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Primary Care Corner with Geoffrey Modest: antibiotics for skin abscesses?

10 Jul, 17 | by

by Dr Geoffrey Modest

A recent article found that either clindamycin or trimethoprim/sulfamethoxazole (TMP/SMX) are superior to placebo for uncomplicated skin abscesses (see Daum RS. N Engl J Med 2017;376:2545-55 ).

Details:

— multicenter, prospective, double-blind trial of 786 outpatient adults and children who had a skin abscess <5 cm in diameter (or <3 cm if 6-11 months old, <4 cm if 1-8 yo), and two of: erythema, swelling/induration, local warmth, purulent drainage, tenderness.

— patients randomized to clindamycin 150 mg TID vs TMP/SMX 80/400 mg BID vs placebo, for 10 days

— 57% male, mean age 25.5 (64% > 18yo/13% 9-17yo/21% 1-18yo/2% <1yo),  62% African-American/31% white, temperature 37°C, area of wound 4 cm², surrounding erythema 27 cm²

— all had incision and drainage of their abscess

— Exclusion criteria: infection in a body site requiring specialized management (perirectal, genital, hand infection), human or animal bites, oral temperature higher than 38.5°C (38.0°C in children 6-11 months of age), systemic inflammatory response syndrome, immunosuppressive therapy, immunocompromising conditions (e.g. diabetes, renal failure), BMI >40

Results:

— S. aureus was isolated from 527 (67%); MRSA was isolated from 388 (49%)

— intention-to-treat analysis 10 days after therapy: cure rate in clindamycin group was 83%, TMP/SMX group 82% (no statistical difference), but in the placebo group was 69%, significantly lower (p<0.001)

— For those who could be evaluated (those that completed the required study visits): 93% of clindamycin group, 93% of TMP/SMX group, and 81% of placebo were cured.

— children did slightly better than adults overall, especially in the clindamycin group

— For those without S. aureus, 90.5% on clindamycin, 90.8% on TMP/SMX , and 90.8% on placebo were cured (i.e. no benefit in non-S. aureus infections by antibiotics)

— for those with S. aureus (similar numbers for MRSA and MSSA), around 95% on clindamycin, 92% on TMP/SMX , and 70% on placebo were cured

— treatment failure was mostly because of a lesion at a different body site, or use of a rescue medication (done largely in the placebo group), but rarely due to worsening of the original lesion.

— at the one month follow-up visit:

–79% of the clindamycin group, 73% on TMP/SMX , and 63% on placebo remained cured.

–new infections at one month were less common in the clindamycin group (7%), than in the TMP/SMX group (14%), p=0.03, or the placebo group (13%), p=0.06

— adverse events were more common with clindamycin (22%) than with TMP/SMX (11%) or placebo (13%). All adverse events were without sequelae. One participant on TMP/SMX had a hypersensitivity reaction (fever, rash, thrombocytopenia, and hepatitis). Most common adverse events were diarrhea (16% clindamycin, 5% TMP/SMX, 7% placebo) and nausea (2%, 4%, 2%). No C difficile infections

Commentary:

— Skin abscesses are quite common, affecting 4% of people in the United States annually. Often these are treated as outpatients with clindamycin or TMP/SMX,  given the large percent of community MRSA

— In this study TMP/SMX was effective at a lower dose than often prescribed, though a 10-day course was given (vs 7 days). It is possible that the cure rates might have been higher with higher doses of TMP/SMX

— 13  patients had resistance to clindamycin and did not fare as well (54% cure vs 85% in clindamycin-susceptible infections). There were no cases of TMP/SMX resistance

— this study suggests that antibiotics help, though held-wisdom previously was that there was not much additional benefit after incision and drainage alone.

— there were minimal severe adverse reactions. Prior studies have found about 5% on TMP/SMX have severe reactions (and 1 person did above), and these can be fatal.

