The goal of this investigation was to develop
a protocol that could exploit the method of enrichment culture as a means
for isolating Streptococcus lactis from fresh whole milk. Literature
sources show that S. lactis exhibits the following
characteristics:
Facultativley anaerobic
Gram positive
Cocci shaped cells
Non-motile
Not capsule forming
Asporogenic
Catalase Negative
Oxidase Negative
Mesophilic (grows best between 25-35o
C)
Gamma-hemolysis
Pinpoint, smooth, non-pigmented colony formations
Lactose and glucose fermenting
A tomato juice agar growth medium was selected to perform
initial streak plates of fresh milk. After 48 hours at 37oC
the streak plates yielded growth showing the desired colonial characteristics.
These colonies were then used to perform confirmatory assays to determine
the identity of the isolate present. The confirmatory assays that were
chosen tested all of the characteristics that were previously highlighted
in this summary. Every test indicated the presence of S. lactis
with the exception of an assay meant to detemine the ability of the isolate
to ferment lactose. Since this test was not consistent it must be concluded
that the organism assayed was not S. lactis. A protocol appears
that would exploit the confirmed characteristics of the isolated organism
assayed in this investigation.
