Resistance to b-lactams among Gram-negative bacteria is a worldwide issue. Increased prevalence of extended-spectrum b-lactamase (ESBL)-producers and the dissemination of carbapenem-resistance genes are particularly concerning. ESBL-producing strains are common in the Kingdom of Saudi Arabia, particularly among the Enterobacteriaceae, and carbapenem resistance is on the increase, especially among the non-fermenters. b-lactamase production is a major mechanism of resistance to these agents and although b-lactamase-producing strains have been documented in the Kingdom, relatively few reports characterized the molecular basis of this production. Nevertheless, available data suggest that CTX-M (CTX-M-15 in particular) is the predominant ESBL in the Enterobacteriaceae, with SHV also being prevalent in Klebsiella pneumoniae. Carbapenem resistance in the latter is mainly due to OXA-48 and NDM-1. In Pseudomonas aeruginosa, VEB-like enzymes are the most common ESBLs, and VIM is the prevalent metallo-b-lactamase. OXA-10 extended-spectrum enzymes are also frequent. PER and GES ESBLs have been reported in Acinetobacter baumannii, and oxacillinases (OXA-23 in particular) are the dominant carbapanamases in this species.
IntroductionInfections due to Gram-negative bacteria are a leading cause of morbidity and mortality worldwide (Giske et al., 2008). Antimicrobial agents are a major therapeutic tool in the treatment of such infections. However, antimicrobial resistance among Gram-negative bacteria, particularly among the Enterobacteriaceae and the non-fermenters, has become one of the most serious public health concerns worldwide (Giske et al., 2008;Livermore, 2012). The global dissemination of resistance has recently received much attention, especially following reports of the international spread of multi-resistant Enterobacteriaceae, particularly strains resistant to cephalosporins due to the production of CTX-M-type extended-spectrum b-lactamases (ESBLs) and strains producing carbapenemases such as KPC and NDM (Nordmann et al., 2011;Johnson & Woodford, 2013). The spread of resistance determinants is facilitated by a number of factors, including presence on genetic mobile elements, antibiotic misuse, poor infection control practices, and increased international travel. In this context Saudi Arabia is particularly relevant as it is annually a host for more than 4 million Muslim pilgrims from over 180 countries worldwide in the Hajj and Umra seasons. In addition, up to 6 million of the Kingdom's population are expatriates, mainly from south and east Asia, where antimicrobial resistance is rife, including to carbapenems (Yong et al., 2009). These factors could potentially make Saudi Arabia a hot spot for the collection of multidrug-resistant strains and the spread of antibiotic resistance around the world.We previously reported on the antimicrobial resistance among the key Gram-negative bacteria in Saudi Arabia and found increased prevalence of b-lactam-resistant strains, including ESBL-producers, and carbapenem resistance (Y...