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Theme 2.1 Microbiology > Bacterial pneumonia > Flashcards

Bacterial pneumonia Flashcards

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1
Q

What is pneumonia?

A
  • an acute infection of the lung parenchyma

- distal to the terminal bronchiole

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2
Q

What causes pneumonia?

A 
caused by :
Bacteria
Virus
Fungus 
Inhalation of foreign substances
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3
Q

What are the common symptoms of pneumonia?

A 
common symptoms include:
fever 
persistent coughing 
chills 
shortness of breath 
fatigue
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4
Q

What are the different types of pneumonia?

A
  1. Community-Acquired Pneumonia:
  2. Aspiration Pneumonia
  3. Hospital-acquired or Nosocomial pneumonia
  4. Ventilator-associated pneumonia (VAP)
  5. Atypical pneumonia
  6. Viral pneumonia
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5
Q

Community-Acquired pneumonia

A

“a syndrome in which acute infection of the lungs develops in persons who have not been hospitalized recently and have not had regular exposure to the health care system.”

Streptococcus pneumoniae is the commonest cause
Usually follows Viral URTI

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6
Q

Aspiration pneumonia

A

occurs when stomach contents or a foreign object is inhaled into the air passages

Patients at risk:
>alcoholism
>epilepsy
>cerebrovascular accident

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7
Q

Hospital-acquired or nosocomial pneumonia

A

Hospital-acquired or nosocomial pneumonia

> occurs 48 hours or more after admission

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8
Q

Ventilator-associated pneumonia (VAP)

A

Ventilator-associated pneumonia (VAP)

is a type of HAP that develops more than 48 to 72 hours after endotracheal intubation.

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9
Q

Atypical pneumonia

A

refers to pneumonia caused by certain bacteria, including:

Legionella pneumophila,
Mycoplasma pneumoniae,
Chlamydophila pneumoniae

PCP (pneumocystis pneumonia) which has a prevalence of 22% among HIV-infected adults admitted with CAP in sub-Saharan Africa

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10
Q

What is the epidemiology of Community-acquired pneumonia (CAP)?

A

> the major cause of hospitalization and death
exacerbated by the HIV epidemic
CAP can occur in HIV-seropositive patients at any stage of the infection

> The spectrum of aetiological agents in HIV-infected individuals may differ from HIV-uninfected individuals with Streptococcus pneumoniae and tuberculosis being more commonly identified in HIV-infected individuals

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11
Q

Respiratory syncytial virus (RSV) is the commonest cause of?

A

viral CAP, especially in the first 3 years of life.

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12
Q

During influenza outbreaks, the circulating influenza virus

A

becomes the principal cause of CAP that is serious enough to require hospitalization

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13
Q

Respiratory syncytial virus, parainfluenza virus, human metapneumovirus, adenovirus, coronavirus, and rhinovirus are commonly detected in patients

A

with CAP (Community-acquired pneumonia)

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14
Q

The clinical spectrum of SARS-CoV-2 infection is wide, encompassing?

A

asymptomatic infection, fever, fatigue, myalgias, mild upper respiratory tract illness, severe life-threatening viral pneumonia requiring admission to hospital and death

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15
Q

Medical Risk factors for Community-acquired pneumonia.

A

Medical:

  • Age <1 year
  • Prematurity
  • Malnutrition
  • Immunosuppression
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16
Q

Social Risk factors for Community-acquired pneumonia.

A

Social:

  • Overcrowding
  • Inadequate housing
  • Passive tobacco smoke exposure
  • Indoor fuel exposure
  • Winter season
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17
Q

The most important predictors of patient morbidity and mortality are?

A
  1. age
  2. the presence of underlying disease
  3. severity of illness.
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18
Q

AGE is an important predictor of patient morbidity and mortality.

A
  1. Patients over 60 years of age have significantly higher mortality and should be treated more vigorously, with hospitalization being considered at an earlier stage than for a younger patient.
  2. There is an association of particular pathogens with different age groups
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19
Q

There is an association of particular pathogens with different age groups

A

> Streptococcus pneumoniae is more common in the elderly, although it does occur in all age groups

> Mycoplasma pneumoniae is much more common in the 20-40 age group

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20
Q

Underlying illness is an important predictor of patient morbidity and mortality.

A

Patients with chronic obstructive pulmonary disease (COPD) are at increased risk for CAP caused by H. influenzae and Mor. Catarrhalis

P. aeruginosa and other gram negative bacilli also cause CAP in persons who have COPD or bronchiectasis.

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21
Q

What causes community-acquired pneumonia?

A

*Bacterial cause:

  1. Streptococcus pneumoniae
  2. Haemophilus influenzae
  3. Staphylococcus aureus
  4. Mycobacterium tuberculosis
  5. Moraxella catarrhalis
  • Atypical causes
  • Viral causes
  • Anaerobic organisms:
    1. elderly
    2. patients with increased risk of aspiration

**polymicrobial infections

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22
Q

Polymicrobial (mixed) infections are fairly common in

A

the elderly and severely ill patients.

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23
Q

TB in patients with CAP

A
  • Importantly, between 18% to 40% of patients with CAP in South Africa may test positive for tuberculosis
  • Infection with Mycobacterium tuberculosis should always be considered

-common in immunocompromised patients
HIV infection

  • may present as an acute infection
  • possible cause in immunocompetent individuals, esp those not responding to conventional antibiotic therapy
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24
Q

Additional pathogens causing CAP in HIV-infected children

A 
Bacteria
Non-typhoid salmonella
Klebsiella pneumoniae
Streptococcus milleri
Escherichia coli
Methicillin-resistant Staphylococcus aureus

Fungi
Pneumocystis jirovecii (previously Pneumocystis carinii)
Candida species

Viral
Cytomegalovirus
Varicella zoster virus

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25
Q

Other viruses that cause CAP include

A
  1. the Middle East respiratory syndrome coronavirus (MERS-CoV), which recently emerged in the Arabian Peninsula,
    and
  2. avian-origin influenza A (H7N9)

both of these newly identified viruses have since spread elsewhere

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26
Q

Pneumonia in children

A

Bacteria are the major cause of pneumonia mortality in both HIV uninfected and HIV-infected children.
Streptococcus pneumoniae is the commonest cause of bacterial pneumonia.
Other bacteria isolated are Staphyloccocus aureus and less often Haemophilus influenzae type b (Hib).
RSV causes significant mortality and morbidity in both HIV-infected and uninfected children.

PCP is the predominant cause of pneumonia mortality in HIV-infected children less than 6 months of age.

no cause is found in about half the patients who are hospitalized for CAP

27
Q

How is pneumonia transmitted?

A
  1. Inhalation of small airborne infectious particles
  2. Aspiration of Naso-oropharyngeal flora
  3. Hematogenous spread to the lung from another site of infection
  4. Direct extension from a contiguous site of infection.
  5. penetration and contamination of the lung can occur due to accidental trauma (car accident) or surgery.
28
Q

What is the pathogenesis of pneumonia?

A

The microorganism enter through the respiratory route by:
inhalation
aspiration.

Reach bronchioles and multiply.
Inflammation occurs in alveolar spaces.

Pathological changes depend on:
type of organism
age
condition of the host/ patient.

29
Q

Three major cell types line the airway:

A
  1. the ciliated cell
  2. the mucous secreting goblet cell
  3. the secretory Clara cell
30
Q

Other mediators of innate immunity:

A

transepithelial dendritic cells

alveolar macrophages

31
Q

What are the Alveolar macrophages?

A

these cells can mediate phagocytosis of inhaled or aspirated pathogens

32
Q

What components does Alveolar lining fluid contain?

A
  1. surfactant,
  2. phospholipids,
  3. IgG, IgE, IgA,
  4. secretory IgA,
  5. certain complement components
33
Q

The respiratory epithelium has the ability to

A

respond to pathogens through pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs)

34
Q

Discuss Pneumonia in the face of COVID-19

A

Patients infected with the virus may be asymptomatic or have symptoms with varying degrees of severity involving predominantly the respiratory tract.

The pathogenesis of SARS CoV begins with virus interaction with host cells

SARS-CoV-2 enters the airways of a newly infected person

The viral S protein (spike protein) binds with high affinity to the angiotensin-converting enzyme 2 (ACE2) receptor found on the membranes of respiratory epithelial cells, mainly type II pneumocytes.

