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Anaerobe 15 (2009) 201–203

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Anaerobe

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Clinical microbiology

Recurrent abscesses due to Finegoldia magna, Dermabacter hominisand Staphylococcus aureus in an immunocompetent patient

J. Martin a, P. Bemer a,*, S. Touchais b, N. Asseray c, S. Corvec a

a Department of Bacteriology-Hygiene, Nantes University Hospital, Franceb Department of Orthopaedy, Nantes University Hospital, Francec Referent in Antibiotherapy, Nantes University Hospital, 44093, Nantes cedex 1, France

a r t i c l e i n f o

Article history:Received 15 January 2009Received in revised form10 March 2009Accepted 19 March 2009Available online 27 March 2009

Keywords:Recurrent abscessesFinegoldia magnaImmunocompetent patientMoxifloxacin

* Correspondence to: P. Bemer, Department of MicHospital, CHU Hotel-Dieu, 9 quai Moncousu, 44093 Nþ33 2 40 08 39 79; fax: þ33 2 40 08 38 29.

E-mail address: pascale.bemer@chu-nantes.fr (P. B

1075-9964/$ – see front matter � 2009 Elsevier Ltd.doi:10.1016/j.anaerobe.2009.03.006

a b s t r a c t

A case of recurrent abscesses in an immunocompetent patient is reported, involving the opportunistichuman pathogen Dermabacter hominis, the virulent anaerobic pathogen Finegoldia magna and Staphy-lococcus aureus.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Acute bacterial infections have various presentations andseverity. We report a case of recurrent abscesses due to a mixture ofboth aerobic and anaerobic bacteria (Dermabacter hominis, Staph-ylococcus aureus and Finegoldia magna), causing chronic and painfulinfection. Prolonged courses of antibiotics were needed forsuccessful eradication.

2. Case report

A 31-year-old man was admitted to the emergency departmentfor an abscess of the left plantar arch with purulent dischargeoccurring for 10 days. A malformation of the left forefoot betweenM1 and M2 metatarsal bones required wearing of orthopaedicshoes since childhood. His medical history highlighted erysipelaswith toe-web intertrigo of the left foot and ankle 4 years ago. Thepatient presented with painful edematous lesions of the left plantararch without necrosis, gas in tissues or foul odor. An intermediateform of cellulitis with abscess was suspected. No sign of systemictoxicity was observed (e.g. fever or hypothermia, hypotension andtachycardia). The value of the complete blood count was in the

robiology, Nantes Universityantes Cedex 01, France. Tel.:

emer).

All rights reserved.

expected normal range. The serum concentration of C-reactiveprotein was less than 10 mg/L. Ultrasonography of the lesionsdemonstrated subcutaneous accumulation of fluid. The patientunderwent surgical drainage with debridement of necrotic infectedtissue. The patient did not receive antimicrobial therapy prior tosample collection. During surgery, two specimens were obtained byneedle aspiration and tissue excision. The patient received anempirical antimicrobial therapy based on co-amoxiclav or amoxi-cillin–clavulanic acid (3 g per day) for 7 days. Local care was startedwith sterile saline dressings. Gram stain of the tissue specimensrevealed numerous polymorphonuclear leukocytes with Gram-positive cocci. The horse blood agar media inoculated for bothspecimens yielded growth of S. aureus susceptible to methicillinafter 1 day of incubation. Antibiotic treatment was changed tooxacillin for a further 7 days. Gram-positive anaerobic cocci wereisolated from Schaedler broth culture medium after 5 days ofincubation from both samples. They were identified as F. magna(formerly Peptostreptococcus magnus), and were found resistant toclindamycin. The patient, admitted for a first recurrence on day 15,was treated by drainage at the consultation without specimencollection and without any antibiotic treatment. A second recur-rence occurring within 45 days required surgery. Three tissuesamples, obtained during surgery, revealed numerous poly-morphonuclear leukocytes with Gram-positive bacilli after Gramstaining. The 3 specimens were positive in culture on horse bloodagar after 1 day of incubation with an aerobic Gram-positiveorganism identified as D. hominis susceptible to b-lactams and

J. Martin et al. / Anaerobe 15 (2009) 201–203202

resistant to erythromycin. F. magna resistant to clindamycin wasisolated from the 3 tissue specimens after 5 days of incubation fromanaerobic broth medium. S. aureus was not isolated at this time. Atreatment by pristinamycin (3 g per day) was started for 15 days.Ten days later, the patient was seen at the consultation for persis-tence of the purulent discharge. The antibiotic was changed to co-amoxiclav or amoxicillin-clavulanic acid (3 g per day) for 15 days.Bacterial cultures from a swab sample yielded massive growth of S.aureus (after 1 day), and F. magna (after 5 days) with the sameantibiotic susceptibility pattern. According to a multidisciplinaryteam discussion, the treatment was changed after 7 days fora combination of amoxicillin (8 g per day) and moxifloxacin(400 mg per day) for a further 6 weeks. Protection of the woundfrom weight bearing until healing was achieved using Barouk-typehalf-shoes. The patient recovered uneventfully (see Fig. 1).

