Exam 4 Flashcards
1
Q
what are some LRT infections
A
- bronchitis
- histoplasmosis
- influenza*
- pneumonia
- tuberculosis
2
Q
what are some URT infections
A
- common cold
- diphtheria
- whooping cough
- strep throat
- ear infections
3
Q
how are respiratory pathogens transmitted from human to human
A
- via indirect contact with respiratory droplets (common)
- less than 3ft; are heavier and need to be in
close contact with someone to transfer
- less than 3ft; are heavier and need to be in
- via airborne droplet nuclei (rare)
- are lighter and can travel in the air for a
longer amount of time
- are lighter and can travel in the air for a
4
Q
true or false; some respiratory pathogens exist as part of the normal microbiota
A
true
5
Q
does influenza start in the URT or LRT
A
starts in the URT and then moves to LRT
6
Q
describe corynebacterium diphtheriae shape
A
- gram-positive rods
- often arranged side by side in “palisades”
- irregular staining
7
Q
how is corynebacterium diphtheriae transmitted
A
- humans are the only known reservoir
- transmitted via contact with respiratory droplets
8
Q
humans can have c. diphtheriae in their
A
oropharynx or on skin
9
Q
what population is most likely to get c. diphtheriae
A
unimmunized children
10
Q
describe diptherotoxin
A
- A-B exotoxin
- lysogenzied strains of C. diphtheriae causes Diphtheria
11
Q
what is the function of diptherotoxin
A
inhibits protein synthesis
12
Q
what are some signs/symptoms of diphtheria
A
- acute onset of sore throat
- pseudomembrane = dead cells, exudate, RBCs, and bacteria
- “bull neck” = enlarged cervical lymph nodes and edema in the neck
- fever
- systemic diphtheria = toxin gets into circulation (toxemia) and damages heart and kidneys
13
Q
if someone were to have a sore throat, enlarged cervical lymph nodes, fever, and pseudomembrane - what would be their diagnosis?
A
diphtheria
14
Q
would corynebacteria organisms be detected in the blood from a patient with systemic diphtheria?
A
no
- because the corynebacteria infect the URT, but the localized infection produces the toxin that would be systemic
15
Q
c. diphtheria requires these two treatments
A
- antibiotics to arrest the infection, but toxins already absorbed are unaffected
- diphtheria antitoxin to neutralize toxin circulation
16
Q
what vaccines work to prevent diphtheria, pertussis, and tetanus
A
DTaP and Tdap vaccines
- contains diphtheria toxoid = inactivated exotoxin
17
Q
what are some signs/symptoms of a common cold and how long do they last
A
- sneezing, sore throat, runny nose, cough
- nasal secretions initially watery, then thicken,
finally become cloudy and greenish
- nasal secretions initially watery, then thicken,
- symptoms mostly gone within 7-10 days
18
Q
what are some complications that can occur with a common cold
A
sinus congestion or earache
19
Q
what are some signs/symptoms of the flu and how long do they last
A
- high fever; lasts 3-4 days
- early and prominent extreme exhaustion
- chest pain and severe cough
20
Q
what are some complications that can occur with the flu
A
- bronchitis and pneumonia; can be life-threatening
21
Q
how many times do adults vs children get a common cold and what is the causative agent?
A
- adults get ~ 2-4 a year
- children get ~ 9 colds a year
- causative agent = children don’t have as much immunity
22
Q
what is the most common cause of the common cold
A
rhinovirus
23
Q
describe rhinovirus
A
- naked virus with an RNA genome
- replicate best between 33C - 35C -> infect cooler tissues of the nose
24
Q
what is the pathogenesis of common cold
A
- infects respiratory epithelial cells in the nasal mucosa
- inhibits the ciliary motion of infected cells; cells die
- damage leads to release of cytokines, inflammation
- nasal excess nasal secretions, congestions, sore throat, coughing, and sneezing
- fever is typically absent
25
how is rhinovirus transmitted
- direct contact = with hands contaminated with respiratory droplets
- indirect contact = respiratory droplets
- contaminated fomites (rhinoviruses are naked)
- only need a few virions to infect
26
describe bordetella pertussis
- tiny encapsulated gram-negative bacilli
- causes pertussis aka whooping cough
27
bordetella pertussis is the classic disease of
infants (<1 year)
- severe, life-threatening in babies
28
what is the epidemiology of bordetella pertussis
- human reservoir
- transmitted via contact with respiratory droplets
29
what is the pathogenesis of bordetella pertussis
- cells are inhaled, attach to ciliated cells of respiratory epithelium
- tracheal cytotoxin = toxic to ciliated epithelial cells -> disrupts mucociliary clearance
30
describe pertussis toxin (PTx)
- A-B exotoxin
- A subunit inactivates inhibitory regulatory G protein, causing increase in cAMP production
- increased cAMP yields increased mucus, decreased killing ability of phagocytes
31
what are the stages of pertussis disease
1. incubation = 7-10 days; no symptoms; rising bacterial culture
2. catarrhal = 1-2 weeks; rhinorrhea, malaise, fever, sneezing, anorexia; peak bacterial culture
3. paroxysmal = 2-4 weeks; repetitive cough with whoops, vomiting, leukocytosis; falling bacterial culture
4. convalescent = 3-4 weeks (or longer); diminished paroxysmal cough, development of secondary complications (pneumonia, seizures, encephalopathy); lowest point of bacterial culture
32
what is the treatment for pertussis
- primarily supportive
- antibiotics effective if treated early
33
what is the prevention of pertussis
- immunization with DTaP starting at two months
- subunits of B. pertussis are used in the vaccine
- requires boosters, Tdap
34
what does Tdap include
tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis
35
which type of vaccine do you think would result in longer lasting immunity?
