Extended-spectrum β-lactamase and carbapenemase-producing Aeromonas species in wild animals from Portugal.

AeromonAs are Gram-negative, facultative-anaerobic, non-sporeforming, glucose-fermenting, oxidaseand catalase-positive rods (Martin-Carnahan and Joseph 2005). Apart from fish, which are widely reported hosts for Aeromonads, insects, crustaceans, reptiles, birds and mammals were also found to harbour Aeromonas species, both in healthy and disease state (Pearson and others 2000, Turutoglu and others 2005, Evangelista-Barreto and others 2006, Ceylan and others 2009). An increase in resistance levels of the genus, particularly to β-lactam antimicrobial agents, has been observed not only in clinical isolates, but also in environmental strains (Saavedra and others 2004, 2007). The most common mechanism of antibacterial resistance is the production of three chromosomally encoded β-lactamases, which have been described and identified in different Aeromonas (Janda and Abbott 2010). They may or may not concomitantly occur in the same strain, and their coordinated expression is induced by the presence of β-lactam antibiotics (Walsh and others 1997, Avison and others 2004). These enzymes comprise cephalosporinases (Ambler’s class C), penicillinases/oxacillinases (class D) such as OXA-type enzymes and metallo-β-lactamases (class B) (Hayes and others 1994). The most common metallo-β-lactamases produced by this genus are of the ‘CphA’-type, whose sequences appear to be widely distributed in Aeromonas hydrophila an Aeromonas veronii strains (Walsh and others 1997). Recently, two other metallo-β-lactamases, VIM and IMP, have