Abstract
A urine dipstick test used for prompt diagnosis of urinary tract infection (UTI) is a rapid and cost-effective method. The main objective of this study was to compare the efficacy of the urine dipstick test with culture methods in screening for UTIs along with the detection of the blaCTX-M gene in extended spectrum β-lactamase (ESBL)-producing Escherichia coli. A total of 217 mid-stream urine samples were collected from UTI-suspected patients attending Bharatpur Hospital, Chitwan, and tested by dipstick test strip (COMBI-10SL, Germany) prior to the culture. E. coli isolates were identified by standard microbiological procedures and subjected to antimicrobial susceptibility testing by Kirby Bauer disc diffusion method following CLSI guideline. Primary screening of ESBL-producing E. coli isolates was conducted using ceftriaxone, cefotaxime and ceftazidime discs and phenotypically confirmed by combined disk diffusion test. Plasmid DNA of ESBL-producing strains was extracted by phenol-chloroform method and subjected to PCR for detection of the blaCTX-M gene. Out of 217 urine samples, 48 (22.12%) showed significant bacteriuria. Among 46 (21.20%) Gram negative bacteria recovered, the predominant one was E. coli 37 (77.08%) of which 33 (89.19%) were multidrug resistant (MDR). E. coli isolates showed a higher degree of resistance towards cefazolin (62.16%) while 81.08% of the isolates were sensitive towards amikacin followed by nitrofurantoin (70.27%). Among 14 (37.84%) phenotypically confirmed ESBL isolates, only eight (21.62%) isolates carried the blaCTX-M gene. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of urine dipstick test were 43.75%, 77.51%, 35.59% and 82.91%, respectively. Besides, the use of dipstick test strip for screening UTI was associated with many false positive and negative results as compared to the gold standard culture method. Hence, dipstick nitrite test alone should not be used as sole method for screening UTIs.
Highlights
Urinary tract infection is the second most frequent infectious disease that probably affects one-half of all people during their lifetimes
A urinary tract infection (UTI) is a severe public health problem caused by a variety of pathogens, but most frequently by Escherichia coli followed by Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, Staphylococcus saprophyticus, Staphylococcus aureus, and Pseudomonas aeruginosa [4,5,6]
Several tests are available for the diagnosis of UTIs, but the semi-quantitative culture of urine specimen is the only method for the detailed documentation of a bacterial urine infection [9]
Summary
Urinary tract infection is the second most frequent infectious disease that probably affects one-half of all people during their lifetimes. UTIs mean the presence of microbial pathogens causing the infection within the urinary tract [1]. The dipstick strip is considered to be one of the qualitative diagnostic tools [10] which include reagent pads such as nitrite, leukocyte esterase, specific gravity, pH, protein, glucose, ketones, bilirubin, urobilinogen and blood [11]. It is associated with many false positive and negative results as compared to the gold standard culture method
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