A b s t r a c tPseudomonas aeruginosa is a leading human pathogen that causes serious infections at various tissues and organs leading to life threatening health problems and possible deadly outcomes. Resistance patterns vary widely whether it is from hospitals or community acquired infections. Reporting resistance profiles to a certain antibiotics provide valuable information in a given setting, but may be extrapolated outside the sampling location. In the present study, P. aeruginosa isolates were screened to determine their susceptibilities against antipseudomonal antimicrobial agents and possible existing mechanisms of resistance were determined. Eighty-six isolates of P. aeruginosa were recovered. Isolates representing different resistance profiles were screened for the existence of three different resistance mechanisms including drug inactivation due to metallo-β-lactamases, drug impermeability by outer membrane proteins and drug efflux. All tested isolates showed uniform susceptibility (100%, n = 86/86) to piperacillin, meropenem, amikacin, and polymyxin B. A single isolate was found to be imipenem resistant (99%, n = 85/86). The possible mechanisms of resistance of P. aeruginosa to imipenem involve active drug efflux pumps, outer membrane impermeability as well as drug inactivating enzymes. These findings demonstrate the fundamental importance of the in vitro susceptibility testing of antibiotics prior to antipseudomonal therapy and highlight the need for a continuous antimicrobial resistance surveillance programs to monitor the changing resistance patterns so that clinicians and health care officials are updated as to the most effective therapeutic agents to combat the serious outcomes of P. aeruginosa infections. This copy is for personal use only -distribution prohibited.El Zowalaty M.E. and Gyetvai B.1 24 anti biotics (El Zowalaty et al., 2015). The literature is rich in surveillance studies from all over the world reporting varying resistance rates among P. aeruginosa against different antimicrobial agent. Recently, studies have focused on the decreased susceptibility of P. aeru ginosa to currently used antipseudomonal agents, including β-lactams, aminoglycosides, and fluoroquinolones (Al-Tawfiq, 2007) since resistance of P. aeru ginosa to carbapenems, piperacillin, and other highly active antibiotics has emerged and is increasing which makes treatment of P. aeruginosa infections troublesome (Strateva et al., 2007).Recently, resistance rates of P. aeruginosa clinical isolates recovered from patients admitted to Zagazig University hospitals in Egypt against different classes of antimicrobial agents were reported (El Zowalaty, 2012). The current study further examined the susceptibilities and possible resistance mechanisms of P. aeruginosa isolates collected from hospitalized patients against selected antipseudomonal agents that are available in the Egyptian pharmaceutical market and are frequently prescribed to patients.
Experimental
Materials and MethodsStudy site. The specimens were collected from ...