The early treatment of urinary tract infections (UTIs) is directly related to decrease in morbidity, which makes the empirical treatment of great importance. Recently, beta lactamases of several types have emerged as significant mechanisms of resistance in Gram-negative bacilli, especially Escherichia coli. Our aim was to study the urinary E. coli isolated from Lebanese patients and to characterize their mechanisms of resistance. The study analyzed data between 2005 and 2012 of UTIs caused by E. coli. The mechanisms of resistance were characterized by phenotypic and genotypic methods and the pulsed-field gel electrophoresis (PFGE) was used to determine the different bacterial clusters. As expected, the highest incidence was observed with E. coli (60.53–73.98%) followed by K. pneumoniae (5.32–8.33%). ICU isolates were constantly associated with the lowest rates of susceptibility to extended-spectrum cephalosporins, ciprofloxacin, as well as most of the tested antibiotics. A 100% occurrence of CTX-M in extended-spectrum β-lactamase (ESBL)-producing isolates was recorded, followed by TEM, SHV, and OXA. In addition, 15.9% harbored 4 different ESBL enzymes and only 13 isolates (14.8%) harbored only one enzyme (CTX-M). Over the years, the simultaneous susceptibility of E. coli to ceftazidime and ciprofloxacin decreased from 62.5% in 2006 to 48.7% in 2012. PFGE results demonstrated that 10 clusters were 32 generated, denoting diversity among detected isolates. Understanding the epidemiology of resistance is 33 instrumental for the implementation of recommendations for the management of antimicrobials, infection 34 control measures, as well as active surveillance and antimicrobial stewardship.

Extended-spectrum beta-lactamases (ESBL) and carbapenemase-producing organisms pose severe problems for hospitalized patients. In the absence of efficient sanitation and sewage disposal, the risks for transmission of hospital organisms into the community are high. Our objectives were to study the occurrence and mechanisms of resistance of multidrug-resistant gram-negative bacilli in two Lebanese hospital sewage treatment plants. Wastewater samples were collected, filtered, and cultivated on MacConckey+cefotaxime agars. ESBL, AmpC, metallo-β-lactamases (MBL), and Klebsiella pneumoniae Carbapenemases (KPC) production were phenotypically detected using plain Mueller Hinton agar plates, and plates impregnated with 5 mM EDTA, 10 mg/mL phenyl boronic acid, and 250 μg/mL cloxacillin (embedded). Temocillin discs were used for the presumptive detection of OXAs. ESBL, carbapenemase, outer membrane protein F (OMPF), and outer membrane protein C (OMPC) genes were detected using polymerase chain reaction. Pulsed-field gel electrophoresis (PFGE) was performed to study the clonality of Enterobacter cloacae isolates. In total, 32 and 38 Enterobacteriaceae were detected from Hospital 1 and Hospital 2, respectively. All Escherichia coli and Klebsiella spp. isolates were ESBL producers. AmpC reached 25% and 28.9% of all isolates. Only one Enterobacter cloacae isolate from one hospital showed full resistance to carbapenems. Molecular tests, however, detected NDM-1 in two strains of Enterobacter cloacae. PFGE results showed 80% similarity between these two strains. The isolation of NDM-1-producing Enterobacter cloacae from hospital wastewater occurred almost a year before the first case of carbapenem-resistant Enterobacter spp. was detected from a patient sample in the laboratory hospital. Understanding the local epidemiology of resistance in hospitals should include areas of potential resistance, such as wastewater and hospital environment.

