Meningitis (Neisseria)

Causative Organism: Neisseria meningitidis (gram-negative diplococci)

Mode of Transmission: Droplet contact

Virulence Factors: Capsule, endotoxin and IgA protease

Culture/Diagnosis: Gram stain/culture of CSF, blood, rapid antigenic tests, oxidase test, and PCR

Prevention: Conjugated vaccine; ciprofloxacin, rifampin, or ceftriaxone used to protect contacts

Treatment: Ceftriaxone, penicillin

Meningitis (Streptococcus)

Causative Organism: Streptococcus pneumoniae (small, gram-positive, flattened coccus)

Mode of Transmission: Droplet contact

Virulence Factors: Capsule, induction of apoptosis, hemolysin, and hydrogen peroxide production

Culture/Diagnosis: Gram stain/culture of CSF

Prevention: Two vaccines: Prevnar
(children and adults) and Pneumovax (adults)

Treatment: Vancomycin + ceftriaxone or
cefotaxime; resistant S. pneumoniae is categorized by the CDC as a Serious Threat

Meningitis (Haemophilus)

Causative Organism: Haemophilus influenzae (gram-negative coccobacillus)

Mode of Transmission: Droplet contact

Virulence Factors: Capsule

Culture/Diagnosis: Culture on chocolate agar

Prevention: Hib vaccine, ciprofloxacin, rifampin, or ceftriaxone

Treatment: ceftriaxone

Meningitis (Listeria)

Causative Organism: Listeria moncytogenes (gram-positive from coccobacilli to long filaments)

Mode of Transmission: Vehicle (food)

Virulence Factors: Intracellular growth

Culture/Diagnosis: cold enrichment, rapid methods

Prevention: cooking food, avoiding unpasteurized dairy products

Treatment: Ampicillin + gentamicin

Meningitis (Cryptococcus)

Causative Organism: Cryptococcus neoformans (yeast)

Mode of Transmission: Vehicle (air, dust)

Virulence Factors: Capsule, melanin production

Culture/Diagnosis: Negative staining, biochemical tests, DNA probes, cryptococcal antigen test

Prevention: N/A

Treatment: Amphotericin B and flucytosine, followed by fluconazole

Meningitis (Coccidioides)

Causative Organism: Coccidioides

Mode of Transmission: Vehicle (air, dust, and soil)

Virulence Factors: Granuloma (spherule) formation

Culture/Diagnosis: dentification of spherules, cultivation on Sabouraud’s agar

Prevention: Avoiding airborne endospores

Treatment: Fluconazole or amphotericin B

Meningitis (viruses)

Causative Organism: viruses

Mode of Transmission: Droplet contact

Virulence Factors: Lytic infection of host cells

Culture/Diagnosis: Initially, absence of bacteria/fungi/protozoa, followed by viral culture or antigen tests

Prevention: N/A

Treatment: Usually none (unless specific virus identified and specific antiviral exists)

Neonatal and Infant Meningitis (Streptococcus)

Causative Organism: Streptococcus agalactiae

Mode of Transmission: vertical (during birth)

Virulence Factors: Capsule

Culture/Diagnosis: Culture mother’s genital tract on blood agar; CSF culture of neonate

Prevention: Culture and treatment of mother

Treatment: Penicillin G plus aminoglycosides

Neonatal and Infant Meningitis ( E. coli, K1)

Causative Organism: Escherichia coli, strain K1 B G-

Mode of Transmission: Vertical (during birth)

Virulence Factors: N/A

Culture/Diagnosis: CSF Gram stain/culture

Prevention: N/A

Treatment: Ceftazidime or cefepime ± gentamicin

Neonatal and Infant Meningitis (Listeria)

Causative Organism: Listeria monoctogenes

Mode of Transmission: Vertical

Virulence Factors: Intracellular growth

Culture/Diagnosis: Cold enrichment, rapid methods

Prevention: Cooking food, avoiding unpasteurized dairy
products

Treatment: Ampicillin, trimethoprim-sulfamethoxazole

Neonatal and Infant Meningitis (Cronobacter)

Causative Organism: Cronobacter sakazakii

Mode of Transmission: Vehicle (baby formula)

Virulence Factors: Ability to survive dry conditions

Culture/Diagnosis:

Prevention: Chromogenic differential agar or rapid detection
kits

Treatment: Safe preparation and use of, or avoidance of,
powdered formula

Primary Amoebic Meningoencephalitis

Causative Organism: Naegleria fowleri

Mode of Transmission: Vehicle (exposure while swimming in water)

Virulence Factors: Invasiveness

Culture/Diagnosis: Examination of CSF; brain imaging,
biopsy

Prevention: Limit warm freshwater or untreated tap water entering nasal passages

Treatment: Pentamidine, sulfadiazine

Granulomatous Amoebic Meningoencephalitis

Causative Organism: Acanthamoeba

Mode of Transmission: Direct contact

Virulence Factors: Invasiveness

Culture/Diagnosis: Examination of CSF; brain imaging, biopsy

Prevention: N/A

Treatment: Surgical excision of granulomas; pentamidine

Acute Encephalitis Disease (Arboviruses)

