In the present study, the overall prevalence of UTI from both symptomatic and asymptomatic UTI diabetes patients was 9.8%. This rate is comparable to the rates reported from other studies in Ethiopia (Debre Tabor (10.9%) [20], Hawassa 13.8% [35], Addis Ababa 10.9% [36]), India 12.2% [18] and Romania (10.7%) [37]. However, much higher prevalence rates were reported from Bahir Dar (30.5%) [38], and Arbaminch (33.8%) [39] in Ethiopia, Sudan (19.5%) [40], India (22%) [21], Pakistan (52.76%) (41)], Egypt (52.2%) [19], and Nepal (54.25%) [42]. Inclusion of asymptomatic DM patients and exclusion of catheterized DM patients, which is a known determinant factor that may increase the prevalence of UTI [19, 42], could be reasons for detecting lower prevalence of UTI in our study compared to the latter reports.
In the present study, 22 bacterial uropathogens belonging to five species were isolated. Gram-negative bacteria were more prevalent (81.8%) than Gram-positive bacteria (18.2%), as has been the case in most studies conducted elsewhere in the world. Our finding of high Gram–negative bacterial isolates in DM patients is in concordance with reports from Mekelle (83%) [43],India (92%) [44] and Sudan (87.2%) [40]. However, relatively lower prevalence were reported from other similar studies in Ethiopia such as in Debre Tabor (41.9%) [20] and Bahir Dar (61.9%) [45].
Generally, in the present study (63.6%) and in most other studies conducted elsewhere (Pakistan (60.0%) [24], India 67.6% [46], Dessie, 63% (47)], Sudan 54.6% [40] and Romania (68.9%) [37], E. coli was the most frequently isolated uropathogen. This dominance of E. coli among UTI patients may not be surprising since it is the commonest flora of the gastrointestinal tract and bowel from which it ascends to urinary tract where it uses its well characterized virulence factors to colonize the urinary tracts. The second leading bacterial isolate in our study was K. pneumoniae (13.7%), as was true for reports from Bahir Dar [38], Dessie [47], Sudan [40] and Nigeria [22]. On the contrary, Proteus species, Pseudomonas species and CoNs were reported to be the second abundant bacterial isolates from UTI from studies in Addis Ababa [48], Bahir Dar [49] and Pakistan [24], respectively.
In the present study, small proportion of Enterococcus species and CoNs were isolated each with the rate of 9.1% among the overall bacterial isolates. The 9.1% prevalence rate for Enterococcus species was also reported from Sudan [40]. However, S. aureus and S. saprophyticus in Debre Tabor [20], S. saprophyticus in Bahir Dar [49], S. aureus in Arbaminch [39] and CoNs in Dessie [47] were the leading Gram-positive isolates, showing variations in the dominance of UTI bacterial isolates among the different geographic locations in Ethiopia.
In the present study, duration of DM was shown to be an important risk factor for UTI development (p = 0.003), as evidenced by proportion of significant bacteriuria being observed more (17.2%) from those with diabetic history of > 10 years than those (4.5%) who were diabetic for only < 10 years. This is likely to be because of the progressive nature of diabetics that may damage genitourinary system (neuropathy) leading to dysfunctional bladder thereby creating micturition abnormality, a condition important for the developments of UTI [19, 50]. In fact, previous other studies from Egypt [19] and India [51] also reported the same conclusion in that the longer duration of DM the higher the rate of UTI observed. However, some studies from Iran [52] and Addis Ababa [27] reported no statistically significant association between duration of diabetics and UTI.
Another identified risk factor associated with significant bacteriuria in this study was previous history of UTI. Sixty-nine of the study participants in the present study had history of previous UTI. However, 14 of the 22 (63.63%) participants with significant bacteriuria were among those who had previous history of UTI. In fact, the likelihood of developing significant bacteriuria was 4.709 times greater among participants with history of UTI than without (P < 0.05). Other in-country studies have reported the same trend of higher rate of significant bacteriuria among those with previous history of UTI [27, 29, 53]. However, two studies from Hawassa [35] and Arbaminch [39] reported a contradictory finding, where they found statistically significant association of significant bacteriuria among DM patients with no history of UTI. Probably the latter studies might have introduced real biases during recruitment of participants.
Only 97/225 (43.1%) of the participants in our study had symptoms of UTI. However, the majority (15/22; 68%) of participants with significant bacteriuria were among the symptomatic ones (p < 0.05). This is not unexpected, as was the case from reports of other studies [27, 36], because long duration of DM and delayed medical intervention are likely to result in renal defects that in turn would lead to occurrence of UTI symptoms. On the contrary, our finding disagrees with the studies conducted in Hawassa [35], Sudan [40] and Italy [53] where symptomatic UTI had no significant association with significant bacteriuria. The difference might be due to respondent bias in accurately telling the symptoms characterizing symptomatic UTI.
