Microorganisms Test 2 Flashcards Preview

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Flashcards in Microorganisms Test 2 Deck (16):

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



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.



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.



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



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.


Rabies Virus

The virus proliferates in the brain, leading to fever, excitation, dilation of the pupils, excessive salivation, and anxiety. A fear of swallowing develops due to throat spasms. Death by respiratory failure.

Diagnosis: history and tissue sampling from possible vector.

Treatment: Rabies immune globulin injection at site and IM. Also immunization. No treatment once in CNS.

Mechanism of pathogenesis: bite --> replication in muscle --> travel through PNS into CNS --> affect brain and spinal cord.