Medical microbiology Flashcards
1
Q
What is a key epidemiology marker?
A
Death/mortality.
2
Q
Why is infection important in epidemiology?
A
It was and still is a major killer.
3
Q
Which infectious diseases were major killers in the last century?
A
Measles, HIV/AIDS, Hepatitis, Influenza, Respiratory viruses, Smallpox (eradicated).
4
Q
Which infectious diseases are of current and future concern?
A
HIV/AIDS, Influenza, SARS and Ebola, COVID, parasitic diseases, bacterial diseases.
5
Q
What threats are projected to increase global deaths?
A
Antimicrobial resistance, COVID, and another pandemic.
6
Q
What is an obligate pathogen?
A
A pathogen that can only reproduce inside a host.
7
Q
Give an example of an obligate pathogen.
A
Mycobacterium tuberculosis.
8
Q
What disease does Mycobacterium tuberculosis cause?
A
Tuberculosis.
9
Q
What are the characteristics of Mycobacterium tuberculosis?
A
Obligate pathogen, gram +ve, aerobe, actinobacteria.
10
Q
What is a facultative pathogen?
A
A pathogen that can cause disease in a host but can also live and reproduce in a non-pathogenic manner.
11
Q
Give an example of a facultative pathogen.
A
Vibrio cholerae.
12
Q
What disease does Vibrio cholerae cause?
A
Cholera.
13
Q
What are the characteristics of Vibrio cholerae?
A
Gram -ve, facultative anaerobe, proteobacteria.
14
Q
What is an opportunistic pathogen?
A
A pathogen that causes disease in a compromised host (e.g., weakened immune system).
15
Q
Give an example of an opportunistic pathogen that is gram -ve.
A
Pseudomonas aeruginosa.
16
Q
What does Pseudomonas aeruginosa cause?
A
Wound, blood, burn, and lung infections.
17
Q
What are the characteristics of Pseudomonas aeruginosa?
A
Gram -ve, proteobacteria.
18
Q
Give an example of an opportunistic pathogen that is gram +ve.
A
Staphylococcus aureus.
19
Q
What does Staphylococcus aureus cause?
A
Skin, wound, blood infections and endocarditis.
20
Q
What are the characteristics of Staphylococcus aureus?
A
Gram +ve, firmicutes phylum, bacilli class.
21
Q
What is a commensal pathogen?
A
Bacteria that live on the body surface or mucosa without harming human health but may elicit an immune response.
22
Q
Give examples of commensal gut bacteria.
A
Lactobacillus and Acidophilus.
23
Q
What are the characteristics of Lactobacillus and Acidophilus?
A
Gram +ve, firmicutes, bacilli; promote health and are part of the normal gut microbiota.
24
Q
What is pneumonia?
A
Swelling (inflammation) of tissue in one or both lungs.
25
What is bronchitis?
Infection of the main airways of the lungs (bronchi), causing irritation and inflammation.
26
Why are lower respiratory infections (LRI) significant?
They are the leading cause of death due to infectious disease in the world.
27
What were the global LRI stats in 2019?
2.5 million deaths, 672,000 children under 5, 1.23 million adults over 70.
28
Name 4 major pathogens involved in LRI.
Streptococcus pneumoniae, Haemophilus influenzae type B, Influenza virus, Respiratory syncytial virus.
29
What are the features of Streptococcus pneumoniae?
Gram +ve, cocci, opportunistic pathogen, extracellular bacteria.
30
What is bacterial carriage?
The harbouring of a potentially disease-causing organism without contracting the disease.
31
Is S. pneumoniae an obligate human host?
Yes.
32
How is S. pneumoniae transmitted?
Contact with secretions (saliva and mucus).
33
What percentage of invasive S. pneumoniae infections are fatal?
5%.
34
What are the treatment options for S. pneumoniae?
Oral B-lactams; IV: ceftriaxone, cefotaxime, or amoxicillin-clavulanic acid.
35
What vaccines are used for S. pneumoniae?
PCV7, PCV13 (babies), PPSV23 (adults over 65).
36
How does S. pneumoniae evolve genetically?
