Although, using pour plates alternatively instead of XLD agar plates could of possible allowed acid to inhibit growth, potentially allowing to give much better and accurate results. For future experiments and more successful results, milk is a perfect environment for the growth of salmonella; survival of salmonella stops as acid counteracts. XLD agar, which is a particular growth medium, was used, which differentiates salmonella from shigella. Due to lack of equipment, during this experiment we used XLD agar plates, using pour plates instead of the XLD plates could have possibly made a difference with the results ensuring there is growth of salmonella.
Escherichia coli (E. coli) is a member of the Enterobacteriaceae family of organisms. It is a non-spore forming, facultative anaerobic, gram negative rod capable of growing on a variety of media and, similar to other members of the Enterobacteriaceae family, contains the enterobacterial common antigen. Most E. coli are part of the normal flora of the human gastrointestinal tract, however some strains are pathogenic and capable of causing clinical disease. Epidemiologic classification of E. coli is based on the expression of certain surface antigens. The three of greatest importance are the somatic O polysaccharide (part of the lipopolysaccharide or Gram negative endotoxin), the K antigens (part of the capsule), and the H antigens (flagellin proteins).
A positive result changes to a dark color and a negative test did not. This result shows that my bacteria do not ferment the sugars glucose, lactose and sucrose. Bacteria that can ferment these three sugars have the ability to produce hydrogen sulfide gas. The Gelatin test was to determine whether or not the organism has the enzyme gelatinase that hydrolyzes gelatin. A gelatin broth was obtained and was stabbed with the unknown bacteria.
Work cited Coburn, Bryan. Salmonella, the host and disease: a brief review. 2007. Curtello, Suzette. "The Effectiveness Of Antibiotics In The Prevention Of Salmonella Typhimurium In Growing Chickens."
The other serovars of Salmonella can infect multiple different hosts. Salmonella bacteria that infect humans result in multiple different medical manifestations. Most Salmonella cause diarrhea and they can occasionally cause secondary bacteremia. The Salmonella serovar that causes the most severe medical response is the Salmonella enterica serovar Salmonella Typhi. It is a gram-negative bacterium but the way it invades and attacks the host is very different from most gram-negative bacteria.
Next an MSA test was done and the results showed that there was growth but no color change. This illustrates that the unkown bacteria could tolerate high salt concentration but not ferment mannitol. The MSA plate eliminated Streptococcus pneumonia and Streptococcus pyogenes as choices since the bacteria can’t grow in high salt concentration. Staphylococcus aureus could be eliminated because not only did the unknown bacteria grow but also it didn’t change color to yellow. Lastly a Catalase test was done by taking a colony from the Blood Agar plate... ... middle of paper ... ...imary stain and not pick up the counterstain.
The MAC agar plate containing B. megaterium, E. coli and P. vulgaris had a growth of P. vulgaris and E. coli. There was no growth of B. megaterium on the MacConkey plate. The colour of the E.coli colonies was pink while P. vulgaris growth appears beige colour. Q3 and Q4 MacConkey (MAC) agar is a medium in which selective to Gram negative bacteria and able to distinguish between fermenter bacteria and non-fermenter bacteria as well as pathogens. MAC agar contains peptone, crystal violet, pH indicator, lactose and bile salt (Sumbali and Mehrotra, 2009).
If the bacterium has the enzyme tryptophanase, indole will be ... ... middle of paper ... ...indole, it is motile, there is no urease present and there is no coagulase activity. By deduction and logical reasoning Unknown 10a was determined to be Escherichia coli. Unknown 10b is Staphylococcus epidermidis. According to Bergey’s Manual Staphylococcus bacteria are gram positive spherical cells that occur singly, in pairs or in irregular clusters. Unknown 10b was gram positive, spherical and occurred in clusters.
Salmonella typhi cells are aerobic, gram negative rods that affect the gastrointestinal tracts of humans, and occasionally the bloodstream. There are three antigenic structures of Salmonella: the H antigen, O antigen, and Vi antigen. The O antigens are responsible for the production of fever. They are located inside the cell wall which enables them to withstand heat. The H antigen is a protein structure that makes up the subunits of flagella, so only bacteria that is motile will have this antigen.
The Catalase Test indicated a positive result. This showed that the bacterium contained the enzyme catalase which converts hydrogen peroxide into water and gaseous oxygen. The positive control used for this test was Micrococcus and the negative control for this test was Entercoccus. The Sulfur Reduction, Indole Production, and Motility (SIM) Test results indicated that the bacterium lacked the enzymes cysteine reductase or thiosulfate reductase and thus was unable to reduce sulfur. The positive control used for sulfur reduction was Proteus mirabilis and the negative control used was Staphylococcus epidermidis.