L.2 Streptococcus (alpha-haem) Flashcards
1
Q
What type of organisms are Gram-positive aerobic organisms?
A
Grow in chains/pairs, non-motile, non-spore forming
2
Q
Where can commensal microflora be found?
A
Mouth, skin, intestine, upper respiratory tract
3
Q
How are several species of Gram-positive aerobic organisms often carried?
A
Asymptomatically
4
Q
What test differentiates Gram-positive aerobic organisms from Staphylococcus species?
A
Catalase negative
5
Q
What are the two main classifications of Gram-positive cocci based on haemolytic properties?
A
Alpha-haemolytic and beta-haemolytic
6
Q
What are the examples of alpha-haemolytic organisms?
A
- S. Viridans
- S. pneumoniae
7
Q
What are the examples of beta-haemolytic organisms?
A
- S. pyogenes
- S. agalacteae
- Group A-H
8
Q
What is the family name of the genus Streptococcus?
A
Streptococcaceae
9
Q
What is the process of haemolysis?
A
Destruction of red blood cells
10
Q
What is alpha-haemolysis characterized by?
A
Damage (but not lysis) of RBCs in blood, producing a greenish tint
11
Q
What is beta-haemolysis characterized by?
A
Lysis of RBCs, resulting in transparent media around colonies
12
Q
What is the basis for classification into Lancefield groups?
A
C-substance polysaccharides
13
Q
What is the significance of Lancefield grouping?
A
Identifying pathogenic β-hemolytic streptococci
14
Q
What are the key differences in Lancefield groups?
A
- Disease patterns
- Antibiotic sensitivity
- Carriage vs. infection
15
Q
What are the most clinically significant groups of streptococci?
A
- GAS (Group A Strep)
- GBS (Group B Strep)
16
Q
Where is Group A Strep (e.g., S. pyogenes) commonly found?
A
Surface of skin and inside throat
17
Q
Where does Group B Strep (e.g., S. agalactiae) usually live?
A
Inside digestive tract and in women in vagina
18
Q
Which alpha-haemolytic streptococci do not have group specific antigens?
A
- S. pneumoniae
- S. viridans
19
Q
What are the two main types of Alpha-haemolytic Streptococci?
A
- Streptococcus pneumoniae
- Viridans streptococci
Many different species of Viridans streptococci exist.
20
Q
In what year did the WHO include S. pneumoniae as one of the priority pathogens?
A
2017
This designation reflects the high burden of disease associated with S. pneumoniae.
21
Q
What are the reasons for the prominence of S. pneumoniae as a cause of disease?
A
- High Carriage Rates
- Genetic adaptability
- Ability to shift from commensal to pathogenic interaction in its host
These factors contribute to its role in disease prevalence.
22
Q
What is the first step in the pathogenesis of pneumococcal disease?
A
Establishment of colonization
This is also referred to as the creation of the carrier state.
23
Q
What triggers the rapid inflammatory response in pneumococcal disease?
A
Gaining access to the normally sterile part of the airway
This access leads to disease manifestation.
24
Q
What factors contribute to the transition from colonization to infection?
A
- Host susceptibility
- Bacterial virulence factors
The exact mechanisms are not well understood.
25
What host factors are associated with increased susceptibility to pneumococcal disease?
* Preceding infections with respiratory virus
* Exposure to smoking
* Anatomical variations
* Suboptimal immunity in young children and elderly
## Footnote
These factors can increase the risk of developing pneumococcal disease.
26
What role does colonization play in the spread of S. pneumoniae?
It is a prerequisite for both transmission to other individuals and invasive disease in the carrier
## Footnote
Carriers can shed the bacterium in nasal secretions.
27
How can S. pneumoniae disseminate beyond its niche?
* Aspiration
* Bacteraemia
* Local spread
## Footnote
These mechanisms allow the bacterium to spread within the host.
28
Where does S. pneumoniae primarily colonize in both children and adults?
Nasopharynx
## Footnote
This is the primary site for colonization by S. pneumoniae.
