Microbiology Case Study: An 88 Year Old Male with Headache

Case History

An 88 year old male presents with fever, nausea, and headache. The patient reported a diffuse headache accompanied by malaise, fatigue, and nausea without vomiting. He denied confusion, irritability, or a personal and family history of headaches. According to the patient, he frequently attends cookout parties and enjoys fruits, salads, wine, and cheese. Temperature is 38.2 degrees Celsius, blood pressure is 96/65 mmHg, pulse is 102 beats/minute, and respiratory rate is 20 breaths per minute. Physical exam is negative for nuchal rigidity and Kernig sign. Funduscopic exam is negative for papilledema. CBC shows leukocyte count of 16,000/mm3. The patient’s blood culture is positive.

Laboratory Identification

Image 1. Short gram positive bacilli identified on Gram stain of blood culture (100x oil immersion).
Image 2. Aerobic growth of round and translucent colonies with a narrow zone of beta hemolysis subcultured from positive blood culture bottle to sheep blood agar plate.

The blood culture was positive for short, gram positive bacilli. Sheep blood agar plate grew round and translucent colonies which have a narrow zone of beta hemolysis as shown on our plate. The organism was catalase positive and motile at 25 degrees Celsius. It showed end over end tumbling motility in a wet prep and an umbrella pattern in semi-solid motility medium. It was identified by MALDI-ToF as Listeria monocytogenes.


Listeria monocytogenes is a gram positive bacillus that is isolated from the environment and a variety of animals. It is associated with foodborne outbreaks from dairy and meat products. The most common foods associated with listeriosis outbreaks include unpasteurized raw milk, cold deli meat, hot dogs, raw sprouts, smoked seafood, and soft cheese.1

Listeria commonly infects pregnant women, immunocompromised individuals, and elderly 65 years or older.1 Among pregnant women, Listeria can lead to miscarriages, stillbirths, and newborn meningitis resulting in death.1 In 1985, an outbreak of Listeria due to soft cheese resulted in 142 individuals sick, 10 newborn deaths, 18 adult deaths, and 20 miscarriages.1 Among the immunocompromised and elderly, Listeria can cause septicemia and meningitis. In 2011, a cantaloupe outbreak due to Listeria resulted in 147 people sick in 28 states and 33 deaths.1 The infected population was mostly over the age of 65 years.1 In addition, Listeria can cause acute febrile gastroenteritis in healthy individuals.2 Patients typically present with fever, watery diarrhea, nausea, headache, and pain in joints and muscles.2 Symptoms start 24 hours after the ingestion of bacteria and resolve by themselves in 2 days.2

Treatment of Listeria depends on the severity of symptoms. Although pregnant women with Listeria infection typically present with a self-limited flu-like illness, they are treated with IV ampicillin to prevent infection of the fetus.1 For patients other than pregnant women, the treatment of Listeria infection depends on the severity of symptoms.


  1. Information for Health Professionals and Laboratories. (2017, June 29). Retrieved on March 1st, 2018 from https://www.cdc.gov/listeria/technical.html
  2. Say Tat Ooi, Bennett Lorber; Gastroenteritis Due to Listeria monocytogenesClinical Infectious Diseases, Volume 40, Issue 9, 1 May 2005, Pages 1327 1332, https://doi.org/10.1086/429324


-Ting Chen, MD is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

One thought on “Microbiology Case Study: An 88 Year Old Male with Headache”

  1. I just love these case reviews. When you do not work in certain areas of the lab, you often lose your skill in those areas. These cases simply re-connects you to those areas and make you appreciate science and great lab testing.

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