**2.4.3 Determination of the Minimum Inhibitory Concentration (MIC) of extract**

#### **2.4.3.1 Materials for Minimum Inhibitory Concentration (MIC) of extract**

Broth culture of test organism (s); known concentration of plant extracts (e.g. 0.5g/ml, 1g/ml etc); set of test tubes; micro-pipettor (adjustable 100µl-1000µl); Nutrient broth; Sterile physiological saline; incubator.

#### **2.4.3.2 Method for Minimum Inhibitory Concentration (MIC) of extract**

A set of test tubes were dispensed 0.5 ml (500µl) of physiological saline. An equal volume (i.e. 0.5ml) of test plant extract were added to the saline in first tube and mixed the two thoroughly well.

*In Vitro* Antimicrobial Activity of Crude Extracts of Erythrina abyssinica and Capsicum

The study found that the leaves extracts did not have antimicrobial activities.

**Plant Sample Location Plant part Weight of** 

from Mbarara, Bushenyi, Ntungamo and Rakai districts

*E. abbysinica* 

annum in Poultry Diseases Control in the South Western Agro-Ecological Zone of Uganda 603

Bushenyi respectively were effective against *Pseudomonas aeruginosa demonstrated in Table 3*.

Table 1. Percentage yield extract of leaves, root bark and stem bark of *Erythrina abbysinica*

Fig. 4. Percentage yield determination of plant extracts (*Erythrinna abbyssinica*)

**sample (g)** 

Ntungamo Root barks 450.0 39.6 8.8 Mbarara Root barks 295.6 37.8 12.8 Bushenyi Root barks 689.5 53.0 7.7 Rakai Root barks 500.0 24.3 4.9 Ntungamo Stem barks 537.0 11.6 2.2 Mbarara Stem barks 435.8 10.7 2.5 Bushenyi Stem barks 483.7 13.4 2.8 Rakai Stem barks 500.0 44.6 8.9 Ntungamo Leaves 500.1 3.2 0.6 Mbarara Leaves 451.7 3.2 0.7 Bushenyi Leaves 761.6 29.4 3.9 Rakai Leaves 500.0 31.1 6.2

**Dry weight of** 

**concentrate (g) % yield** 

This was repeated throughout all the test tube and the last aliquot 0.5 ml of solution from the last tube discarded so as to have uniform volume. This constituted a two fold serial dilution whereby each step moved to the right reduced the concentration of the extract by a factor of 2. About 100µl of a 24 hour culture of the test organism were added to each of the test tubes (containing the already serially diluted extract). This was mixed thoroughly well, plugged with cotton wool and incubated the preparation at 37oC for 16-24 hours.

At microbiology laboratory, the samples were each weighed and dissolved in Dimethylesulfoxide (DMSO) at a final concentration of 0.5g/ml. Mueller Hinton Agar (MHA) plates for antibiotic sensitivity testing were prepared and inoculated with pure colonies of *E. coli, Staphylococcus spp., Streptococcus spp., Salmonella spp., and Pseudomonas spp.,* which were known to be the common causes of poultry diseases.

The wells were bored in the inoculated plates and the samples from the extracts were impregnated into the wells and incubated overnight. A control plate inoculated with E. coli and impregnated with Dimethylesulfoxide (DMSO) and a known antibiotic, Ciprofloxacin was set up as negative and positive controls respectively.

After 24hrs of incubation, the plates were examined for antibacterial activity on the different sample extracts, and the results were as follows:
