GEN2608 Infectious Diseases
All cases
,Case 1: Hands up in the air
Community-acquired pneumonia
Community-acquired pneumonia (CAP) refers to an infection of the pulmonary parenchyma
that occurs outside of a healthcare facility, such as hospitals or long-term care facilities. It is a
common and potentially serious condition that affects individuals of all age groups.
Pathogens that cause CAP
CAP can be caused by various pathogens, including bacteria, viruses, fungi and rarely,
parasites.
Bacteria:
o Streptococcus pneumoniae (pneumococcus): this is the most common
bacterial cause of CAP. However, due to vaccination the incidence is
decreasing. (diplococci +)
o Haemophilus influenzae: particularly associated with COPD and other chronic
respiratory diseases.
o Staphylococcus aureus: can cause severe pneumonia, especially in
healthcare-associated cases. It’s CAP after a viral infection like COVID.
o Mycoplasma pneumoniae: common in young adults and usually causes milder
symptoms. (atypical, nothing happens when Gram-staining).
o Legionella pneumophila: associated with severe pneumonia, often acquired
through contaminated water sources. (atypical)
o Chlamydophila pneumoniae: similar symptoms to Mycoplasma pneumoniae
infection.
o E. coli (Gram-negative)
o Klebsiella pneumoniae (Gram-negative)
o P. aeruginosa (gram-negative)
Symptoms
CAP can present with a range of symptoms, which can vary in severity depending on the
individual, the causative pathogen, and underlying health conditions. Some common
symptoms associated with CAP are:
Respiratory symptoms:
2
, o Cough: often productive, with phlegm or sputum. The color and consistency of
the sputum may vary depending on the causative agent.
o Shortness of breath: difficulty breathing or a sensation of breathlessness,
especially during physical activity.
o Chest pain: sharp or stabbing chest discomfort, worsened by deep breathing
or coughing.
General symptoms:
o Fever: often accompanied by chills or sweating. The severity of fever can vary.
o Fatigue: feeling excessively tired or weak.
o Loss of appetite: reduced desire to eat.
o Rapid breathing: increased respiratory rate or short, shallow breaths.
o Rapid heartbeat: elevated heart rate, especially during physical exertion.
o Muscle aches: generalized body pain or muscle soreness.
o Headache: can be present, particularly with certain pathogens such as
influenza virus.
Other symptoms:
o Confusion or delirium: especially in older adults, CAP can cause changes in
mental status or confusion.
o Nausea, vomiting, or diarrhea: Sometimes present, particularly in bacterial or
Legionella pneumonia.
Physical examination findings:
o Presence or absence of a significant pleural effusion
o Increased respiratory rate
o Use of accessory muscles of respiration
o Palpation increased/decreased tactile fremitus
o Percussion dull to flat tone
o Auscultation
Crackles
Bronchial breath sounds
Pleural friction rub
o The older the patient is, the less obvious the symptoms are
How is it diagnosed?
CAP is diagnosed through a combination of medical history evaluation, physical examination,
and various diagnostic tests. The diagnostic process aims to identify the presence of
pneumonia, determine the severity, and identify the potential causative agent. Some
approaches to diagnosing CAP are:
Medical history evaluation: the healthcare provider will ask questions regarding
your symptoms, such as cough, shortness of breath, fever, chest pain, and any
associated factors. They may inquire about recent travel, exposure to sick individuals,
immunization history, and any underlying health conditions.
Physical examination: the healthcare provider will conduct a thorough physical
examination, which typically includes listening to the lungs with a stethoscope to
check for abnormal lung sounds, such as crackles or decreased breath sounds. They
may also assess vital signs, look for signs or respiratory distress, and examine other
relevant findings.
3
, Chest X-ray: a chest X-ray is commonly used to confirm the presence of pneumonia
and assess its extent and location within the lungs. It can help differentiate
pneumonia from other conditions and provide information about the severity of the
infection.
Laboratory tests:
o Blood tests: a complete blood count (CBC) can provide information about the
white blood cell count, which may be elevated in response to an infection.
Blood cultures may also be collected to identify the specific causative bacteria
and guide antibiotic selection.
o Sputum culture: if you produce sputum, a sample may be collected and
analyzed in a laboratory to identify the causative bacteria and guide antibiotic
treatment.
o Other laboratory tests: in certain cases, or based on the clinical
presentation, additional tests may be ordered to assess for specific
pathogens, such as viral polymerase chain reaction (PCR) tests or serology
for viruses or atypical bacteria.
o Urine antigen test: Used for the detection of S. pneumonia and Legionella.
S. pneumonia
Sensitivity: 70%
Specificity: >90%
Legionella > serogroup 1
Most common acquired cases
Sensitivity: 70%
Specificity: 99%
Other diagnostic procedures:
o Pulse oximetry: measurement of oxygen saturation levels using a small
device called a pulse oximeter. This helps assess the adequacy of oxygen
exchange in the blood.
o Arterial blood gas (ABG) analysis: in more severe cases or if oxygenation is
a concern, an arterial blood sample may be taken to measure blood gas levels
and assess respiratory function.
o Bronchoscopy: in certain cases, a bronchoscopy may be performed to obtain
samples directly from the airways or more detailed analysis.
Gram-staining:
o Pink Gram-negative bacteria
thin peptidoglycan layer pigment won’t stay
o purple Gram-positive bacteria
thick peptidoglycan layer pigment will stay
Biomarkers:
o CRP: C-reactive protein
o PCT: procalcitonin
Show inflammatory response and is particular to bacterial pathogens.
