The Role of Anaerobic Bacteria in Cutaneous and Soft Tissue Abscesses and Infected Cysts

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Anaerobe 13 (2007) 171–177 www.elsevier.com/locate/anaerobe Mini-review The role of anaerobic bacteria in cutaneous and soft tissue abscesses and infected cysts

Itzhak BrookÃ

Schools of Medicine, Georgetown University, 4431 Albemarle Street NW, Washington, DC 20016, USA

Received 12 August 2007; accepted 18 August 2007 Available online 6 September 2007

Abstract

This review presents the aerobic and anaerobic microbiological aspects and management of cutaneous and soft tissue abscesses, paronychia, anorectal, pilonidal, and perirectal abscesses, infected epidermal cysts, hidradenitis suppurativa, and pustular acne lesions. These infections often occur in different body sites or in areas that have been compromised or injured by foreign body, trauma, ischemia, malignancy or surgery. In addition to group A beta-hemolytic streptococci and Staphylococcus aureus, the indigenous aerobic and anaerobic cutaneous and mucous membranes local microﬂora usually is responsible for these generally polymicrobial infections. These infections may occasionally lead to serious potentially life-threatening local and systemic complications. The infections can progress rapidly and early recognition and proper medical and surgical management is the cornerstone of therapy. r 2007 Elsevier Ltd. All rights reserved.

Keywords: Abscess; Cyst; Staphylococcus aureus; Anaerobes

Cutaneous and soft tissue abscesses and infected cysts pilonidal abscess, perirectal abscess, infected epidermal infections are among the most common infections, and cysts, hidradenitis suppurativa, and pustular acne lesions. may sometimes lead to serious local and systemic complications. These infections can be potentially life- 1. Cutaneous abscesses threatening infections that may have rapid progress. Their early recognition and proper medical and surgical manage- Subcutaneous and cutaneous abscesses can be caused by ment is therefore of primary importance. polymicrobial aerobic and anaerobic bacteria. Although In addition to group A beta-hemolytic streptococci the primary management of these infections is usually Staphylococcus aureus (GABHS) and , the indigenous through surgical drainage, knowledge of their microbio- aerobic and anaerobic cutaneous and mucous membranes logy allows institution of empiric antimicrobial therapy local microﬂora usually is often responsible for polymi- prior to the availability of culture results. crobial infections. Anaerobic infections of the skin and soft tissue frequently occur in areas of the body that have been compromised or injured by foreign body, trauma, ische- 1.1. Microbiology mia, malignancy or surgery. Because the indigenous local microﬂora usually is responsible for these infections, The commonest organisms involved in skin and soft anatomic sites that are subject to fecal or oral contamina- tissue infections are S. aureus and GABHS [1]. They tion are particularly at risk (Fig. 1). frequently cause impetigo, furunculosis, cellulitis, and This review summarizes the aerobic and anaerobic wound infections [2]. Recently, many of the S. aureus microbiological aspects and management of cutaneous isolates are methicillin resistant. Gram-negative enteric and soft tissue abscesses, paronychia, anorectal abscess, bacteria (i.e. Enterobacter spp., and Escherichia coli) are also recovered occasionally. ÃTel.: +1 202 363 4253; fax: +1 202 244 6809. The predominant anaerobes are Gram-positive cocci, E-mail address: [email protected] Gram-negative bacilli (including Bacteroides fragilis group

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infection. Under appropriate conditions of lowered tissue resistance, almost any of the common bacteria can initiate an infectious process. Cultures obtained from abscesses frequently contain several bacterial species, and as might be expected, the organisms found most frequently are the ‘‘normal flora’’ of these regions (Fig. 1). Aspirates obtained from abscesses of the perineal and rectal area tend to yield organisms found in stool, and those obtained from oral regions generally harbor mouth flora. Conversely, pus recovered from abscesses in areas remote from the rectum or mouth contains primarily constituents of the microflora indigenous to the skin [2–4].

