Pattern of antibiotic sensitivity of bacteria causing urinary tract infection in a private Medical College Hospital in

Introduction: Urinary tract infection (UTI) infection is a serious health problem affecting millions of people each year.1 It has been estimated that about six million patients visit out patient departments and about 300,000 are treated in the wards every year for UTI worldwide. Approximately, 10% of human population get UTI at some stage during their lives.2 In Bangladesh , 20-35% females experience at least one episode of UTI in their lives.3,4 Among school children the prevalence is 1% -4% in Bangladesh.5 According to the annual report published by Department of health services, 0.46% of total outdoor patients suffered from UTI and this was out of the total population of Nepal.2 Escherichia coli is the principle pathogen causing UTI, accounting for 75 – 90% in both inpatients and outpatients followed by Klebsiella, enterobacter, proteus, pseudomonas

and enterococcus were more often isolated from inpatients.7 Elsewhere, coagulase negative Staphylococci saprophyticus may be a common cause of UTI in some reports.8 At least 80% of the uncomplicated cystitis and pyelonephritis are due to E.coli.Whereas Proteus mirabilis and Klebsiella pneumoniae infection accounts 10% and 6% respectively.Also UTI caused by gram positive bacteria include Enterococcus, and streptococcus agalacticus.Staphylococcus especially coagulase negative staphylococci accounts for 5% to 15% of cases of uncomplicated cystitis.9 The antibiotic susceptibility patterns of UTI causing pathogens have been varying from time to time and from place to place in both community and hospital settings.10,11,12 Increasing drug resistance in pathogens is now a serious problem to treat diseases like malaria, Tuberculosis, diarrheal diseases, UTI etc. 13 The main cause of this issue is the improper and uncontrolled use of antibiotics as well as improper prescription, inappropriate dosage and duration of treatment.14,15 The genetic causes of drug resistance in pathogenic microorganisms are horizontal gene transfer via plasmid, transposons and bacteriophages, recombination of foreign DNA in bacteria chromosome and mutations in chromosomal loci.16 A large number of drug resistant bacteria have been discovered during the past decades as methecillin resistant Staphylococcus aureus (MRSA), 17 multi drug resistant Pseudomonas aeruginosa, 18 Serratia marcescens, 19 vancomycin resistant enterococci (VRE) 20 and extended spectrum beta lactamase (ESBL) resistant Enterococci, 21 which is a very serious public health issue mainly in developing countries where high level of poverty, poor hygienic conditions as well as fake and spurious drugs are in the circulation of medical practices.12 For all of the above reasons, this study was aimed to identify the most common etiologic agents responsible for urinary tract infection with determination the antimicrobial sensitivity pattern to the commonly used antibiotics.

Materials and methods:
This study was done in the department of Microbiology, Shahbuddin Medical College Hospital during the period of July 2008 to June 2009.The patients comprised both sexes and all age groups.Urine samples were collected by using ster-ile, dry, wide mouthed leak proof plastic container and analysed them for different organisms responsible for UTI.Standard method for isolaton and identificationof the organisms were carried out with all urine samples.Blood agar and MacConkey agar media were plated using a calibrated loop withdrawing 0.001 ml of urine sample.The bacterial colonies were counted and multiplied by 100 to give an estimate of the number of bacteria present per milliliter of urine.
Significant growth was determined as>10 5 colony forming units (CFU)/ ml of midstream urine samples and>10 2 CFU/ml of a catheter specimen.22 Gram negative bacteria were idendified by morphological study, oxidase test, routine biochemical tests such as motility test, indole and urease production and Triple Sugar Iron reaction.Gram positive bacteria were identified by catalase, coagulase and Novobiocin tests.Samples which showed significant colony count were taken into consideration and sensitivity pattern of the isolated organisms was determined by modified Kirby-Bauer technique using Mueller-Hinton agar.23 Interpretation of results was done measuring the sizes of zones of inhibition and reported according to "The Clinical Laboratory Standard Institute" (CLSI) guidelines.24 Antibiotics for uropathogens were tested include imipenam, cefodoxime, ciprofloxacin, nalidixic acid, erythromycin, methicillin, tetracycline, amikacin, cotrimoxazole, nitrofurantoin, ceftriaxone, cloxacillin, vancomycin, meropenam, cefoxitin, netilmicin and azithromycin.

Results:
During July 2008 to June 2009 a total of 555 urine samples were tested from patients of all age groups in both sexes.Among them 84 (15.13%) were culture positive (Table 1).

Discussion:
Urinary tract infection is one of the serious issues which needed an urgent medical attention in community.25

Conclusion:
In this present study, the main organism causing UTI is E.coli followed by Enterococci .Highest sensitivity was found to Netilmicin, Imipenem, Amikacin and Meropenam.We should use these drugs rationale so that they remain effective for treatment of UTI.As the commonly used drugs shows less sensitivity, further study is needed for newer drugs to fight against urinary tract infection.

Table 3 . Overall sensitivity and resistance of different antibiotics
The most effective management of UTI patients is the identification of pathogens and selection of effective antimicrobial agents against them.26 A total of 84 isolates were obtained from our study.Out of 84 isolates E.coli was significantly the most common isolated organism accounted 61 cases (72.62%) followed by Enterococci 11 cases(13.09),Proteus in 4(4.77%) patients, Pseudomonas in 3 cases (3.57%),Staphylococcus saprophyticus & Klebsiella 2(2.38%) in each cases and Gram positive cocci in 1(1.19%) case were isolated in this study.The present finding was in accordance with many other studies who showed predominance of Gram negative bacilli specially E.coli ranged between 75-90-%.6 A study done in BSMMU, Dhaka by Anis showed E.coli (92%) as the commonest organism followed by Pseudomonas, Enterococci, Klebsiella and Proteus.27 Another study done by Ronald showed that E.coli remains the predominant Figure 1: shows the percentage-wise distribution of organisms among UTI subjects

Table 2 . Distribution of bacteria in urine samples
High incidence of resistance to these drugs specially Ampicillin has also reported by other workers in developing countries 34 .This may be due to inadequate dosages of these antibiotics used during self medication in our community is like to be a factor contributing to development of resistance.Therefore drug resistance is a common problem and need is for judicious use of antimicrobial agents after laboratory monitoring.