Treatment
The SWAB (Dutch Working Party on Antibiotic Policy) guidelines categorize patients with
community-acquired pneumonia (CAP) into four distinct categories based on the severity of
illness and specific risk factors. These categories help guide treatment decisions and are
based on the:
4
All cases
,Case 1: Hands up in the air
Community-acquired pneumonia
Community-acquired pneumonia (CAP) refers to an infection of the pulmonary parenchyma
that occurs outside of a healthcare facility, such as hospitals or long-term care facilities. It is a
common and potentially serious condition that affects individuals of all age groups.
Pathogens that cause CAP
CAP can be caused by various pathogens, including bacteria, viruses, fungi and rarely,
parasites.
Bacteria:
o Streptococcus pneumoniae (pneumococcus): this is the most common
bacterial cause of CAP. However, due to vaccination the incidence is
decreasing. (diplococci +)
o Haemophilus influenzae: particularly associated with COPD and other chronic
respiratory diseases.
o Staphylococcus aureus: can cause severe pneumonia, especially in
healthcare-associated cases. It’s CAP after a viral infection like COVID.
o Mycoplasma pneumoniae: common in young adults and usually causes milder
symptoms. (atypical, nothing happens when Gram-staining).
o Legionella pneumophila: associated with severe pneumonia, often acquired
through contaminated water sources. (atypical)
o Chlamydophila pneumoniae: similar symptoms to Mycoplasma pneumoniae
infection.
o E. coli (Gram-negative)
o Klebsiella pneumoniae (Gram-negative)
o P. aeruginosa (gram-negative)
Symptoms
CAP can present with a range of symptoms, which can vary in severity depending on the
individual, the causative pathogen, and underlying health conditions. Some common
symptoms associated with CAP are:
Respiratory symptoms:
2
, o Cough: often productive, with phlegm or sputum. The color and consistency of
the sputum may vary depending on the causative agent.
o Shortness of breath: difficulty breathing or a sensation of breathlessness,
especially during physical activity.
o Chest pain: sharp or stabbing chest discomfort, worsened by deep breathing
or coughing.
General symptoms:
o Fever: often accompanied by chills or sweating. The severity of fever can vary.
o Fatigue: feeling excessively tired or weak.
o Loss of appetite: reduced desire to eat.
o Rapid breathing: increased respiratory rate or short, shallow breaths.
o Rapid heartbeat: elevated heart rate, especially during physical exertion.
o Muscle aches: generalized body pain or muscle soreness.
o Headache: can be present, particularly with certain pathogens such as
influenza virus.
Other symptoms:
o Confusion or delirium: especially in older adults, CAP can cause changes in
mental status or confusion.
o Nausea, vomiting, or diarrhea: Sometimes present, particularly in bacterial or
Legionella pneumonia.
Physical examination findings:
o Presence or absence of a significant pleural effusion
o Increased respiratory rate
o Use of accessory muscles of respiration
o Palpation increased/decreased tactile fremitus
o Percussion dull to flat tone
o Auscultation
Crackles
Bronchial breath sounds
Pleural friction rub
o The older the patient is, the less obvious the symptoms are
How is it diagnosed?
CAP is diagnosed through a combination of medical history evaluation, physical examination,
and various diagnostic tests. The diagnostic process aims to identify the presence of
pneumonia, determine the severity, and identify the potential causative agent. Some
approaches to diagnosing CAP are:
Medical history evaluation: the healthcare provider will ask questions regarding
your symptoms, such as cough, shortness of breath, fever, chest pain, and any
associated factors. They may inquire about recent travel, exposure to sick individuals,
immunization history, and any underlying health conditions.
Physical examination: the healthcare provider will conduct a thorough physical
examination, which typically includes listening to the lungs with a stethoscope to
check for abnormal lung sounds, such as crackles or decreased breath sounds. They
may also assess vital signs, look for signs or respiratory distress, and examine other
relevant findings.
3
, Chest X-ray: a chest X-ray is commonly used to confirm the presence of pneumonia
and assess its extent and location within the lungs. It can help differentiate
pneumonia from other conditions and provide information about the severity of the
infection.
Laboratory tests:
o Blood tests: a complete blood count (CBC) can provide information about the
white blood cell count, which may be elevated in response to an infection.
Blood cultures may also be collected to identify the specific causative bacteria
and guide antibiotic selection.
o Sputum culture: if you produce sputum, a sample may be collected and
analyzed in a laboratory to identify the causative bacteria and guide antibiotic
treatment.
o Other laboratory tests: in certain cases, or based on the clinical
presentation, additional tests may be ordered to assess for specific
pathogens, such as viral polymerase chain reaction (PCR) tests or serology
for viruses or atypical bacteria.
o Urine antigen test: Used for the detection of S. pneumonia and Legionella.
S. pneumonia
Sensitivity: 70%
Specificity: >90%
Legionella > serogroup 1
Most common acquired cases
Sensitivity: 70%
Specificity: 99%
Other diagnostic procedures:
o Pulse oximetry: measurement of oxygen saturation levels using a small
device called a pulse oximeter. This helps assess the adequacy of oxygen
exchange in the blood.
o Arterial blood gas (ABG) analysis: in more severe cases or if oxygenation is
a concern, an arterial blood sample may be taken to measure blood gas levels
and assess respiratory function.
o Bronchoscopy: in certain cases, a bronchoscopy may be performed to obtain
samples directly from the airways or more detailed analysis.
Gram-staining:
o Pink Gram-negative bacteria
thin peptidoglycan layer pigment won’t stay
o purple Gram-positive bacteria
thick peptidoglycan layer pigment will stay
Biomarkers:
o CRP: C-reactive protein
o PCT: procalcitonin
Show inflammatory response and is particular to bacterial pathogens.
Treatment
The SWAB (Dutch Working Party on Antibiotic Policy) guidelines categorize patients with
community-acquired pneumonia (CAP) into four distinct categories based on the severity of
illness and specific risk factors. These categories help guide treatment decisions and are
based on the:
4
