What is the cause of persistent cellulitis in a 60-year-old patient with prostate cancer on prednisolone (5 mg daily) and flucloxacillin (every 6 hours), and does the antibiotic need to be changed?

From the Guidelines

The patient's cellulitis is likely not improving due to inadequate antibiotic coverage, and the antibiotics should be changed to a broader-spectrum regimen. I recommend broadening coverage with a combination therapy such as piperacillin-tazobactam 4.5g IV every 6 hours or meropenem 1g IV every 8 hours, plus vancomycin dosed according to weight (typically 15-20 mg/kg every 12 hours) 1. This change is necessary because the current flucloxacillin regimen is likely insufficient given the patient's risk factors, including immunocompromised state from prostate cancer and steroid use 1. The patient's prednisolone use, even at a low dose of 5 mg daily, impairs immune function and can mask signs of worsening infection. Additionally, prostate cancer may affect overall immune status. The lack of improvement after 4 days suggests either resistant organisms (possibly MRSA or gram-negative bacteria) or deeper tissue involvement that flucloxacillin alone cannot adequately treat. Some key points to consider in the management of this patient include:

• Blood cultures should be obtained before changing antibiotics, and consideration should be given to imaging studies to rule out deeper infection such as abscess or osteomyelitis 1.
• The patient may also benefit from elevation of the affected limb, proper wound care if applicable, and close monitoring of inflammatory markers 1.
• The optimal duration of antibiotic therapy for skin and soft tissue infections (SSTIs) is still a topic of debate, with some studies suggesting that shorter courses may be adequate, but further study is needed to evaluate the optimal duration of antibiotic therapy for SSTIs 1. Given the patient's risk factors and the lack of improvement with the current regimen, it is reasonable to consider a broader-spectrum antibiotic regimen and to monitor the patient closely for signs of improvement or worsening infection.

From the Research

Causes of Persistent Cellulitis

• The cause of persistent cellulitis in a 60-year-old patient with prostate cancer on prednisolone (5 mg daily) and flucloxacillin (every 6 hours) can be attributed to various factors, including the underlying condition of the patient, the type of bacteria causing the infection, and the effectiveness of the antibiotic treatment 2, 3.
• Cellulitis is a clinical diagnosis based on the history of present illness and physical examination, and it can be difficult to diagnose due to a number of infectious and non-infectious clinical mimickers 2.
• The majority of non-purulent, uncomplicated cases of cellulitis are caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus, and appropriate targeted coverage of this pathogen with oral antibiotics such as penicillin, amoxicillin, and cephalexin is sufficient 2.

Antibiotic Treatment

• The patient is currently on flucloxacillin, which is a commonly prescribed antibiotic for the treatment of cellulitis, particularly in Ireland and the United Kingdom 4.
• However, the effectiveness of flucloxacillin in treating cellulitis caused by methicillin-resistant Staphylococcus aureus (MRSA) is limited, and antibiotics with activity against community-associated MRSA, such as trimethoprim-sulfamethoxazole and clindamycin, may be preferred empiric therapy for outpatients with cellulitis in the community-associated MRSA-prevalent setting 5.
• The decision to change the antibiotic treatment should be based on the clinical presentation, laboratory results, and the patient's response to the current treatment, as well as the potential risks and benefits of changing the antibiotic regimen 4, 5.

Considerations for Changing Antibiotic Treatment

• The patient's underlying condition, such as prostate cancer, and the use of prednisolone, which can suppress the immune system, should be taken into consideration when deciding whether to change the antibiotic treatment 2, 3.
• The potential for antibiotic resistance, particularly in the case of MRSA, should also be considered, and antibiotics with a narrower spectrum of activity may be preferred to minimize the risk of resistance 5, 6.
• The patient's clinical response to the current treatment, including any signs of improvement or worsening of symptoms, should be closely monitored, and adjustments to the antibiotic treatment should be made as necessary 4, 5.