Through uptake and incorporation of exogenous DNA via natural competence.
37
What are the features of Haemophilus influenzae?
Gram -ve, pleomorphic coccobacillus, extracellular, opportunistic pathogen.
38
What divides typeable and non-typeable strains of H. influenzae?
Presence or absence of a polysaccharide capsule.
39
What is the colonisation rate of H. influenzae?
20% infants <1, 50% aged 5–6, 75% adults.
40
How is H. influenzae transmitted?
Airborne droplets and secretions.
41
What diseases do NTHi strains cause?
Bronchitis (children), pneumonia (adults with lung disease).
42
What antibiotics are used to treat H. influenzae?
B-lactams, cephalosporins, amoxicillin-clavulanic acid, TMP-SMX, tetracyclines, quinolones, macrolides.
43
What vaccine covers H. influenzae?
The 6-in-1 vaccine (3 doses at 8, 12, and 16 weeks).
44
What animals can influenza A infect?
Humans, pigs, horses, poultry, and wild migratory birds.
45
Which influenza strains affect humans?
Influenza A and B.
46
What is the influenza incubation period?
1–4 days.
47
What is the annual global burden of influenza?
~1 billion infections, 3–5 million severe cases, 300,000–500,000 deaths.
48
What type of virus is influenza?
Negative-sense, single-stranded RNA virus with 8 segments.
49
What do segments 1–3 of influenza RNA code for?
RNA-dependent RNA polymerases.
50
What does segment 4 code for?
HA (haemagglutinin) – binds to sialic acid receptors.
51
What does segment 5 code for?
NP (nucleoprotein) – binds viral RNA genome.
52
What does segment 6 code for?
NA (neuraminidase) – helps viral release and spread.
53
What is antigenic drift?
Gradual accumulation of mutations = minor changes in surface proteins.
54
What is antigenic shift?
Sudden major change when viral strains combine to form a new subtype (e.g., COVID).
55
Why is antigenic shift dangerous?
It can cause pandemics due to little to no population immunity.
56
What are post-influenza bacterial superinfections?
Flu weakens immune system, leading to secondary infections (e.g., S. pneumoniae, H. influenzae).
57
How is the flu vaccine produced?
Egg-based takes 6 months; cell-based takes 3 months.
58
What is herd immunity?
When enough people are vaccinated, disease transmission becomes difficult.
59
What is the incubation period of SARS-CoV-2?
2–14 days.
60
What is the infection rate in the population?
131 per 100,000 people.
61
What is Ro for COVID-19?
3.28 – average number of secondary infections per case.
62
What type of virus is SARS-CoV-2?
+ve single-stranded RNA virus.
63
What does the 1ab region encode?
Replicase proteins with proofreading activity.
64
What does the S gene encode?
Spike protein – binds to cell receptors.
65
What does the E gene encode?
Envelope protein – morphogenesis, assembly, budding.
66
What does the M gene encode?
Membrane glycoprotein.
67
What does the N gene encode?
Nucleocapsid protein – binds RNA genome.
68
What animal has the highest similarity to SARS-CoV-2?
RaTG13 bat coronavirus (96.2% similarity).
69
What pangolin virus shares key features with SARS-CoV-2?
MP789 – shares amino acids for ACE2 binding.
70
Is the life cycle of coronavirus needed for study?
No – mentioned in slides but not important.
71
What is diarrhea?
The passage of unusually loose or watery stools at least three times in 24 hours.
72
What are the four main types of diarrhea?
Acute watery, acute bloody (dysentery), persistent (14+ days), diarrhea with severe malnutrition.
73
What causes osmotic diarrhea?
Presence of non-absorbable solutes in the intestine.
74
What causes secretory diarrhea?
Excessive secretion of electrolytes and water into the gut.
75
What characterizes acute bloody diarrhea?
Presence of mucus and blood in stools.
76
What is persistent diarrhea?
Diarrhea lasting 14 days or longer.
77
What is diarrhea with severe malnutrition?
Diarrhea associated with Marasmus or Kwashiorkor.
78
How common are diarrheal diseases in children?
1.7 billion cases per year globally.