1.3. Diagnosis

Redness, tenderness, heat, and swelling are characteristic of skin and subcutaneous tissues infections. Associating lymphangitis is characterized by the presence of reddish Fig. 1. Distribution of organisms in abscesses, wound, burns and streaks extending proximally and associated with tender decubitus ulcers. enlargement of regional lymph nodes. Systemic symptoms can be mild, and include fever, and malaise. Fluctuation in the abscess indicates that it is ready for drainage. and, Prevotella and Porphyromonas spp.), and Fusobacter- Laboratory findings include leukocytosis, rapid sedimenta- ium spp. [1–3]. Anaerobes predominate in infections of the tion rate, and often positive blood cultures. Some organ- vulvovaginal, buttocks, perirectal, finger, and head areas. isms can cause bacteremia more frequently, and Aerobic bacteria are prevalent in the neck, hand, leg, and manipulation including surgical incision of the abscess trunk areas. Many of these infections are polymicrobial. may be followed by transient bacteremia. S. aureus, the most prevalent aerobe, is found whenever Pus or material recovered by aspiration or incision abscesses originate from skin surface. It is, recovered should be Gram stained and cultured for both aerobic and however, less often from the buttocks, perirectal, and anaerobic bacteria as well as fungi. vulvovaginal areas. The infections at these latter sites Radiological studies may reveal localized collections generally originate from adjacent mucous membranes of pus when free gas is present or when abnormal rather than skin. Among Gram-negative aerobes, Entero- tissue density is observed. Ultrasound, computed tomo- bacter spp. are recovered mostly from the trunk and legs, graphy (CT), angiography, and radionuclide scans may be while E. coli is recovered mainly from the vulvovaginal, helpful [5]. buttocks, and perirectal areas. Peptostreptococcus spp. which are normal skin inhabi- 1.4. Management tants and part of the endogenous gastrointestinal flora [4], are also recovered from infections at all sites. B. fragilis Surgical drainage is the treatment of choice. Although group, which predominate in the feces, are cultured most antimicrobials may prevent suppuration if given early or frequently from abscesses of the perirectal area. Pigmented prevent spread of an existing abscess, they are not an Prevotella and Porphyromonas spp., which occurs in stools adequate substitute for surgical evacuation. Heat applica- as well as in the oral cavity [2,4], are isolated from tion can relieve the pain and facilitate suppuration and infections proximal to these sites and from the head and liquefaction. neck. Most strains of B. fragilis group and many of Some antimicrobials can be partially inactivated by pus Prevotella Porphynomonas and Fusobacterium spp. are and by low pH (aminoglycosides and quinolones). The resistant to penicillins. Beta-lactamase-producing bacteria activity of some antibiotics that are effective against (BLPB) are recovered in about half of the abscesses. multiplying organisms (i.e. beta-lactams) is impaired by the failure of bacteria to multiply in pus. Furthermore, 1.2. Pathogenesis phagocytosis is reduced in the abscess cavity. Because of the combination of these factors, many abscesses are Factors predisposing to abscess formation include resistant to antimicrobial therapy. obstruction of drainage, ischemia, chemical irritation, Because anaerobic bacteria frequently are associated hematoma formation, accumulation of fluid, foreign with cutaneous abscesses, especially in areas adjacent to bodies, trauma, and stasis in the vascular system. mucosal membranes, their presence should be anticipated The site of the abscess is of paramount importance in the if antimicrobial therapy is given. Appropriate antimicro- selection of the organism(s) that may be cause the bials include clindamycin, metronidazole, cefoxitin, a Author's personal copy