- whole cell vaccine
- subunit (acellular) vaccine
whole cell vaccine
36
describe the symptoms of and how long the immunity for killed whole-cell vaccine, DTP
- fever, agitation, febrile seizures
- long term immunity
37
what are the symptoms and duration of immunity for acellular vaccines, DTaP
- fewer, milder side effects
- waning immunity
38
during which weeks should pregnant women get a dose of Tdap vaccine and why
- during the early part of gestational weeks 27 through 36
- helps mother from passing pertussis onto infant and provides passive immunity to infant
39
what is the route of infection of bacterial pneumonia
- the infection of the lungs elicits inflammation
- the alveoli fill with fluids and WBCs (consolidation)
- air exchange becomes impaired and patients experiences respiratory distress
40
describe klebsiella penumonia
- gram-negative rods
- large capsule is its major virulence factor
- produces big mucoid colony when cultured on agar
41
what are some symptoms of klebsiella pneumonia
lung necrosis and abscess formation resulting in bloody "currant jelly" sputum
42
klebsiella pneumonia is the leading cause of
hospital-acquired pneumonia
43
how is klebsiella pneumonia transmitted
- transmitted via contact with respiratory droplets or contaminated medical equipment (eg ventilators)
44
true or false - klebsiella penumoniae may be part of the microbiota in pharynx and GI tract, and do not typically cause respiratory disease in healthy individuals
true
45
what populations are at most risk for klebsiella pneumonia
- those with preexisting lung conditions
- patients with invasive medical devices
- alcoholics and diabetics
46
what is the treatment for klebsiella pneumonia
- carbapenem antibiotics (beta lactam antibiotic)
- though it is hard to treat klebsiella pneumonia because of its antibiotic resistance
47
new strains encoding klebsiella pneumonia have emerged carbapenemase (KPC) and they belong to a family of bacteria called
carbapenem-resistant enterobacteriaceae (CRE)
48
describe mycoplasmal pneumonia
small, easily deformed bacteria lacking cell wall (no peptidoglycan)
49
mycoplasmal pneumonia is the leading pneumonia of
college students, common among military recruits, and children 5-15 years of age
50
how is mycoplasmal penumonia transmitted
through contact with respiratory droplets
- not part of the microbiota
51
mycoplasmal penumonia use specialized attachment organelle to bind to
ciliated cells
- this causes epithelial cells to be damaged and ciliary motion is hindered
52
what are some signs/symptoms of mycoplasmal pneumonia
- generally mild "walking pneumonia" or "atypical pneumonia"
- onset is gradual
- initial symptoms are fever, headache, muscle pain, and fatigue
- dry persistent cough and sputum may be produced later
53
describe haemophilus influenzae penumonia
- gram-negative coccobacillus
- nonencapsulated strains, which cause pneumonia
- colonizes the nasopharynx in majority of healthy children
- elderly is the high risk group
54
how is haemophilus influenzae transmitted
- via contact with respiratory droplets
- infect alveoli -> inflammation -> exudate rich in neutrophils -> cough and shortness of breath
55
antibiotic resistance is a big challenge for treatment of
haemophilus influenzae
- no vaccine against the nonencapsulated strains
56
describe histoplasmosis (spelunker's disease)
- dimorphic fungus (ie mold and yeast forms)
- exists in soil contaminated with bat or bird droppings
57
how is histoplasma transmitted
- reservoir: birds and bats
- acquired through inhalation of mold spores from soil (often soil contaminated with bird and bat droppings)
- airborne transmission = the spores become airborne during cleanup or demolition projects
- non-communicable
58
what are some signs/symptoms of histoplasma
- headache, weakness, chest pain, and in severe cases -> extensive pulmonary infiltration and dissemination to other organs
59
what other diseases may occur from histoplasmosis
serious lung disease (TB-like illness) may occur in immunocompromised people or elderly or infants
60
what does antigenic drift mean
when envelope proteins continually mutate
- resulting from RNA replication errors
- RNA polymerase has low fidelity
- gradual
- occurs with influenza A, B, and C
61
what does antigenic shift mean
major changes caused by genetic reassortment
- coinfection with two viruses in same cells allow mixture of 8 RNA segments
- abrupt
- occurs with influenza A only
62
if someone has a low grade fever, runny nose, sneezing and cough but feels well enough to work or class, which disease do they most likely have?