29
What are the surface adhesins used by S. pneumoniae to bind to epithelial cells?
* PavA
* PsrP
* PspC
* CbpA
## Footnote
These adhesins facilitate the attachment to host cells.
30
What role do choline-binding proteins play in the adhesion of S. pneumoniae?
They attach to human receptors
## Footnote
This interaction is crucial for the colonization process.
31
What is the purpose of biofilm formation for S. pneumoniae?
To persist in the nasopharynx and resist clearance by the immune system
## Footnote
Biofilms enhance survival against host defenses.
32
How is biofilm formation regulated in S. pneumoniae?
Quorum sensing
## Footnote
This process allows bacteria to coordinate behavior based on population density.
33
What feature of S. pneumoniae prevents phagocytosis?
Capsule (polysaccharide coat)
## Footnote
The capsule acts as a protective barrier against immune cells.
34
What does IgA protease do in the context of immune evasion by S. pneumoniae?
Degrades mucosal IgA, preventing immune recognition
## Footnote
This helps the bacteria evade the immune response.
35
Is colonization by S. pneumoniae usually symptomatic or asymptomatic?
Asymptomatic
## Footnote
Most individuals do not show symptoms but can still transmit the infection.
36
What are the modes of spread for S. pneumoniae?
* Direct Contact (e.g., respiratory droplets)
* Indirect Contact (e.g., contaminated surfaces, hands)
## Footnote
These methods highlight how easily the bacteria can spread.
37
What factors enhance the transmission of S. pneumoniae?
* Viral Co-Infections (Influenza, RSV)
* Overcrowding & Poor Hygiene
* Children & Elderly
## Footnote
These factors increase the likelihood of pneumococcal spread.
38
What happens once S. pneumoniae is transmitted to a new host?
It can recolonize or invade deeper tissues if conditions allow
## Footnote
This indicates the potential for more severe infections.
39
What are the triggers for invasion?
Disruption of epithelial barriers, activation of virulence factors
## Footnote
Examples of disruption include viral infections, smoking, or immune deficiency.
40
What is the consequence of disruption of epithelial barriers?
Penetration of Mucosa
## Footnote
This can lead to various infections depending on the tissue affected.
41
How does the immune system evade infection?
Capsule resists complement-mediated opsonization, PspA blocks complement deposition
## Footnote
These mechanisms help pathogens avoid detection and destruction by the immune system.
42
What tissue-specific infection is associated with the lungs?
Pneumonia
## Footnote
Pneumonia is characterized by inflammation and alveolar damage.
43
What is the most common cause of Otitis Media?
S. pneumoniae
## Footnote
Otitis Media is the most common cause of middle ear infection in children.
44
What is the prevalence of S. pneumoniae in acute bacterial pneumoniae?
Most common cause of CAP worldwide, accounts for approx. 30% of all pneumoniae cases
## Footnote
Common in older adults and immunocompromised individuals.
45
What are complications of pneumonia caused by S. pneumoniae?
Bacteraemia/sepsis, disseminated organ damage
## Footnote
Complications can occur if the infection spreads beyond the lungs.
46
What percentage of people with pneumonia progress to invasive disease?
15-30%
## Footnote
This progression can lead to serious conditions like sepsis.
47
What is the leading cause of meningitis?
S. pneumoniae
## Footnote
Fatality rates can be up to 50% for meningitis caused by this organism.
48
How many serotypes of S. pneumoniae are there, and how many cause the majority of invasive infections?
Approx. 90 different serotypes, 8-10 cause majority of infections
## Footnote
These predominant serotypes are critical for understanding invasive pneumococcal disease.
49
What is the classification of S. pneumoniae infections?
Non-invasive and invasive infections
## Footnote
Non-invasive includes pneumonia and otitis media; invasive includes bloodstream infections and meningitis.
50
What is the seasonal prevalence of pneumonia caused by S. pneumoniae?
More prevalent in Winter months
## Footnote
Seasonality affects the incidence of respiratory infections.
51
What is the definition of invasive infections in S. pneumoniae?
