Question

A 59-year-old female stroke victim was confined temporarily to a respite nursing home because her immediate family was on a short vacation. Upon admission, she complained of a slight respiratory ailment. Three days later, she awoke with a stiff neck and a severe headache. Because of a high fever and other signs and symptoms of meningitis, she was transported to a nearby hospital emergency department, where a spinal tap was performed. The cerebrospinal fluid (CSF) was sent to the laboratory. The specimen was cloudy, had a high protein concentration, and more than 420 white blood cells (WBCs)/ml were noted; 92% were polymorphonuclear cells. The Gram-stained direct smear revealed many WBCs and many small, gram-negative bacilli; some appeared to be coccobacillary with clear halos around them. Cultures of the CSF and blood produced heavy bacterial growth on chocolate agar, but not on sheep blood or MacConkey agars.

1. The identity of the organism causing the patient's infection.
2. Risk factors for acquisition of the organism.
3. The characteristics of the microscopic morphology and growth patterns on laboratory media that help provide a presumptive identification

Answer 1

1. The organism that is causing the patient's infection is Neisseria meningitidis.

2. Neisseria meningitidis is spread through saliva and respiratory secretions during coughing, sneezing, kissing, chewing on toys and even through sharing fresh water. The risk factors are people with weak immunity, child care providers, pregnant women, people who live in close proximity to one another and adults over 55 years old.

3. A small amount of cerebrospinal fluid is required for analysis. It is a gram negative diplococci organism seen on a gram stain of a centrifugal sample of CSF. It takes around 1 to 2 hours to do the test. The organism is grown on a chocolate agar plate or on Thayer-Martin agar. Neisseria meningitidis ferments amd utilizes the glucose and maltose. The tests usually take 48-72 hours for growing the organism and a week more for serotyping.