— for clindamycin, there was a meta-analysis (see Brown KA. Antimicrobial Agents and Chemotherapy 2013; 57: 2326) that found that, as compared to no antibiotic exposure, the Odds Ratio of C difficile infection for clindamycin was 16.80, fluoroquinolones 5.50, cephalosporins 5.68, macrolides 2.65, TMP/SMX 1.81

— it was mentioned in the supplementary materials of the current study that 33 in the placebo group (13%) used “rescue meds”, whereas 12 in clindamycin (5%) and 15 in TMP/SMX (6%)​ did. There is no comment on what meds were used or what the outcomes were for those who continued with their assigned meds/placebo and did not require rescue meds

so:

–it seems quite likely from this study that antibiotics help, as also noted in a prior blog , a study comparing TMP/SMX at 4-fold higher doses (320/1600 mg bid) finding benefit from the antibiotic but noting that >80% responded just to I&D.  And, 80+% of people seem to get better without antibiotics (in several other studies), and even in this study, 81% of those completing the study were cured. (70% of those with documented S aureus infections).

— there are really bad/occasionally lethal short-term potential adverse events from these antibiotics, especially severe systemic reactions to TMP/SMX and severe C difficile infections with clindamycin

–and there are potential long-term bad effects on the microbiome. As an example, this blog reviews a large prospective observational study finding antibiotic usage was associated with later development of colonic adenomas, including high-risk ones

–it was also notable in this study that there were not many cases of the abscess area getting worse in the placebo group with “treatment failure”

–so, in lower risk patients (nondiabetics, immunocompromise, etc), it might be reasonable just to watch the patient, holding the antibiotics but prescribing them if they were not getting better in a few days. I would be inclined to use antibiotics even in this lower-risk group if there were uncertainty about being able to have close followup (returning to clinic or phone followup), to assess the progress.

Primary Care Corner with Geoffrey Modest MD: Cellulitis treatment

25 May, 17 | by

by Dr Geoffrey Modest

 

Given the emergence of methicillin-resistant Staphylococcus aureus (MRSA), there are concerns about what empiric therapy to prescribe for skin infections, including cellulitis. A recent article in JAMA assessed the utility of adding trimethoprim-sulfamethoxazole (TMP-SMX) to cephalexin in treating uncomplicated cellulitis (see doi:10.1001/jama.2017.5653).

Details:

— 5 US emergency departments participated in an outpatient double-blind study of 500 patients >12 years old with cellulitis but without wound, purulent drainage, or abscess, seen from 2009-2012.

— Median age 40, 58% male, 57% white/35% black/1% Asian, symptom duration 3 days, 20% with a history of fever in the week prior to enrollment, 56% of infections were in the lower extremity/24% upper extremity/9% trunk abdomen or back/6% head or neck/4% groin or buttocks, 11% diabetics; mean length and width of erythema was 13 x 10 cm

— Bedside ultrasound was used to exclude abscess

— patients were randomized to cephalexin 500 mg 4 times a day plus TMP-SMX 160 mg/800 mg twice a day for 7 days, vs cephalexin plus placebo for 7 days

— primary outcome was clinical cure,  defined as an absence of fever, increase in erythema >25%, swelling, or tenderness at days 3-4; no decrease in erythema, swelling, or tenderness at days 8-10; and the presence of no more than minimal erythema, swelling, or tenderness at days 14-21.

Results:

— in a per-protocol analysis, which was limited to those patients who had a physical follow-up at 14-21 days after enrollment and took to at least 75% of medication doses: clinical cure at 14-21 days occurred in 182 (83.5%) of those assigned to cephalexin plus TMP-SMX, versus 165 (85.5%) in those on cephalexin alone, nonsignificant

— in the modified intention-to-treat population (participants took at least one dose of study medication, had an in-person or telephone assessment at the test of cure visit, and included those who withdrew from the trial or were lost to follow-up), clinical cure occurred in 189 of 248 patients (76.2%) in the combination group and 171 (69.0%) in the cephalexin group, a difference of 7.3% (-1.0% to 15.5%) p=0.07, almost but not quite significant. However in the more specific modified intention-to-treat analysis including those who took at least one dose of medications and had an in-person follow-up evaluation at any time during the study (ie, not including those who were lost to follow-up etc), the clinical cure rates were 83.8% in those on combined therapy and 82.8% of those with cephalexin alone, nonsignificant

— Adverse events, including the secondary outcome of overnight hospitalization, recurrent skin infections, and similar skin infections in household contacts through weeks 7-9, did not differ significantly. However, one patient on TMP-SMX did have acute-on-chronic kidney injury that resolved.