Invasive S.p infection is a notifiable disease in Ireland
## Footnote
This highlights the public health significance of monitoring such infections.
52
What populations are particularly affected by invasive S. pneumoniae?
Young children, older adults, immunocompromised individuals
## Footnote
These groups are at higher risk for severe infections.
53
What is the mortality rate of invasive S. pneumoniae in adults aged 65 and older?
18/100,000
## Footnote
This indicates a significant risk in older populations.
54
What is the mortality rate of invasive S. pneumoniae in children under 2 years old?
0.4/100,000
## Footnote
This shows a lower risk compared to older adults.
55
What is IPD and why is it significant in Ireland?
Invasive pneumococcal disease (IPD) is a notifiable disease in Ireland
## Footnote
It includes conditions like meningitis and bloodstream infections.
56
How many deaths from IPD were reported in Ireland in 2023?
19 deaths
## Footnote
This highlights the impact of IPD in the population.
57
What is the primary virulence factor of S. pneumoniae?
Capsule
## Footnote
It is essential for colonization and prevents phagocytosis.
58
What is the composition of the capsule of S. pneumoniae?
Polysaccharides
## Footnote
This outermost layer plays a crucial role in virulence.
59
What role does the capsule play in the pathogenicity of S. pneumoniae?
Prevents recognition and engulfment by neutrophils/macrophages
## Footnote
It is anti-phagocytic and aids in immune evasion.
60
Why are non-encapsulated strains of S. pneumoniae typically non-pathogenic?
They lack the essential capsule for virulence
## Footnote
The capsule is crucial for causing disease.
61
What is the significance of the antigenic diversity of the S. pneumoniae capsule?
Over 90 strain types recognized based on capsular carbohydrates
## Footnote
This complexity contributes to vaccine design challenges and immune evasion.
62
What are pili in the context of S. pneumoniae?
Adhesins that facilitate attachment to epithelial cells
## Footnote
Important for initial colonization in the respiratory tract.
63
What is the function of Choline Binding Protein A (CbpA) in S. pneumoniae?
Binds to choline residues, aiding in adherence and invasion
## Footnote
CbpA is crucial for nasopharyngeal colonization.
64
What is the role of autolysins LytA in S. pneumoniae?
Cell wall degrading protease that triggers bacterial autolysis
## Footnote
It releases other virulence factors during the process.
65
What is pneumolysin and its mechanism of action?
A potent cytolysin that forms pores in host cell membranes
## Footnote
This leads to cell death and contributes to lung tissue damage.
66
What are the effects of pneumolysin on the host immune response?
Pro-inflammatory, activates the immune response, inhibits PMNs
## Footnote
It enhances inflammation and contributes to tissue damage.
67
True or False: The capsule of S. pneumoniae is non-essential for its virulence.
False
## Footnote
The capsule is indispensable for pneumococcal virulence.
68
What specimens are sent to the lab for the investigation of S. pneumoniae?
Sputum, pleural fluid, pus, aspirates, blood cultures
## Footnote
Quality of the sputum sample is important for accurate results.
69
What culture media is used for inoculation in the lab investigation of S. pneumoniae?
Blood agar, incubated at 37C with 5% CO2
## Footnote
The media is essential for the growth of fastidious organisms.
70
What is the first step in the lab investigation of S. pneumoniae after receiving specimens?
Inoculate specimens on culture media and prepare a slide for gram stain.
71
What type of bacteria is indicated by Gram positive diplococci that are lancet-shaped?
S. pneumoniae
72
What is the temperature requirement for growing S. pneumoniae in the lab?
37C
73
What type of hemolysis does S. pneumoniae exhibit on blood agar?
A-Haemolysis
74
What is the purpose of the Antimicrobial Susceptibility Test (AST) in the investigation?
To determine the susceptibility of the bacteria to various antibiotics.
75
What is the significance of the Biofire film array ME in the investigation?
It is a multiplex PCR system that tests for viruses, bacteria, parasites, yeast, and antimicrobial resistance genes.