While the virus has its genome replicated, the host’s immune system is activated, inducing the recruitment of inflammatory cells with subsequent production of pro-inflammatory cytokines and chemokines, as well as the maturation of dendritic cells

35
Q

The immune response induced by SARS-CoV-2 infection is characterized by two phases:

A
  1. an initial immunoprotective phase and

2. an activation phase of the cytokine storm, which yields a more severe clinical manifestation

36
Q

In the initial immunoprotective phase. In the first phase what happens?

A

In the first phase, a robust adaptive response can control the virus and block inflammatory progression

37
Q

What is Streptococcus pneumonia?

A

AKA pneumococcus :
Normal inhabitant of upper respiratory tract
Colonizes nasopharynx in 40% of healthy adults and children
Children carry in the nasopharynx asymptomatically for about 4-6 weeks, often several serotypes at a time

38
Q

Discuss the streptococcus pneumonia before we had antibiotics and also what happened when we discovered antibiotics.

A

In the pre-antibiotic era, Streptococcus pneumoniae caused 95% of cases of pneumonia.

Recognized factors contributing to this decline (why cases decreased from 95% to 40%) include:

> the widespread use of pneumococcal polysaccharide vaccine in adults

> the universal administration of the pneumococcal conjugate vaccine in children

> decreased rates of cigarette smoking

39
Q

What are some of the other infections caused by Pneumococcus?

A

Other infections:

Sinusitis
otitis media
Meningitis

40
Q

How do Severe pneumococcal infections spread?

A

spread of bacteria to the bloodstream and the central nervous system.

41
Q

What are the characteristics of streptococcus pneumonia?

A
  • Gram-positive, lancet-shaped
  • cocci pairs of cocci (diplococci) or short chains
  • fragile bacterium
42
Q

How does streptococcus pneumoniae spread and what happens when it colonizes?

A
  1. S. pneumoniae is spread through airborne droplets.
  2. Colonisers the nasopharynx asymptomatically as part of the commensal microbiota of the upper respiratory tract.
  3. After colonization, if the bacterium is not cleared by the immune system, the bacterium is spread via horizontal dissemination into the lower airways and other organs and tissues, and becomes pathogenic
43
Q

Streptococcus pneumoniae is an opportunistic pathogen that takes advantage of hosts with?

A

Underdeveloped, weakened, and or deteriorating immune systems.

44
Q

What are the virulence factors of streptococcus pneumonia? (5)

A

Things that make it harmful and not easily killed by bacteria

1. Capsule 
composed of polysaccharide 
interferes with phagocytosis  
90 diff capsule types identified 
pneumococcal vaccines: based on various capsular antigens derived from the highly-prevalent strains.
  1. Cell Wall:
    peptidoglycan with teichoic acid
    contain phosphorylcholine :
    helps adhere receptors located on human cells.
  2. Pili
    Helps colonization of the upper respiratory tract
  3. Surface Proteins :
    penicillin-binding proteins (PBPs) :
    Binding sites of antibiotics
  4. Pneumolysin: cause lysis of host cells
45
Q

What is Haemophilus influenzae?

A

-small, Gram-negative bacterium

Infants and young children ( 5 years) Hib causes :
>bacteremia
>meningitis

Encapsulated organisms penetrate the epithelium of the nasopharynx and invade blood capillaries directly

46
Q

What are non-typeable strains of Haemophilus influenzae? and what do they cause?

A

Non-typable strains are less invasive, usually harbored as normal flora

Nontypable H. influenzae causes:

  1. ear infections
  2. sinusitis
47
Q

What are the virulence factors of Haemophilus influenza?

A
  1. Capsule:
    polyribosyl ribitol phosphate (PRP) capsule is an important virulence factor
    renders type b H. influenzae resistant to phagocytosis by PMNs
    Facilitates invasion
2. Cell wall:
contain lipooligosaccharide (LOS), which resembles the lipopolysaccharide (LPS) of Gram-negative bacilli but has shorter side chains
  1. Fimbriae:
    adherence to tissues is mediated by pili (fimbriae) - important precursor to colonization
  2. IgA proteases
    facilitates attachment to mucosal surfaces
  3. Outer-membrane proteins
    Involved in invasion
48
Q

Haemophilus influenza Strains are classified as:

A
  1. serotypable (if they display a capsular polysaccharide antigen) or
    nontypable (no capsule)

7 serotypes: identified on the basis of capsular polysaccharides (a-f)

**H. influenzae type b is the most virulent organism of these

49
Q

What is Moraxella catarrhalis? and what does it cause?