79
How often do adults experience diarrhea?
On average once every two years.
80
Why is diarrhea dangerous in children?
It is a leading cause of malnutrition in children under 5.
81
What is the leading viral cause of childhood diarrhea?
Rotavirus.
82
What impact did rotavirus vaccination have in Rwanda?
61-70% reduction in rotavirus cases.
83
Name 3 key bacterial causes of diarrhea.
Shigella, Salmonella, Campylobacter.
84
What are the 4 Shigella species?
S. flexneri, S. sonnei, S. boydii, S. dysenteriae.
85
What is the most common cause of food poisoning in the U.S. & Europe?
Campylobacter jejuni.
86
List types of diarrheagenic E. coli strains.
EPEC, EHEC/STEC, ETEC, DAEC, EAEC, EIEC.
87
What does EPEC stand for?
Enteropathogenic E. coli.
88
What does EHEC/STEC stand for?
Enterohemorrhagic / Shiga-toxin-producing E. coli.
89
What does ETEC stand for?
Enterotoxigenic E. coli.
90
What does DAEC stand for?
Diffusely adherent E. coli.
91
What does EAEC stand for?
Enteroaggregative E. coli.
92
What does EIEC stand for?
Enteroinvasive E. coli.
93
What bacteria causes cholera?
Vibrio cholerae.
94
What bacteria is linked to antibiotic-associated diarrhea?
Clostridium difficile.
95
What pathogen produces enterotoxins?
Toxigenic Staphylococcus aureus.
96
What are the main organs of the digestive system?
Stomach, duodenum, jejunum, ileum, colon, rectum.
97
What are 3 functions of the digestive system?
Digestion, absorption, elimination of waste.
98
What are some host defenses in the gut?
Mucus layer, microbiota, antimicrobial proteins like IgA.
99
What enzyme breaks sucrose into glucose and fructose?
Sucrase-isomaltase.
100
What enzyme breaks lactose into glucose and galactose?
Lactase.
101
What enzyme breaks maltose into glucose?
Maltase.
102
What causes secretory diarrhea in cholera?
Cholera toxin increases cAMP → chloride secretion via CFTR channels.
103
How much fluid can be lost per hour in cholera?
Up to 1L per hour.
104
What are 3 major sources of diarrheal disease transmission?
Water, food, human contact (fecal-oral).
105
Which vegetables were linked to ETEC?
Parsley.
106
Which vegetables were linked to EAEC?
Bean sprouts.
107
Which vegetables were linked to EHEC?
Radish sprouts, alfalfa sprouts, romaine lettuce.
108
What % of UK motorway users claimed to wash hands?
99%.
109
What % of men actually washed hands?
32%.
110
What % of women actually washed hands?
64%.
111
Where was fecal bacteria found in the UK study?
26% of hands, 16% of phones, 14% of banknotes, 10% of credit cards.
112
What % of people wash hands before eating?
Only 39%.
113
Name 3 key prevention strategies for diarrheal disease.
Safe water, sanitation, exclusive breastfeeding.
114
What hygiene measure can reduce diarrheal cases by 23-40%?
Hand washing with soap.
115
How much can handwashing reduce diarrhea in immunocompromised individuals?
By 58%.
116
How much does handwashing reduce school absenteeism?
By 29–57%.
117
What is ORS and what does it contain?
Oral rehydration salts; water, salt, and sugar.
118
Why is ORS effective?
Absorbed in small intestine and replaces lost fluids.
119
When is IV fluid needed?
Severe dehydration or shock.
120
What is a caution when using ORS?
Watch for osmotic diarrhea patients.
121
How does zinc help treat diarrhea?
Reduces duration by 25% and stool volume by 30%.
122
Why are nutrient-rich foods important?
Prevent malnutrition but may worsen osmotic diarrhea.
123
When is loperamide used?
For symptom relief; use with caution as it slows gut motility.
124
Are antibiotics always used?
No, only for specific infections; avoided in EHEC to prevent HUS.
125
What are the 6 key concepts to know?
Definition/types, mechanisms, epidemiology, pathogens, prevention, treatment.