ARTICLE IN PRESS I. Brook / Anaerobe 13 (2007) 171–177 173 carbapenem (e.g. imipenem, meropenem, ertapenem), or a methodology for cultivation of both aerobic and anaerobic combination of a beta-lactamase inhibitor (i.e. clavulanic organisms in such infections, anaerobic organisms were acid, tazobactam) and a penicillin (i.e. amoxicillin, recovered from about half of the patients studied [8]. ticarcillin, piperacillin). If staphylococcal infection is Acute paronychia usually results from a trauma, which suspected, or when no initial clue for etiology is available, breaks down the physical barrier between the nail bed and a penicillinase-resistant penicillin (e.g., oxacillin) is given. the nail; this disruption allows the introduction of Macrolides or vancomycin can be administered to peni- pathogens. Activities, such as nail biting, finger sucking, cillin allergic individuals, and an aminoglycoside, or manicuring, or artificial nail placement can also induce quinolone, or a fourth generation cephalosporin (i.e., such trauma. ceftazidime, cefepime) can be given when Gram-negative Chronic paronychia often occurs in individuals whose aerobic bacilli are suspected. Recently, there has been an hands are repeatedly exposed to moisture or have increase in the recovery of methicillin resistant S. aureus prolonged and repeated contact with irritants or chemicals. (MRSA). Patients with serious infections where S. aureus is Especially susceptible are housekeepers, dishwashers, suspected should therefore be initially given agents active bartenders, and swimmers. against MRSA until susceptibility results are available. These include vancomycin, daptomycin, linezolid, quinu- 2.2. Diagnosis pristin/dalfopristin and tigecycline. Acute paronychia is manifested by erythema, edema, 1.5. Complications fever, and tenderness. There is less erythema in chronic paronychia, with is characterized by a cushion like Locally or systemically spread of the infection may thickening of the paronychial tissue. The nail plates can occur. Local spread generally follows the path of least be thickened and discolored, with pronounced transverse resistance along fascial planes. Lymphatic spread may lead ridges. to lymphangitis, lymphadenitis, or bubo. Involvement of This infection generally starts as a subcuticular or veins may lead to infective thrombophlebitis, bacteremia, intracutaneous infection with local exudate which even- septic embolization, and systemic dissemination. tually spreads under the fingernail base. Infection may follow the nail margin or extend beneath the nail and 2. Paronychia suppurate. Rarely, it can penetrate deep into the finger, causing tendon necrosis, and osteomyelitis. The chronically Paronychia is an inflammation of the structure sur- infected nail eventually becomes distorted. rounding the nails. Whether acute or chronic, paronychia Bacterial culture for aerobic and anaerobic bacteria is results from a breakdown of the protective barrier between indicated especially when the exudate is purulent. A the nail and the nail fold. The introduction of organisms microscopic examination in potassium hydroxide and into the moist nail crevice results in the bacterial or fungal culture for Candida and dermatophytes are also indicated. (yeast or mold) colonization of the area. It is common in A large amount of budding yeast on potassium hydroxide housewives, cleaners, nurses, children who suck their examination suggests that Candida may be of etiologic fingers, or those who often have their hands in water [6]. significance. A positive culture for Candida in the absence Paronychia occurs more common in women than in men, of a positive potassium hydroxide examination and clinical with a female-to-male ratio of 3:1. signs suggestive of candidiasis may indicate that the organism is a nonpathogen. 2.1. Microbiology and pathogenesis 2.3. Management The bacteriology of paronychia is polymicrobial due to aerobic and anaerobic bacteria in about three fourth of the An acute infection is best treated with hot compresses or cases. The predominant aerobic organisms are S. aureus, soaks of the affected finger 3–4 times per day and an Streptococcus spp., Eikenella corrodens, GABHS, Klebsiella appropriate systemic antibiotic. If the infection does not pneumoniae, Proteus spp., P. aeruginosa, and Candida resolve or progresses to an abscess, it should be drained albicans The predominant anaerobic bacteria are Gram- promptly. A purulent pocket should be opened cautiously negative bacilli of oral origin (Prevotella and Porphyromo- with a scalpel. Infection extending along the tendon nas), Fusobacterium,andPeptostreptococcus spp. BLPB are sheaths requires prompt surgical incision and drainage. present in about half of the patients [7]. The initial treatment of chronic paronychia consists of The anaerobic organisms isolated are generally part of the avoidance of inciting factors such as exposure to moist normal oropharyngeal flora that are self-inoculated environments or skin irritants. Proper recovery is facili- through nail biting and finger sucking from the patient’s tated by keeping the affected lesion dry. Choice of footgear own mouth flora onto the finger. This phenomenon is for infection of the toes may also be considered. Mild cases parallel to the acquisition of infection following human of chronic paronychia can be treated with warm soaks. bites and clenched fist injuries. In studies that applied Chronic paronychia caused by dermatophytes that are Author's personal copy