— 36 patients had treatment failure with cephalexin plus TMP-SMX: 10 (28%) were found to have an abscess the time of clinical failure and 9 (25%) developed an opening of the skin and purulent drainage

— 60 patients overall had treatment failure with clinical evidence of infection and had material available for culture: 41 (68%, and 10% of the per-protocol population) had MRSA, 8 (13%) had MSSA, and 3% streptococcal species, with no difference between treatment groups in the proportion having MRSA during follow-up.

— Post hoc subgroup analyses showed no difference between the groups if the patients had a history of fever or not, had diabetes, or by the size of the erythema.

Commentary:

— cellulitis is a common outpatient issue, and a difficult one because it is usually impossible to find the causative organism. b-hemolytic strep is often considered the cause, and the 2014 guidelines from the Infectious Diseases Society of America suggest choosing an antibiotic against Streptococci if there is no evidence of systemic signs of infection, penetrating trauma, evidence of MRSA elsewhere, or injection drug use. However, it is common for clinicians to cover MRSA infection in patients with cellulitis, given how widespread these infections are and how standard antibiotic therapy as with cephalosporins do not cover these MRSA infections.

— it is not so surprising that TMP/SMX does not add much to the treatment of cellulitis overall, since it does not provide much coverage for b-hemolytic strep, the presumed major causative organism

— One concern with this type of ED-based study is the higher likelihood of lower levels of medication adherence. They found that of the patients who took at least one dose of medications, only 52% were 100% adherent to the full regimen and 25% took 76-99% of their doses. This nonadherence was 3-fold higher in the cephalexin only group, for unclear reasons. But, the per-protocol analysis (ie those who took the meds) showed no difference between the outcomes of the treatment groups. I should add that some in this per-protocol group might have taken as little as 75% of their prescribed antibiotics, and this seems to me to be an arbitrary number. Which brings up the issue that some of these patients, in their most aggressively treated group, may actually have had insufficient antibiotic therapy. It would have been useful to have more granular data here assessing outcomes by finer gradations of medication adherence.

— Of note, of 36 patients who had treatment failure in the combined antibiotic group, over half had an abscess or skin opening/purulent discharge; and 71% of 28 in those on cephalexin alone. 10% of the patients who had clinical failure but had taken at least 75% of medication doses did have MRSA, which does suggest that even in patients with no clinical or ultrasound evidence of an abscess, there might well be MRSA (though, again, was this MRSA created or selected-for by taking insufficient quantities of antibiotics to cure the infection??) And this number is likely to be higher in many clinical settings, where cellulitis is defined exclusively clinically and without the use of ultrasound. It is somewhat reassuring that the treatment failures were similar in that both treatment groups had MRSA, though it seems that the numbers were too low to draw definitive conclusion.

–clearly from this study, there is a fine line between cellulitis and abscess formation. Even many of those who did not have an ultrasound-detectable abscess at the initiation of the study ultimately did develop fluid collections or skin opening with purulent discharge. And the proportion of patients with unknown fluid collections in our health center, for example, is undoubtedly higher than in this study since we do not have a bedside ultrasound machine (which limits the generalizability of this study in these settings). Again, it would have been interesting to have more granular data about the baseline characteristics of those who developed abscess/purulent discharge in this study and if there were any predictive models for them, since those who have abscesses are much more likely to have MRSA and should be treated differently. For one thing, those who are basically healthy (no immunocompromise, lots of comorbidities) who have no systemic symptoms and especially with small abscesses (eg <2cm) do just as well with incision and drainage and without antibiotics at all. And if antibiotics are indicated, they should cover MRSA.

