Antibiotic Resistance Profile of E. coli Strains Isolated from Clinical Specimens and Food Samples in Egypt

A total of 147 E. coli strains were isolated from food samples and clinical specimens. The prevalence of E. coli in clinical specimens was much higher than in food samples. The antibiotic resistance profile of these strains was determined against 7 classes of antimicrobial agents (26 different members). Almost 90% of E. coli strains were resistant to at least one of the tested antibiotics. The highest antibiotic resistance was recorded against conventional Beta-lactams. However, this resistance was significantly lower when Beta-lactams combinations and cephalosporins were tested. The highest sensitivity of the isolates was to imepenem and polymyxin-B where all isolated E. coli strains were sensitive to imipenem. The resistance to tetracyclines, macrolides and sulfonamides/trimethoprim were almost in the same order of magnitude of 30-37%. The resistance to quinolones and aminoglycosides were 19 and 10 % respectively. Among isolated E. coli 52 strains (35%) exhibited multidrug resistance (MDR) pattern to equal or more than 3 antibiotics classes with different mode of action. Interestingly, MDR E. coli isolated from food samples was higher than those isolated from clinical specimens. Key word: E. coli Antibiotics Multi-drug resistance Food INTRODUCTION (19,000 in 1992) [8]. This problem was more complicated E. coli is an important member of the normal strains to 3 or even more classes of antibacterial agents intestinal microflora of humans and other mammals, it has belonging to different chemical classes by using various also been widely exploited as a cloning host in mechanisms [9]. The occurrence of MDR is very common recombinant DNA technology. However, E. coli is not a and mainly in Gram negative bacteria [10]. In this sense, laboratory workhorse or harmless intestinal inhabitant; it MDR clinical isolates of E. coli pathogenic strains are can also be a highly versatile and frequently deadly, commonly seen today in clinics representing a major pathogen [1]. Moreover, E. coli is well known with the healthcare problem with increased morbidity and mortality high genetic flexibility to acquire and/or transfer worldwide [11]. Moreover and a matter of fact resistance or virulence genes from or to other strains of antimicrobial resistance has been found not only in E. coli as well as other organisms [2, 3]. pathogenic strains but also in non-pathogenic ones No doubt that the growing problem of antimicrobial [12, 13]. resistance has become a significant public health concern In this prospective, this study was conducted to worldwide [4] and especially in developing countries [5] screen both clinical specimens as well as environmental as a result of overuse and misuse of antibiotics [6, 7]. (food) samples for the presence of E. coli strains. Consequently, antibiotic resistance presents a great The antibiogram of all isolated E. coli strains was challenge to the treatment of infections. According to determined against 26 different members of antibiotics the Centers for Disease Control and Prevention, representing 7 classes of antibiotics. Finally, the healthcare-related infections led to 98,987 deaths in the prevalence of MDR among these isolates was USA in 2002, almost five times higher than a decade ago investigated. through the emergence of multidrug resistant (MDR) Intl. J. Microbiol. Res., 3 (3): 176-182, 2012 177 MATERIALS AND METHODS from different sources. In all cases, p<0.05 was regarded All tests were conducted under aseptic conditions and in triplicates. RESULTS Screening, Isolation and Identification of E. coli Strains: Screening, Isolation and Identification of E. coli Strains: A total of 100 stool samples was collected from children Among the screened 100 clinical specimens 67 E. coli with acute diarrhea in presence or absence of clinical isolates were identified representing 67 % (Fig. 1A). While manifestations. All samples were collected using sterile only 80 isolates were identified as E. coli from those swabs and obtained from Abu-Reesh Hospital, Cairo, collected among the screened different 1000 food samples Egypt. Each swab was dispersed in 5 ml sterile saline representing (8%) (Fig. 