ARTICLE IN PRESS 174 I. Brook / Anaerobe 13 (2007) 171–177 sensitive to griseofulvin generally respond to treatment sphincteric space and then spreads along adjacent potential with this agent. If Candida is present, nystatin or spaces. The abscess is often initiated as a result of diarrhea amphotericin-B lotion should be used, and occasionally or constipated that abrade the anal canal causing destruc- either may be incorporated with the steroid. Oral therapy tion of the normal mucosal barrier, allowing bacteria to with antifungal agents (e.g. Ketoconazole) is useful if invade perianal tissues and anal glands. The invading topical therapy failed [6]. bacteria may be of stool or skin origin. When untreated, Treatment effective against anaerobes of oral origin is the abscess may burrow along the rectal sphincter, exiting generally necessary. When S. aureus is suspected, penicillin next to the anus on the buttock, forming a fistula-in-ano. and a penicillinase-resistant penicillin should be used. Alternatively, it may burrow through the musculature of Linezolid or vancomycin are indicated for MRSA. The the perirectal ring into the deeper tissues, forming an combination of a penicillin (i.e. amoxicillin, ticarcillin) and ischiorectal abscess. Predisposing condition include ulcera- a beta-lactamase inhibitor (i.e. clavulanic acid) is effective. tive colitis, primary or secondary neutropenia. First-generation cephalosporins are not as effective as the above combination because of the resistance of some 3.3. Diagnosis anaerobic bacteria and E. corrodens. Cefoxitin or the combination of a penicillin and a beta-lactamase inhibitor The clinical presentation correlates with the abscess are effective parenteral agents. anatomical location. Patients with perianal abscesses often E. corrodens, has unique susceptibility: it is susceptible to complain of dull perianal discomfort and pruritus. The penicillin, ampicillin, azithromycin and the fluoroquino- pain often is exacerbated by movement and increased lones but resistant to oxacillin, methicillin, nafcillin, and perineal pressure from sitting or defecation. Physical clindamycin, and occasionally resistant to cephalosporins. examination demonstrates a small, erythematous, well- Avoidance of water, detergents, and chemicals, and dry defined, fluctuant, subcutaneous mass near the anal orifice. their fingernail areas after washing can prevent recurrences Ischiorectal abscesses typically present with systemic and facilitate recovery. Sucking of fingers or nail biting fevers, chills, and severe perirectal pain and fullness should be avoided. consistent with the more advanced nature of this process. External signs are minimal and may include erythema, 3. Anorectal abscess induration, or fluctuance. On rectal examination, a fluctuant indurated mass can be encountered. The classic locations of anorectal abscesses are: perianal Intersphincteric abscesses are sometimes difficult to (60% of all), ischiorectal (20%), intersphincteric (5%), diagnose and present with rectal pain and localized supralevator (4%), and submucosal (1%). Perianal abscess tenderness on examination. Suspicion of an intersphinc- is an infection of the soft tissues surrounding the anal teric or supralevator abscess may require confirmation by canal, with formation of a discrete abscess cavity. The CT scan, magnetic resonance imaging (MRI), or anal severity and depth of the abscess vary, and the abscess ultrasonography. cavity is often associated with formation of a fistulous tract. The peak incidence of the abscesses is in the third to 3.4. Management fourth decades of life and is more common in men than women. However, perianal abscess also occurs in infants. Drainage is the mainstay of therapy. The abscess should be incised to prevent spread of the infection. Fistulous 3.1. Microbiology tracts must be opened and excised. Gram stain and cultures should be done. Administration of antimicrobials effective The infection is generally polymicrobial due to aerobic against anaerobic bacteria and enteric Gram-negative rods and anaerobic bacteria. The predominant anaerobes are is generally essential especially in the presence of a systemic Gram-negative bacilli (including B. fragilis group and inflammatory response, diabetes, or immunosuppression. pigmented Prevotella and Porphyromonas spp.), Gram- The antimicrobials effective against anaerobes include: positive anaerobic cocci, Fusobacterium and Clostridium clindamycin, cefoxitin, chloramphenicol, or metronidazole. spp. The predominant facultatives and aerobes are E. coli, An aminoglycoside, a quinolone or third-generation S. aureus, GABHS, P. aeruginosa, and Proteus morganii cephalosporins provide coverage for Gram-negative enteric [9,10]. rods. Single-agent therapy with cefoxitin, a carbapenem or the combination of a penicillin (such as ampicillin or 3.2. Pathogenesis ticarcillin) and a beta-lactamase inhibitor (such as sulbac- tam or clavulanic acid) may be adequate. Perirectal abscesses and fistulas are anorectal disorders arising mostly from the obstruction of anal crypts. 3.5. Complications Infection of the static glandular secretions results in suppuration and abscess formation within the anal gland. Complications include septicemia, anorectal fistulas, The abscess is usually formed initially within the inter- anal gangrene, and abscess recurrence. Author's personal copy