 

so, this article, though not obviously generalizable to all settings (eg no ultrasound in many settings, perhaps higher medication adherence in primary care setting), does suggest reasonably strongly that TMP/SMX does not add much to the treatment of clinical cellulitis. Though imperfect, the per-protocol analysis does support this conclusion. Therefore, I think it is very reasonable to treat patients with cellulitis but without systemic symptoms/immunocompromise/etc just with a cephalosporin, thereby avoiding the unusual but occasionally severe adverse reactions of TMP/SMX, but with the caveat that there be close followup. Other studies have found that 90% of patients with cellulitis have significant clinical  improvement within 3 days, so that might be a reasonable target for a return visit. On the other hand, it seems reasonable to me to use the combo therapy in a patient who has a low probability for coming for follow-up, especially if one cannot rule-out a small abscess for lack of an ultrasound, where I would imagine that MRSA is more likely…

 

Primary Care Corner with Geoffrey Modest MD: Treatment of skin infections in era of MRSA

30 Mar, 15 | by EBM

By: Dr. Geoffrey Modest

A study done in 4 centers (Univ of Chicago, San Francisco General Hosp, Harbor-UCLA , and Vanderbilt Univ Med Ctr) looked at the efficacy of clindamycin vs trimethoprim-sulfamethoxazole (TMP-SMX) for uncomplicated skin infections (see N Engl J Med 2015;372:1093-1103​). The question was: which medication is preferred in the current era of community-acquired methicillin-resistant Staph aureus (MRSA), which seems to be extremely common around the country?

Untitled

Details:

–524 patients, including 155 children. 30.5% with abscess (>5cm, in adults), 53.4% with cellulitis, 15.6% with both; the patients were 52.3% male, 53.2% Black, 40.3% White, 28.6% Hispanic. Mean age 27.1. 29.6% children.

–patients were randomized to clindamycin (adults at 300mg tid) or TMP-SMX (on double-strength tablet bid), all for 10 days. Pediatric doses adjusted by body weight

— of those with positive cultures (n=277), 217 had s. aureus [167 with MRSA, 77.0% of the staph infections, with 21 (12.4%) resistant to clinda and 1 resistant to TMP-SMX; 52 were methicillin sensitive]; 32 were strep of different varieties; 10 were proteus, 38 coagulase-negative staph, 15 diphteroids, and a smattering of others. Note: all of the cultures were from those with abscesses, not cellulitis (cellulitis being 53.4% of the skin infections)

–no difference in outcomes between these medications: 80.3% were cured with clindamycin, 77.7% with TMP-SMX in intention-to-treat analysis, but in the 466 evaluable patients, it was 89.5% with clindamycin and 88.2% with TMP-SMX.

–no difference in children vs adults, in those with abscesses vs cellulitis. also no difference in subgroups infected with s. aureus, MRSA, or MSSA. of the 15 patients with clindamycin-resistant staph, 11 were cured (73.3%) vs 91.7% of those sensitive to clinda

–adverse events: similar: 18.9% with TMP-SMX​  and 18.6% with clindamycin, with both antibiotics associated with diarrhea in about 10%, nausea 2.5%, pruritus in 1.5%, rash in 1%. no cases of clindamycin-associated c. diff infections.

So, a few points:

–It is pretty remarkable how well TMP-SMX did, since a reasonable percentage of the patients had strep which is felt not to be sensitive to TMP-SMX. And, it is generally held that cellulitis is much more likely than abscesses to be caused by strep (though we cannot really culture cellulitis), yet the cure rate with TMP-SMX was the same for cellulitis and abscesses. there is some literature suggesting that the way sensitivity testing is done may underestimate TMP-SMX sensitivity. [As a general point, agar-plate antibiotic resistance is not always an accurate reflection of what happens in the body. For example, many organisms causing urinary tract infections seemingly resistant to antibiotics may in fact respond, perhaps related to the high concentration of antibiotics in the urine]

–Several studies have found that antibiotics do not add much to the primary treatment of abscesses (which is: incision and drainage, I&D), so the high cure rate with any antibiotic may not be surprising. So, for example, 73.3% of those with clindamycin-resistant staph in the above study “responded” to antibiotics, but these bacterial isolates were from abscesses and may not have needed antibiotics. But I should add that the literature on this is really all over the place. Some studies suggest that abscesses> 5cm (as in the above study) do better with antibiotics in addition to I&D. Some find that MRSA infections in particular respond better when antibiotics are added. but there are studies to the contrary.

