Microbiology Exam 4 Flashcards
This spirochete is contracted by direct contact with a painless, small round, and firm infectious lesion (chancre). The onset of symptoms ranges from 10-90 days and without treatment this spirochete could cause secondary sx ( widespread rash) and tertiary sx ( multi-organ).
- Treponema pallidum
Syphilis
- Treponema pallidum
Which spirochete causes Lyme Disease (target sign) from prolonged association with deer tick bite exposure (24+ hrs)?
- Borrelia burgdorferi
What could cause a red macule, expanding rash, and neurologic or cardiac involvement (encephalitis, facial palsy, etc)?
- Borrelia burgdorferi
Lyme disease
Deer ticks may cause what disease?
- Lyme Disease from Borrelia burgdorferi
What spirochete transmits through contact with the urine of infected animals via contaminated water or moist soil? Causing fever, headache, myalgia, and chills leading to renal and liver failure.
- Leptospira interrogans
Leptospirosis
What causes leptospirosis?
- Leptospira interrgoans
GNB BTA that causes Melioidosis, especially persons with a pre-existing major illness.
- Burkholderia pseudomallei (B. pseudomallei)
Endemic in Southeast Asia, N. Australia, & South Pacific.
Transmitted by direct contact with contaminated soil and surface water causing acute pulmonary infection; acute localized infection (ulcer/nodule/abscess), septicemia, multiple organ involvement. Symptoms often appear 2-4 weeks after exposure or maybe subclinical and/or delayed (years). What etiologic agent is described?
- Burkholderia pseudomallei (B. pseudomallei)
Which BTA is endemic to parts of Africa, Asia, Middle East, & S. America (eradicated from N. America & Europe). Transmitted from animals to humans (rare) via contact with blood and body fluids into skin abrasions or mucosal surfaces (not environmental sources)
• Affects lungs & airways; causes septicemia, cutaneous lesions, liver, spleen, fever
• Fatality rate 95% in untreated; 50% in treated
- Burkholderia mallei (B. mallei)
What infrequent pathogen causes pneumonia in immunocompromised or cystic fibrosis patients?
- Burkholderia cepacia
Transmission through Soil & water source – very hardy; challenging hospital control
Which very-low-frequency etiologic agent is a GPC in chains that causes generalized necrotizing soft tissue infections, including Pelvic Inflammatory Disease; bone & joint, and other infections?
- Peptostreptococcus
Anaerobic bacteria that is normal microbiota of the vagina, GI, and skin?
- Peptostreptococcus
GPC, chains
Name the etiologic agent.
- Very low frequency
- Gram-negative bacilli
- Anaerobic
- Periodontal infections, skin ulcers
- Fusobacterium
Lower levels of this etiologic agent in the gut may be associated with clinical disorders?
- Facalilbacterium
Which etiologic agent is an abundant normal microbiota of gut, vagina, mouth and an important component of probiotics?
- Bifidobacterium
Gram-positive bacilli, often branched, non-sporeforming
Anaerobic
Name the etiologic agent described.
- Gram-positive bacillus, non-sporeforming
- Anaerobic
- An abundant normal gut microbiota; may boost immune system.
- Facalilbacterium
Which virus is transmitted by droplets and contact (especially hands) and by inhalation of droplets, causing cough, runny nose, generalized aches & muscle pain, fever (possible nausea & vomiting in children probably due to fever)?
- Incubation 1-2 days; symptoms 5-7 days (cough 7-14 days)
- Viral Pneumonia (about 10% of admissions) – high mortality
- Secondary Bacterial Pneumonia sometimes follows viral URT infections
- Influenza virus
Which virus structure is described below?
