*2.5. Antimicrobial Susceptibility Pattern of the Confirmed E. coli Strains*

The antimicrobial susceptibility test of the confirmed *E. coli* isolates was determined by the disc diffusion technique on Mueller Hinton agar (MHA) plates, following Clinical and Laboratory Standards Institute (CLSI) [26] guidelines. Fresh culture from the glycerol stock was streaked onto nutrient agar plates and incubated at 37 ◦C for 24 h. Colonies were transferred into a test tube of 5 mL of normal sterile saline, and adjusted to attain turbidity matching the 0.5 McFarland standard. The isolates were then streaked onto MHA plates, and disks infused with antimicrobial agents were dispensed onto the inoculated plates and incubated for 18 to 24 h at 37 ◦C. After incubation, the zones of inhibition were measured, and isolates were categorized as resistant or susceptible to the antimicrobial agents used, while those that were intermediate were considered resistant. The following eight commercial antibiotic discs: Amikacin (30 μg), ampicillin (10 μg), ceftazidime (30 μg), ciprofloxacin (5 μg), gentamicin (10 μg), norflaxacin (10 μg), tetracycline (30 μg), and trimethoprim (10 μg) were tested against the confirmed isolates.

#### *2.6. Interpretation of Multiple Antibiotic-Resistance Index (MARI)*

The multiple antibiotic resistance index (MAR Index) of isolates that exhibited resistance against the actions of three or more antibiotics which were tested was expressed as *x*/*y*, where *x* indicates the sum of antibiotics to which the isolate was resistant to and *y* indicates the number of antibiotics tested against the isolate. Multidrug resistance was interpreted as the display of resistance to three or more antibiotics used, whereas the MARI (multidrug antibiotic-resisted indices) of the isolates was approximated, as previously described by Krumperman [27]. The multiple antibiotic resistance index (MARI) = *w*/(*uxv*), where: *w* is the summation of antibiotics resistance scores of the isolates; *u* is the sum of antibiotics used; and *v* is the sum of isolates which resisted the antibiotics employed.

#### **3. Results**
