*3.1. Molecular Identification and Characterization of the Recovered E. coli Isolates*

A total of 260 presumptive *E. coli* isolates were obtained from the water samples following microbiological analysis. The presumptive isolates were confirmed by polymerase chain reaction techniques (PCR) targeting the *uidA* gene. Results showed that 41.2% (107/260) of the *E. coli* isolates were positive, as shown in Figure 2. The confirmed *E. coli* isolates were further characterized into different pathotypes using specific primers for each pathotype, and the result is shown in Table 2. A total number of 26 isolates belonging to the three pathotypes identified were isolated from the 3 sampling points (canal), while 47 isolates belonging to the three pathotypes identified were recovered from the 3 sampling points (beach).

**Figure 2.** PCR products of the amplification of the *uidA* gene (*E. coli*) Lane 1: 100 bp molecular weight marker; Lane 2: positive control (*E. coli* ATCC 25922); Lane 3: negative control; Lanes 4–13: positive isolates.


**Table 2.** Results of *E. coli* pathotypes.

*3.2. Antimicrobial Susceptibility Pattern of the Confirmed E. coli Pathotypes*

Of the 8 test antimicrobial agents which were selected, ampicillin had the highest resistance frequency (100%). Nevertheless, amikacin and gentamycin both had quite high frequencies of 98.6% (72/73), while 70 of the strains were resistant to ceftazidime, with a frequency of 95.9% (Figure 3). About 45 strains (93% of the NMEC strains) exhibited resistance to each of ampicillin, amikacin, gentamycin, tetracycline, and ceftazidime, while 9.1% (1/11) and 91% (10/11) of the EPEC strains displayed resistance to ciprofloxacin and tetracycline respectively. For NMEC, 26 strains showed a resistance frequency of 54.2% against ciprofloxacin. Similarly, the EIEC strains demonstrated resistance ranging between 7% (1/14) and 50% (7/14) to amikacin, ampicillin, ceftazidime, ciprofloxacin, gentamycin, norfloxacin tetracycline, and trimethoprim. The results from the *E. coli* isolates which were subjected to the selected antimicrobial agents are summarized in Figure 3, which highlights all the sensitivity percentages of the isolates. 23 isolates of the various strains identified showed resistance to 8 antibiotics (19 NMEC, 3 EPEC and 1 EIEC), while 19 strains showed resistance to 7 antibiotics (5 NMEC, 4 EPEC and 10 EIEC).

**Figure 3.** Sensitivity percentages of *E. coli* isolates to 8 antibacterial agents. The antibiotic susceptibility patterns of the isolates of the several antibiotics tested following the CLSI (Clinical and Laboratory Standards Institute) guideline [26] showed that the isolates displayed highest resistance to ampicillin (100%). The following is the order of the level of resistance exhibited against the remaining antibiotics; amikacin (96%), gentamycin (96%), ceftazidime (96%), tetracycline (92%), ciprofloxacin (85%), trimethoprim (84%), norflaxacin (62%). However, the isolates were mostly susceptible to norflaxacin.
