Streptococcus pneumoniae Streptococcus pneumoniae (or pneumococcus) is a Gram-positive coccus seen in pairs, which is typically α-haemolytic, but can be variable. Pathogenesis Streptococcus pneumoniae has a polysaccharide capsule that protects…
The main characteristics of streptococci include the following. They are Gram-positive cocci arranged in pairs and chains. They are fastidious facultative anaerobes. They require rich blood-containing media. They may be…
Staphylococci are part of the normal flora and important human pathogens. There are more than 26 species but only a few are pathogenic. Staphylococcus aureus is the most invasive species,…
The incidence of an infection varies with changes in pathogen virulence and in the immunity of the host population. Many infectious diseases have a characteristic pattern. For example, meningococcal infection…
Infection is a major cause of mortality and morbidity in patients admitted to hospital. The most frequent types of infection are urinary tract, respiratory, wound, skin and soft-tissue infections, and…
Identifying an Outbreak An outbreak, whether in a hospital or the community, must first be recognized by clinical awareness and effective laboratory diagnosis; data must be managed centrally, a process…
Sources of Infection Infection is caused either by organisms from the host’s normal flora (endogenous infection) or by organisms transmitted from another source (exogenous infection). Endogenous Infection The normal flora…
Specimens Any tissue or body fluid can be subjected to microbiological investigation with the aim of identifying the infecting pathogen and predicting response to therapy. To optimize the diagnostic benefit…
Resistance occurs when a previously susceptible organism is no longer inhibited by an antibiotic at a concentration that can be safely achieved in clinical practice. Resistance can develop quickly because:…
Definitions Humans encounter bacteria, viruses and parasites that do not cause disease. An infection occurs when microorganisms cause ill-health. Term Definition Pathogen An organism capable of causing disease Commensal An…
