BACTERIAL MENINGITIS Bacterial meningitis is a serious, life-threatening disease that causes inflammation of the membranes (meninges) and cerebrospinal fluid (CSF) of the nervous system. The meninges and the CSF encase and protect the brain and spinal cord. Bacterial meningitis is caused by an infection of bacteria. The most serious form of bacterial meningitis is called acute bacterial meningitis. ** Acute bacterial meningitis develops within hours or days and can be rapidly fatal or lead to serious, permanent complications if not recognized and treated immediately.
The meninges is the system of membranes which envelops the central nervous system. The meninges consist of three layers: <ul><li>Dura mater - thick, durable membrane, closest to the skull. </li></ul><ul><li>Arachnoid mater - thin, transparent membrane. Named because of its spider web-like appearance. It provides a cushioning effect for the central nervous system. </li></ul><ul><li>Pia mater - s a very delicate membrane. It is the meningeal envelope which firmly adheres to the surface of the brain and spinal cord. </li></ul>** subarachnoid space - is the space which normally exists between the arachnoid and the pia mater, which is filled with cerebrospinal fluid.
BACTERIAS THAT CAUSE MENINGITIS: 1. Neisseria meningitidis – are gram-negative, kidney bean–shaped organisms and frequently are found intracellularly. 2. Streptococcus pneumoniae - are lancet-shaped, gram-positive diplococci and are the leading cause of meningitis. 3. Haemophilus influenza type b – a pleomorphic gram-negative rod whose shape varies from a coccobacillary form to a long curved rod. **Today, Streptococcus pneumoniae and Neisseria meningitidis are the leading causes of bacterial meningitis. For bacterial meningitis, it is also important to know which type of bacteria is causing the meningitis because antibiotics can prevent some types from spreading and infecting other people. Before the 1990s, Haemophilus influenzae type b (Hib) was the leading cause of bacterial meningitis, but new vaccines being given to all children as part of their routine immunizations have reduced the occurrence of invasive disease due to H. influenzae.
PATHOPHYSIOLOGY Bacteria reach the subarachnoid space by a hematogenous route and may directly reach the meninges Once pathogens enter the subarachnoid space, an intense host inflammatory response is triggered by lipoteichoic acid and other bacterial cell wall products produced as a result of bacterial lysis Interleukin 1 (IL-1), tumor necrosis factor-alpha (TNF-a), and enhanced nitric oxide production play critical roles in triggering inflammatory response and ensuing neurologic damage. Infection and inflammatory response later affect penetrating cortical vessels, resulting in swelling and proliferation of the endothelial cells of arterioles. A similar process can involve the veins, causing mural thrombi and obstruction of flow. The result is an increase in intracellular sodium and intracellular water. The development of brain edema further compromises cerebral circulation, which can result in increased intracranial pressure and increased secretion of antidiuretic hormone resulting in the syndrome of inappropriate antidiuretic hormone secretion (SIADH) occurs in most patients with meningitis and causes further retention of free water. These factors contribute to the development of focal or generalized seizures. Severe brain edema also results in a caudal shift of midline structures with their entrapment in the tentorial notch or foramen magnum. If untreated, these changes result in decortication or decerebration and can progress rapidly to respiratory and cardiac arrest.
BACTERIA IL-1 TNF-a Enhanced Nitric oxide Inflammatory response Neurologic damage Subarachnoid space BACTERIAL LYSIS SWELLING **obstruction of normal flow BRAIN EDEMA Increase intracranial pressure! Increased secretion of antidiuretic hormone resulting in the syndrome of inappropriate antidiuretic hormone secretion (SIADH) THE BRAIN MENINGES WILL LATER BE INFLAMMED MENINGITIS
SIGNS AND SYMPTOMS OF DISEASE <ul><li>Fever </li></ul><ul><li>Tachycardia </li></ul><ul><li>Diaphoresis </li></ul><ul><li>Hypothermia </li></ul><ul><li>Rigors </li></ul><ul><li>Weakness </li></ul><ul><li>Photophobia </li></ul><ul><li>Seizures </li></ul><ul><li>Headache </li></ul><ul><li>Stiff neck </li></ul><ul><li>Aching muscles </li></ul><ul><li>Nausea </li></ul>The list of signs and symptoms mentioned in various sources for Bacterial meningitis includes the symptoms listed below: <ul><li>Vomiting </li></ul><ul><li>Lethargy </li></ul><ul><li>Irritability </li></ul><ul><li>Apnea </li></ul><ul><li>Apathy </li></ul><ul><li>Jaundice </li></ul><ul><li>Pallor </li></ul><ul><li>Shock </li></ul><ul><li>Hypotonia </li></ul><ul><li>Hypoglycemia </li></ul><ul><li>Convulsions </li></ul><ul><li>Anorexia </li></ul><ul><li>Coma </li></ul>
Kernig’s sign - usually performed with the patient supine with hips and knees in flexion. Extension of the knees is attempted: the inability to extend the patient’s knees beyond 135 degrees without causing pain constitutes a positive test for Kernig’s sign. Brudzinski signs - patient supine, then physician places one hand behind the patient’s head and places the other hand on the patient’s chest. The physician then raises the patient’s head (with the hand behind the head) while the hand on the chest restrains the patient and prevents the patient from rising. Flexion of the patient’s lower extremities (hips and knees) constitutes a positive sign.