Core with 8 strands of RNA, Enveloped
- Lipid bilayer from previous host cell (animal specific or adapted to other types of cells)
- Contains Hemagglutinin and Neuraminidase – used for attachment and virulence
- Matrix protein (capsid)
Antigenic Types Include (A, B, C)
- Types based on surface antigens Hemagglutinin (H) and Neuraminidase (N)
- Animal strain based on original “source” of viral envelope
- Infectivity of animal virus to humans is due to adaptation to enter human cell membranes
- Influenza virus
Virulence factors of this virus include:
- High rate of gene recombination and mutation – New major antigenic types & subtypes sweep the world every 2-4 years
- Surface antigen changes due to:
(a) Gene recombination – recombination of 8 strands of RNA
(b) Gene mutation – causes genetic shift and drift - Hemagglutinin and Neuraminidase are factors both of attachment and cause some symptoms
- Virulence Factors
(a) Animal-specific envelope (e.g. human strains infect humans; avian strains infects avians; swine strains)
(b) Surface antigen changes (e.g. Avian Influenza (H5N1)
(c) Adaptation of virus envelope to enter & replicate in human cell - Antiviral medications available – start treatment within 48 hours to be effective
- Vaccine
(1) Made with the most common 3 antigens
(2) Required annually to match antigenic strains moving toward USA (World Health Org., CDC, and DoD labs track location and movement of strains around the world)
- Influenza virus
Which virus is the primary cause of the common cold and the most prevalent? How is this virus transmitted and is an RNA or DNA virus?
- Rhinovirus
- RNA
- Transmitted by inhalation of droplets and by contact (hands, eyes)
Developing vaccines is challenging.
What are the antigenically stable influenza virus types?
- Types B & C
What are the influenza virus antigenic Type A human subtypes?
- H1N1 (swine type adapted to human)
- H3N2
- H5N1, H7N9 (avian subtypes adapted to humans, considered dangerous)
Name the etiologic agent that is the second most common agent of colds and second most prevalent? It causes SARs and MERS-CoV. Transmitted by inhalation of droplets and by contact (hands & eyes).
- Corona virus
Developing vaccines is challenging.
What is SARs?
- SARS (Severe Acute Respiratory Syndrome) (several thousand cases, about 30% mortality)
What is MERS-CoV?
- MERS-CoV (Middle East Respiratory Syndrome – Corona Virus) – severe acute respiratory illness (fever, cough, shortness of breath), several hundred persons ill & about 30% mortality since 2012 (mostly Jordan, Saudia Arabia); camels are likely source
What virus is aka Human Orthopneumovirus, - the primary agent in infants & young children?
- Respiratory syncytial virus (RSV)
Which virus antigenic groups A and B are capable of causing severe infections, immunoglobulins are not necessarily protective against future infections, and developing a vaccine for this virus is very challenging?
- Respiratory syncytial virus (RSV)
How is RSV transmitted?
- Transmitted by droplets and contact (especially hands and eyes) and by inhalation of droplets
What is croup?
- Croup refers to an infection of the upper airway, which obstructs breathing and causes a characteristic barking cough. The cough and other signs and symptoms of croup are the result of swelling around the voice box (larynx), windpipe (trachea) and bronchial tubes (bronchi).
Which virus causes croup, bronchitis, cold-like symptoms; especially frequent in children? Is this virus enveloped and RNA or DNA?
- Parainfluenza virus
- Enveloped RNA virus - member of Paramyxovirus family; 4 antigenic types
This spirochete is contracted by direct contact with a painless, small round, and firm infectious lesion (chancre). The onset of symptoms ranges from 10-90 days and without treatment this spirochete could cause secondary sx ( widespread rash) and tertiary sx ( multi-organ).
- Human Metapneumovirus (hMPV)
What type of adenovirus causes Atypical pneumonia?
-Type 37
What types of adenovirus cause acute respiratory disease in military recruits?
- Types 4, 7
Which non-enveloped DNA virus is the agent of 5% to 10% of all viral infections (50% of infections before age 5)?
- Adenovirus
Causes:
- acute respiratory disease in military recurits (types 4, 7)
- Conjunctivitis
- Atypical pneumonia (type 37)
- Cold-like disease
- Gastrointestinal disease
- Croup/Bronchitis, sore throat, cystitis
Vaccine available againest types 4 and 7
The CMI holds this virus in check, it causes Types 1 & 2 Fever blisters, cold sores, gingivostomatitis, keratoconjunctivitis (neonates, contact lens wearer), genital lesions, meningitis (neonate). The primary lesion is more severe than subsequent, viruses hide (go latent) in nerve ganglia serving the region of the primary lesion.