- strep throat
- a cold
- flu
a cold
63
what are some symptoms of influenza "the flu"
fever, headache, muscle aches/pains, fatigue, sore throat and cough
64
how is influenza transmitted
- contact with respiratory droplets
- airborne via respiratory droplet nuclei
- contact with fomites contaminated with respiratory droplets
65
describe influenza virus
- enveloped
- (-) ss RNA genome
- segmented genoma
66
what is the pathogenesis of "flu"
- the virus attaches to and infects epithelial cells in the URT
- replicates inside the cells, damaging the cells (recovery of the mucociliary escalator may take weeks)
- spreads to LRT and sometimes secondary bacterial infections occur
67
what are influenza's glycoproteins "spikes"
- hemagglutinin (HA)
- neuraminidase (NA)
68
what is the function of hemagglutinin
- facilitates viral entry
- binds to sialic acid on host cells which act as receptors
69
what is the function of neuraminidase
- facilitates virion release from the cell by cleaving sialic acid
- degrades mucin layer of respiratory tract
70
why does influenza cause annual epidemics and periodic pandemics
viral evolution
71
flu pandemics are caused by the emergence of a virus that is "novel" which means there is a new
HA or NA subtype
72
HA and NA surface antigens change as influenza
replicates
73
which types of genetic change is primarily responsible for pandemics
- antigenic drift
- antigenic shift
- both are equally as likely to contribute to the emergence of a pandemic viral strain
antigenic shift
74
swine is susceptible to which two strains
avian and human influenza strain
75
true or false - influenza A can infect animals other than humans
true
76
in the 1918 pandemic influenza, were people with the strongest or weakest immune systems affected
strongest
77
what helped contain the 1918 flu pandemic
non-pharmaceutical interventions (NPI)
- isolation, quarantine
78
what is another name for avian H5N1 influenza
bird flu
79
is avian H5N1 influenza highly virulent in humans
yes
80
what are the three qualities that made 1918 influenza pandemic so severe
1. everyone was susceptible because it was a novel strain
2. spreads easily from person-to-person (airborne transmission)
3. virus was unusually virulent (mortality rate = ~10%)
81
evidence so far suggests that H7N9 and H5N1 influenza cannot be transmitted from
human to human
82
what is the treatment for influenza antivirals
- supportive treatment (rest and fluids)
- there are four FDA-approved antiviral drugs recommended by CDC to treat flu
- three of which are NA inhibitors
- needs to be given early
83
what is the prevention of the four influenza strains
flu vaccines
- takes about six months to produce a flu vaccine
- vaccines are protective if the vaccine strains are closely related to circulating strains
84
describe flu vaccines
- contain three or four different viruses (mix of A subtypes and a B strain)
- about 50-70% effective, new one required each year because of antigenic drift
85
what are the two types of flu vaccine
- inactivated vaccine (flu shot)
- live attenuated vaccine (nasal spray)
86
what are the inactivated influenza vaccine recommendations
- routine annual influenza vaccination is recommended for all persons aged >_ 6 months who do not have contraindications
- exceptions: egg allergies and pervious adverse reactions to vaccine
87
infected people who are asymptomatic or mildly symptomatic can transmit influenza virus to
persons at high risk for complications from influenza
88
what is a coronavirus
- large family of enveloped viruses
- ss RNA genome
- cause a range of illnesses from mild to severe
89
which types of diseases are caused by coronaviruses
- common cold
- SARS (severe acute respiratory syndrome)
- MERS (middle east respiratory syndrome)
90
how is coronavirus transmitted
- contact with respiratory droplets (most)
- airborne transmission via droplet nuclei (less common)
- fomites: contaminated with respiratory droplets
91
when are people most infectious with COVID-19
2-3 days before symptoms and first 7 days of illness
92
what populations are more at risk for COVID
- people older than 65
- people with underlying medical conditions
93
what is the structure of SARS CoV-2
- ss (+) RNA genome
- enveloped
94
why do S-proteins bind to ACE2
triggers either viral endocytosis or membrane fusion and viral entry
- contributes to high rate of infectivity
95
S protein is coated in ____ which disguise it from the immune system
glycans
96
if SARS CoV-2 is not blocked by the immune system what will happen
virions will migrate to the LRT where they infect type 2 pneumocyte cells that are rich in ACE2 proteins
- will eventually lead to apoptosis and death of alveolar cells
97
in critical cases, a "cytokine storm," an overreaction by the immune system, causes immune cells to cause damage to
healthy tissues
98
SARS CoV-2 once it infects the alveoli of the lung, may cause hypoxemia. What is hypoxemia?
- low hemoglobin in the blood
- loss of surfactant
- low oxygen in the blood
- septic shock
- elevated oxygen in the blood
low oxygen in the blood
99
what are the three stages of COVID-19
1. asymptomatic state
2. upper airway and conducting airway response
3. hypoxia, progression to acute respiratory distress syndrome (ARDS) within 8 to 12 days
100
what happens in stage 1 of COVID
- incubation time - average is 5 days, range 2 to 14 days
- virus shed by the host in droplets
- virus propagates, mild innate immune response initiated
101
what happens in stage 2 of COVID
- robust immune response
- clinical manifestations of disease appear on average 5 days post-exposure and include cough, fever, shortness of breath, sore throat, loss of taste and/or smell
- up to 80% of COVID-19 cases will either be asymptomatic or will arrest at this stage
102
what happens in stage 3 of COVID
- critical care/hospitalization necessary
- manifestations include pneumonia, etc
- oxygen levels fall (SpO2 < 94%) as lungs become filled with fluid, WBCs, mucus, and cellular debris
- leading cause of death is hypoxic respiratory failure complicated by ARDS
103
about four weeks after COVID-19 initial infection, symptoms may include
fatigue, joint pain, chest pain, anxiety, depression, worsened quality of life
104
multisystem inflammatory syndrome in children (MIS-C) with exposure to SARS-CoV-2 symptoms include
persistent fever, hypotension, rashes, multiorgan involvement (kidneys, heart, GI, vasculature, neurologic), and inflammation
105
describe RT-PCR test; what kind of test is it, what does it detect, lists advantages and disadvantages
- molecular test
- detects viral genetic material
- adv: accurate is sample is taken approximately 5 days post-exposure
- disadv: may not catch early infection, takes 24-48 hours for results
106
describe antigen rapid test; what kind of test is it, what does it detect, lists advantages and disadvantages
- immunological test
- detects viral protein antigens vs genetic material
- adv: results in ~15 minutes, good screening tool
- disadv: not as sensitive as PCR test -> can result in false negatives
107
what are the two diagnostic tests for COVID-19
- RT-PCR test
- antigen rapid test
108
which viral antigen is targeted by the SARS CoV-2 vaccines currently approved for use in the U.S.
