Meningitis: Bacterial vs. Viral

Case Study
D.F. is a 65-year-old male who has brain cancer. He is admitted to a private room in a community hospital for adjustment of anti-seizure medication and to receive chemotherapy. Within 48 hours of admission D.F. develops a rash and fever. Initially, the rash is considered a drug reaction to the anti-seizure medicine and the fever is considered a reaction to the chemotherapy. D.F. complains of a severe headache. An infectious disease physician evaluates him. The differential includes meningitis and tumor. A lumbar puncture is performed to obtain cerebrospinal fluid (CSF) for analysis. The CSF analysis shows elevated opening pressure, elevated protein, low glucose (hypoglycorrhachia), cloudy fluid and a positive Gram stain. Bacterial meningitis is the presumptive diagnosis. Broad-spectrum empiric antibiotic therapy is initiated.

Meningitis
Meningitis is an anxiety-provoking topic for many health care workers who often have common misperceptions about meningitis. These inaccuracies include that meningitis is always infectious; that the agents causing meningitis can be easily transmitted from person to person; that people diagnosed with meningitis are highly infectious; and that meningitis is always associated with severe complications (e.g., death). Nurses play an important role in providing accurate information to dispel these misperceptions and decrease fear and anxiety in patients, family, staff and the public.

Although some types of bacterial meningitis can be catastrophic, the reality is that meningitis is a complex group of diseases with varying severities and epidemiologies. The etiology of meningitis can be either infectious (bacteria or viral) or noninfectious (such as tumor, trauma, brain abscess, subdural empyema or pharmacologic reaction).

Since viral meningitis is often a self-limited disease, it is probably fair to assume that many cases of viral meningitis go undiagnosed and/or do not have a specific etiologic agent identified. The most common pathogens associated with meningitis are listed in Table 1.

A lumbar puncture is the usual procedure performed from which a diagnosis of bacterial vs. viral meningitis can be established. CSF obtained from the lumbar puncture is examined directly and cultured, and the results of these analyses are critical to diagnose either bacterial or viral meningitis. Table 2 summarizes the most common CSF findings associated with bacterial or viral meningitis. Severe complications can result from bacterial meningitis but are not very common from viral meningitis.

Bacterial Meningitis
Worldwide, bacterial meningitis is a common disease, with 75 percent-80 percent of all cases associated with three pathogens: Haemophilis influenzae, Neisseria meningitidis and Streptococcus pneumoniae. In the United States, as of the late 1990s-more than 10 years after licensure of the H. influenzae serotype b vaccine (Hib)-the most common agents are N. meningitidis and S. pneumoniae. During the early 1990s, approximately 25,000 cases occurred annually in the United States, with 70 percent identified among children age 5 or younger. Each year more than 2,000 deaths were attributed to bacterial meningitis.

The predominant organisms responsible for bacterial meningitis vary, depending on the age of the patient (see Table 3). Epidemics of bacterial meningitis do occur and are always associated with N. meningitidis.

Bacterial meningitis in adults is characterized by abrupt onset. Symptoms can include sudden fever, intense headache and meningismus. Signs of meningeal irritation associated with acute febrile illness or dehydration without actual infection of the meninges may be subtle or acute; may or may not be accompanied by Kernig's sign (inability to extend the leg fully when in a sitting position or when the thigh is flexed upon the abdomen), or Brudzinski's sign (flexion of the neck resulting in flexion of the hip and knee, or with passive flexion of the lower limb on one side a similar movement occurs on the opposite side). Other signs of cerebral dysfunction (confusion, delirium, declining level of consciousness) may be present. Constitution signs can include nausea, vomiting, rigors, myalgia, weakness and diaphoresis. Seizures occur in up to 40 percent of cases.

A petechial rash may develop in association with N. meningitidis meningitis. However, neonates with bacterial meningitis often do not manifest fever or meningismus-the clinical symptoms may be nonspecific (e.g., irritability, high-pitched crying, listlessness, refusal to feed). Elderly patients may have no fever and the main clinical symptoms may be lethargy/obtundation with variable signs of meningismus.

Bacterial meningitis is diagnosed by CSF examination. Typical findings are: elevated opening pressure, elevated protein and hypoglycorrhachia. The fluid appearance may be cloudy or turbid. The CSF leukocyte concentration is usually elevated with a neutrophilic pleocytosis. CSF Gram stain examination is associated with rapid and accurate organism identification in up to 90 percent of bacterial meningitis cases.

Emergent empirical broad spectrum antimicrobial therapy, based on age, underlying disease status and medical history, should be initiated as soon as a diagnosis of bacterial meningitis is likely even if no bacteria are visualized by Gram stain.

Upon identification of the bacterial pathogen, antimicrobial therapy can be modified based on susceptibility results. Therapy should be individualized and based on the patient's clinical response. Neurologic sequelae (e.g., hearing loss, seizures and behavioral problems) are associated in about 33 percent -50 percent of bacterial meningitis survivors.

