Case Presentation

The patient was a 31-month-old girl admitted to the hospital because of fever, headache, drowsiness, and vomiting. She had been previously well until 12 hours before admission, when she developed a runny nose, malaise, and loss of appetite.

Her birth and development were normal.There was no history of head trauma. Her routine immunizations had been neglected.

On examination, her temperature was 40°C (104° F), her neck was stiff, and she did not respond to verbal commands.

Her white blood count was elevated and showed a marked increase in the percentage of polymorphonuclear neutrophils (PMNs). Her blood sugar was in the normal range.

A spinal tap was performed, yielding cloudy cerebrospinal fluid under increased pressure.The fluid contained 18,000 white blood cells per microliter (normally, there are few or none), a markedly elevated protein, and a markedly low glucose. Gram stain of the fluid showed many tiny Gram-negative coccobacilli, most of which were outside the white blood cells.

1. What is the diagnosis and what is the causative agent?

2. What is the prognosis in this case?

3. What age group is most susceptible to this illness?

4. Compare the pathogenesis of this disease in children and adults.

Discussion

1. The patient had bacterial meningitis caused by Haemophilus Influenzae, serotype b.The fact that she had been healthy prior to her illness makes it highly unlikely that other serotypes could be responsible.

2. With treatment, the fatality rate is approximately 5%. Formerly, ampicillin was effective in most cases, but beginning in 1974, an increasing number of strains possessed a plasmid coding for ^-lactamase. So far, however, these strains have been susceptible to the newer cephalosporin-type antibiotics. Unfortunately, about one-third of those who are treated and recover from the infection are left with permanent damage to the nervous system, such as deafness or paralysis of facial nerves. Prompt diagnosis and correct choice of antibacterial treatment minimize the chance of permanent damage.

3. The peak incidence of this disease is in the age range of 6 to 18 months, corresponding to the time when protective levels of transplacental antibody are lacking and acquired active immunity has not yet developed.

Since 1987, vaccines consisting of type b capsular antigen conjugated with a protein such as the outer membrane protein of Neisseria meningitidis or diphtheria toxin have been used to immunize infants and thus eliminate the immunity gap. As a result, meningitis caused by H. influenzae type b is now rare. It is important to know, however, that strains other than type b can sometimes cause meningitis. So far, such strains are uncommon, although they represent an increasing percentage as type b strains decline in importance.

Haemophilus influenzae type b strains are referred to as "invasive" strains because they establish infection of the upper respiratory tract, pass the epithelium, and enter the lymphatic vessels and bloodstream. In this way, they gain access to the general circulation and are carried to the central nervous system. Most strains of H. influenzae, unlike type b, are non-invasive; although they can cause infections of respiratory epithelium, they usually do not enter the circulation. Most adults are immune to type b strains, but some adults develop meningitis from non-invasive H. influenzae strains that gain access to the nervous system because of a skull fracture or by direct extension to the meninges from an infected sinus or middle ear.

■ Those who are pregnant or have underlying diseases are advised to avoid soft cheeses such as Brie, Camembert, and Mexican style, and to avoid or reheat cold cuts, hot dogs, and refrigerated leftovers before eating.

So far, most strains of L. monocytogenes have remained susceptible to antibacterial medications such as penicillin. Even though the disease is often mild in pregnant women, prompt diagnosis and treatment is important to protect the fetus.

Some of the main features of listeriosis are presented in table 26.2.

Hansen's Disease (Leprosy)

Although Hansen's disease, also known as leprosy, is now a relatively minor problem in the Western world, it was once common in Europe and America. Like tuberculosis, the disease began to recede for unknown reasons even before an effective treatment was discovered. Today, it is chiefly a problem in tropical and economically underdeveloped countries, with an estimated worldwide occurrence of about 600,000 active cases, mostly concentrated in India, Nepal, Myanmar, Madagascar, Mozambique, and Brazil. In recent years, reported new cases in the United States have averaged about 150 per year, mostly acquired outside the country. The World Health Organization aims to eradicate the disease by the year 2005.

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