–There have been studies finding that cephalosporins or other b-lactam antibiotics with anti-strep activity work somewhat better than TMP-SMX for skin infections, though given the very high prevalence of MRSA that we find at our health center, we have been mostly using TMP-SMX as the primary agent and with good results​ (again, we only culture those with abscesses). I had a patient with morbid obesity and diabetes a few years ago who had a very large inner thigh abscess and surrounding cellulitis from documented MRSA, sent home from the hospital on linezolid, but I was unable to get the required prior approval and switched him to TMP-SMX​, and he had a great result… In general, we do usually add antibiotics for skin infections because of the articles suggesting benefit in MRSA, and there was even an article suggesting less likely recurrences if use TMP-SMX​.

Note: I have several other articles in the BMJ online blogs on MRSA, including the use of bleach baths, the new Infectious Disease Society guidelines on treatment of skin infections, and skin abscess treatment. See here. ​

Primary Care Corner with Geoffrey Modest MD: Choosing wisely — infectious disease society recommendations

3 Mar, 15 | by EBM

By: Dr. Geoffrey Modest

Will pass along the infectious disease society “choosing-wisely” recommendations for decreasing antibiotic use. Although none of these are new or surprising, data suggest that antibiotics are still being prescribed for these conditions unwisely….  (see here)

  1. Don’t treat asymptomatic bacteruria with antibiotics. (except pregnant patients, those undergoing invasive urological surgery including prostate surgery, or those within 1 year of kidney or kidney pancreas transplant)
  2. Avoid antibiotics for upper respiratory infections. most are viral. But one should treat group A strep and pertussis
  3. Don’t use antibiotics for stasis dermatitis of lower extremities. Use leg elevation and compression. [in my experience, this can be a difficult call: stasis dermatitis can really look like cellulitis with bright red, well-demarcated erythema, though with less induration than cellulitis. And i would add that topical steroids do work quickly with stasis dermatitis]
  4. Don’t test for clostridium difficile infection in the absence of diarrhea. Except if ileus from c. difficile is suspected. In general​, c. diff carriage should not be treated so shouldn’t be looked for
  5. Don’t use prophylactic antibiotics for treatment of mitral valve prolapse as a means to prevent endocarditis.

So, just a reminder.

Primary Care Corner with Geoffrey Modest MD: Soft Tissue Infection Guidelines

7 Oct, 14 | by EBM

​The Infectious Diseases Society of America just updated their 2005 guidelines for treatment of skin and soft tissue infections (see DOI: 10.1093/cid/ciu296). The guideline deals with minor infections and up to life threatening ones, but I will focus on ones seen/treated in primary care (there is also an algorithm for wound infections, which I will leave to you to investigate).

-Mild nonpurulent infections (cellulitis, erysipelas): Where mild infection is defined as skin infection without systemic signs of infection (>38 deg C, tachycardia >90, tachypnea >24,or WBC >12K or <400, or immunocompromized):

–Blood culture/biopsies etc. only if patient is immunocompromized (and these patients should be admitted/get IV antibiotics)

–Should use antibiotic with anti-strep activity for 5 days, then extend if necessary after further evaluation. They do note that many clinicians (which includes me) like to cover methicillin-sensitive staph (MSSA). Also, consider covering methicillin-resistant (MRSA) if severe infection, nasal colonization with MRSA, injection drug use.

–In lower extremity cellulitis, examine interdigital toe spaces to look for fissuring, scaling, maceration which could lead to recurrent cellulitis  (I’ve had a couple of patients with recurrent lower extremity cellulitis and bad fungal infections of toenails or interdigitally, who did not have further cellultitis when those were treated. I would also add that patients with venous insufficiency and recurrent cellulitis seem to do better with compression stockings.) Consider prophylactic antibiotics in patients with recurrent infections (3-4 episodes/yr) , e.g. with oral penicillin or erythromycin for 4-52 weeks or benzathine penicillin IM 2.4M units ​every 2-4 weeks.