Background: Intubated patients are particularly at risk of developing infections caused by these pathogens, specifically, P. aeruginosa and A. baumannii. In the past fifteen years, Carbapenems were known to be the drugs of choice for these bacteria. With the increase in the use and misuse of antibiotics, these bacteria became highly resistant, and almost all available antibiotics, including Carbapenems, became inefficient. Synergistic combination therapy may be a useful strategy in slowing as well as overcoming the emergence of resistance. The aim of this study was to evaluate the antibacterial activity on P. aeruginosa and A. baumannii of the combination of two antibiotics: Colistin and a Carbapenem (Meropenem or Imipenem). Methods: The antibacterial activity was assessed by determining the MIC. Then, the effect of combining the antibiotics was studied using the Checkerboard Technique described by White et al., 1996. The Fractional Inhibitory Concentration (FIC) for each strain was then calculated and classified as synergy, additive, indifference or antagonism. 11 strains of A. baumannii and 11 strains of P. aeruginosa were tested in the presence of Meropenem combined with Colistin or Imipenem combined with Colistin. Results: For the combination of Meropenem and Colistin, 6 strains of A. baumannii and 3 strains of P. aeruginosa showed synergy while 5 strains of A. baumannii and 7 strains of P. aeruginosa showed additive effect, only 1 strain of P. aeruginosa showed antagonism. For Imipenem and Colistin, only 1 strain of A. baumannii and 3 strains of Pseudomonas showed synergy while 8 strains of Acinetobacter and 8 strains of Pseudomonas showed additive effect. Conclusion: The "in vitro" combination Colistin-Carbapenem is associated with an improvement in MIC. In the majority of the cases, this improvement suggests a synergistic combination or an additive effect.

Introduction: The aim of this work was to study the ability of ciprofloxacin to restrict the development of resistant mutants of Escherichia coli and Klebsiella pneumoniae through determination of the Mutant Prevention Concentration (MPC). Methodology: We studied 140 strains of E. coli and 86 strains of K. pneumoniae with different profiles of sensitivity to fluoroquinolones and extended spectrum beta lactamase (ESBL) production. The MPCs were determined using an inoculum of 10 10 CFU/ml in Mueller-Hinton agar plates with serial concentrations of ciprofloxacin. Results: Ciprofloxacin-susceptible ESBL-producing strains showed a higher MPC for ciprofloxacin (P <0.001) than ciprofloxacin-susceptible non ESBL-producing strains, while ciprofloxacin-resistant ESBL-producing and non ESBL-producing strains did not significantly differ. The presence of qnr variants was associated with elevated MPCs. This was observed for both tested organisms.

The relationship between antibiotic consumption and resistance has been widely evaluated. Pseudomonas aeruginosa is one of the most important opportunistic pathogens in the nosocomial setting, and its resistance to antibiotics is increasing. Production of metallo-β-lactamases (MBLs) is currently the most fearful resistance mechanism due to the potential of dissemination. This study aimed to evaluate the correlation between antibiotic consumption (expressed in DDD/100 bed days) and resistance (expressed in % of isolates and patients) in different time periods for P. aeruginosa between 2006 and 2009 at Saint George Hospital University Medical Center (SGH-UMC), Beirut. Pearson correlation coefficients (r) were calculated and linear regression was performed. Detection of MBL-producing Imipenem resistant P. aeruginosa (IRPA) isolates between 2008 and 2009 was performed using three MBL screening methods: MBL Etest®, Imipenem/EDTA combined disk test and EDTA disk potentiation with four cephalosporins. The modified Hodge test was also performed. From 2006 till 2009, there was a trend of increasing resistance of P. aeruginosa to all antibiotics, and the highest % of resistance was for Ofloxacin. Concerning resistance expressed by isolates, high correlation coefficients resulted among Imipenem, Ciprofloxacin and Tazobactam consumption and resistance to these agents in the same year correlation; Ceftazidime and Ofloxacin consumption and resistance in the next year correlation; Gentamicin and Ofloxacin consumption and the change in resistance (ΔR). Concerning resistance expressed by patients, results were similar except for Ceftazidime and Ofloxacin correlation in the next year correlation. In MBL screening, three isolates gave accordance among 4 methods which showed a positive result. The correlation between antibiotic consumption and resistance is highly dependent on the kind of antibiotic, the organism and the time of correlation. Various MBL screening phenotypic methods on one isolate can increase accuracy and eliminate false positive and negative results.