A
  1. Gram-negative cocci
  2. Resp pathogen
It Causes:
>Pneumonia especially in  elderly
>Otitis media
>Lower respiratory tract infections in COPD patients 
>sinusitis
50
Q

What are the Virulence factors of Moraxella catarrhalis?

A
  1. Outer-membrane proteins
  2. Lipo-oligosaccharides
  3. Pili
51
Q

What is Hospital-acquired pneumonia?

A

Pneumonia is the second most common nosocomial infection in critically ill patients
ET tubes interfere with host defenses and provide a direct route of entry for pathogens
Micro-aspiration of contaminated oropharyngeal secretions

52
Q

What is Hospital-acquired pneumonia caused by?

A
  1. Staphylococcus aureus
  2. Gram-negative bacterium

> Klebsiella pneumoniae
Pseudomonas aeruginosa.
Acinetobacter spp

53
Q

Pseudomaonas aeruginosa -

A

It is a Gram-negative, aerobic rod bacteria.

It causes:

  1. urinary tract infections
  2. respiratory system infections

It is an Opportunistic pathogen – especially in the hospital setting

It Colonizes sinks ,taps

It also Colonizes moist areas of human skin: ear , axilla , perineum

54
Q

Pseudomaonas aeruginosa Virulence factors

A

> Exotoxins
Lipopolysacc – endotoxin
Cytotoxic subs: help it invade tissues

  • Proteases
  • Haemolysins
  • Pyocyanin

> Porins
Pili/fimbriae:
-adhere to the epithelial cells of the upper respiratory tract

> naturally resistant to many antibiotics
due to the permeability barrier afforded by its Gram-negative outer membrane

> tendency to colonize surfaces
biofilm: makes Ps less susceptible to antibiotics

55
Q

What is Staphylococcus aureus and what infections does it cause?

A

Gram-positive cocci
Skin colonizer

Infections
>Skin and soft tissue - impetigo
>Pneumonia
>Bone & joint
>endocarditis
56
Q

Staphylococcus aureus - virulence factors

A
  1. Capsule
  2. Surface adhesins – protein A
  3. Teichoic acid – release of inflam cells
  4. Peptidoglycan – PBP’s associated with antibiotic resistance
  5. Toxins :
    PVL
57
Q

What is MRSA?

A

Methicillin-resistant Staph aureus

Resistant to many antibiotics

Resist due to alteration in the binding site of antibiotics (PBPs)

58
Q

What are the complications of Pneumonia?

A

Meningitis
Sepsis
Empyema: Empyema is the medical term for pockets of pus that have collected inside a body cavity

Respiratory failure
Extra pulmonary infections;
Arthritis
Osteomyelitis

59
Q

Vaccines for pneumonia?

A

protects against invasive disease
based on based on capsular antigens derived of the highly-prevalent strains.
serotypes represent 85-90% of those that cause invasive disease
Immunization is suggested for those at highest risk of infection

60
Q

What are the two causes of bacterial pneumonia that are vaccine-preventable?

A

Hib: Haemophilus influenzae type b

Pneumococcus

61
Q

In infants and young children of 5 years. What does Hib (Haemophilus influenzae type b) cause?

A

Infants and young children ( 5 years) Hib causes :
bacteremia
meningitis

**routine immunization of children against Hib (Haemophilus influenzae type b) has decreased the incidence of disease

62
Q

How do we prevent invasive pneumococcal disease (IPD)?

A

prevention of invasive pneumococcal disease (IPD)

= isolation of Streptococcus pneumoniae from a normally sterile site such as blood or cerebrospinal fluid.

63
Q

HIV positive children affected by Invasive pneumococcal disease

A

HIV + Children

8 x more likely to suffer multiple episodes of invasive pneumococcal disease (IPD), than HIV- children

Theme 2.1 Microbiology (10 decks)

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