–Dog/cat bites — give preemptive therapy for 3-5 days in those with more severe bites or immunocompromized (they note that patients with relatively minor dog bites, not involving the face, hand, or foot found a pretty low incidence of infection — 16% — and may not justify routine antibiotic administration, esp if there is good followup available.  Give amox-clavulanate 875/125 bid. for human bites, always give antibiotics). Give Td or Tdap if not given within past 10 years, consider rabies prophylaxis, do not generally close wounds except on face, and give azithro if concerned about cat scratch disease.

–In terms of general treatment, MRSA is unusual cause of cellulitis (study in cellulitis patients at a medical center with high incidence of other MRSA-related skin infections found that cefazolin or oxacillin was successful in 96% of the patients. Another recent study not referenced in this article found greater efficacy of cephalexin to TMP/SMX,  and, I would add, some of the agents used to treat MRSA, esp TMP-SMX and doxycycline, are less active against strep).

–Antibiotic recommendations: pen VK (I do not use this since by inspection cannot rule-out staph infection), cephalosporin, dicloxacillin, or clindamycin orally — see doses under impetigo/ecthyma

–Impetigo/ecthyma (ecthyma is deeper infection, lesions usually begin as vesicles which rupture, then get circular erythematous ulcer with adherent crusts, and typically leaves a scar

–Gram stain and culture pus or exudates to see if staph or strep, but treatment without this is reasonable in typical cases

–Bullous or nonbullous impetigo: can use oral therapy or topical, though oral therapy preferred if multiple lesions

–Therapies: topical — use either mupirocin or retapamulin bid for 5 days; oral — 7 days of therapy active against staph (unless culture shows strep alone), with MSSA agent (dicloxacillin 250 qid,  cephalexin 250 qid, though I usually use 500 bid with good effect, amox-clav 875/125 bid), or if MRSA suspected can use doxycycline 100 bid , clindamycin 300-400 qid, or TMP/SMX 1-2 DS tabs bid.

–Purulent skin infections/abscesses

–Gram stain and culture are recommended (though not for inflamed epidermoid cysts).

–I&D is recommended for inflamed epidermoid cysts, and abscesses (including carbuncles, large furuncles).

–Use of antibiotics should be based on presence or absence of systemic inflammatory response (T>38C or <36C, tachypnea>24, tachycardia >90, WBC>12000 or <400)

–Antibiotic for MRSA is recommended in those who fail initial antibiotic treatment or have impaired host defenses. Also for those with systemic symptoms as above.

–For those with recurrent abscesses, look for local causes (eg pilonidal cyst, hidradenitis or foreign body), drain and culture, then treat with 5 to 10 days of an active antibiotic. Consider 5-day decolonization regimen (e.g., intranasal mupirocin, daily chlorhexidene washes, daily decontamination of personal items) and evaluate for neutrophil disorders if recurrent abscesses began in childhood. They do mention bleach baths (1/4-1/2 cup of bleach per full bath) — see here for a previous blog that promots bleach baths and I have had a few people email me with very positive stories. Data is not great for the 5-day decolonization regimens they cite. I would also add that I have seen a patient with apparent recurrent abscesses on his hands, which turned out to be a herpetic whitlow.

​–Choice of antibiotics for empiric therapy: TMP/SMX 1-2 DS tabs bid or doxycycline/minocycline 100mg bid. For culture-guided therapy: dicloxacillin 500 qid or cephalexin 500 qid (they did not include clindamycin in the empiric therapy. Not sure why. I have certainly had much success with that and it covers strep if needed.)

Geoff

Primary Care Corner with Geoffrey Modest MD: Bleach baths to decrease recurrent skin infections

2 Apr, 14 | by EBM

1000 healthy kids aged 3 months to 18 yrs with probable community-associated staph aureus skin/soft tissue (SSTI) or invasive infection randomized to daily hygiene vs that with 2x/week bleach baths for 3 months (see DOI: 10.1093/cid/cit764). basically,