- envelope protein
- spike glycoprotein
- nucleocapsid protein
- envelope lipid
- viral RNA
spike glycoprotein
109
what is the goal of COVID-19 vaccines
- to induce the production of antibodies that bind to the virus
- effectively blocking entry into the host cell so that S protein is the antigen used in most vaccine candidates
110
what are the four COVID-19 treatments
- remdesivir - anti-viral
- paxlovid - anti-viral
- bebtelovimab - anti-SARS CoV2 monoclonal antibodies
- dexamethasone - anti-inflammatory
111
describe remdesivir anti-viral treatment
- nucleosides analog that targets the RNA-dependent RNA-polymerase
- inhibit viral replication by terminating RNA transcription prematurely
- IV infusion at a healthcare facility for three days
112
describe paxlovid anti-viral treatment
- protease inhibitor of the SARS-CoV2 main protease enzyme
- used to treat mild-to-moderate COVID-19 and who are at high risk for progression to severe COVID-19
- taken at home by mouth (orally)
113
describe bebtelovimab anti-SARS CoV2 monoclonal antibodies treatment
- IgG antibody that binds the spike protein on SARS CoV2
- blocks attachment to human ACE2 receptor
- single IV injection
- FDA does not recommend use of convalescent plasma
114
describe dexamethasone anti-inflammatory treatment
- steroid
- relieves inflammation
- recommended only in hospitalized and severe cases if remdesivir cannot be obtained
115
mycobacterium tuberculosis is a chronic granulomatous disease of the lungs but can spread to
extrapulmonary organs
- especially in children and HIV patients
116
mycobacterium tuberculosis causes tuberculosis and is the leading
infectious disease killer in the world
117
which of the following stains could we use to detect mycobacterium tuberculosis
- gram
- spore
- acid-fast
acid-fast
118
describe the shape of mycobacteria and its cell wall
- rods
- gram (+) cell wall but stains very weakly with gram stain
- complex cell wall rich in lipids called mycolic acids
- lipids account for 60% of cell wall weight
119
describe acid-fast cell wall
- resistant to detergents, many antibiotics, and drying conditions
- slow growth
- protection from lysis after phagocytosis (along with the capsule)
- blocks fusion of phagosome with lysosome
- masks PAMPS on the bacterial surface
- capacity for intracellular growth within
macrophages -> "facultative intracellular
pathogen"
120
what is the epidemiology of TB
- humans are the only natural reservoir
- airborne transmission (ie respiratory droplet nuclei)
- very contagious (RO=12)
- low infectious dose (just about 10 bacilli)
121
what populations are at greatest risk for TB disease
- HIV+ individuals
- diabetics
- substance abusers
- low body weight/malnourishment
- immunocompromised
122
majority of TB cases in the US occur in which kind of patients
foreign-born and HIV-infected
123
infection by mycobacterium tuberculosis typically results in
asymptomatic lung infection
124
can immune response controls eliminated TB
no
125
TB yields
latent tuberculosis infection (LTBI)
126
people who have had TB may develop ____ later in life
active tuberculosis disease (ATBD)
- weight loss, night sweating, persistent cough, often blood-streaked sputum
127
what is the pathogenesis of tuberculosis
1. acid-fast bacilli are inhaled and spread to alveoli
2. phagocytized by alveolar macrophages
3. M. tuberculosis capsule and waxy mycolic acids block phagosome from fusing with lysosome to avoid destruction within macrophages
4. mycobacteria multiply in macrophages (intracellular pathogen). inflammatory response -> other phagocytes are attracted to the site
5. macrophages fuse together to form giant multinucleated cells
6. a granuloma (aka a tubercle) forms
128
what is the pathogenesis of active secondary TB disease (A2TBD)
- suppressed cell mediated immunity -> macrophages in tubercle die -> mycobacteria, enzymes, cytokines released -> forming area of necrosis
129
what happens in A2TBD
- tubercle ruptures, releases live mycobacteria into airways
- causes large lung defect called tuberculous cavity
130
how can A2TBD be transmitted
by coughing
131
what are the signs/symptoms of active pulmonary TB disease
- most TB cases are pulmonary:
- chronic cough, blood rust-colored sputum, high
fever, night sweats, weight loss, and fatigue
132
describe extrapulmonary TB
- bacteria that can spread to organs other than the lungs such as lymph nodes, brain, kidneys, bones
- called "miliary" TB -> when TB gets into circulation and spreads systemically to all parts of the body
133
extrapulmonary TB is most common in
children < 5 years and in HIV-infected patients
134
in an HIV-infected person, TB can develop in one of two ways:
1. person with LTBI becomes infected with HIV and then develops TB disease as the immune system is weakened
2. person with HIV infection becomes infected with M. tuberculosis and then rapidly develops TB disease
135
explain the process of tuberculin (aka mantoux) skin test for exposure to TB
purified protein derivatives (PPDs) from the Mtb bacterium are inserted intradermally and read 48-72 hours later
136
describe the lab detection of mycobacteria
- acid-fast bacilli ("AFB") in sputum
- a positive test for AFB in sputum means the person has active TB
- but...slow growth, 4-6 weeks
- new rapid PCR-based test: 1-5hours
137
what does BCG TB vaccine stand for
bacille calmette-guerin TB
138
how to prevent TB with BCG TB vaccine
- vaccine contains a live attenuated BCG strain
- BCG is a strain of mycobacterium bovis
