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Questions and Answers
Which of the following is a basic laboratory feature of staphylococci?
Which of the following is a basic laboratory feature of staphylococci?
- They are traditionally divided into 2 groups based on their ability to produce spores
- They appear spherical and form in clumps/clusters (correct)
- They are commonly found in acidic environments
- They are obligate anaerobes
Which of the following is a feature of coagulase-positive staphylococci?
Which of the following is a feature of coagulase-positive staphylococci?
- They can colonise nasal passages and other moist skin areas (correct)
- They are commonly found in extreme cold environments
- They are classified as obligate anaerobes
- They are unable to produce biofilms
What is the traditional division of staphylococci based on?
What is the traditional division of staphylococci based on?
- Their ability to clot blood plasma (correct)
- Their Gram staining characteristics
- Their ability to produce endospores
- Their resistance to antimicrobial agents
Which of the following is a characteristic of coagulase-negative staphylococci?
Which of the following is a characteristic of coagulase-negative staphylococci?
Which test is used to differentiate S. aureus from other staphylococci based on the presence of an enzyme that causes blood clot formation?
Which test is used to differentiate S. aureus from other staphylococci based on the presence of an enzyme that causes blood clot formation?
Which enzyme is determined by the ability of bacteria to reduce hydrogen peroxide into water and oxygen, resulting in the production of bubbles?
Which enzyme is determined by the ability of bacteria to reduce hydrogen peroxide into water and oxygen, resulting in the production of bubbles?
What is the most likely causative pathogen for the painful, red lump on the neck of the 19-year-old male?
What is the most likely causative pathogen for the painful, red lump on the neck of the 19-year-old male?
Is the infection exogenous or endogenous?
Is the infection exogenous or endogenous?
Does this infection require any further management?
Does this infection require any further management?
What percentage of healthy humans are colonized by Staphylococcus aureus?
What percentage of healthy humans are colonized by Staphylococcus aureus?
What is the main factor contributing to increased colonization of Staphylococcus aureus in humans?
What is the main factor contributing to increased colonization of Staphylococcus aureus in humans?
What is the distinguishing factor between methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus?
What is the distinguishing factor between methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus?
What is the portal of entry for S. aureus infections?
What is the portal of entry for S. aureus infections?
Which factor facilitates the attachment of S. aureus to blood clots and traumatised tissue?
Which factor facilitates the attachment of S. aureus to blood clots and traumatised tissue?
What is the main factor contributing to the spread of S. aureus infections person-to-person?
What is the main factor contributing to the spread of S. aureus infections person-to-person?
In which category of S. aureus infections does endocarditis usually occur?
In which category of S. aureus infections does endocarditis usually occur?
Which of the following is a characteristic of infections caused by clinically important streptococci?
Which of the following is a characteristic of infections caused by clinically important streptococci?
What is the main factor contributing to the pathogenesis of infections caused by clinically important streptococci?
What is the main factor contributing to the pathogenesis of infections caused by clinically important streptococci?
What is the recommended approach for diagnosing infections caused by clinically important streptococci?
What is the recommended approach for diagnosing infections caused by clinically important streptococci?
What is the portal of entry for pneumococcal infections?
What is the portal of entry for pneumococcal infections?
Which infection can result from turbulent flow through the heart, leading to bacterial attachment and vegetation formation?
Which infection can result from turbulent flow through the heart, leading to bacterial attachment and vegetation formation?
Which bacterium is typically found in the bowel flora and is associated with common vancomycin resistance?
Which bacterium is typically found in the bowel flora and is associated with common vancomycin resistance?
Which bacterium accounts for over 25% of clinical anaerobes and can cause aspiration pneumonia, sinusitis, brain abscess, and intra-abdominal abscesses?
Which bacterium accounts for over 25% of clinical anaerobes and can cause aspiration pneumonia, sinusitis, brain abscess, and intra-abdominal abscesses?
What laboratory test is used to differentiate Streptococcus pyogenes from other staphylococci based on the presence of an enzyme that causes blood clot formation?
What laboratory test is used to differentiate Streptococcus pyogenes from other staphylococci based on the presence of an enzyme that causes blood clot formation?
What is a distinguishing feature of Streptococcus pneumoniae when observed under a microscope?
What is a distinguishing feature of Streptococcus pneumoniae when observed under a microscope?
What is the main factor contributing to increased colonization of Staphylococcus aureus in humans?
What is the main factor contributing to increased colonization of Staphylococcus aureus in humans?
What type of resistance can pneumococci develop by altering penicillin-binding proteins?
What type of resistance can pneumococci develop by altering penicillin-binding proteins?
Which infections can be caused by Enterococci in at-risk patients, especially in hospital settings?
Which infections can be caused by Enterococci in at-risk patients, especially in hospital settings?
What is the diagnosis of streptococcal infections reliant on, in addition to clinical suspicion?
What is the diagnosis of streptococcal infections reliant on, in addition to clinical suspicion?
Which country ranks 8/29 in the EU/EEA for resistance rates of S. pneumoniae, highlighting the importance of knowing local resistance patterns when treating infections?
Which country ranks 8/29 in the EU/EEA for resistance rates of S. pneumoniae, highlighting the importance of knowing local resistance patterns when treating infections?
What is the main mode of spread for S. aureus infections person-to-person?
What is the main mode of spread for S. aureus infections person-to-person?
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Study Notes
Bacterial Infections: Pneumococcal Disease, Enterococci, and Streptococci
- Pneumococcus is a Gram-positive bacterium carried in the nasopharynx by 5-10% of healthy adults and 20-40% of healthy children, with over 90 serotypes and vaccines available against some.
- Pneumococcus causes invasive diseases like pneumonia, sinusitis, otitis media, and meningitis, spreading via respiratory droplets and invading the oropharynx.
- Pneumococcal pneumonia presents symptoms such as pleuritic chest pain, shortness of breath, and may lead to complications like parapneumonic effusion and bacteraemia.
- Enterococci, including E. faecium and E. faecalis, are typically found in the bowel flora, with common vancomycin resistance and causing infections in at-risk patients, especially in hospital settings.
- Enterococcal infections include urinary tract infections, endocarditis, bloodstream infections, wound infections, and intra-abdominal infections, particularly in patients with recent surgery, underlying diseases, or prolonged hospitalization.
- Infective endocarditis can occur due to turbulent flow through the heart, leading to bacterial attachment and vegetation formation, often following procedures that damage epithelial barriers.
- Anaerobic streptococcus Peptostreptococcus, which accounts for over 25% of clinical anaerobes, can cause a range of infections, such as aspiration pneumonia, sinusitis, brain abscess, and intra-abdominal abscesses.
- The diagnosis of streptococcal infections relies on clinical suspicion, appropriate sample collection, and laboratory tests like gram stain, culture, and identification techniques such as Lancefield grouping and antibiotic susceptibility testing.
- Laboratory diagnosis of Streptococcus pyogenes involves bacitracin disk testing, gram stain showing beta-hemolytic cocci in chains, and other specific identification methods.
- Laboratory diagnosis of Streptococcus pneumoniae involves identifying Gram-positive cocci in chains or diplococci, being alpha-hemolytic, and showing susceptibility to optochin.
- Pneumococci can develop antimicrobial resistance, altering penicillin-binding proteins and leading to low-level, intermediate, or high-level resistance, which is important to consider when treating patients.
- Antimicrobial resistance in S. pneumoniae varies geographically, with Ireland ranking 8/29 in the EU/EEA for resistance rates, highlighting the importance of knowing the local resistance patterns when treating infections.
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