Abscesses are accumulations of pus in the tissues and any organism isolated from them may be of significance. They occur in many parts of the body as superficial infections or as deep-seated infections associated with any internal organ. Many abscesses are caused by Staphylococcus aureus alone, but others are caused by mixed infections. Anaerobes are predominant isolates in intra-abdominal abscesses and abscesses in the oral and anal areas. Members of the "Streptococcus anginosus" group and Enterobacterales are also frequently present in lesions at these sites. Post-operative wound infections arise when microorganisms contaminate surgical wounds during an operation or immediately afterwards. Colonised body sites are frequent sources of pathogens, although they may be transmitted via medical and nursing staff or via inanimate objects from other patients or elsewhere in the hospital environment.
Organisms most commonly isolated include:
- S. aureus including MRSA.
- Bacteroides species
- Clostridium species
- Enterobacterales
- Pseudomonads
- β-haemolytic streptococci
- Enterococci
- Peptostreptococcus species
Coagulase-negative staphylococci and coryneforms isolated from post-operative sites overlying implants or prostheses may indicate infection. This is particularly true in the presence of a sinus tract in direct communication with the joint. However, with the exception of S. aureus, superficial flora do not necessarily represent the flora deep inside a wound and cultures should be interpreted with care.
PLEASE NOTE: Samples and accompanying relevant patient/ isolate data maybe referred for confirmatory or further laboratory testing to Reference laboratories. Relevant Public Health departments may also be notified IF a notifiable disease is identified under the Infectious Diseases (Amendment) Regulations 2020 (S.I. No. 53/2020).
Preparation of patient: Collect specimens before antimicrobial therapy where possible.
Precautions: Samples of pus are preferred to swabs. However, pus swabs are often received (when using swabs, the deepest part of the wound should be sampled, avoiding the superficial microflora). If processing is delayed, refrigeration is preferable to storage at ambient temperature. Delays of over 48hr are undesirable.