Of the three variables described above that were found in bivariate analysis to have had significant association to significant bacteriuria in this study, only previous history of UTI and current symptoms of UTI were found by multivariate analysis to be persistently associated with significant bacteriuria. Surprisingly, however, this finding was in contradiction with the reports from the Sudan [40], where duration of diabetics and previous history of UTI had no significant association with significant bacteriuria in multivariate analysis. Moreover, in reports of other studies in Ethiopia, multivariate analysis showed previous history UTI to have had statistically significant association with significant culture positive bacteria in diabetic patients [35, 53]. However, other variables such as gender in Harar [53] and educational status in Hawassa [35] were also as important in this association, which were not even significant by bivariate analysis in our study.
Regarding antimicrobial sensitivity test results, the Gram-negative uropathogens were highly sensitive to meropenem (100%), nitrofurantoin (100%) and gentamicin (88.9%). The latter two antimicrobials were also shown previously to be highly effective against Gram-negative bacteria with sensitivity of 95.5% and 73.3% for nitrofurantoin and gentamicin, respectively from Dessie, Ethiopia [47]. A 100% sensitivity to nitrofurantoin was also recorded from a study in Arbaminch [39] and Gondar [29].
In the contrary, high level resistance was exhibited by the Gram-negative isolates against a number of tested antimicrobials that are commonly used against bacterial UTI: ampicillin (100%), doxycycline (100%), cefuroxime (100%), amoxacillin-clavulanate (94.4%), co-trimoxazole (72.2%), and ciprofloxacin (61.1%). The most disturbing observation in this connection is that all the Gram-negative isolates had shown resistance to more than at least one antimicrobial in three classes tested (100% MDR level). Such high levels of resistance among uropathogens against these same antimicrobials seems widespread both in Ethiopia (E.g. 91.4% against ampicillin and 79.2% against amoxacillin-clavulanate [38], 100% against co-tromoxazole, greater than 75% against amoxacillin-clavulanate [53], and between 60–100% against ampicillin [18, 29, 35, 36]) and elsewhere in the world [18]. Still more studies have confirmed that detection of high MDR among the Gram-negative uropathogens is common both in Ethiopia and elsewhere [20, 35, 47, 49, 53]. The remarkably higher prevalence of resistance, including MDR, against these commonly prescribed antibiotics may be due to: their wider availability and ease of access outside treatment centers, and so, indiscriminate use of the drugs without prescription [55]; or/and fake drugs, sub-standard or expired drugs may circulate that are likely to be used for self-treatment; frequent use of broad-spectrum antibiotics as prophylactics; and lack of laboratory tests both AST and pathogen identification [32].
E. coli, the leading uropathogen in the present study, was 100% sensitive to meropenem and nitrofurantoin, and 87.5% to gentamicin, although a very high level of resistance was observed to doxycycline (100%), ampicillin (100%), cefuroxime (100%) and amoxacillin-clavulanate (92.9%). Such high sensitivity of E. coli to the former two antibiotics was also reported previously from the Sudan [40], where it was 100% and 86.3%sensitive to gentamicin and nitrofurantoin, respectively; and in Ethiopia, where it was observed to be 100% sensitive to nitrofurantoin in Addis Ababa [27] and Hawassa [35]. However, this pathogen has been found to exhibit very high resistance (100%) to Ampicillin, which is also supported by the report from Hawassa (100%) [35] and Bahir Dar [49]. On the contrary, the 92.2% and 100% resistance of E. coli to amoxacillin-clavulanate and ampicillin, respectively, in our study disagrees with the report from the Sudan [40] in that amoxacillin-clavulanate (sensitivity rate 90.9%) and ampicillin (sensitivity rate 72.7%) were presented as effective drugs. The deterioration in the effectiveness of amoxacillin-clavulanate and ampicillin against E. coli from UTI is a matter of concern, given the facts that the primary etiology of UTI infection for DM patients is this uropathogen, and these antimicrobials are among the most commonly used drugs in Ethiopia.
In the present study, the overall percentage of antimicrobial sensitivity of Gram-positive bacterial isolates to majority of the tested antibiotics was high. For instance, Enterococcus species were 100% sensitive to nitrofurantoin, ampicillin and vancomycin. Previous studies from Ethiopia and the Sudan [20, 29, 40] also reported same high sensitivity rate for the former two antibiotics. Similarly, CoNs were highly sensitive (100%) to six of the tested antimicrobials, namely, nitrofurantoin, Ciprofloxacin, co-trimoxazole, Gentamicin, Cefoxitin, and Doxycycline, which was also observed in other previous studies in Ethiopia, where 100% sensitivity were reported against doxycycline [20], gentamicin [35] and ampicillin [40].
Mixed result was observed in regards to resistance among the two Gram-positive bacterial species isolated, Enterococcus sp. and CoNs. On the one hand, Enterococcus isolates were 100% resistant to doxycycline but CoNs were 100% sensitive to this drug. On the other, resistance to Ciprofloxacin was 50% for Enterococcus while it was 0% to CoNs. Moreover, CoNs isolates were 100% resistant to Penicillin, as was the cases in other studies elsewhere [35, 54]. Overall, gram positive isolates presented better options for empiric treatment than the gram negative isolates since they were 100% sensitive to all tested antimicrobial drugs except 100% resistance to penicillin and doxycycline.