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Introduction: Acquired AmpC beta-lactamases (qAmpC) which confer resistance to cephamycins and reduced susceptibility to extended-spectrum cephalosporins and β-lactamase inhibitors have increasingly been recognized as an emerging problem worldwide. qAmpCs enzymes are grouped according to the DNA sequence similarity with natural chromosomal AmpCs of some Enterobacteriaceae species, namely C. freundii (CMY-2-like, LAT-1, CFE-1), Enterobacter spp. (ACT-1-like, MIR-1-like), M. morgannii (DHA-1-like) and H. alvei (ACC-1-like), and with Aeromonas spp. (CMY-1-like, FOX-1-like, MOX-1-like). Isolates harbouring qAmpCs are usually multirresistant, and inappropriate empirical therapy is associated with high mortality ratios in invasive infections. Objectives: Estimate the worldwide prevalence and distribution of qAmpC types. Methods: We conducted a literature review on pertinent articles published between 2000 and 2011 on qAmpC detection and prevalence in Enterobacteriaceae lacking inducible AmpC [E. coli (EC), K. pneumoniae (KP), K. oxytoca (KO), P. mirabilis (PM) and Salmonella spp. (SM)] isolated from human infections. Estimated relative frequencies were calculated for qAmpC types detected in each country with relevant articles. Results: A total of 26 relevant studies from 21 countries on qAmpC epidemiology were retrieved, comprising 216648 isolates (182573 EC, 18858 KP, 8117 SM, 2340 PM, and 2278 KO). qAmpCs were detected in all but one study from Brazil, being the worldwide overall prevalence 0.55% (1194/216648, or 5.5 qAmpC producers per 1000 isolates). Countries with higher prevalence were China (4%), South Korea (3.5%), Portugal (3%) and Poland (3%), and the lowest were observed in Brazil (0%), Japan (0.08%), Switzerland (0.16%) and Belgium (0.16%). The overall species specific prevalence was 4.1%, 3.5%, 1.4%, 0.5% and 0.2% in SM, PM, KP, KO, and EC respectively. China presented the higher prevalence for KP (7%) and KO (3%), Thailand for EC (2%), while for PM and SM it was Poland (20.5%) and Mexico (7.7%), respectively. Globally, the main qAmpC variants detected were CMY-2 (53.1%), DHA-1 (30.6%) and CMY-2-like (11.7%). CMY-2 was predominantly present in EC, PM and SM isolates while DHA-1 was detected mostly among KP and KO. In countries like South Korea, China, and Portugal DHA-1 is the dominant variant, while in North America, Norway, Danmark, Tailand, Japan, Algeria and Spain is CMY-2. Conclusion: Although qAmpC prevalence is globally low, the results suggest that it is rising. This study also demonstrates that CMY-2 is the most prevalent qAmpC followed by DHA-1. Future studies are needed in order to monitor the spread of this emerging resistance mechanism.

É sabido que num mesmo país a prevalência de S. aureus meticilina-resistentes (SAMR) varia substancialmente de um hospital para outro. De modo a compreender a epidemiologia e a resistência aos antibióticos dos isolados SAMR no Hospital S. Teotónio – Viseu, conduzimos um estudo retrospectivo (2000-2001) através da análise da base de dados do laboratório (MODULAB IZASA), que permite obter dados demográficos acerca dos pacientes, e padrões de resistência dos isolados de S. aureus. A identificação das estirpes foi efectuada com o sistema Vitek (bioMérieux, Marcy L’étoile, France) e galerias BBL+ (Beckton Dickinson, Cockeysville, Maryland, USA). Para a susceptibilidade antimicrobiana recorreu-se ao sistema Vitek e ao método de difusão de disco (Kirby-Bauer). Foram seguidas as guidelines interpretativas da NCCLS. Do total de 300 isolados de S. aureus estudados, 110 (37%) provieram de exsudados purulentos, 109 (36.1%) do tracto respiratório, 52 (17.3%) de sangue e 16 (5.3%) de pontas de catéter. A resistência global à meticilina foi de 46.7% (140/300). As amostras mais comuns a partir das quais se isolaram SAMR foram as secreções respiratórias (54.2%), seguidas pelos exsudatos purulentos (24.2%), hemoculturas (12.1%) e pontas de catéter (7.1%). Nos isolados invasivos a resistência à meticilina foi de 32.7%. As taxas de resistência dos SAMR a outros antibióticos foram as seguintes: 96.3% resistentes à ciprofloxacina, 92.7% à eritromicina, 91.7% à gentamicina, 86.3% à tetraciclina, 75% ao trimethoprimsulfamethoxazole e 54.8% à clindamicina. A taxa de multirresistência foi de 87%. Os isolados SAMR exibem altos níveis de resistência à maioria dos antibióticos, excepto à teicoplanina e vancomicina, que continuam a ser as principais armas terapêuticas nas infecções por SAMR, apesar do uso substancial de glicopéptidos ao longo de muitos anos. Concluímos que a prevalência de isolados SAMR é elevada (46.7%) no Hospital S. Teotónio, o que se correlaciona com um estudo anterior de hospitais portugueses (48-50%), e com resultados de países mediterrâneos como Espanha, Itália e França (30-50%). Contudo, contrasta fortemente com os países do norte da Europa como Alemanha, Suécia, Holanda e Dinamarca (<5%). Estes dados serão úteis para a nossa comissão de controlo da infecção.