Microorganisms Test 2 Flashcards

1
Q

Listeria monocytogenes

A

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)

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2
Q

Enterovirus/piconrnavirus: coxsackie, ECHO viruses, polio

A

Seasons: summer and fall

picornavirus: pico = small + RNA = picorna

transmitted oral fecal or respiratory

Capsid symmetry: icosahedral

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3
Q

Neisseria meningitidis

A

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

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4
Q

Streptococcus pneumonia

A

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

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5
Q

Hemophilus influenze type b

A

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

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6
Q

TORCH Infections (Perinatal)

A

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

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7
Q

Group B streptococcus aka strep agalactaiae

A

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)

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8
Q

Escherichia coli K1 strains

A

Gram negative, rod

Enteric organism, bacteremia, and transcellular permeation of BBB

K1 capsular polysaccharide prevents fusion with lysosome

Treatment with ceftriaxone and carbapenem

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9
Q

Chronic meningitis

A

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

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10
Q

TB Meningitis

A

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

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11
Q

HSV 1 & 2

A

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

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12
Q

VZV

A

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.

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13
Q

Measles

A

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.

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14
Q

Picornaviruses

A

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

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15
Q

Arboviruses

A

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.

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16
Q

Rabies Virus

A

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.