NEISSERIAE MENINGITIDIS

Dr. Uzma Mussarat

LEARNING OBJECTIVES

Enlist the bacterial causes of meningitis Describe the morphological features,virulence

factors and diagnosis of following bacteria Neisseria meningitides Listeria monocytogenes Haemophilus influenzae Streptococcus agalactae streptococcus pneumonia

Meningitis

Meningitis means inflammation but usually implies serious infection of the meninges

Microorganism reach the meninges either by direct extension from the ears, nasopharynx, cranial injury or congenital meningeal defect, or by bloodstream spread.

Non infectious causes of inflammation include malignant cells, drugs and blood following subarachnoid hemorrhage

Meningococcal Meningitis

Is inflammation of the meninges- meningitis, caused by the bacteria Nesseria meningitidis.

Neisseria meningitidis,Streptococcus pneumoniae and Haemophilus influenzae are the most common agents of bacterial meningitis.

Meningococcal Meningitis

Less common bacterial causes of Meningitis, such as Staphylococci, enteric bacteria, group B streptococci and Listeria, occur in sub-populations like the immunocompromised, neonates, or head trauma patients.

Patients with Meningococcal Meningitis present with sudden onset of fever, intense headache, nausea, vomiting, stiff neck and, frequently, a petechial rash with pink macules or, very rarely, vesicles. Delirium and coma often appear.

Case fatality rate is between 5% and 15%.

Pathology

In acute bacterial meningitis, the pia arachnoid is congested with polymorphs. A layer of pus forms. This may organize to form adhesions, causing cranial nerve palsies and hydrocephalus.

In chronic infection (e.g. TB), the brain is covered in a viscous grey green exudates with numerous meningeal tubercles. Adhesions are invariable. Cerebral edema occurs in any bacterial meningitis.

In viral meningitis there is a predominantly lymphocytic inflammatory CSF reaction without pus formation, polymorphs or adhesions, there is little or no cerebral edema unless encephalitis develops.

Neisseria meningitides

General Characteristics of Neisseria spp.

Aerobic Gram-negative cocci often arranged in pairs

(diplococci) with adjacent sides flattened (like coffe beans)

Oxidase positive Most catalase positive Nonmotile Acid from oxidation of carbohydrates, not

from fermentation

Neisseria gonorrhoeaeNeisseria meningitidis

Important Human Pathogens

Other species normally colonize mucosal surfaces of oropharynx and

nasopharynx and occasionally anogenital mucosal membranes

Neisseria Associated Diseases

(ophthalmia neonatorum)

Encapsulated small, gram-negative diplococci

Second most common cause (behind S. pneumoniae) of community-acquired meningitis in previously healthy adults; swift progression from good health to life-threatening disease

Introductionof Neisseria meningitidis

Meningococcal meningitis

Humans only natural hosts Person-to-person transmission by

aerosolization of respiratory tract secretions in crowded conditions

Close contact with infectious person (e.g., family members, day care centers, military barracks, prisons, and other institutional settings)

Epidemiology of Meningococcal Disease

Highest incidence in children younger than 5 years and particularly those younger than 1 year of age as passive maternal antibody declines and as infants immune system maturesCommonly colonize nasopharynx of healthy individuals; highest oral and nasopharyngeal carriage rates in school-age children, young adults and lower socioeconomic groups

Occurrence Infections can occur through the year, but are more

common in late winter to early spring.

Mode of Transmission By direct contact- respiratory droplets from nose and

throat of infected people. Infection usually causes subclinical infection, severe

systemic infection is rare. Carrier prevalence can be as high as 25%.

Pathogenicity:

Pili-mediated, receptor-specific colonization of nonciliated cells of nasopharynx

Antiphagocytic polysaccharide capsule allows systemic spread in absence of specific immunity

Toxic effects mediated by hyperproduction of lipooligosaccharide

Serogroups A, B, C, Y, W135 account for about 90% of all infections

Specific receptors (GD1 ganglioside) for bacterial fimbriae on nonciliated columnar epithelial cells in nasopharynx of host

Organisms are internalized into phagocytic vacuoles, avoid intracellular killing in absence of humoral immunity and complement system (patients with late complement deficiencies are particularly at risk)

Replicate intracellularly and migrate to subepithelial space where excess membrane fragments are released

Pathogenesis of Meningococcal Disease

Hyperproduction of endotoxin (lipid A of LOS) and blebbing into surrounding environment (e.g., subepithelial spaces, bloodstream) mediates most clinical manifestations including diffuse vascular damage (e.g., endothelial damage, vasculitis (inflammation of vessel walls), thrombosis (clotting), disseminated intravascular coagulation (DIC)

Following dissemination of virulent organisms from the nasopharynx: Meningitis Septicemia (meningococcemia) with or

without meningitis Meningoencephalitis Pneumonia Arthritis Urethritis

Diseases Associated with Neisseria meningitidis

Meningitis Clinical findings

Clinically: rapid deterioration of flu like illness

Headache, neck stiffness, +ve kerning’s sign, fever,

Diagnosis: CSF + blood cultureCSF: WBC , RBCsGram stain: bacteria & cells

Neisseria meningitidis in Cerebrospinal Fluid

Skin Lesions of Meningococcemia

NOTE: Petechiae have coalesced into hemorrhagic bullae.