76
What is cerebrospinal fluid used for in the context of S. pneumoniae investigation?
Direct molecular detection via lumbar puncture.
77
What atmosphere conditions are required for incubating S. pneumoniae?
5% CO2 with O2 and anaerobically.
78
Fill in the blank: The Gram stain result for S. pneumoniae shows Gram positive _______.
diplococci
79
What is the primary focus of the Day 1 procedures in the lab investigation?
Sample collection and initial inoculation for culture.
80
What is the final step reported on Day 3 of the lab investigation?
Report results.
81
True or False: S. pneumoniae is classified as a fastidious organism.
True
82
What type of colonies are observed in Alpha – Haemolysis?
Two distinct colonies:
* Draughtsman Colonies
* Mucoid Colonies
## Footnote
These colonies are characterized during the isolation process of bacteria.
83
What are the basic characterization tests for the identified organism?
Gram Positive diplococci, KOH Negative, Catalase negative, Oxidase negative
## Footnote
These tests help in the preliminary identification of the organism.
84
What is the purpose of Optochin Susceptibility testing?
To confirm the identification of the organism
## Footnote
It helps differentiate Streptococcus pneumoniae from other streptococci.
85
What characteristics define a preliminary identification of Strep pneumoniae?
Mucoid or Draughtsman Colonies on Blood Agar, GPDC, Catalase Negative, Optochin Susceptible, Bile Susceptible
## Footnote
These criteria are essential for confirming the identity of the bacteria.
86
What is Vitek or Maldi TOF Identification?
Mass spectrometry for identification of bacteria
## Footnote
This method is used for precise bacterial identification but may lack discrimination for closely related species.
87
What laboratory is mentioned for sending CSF samples?
IMSRL – Temple Street
## Footnote
This is the Irish meningitis and sepsis reference Lab.
88
What methods are used for confirmation of the bacterial identification?
Real Time PCR directly on specimen, Serogroup capsule – PCR
## Footnote
These molecular techniques provide accurate confirmation of the pathogen.
89
What are the main antimicrobial treatments for Strep pneumoniae?
Penicillin (β lactam), Erythromycin (Macrolide), Cefotaxime (Third generation Cephalosporin)
## Footnote
These are standard treatments but resistance is a growing concern.
90
What trend is observed in antimicrobial resistance among pneumococci?
Penicillin non-susceptible pneumococci (PNSP) increased with age:
* 11% in patients 18-39 years
* 29% in patients ≥75 years old
## Footnote
This highlights the need for monitoring resistance patterns in different age groups.
91
What additional resistance is observed in older patients?
Reduced susceptibility to cefotaxime and erythromycin
## Footnote
This indicates a need for careful selection of antibiotics in older populations.
92
What are the characteristics of Streptococcus viridans?
Commensals found in GI, respiratory, female genital tracts; most prevalent in oral cavity; low pathogenicity overall.
93
Which species are included in Streptococcus viridans?
* S. mitis
* S. oralis
* S. mutans
94
How does Streptococcus viridans enter the bloodstream?
Via minor trauma (e.g., dental work).
95
What condition is caused by Streptococcus viridans adhering to damaged heart valves?
Subacute Bacterial Endocarditis (SBE).
96
Who is at risk for Subacute Endocarditis?
Individuals with pre-existing valvular damage, prosthetic valves, or cardiac devices.
97
What may be required before dental procedures for certain patients at risk of SBE?
Prophylactic penicillin.
98
What does S. mutans produce on teeth?
Biofilm.
99
What is S. mutans associated with?
Dental plaque and tooth decay (caries).
100
What type of bacteria is Streptococcus viridans in terms of gram stain?
Gram-positive cocci in chains.
101
Is Streptococcus viridans catalase positive or negative?
Catalase negative.
102
Is Streptococcus viridans oxidase positive or negative?
Oxidase negative.
103
What type of anaerobe is Streptococcus viridans?
Facultative anaerobe.
104
Streptococcus viridans is described as _______.
[fastidious]
