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Chronic infections, characterized by prolonged inflammation and slow progression, present a daunting challenge to medical professionals due to their intricate diagnosis and complex treatment. These infections often occur in sites such as wounds or surgical implants and are frequently associated with bacterial biofilms.
Three pivotal steps are integral to the diagnosis of chronic infections. First, the bacteria must be sampled, then identifying the causative agent, and finally, confirming if the bacteria exist in a biofilm. An interesting exception to the challenge of diagnosing chronic infections is found in cystic fibrosis, where specimens can be easily obtained from patients’ phlegm, cultured, and diagnosed.
Yet, for most chronic infections, diagnosis remains challenging. The main reason is the presence of multiple organisms; chronic wounds often harbour more than five different bacterial types, making identifying a single causative agent difficult. There can be hurdles even with advanced diagnostic methods such as polymerase chain reaction (PCR) and growth media culture. Not all bacteria can be cultured in a clinical laboratory, and PCR technology, despite its accuracy, cannot differentiate between live and dead bacteria. Consequently, PCR is best used to confirm diagnoses when a single cause of infection is known, but it cannot serve as the sole diagnostic method.
Sample collection methods for chronic wounds often result in diagnostic inaccuracies. The commonly employed technique, involving a cotton stick swab across the wound surface, can inadvertently pick up bacteria such as Staphylococcus aureus from the skin surface while missing the deeper Pseudomonas aeruginosa infections. The inhomogeneous bacterial distribution within the wound and variations in bacterial count depending on the sample collection site further undermine the diagnostic value of wound biopsies.
Blood culture, while suitable for acute infections, proves ineffective for chronic infections due to the localized nature of inflammation. The quest for a definitive sampling method continues, necessitating ongoing innovative research.
So, what can be done with our current resources?
Bacterial culture, while imperfect, remains the standard method for diagnosing chronic infections in most clinical settings. Despite the challenges, the presence of culturable bacteria is still a strong indication of an infection. Moreover, sensitivity tests can guide the selection of an appropriate treatment. Bacterial culture can also estimate the number and types of bacteria present in the wound, albeit without determining whether the bacteria exist in planktonic or biofilm states, which could significantly influence treatment strategies.
Microscopy serves as a valuable tool in identifying bacterial biofilms. It can confirm the presence of a biofilm infection, examine its interaction with tissue, and ascertain if inflammatory cells are present. However, microscopy is a labour-intensive and time-consuming process, requiring the expertise of skilled microbiologists for accurate results.
Currently, no standalone diagnostic method offers a fast, accurate, and reliable diagnosis for chronic infections. Combining techniques, including bacterial culture, molecular identification, and microscopy, is necessary to unveil the disease’s cause.
Without an accurate diagnosis, it’s impossible to provide effective treatment. Therefore, early diagnosis and prompt treatment are crucial for chronic infections, as they can mitigate the risk of biofilm formation and reduce the need for invasive procedures, like debridement or amputation. Additionally, patients’ medical histories, including recurrent infections and predisposing factors such as implanted medical devices, diabetes, obesity, etc., can assist clinicians in confirming their diagnosis of chronic infections.
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