Prevalence of E. coli-caused Conditions
In total, 98 strains were isolated from urine samples and 2 strains were isolated from uterine scrapings. 87 E. coli strains (87%) were isolated from females; whereas, 13 strains (13%) were isolated from males (Fig. 1). E. coli-caused conditions were more common among females, than males (p < 0.05) in all study groups and demonstrated the sex specific predisposition to infection.
Among 100 isolates, 53 isolates (53%) were recovered from infectious study group patients. 32 were recovered from non-infectious study group patients, and 15 were obtained from patients with unavailable clinical records. The most commonly observed infectious study group (53 cases) consisted of 20 confirmed UTI (37.7%), 19 with pyelonephritis (35.8%), 10 with cystitis (18.9%), two of endometritis and two of pyelonephritis with complications of urosepsis (3.8%), respectively (Table 1).
Thirty-two E. coli strains (32%) were isolated from pregnant women, who participated in a prenatal surveillance program. All strains caused ASB at the time of culture. One patient later developed unspecified UTI. Finally, 15 strains were isolated from patients with unavailable medical data (15%).
Age Distribution among Patients with E. coli-caused UTC
Among the 87 females, the age of the patients ranged from 2 to 90 years. Among 13 males, the age ranged from 2 to 89 years. The median age of females was 33 years, while observed median age among males was 44 years (Fig. 1).
Antimicrobial Susceptibility Patterns among UPEC
Among all E. coli strains, 86% showed resistance to at least one tested antimicrobial, while 22% of strains were resistant to 3 or more antibiotics. A high frequency of resistance to cephalosporins was observed; e.g., as 43% of strains was resistant to cefuroxime (Table 1). Lower levels of resistance to penicillins were observed; 32% of all tested isolates were resistant to ampicillin and 28% of E. coli strains showed resistance to amoxicillin/clavulanate. Ciprofloxacin resistance was detected in 31% of all isolates. Lastly, 16% of isolates showed resistance to trimethoprim. Lower resistance rates to aminoglycosides were observed during this study. The highest rates of resistance among tested aminoglycosides were observed to tobramycin (6%), and followed by amikacin (4%) and gentamicin (3%). Among tested isolates, 3% showed resistance to nitrofurantoin. Furthermore, all isolates were susceptible to carbapenems (meropenem and imipenem). Additionally, intermediate resistance to antibiotics was observed. In general, 25% of all tested E. coli demonstrated intermediate susceptibility to at least one antimicrobial. 9% showed intermediate susceptibility to tobramycin, 6% - to amikacin, and 5% - to trimethoprim (Table 1).
Serological Diversity among E. coli Strains Isolated from Patients with UTC
Among 100 isolates, 64% of E. coli isolates belonged to a serogroup associated with uropathogenicity, while the serogroup of remaining 36% tested E. coli isolates was not identified, hence belonged to other serogroups (Table 2). Among UTI-associated serogroups, O15 (32.8%), followed by O22 (23.4%), and O25 (15.6%).
Among all isolates belonged to UTI-associated serogroups and recovered from female patients, O15 (95.2%), O22 (86.7%), and O25 (100%) were the most common. Two (13.3%) out of 13 isolates, obtained from male patients, were identified as E. coli O22. Furthermore, 7 out of 13 isolates, obtained from male patients, were from serogroups not commonly associated with uropathogenicity (Table 2).
Serogroups O15 and O22 (17%) were the most prevalent among 53 E. coli isolates obtained from the infectious study group (Figure 2). Serogroups O8, O15, O18, O22, O25, of isolates from infectious group with clinically proven cystitis, represented a similar distribution of UTI-associated serogroups (1.9%), while the majority of the isolates represented non-UTI associated serogroups (9.4%). In the infectious group cases of pyelonephritis, serogroups O15 and O22 were the most prevalent and represented 7.6% and 11.3%, respectively, whereas serogroups of 11.3% were not identified (Fig. 2).
In the cases within the non-infectious study group, serogroups O15 (28.1%) and O22 (15.6%) were the most common isolates obtained from patients with ASB. However, serogroups of 28.1% of the isolates were not identifiable by used assay (Fig. 2).
Increased Multidrug Antimicrobial Resistance Observed among O15 Serogroup
Increased antimicrobial resistance levels were observed among E. coli UTI-associated serogroups in comparison to those of non-UTI associated serogroups. Increased resistance frequencies were observed among serogroups O15, O22, and O25. Those serogroups had demonstrated extensive resistance rates (resistance to two and more antibiotics) regardless of the diagnosis. 57.1% of O15 isolates indicated resistance to ciprofloxacin, and 71.4% were resistant to ampicillin. 60% of E. coli O22 was resistant to ciprofloxacin (Table 2). When compared to other UTI-associated serogroups, O15 showed significantly higher resistance (p=0.016) to ampicillin and trimethoprim (p=0.027) and was resistant to more than one antimicrobial agent.
Phylogenetic Diversity among E. coli Isolates
Phylogenetic group B2 was the most prevalent (50%) among analyzed population of E. coli, followed by group D that represented 25% of all isolates. Furthermore, 18% of isolates represented B1, while 7% was grouped as A. A similar proportion of distribution among E. coli phylogenetic groups was observed when isolates obtained from female patients were analyzed. A similar distribution was observed in the smaller group of males (Table 3).
- coli B2 was dominant (54.7%) and followed by D (24.5%) in infectious group. Group B2 was prevalent between both sexes in the infectious group (Table 3). The different distribution was observed in the non-infectious group, as group A was considerably more prevalent (12.5%) in comparison to those of other groups and conditions. Groups D and B2 were the most common and followed by low frequencies of group A in the group of unavailable medical data.
Phylogenetic group B2 were common among serogroup O22 (60%) and O25 (50%) isolates (Fig. 3).
Patterns of Antimicrobial Susceptibility among E. coli Phylogenetic Groups
Group B1 isolates showed highest resistance to ciprofloxacin (44.4%), while group A reached 28.6%, and was followed by B2 and D (28.0% and 28.0%, respectively). Highest resistance rates to amoxicillin/clavulanate were observed among group D (48.0%), while B1 and B2 reached 22.2% and 22%, respectively. Group A demonstrated lowest resistance rates (14.3%). Increased resistance to ampicillin was observed among the members of group A (42.9%) and D (36.0%), whereas B1 and B2 demonstrated 27.8% and 30.0% resistance. Isolates of A, D, B2, and B1 groups were highly resistant to cefuroxime (57.1%, 52%, 40%, and 33.3%, respectively) (Table 4). There were no significant differences between phylogenetic groups and association between bacteriuric and non-bacteriuric patient populations.