Question

A 3 12 year old male presented to an outside emergency room with a fever and lethargy since the previous evening and a petechial rash first noted on the day of evaluation. On physical examination the patient was listless and had a temperature of 39°C, blood pressure of 104/52 mmHg, and heart rate of 148 beats/min. Examination of the skin revealed a petechial rash as well as two purpuric lesions. Blood cultures were obtained, and he was given intravenous antibiotics and transferred to this hospital. On arrival here, he underwent a lumbar puncture, which was notable for cerebrospinal fluid with 190 white blood cells/mm3, with 94% neutrophils, consistent with bacterial meningitis. No organisms were seen on Gram stain of the cerebrospinal fluid. Blood cultures from the outside hospital were subsequently positive for an oxidase- positive, gram-negative diplococcus. 1) Which bacterium was causing this patient's illness? 2) Is this organism ever part of the normal oropharyngeal flora? Explain your answer. 3) Which immunologic abnormalities predispose individuals to infection with this organism? 4) What are purpuric lesions and a petechial rash, and which virulence factor plays a central role responsible for their appearance?

Answer 1

1.Neisseria meningitidis The Meningococcal bacteria in particular are the most common cause of the meningitis rash. These bacteria can be very common and are mostly harmless, but in some people this bacteria invade the body via the back of the nose and throat, causing severe illness and even death.

2.N. meningitidis is usually considered to be part of the normal oropharyngeal flora and can be found in a significant minority (2 to 10%) of healthy people. During epi- demics of meningococcaldisease in institutionalized populations such as new recruits to the military, colonization rates may increase

3.

Bacteria that enter the bloodstream and travel to the brain and spinal cord cause acute bacterial meningitis. But it can also occur when bacteria directly invade the meninges. This may be caused by an ear or sinus infection, a skull fracture, or, rarely, after some surgeries.

Several strains of bacteria can cause acute bacterial meningitis, most commonly:

• Streptococcus pneumoniae (pneumococcus). This bacterium is the most common cause of bacterial meningitis in infants, young children and adults in the United States. It more commonly causes pneumonia or ear or sinus infections. A vaccine can help prevent this infection.
• Neisseria meningitidis (meningococcus).This bacterium is another leading cause of bacterial meningitis. These bacteria commonly cause an upper respiratory infection but can cause meningococcal meningitis when they enter the bloodstream. This is a highly contagious infection that affects mainly teenagers and young adults. It may cause local epidemics in college dormitories, boarding schools and military bases. A vaccine can help prevent infection.
• Haemophilus influenzae (haemophilus).Haemophilus influenzae type b (Hib) bacterium was once the leading cause of bacterial meningitis in children. But new Hib vaccines have greatly reduced the number of cases of this type of meningitis.
• Listeria monocytogenes (listeria). These bacteria can be found in unpasteurized cheeses, hot dogs and lunchmeats. Pregnant women, newborns, older adults and people with weakened immune systems are most susceptible. Listeria can cross the placental barrier, and infections in late pregnancy may be fatal to the baby.

4.Purpuric lesions will show extravasation of red blood cells into the dermis. Small vessels in the upper dermis may be filled with homogeneous, eosinophilic material

Petechial rash are pinpoint, round spots that appear on the skin as a result of bleeding. The bleeding causes the petechiae to appear red, brown or purple.