Question

2 Search Case Study #8.pdf (page 2 of 6) A 29-year old immunocompromised female is admitted to the hospital with flu-like symptoms, personality changes, uncoordinated muscle movements, and seizures. Her husband states that she attended a wine and cheese tasting charity event the week prior. The attending physician performs a lumbar puncture to rule out meningitis. Cerebral spinal fluid (CSF) was sent to the lab for gram stain and routine culture. CSF is abnormally cloudy Gram Stain on CSF Organism on BAP after overnight incubation

Answer 1

Answer: The isolated bacterium is Gram positive Rods and belongs to Listeria Spp and is Listeria monocytogenes

From the case presented is it evident that the infection is food borne (through cheese). The patient has complained of flu like symptoms, uncoordinated muscle movements, personality changes and seizures, hence CSF sample was collected and sent to lab for testing.

Gram staining was performed of CSF and it is observed that it shows presence of Gram Positive bacilli (rods) and organisms grows on blood agar plate ( BAP) with overnight incubation and shows zone of haemolysis around the colony, both of this indicates that the organism has crossed the blood brain barrier and is able to grow in CSF.

Typically a patient suffering from Listeriosis shows muscle aches, nausea , diarrhea and if the infection has spread to nervous system , then symptoms such as headache , stiff neck , confusion , loss of balance can occur .

Hence from Gram staining of CSF, BAP results and symptoms of patient, it can be concluded that the organism is Gram Positive bacilli and has gained entry via contaminated food.

To further confirm the isolate TEST 1 to TEST 4 are performed, we shall discuss each test in detail.

TEST 1 rapid slide test:

This test detects presence of enzyme catalase. Catalase is an enzyme that catalyses release of oxygen from hydrogen peroxide (H2O2).It is test used to identify and differentiate bacteria. In this the case results shows presence of bubbles on slides in which the colony of the isolate is placed and thus the isolate is catalase positive. Up to this step we can say that the isolate is Gram Positive , haemolytic and catalase positive.

TEST 2 endospore staining test.

It is test which will show presence of endospore in the bacterial cells, endospores are inclusion body seen within bacterial cell using specific staining technique. The microscopy results do not show presence of any endospore, hence the organism is non endospore forming.

TEST 3 CAMP test

This test is useful in identification of both streptococcus agalactiae and many Gram positive rods including Listeria monocytogenes. This test is sort of confirmatory test for Listeria monocytogenes.

This test detects production of diffusible, thermostable, extracellular protein called as CAMP factor. This factor acts in combination with Beta lysin produced by Staphylococcus aureus and produced a zone of enhanced lysis of erythrocytes present in the blood agar media. In standard CAMP positive test a typical arrowhead clearing (zone) is seen at the junction of two organism when place right angle to each other.

In this case you can observe an enchained zone of arrow shaped clearing at the junction of S. aureus and Unknown organism, indicating that the organism is CAMP positive.

TEST 4 Agar motility test:

Motility test is also an important test for identification. The test results show here “umbrella shape Motility in semi solid medium, this is one of the unique characters exhibited by Listeria monocytogenes due presence of peritrichous Flagella and hence is actively motile.

Thus with initial tests such as Gram stain, source of infection and patients symptoms it can be said that the isolate belongs to Listeria Spp.

Further carrying out extra tests like TEST 1 rapid slide test, TEST 2 endospore staining test, TEST 3 CAMP test and TEST 4 Agar motility test it can be said that the organism is Listeria monocytogenes , which is a Gram Positive bacilli, non endospore forming , haemolytic , Catalase positive , highly motile, CAMP positive ,food borne pathogen