- Herpes simplex (HSV), DNA, Enveloped
No adequate vaccine
What virus causes chickenpox and shingles (latent/recurring), hides in the nerve ganglia, and is held in check by CMI?
- Herpes zoster (HZV)
Vaccines available (chickenpox & shingles)
Which DNA enveloped virus is acquired via respiratory tract causing vesicle type skin lesions, moderately large, relatively few, mostly on the trunk of the body?
- Chickenpox: Herpes zoster (HZV)
Vaccines available (chickenpox & shingles)
What occurs when HZV remerges from hiding in the nerve ganglia, causing numerous, small, closely- spaced vesicles in the area served by the infected nerve ganglion? Virus outbreak subsides after few-to several weeks but may recur periodically.
- Shingles
Vaccines available (chickenpox & shingles)
Name the virus that is transmitted by oral secretions, infects the B-cell, and causes infectious mononucleosis in adolescents and adults.
- Epstien-Barr virus (EBV)
Virus may be eliminated by Cell Mediated Immunity or go into latency
What are the symptoms of mononucleosis?
- Fever, sore throat, enlarged lymph nodes, fatigue, swelling of liver or spleen
What viruses cause mononucleosis?
- EBV (adolescents and adults)
- CMV (children)
Baby is infected from vaginal microbiota during birthing, occasionally causes CMV mononucleosis with microcephaly, jaundice, multiple organ involvement. Impairment of the central nervous system is associated with the development of mental/physical retardation. Rarely causes obvious illness.
- Cytomegalovirus, CMV (children)
Latent virus infection in immunosuppressed / immunocompromised organ transplant, malignancy, AIDS
(a) Febrile mononucleosis
(b) Multiple organ involvement (pneumonitis, hepatitis, GI ulcerations, encephalopathy)
(c) Severity of disease related to competency of cell-mediated immunity
- Cytomegalovirus
What virus causes epidemic diarrhea in infants and young children? Transmitted feal to oral transmission and there is a vaccine for it.
- Rotavirus, RNA
Which RNA non-enveloped virus causes 90% of epidemic and sporatic viral gastroenteritis? After 18-48 hours of incubation, it causes vomiting, diarrhea, cramps, and low-grade fever. The illness lasts 12-60 hours and often remits spontaneously. Transmitted by food, water, vomitus – very difficult to prevent the spread.
- Norwalk virus
Describe the structure of the Human Immunodeficiency Virus.
General characteristics (Retrovirus group) (1) Medium sized, enveloped RNA virus (2) Structure and composition (a) Envelope • Glycoprotein-41 (GP-41) • Glycoprotein-120 (GP-120) • Antigenically variable (b) Capsid: Protein-24 (P-24) (c) Core • Two strands of RNA • Reverse transcriptase -- an enzyme which produces a DNA copy of the genomic RNA (this is an extremely unusual approach) (3) Two antigenic types: HIV-1 present worldwide and HIV-2 primarily found in Western Africa. (Antigenic variations within each type.)
Describe the interactions between HIV and Cells.
(1) GP-120 attaches to the CD4 marker on the cell membrane [can infect cells that do not have CD4 markers if they co-infect with another Retrovirus]. GP-41 attaches to a different protein, CXCR4.
(2) The RNA strands enter the host cell
(3) * Reverse transcriptase uses the RNA strands as a template to produce new viral DNA
(4) * The new viral DNA is incorporated into the host cell’s DNA – remains latent for prolonged period of time
* Unusual characteristic
(5) Alters the ability of CD4 cell to produce cytokines
(6) New virions released from infected cells by budding - ultimately kills CD4 cell
d. Types of cells infected (primary): CD4 Helper T-cells; Monocytes – macrophages
How is HIV transmitted?
Transmission of the virus (primarily inside infected cells) [HIV virions have been isolated in all body secretions.]
(1) Intimate sexual contact
(2) Blood and blood products (e.g. transfusion, I.V. drug use, needle sticks, cuts)
(3) Perinatally – from mother to baby
Where are the hot spots of infection for HIV?
