ORIGINAL ARTICLE

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ANTIMICROBIAL SUSCEPTIBILITY OF COMMUNITY-ACQUIRED UROPATHOGENS IN GENERAL PRACTICE

Table 2: Percentage Distribution of Antimicrobial Resistance of Pathogens in Community-acquired UTI

Antimicrobial	Percentage (No. tested)
	Overall	E. coli	Klebsiella spp.
Ampicillin	63.0 (107)	62.0 (90)	90.0 (10)
Amoxycillin-clavulanate	3.7 (107)	3.3 (89)	11.0 ( 9)
Cefuroxime	1.0 (100)	0.0 (84)	0.0 (10)
Cephalexin	3.8 (104)	1.1 (90)	20.0 (10)
Sulphamethoxazole-Trimethoprim	40.1 (112)	42.0 (90)	30.0 (10)
Norfloxacin	8.6 (105)	8.8 (90)	10.0 (10)
Fosfomycin Trometamol	1.0 (104)	1.1 (90)	0.0 (10)
Pipemidic Acid	14.3 (105)	14.4 (90)	10.0 (10)

DISCUSSION

Laboratory diagnosis of UTI using urine cultures is based on the semi-quantitative counts of organisms and identification of the isolates. A known quantity of urine is streaked on solid agar media and incubated at 35 ± 2° C for 16-18 hours and the bacterial colonies counted. The reliability of this method, however, is strongly dependent on the time taken to send the urine specimen to the laboratory and the transport conditions because urine is an excellent culture medium and delayed plating may result in false-positive results. This was our principal concern in conducting the present study, as the urine specimens had to be transported by couriers on motorbikes. One solution was the use of commercial dipslides, in which the urine is inoculated on the device at the bedside. However, the method was not available locally. We circumvented the problem by direct inoculation of the culture plate as a bedside procedure. From the experience of studies using dipslides, bedside inoculation does not appear to affect the final results of urine cultures.⁹ Three percent of the samples in our study were contaminated; this compares favourably with a previous local study¹⁰ where 19% of urine samples were contaminated.

It is important to note that urine cultures are reserved for patients with complicated UTI or those who failed or relapsed after empiric therapy. In the outpatient setting, symptomatic patients with uncomplicated UTI are usually treated empirically, i.e. without urine cultures. However, other investigations may be helpful and each primary care physician has his own strategy. If empiric treatment is based on history alone then one would be treating at least 40% of patients without a UTI. This is because through history taking, the pretest probability of a UTI hardly exceeds 60%.⁹ In our study true UTI was present in only 52% of all patients with symptoms. Primary care physicians usually use urine dipstick or urine microscopy to help in the diagnosis and treatment. These investigations have their limitations.¹¹ Urine dipstick alone seems to be useful to rule out infection if the results of both nitrites and leukocyte-esterase are negative.¹² On the other hand, it is most interesting to note that from a practical standpoint, studies of urine do not seem to have much effect on the actual management of UTI by most primary care physicians. Nearly all patients with symptoms of dysuria, frequency and urgency receive antibiotics irrespective of the results of urinalysis and culture.^{13, 14}

The demographic data (Table 1) indicates that women of reproductive age group formed the main group of adult patients with UTI presenting to the general practice clinics (54% of all UTI detected were from women age 10-49 years). These were mainly cases of acute uncomplicated cystitis. Beyond the age of 50 years, cystitis was likely to be complicated by concomitant medical problems like diabetes. It is worthy of note that only a small percentage of older males with UTI (commonly complicated by prostatomegaly and other urinary tract disorders) was represented in this study. It was likely that these patients presented principally to secondary or tertiary healthcare facilities.

The overall frequency of infection and the pathogens involved were broadly as expected. E. coli was the most common pathogen isolated, involving 77% of the positive samples. Klebsiella spp was the second common organism. Staphyloccocus saprophyticus, which is known to occur in a seasonal fashion, was seen only in a few cases. The majority of cases seen in general practice belonged to the class of uncomplicated acute cystitis in women, which comprised 64% of the UTI cases seen in this study. In a classic study by Rubin,¹⁵ E. coli was isolated in about 80% of uncomplicated cases of UTI. In our study, a similar 80% of uncomplicated acute cystitis grew E. coli. In fact, E. coli remained the most common pathogen for all the clinical manifestations and in all groups of patients.¹⁶ The microbiology of UTI, unlike other infectious diseases, has remained remarkably constant over the decades.¹⁷

E. coli, a member of the human colonic flora, is usually non-pathogenic. However, certain strains may acquire virulence factors and cause human diseases. There are three principal ones, the strains causing sepsis/meningitis, the enteropathogens and the uropathogens. Bacterial cystitis begins with the colonisation of the periurethral skin and the anterior urethra before entry into the bladder.¹⁸ Uropathogenic E. coli exhibits specific virulence factors, which allow them to adhere to vaginal and uroepithelial cells, resist bactericidal activity of human serum, prevent phagocytosis by leucocytes and production of specific cytotoxins for tissue invasion.¹⁹ Such virulence factors and uropathogenicity are not confined to E. coli, and has been shown with Proteus mirabilis and Klebsiella spp.^{20, 21}