n=11, axilla, n= 8), back (n=18), upper extremity (n=6), buttocks
(n=6), chest (n=6), lower extremity (n=5), neck (n=5), face (n=5),
scalp (n=5); a few patients were noted to have multiple cysts
simultaneously, explaining the overlap of location.
DISCUSSION
We have studied the results of inflamed EIC cultures in the population at our department to understand how often bacterial infection plays a role in the inflammatory process, and which are the most common infectious agents. A significant portion of cultures revealed bacterial infections of a broad range, however we found that 47% of the cultures revealed no bacterial growth or normal bacterial flora.
In comparison to inflamed EIC lesions in our study, Kuniyuki described 21% having no pathogenic bacterial growth. In our study, the most prevalent cultured bacteria, methicillin sensitive S. Aureus (MSSA), was relatively common; but this bacteria was not exceptionally prevalent in other studies.3 In a similar study from 2008, the most prevalent aerobe found was Coagulasenegative Staphylococcus (lugdunensis and epidermidis),3,4 yet in our patient population, only 4 cultures reported this result. S. Aureus was common in our patient group, a result found in some studies but not realized in others.4,5,6 There were no anaerobes found to be more prevalent than others, but overall appearing nearly equal in prevalence to other studies.4,5 The lab grew out anaerobic bacteria in 24% (n=18) of EIC’s were found on the back, with 15% (n=11) found on the groin.
Methicillin resistance was present in only 8 of 21 Staphylococcus aureus isolates. Furthermore, 47% of inflamed EIC lesions grew no pathogenic bacteria. Additionally, of the EIC lesions initially not treated systemically with antibiotics, only half later required therapy. Therefore, it appears that in our region, incision and drainage, followed by culture, and antibiotic therapy only in response to positive cultures is a regimen supported by the data. The clearance of symptoms in some patients with positive cultures without oral antibiotics suggests that immunocompetent individuals may improve with conservative therapy half of the time. This is similar to historic data from Diven et al who reported only 108 of 192 cultured lesions were positive for bacteria.5 In the setting of hidradenitis suppurativa, one case has supported lesion formation with friction. In the setting of culture positive for Cutibacterium acnes, we believe that inflammation may be triggered similar to acne lesions.7 The mechanism by which inflammation in cysts is triggered is unclear, however, histopathology of lesions supports foreign body reaction to cyst contents.8
Our work, though smaller than other studies, reaffirms concerns of overprescribing of oral antibiotics in cutaneous abscesses.2 The issue of antibiotic resistance should be kept in mind when prescribing an antibiotic of any nature, topical or oral. While not all courses of treatment recorded in our patients were antibiotics, both prescribed singularly and dually with other therapies, the overwhelming majority of treatments prescribed in various series were antibiotics.8.9 By prescribing only when sufficient warrant for prescription of an antibiotic exists, particularly in the case of bacterial infections, there are many suggested benefits including reducing the chances of increasing bacterial resistances, such as MRSA, as well as improving the health outcomes of the patient, including the reduction of side effects from antimicrobial therapy.10,11
Current guidelines from the Infectious Diseases Society of America released in 2014 recommend incision and drainage for all purulent lesions, with the addition of culture and sensitivity and empiric antibiotics or defined antibiotics in moderate (purulent infection with systemic signs of infection) to severe cases (patients who have failed incision and drainage plus oral antibiotics, with systemic signs of infection such as tachycardia and elevated temperature or abnormal white blood cell count, or the immunocompromised).11 A recent multi-center, placebocontrolled trial of therapies for small abscesses randomized incision and drainage alone (placebo) against incision and drainage plus either trimethoprim-sulfamethoxazole or clindamycin in the setting of six urban urgicare or emergency departments. This study demonstrated benefit of clindamycin and trimethoprim-sulfamethoxazole with incision and drainage over placebo in Staphylococcus aureus positive lesions (67% of the cases). “The cure rates among participants with an abscess that did not grow S. aureus in culture were similar for all treatment groups in the intention-to-treat population and the population that could be evaluated (P=0.99 for all comparisons)â€13 While Emergency Departments deal with abscesses, not necessarily cysts that develop erythema and other signs of inflammation, our series and previously reported cases, in the mild EIC with noted purulence, the dermatologist may perform incision and drainage with associated culture and sensitivity, and prescribing based on the results. Where empiric therapy is chosen, doxycycline is supported as first line therapy from our cases, however, the recent literature from emergency care supports oral clindamycin or oral trimethoprim-sulfamethoxazole therapy with incision and drainage over incision and drainage alone, with increased risk of side effects with both active agents. Usage for 5–10 days can be chosen depending on severity and response to therapy.13
In comparison to inflamed EIC lesions in our study, Kuniyuki described 21% having no pathogenic bacterial growth. In our study, the most prevalent cultured bacteria, methicillin sensitive S. Aureus (MSSA), was relatively common; but this bacteria was not exceptionally prevalent in other studies.3 In a similar study from 2008, the most prevalent aerobe found was Coagulasenegative Staphylococcus (lugdunensis and epidermidis),3,4 yet in our patient population, only 4 cultures reported this result. S. Aureus was common in our patient group, a result found in some studies but not realized in others.4,5,6 There were no anaerobes found to be more prevalent than others, but overall appearing nearly equal in prevalence to other studies.4,5 The lab grew out anaerobic bacteria in 24% (n=18) of EIC’s were found on the back, with 15% (n=11) found on the groin.
