Gram Staining : A Positive Or Negative?

After selecting the unknown sample # 2, the gram stain technique was performed in order to correctly identify the microbes. Gram staining is considered a differential media because staining differentiates between gram negative and gram positive bacteria. The purpose of the gram stain is to give crucial information as to whether the bacteria has a positive or negative cell wall, provides rapid results to physicians, and identifies the shape and arrangement of the organisms. The gram stain of sample # 2 reveals that one of the unknown microbes is a gram negative bacillus/rod and the other is a gram negative coccus.

The EMB plate was used to isolate the gram negative rod because the EMB plate is selective for gram negative rods, inhibiting the growth of gram positive organisms. This will effectively isolate the gram negative bacteria, thus creating a pure colony. Furthermore, the EMB plate differentiates for a gram negative rod that has the enzyme to break down lactose or sucrose, releasing an acidic waste product. If the organism appears to be dark purple to black, then it means that the microbe can ferment lactose and sucrose. The purple colonies on the EMB plate reveal that the gram negative bacteria is able to ferment lactose and sucrose. A gram stain of the colonies from the EMB plate show only the gram negative rods thus making the colonies on the plates pure.

A BAP plate was chosen to isolate the gram positive coccus. The BAP plate was chosen instead of the MSA plate because Citrobracter freundii can grow and break down mannitol. If Citrobracter freundii, a gram negative rod, and Staphylococcus aureus, a gram positive coccus, were the two unknown bacteria in the sample, then it would be difficult to know which bacteria caused...

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...atient is immunocompromised from the chemotherapy for lymphoblastic leukemia; the longer she stayed at the hospital for treatment, the more susceptible she was to contract the UTI from Enterobacter aerogenes.

Klebsiella pneumoniae is one of the most common causes of urinary tract infections. The organism is a part of the normal flora in the intestines and can only be contracted in hospital settings just like Enterobacter aerogenes. Patients are immunocompromised and at the hospitals for long periods of time are highly likely to contract a UTI from Klebsiella pneumoniae. Healthy people are unlikely to contract a disease caused by the organism (Klebsiella). This bacteria is another possible cause of the UTI in the patient. She had a high risk of contracting the UTI from Klebsiella pneumoniae from her compromised immune system and the long hospital stay for treatment.