cefpime; FEP/CLAV – Cefpime/ácido clavulâmico; CAZ – Ceftazidima; CAZ/CLAV- Ceftazidima/Ácido Clavulâmico
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5. O imipenemo foi o único antibiótico que apresentou actividade contra as 17
estirpes produtoras de ESBL, (100%), mas dado não se tratar de um antibiótico do ambulatório, a sua administração obriga a internamento hospitalar.
6. Para além do imipenemo, houve antibióticos não β-lactâmicos que apresentaram actividade contra algumas destas 17 estirpes produtoras de ESBL: netilmicina, 14 casos (82.3%); nitrofurantoína, 12 casos (70.6%); cloranfenicol, 11casos (64.7%); norfloxacina, 5 casos (29.4%); trimetoprim, 4 casos (23.5%); tetraciclina, 3 casos (17.6%) e estreptomicina, 2 casos (11.8%).
Gráfico 2 – Eficácia dos antibióticos não β-lactâmicos testados nas estirpes produtoras de ESBL.
NA - ácido nalidíxico (30 µg); NOR – norfloxacina (30 µg); F – nitrofurantoina (30 µg); TE – tetraciclina (30 µg); C – cloranfenicol (30 µg); SXT – trimetoprim-sulfametoxazol (1,25 µg/ 23,75 µg); NET – netilmicina (30 µg); S – estreptomicina (30 µg);
7. As 17 estirpes produtoras de ESBL, apresentaram perfis de co-resistência a um
ou mais antibióticos não β -lactâmicos. Muito possivelmente, durante os
fenómenos de conjugação bacteriana poderá também haver transferência de genes codificadores de ESBL bem como de genes codificadores de outras resistências.
8. O cruzamento de informações obtidas pelos métodos manuais aqui realizados e as fornecidas pelo sistema automático Vitek®(bioMérieux) revela grande sobreposição no que diz respeito à detecção de estirpes produtoras de ESBLs. No entanto, a amostra 349, reportada pelo Vitek® como uma estirpe de E.coli não produtora de ESBLs foi considerada positiva pelo teste de despiste e
confirmada pelo teste de adição de ácido clavulânico (ΔCLAV>5mm para os
DISSERTAÇÃO PARA MESTRADO DE ANÁLISES CLÍNICAS 52
automatizados reportarem resultados falsamente negativos (Donaldson et
al.,2008),(Farber et al.,2008), (Wiegand et al.,2007).
9. A estirpe 287 (C.freundii) apresentou comportamentos fenotípicos sobreponíveis nos dois testes de sensibilidade realizados em meio de Mueller-Hinton com e
sem adição de cloxacilina (500µg/ml). É conhecido o facto das β -lactamases do
tipo AmpC, quando presentes conjuntamente com as β-lactamases do tipo ESBL poderem mascarar o fenótipo destas últimas, sendo todavia inibidas pela cloxacilina.
10. Pelo processo de conjugação obtiveram-se 2 casos de transconjugantes com resistência ao SXT (T96 e T273). Durante o processo de conjugação houve transferência de genes codificadores da resistência ao SXT.
11. A amostra 156 é uma estirpe multirresistente. Apresenta unicamente susceptibilidade ao Imipenem ( IPM), à Nitrofurantoina (F) e ao Cloranfenicol (C) .A focagem isoeléctrica revela a presença de 3 bandas com pI´s: 5.4, 7.4, e >8.0. Este fenótipo é muito sugestivo do fenótipo apresentado por um clone existente em Portugal e restante Europa. Trata-se de um clone de E. coli produtor das β-lactamases TEM-1 (pI:5,4), OXA-1(pI:7,4) e CTX-M- 15(pI:8,6), e possuidor do gene aac6’Ibcr
12. Neste estudo, a prevalência de Enterobacteriaceae produtoras de ESBL foi de 4%. Este valor é superior aos encontrados em estudos efectuados em países do Norte da Europa mas definitivamente inferior aos referidos para a América Latina (Villegas et al., 2008).
que condiciona redução de susceptibilidade às fluorquinolonas (Machado et al., 2006).
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10- CONCLUSÃO
A presença de Enterobacteriaceae produtoras de β-lactamases de espectro alargado em amostras clínicas da comunidade, é uma realidade da zona urbana do grande Porto que deve ser tida em conta pelos laboratórios de análises clínicas públicos e privados desta zona do país.
É urgente a racionalização do uso de antibióticos β-lactâmicos.
É fundamental investir-se em estudos de detecção e vigilância de Enterobacteriaceae produtoras de ESBL.
É essencial que os laboratórios de análises clínicas incluam métodos de detecção de
Enterobacteriaceae produtoras de ESBL, na sua rotina.
Este contributo ajudará em muito os clínicos na escolha do tratamento a instaurar, reduzindo-se assim a ocorrência de falhas terapêuticas por falta de informação
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