Antimicrobial Sensitivity Pattern of Bacterial Pathogens Associated with Urinary Tract Infection

Background: Urinary tract infection (UTI) is one of the common bacterial infections in mankind. The changing antimicrobial sensitivity in UTI demands use of appropriate antibiotics. Objective: This study was conducted to determine the distribution and antimicrobial susceptibility of uropathogens. Materials and method: This was a prospective study conducted in Bangladesh Medical College & Hospital, Dhaka, Bangladesh between May 2016 to June 2017 to identify the organisms causing UTI and their antibiotic susceptibility. Clean catch midstream urine samples were collected from 95 patients presenting with symptoms of UTI. Antimicrobial susceptibility was performed by disc diffusion method. Results: Out of 95 urine samples, 56 (58.9%) were found positive. The prevalence was significantly higher in females than in males (females: 58.9%; males: 41%). Age group of >48 years showed higher prevalence of UTI. The most common organisms isolated were Escherichia coli, Klebsiella, Pseudomonas, Proteus and Staphylococcus aureus. These represented 44.6%, 21.4%, 14.3%, 12.5%, and 7.14% of isolates respectively. Imipenem and Meropenem were found the most susceptible drug against isolated uropathogens. Conclusion: Most powerful antibiotics in our study were imipenem and meropenem. In conclusion, one can truly affirm that the choice of drugs in the treatment of UTI is becoming quite narrow today due to the wide scale resistance that the common UTI pathogens show to drugs which have been used previously.


Introduction
Among the most common infectious diseases, urinary tract infections (UTIs) are commonly encountered by clinicians in developing countries. 1,2Urinary tract infections (UTI) affect any part of the urinary tract and include mainly cystitis (bladder infection), pyelonephritis (kidney infection) and urethritis (urethra infection) showing tissue damage, burning, painful urination, urgency and increased urinary frequency, suprapubic pain, pain in renal angle, fever and other systemic manifestations but asymptomatic cases may also occur. 3,4Presence of 105 cfu/mL 1. 2. 3.  4.  in midstream urine is considered as significant number of bacteria for UTI. 5 Effective management of patients suffering from bacterial UTIs commonly relies on the identification of the type of organisms that caused the disease and the selection of an effective antibiotic agent to the organism in question. 6UTI is more common in females than in males as female urethra is structurally found to be less effective for preventing the bacterial entry. 7It may be due to the proximity of the genital tract and urethra 8 and adherence of urothelial mucosa to the mucopolysaccharide lining. 9he vast majority of uncomplicated UTIs are caused by the Gram-negative bacillus Escherichia coli, with other pathogens including Staphylococcus, Klebsiella spp.and Proteus mirabilis. 10Extensive and inappropriate use of antimicrobial agents has invariably resulted in the development of antibiotic resistance which, in recent years, has become a major problem worldwide. 11The distribution of antimicrobial susceptibility data of UTI-causing microorganisms changes from time to time and from place to place. 12Increasing drug resistance in UTI needs regular monitoring of the antibiotic susceptibility of uropathogens in a particular area.

Materials and method
A total of 95 urine specimens were examined from patients who were suspected to have urinary tract infection, from May 2016 to June 2017.The study was performed at Bangladesh Medical College & Hospital, Dhaka, Bangladesh.Clean catch midstream urine was collected from each patient.All patients were well instructed on how to collect sample aseptically prior to sample collection to avoid contaminations from urethra.Qualitative microbiological analysis was performed with all the samples.The diagnosis of urinary tract infection was based on microscopic findings of more than 5 white blood cells (WBC) per high power field.Identification of organisms was done by conventional methods through culturing of samples followed by biochemical tests including their distinct colony characteristics.The inoculation at 37ºC for 48 hours and CFU count of 105/mL of urine were considered positive for UTI.The antibiotic sensitivity test was done on disc diffusion test.Interpretation as 'Sensitive' or 'Resistant' was done on the basis of the diameters of zones of inhibition of bacterial growth as recommended by the disc manufacturer.

Results
A total of 95 clinical urine samples were collected.Out of the collected 95 urine samples, 56 samples (58.9%) were found positive with one organism for each after culturing.Out of 56 urine samples which showed the significant bacterial growth, 23 (41.07%) samples were from males and 33 (58.9%) from females (Table I).The highest prevalence of UTI was found in the age group of >48 years (44.6%).(Table II) Of the 95 tested samples, total 56 urine samples showed significant bacterial growth.The pie chart (Fig 1 ) shows prevalence of UTI in patients was found to be 59%.Imipenem, meropenem, nitrofurantoin and amikacin showed the highest sensitivity against 92%, 92%, 88% and 84% E. coli.Imipenem and meropenem were found to be the most susceptible drug for K. pneumoniae with the rate of 91.6%.and 83%.In case of P. aeruginosa, the highest susceptible antibiotics were imipenem (87.5%), meropenem (87.5%) and amikacin (87.5%).Sensitivity of the Proteus was 85.7% against both Imipenem and meropenem.
Imipenem and meropenem were found to be 100% sensitive for S. aureus.(Table IV

Discussion
Out of the collected 95 urine samples, 56 samples (58.9%) were found positive.Our study also shows similarity to the study of Rahman et al. in non-diabetic patients. 14The prevalence rate of UTI in our study also correlates with other studies done in South Trinidad 15 , which showed highly significant uropathogens.In other studies prevalence rate of UTI accounted for 38.6% 16 , 35.5% 17 , 34.5% 18 , and 36.68% 19in India.
[28] The occurrence of UTI recorded among the elderly was highest in the age group of ≥48 years ( 45%).Our results agree with the study done in Japan with a 20-year period in which a trend of increasing complicated UTI was reported in elderly patients. 29e predominant isolates in our study were Escherichia coli (44.6%).[35][36][37] The sensitivity rate of carbepenems (meropenem vs. imipenem) among uropathogens was as follows: E. coli (92% vs. 92%), Klebsiella (83% vs. 91.6%),Proteus (85.7% vs. 85.7%),P. aeruginosa (87.5% vs. 87.5%),and S. aureus (100% vs. 100%).A study conducted in India showed that meropenem was highly sensitive against Gram negative bacilli whereas cephalosporin showed highest resistance against Gram negative rods. 38In other study, meropenem and imipenem were found to be 98% and 100% sensitive, respectively, against highly resistant gram negative bacilli. 39A study done in King Fahd Hospital, Saudi Arabia showed that meropenem was 95.8% sensitive followed by amikacin (93.7%) and imipenem (91.71%) against extended spectrum β lactamase producing E. coli. 40The high rate of resistance against fluoroquninolones was suggested by studies done in Spain, Europe, and Iran 41,42 and also by other studies done in India. 25,43,44Another study done in Spain also showed the reduced susceptibility of E. coli isolates from patients with UTI to Fluoroquinolones.This reduced susceptibility might be due to using antibiotics without restriction.][47]

Table III : Distribution of isolated uropathogens (n=56) Table IV: Antibiotic sensitivity pattern of isolated organism in UTI
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