Skin findings range from a nonspecific blanching, erythematous, maculopapular rash to a petechial or purpuric rash. **Approximately 6% of affected infants and children show signs of disseminated intravascular coagulopathy and endotoxic shock. These signs are indicative of a poor prognosis.
MODES OF TRANSMISSION The bacteria that cause bacterial meningitis are carried by humans in the nose and throat and are spread into the air by coughing and/or sneezing. Once these bacteria are airborne, they can be picked up by anyone who breathes them into their respiratory tract. The pathogens then spread from the respiratory tract to the blood stream and to the nervous system and cause bacterial meningitis .
SEROLOGICAL DIAGNOSIS A complete blood count (CBC) is also performed is measure the numbers of different types of blood cells, including white blood cells (WBCs). Different types of WBCs increase in number in characteristic ways during an infectious process, such as bacterial meningitis. <ul><li>Latex agglutination - The clumping of cells such as bacteria or red blood cells in the presence </li></ul><ul><li>of an antibody. The antibody or other molecule binds multiple particles and joins them, creating </li></ul><ul><li>a large complex. </li></ul>Specimen: CSF, blood, urine culture <ul><li>Serotyping - is a group of microorganisms classified together based on their cell surface antigens includes virulence, lipopolysaccharides (LPS) in Gram-negative bacteria, presence of an exotoxin or other characteristics which differentiate two members of the same species. </li></ul>
<ul><li>Limulus amebocyte lysate </li></ul><ul><li>(LAL) is an aqueous extract of blood cells (amoebocytes) from the horseshoe crab, Limulus polyphemus . LAL reacts with bacterial endotoxin or lipopolysaccharide (LPS), which is a membrane component of “Gram negative bacteria”. This reaction is the basis of the LAL test , which is used for the detection and quantification of bacterial endotoxins. </li></ul><ul><li>There are three basic LAL test methodologies: </li></ul><ul><li>gel-clot </li></ul><ul><li>turbidimetric </li></ul><ul><li>chromogenic </li></ul><ul><li>**The primary application for LAL is the testing of parenteral pharmaceuticals and medical devices that contact blood or cerebrospinal fluid. </li></ul><ul><li>Lumbar puncture - The CSF sample is examined for presence and types of white blood cells, red blood cells, protein content and glucose level. [ </li></ul>
TREATMENT AND PREVENTION “ Treatment of bacterial meningitis includes hospitalization, generally in an intensive care setting.” Prevention of the spread of bacterial meningitis also includes frequent hand washing and covering the mouth and nose with a tissue when sneezing or coughing . <ul><li>As soon as meningococcal infection is suspected, treatment begins with: </li></ul><ul><ul><li>High doses of aqueous penicillin G </li></ul></ul><ul><ul><li>Ampicillin, or cephalosporins such as ceftriaxone </li></ul></ul><ul><ul><li>Therapy may also include mannitol for cerebral edema </li></ul></ul><ul><ul><li>I.V. heparin for DIC </li></ul></ul><ul><ul><li>Dopamine for shock </li></ul></ul><ul><ul><li>Digoxin and a diuretic if heart failure develops </li></ul></ul><ul><ul><li>Supportive measures include fluid and electrolyte maintenance, ventilation (maintenance of a patent airway and oxygen, if necessary), insertion of an arterial or central venous pressure (CVP) line to monitor cardiovascular status, and bed rest </li></ul></ul>