1B). solution prior to cultivation. Concurrently, a total of 1000 food samples was obtained from different food products Antibiotic Resistance Profile of Isolated E. coli Strains: (Ground roasted, beef lamb, turkey, chickens, salad vegetables, raw milk, cheese, koshari, etc.), available in retail stores and restaurants. Food samples were collected in sterile screw capped jars and stored at 4°C prior analysis. Initially, 1-2 grams of each food sample was transferred into sterile flasks containing 20 ml saline solution prior to cultivation. For all samples cultivation was conducted by transferring one ml of the resulted suspension into sterile Petri dishes. Then 15 ml molten sterile MacConkey agar at 45°C was added and mixed well. All plates were incubated at 37°C for 24-48 h. Preliminary identification of the isolated bacterial strains was conducted by morphological examination using Gram stain according to Bergey’s Manual of Systematic Bacteriology, [14] and biochemical regimen by API 20E (BioMérieux, France) according to the manufacturer instructions. Finally the identification was better confirmed using E. coli chromogenic agar medium (Oxoid, USA) [15]. Antibiotic Susceptibility Testing of E. coli Isolates: The antibiotic susceptibility testing was conducted using disc diffusion method (Kirby-Bauer method) using Mueller-Hinton agar (Difco, MI, USA) according to the guidelines of the Clinical and Laboratory Standards Institute [16]. All E. coli isolates were tested against 26 different members of antibiotics representing 7 different antibiotic classes. The antibiotics used were in the form of commercially available antimicrobial discs (Himedia, India). The susceptibility pattern of the tested isolates was determined according to the resulted zone of inhibition based on the standard data base [16]. The Statistical Analysis: All data were entered into Fig. 1: The recorded prevalence (%) of the isolated E. SPSS/PC software and comparative statistics were coli strains compared to the E. coli free samples calculated using a non parametric Mann-Whitney test to collected from 100 clinical samples (A) and 1000 estimate the resistance rates between the E. coli isolates food sample (B). as statistically significant depending on median. When conventional Beta-lactams represented by ampicillin was tested 85 and 95% of the E. coli isolates from food and clinical origins respectively showed resistance. When combinations of conventional Betalactams with Beta-lactamase suicidal inhibitor were tested the recorded resistance was much lower (Table 1). Only 15-20 % of the isolated E. coli strains were resistant to cephalosporins and new generation of Beta-lactams (Table 1). Interestingly, all isolated E. coli strains were sensitive to imipenem. Intl. J. Microbiol. Res., 3 (3): 176-182, 2012 178 Table 1: Antimicrobial susceptibility pattern of E. coli strains isolated from clinical and food samples Clinical Isolates (67) Food Isolates (80) ---------------------------------------------------------------Antibiotic class Tested members (conc. μg ml ) Sensitive Resistant Sensitive Resistant 1 Beta-lactams Conventional Beta-lactams: Ampicillin (AMP) (30) 15% (10) 85% (57) 5% (4) 95% (76) Combination Beta-lactams: Amoxacillin/Clavulanic acid (AMC) (20/10); Ampicillin/Sulbactam (A/S) (10), Pipracilline/Tazobactam (PIT) (10/10) 65.6% (44) 34.4 % (23) 91.25 % (73) 8.75 % (7) Cephalosporins Beta-lactams: Cefixime (CFM) (30), Cefoxitin (CX) (30), Cefotaxime (CTX) (30), Cefuroxime (CXM) (30) 79% (53) 21% (14) 78.75 % (63) 20.25 % (17) Newly used Beta-lactams: Imipenem (IMP) (15), Azetronam (AT) (30) 85% (57) 15 % (10) 98.75 % (79) 1.25 % (1) Quinolones Ciprofloxacin (CIP ) (5), Gatifloxacin (GAT) (5), Levofloxacin (LE) (5), Lomefloxacin (LOM) (10), Ofloxacine (OF) (5), Norfloxacin (NX) (10), Sparfloxacin (SPX) (10) 82% (55) 18 % (12) 81.25 % (65) 18.75 % (15) Aminoglycosides Amikacin (AK) (30), Kanamycin (K) (30), Tobramycin (TOB) ( 100/10), Neomycin (N) (300 units) 91% (61) 9% (6) 90 % (72) 10% (8) Tetracycline Doxycycline (DO) (5), Tetracycline (TE) (5) 63% (42) 37 % (25) 62.5% (50) 37.5% (30) Macrolides Azithromycin (AZM) (30) 69 % (46) 31 % (21) 66 % (53) 34 % (27) Polymxins Polymyxin-B (PB) (30) 98.5 % (66) 1.5 % (1) 97.5 % (78) 2.5 % (2)