Risk factor

Prevalent pathogens

Crowded residences (school or college dormitories, military barracks)

Neisseria meningitidis, viruses (enteroviruses, measles, mumps)

Public beaches and swimming pools

Enteroviruses

Age >60 years

Streptococcus pneumoniae and Listeria monocytogenes

Sinusitis, acute or chronic purulent otitis media, mastoiditis

S pneumoniae, Hib

Alcohol abuse

S pneumoniae, L monocytogenes, Mycobacterium tuberculosis

Impaired cell-mediated immune response (HIV and AIDS, immunosuppressive therapy—particularly after transplant—or glucocorticoid treatment, cancer treatment), diabetes, hemodialysis, liver cirrhosis, cachexia in end-stage cancer or other diseases

L monocytogenes, M tuberculosis, fungi

Fractures of the skull base or ethmoidal cells involving the anterior cranial fossa and tears of the dura mater resulting in CSF leakage

S pneumoniae, Hib, group A beta-hemolytic streptococci

Penetrating head injuries

Staphylococcus aureus, Staphylococcus epidermidis, aerobic gram-negative bacilli including Pseudomonas aeruginosa

Neurosurgical procedures

Klebsiella pneumoniae, other Enterobacteriaceae, P aeruginosa, Acinetobacter baumannii, S aureus, S epidermidis (hospital-acquired meningitis)

CSF shunts

S epidermidis, S aureus, P aeruginosa, other aerobic gram-negative bacilli, Propionibacterium acnes, fungi

Complement deficiencies

N meningitidis (frequently familial or recurrent meningitis), Moraxella spp, Acinetobacter spp

Neutropenia <1×109/L

P aeruginosa, other gram-negative bacilli

Impaired humoral immune response

S pneumoniae, Hib, less commonly N meningitidis

Asplenia

S pneumoniae, Hib, N meningitidis

Cranial or vertebral osteomyelitis

S aureus, gram-negative bacilli

Sarcoidosis

M tuberculosis

Burns, severe illness, invasive ICU procedures (intubation, tracheostomy, vascular access procedures, parenteral nutrition), prosthetic heart valves or other prostheses, treatment with broad-spectrum antibiotics

Fungi