- M. bovis causes TB in cows as well as humans
- most effective in preventing TB disease in babies and children
- has very limited effectiveness against pulmonary TB in adults
- not generally recommended in US
- used where TB is endemic
139
why are mycobacteria difficult to treat
- replicate slowly
- replicate intracellularly within macrophages
- cell wall is difficult to penetrate
- evolution of drug resistance
140
what is the treatment for mycobacteria
- people with LTBI can be given treatment to prevent them from developing TB disease
- combination antibiotic therapy taken every day for 6 months for uncomplicated TB, otherwise 12-18 months is standard and even longer if MDR-TB strain
- DOTS = direction observation treatment system
141
why do we still have TB
- treatment and prevention are difficult
- slow insidious disease
- long treatment duration
- BCG vaccine is inexpensive but inadequate
- LTBI is a silent reservoir
- affects the poor disproportionately
- expensive to both individual and society
- access to care for diagnosis and treatment
- contact tracing and DOTS
- HIV
- emergence of drug-resistant strains
142
like herpes simplex virus, which of the following belongs to the herpesviridae family
- rubeola virus
- rubella virus
- varicella zoster virus
- influenza
VZV
143
what are the two serotypes of herpes simplex virus and how are they transmitted
- HSV-1 = primarily oral contact
- HSV-2 = primarily genital contact
144
what is the epidemiology of HSV
- virus transmitted by direct contact
- greatest risk is contact with lesions or saliva
within few days of disease onset since many
virions present
- asymptomatic people can still be infectious
- can also be transmitted vertically by crossing the
placenta
145
what happens in the establishment of latent infection of HSV
1. virus penetrates into skin, where it replicates - PRIMARY
2. virus enters cutaneous neurons and migrates to a ganglion, where it remains in a latent state - LATENT
146
what happens in the reactivation of latent virus of HSV
1. virus can be subsequently be reactivated and travel through sensory neurons to the epidermis
2. a reccurent infection results
147
in what cells do primary acute infections occur
epithelial cells
148
latent infection of HSV persists in
sensory neurons in the ganglion
149
what can reactivate HSV
stresses like menstruation, sunlight, fever, and illness
150
describe the primary acute infection of labial herpes
- cold sores
- small blisters near mouth that break in a day or two
- blisters rupture -> painful superficial ulcers
- lesions heals within about 10 days, but virus persists throughout life as latent virus
151
describe recurrent infection from reactivation of latent virus of labial herpes
- cold sores
- usually less severe than initial infection
- includes tingling, itching, burning on lips
- blisters and ulcerations usually heal within 7-10 days
152
why aren't antibodies to HSV-1 protective against the recurrence of the disease?
- in general, antibodies can never bind to antigens on viruses and therefore are never protective
- the person is getting infected with a different serotype
- the virus is contained within neurons and the antibodies cannot penetrate the cells
the virus is contained within neurons and the antibodies cannot penetrate the cells
- no viral replication, so cannot recognize infection
153
the mumps virus causes which disease
mumps
154
are mumps enveloped, what is their reservoir, how is it transmitted, and how contagious is it
- enveloped
- human reservoir
- airborne transmission via respiratory droplet nuclei
- highly contagious
155
what are the signs/symptoms of mumps
- acute parotitis: painful swelling of the parotid salivary glands
- fever, pain in swallowing, nasal discharge
156
what are some complications of mumps infection
- viremia may occur (viruses present in bloodstream)
- complications are rare but include:
- orchitis (inflammation of the testicles) in
postpubertal males -> in rare cases, infertility
- encephalitis - inflammation of brain
- meningitis - inflammation of fluid and
membranes surrounding brain and spinal cord
- deafness
157
what is the immunity and prevention of mumps
- there is only one serotype so infection usually confers life-long immunity
- live, attenuated vaccine (MMR)
158
what is oral thrush caused by
overgrowth of the opportunistic yeast, candida albicans, which is part of the oral microbiota
159
what type of infection of oral thrush; exogenous or endogenous
endogenous
- non-transmissible
160
what are the risk groups of oral thrush
- most common in infants because they do not yet have well developed immune systems and have not acquired the robust normal microbiota that keeps candida in check in adults
- common in AIDS patients
161
what are the signs/symptoms of oral thrush
thick, white, "cottage-cheese," adherent growth on the mucous membranes of mouth and throat
- can easily be wiped off to expose an erythematous mucosa
162
what are two viral disease of the upper digestive system (UDS)
- labial herpes caused by herpes simplex virus
- mumps caused by mumps virus
163
what is a fungal disease of the UDS
oral thrush by candida albicans
164
what is a bacterial disease of the UDS
peptic ulcers by helicobacter pylori
165
what are signs/symptoms of peptic ulcers
- epigastric pain
- heart burn
- nausea associated with eating
166
what causes peptic ulcers
in most cases, caused by bacteria
167
what is the shape of helicobacter pylori