Neck rigidity

Haemorrhagic rash

Large numbers (e.g., >107cells/ml) of encapsulated, small, gram-negative diplococci (flattened along adjoining side) and polymorphonuclear leukocytes (PMN’s) can be seen microscopically in cerebrospinal fluid (CSF)

Laboratory Characterization of Neisseria meningitidis

Contd…

Transparent, non-pigmented nonhemolytic colonies on chocolate blood agar with enhanced growth in moist atmosphere with 5% CO2

Oxidase-positiveAcid production from glucose and

maltose but not from other sugars

Diagnosis Isolation of the organism

from CSF or blood.

2. Streptococcus pneumoniae (G+,Lancet shaped diplococci Alpha- haemolytic colonies on blood agar Quelling Test +ive Optochin –sensitive Bile solubility test +ive (bile soluble) Capsular polysaccharide Antigen detection

from CSF by Latex agglutination method

Streptococcus pneumoniae

General characteristics Inhabits the nasopharyngeal areas of healthy

individuals Possess C substance

Virulence factors Polysaccharide capsule

Clinical infections pneumonia meningitis bacteremia sinusitis/otitis media

The quellung reaction (swelling reaction) forms the basis of serotyping and relies On the swelling of the capsule upon binding of homologous antibody. The test consists of mixing a loopful of colony with equal quantity of specific antiserum and then examining microscopicallyfor capsular swelling

Contd…

Pneumoccus grow only in enriched media. (blood agar, glucose broth)

aerobes, facultative anaerobes optimal temperature – 37C (25-42C) optimal pH – 7.8 (6.5-8.3) increased growth in 5-10% CO2

Laboratory Diagnosis:Streptococcus pneumoniae

Colony morphology Smooth,

glistening, wet-looking, mucoid

a-Hemolytic CO2enhances

growth

Laboratory Diagnosis: Streptococcus pneumoniae

Identification Catalase

negative Optochin-

susceptibility-test–susceptible

Bile-solubility-test–positive

Alpha & Beta Haemolysis

S. pneumoniae

Pus cells and S. pneumoniae in sputum gram stain

Neutrophil & Red Cells

3. Haemophilus influenzae

Aerobic , Small, pleomorphic gram-negative coccobacilli Polysaccharide capsule Six different serotypes (a-f) of polysaccharide capsule(based on

the antigenicity of capsular polysacchrides)

Contd… 95% of invasive disease caused

by type b The type b capsule is composed of polyribitol phosphates Unencapsulated and untypeable strains can cause sinusitis and otitis media

but are usually noninvasive Growth in culture requires heme (X factor) and/or nicotinamide adenine

dinucleotide (NAD) (V factor) for adequate energy production

H.INFLUENZAE IS THE LEADING CAUSE OF MENINGITIS IN YOUNG CHILDREN

Important cause of URTI(otitis media,sinusitis and epiglottitis) and sepsis in children

It causes pneumonia in adults particularly in those having COPD (chronic obstructive pulmonary disease)

LABORATORY DIAGNOSIS

Specimens: Oral swab: avoid contamination with oral secretions Sputum from LRT Direct needle aspiration Cerebrospinal fluid (CSF) and blood (>107 bacteria/ml)

Microscopy: both sensitive & specific; G(-) bacilli in CSF in >80% cases before antibiotics treatment

LABORATORY DIAGNOSIS Heated blood (chocolate) agar for isolation(to inactivate nonspecific inhibitors of

H.influenzae growth) Growth require heme (x factor) and nicotinamide adenine dinucleotide, NAD (v

factor)

Contd..

Definitive identification can be made by biochemical tests or the capsular swelling “QUELLUNG “reaction

Fluorescent-antibody staining of the organism and counterimmunoelectrophoresis or latex agglutination tests detect the capsular polysacchride.

Streptococcus agalactiae

Streptococcus agalactiae

Gram +ive cocci in small chains Beta haemolytic colonies on blood agar Lance-field gouping ---group B (specific antiserum) Hippurate Hydrolysis test +ive CAMP – TEST +ive (Chtist,Atkin,Mouch,Peterson) Bacitracin Disk ----Negative

FIG. 6. CAMP-positive Streptococcus agalactiae (group B) inoculated at right angles to the test organism Staphylococcus aureus. Note the arrow-shaped zones of enhanced hemolysis.  

FIG. 7. CAMP-negative Streptococcus pyogenes (group A) inoculated at right angles to the test organism Staphylococcus aureus. Note the absence of arrow-shaped zones of enhanced hemolysis.)

Listeria Monocytogenes

Gram +ive , motile rod. Coccobacillus , Non –capsulated

Motile at 18 – 20 C°, non motile at 37 C° Tumbling/ Rotating motility Grows at Refrigerating temp 2-8 C°also Can cross placenta Causes meningitis in new born and pregnant women

Listeria Monocytogenes

Laboratory Diagnosis

Gram staining----G+ive rods Small grey coloured colonies

with narrow zone of beta hemolysis on blood agar

Motile nature differentiate it from corynaebacteria

THANKS