Methicillin resistance was present in only 8 of 21 Staphylococcus aureus isolates. Furthermore, 47% of inflamed EIC lesions grew no pathogenic bacteria. Additionally, of the EIC lesions initially not treated systemically with antibiotics, only half later required therapy. Therefore, it appears that in our region, incision and drainage, followed by culture, and antibiotic therapy only in response to positive cultures is a regimen supported by the data. The clearance of symptoms in some patients with positive cultures without oral antibiotics suggests that immunocompetent individuals may improve with conservative therapy half of the time. This is similar to historic data from Diven et al who reported only 108 of 192 cultured lesions were positive for bacteria.5 In the setting of hidradenitis suppurativa, one case has supported lesion formation with friction. In the setting of culture positive for Cutibacterium acnes, we believe that inflammation may be triggered similar to acne lesions.7 The mechanism by which inflammation in cysts is triggered is unclear, however, histopathology of lesions supports foreign body reaction to cyst contents.8
Our work, though smaller than other studies, reaffirms concerns of overprescribing of oral antibiotics in cutaneous abscesses.2 The issue of antibiotic resistance should be kept in mind when prescribing an antibiotic of any nature, topical or oral. While not all courses of treatment recorded in our patients were antibiotics, both prescribed singularly and dually with other therapies, the overwhelming majority of treatments prescribed in various series were antibiotics.8.9 By prescribing only when sufficient warrant for prescription of an antibiotic exists, particularly in the case of bacterial infections, there are many suggested benefits including reducing the chances of increasing bacterial resistances, such as MRSA, as well as improving the health outcomes of the patient, including the reduction of side effects from antimicrobial therapy.10,11
Current guidelines from the Infectious Diseases Society of America released in 2014 recommend incision and drainage for all purulent lesions, with the addition of culture and sensitivity and empiric antibiotics or defined antibiotics in moderate (purulent infection with systemic signs of infection) to severe cases (patients who have failed incision and drainage plus oral antibiotics, with systemic signs of infection such as tachycardia and elevated temperature or abnormal white blood cell count, or the immunocompromised).11 A recent multi-center, placebocontrolled trial of therapies for small abscesses randomized incision and drainage alone (placebo) against incision and drainage plus either trimethoprim-sulfamethoxazole or clindamycin in the setting of six urban urgicare or emergency departments. This study demonstrated benefit of clindamycin and trimethoprim-sulfamethoxazole with incision and drainage over placebo in Staphylococcus aureus positive lesions (67% of the cases). “The cure rates among participants with an abscess that did not grow S. aureus in culture were similar for all treatment groups in the intention-to-treat population and the population that could be evaluated (P=0.99 for all comparisons)â€13 While Emergency Departments deal with abscesses, not necessarily cysts that develop erythema and other signs of inflammation, our series and previously reported cases, in the mild EIC with noted purulence, the dermatologist may perform incision and drainage with associated culture and sensitivity, and prescribing based on the results. Where empiric therapy is chosen, doxycycline is supported as first line therapy from our cases, however, the recent literature from emergency care supports oral clindamycin or oral trimethoprim-sulfamethoxazole therapy with incision and drainage over incision and drainage alone, with increased risk of side effects with both active agents. Usage for 5–10 days can be chosen depending on severity and response to therapy.13
CONCLUSIONS
In the dermatology outpatient office inflamed epidermal inclusion cysts may not grow bacteria on culture in almost half of cases. Furthermore, bacteria that do grow can vary extensively and may favor Methicillin-sensitive staphylococcus aureus as it does in our institution, therefore incision and drainage with culture and therapy appropriate to the patient is ideal in mild EIC lesions to reduce overprescribing of antibiotics.