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4. Pilonidal abscess S. aureus is the predominant isolate in infections in the trunk and extremities, but anaerobes are frequently Pilonidal sinus is a cyst which is a small midline closure isolated in cyst abscesses in rectal, vulvovaginal, head, defect that can collect debris and subsequent become and scrotal areas. inflamed. When it communicates with the subarachnoid space it serves as a route of bacterial entry into the central 5.2. Management nervous system. It occurs more common in males than in females. Surgical drainage is the treatment of choice for an epidermal cyst abscess. However, recurrences are frequent 4.1. Microbiology and pathogenesis because the keratin producing lining of the cyst is not removed. Administration of systemic antimicrobials may The infection is generally polymicrobial due to enteric be indicated in selected cases, especially in immunocom- facultative aerobic and anaerobic bacteria. Anaerobic promised patients or in instances where local or systemic isolates can outnumber aerobes at a ratio of 5:1 [11]. The spread of the infection has occurred. predominant anaerobic organisms were Gram-negative Antimicrobial treatment of mixed infections requires the bacilli (including B. fragilis group and pigmented Pre- administration of antimicrobials effective against both votella and Porphyromonas spp.), Gram-positive anaerobic aerobic and anaerobic bacterial components of the infec- cocci, Fusobacterium spp., and Clostridium spp. The main tion. Antimicrobials that provide coverage for S. aureus as aerobic organisms are E. coli, Enterococcus spp., Proteus well as the anaerobic bacteria include cefoxitin, clindamy- spp., and Pseudomonas spp. cin, a carbapenem, and the combination of beta-lactamase inhibitors and a penicillin. A combination of metronida- 4.2. Diagnosis and management zole and a beta-lactamase-resistant penicillin can be an alternative. Coverage against MRSA is discussed at the Physical findings depend on the stage of disease. In the section on cutaneous abscesses. early stages a sinus tract or pit is present in the sacrococcygeal area which can progress to midline edema or abscess. Examination of the abscess may reveal 6. Hidradenitis suppurativa tenderness, fluctuance, warmth, purulent discharge, induration and cellulitis. Fever and other systemic signs of Hidradenitis suppurativa (HS) is a recurrent inflamma- infection are uncommon. tion of the apocrine sweat glands, particularly those of the Surgical drainage is the therapy of choice. However, axilla, genital, and perianal areas. It can result in antimicrobial therapy is also needed. The antimicrobial obstruction and rupture of the ducts and the development choices are similar to the one for perirectal abscess. of a secondary infection. The lesions generally drain spontaneously, with formation of multiple sinus tracts 4.3. Complications and with hypertrophic scarring. Although not initially infected, the lesions frequently become secondarily in- Complications include recurrence, abscess formation, fected. Often, patients with HS also are afflicted with acne, systemic infection, squamous cell and verrucous carcinoma. pilonidal cysts, and chronic scalp folliculitis; thus, which is termed follicular occlusion tetrad. 5. Infected epidermal cysts 6.1. Microbiology and pathogenesis Epidermal cysts are closed sacs with a definite wall that result from proliferation of surface epidermal cells. The infection is generally polymicrobial due mainly to Production of keratin and lack of communication with aerobic and anaerobic bacteria of skin and proximal the surface are responsible for cyst formation. Epidermal mucous membranes origin. Anaerobic bacteria alone or cysts can become infected, and an abscess can develop. in combination with aerobic organisms can be isolated from about two-thirds of patients. The most frequently 5.1. Microbiology aerobic bacteria are S. aureus (isolated from about a third of cases), GABHS, micro-aerophilic streptococci, and The organisms causing most epidermal cyst infections P. aeruginosa. The predominant isolated anaerobes are are S. aureus, GABHS, E. coli and aerobic and anaerobic Peptostreptococcus, Prevotella, Fusobacterium and Bacter- bacteria that originate from the normal flora adjacent to oides spp. [13,14]. the site of the cyst infection. Anaerobes are isolated in The anaerobes isolated from the patients depend on the about half of the patients. The predominant anaerobic site of the infection and are part of the flora of the organisms are Peptostreptococcus spp. and Gram-negative oropharynx (Prevotella spp., Fusobacterium spp., Peptos- bacilli (including 12 pigmented Prevotella and Porphyr- treptococcus spp. and microaerophilic streptococci), gas- omonas spp. and B. fragilis group) [12]. trointestinal tract (Bacteroides spp., Peptostreptococcus Author's personal copy