Infection control recommendations for patients with bacterial meningitis-with two important exceptions-are the practice of Standard Precautions, with strict attention to meticulous hand washing. The two exceptions are bacterial meningitis due to either N. meningitidis (meningococcal) or H. influenzae.

Infection Control Precautions
For meningitis caused by either of these two organisms, additional infection control strategies are indicated since transmission can occur by the droplet/close contact route-for up to 24 hours even after starting effective antibiotic therapy.

The Centers for Disease Control and Prevention (CDC) recommends droplet precautions in addition to Standard Precautions for bacterial meningitis caused by either N. meningitidis or H. influenzae. Precautions may be discontinued 24 hours after initiation of effective therapy. When droplet precautions are initiated, the risk for transmission is much lower. The local health department should be notified to arrange for follow-up of household and community contacts.

Meningococcal Meningitis
Because of the potential for an adverse outcome, concern and anxiety are common whenever a meningococcal infection (N. meningitidis) is suspected or diagnosed. The incubation period from exposure to the disease can be 2-10 days, but usually is 3-4 days.

Transmission is by droplet/direct contact with respiratory secretions or contact with laboratory cultures. It is not by aerosols, and thus the risk for transmission from casual or brief contact with infected patients is minimal. In a health care setting, spread of the infection is uncommon.

Health care workers at risk for transmission are those with intense direct contact, e.g., mouth-to-mouth resuscitation, intubation or nasotracheal suctioning without the use of protective barriers, or lab personnel who handle cultures without protection. Only these staff will require chemoprophylaxis.

General exposure guidelines for household contacts and child care contacts are at least 4 hours close contact during the week before the illness onset or mouth-to mouth kissing.

Postexposure chemoprophylaxis can be either rifampin, ciprofloxacin or ceftriaxone. Ciprofloxacin should not be administered to children or pregnant women. Rifampin turns urine, saliva and tears an orange color. Also, it has been associated with nausea, vomiting and rash.

To promote adequate absorption, rifampin should be taken on an empty stomach. Lab staff who have been exposed percutaneously require penicillin prophylaxis. Immunization of health care staff after chemoprophylaxis for sporadic exposure is not indicated.

Vaccine for High-Risk Groups
Meningococcal vaccine, although not routinely recommended, should be given to certain risk groups over 2 years of age-e.g., asplenic people-and is used as a control measure during community and college outbreaks. Additional risk groups susceptible to serious meningococcal infections include persons with terminal complement deficiencies and laboratory personnel who are routinely exposed to N. meningitidis in solutions that may be aerosolized.

Administration of meningococcal vaccine is not indicated for hematopoietic stem cell transplant (HSCT) recipients, but administration of the vaccine should be evaluated for HSCT recipients who live in endemic areas or are experiencing outbreaks.

Bacterial meningitis can be very serious; children are usually hospitalized. Most types of bacterial meningitis will not be spread person-to-person; for the types that can be spread, good hygiene, especially handwashing and environmental cleanliness, are important preventative measures.

Immediate contact with the local health department is very important for the management of bacterial meningitis. Responsibilities of the health department include communicating with the patient's physician, making recommendations to prevent infection transmission and working with local health care workers and the community to reduce the risk for transmission.

In the school and child care setting, parents of exposed children should receive information about meningitis, recommendations for antibiotics and instructions about what to do if their child develops any symptoms of concern (such as fever, headache, rash) during the incubation period.

H. Ibfluenzae Meningitis
In health care settings, transmission of the bacteria H. influenzae from a patient with the infection is exceedingly rare. Because of widespread use of the Hib vaccine, people are usually not unduly anxious or concerned about this disease. Some people-such as those who live in the same household, attend the same day care or are members of the same classroom-may have more than brief or casual contact with the infected person.

General guidelines to identify persons who may have had more than brief or casual contact are those who were:

  • living with the infected person or had at least 4 hours of exposure to the infected person in the childcare setting or the classroom; or

  • attending the same child care as the infected person for 5-7 days before infection onset.

Rifampin is the agent of choice for chemoprophylaxis, but contraindications (e.g., pregnancy, liver disease, drug interactions) must be considered. Children who have H. influenzae should have their hearing tested after recovery.

Viral Meningitis
Viral meningitis (aseptic meningitis), although common in occurrence, is rarely life threatening. Viral meningitis is generally not a reportable disease (depending on whether a reportable etiologic agent-such as mumps-is identified). For this reason, the actual incidence of viral meningitis is not known. However, seasonal increases occur in late summer and early autumn and are mainly attributed to arbovirus and enterovirus activity.

Seasonal predilection occurs with lymphocytic choriomeningitis virus (fall and winter) and mumps (winter and spring). Identification of the viral agent is challenging-under ideal circumstances, serologic and virology isolation methodology may yield a specific etiologic agent identification for about half of the cases diagnosed.