gram negative curved rods (vibrio) or spiral (spirillum) shaped
168
what does helicobacter pylori cause
- 90% of peptic ulcers
- gastritis
- cofactor in stomach cancer
169
what is the reservoir of helicobacter pylori and how is it transmitted
- human reservoir
- transmitted via by person-to-person saliva or fecal-oral
170
why doesn't helicobacter pylori get killed by stomach acids
- H. pylori goes to region of stomach (pyloric region) where the pH of the stomach is relatively higher
- it can sense pH and actively swim via flagella to
the region that has a higher pH
- H. pylori produces urease which breaks urea down into ammonia, this further increases the pH of the stomach
171
what is the pathogenesis of peptic ulcers
- bacteria penetrate and multiply in mucus layer
- bacteria attach but do not invade epithelium
- bacterial toxins and the inflammatory response damages mucus-secreting cells
- acid juices damage to the exposed tissue, causing a peptic ulcer
172
how does someone diagnose H. pylori
- endoscopy to visualize the GI tract and to take biopsy specimen
- a gastric mucosal biopsy and urease test
- biopsy sample is placed in media containing urea
- if H. pylori is present, its urease will hydrolyze the
urea, causing a pH shift and color change
- negative urease test = yellow/orange
- positive urease test = pink
173
what is the treatment for H. pylori
antacids and antibiotics
174
what kind of diseases are the leading cause of death worldwide in children < 5 years old
diarrheal diseases
175
how are diarrheal disease transmitted
by ingestion of contaminated food or water
- transmitted via fecal-oral route from food or water contaminated with animal or human feces
176
what are the moderate dehydration signs of diarrhea
- thirst
- restless behaviors
- decreased urine output
- sunken eyes, tears absent, decreased moisture in mouth
177
what are the severe dehydration signs of diarrhea
- lethargy, floppy, weak
- lack of urine output
- dry mouth
- poor skin turgor
- hypovolemic shock
178
what is the treatment and prevention of diarrhea
- diarrhea is often self-limiting
- rehydration therapy (IV or oral) used to counteract loss of fluid and electrolytes from diarrhea
- water alone insufficient; glucose increases
absorptive capacity of intestine
- oral rehydration salts (ORS) is glucose plus various
salts
- antibiotics usually not helpful
- sewage treatment, handwashing, chlorinating drinking water are important control measures
179
define bacterial gastroenteritis
inflammation of the GI tract due to an infection or toxin; associated with diarrhea, loss of appetite, nausea and/or vomiting
180
gastroenteritis can lead to
- food poisoning aka foodborne intoxication
- infectious diarrhea
181
what is the pathogenesis of food poisoning
- food contaminated with bacteria
- ingest preformed exotoxin (ingested bacteria are killed)
- damage to host tissues by the activity of the exotoxin
182
what is the pathogenesis of infectious gastroenteritis
- food contaminated with bacteria
- ingest bacteria that colonize the gut
- damage to host tissues by either bacteria replicating and invading the tissue or by bacteria adhering to the gut lining and secreting exotoxin (toxins are produced in vivo)
183
what are the signs/symptoms of food poisoning, is the onset rapid or slow, is it contagious, and is the recovery rapid or slow
- nausea, vomiting, followed by diarrhea
- rapid onset within hours after ingestion
- not contagious
- rapid recovery
184
what are the causative agents of food poisoning
- s. aureus
- bacillus cereus
- c. perfringens
185
when does diarrhea occur
when water is not absorbed or when it actually leaves intestinal cells and enters the intestinal lumen
186
describe secretory diarrhea
- often mediated by an enterotoxin
- if bacterial cause, then the infecting bacteria do not invade
- causes the "runs"
- watery diarrhea with loss of electrolytes and fluids from the intestines
- severe dehydration
- possibly accompanied by nausea and vomiting
- usually small intestine
187
describe invasive/inflammatory diarrhea
- typically due to bacteria invading the intestinal mucosa
- causes "the squirts"
- mucosal lining of the intestine is inflamed and becomes damaged; intestines can't absorb nutrients and water
- frequent, diarrhea containing mucus, pus, and sometimes blood in stool (dysentery)
- pain on defecation, colitis, and fever may also be present
- usually large intestine
188
enteric bacteria are gram-negative facultatively anaerobic ____ or ____ (curved rods)
rods or vibrio
189
how are bacterial infections of the LDS transmitted
fecal-oral transmission
190
intestinal pathogens sensitive to acid usually have ___ (high or low) infectious dose, since most are destroyed by acid
high
- generally transmitted by contaminated foods and water
191
acid-resistant pathogens have ___ (high or low) infectious dose
low
- transmitted through direct contact (hand to hand) or by contaminated foods and water
192
what are three examples of non-invasive enteric bacteria
- enteropathogenic e. coli (EPEC)
- enterotoxigenic e. coli (ETEC)
- vibrio cholerae
193
what are some characteristics of e. coli
- gram-neg bacilli
- ferments lactose (coliform)
- many strains part of normal microbiota and act as opportunists
- some strains have developed virulence through plasmid transfers and are primary pathogens
- strains groups into various pathovars based on the virulence factors
194
enterotoxigenic e. coli (ETEC) has what syndrome
watery diarrhea
- "travelers diarrhea"