Causative Organisms: Arboviruses (West Nile virus, La Crosse virus, Jamestown Canyon virus, St. Louis
encephalitis virus, Powassan virus, Eastern equine encephalitis virus)

Mode of Transmission: Vector (arthropod bites)

Virulence Factors: Attachment, fusion, invasion capabilities

Culture/Diagnosis: History, rapid serological tests, nucleic
acid amplification tests

Prevention: Insect control

Treatment: none

Acute Encephalitis Disease (Herpes Simplex)

Causative Organism: Herpes simplex 1 or 2

Mode of Transmission: Vertical or reactivation of latent
infection

Virulence Factors: N/A

Culture/Diagnosis: Clinical presentation, PCR, Ab tests,
growth of virus in cell culture

Prevention: Maternal screening for HSV

Treatment: Acyclovir

Acute Encephalitis Disease (JC virus)

Causative Organism: JC virus

Mode of Transmission: Ubiquitous

Virulence Factors: N/A

Culture/Diagnosis: PCR of cerebrospinal fluid

Prevention: None

Treatment: No drugs proven effective; mefloquine and others have been used

Acute Encephalitis Disease (Postinfection)

Causative Organism: Postinfection encephalitis

Mode of Transmission: Sequelae of measles, other viral infections, and, occasionally, vaccination

Virulence Factors: N/A

Culture/Diagnosis: History of viral infection or vaccination

Prevention: N/A

Treatment: Steroids, anti-inflammatory agents

Subacute Encephalitis Disease (Toxoplasma)

Causative Organism: Toxoplasma gondii

Mode of Transmission: Vehicle (meat) or fecal–oral

Virulence Factors: Intracellular growth

Culture/Diagnosis: Serological detection of IgM, culture, histology

Prevention: Personal hygiene, food hygiene

Treatment: Pyrimethamine and/or leucovorin and/or sulfadiazine

Subacute Encephalitis Disease (sclerosing)

Causative Organism: Subacute sclerosing
panencephalitis

Mode of Transmission: Persistence of measles virus

Virulence Factors: Cell fusion, evasion of immune system

Culture/Diagnosis: EEGs, MRI, serology (Ab versus measles virus)

Prevention: None

Treatment: None

Subacute Encephalitis Disease (Prions)

Causative Organism: Prions

Mode of Transmission: CJD = direct/parenteral contact with infected tissue, or inherited vCJD = vehicle (meat, parenteral)

Virulence Factors: Avoidance of host immune response

Culture/Diagnosis: Biopsy, image of brain

Prevention: Avoiding infected meat or instruments; no prevention for inherited form

Treatment: None

Zika Virus Infection

Causative Organism: Zika virus

Mode of Transmission: Vertical, vector-borne, sexual contact;
likely through blood transfusions (not yet confirmed)

Virulence Factors: Protein that reduces innate immune
response

Culture/Diagnosis: PCR testing

Prevention: Avoiding mosquitoes; no vaccine yet

Treatment: Supportive

Rabies Disease

Causative Organism: Rabies virus

Mode of Transmission: Parenteral (bite trauma), droplet contact

Virulence Factors: Envelope glycoprotein

Culture/Diagnosis: Direct fluorescent antibody test (DFA)

Prevention: Inactivated vaccine

Treatment: Postexposure passive and active immunization; induced coma and ventilator support if symptoms have begun

Poliomyelitis Disease

Causative Organism: Poliovirus

Mode of Transmission: Fecal-oral, vehicle

Virulence Factors: Attachment mechanisms

Culture/Diagnosis: Viral culture, serology

Prevention: Live attenuated (developing world); inactivated
vaccine (developed world)

Treatment: None, palliative, supportive

Tetanus Disease

Causative Organism: Clostridium tentani

Mode of Transmission: Parenteral, direct contact

Virulence Factors: Tetanospasm exotoxin

Culture/Diagnosis: Symptomatic

Prevention: Tetanus toxoid immunization

Treatment: Combination of passive antitoxin and tetanus
toxoid active immunization, metronidazole, and muscle relaxants; sedation

Botulism Disease

Causative Organism: Clostridium botulinum

Mode of Transmission: Vehicle (foodborne toxin, airborne organism), direct contact (wound), and parenteral (injection)

Virulence Factors: Botulinum exotoxin

Culture/Diagnosis: Culture of organism; demonstration of toxin

Prevention: Food hygiene; toxoid immunization available for
laboratory professionals

Treatment: Antitoxin, penicillin G for wound botulism, and
supportive care

African Sleeping Sickness Disease

Causative Organism: T rypanosoma brucei subspecies gambiense or rhodesiense

Mode of Transmission: Vector, vertical

Virulence Factors: Immune evasion by antigen shifting

Culture/Diagnosis: Microscopic examination of blood, CSF

Prevention: Vector control

Treatment: Suramin or pentamidine (early), eflornithine or
melarsoprol (late)