What is the top cause of infection by site?

From the Guidelines

The top cause of infection by site is often specific to the location, with the most common sites being the respiratory tract, urinary tract, bloodstream, and skin. In the context of COVID-19 associated bacterial infections, the most common sites of infection involve the lower respiratory tracts, bloodstream, and urinary tracts, with Klebsiella pneumoniae, Streptococcus pneumoniae, S. aureus, and Haemophilus influenzae being the most common pathogens isolated from clinical specimens 1. When considering the top cause of infection by site, it's essential to understand that different body sites have unique environmental conditions, available nutrients, and host defense mechanisms that influence the types of pathogens that can colonize and infect them. Some key points to consider include:

• In the respiratory tract, viruses like influenza and rhinovirus predominate, while Streptococcus pneumoniae is the leading bacterial cause.
• For urinary tract infections, Escherichia coli is the primary pathogen, accounting for 80-90% of community-acquired cases.
• Skin infections are commonly caused by Staphylococcus aureus and Streptococcus species.
• Bloodstream infections often involve Staphylococcus aureus, coagulase-negative staphylococci, and gram-negative bacilli such as E. coli.
• Central nervous system infections typically involve Streptococcus pneumoniae and Neisseria meningitidis. Understanding the common causative organisms by site helps guide empiric antibiotic therapy before culture results are available and informs infection prevention strategies 1. It's also important to note that the incidence of coinfections and secondary bacterial infections can vary depending on the site of infection and the underlying condition of the patient, with recent studies indicating that the incidence of coinfections ranged between 3.5% and 8%, and secondary bacterial infections between 13.1% and 20% 1. In terms of morbidity, mortality, and quality of life, it's crucial to prioritize effective antimicrobial therapy and infection prevention strategies to minimize the risk of complications and improve patient outcomes 1.

From the Research

Top Causes of Infection by Site

The top causes of infection by site can be broken down into different categories, including upper and lower respiratory tract infections.

• Upper respiratory tract infections are commonly caused by:
  • Rhinoviruses, which account for 20 to 30 percent of episodes of the common cold 2
  • Other viruses such as influenza, adenoviruses, and coronaviruses 2, 3
• Lower respiratory tract infections are commonly caused by:
  • Bacterial pathogens such as Streptococcus pneumoniae and Haemophilus influenzae 4, 5, 6
  • Viral pathogens such as human rhinovirus, influenza viruses, and human coronavirus 4, 3
  • Atypical bacteria such as Mycoplasma pneumoniae and Legionella pneumophila 2, 6

Specific Causes of Infection

• Streptococcus pneumoniae is a common cause of community-acquired pneumonia, accounting for 5.5% of cases overall and 9.2% of cases in patients with community-acquired pneumonia 4
• Haemophilus influenzae is another common cause of lower respiratory tract infections, accounting for 5.4% of cases overall and 14.2% of cases in patients with community-acquired pneumonia 4
• Human rhinovirus is the most common viral pathogen detected in lower respiratory tract infections, accounting for 20.1% of cases 4

Mixed Infections

• Mixed bacterial-viral infections are common in lower respiratory tract infections, with 10% of cases involving both bacterial and viral pathogens 4
• The most common combination of pathogens in mixed infections is Streptococcus pneumoniae and human rhinovirus 4