195
enteropathogenic e. coli (EPEC) has what syndrome
watery diarrhea of long duration, most in infants
196
enterohemorrhagic e. coli (EHEC) has what syndrome
bloody diarrhea
- hemorrhagic colitis and hemolytic uremic syndrome (HUS)
197
enteroinvasive e. coli (EIEC) has what syndrome
blood diarrhea
198
describe EPEC
- non-invasive pathovar of e. coli
- does not produce toxins
- changes the microvilli of small intestines -> formation of attaching and effacing lesion
- prevents reabsorption of water into the cell
199
describe ETEC
- attaches to but does not invade surface epithelium of small intestine
- mediated by enterotoxins such as heat-labile enterotoxin (LT) which is an A-B exotoxin
200
what is the pathogenesis of ETEC
- LT binds to a receptor and activates adenylate cyclase
- adenylate cyclase produces elevated levels of cAMP
- elevated levels of cAMP cause cells to secrete excessive amounts of fluid and electrolytes into the lumen of the intestinal tract
201
what is the reservoir for ETEC, does it have a high or low infectious dose, it is endemic in what kind of countries, who are the at-risk groups, and what kind of diarrhea
- humans are the reservoir
- high infectious dose
- endemic in resource-limited countries
- children <5 years and travelers from non-endemic countries
- watery diarrhea
202
describe vibrio cholerae (shape, most common source, high or low infectious dose, invasive or non-invasive)
- gram-neg curved rods
- fecally contaminated water is the most common source
- high infectious dose
- non-invasive
203
what does vibrio cholerae cause
cholera
- secretory diarrhea
204
describe cholera toxin
- encoded by a bacteriophage
- A-B toxin
205
describe cholera disease
- depending on the strain, can be mild and self-limiting or very severe and life-threatening
- copious amounts of watery stool called "rice water" stool
- up to 20L a day
206
describe cholera in children
- may lost 50% of body weight over the course of an infection
- dehydration, lethargic, sunken eyes, flaccid skin -> hypovolemic shock -> death
207
what is the treatment for secretory diarrhea
- rehydration therapy is essential
- IV (intravenous)
- oral rehydration solution (water, glucose,
electrolytes)
- may also treat with antibiotics (eg highly virulent cholera strain)
- prevention: sanitation and safe water supplies
208
describe enteroinvasive e. coli (EIEC)
- invades and replicates within the mucosa of the large intestine
- moves from cell to cell via nucleating actin filaments
- elicits inflammatory response
- neutrophils damage and ulcerates the intestinal lining
- dysentery
209
describe enterohemmorhagic e. coli (EHEC)
- strains capable of causing epidemics
- most commonly identified EHEC in NA is E. coli 0157:H7 strain (O and H refer to surface antigens)
- invasive pathovar
- reservoir: ruminant animals (especially cattle)
- zoonotic
- typically associated with consumption of undercooked ground beef and raw green leafy veggies contaminated with cattle feces
- low infectious dose
210
describe shiga toxin (Stx) in e. coli
phage-encoded toxin
- A-B type exotoxin
- A subunit inhibits protein synthesis by acting on the rRNA of large ribosome -> lysis -> inflammation
- may travel by blood to the kidney
211
what are some symptoms of EHEC and possible complication
- bloody diarrhea and fatal hemorrhagic colitis
- possible complication: hemolytic uremic syndrome (HUS)
212
true or false - EHEC is a zoonotic pathogen while ETEC is not
true
213
describe shigella
- non-coliform, gram (-) bacilli
- humans are the reservoir
- low infectious dose
- invasive
214
how is shigella transmitted
- self inoculation from fecally contaminated hands
- ingestion of fecally contaminated foods
- person-to-person contact from fecally contaminated hands
215
children under 5 are 10 times more likely to contract which disease
shigella
216
describe shigellosis (bacillary dysentery)
- abdominal pain, fever
- bloody diarrhea with mucus and pus
- straining to defecate
- complications: febrile seizures, confused and other neurological complications may appear in children
217
what does the blood, mucus, and pus suggest
- colonization of the colonic mucosa without invasion
- secretion of toxin that enters the colonic mucosa and disrupts electrolyte transport
- inflammatory invasion of the colonic mucosa
inflammatory invasion of the colonic mucosa
218
describe shiga toxin (Stx)
- the genes for Stx in S. dysenteriae are located on the chromosome
- A-B toxin that inhibits protein synthesis by attaching the rRNA of the large ribosomal subunit
- HUS is not as common with shigella as with EHEC
219
describe salmonella enteritidis
- non coliform, gram (-) bacilli
- high infectious dose
- invasive
- does not produce Stx or actin tails like shigella
- reservoir: poultry (main) - zoonotic
220
how is salmonella enteritidis transmitted
- most human infections due to consuming food contaminated with animal feces
- especially undercooked poultry and eggs
221
is salmonella more or less sensitive to stomach acid as shigella
more sensitive
222
describe salmonellosis
- inflammatory diarrhea, usually mild and non-bloody
- nausea, vomiting
- most healthy individuals recover without treatment within 4-7 days
223
who are the high risk groups for severe salmenollosis
- children <5 years, elderly, immunosuppressed adults
- they require antimicrobial therapy to treat the infection
224
true or false - salmonella remains the leading cause of food-borne fatalities in the U.S.