- Southern Africa, Southern and Southeastern Asia
Describe stage one of the HIV infection.
(1) Stage I – Primary HIV infection – lasts about 1 to 4 months
(a) Viruses are replicated and shed at a moderate rate for a short time
• p24 antigen (capsid) may be detectable for about 2-6 weeks after infection
• Antibodies to p24
(b) Symptoms:
• “Mononucleosis-like” or “flu-like” illness. Fever, night sweats, malaise, rash, and muscle and joint pain. Lymphadenopathy may develop.
• Becomes asymptomatic after 1 to 3 weeks
Describe the second stage of HIV infection.
(2) Stage II – Latent (asymptomatic) period
(a) Patients are asymptomatic – usually lasts few to several years
(b) Viruses are replicated and shed at a low rate
(c) HIV antibodies are detectable
(d) Pathologic characteristics – Gradual decrease in CD4 cells occurs
Describe stage three of the HIV infection.
Stage III – Persistent Generalized Lymphadenopathy or AIDS Related Complex (ARC)
(a) Virus replication and shedding occurs at a high rate – p24 antigen becomes elevated again; Antibody to p24 diminishes
(b) Pathologic characteristics – Gradual reduction of the CD4 cell count.
(c) Symptoms
• Persistent generalized lymphadenopathy (PGL) – Lymph nodes remain swollen for months with no other signs of infection. Night sweats, weight loss, diarrhea.
• Kaposi’s sarcoma
• Opportunistic infections - develop when CD4 cells are less than about 300/ mm3. Oral yeast infections, Recurrent shingles, Bacterial skin infections
Describe stage four of the HIV infection.
(4) Stage IV – AIDS [Acquired Immune Deficiency Syndrome] (symptomatic period)
(a) Pathology
• Significant decrease of CD4 cells (<200/mm3); moderate decrease of CD8 cells
• Antigen to p24 reappears – virus replication overwhelms antibody production
• Antibodies to HIV are ineffective
• Host is gradually unable to mount cell mediated or humoral immunity
(b) Opportunistic infections – become more severe as CD4 count decreases
• Tuberculosis
• Pneumocystis carinii (protozoan) – pneumonia
• Fungal infections: Histoplasmosis, Coccidioidomycosis, Cryptococcal meningitis
• Toxoplasmosis gondii (protozoan) – brain
• Herpes simplex virus, types 1 and 2
• Cryptosporidium – intestinal
• Cytomegalovirus – retina, esophagus, colon
• Mycobacterium avium complex – disseminated
(c) Central Nervous System involvement – Dementia
What virus causes infection of the liver, anorexia, hepatic tenderness, jaundice, and dark urine?
- Hepatitis
Are hepatitis viruses taxonomically related to each other?
- No
Which DNA enveloped virus has the surface antigen HBsAg and what are the antigens in its core?
- Hepatitis B
- HBcAg (core antigen)
- HBeAg ( associated with high infectivity)
What is the earliest marker of acute infection of Hepatitis B?
- HBsAg surface antigen
Persistence over 6 months implies chronic disease (failure to seroconvert to anti-HBs)
How is Hepatitis B transmitted?
(2) Epidemiology & Transmission
(a) Transmission - parenteral route most predominant mode. Contact with blood or blood products, usually via contaminated needles or syringes.
(b) High risk groups
• Intravenous drug users; male homosexuals
• Patients with multiple transfusions; Hemophiliacs; Dialysis
(c) Incubation period
• Usually 45 to 180 days
• Replicates in liver
An immune response that is characterized by a conversion from the absence of a specific antibody to the presence of that specific antibody.
- Seroconversion
When would you see this immunological marker HBeAg (core-associated “e” antigen)?
- Early indicator of acute infection, active virus replication, and most infectious period
- Persistence beyond 10 weeks indicative of progression to chronic carrier state and probable chronic liver damage
When would you see this immunological marker Anti-HBe (antibody to Hepatitis B “e” antigen of the core)?
- Seroconversion from HBeAg to anti-HBe usually occurs during late acute phase - suggests resolution of infection and lowering of transmissibility
- Chronic/carriers fail to seroconvert during acute phase