**3.3 Pulsed-field gel electrophoresis**

The PFGE picture of all the isolates used for this study is partly represented in Figure 3 below. As depicted in the figure, the PFGE typing of the ESBL-producing isolates revealed various different and diverse DNA banding profiles among the *E. coli* and *K. pneumoniae*  isolates. Bacteriophage lambda ladder PFGE marker (New England Biolabs) is all depicted on the lanes λ. The *E. coli* isolates are demonstrated on lanes 1 – 6, 7 – 12 while lanes 13 – 18 and 19 – 24 shows the *K. pneumonia* isolates. Note that except for lanes 4 and 7, all the lanes containing the isolates have significantly divergent banding patterns. From these results therefore, one would interpret the data as stating that all the *E. coli* or *K. pneumoniae* isolates are distinguishable by the PFGE and divergent from each other (>7 band difference).

There was no major clonal similarity or relatedness of either the *K. pneumoniae* or *E. coli* producing ESBL isolates regardless of which hospital facility the patient was admitted to or specimen the bacterial pathogen was recovered from. In addition, one could notice that from the Figure 2, the bands of the DNA were not separated (i.e. no resolution) for isolates in lanes 4 and 7. This phenomenon is called smearing and occurs when there is a contamination of the nucleases (agarose plug, buffer or reagents), or use of abnormal temperature and concentration of the buffers or wrong conditions which may all affect the enzyme. All these were the case with these isolates because when the tests were repeated with only the two isolates the bands were fully separated.
