Bacterial Infections Quiz

Bacterial Infections: Pneumococcus, Enterococci, Streptococcus, and Diagnosis

• Streptococcus pneumoniae, a Gram-positive cocci, is carried by 5-10% of healthy adults and 20-40% of healthy children.
• It has a polysaccharide capsule with over 90 serotypes, allowing typing of strains, and vaccines are available against some serotypes.
• The bacteria cause invasive pneumococcal disease, spread through respiratory droplets, and invade the oropharynx mediated by adhesins.
• Pneumococcal pneumonia symptoms include pleuritic chest pain, shortness of breath, and may lead to complications such as parapneumonic effusion and bacteraemia.
• S. pneumoniae is a common cause of sinusitis, otitis media, meningitis, and bloodstream infections.
• Enterococci are found in the bowel flora, are usually low virulence, and are resistant to vancomycin.
• Enterococcal infections occur in at-risk patients, especially those with recent surgery, underlying disease, or prolonged hospitalization.
• Infections include urinary tract infections, endocarditis, bloodstream infections, wound infections, and intra-abdominal infections.
• Infective endocarditis is caused by bacteria attaching to damaged heart valves and forming vegetations.
• Anaerobic streptococcus Peptostreptococcus can cause infections such as aspiration pneumonia, sinusitis, brain abscess, intra-abdominal abscesses, and pelvic infections.
• Diagnosis of streptococcal infections involves clinical suspicion based on features, appropriate samples sent to the laboratory, and identification through Gram stain, culture, and serology.
• Antimicrobial resistance in S. pneumoniae includes altering the structure of penicillin-binding proteins, leading to different levels of resistance. In 2020, the resistance rate in Ireland was 17.6%.

Streptococcal Infections Overview

• Streptococcal pharyngitis is a common childhood bacterial infection, occasionally due to Group C or G, spread through person-to-person contact via droplets, facilitated by overcrowding, with an incubation period of 2-4 days.
• Symptoms of streptococcal pharyngitis include sore throat, fever, headache, and nausea, with physical examination revealing redness, oedema, lymphoid hyperplasia, enlarged tonsils with exudate, and tender lymph nodes.
• Complications of streptococcal infections include suppurative complications like peritonsillar abscess and non-suppurative sequelae like acute glomerulonephritis and acute rheumatic fever.
• Scarlet fever, characterized by delayed-type skin reactivity to a pyrogenic toxin with pharyngitis and rash, is associated with streptococcal infections.
• Streptococcal toxic shock syndrome is a serious infection with a mortality rate approaching 40% and is characterized by soft tissue inflammation, fever, chills, and multi-organ failure.
• Rheumatic fever, associated with streptococcal pharyngitis, can lead to cardiac tissue damage, while acute glomerulonephritis, also associated with streptococcal pharyngitis, can lead to permanent renal damage.
• Streptococcus agalactiae (Group B Streptococci) can cause neonatal sepsis and is carried by 10-40% of women intermittently in the vagina, with risk factors including maternal colonization and premature delivery.
• Group B Streptococci's virulence mechanisms include capsule polysaccharide, haemolysins, hyaluronidase, and surface proteins, with different serotypes associated with colonisation and disease.
• Other β-haemolytic streptococci, like Group C and G, and α-haemolytic streptococci, including Streptococcus pneumoniae, can cause similar diseases as Group A streptococcus without the immunological complications.
• Streptococcus pneumoniae is the most likely causative pathogen in a clinical case of an 80-year-old female with productive cough, shortness of breath, pleuritic chest pain, and fever.
• When S. pneumoniae is cultured on blood agar, it is most likely to exhibit alpha haemolysis.