true
225
describe campylobacter jejuni
- gram (-) spiral shaped or curved (vibrio) rods
- low ID
- invasive
- animal reservoir: poultry
- most common cause of bacterial diarrhea in the US
226
how is campylobacter jejuni transmitted
- poultry is common source of infection
- raw chicken fluids cross contaminate uncooked food
- campylobacter can be cultured from 60-100% of chickens purchased in supermarkets
- zoonotic
227
describe campylobacteriosis
- fever, nausea/vomiting
- watery diarrhea that transitions into inflammatory diarrhea with abdominal pain
- dysentery occurs in about half the cases
- complications include: irritable bowel syndrome and guillain barre syndrome (temp nerve paralysis)
228
true or false - a case of bacterial inflammatory diarrhea progresses to severe colitis
true
229
describe c. diff shape
- gram (+)
- obligate anaerobe
- spore-former
230
how is c. diff transmitted
usually by contact with contaminated health care worker's hands
- resistant to many antibiotics
- opportunistic pathogen
231
enterotoxins (A and B) bind to intestinal epithelial cells and do what two things
- kills mucosal epithelial cells
- inflammation, diarrhea
232
describe pseudomembranous colitis
- caused by enterotoxins that cause necrosis of the epithelial cell lining the colon
- dead epithelial cells, exudate, dead neutrophils, and bacteria form pseudomembranes
- bloody diarrhea and abdominal pain
233
can you treat c. diff with fecal microbiota transplants (FMT)
yes
234
what three toxins cause food poisoning
- s. aureus
- bacillus cereus
- c. perfringens
235
describe bacillus cereus causing food poisoning
- gram (+)
- endospore-forming
- facultative anaerobe
- soil bacterium
- transmission: via ingestion of toxin-contaminated food
- associated with rice
236
b. cereus enterotoxin acts as a
superantigen
237
describe c. perfringens causing food poisoning
- gram (+)
- endospore-forming
- obligate anaerobe
- found in soil but also cows and poultry
- transmission: via ingestion of toxin-contaminated food
- associated with beef or poultry
- outbreaks often happen in hospitals, prisons, nursing homes "food service germ"
238
describe viral gastroenteritis
transmission: fecal-oral route
- more than 95% of viral gastroenteritis hospitalizations occur in children under the age of 5
239
describe rotavirus
- most common cause of infantile gastroenteritis
- nearly all unvaccinated children infected before age 5
- reservoir: humans
240
describe the rotovirus
- naked virus
- transmission: fecal-oral route
- begin abruptly with vomiting and slight fever, followed shortly by profuse watery diarrhea
- usually clears within a week, but fatal dehydration can occur if fluids are not replaced
241
what is the vaccine for rotovirus
- oral rotavirus vaccine
- live attenuated vaccine
242
true or false - the most common viral cause of diarrhea in adults and the second most common viral cause of diarrhea in children (after rotavirus) is norovirus
true
243
what are the signs/symptoms of norovirus
- abrupt onset of explosive vomiting and watery diarrhea
- resolves after 24-48 hours
244
describe cyst (protozoan disease of LDS)
- non-replicating, dormant
- infectious
- resistant
- outside of host
245
describe trophozoite (protozoan disease of LDS)
- feeding and reproducing life form
- inside the host
246
describe giardia lambia
- intestinal protozoan with cyst and trophozoite forms
- moves via flagella
- transmitted fecal-oral route; waterborne
- beavers are a major reservoir
- zoonotic
247
true or false - giardiasis is the most commonly identified waterborne illness in the US and is associated with hikers drinking from the streams
true
248
what are symptoms of giardiasis
- non-invasive watery (secretory) diarrhea lasting 1-4 weeks
- fatty (greasy appearance), smelly watery diarrhea
- flatulence
- malnutrition (severe cases)
- about 50% of infections are asymptomatic carriers (cyst passers)
249
how to diagnose giardiasis
- a stool ova and parasite exam involves direct examination of a stool sample for the presence of cysts and trophozoites
- can be used to distinguish common parasitic intestinal infections
- ELISA and other tests are used
250
describe cryptosporidium parvum
- protozoan parasite
- reservoir: cattle
- causes cryptosporidiosis
- transmission via ingestion of water contaminated with animal feces (drinking water or swimming)
251
what is an oocyst
protected by a thick outer shell that allows it to survive outside the body for long periods of time and makes it very tolerant to chlorine disinfection
252
describe cryptosporidiosis
- non-invasive, secretory (eg watery) diarrhea
- self-limiting in immunocompetent persons (lasts 10-14 days)
- severe unrelenting and life-threatening diarrhea in immunocompromised hosts (AIDS)
253
how to diagnose cryptosporidiosis
ova and parasite exam: modified acid-fast staining of stool
254
describe shape of enterobius vermicularis
- helminth
- small (length of a staple) intestinal roundworm called pinworm
255
what is the enterobiasis epidemiology
- most common helminth infection in the U.S. usually in children
- transmitted via fecal-oral route
- reservoir: humans
256
enterobiasis symptoms
- eggs are very sticky and itchy
- perianal pruritis
- sleeplessness