Viral meningitis symptoms are similar to those for bacterial meningitis and include fever, headache (often described as being frontal or retro-orbital), photophobia, pain upon moving the eyes, meningismus and sometimes a vesicular/petechial rash (rubella-like if echoviruses and coxsackieviruses are causative).

Constitutional symptoms-e.g., malaise, myalgia, anorexia, nausea, abdominal pain, diarrhea-may accompany fever. Mild lethargy is common. Occurrence of stupor, marked confusion or coma is rare, and these symptoms generally are not indicative of a meningitis with a viral cause. Gastrointestinal and respiratory symptoms may occur when infection is caused by enteroviruses.

The CSF profile is abnormal in viral meningitis. Characteristics include usually normal opening pressure, slightly increased protein and normal glucose (glucose is below normal for bacterial meningitis). The CSF leukocyte concentration is elevated with lymphocytic pleocytosis (polymorphonuclear neutrophils may predominate during the first 48 hours of meningitis, especially in some enteroviral infections). Bacteria are absent on Gram stain.

Mainstay of Treatment
Antimicrobial therapy is not effective for most viral agents; symptomatic therapy is the mainstay for treatment of most cases of viral meningitis. Hospitalization generally is not required, with case-specific exceptions, e.g., patients with deficient humoral immunity. Duration of illness is generally 10 days or less. Sequelae to viral meningitis, lasting a year or more, may include weakness, muscle spasm, insomnia and personality changes; paralysis is unusual although transient paresis and encephalitic manifestations may occur. Recovery from viral meningitis is usually complete for adults. The prognosis for infants and neonates is not as good-learning disabilities, hearing loss and other neurologic sequelae have been reported.

Because agent identification is often not done, difficult to determine or not available until after recovery, infection control is an important consideration. Enteroviruses are transmitted by the fecal-oral route and are among the more common causes of viral meningitis. The CDC recommends contact isolation in addition to Standard Precautions for neonates and young children diagnosed with enterovirus infection, including enteroviral meningitis. The National Institutes of Health Clinical Center practices a more conservative approach for management of meningitis with unclear etiology: Contact isolation is practiced for the duration of the illness for each patient diagnosed with aseptic meningitis. If a nonenteroviral diagnosis is established, infection control guidelines are then modified per the specific infectious agent identified. Generally, investigation of contacts or a source of infection is not indicated.

Case Study
Pending identification of the bacteria, D.F. is placed on droplet precautions and responds quickly to broad-spectrum antibiotic therapy. Droplet precautions are discontinued after 24 hours of antibiotic therapy and Standard Precautions alone are resumed. Culture results are positive for L. monocytogenes, a bacteria that is not transmitted person-to-person and for which antibiotic prophylaxis of contacts is not indicated. D.F. continues a speedy recovery.

Barbara Fahey is a nurse consultant with the Hospital Epidemiology Service, Office of the Director, Clinical Center, National Institutes of Health, Bethesda, MD.

Table 1: Most Common Agents Associated With Meningitis
Escherichia coli** Neisseria meningitidis*
Group B streptococci Pseudomonas species**
Haemophilus influenzae* Streptococcus pneumoniae*
Listeria monocytogenes*
Adenovirus Echovirus
Herpes simplex Lymphocytic choriomeningitis virus
Arbovirus
    Measles
Enteroviruses (picornaviruses)
Mumps
Coxsackievirus Varicella-zoster
* Can be normal oral pharyngeal flora. Conditions such as sinusitis, otitis media, upper respiratory tract infection, lower respiratory tract infection and trauma to the ears, nose or sinuses may predispose to nasopharyngeal epithelial cell infection, which in turn may result in bacteremia (transient or persistent), which in turn may result in bacteria traversing the blood-brain barrier into the CSF.
** Can be normal gastrointestinal flora. Entry into the central nervous system facilitated by trauma, neurosurgical procedures, lumbar puncture and spinal anesthesia.
*** Entry to body occurs via oral, oral-fecal or respiratory route. Virus replicates and spreads to brain via bloodstream.


Table 2: Cerebrospinal Fluid Analysis Findings
Color Clear Cloudy Cloudy
Red blood cell count None None None
Gram stain Negative Usually Positive Usually Negative (60%-90%)
Pressure Less than 200 mm H2O Above normal Normal
Protein 15-45 mg/dL Above normal Above normal
Glucose 50-75 mg/dL Below normal Usually normal or below normal
Lymphocytic pleocytosis None Positive with neutrophilic pleocytosis Positive with lymphocytic pleocytosis


Table 3: Predominant Bacterial Pathogens Causing Meningitis by Age Group
Neonates Enteric bacteria
Gram-negative bacilli
Group B streptococci
Pseudomonas species
Listeria monocytogenes
Children
(> 1 month)
Haemophilis influenzae
Neisseria meningitidis
Adults

 bacilli*

Meningococci species
Pneumococci species
Aerobic gram-negative
* Not as common as meningococci and pneumococci but identified with increasing frequency, especially among the elderly.


Meningitis: Bacterial vs. Viral

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