Antimicrobial susceptibility of Escherichia coli Isolates from Clinical Specimens in Children over a 5-Year Period in Jordan

The present study was conducted to investigate antimicrobial susceptibility pattern of Escherichia coli strains isolated from clinical specimens of Jordanian pediatric patients during a five year period 2005-2009. A total of 2259 E. coli strains were isolated from different clinical specimens and tested for their susceptibility to commonly used antimicrobial agents. Overall, high susceptibility rate was observed for nitrofurantoin (90.4%), followed by ciprofloxacin (85.6%), norfloxacin (83.9%), cefotaxime (83.7%), ceftriaxone (82.4%), and gentamicin (80.8%). Lower susceptibility rates were observed for ampicillin (19.8%) followed by amoxicillin-clavulanic acid (26.8%) and cotrimoxazole (31.6%). Nitrofurantoin was highly effective for E. coli with susceptibility rate of 90.4%. In contrast, ampicillin, amoxicillin-clavulanic acid and cotrimoxazole were found to be ineffective at in vitro for inhibition of the E. coli of pediatric origin.


INTRODUCTION
Antimicrobial resistance has become a serious public health problem worldwide.Infections caused by resistant bacteria have been shown to be more frequently associated with increased morbidity and mortality than those caused by susceptible pathogens 1,2 .In areas of concentrated use, such as hospitals, this had led to lengthened hospital stays, increased health care costs and in extreme cases, to untreatable infections 3 .
The main cause of nosocomial infections in humans is Escherichia coli.It's also a common inhabitant of the human and animal gut and is considered an indicator of fecal contamination in food.E. coli is one of the organisms most frequently isolated from different clinical cases of diarrhea and others 4,5 .Several factors results in increasing antimicrobial drug resistance rates in poor countries such as irrational antimicrobial drug usage and conditions of poor sanitation [4][5][6] .Many studies have demonstrated increases in antimicrobial resistance among pathogenic bacteria after introduction of an antimicrobial 7,8 .Despite world-wide use of antibiotics, the distribution of the resistance is far from being uniform even in the same area 9 .However, there is little information on antimicrobial resistance pattern in Jordan.Therefore, this retrospective study was conducted to determine susceptibility rate to commonly used antibiotics by E. coli strains isolated from cultures of different clinical specimens received from pediatric patients at Princess Rahmah Hospital during a five year period 2005-2009.

MATERIALS AND METHODS
This study was carried out in the diagnostic Medical Microbiology Laboratory of Princess Rahmah Hospital located in Irbid, Jordan, during 2005-2009.A total of 2259 bacterial isolates were identified from different clinical specimens using standard bacteriological methods.These clinical specimens included urine, blood, ear and conjunctival swabs.Microbiological and antibacterial susceptibility data of this study obtained from records of diagnostic Medical Microbiology Laboratory of Princess Rahmah Hospital.These data were filled in a prepared data sheet.The antimicrobial susceptibility patterns of these isolates to antibiotics were determined using the Kirby-Bauer method of disc diffusion test 10 .The isolates were tested against the following antibiotics; amikacin, amoxicillin-clavulanic acid, ampicillin, cefaclor, cefixime, cefotaxime, ceftazidime, ceftriaxone, cephalothin, cephalexin, ciprofloxacin, cotrimoxazole, gentamicin, nalidixic acid, nitrofurantoin and norfloxacin.The study protocol was approved by the Ethics Committee of the ministry of health in Jordan (MOH, REC, 08, 0057).

Statistical Analysis
Data were analyzed using SPSS (version15 for Windows) to calculate the frequencies and cross tables.

RESULTS
During a five year period (2005-2009), a total of 2259 positive E. coli cultures of pediatric patients aged below 15 years old were studied.The distribution of E. coli strains from various clinical specimens was shown in table 1.

DISCUSSION
This current study provides information regarding the distribution of pathogenic E. coli isolates and its antimicrobial susceptibility patterns in pediatric patients.Most E.coli strains isolated from urine samples (97%).This is likely related to contamination with colonic bacteria 11 .
Results of this study showed high resistance rate of E. coli isolates to antimicrobial agents tested.Similar findings regarding high potentials for developing resistance for pathogenic isolates of E.coli were reported in literature.[12] High resistance rate to ampicillin, amoxicillin-clavulanic acid and cotrimoxazole was obtained.These results coincide with results reported high resistance rate of E. coli isolates to ampicillin and amoxicillin in Jordan 13 and elsewhere 14,15 .This high resistance rate is may due to the widespread and lengthy use of these antibacterial drugs in the world including Jordan.Susceptibility rates of E. coli isolates from different clinical specimens was highly significant deceased (P<0.01) to ceftazidime, cefotaxime, cephalothin and nalidixic acid in comparison between the years of 2005 vs. 2009.By the way, amoxicillin-clavulanic acid, cephlexin and cotrimoxazole were also showed decreases in their activity, but this decrement was not significant.The  cause of decrement in the activity of above antimicrobial agents is may due to the widespread and lengthy use of these antimicrobial drugs in the world including Jordan.These results are in accordance with other studies that reported high resistance rates of E. coli isolates against various antibiotics from various clinical specimens [13][14][15] .
In contrast, susceptibility rates of E. coli isolated from different clinical specimens' showed improvement to ampicillin, cefaclor, nitrofurantoin, cefixime, ciprofloxacin, ceftriaxone, gentamicin, norfloxacin in comparison between the years of 2005 vs. 2009.This increment was highly significant (P<0.001) for ampicillin, cefaclor, nitrofurantoin.[18] .The cause of significant improvement in the activity of imipenem and pipracillin is may due to little use of these medicines in treatment of bacterial infection in children.
E. coli isolates remained to be relatively susceptible to third generation cephalosporins but exhibited moderate susceptibility rates to first and second generation cephalosporins.For example, high susceptibility rates to cefotaxime (83.7%), ceftriaxone (82.4%), ceftazidime (77.0%) and cefixime (71.8%) were observed in this study, which is similar to other findings reported in Jordan 13 and elsewhere 14 .However, high resistant rates of E. coli to third generation cephalosporins were reported in different studies 16,17 .Oral use of cefixime may results in increased its resistant rate compared to injectable third generation cephalosporins.Furthermore, E. coli in present study showed low resistant rate to fluoroquinolones i.e. ciprofloxacin and norfloxacin of 14.4 % and 16.1% respectively.Similar finding were reported in Jordan 13 .However, high resistant rates of E. coli to fluoroquinolones were reported else where 16,17 .
Over all antibacterial tested in this study, nitrofurantoin was the most effective agent against E. coli with susceptibility rate of 90.4%.This result coincide with a study reported a very low resistant rate of E. coli to nitrofurantoin even after 50 years of use 19 .
There are many possible reasons for increasing resistant rate of E. coli to common used antimicrobial drugs, including inappropriate and incorrect administration of antimicrobial agents in empiric therapies and lack of appropriate infection control strategies [20][21] .This problem indicates importance of performing antibiotic susceptibility testing before blind antibiotic therapy.

CONCLUSION
The data suggest that ampicillin, amoxicillin-clavulanic acid and cotrimoxazole should not be used in treating infections caused by pathogenic E. coli and other related bacteria in Jordan.These findings also reinforce the need for ongoing investigation to show trends in antibiotic resistance, which can help clinicians provide safe and effective empiric therapies.Moreover, the data would also help authorities to formulate antibacterial prescription policies.