Central Nervous System Infections

RABIES

Tetanus

Trismus

Meningitis

Bacterial Viral

Predisposing factors Most cases of meningitis occur when

colonization by potential pathogens is followed by mucosal invasion of the nasopharynx

However, some patients develop disease by direct extension of bacteria across a skull fracture in the area of the cribriform plate

Other patients develop meningitis following systemic bacteremia as with endocarditis or a urinary tract infection or pneumonia

Some Other predisposing conditions include complement deficiency, corticosteroid excess, and HIV infection

CLINICAL FEATURES The overwhelming majority of patients with

bacterial meningitis have fever and headache Most patients have high fevers, but a small

percentage have hypothermia

CNS symptoms Some patients will have significant

photophobia and/or clouding of the sensorium

Changes in level of consciousness, seizures tend to appear later in the course of disease

Treatment and prevention of bacterial meningitis

Suspected bacterial meningitis is a medical emergency and immediate diagnostic steps must be taken to establish the specific cause

The mortality rate of untreated bacterial meningitis approaches 100 percent and, even with optimal therapy, there is a high failure rate

Empiric treatment should be begun as soon as the diagnosis is suspected using bactericidal agent(s) that achieve significant levels in the CSF

Use of bactericidal agents

Bactericidal therapy is generally necessary to cure meningitis

Chloramphenicol is a bacteriostatic drug for most enteric Gram negative rods; however, it is usually bactericidal for H. influenzae, N. meningitidis, and S. pneumoniae and has been extensively and successfully used to treat meningitis caused by these organisms

More severe but less frequent than viral Used to have a high rate of infection caused

by Haemophilus influenzae type b. However the wide use of protein-polysaccharide conjugated vaccines has dramatically reduced the incidence of this infection

In children Neisseria. meningitidis is the most common cause, followed by Streptococcus pneumoniae

In adults up to age 60, S. pneumoniae is most common followed by N. meningitidis

Over age 60, most cases are due to S. pneumoniae

Bacterial Meningitis

Meningococcal Meningitis Severe acute bacterial infection Neisseria meningitidis Aerobic gram-negative bacteria Serogroups based on characteristics of

the polysaccharide capsuleRelative importance of serogroupsdepends on geographic location and other factors (e.g. age)

Meningococcal DiseasePathogenesis Organism colonizes nasopharynx - pili In some persons organism invades

bloodstream and meninges Transmission- Respiratory droplets