ARTICLE IN PRESS 176 I. Brook / Anaerobe 13 (2007) 171–177 spp.) [4] and skin (Peptostreptococcus spp.) and presumably 7. Pustular acne lesions reached the HS lesions from these sites. Acne vulgaris, a disorder of the pilosebaceous apparatus, is the most common skin disorder of the second and third 6.2. Diagnosis decades of life. The primary lesions are reddish-purple nodules that 7.1. Microbiology and pathogenesis gradually become fluctuant and drain. Irregular sinus tracts with repeated crops of lesions are formed, and Bacterial factors are important in the pathogenesis of reparative processes are only partially successful. The acne. Acne is believed to be associated and perhaps even involved areas show a mixture of burrowing, draining caused by Propionibacterium acnes [15]. The improvement tracts, and ciccatricial scarring. In some cases, HI is in acne patients treated with systemic antibiotics effective associated with acne conglobata or dissecting cellulitis of against P. acnes, as well as other organisms, support this the scalp, that is often associated with spondyloarthro- concept. pathy. The morphogenesis of acne lesions can be divided into The patient often presents with pain, multiple red, hard, two phases. The first one is non-inflammatory, during raised nodules in areas where apocrine glands are which keratin accumulates in affected follicles producing concentrated. As suppuration progresses, surrounding whiteheads (closed comedones), which have very small cellulitis may emerge. Chronic recurrences result in orifices, and blackheads (open comedones) which have palpable thick sinus tracts under the skin, which can turn distended orifices. The second phase is an inflammatory into draining fistulas. In chronic condition the multiple one during which a variety of inflamed lesions may develop nodules can coalesced and become surrounded by a fibrous from some of comedones. reaction resulting in scarred and unsightly appearance of P. acnes is known to be associated with the inflammatory the area. process in acne lesions [15], Propionibacterium spp. possess HI can present as a primary condition, but it may also be immunostimulatory mechanisms such as complement observed in association with: Crohn disease, irritable activation, stimulation of lysosomal enzyme release from bowel syndrome, Down syndrome, Graves disease or human neutrophils, and production of serum-independent Hashimoto thyroiditis, Sjo¨gren syndrome, arthritis, and neutrophil chemotactic factors [16]. Organisms other than herpes simplex. P. acne may contribute to the inflammatory process. These Culture of blood and any exudate and/or aspiration or include Peptostreptococci and anaerobic Gram-negative drainage of larger nodules for aerobic and anaerobic bacilli such as Porphyromonas and Prevotella spp. [17].A bacteria should be obtained. recent study highlighted the polymicrobial nature of over two-thirds of culture positive pustular acne lesions and 6.3. Management suggests the potential for pathogenic role of aerobic and anaerobic organisms other than P. acnes and Staphylococ- Treatment of this condition is difficult and involves the cus spp. in acne vulgaris [17]. administration of antimicrobial therapy, and moist heat locally to establish drainage in the initial phases of the 7.2. Management infection. Large abscesses are surgically drained. Gram’s stain results can guide the selection of empiric Antimicrobial therapy is a common adjuvant in the antimicrobial therapy. However, the final choice of agents management of acne vulgaris. Topical or systemic anti- should be determined by the isolation of specific organisms, microbial agents effective against anaerobic bacteria aerobes and anaerobes, and the results of antimicrobial including P. acne (i.e. clindamycin, macrolides and tetra- susceptibility testing. cylines) are benefital. The empirical choice of antimicro- Initial empiric antimicrobial therapy should be effective bials may not always provide coverage for some of the against S. aureus as well as potential aerobic and anaerobic resistant organisms that can be recovered from pustular pathogens. Antimicrobial agents active against S. aureus acne lesions. Processing pustular specimens for aerobic and and anaerobic bacteria include clindamycin, a carbapenem, anaerobic bacteria can provide guidelines for adequate cefoxitin, and beta-lactamase inhibitor and penicillin management of infected acne lesions. combinations, and metronidazole with beta-lactamase- resistant penicillin. Cefoxitin and carbapenems also pro- References vide coverage against Enterobacteriaceae. However, agents active against Enterobacteriaceae (i.e., aminoglycosides, a [1] Finch R. Skin: and soft-tissue infections. Lancet 1988;1(8578):164–8. quinolone, a fourth-generation cephalosporins) should be [2] Brook I, Frazier EH. Aerobic and anaerobic bacteriology of wounds and cutaneous abscesses. Arch Surg 1990;125:1445–51. added when treating infections involving these bacteria. [3] Meislin HW, Lerner SA, Graves MH, et al. Cutaneous abscesses: Coverage against MRSA is discussed at the section on anaerobic and aerobic bacteriology and outpatient management. Ann cutaneous abscesses. Intern Med 1977;7:145–9. Author's personal copy

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