–recurrence of SSTI common: about 50%
–bleach bath consisted of adding 5ml of bleach (regular bleach, 6.0% hypochlorite) to every gallon of bath water, and bathing in that for 15 min 2x/week, for 3 months. 12-month followup. dilute bleach solutions known to kill staph.
–colonization cultures were obtained from nares, pharynx, groin. 56% were colonized with s. aureus at minimum of 1 site (most common = groin in 38%, nares 22%, throat 17%). MRSA (methicillin-resistant) more common in groin and throat, MSSA (methicillin-sensitive) in nose. more colonization in younger ages, esp <2yo
–rate of “medically-attended” recurrent infection: 17% with bleach bath and 20.9% with regular hygiene (not significant, but arguably too small a trial: needed around 1000 kids to detect 50% reduction with 90% power). no diff between MRSA and MSSA infections (though most infections were MRSA). higher rates of infection with more colonization sites culture-positive
–not adverse effects found, other than dry skin in a few kids and burning eyes in 1 patient only.

 so, obviously a small study at least in terms of outcomes, only with kids, short-term (3 months of baths, with 12 month follow-up) and not powered to get significant results. but, besides that, pretty intriguing… recurrent staph infections really common in kids and adults. seems like a pretty benign therapy (esp given the alternatives of recurrent courses of antibiotics, need for frequent ER visits, etc — ie alternatives not great). and by my quick and dirty (?) measurements in my bathtub, 6″deep water would require 4 ounces of bleach. so, might be reasonable to try in people with documented recurrent infections???? i checked out the Am Acad of Dermatology website for hidradenitis, and they suggested bleach bath as one approach (1/2 cup non-scented bleach to 1/2 full bathtub of water), noting that it works sometimes.

geoff

Primary Care Corner with Geoffrey Modest MD: Skin Abscesses Treatment

25 Mar, 14 | by EBM

review article in new england journal last week on management of skin abscesses in era of methicillin-resistant staph aureaus MRSA (see DOI: 10.1056/NEJMra1212788). both the incidence of skin abscesses overall and the % of MRSA have increased over time. a few comments:

–diagnostic accuracy is not great: eg, a study of 126 adults with cellulitis where ER MD felt abscess not evident, ultrasound found abscess in 50%
–treatment of abscess is primarily I&D
–there may be more rapid healing if the I&D incision is closed vs leaving it open (studies mostly in the anogenital area, showing half the healing time and no diff in recurrences). should consider primary closure if incision >2cm. [goes against conventional wisdom that needs to be open to continue draining]
–no data as to whether to irrigate the wound, and data on whether packing helps is unclear (a couple of very small studies done, one in adults showing more pain but no outcome difference, one in kids found more frequent subsequent drainage and antibiotic treatment in those not packed)
–antibiotics. in 2008, 63% of abscesses were from community-associated MRSA. 15% in MSSA, 2% b-hemolytic strep, 20% other. but cure rates for just I&D alone are in the 85% range. a study in kids found no diff if give tmp/smx vs placebo after I&D, though some decrease in new lesion development. so, Infectious Diseases Society of America recommends systemic antibiotics for patients with extensive disease (multiple sites), rapidly progressive dz, signs/symptoms of systemic illness, immunosuppression, very young or old, abscess in difficult area to drain, associated septic phlebitis, or drained abscess not responding just to I&D.
–empirical antibiotic therapy when chosen should cover MRSA, ie first choice of tmp/smx 1-2 DS tabs bid. some resistance to clinda and tetras, but can do clindamycin 300-450 tid, doxycylcine 100 bid or minocycline 200, then 100 q12h.
–if cellulitis alone, more likely to be strep (difficult to really know the organism if just cellulitis, though), and TMP/SMX and tetracyclines less active. clinda may be better choice. and my experience is that TMP/SMX, which has limited activity against strep, typically works well with cellulitis (though i never do ultrasound to rule-out small abscess…). if severe cellulitis, might cover with TMP/SMX plus cephalexin. there are no great data for these suggestions from clinical trials, and some trials are currently ongoing.

so, this brings up a few issues. even though it is commonly incorrect to conclude that an abscess is not present without the aid of an ultrasound, those of us in the community cannot typically get an ultrasound easily. unless the patient has severe infection needing hospitalization, we treat them by I&D if there is an evident abscess present, will occasionally needle it if not sure (though sometimes purulent collections can be quite viscous and can be missed with a needle), and (probably more often than is necessary) prescribe antibiotics. my experience is that small abscesses/collections often resorb with heat and antibiotics without I&D.

geoff

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