Microorganisms Test 2 Flashcards
Listeria monocytogenes
Gram positive bacillus, intracellular pathogen, in environment
Risk group: Immunosuppressed, pregnancy, old ,newborns
Consumption of contaminated food - unpasteurized milk, cheese, and deli meats
Mechanism of disease: Internalin induces phagocytosis by epithelial cells of the GI track, and phospholipase and listeriolysin O allow to escape from vacuole
Treatment: Ampicillin and Gentamicin (synergistic effect of Ampicillin improving Gentamicin’s entrance into the cell)
Enterovirus/piconrnavirus: coxsackie, ECHO viruses, polio
Seasons: summer and fall
picornavirus: pico = small + RNA = picorna
transmitted oral fecal or respiratory
Capsid symmetry: icosahedral
Neisseria meningitidis
Gram negative diplococcus
13 serogroups -vaccine covers 4 types; New serogroup B vaccine as well.
Virulence factors include pili, IgA protease, capsule, adn endotoxin
Outbreaks in late winter or early sping
Risk group: teens, dorms
Transmission: respiratory droplets
LOS leads to thrombocytopenia, which is associated with disseminate intravascular coagulation (DIC) leading to hemorrhagic skin rash.
Treatment: Vaccine; Definitive and prophylactic treatment with ceftriaxone
Streptococcus pneumonia
Gram positive diplococci, lancet shape
Transmitted through respiratory droplet
Meningitis is secondary to paranasal sinusitis and otitis media
Most common cause of meningitis in individuals > 2 months old
Heptavalent protein-conjugate vaccine
Hemophilus influenze type b
Gram negative rod
Virulence factors include pili, outer membrane proteins, IgA protease and endotoxin
Infection can be following by hearing loss
Prevention wit hHib vaccine
TORCH Infections (Perinatal)
Mild maternal morbidity, but have serious fatal consequences.
Meningitis: Group B strep, E. coli, Listeria
TORCH, which includes Toxoplasmosis, Other (syphilis, varicella-zoster, parvovirus B19, Rubella, Cytomegalovirus, and HSV- 2
Group B streptococcus aka strep agalactaiae
GI and GU tract flora
Vertical transmission to infant: in utero or during vaginal delivery
Adult disease in immunocompromised
Sepsis, pneumonia, and meningitis
Twice as common in African American infants
Screen pregnant women (25% carriers) and treat with penicillin G
Bacitracin resistant, catalase negative, CAMP reaction (synergistice hemolysis of rbc’s by phospholipase of GBS and B-hemolysin of S. aureus)
Escherichia coli K1 strains
Gram negative, rod
Enteric organism, bacteremia, and transcellular permeation of BBB
K1 capsular polysaccharide prevents fusion with lysosome
Treatment with ceftriaxone and carbapenem
Chronic meningitis
Gradual onset over a period of weeks.
Spirochetes - Treponema pallidum, syphillis leptosira, and borrelia burgdoreferi, TB, fungi
Risk group - immunocompromised individuals especially with HIV/AIDS
TB Meningitis
25% of active TB have meningeal involvement
Gradual onset
Where incidence of TB is high mostly 0-4 year olds affected; where low incidence, mostly adults affected
Treat with RIPE(S): Rifampin, Isoniazid, pyrazinamide, and ethambutol
HSV 1 & 2
Large enveloped dsDNA virus.
Encode several proteins that are required to promote viral DNA replication (incuding biral DNA dependent DNA pol.) –> These proteins are the major targets of current antiviral chemotherapy vs. herpes virus infx.
Can cause lytic, persistent, latent (in neurons!), and in some cases, immortalizing infections
Profile: DNA virus –> Icosahedral Nucleocapsid –> Enveloped –> DS DNA linear genome (class I) –> Herpes viridae –> simplex virus –> HSV I and HSV 2
Account for 50% of all encephalitis cases where a cause is determined. HSV-1 is predominant. HSV-2 is more common in aseptic meningitis and neonatal HSV infx
Temporal lobe on MRI
Site of latentcy: Trigeminal ganglia
VZV
Profile: DNA virus –> Icosahedral Nucleocapsid –> Enveloped –> DS DNA linear genome (class I) –> Herpes viridae –> VZV
VZV is most common cause of encephalitis in immunocompromised pts. expeically w/ HIV.
Second most common viral cause of sporadic encephalitis and can occur w/ shingles or chickenpox.
Measles
Profile: ss RNA (-) virus –> Nonsegmented –> Helical Nucleocapsid –> Enveloped –> Paramyxoviridae –> Morbillivirus –> Measles Virus
Disease Mechanism: Repiratory –> lymph –> primary viremia –> blood –> multiple organs –> secondary viremia –> rash (acute) and rarely encephalitis (subacute) and subacute sclerosing panencephalitis (years later)
Incubation: 10-14 days
High R0 –> type A disease = incubation > latency
Immunocompetent - usually fine; certain genetic polymorphisms are at higher risk.
Picornaviruses
Profile: ssRNA (+) group IV –> nonsegmented –> Icosahedral nucleocapsid –> Noneveloped–> Picornaviridae –> Enterovirus –> Poliovirus, Coxaskievirus A & B, ECHO virus, and Enterovirus
Mechanism of disease: Oropharynx and intestine –> Lymph –> Blood (viremia) –> Skin, muscle, brain, meninges
Arboviruses
arthropod vectors. Several families can cause encephalitis.
West nile virus and La Crosse encephalitis virus (LCEV) highlighted.
Most infections are asymptomatic. Presentation of symptoms takes 2 to 15 days post infx. Flu-like illness. Vomiting and hemorrhagic fever can also occur. Infx can rarely spread to CNS.