3. Microbiology

All the specimens were quickly transported to the laboratoryand inoculated within 2 h after collection. Gram stain of the tissuespecimens revealed numerous polymorphonuclear leukocytes withGram-positive cocci. Gram-positive bacilli were observed in the 3samples positive in culture to D. hominis. Horse blood agar plateswere inoculated for the isolation of aerobic organisms. The plates,incubated at 37 �C under 5% carbon dioxide, were examined at 24and 48 h. For the isolation of anaerobes, specimens were inoculatedinto enriched thioglycolate broth medium (Schaedler broth, bio-Merieux, Marcy-l’Etoile, France) and incubated for 14 days.

Cultures were positive to S. aureus after 24 h of incubation. Theidentification was based upon colony and Gram stain morphologiesand a positive catalase reaction. A rapid latex agglutination kit wasused for the simultaneous detection of clumping factor, protein Aand staphylococcal capsular polysaccharide antigens (PastorexStaph Plus test, BioRad, Marnes-la-Coquette, France). Antibioticsusceptibility testing was performed using the Vitek2 automatedsystem (bioMerieux, Marcy-l’Etoile, France). Detection of methi-cillin resistance was controlled by the disc diffusion methodaccording to recommendations of the Antibiogram Committee ofthe French Society for Microbiology (CA-SFM) [1]. The S. aureus

Day 1 D 15 D First abscess treated by surgeryTw

o perioperative samples positive to

S. aureus and

F. m

agna

First recurrence treated by drainage

magna

Co-amoxiclav

oxacillin

pristinamycin

Amoxicillin/moxifloxacin

7 days

7 days

Fig. 1. Antibiotic

strains were found susceptible to all antibiotics includingmoxifloxacin.

F. magna was isolated within 5 days after the inoculation toSchaedler broth medium from all the tissue specimens. Subcultureson Schaedler agar medium incubated under anaerobic conditionsyielded translucent colonies, which were identified as F. magnawith the semi-automatic API ID 32A gallery (bioMerieux, Marcy-l’Etoile, France). Antibiotic susceptibility testing was performedusing the disc diffusion method according to CA-SFM guidelines [1].Antibiotic susceptibility test results were interpreted after 48 h ofincubation according to the recommendations of the ClinicalLaboratory Standards Institute (CLSI) and the CA-SFM, as someresistant strains are falsely susceptible to clindamycin after 24 h ofincubation [1]. The F. magna isolates were susceptible to all theantibiotics including moxifloxacin except clindamycin.

D. hominis grew on 5% horse blood agar plate after 1 day as 0.5-to 1-mm-diameter grayish-white colonies. The Gram-positivebacilli had a coryneform morphology without branching. Amongbiochemical or enzymatic reactions, catalase and esculin hydrolysiswere positive. This bacterium was able to ferment glucose, sucrose,maltose and lactose, but not xylose. Identification was made withthe semi-automatic API Coryne gallery (bioMerieux, Marcy-l’Etoile,France, numerical profile 6570365). The biochemical identificationwas confirmed by sequencing the 500 first base pairs of the 16SrDNA on BIBI (Bioinformatic Bacteria Identification: http://www.ncbi.nlm.nih.gov) with a 100% similarity with the reference strain.Antibiotic susceptibility testing was performed using the discdiffusion method according to CA-SFM recommendations [1]. D.hominis was susceptible to b-lactams, fluoroquinolones and glyco-peptides, and was resistant to aminoglycosides, macrolides andlincosamides by the diffusion method [1].

4. Discussion

Skin and soft tissue infections are a generic term used todescribe a large range of infections such as acute infections of thehypodermis (erysipelas) and intermediate forms with abscesses,both called cellulitis, and necrotizing fasciitis. Those infectionsusually complicate a wound, ulcer or dermatosis. Abscesses and

45 D 55 D 62 D 104Second recurrence treated by surgeryThree perioperative sam

ples positive toD

. hom

inis and

F.

Third recurrence treated by drainage

Recovery

Multidisciplanary staff discussion

10 days

6 weeks

7 days

treatment.

J. Martin et al. / Anaerobe 15 (2009) 201–203 203

necrotizing fasciitis are polymicrobial infections caused bya mixture of aerobic, specifically S. aureus and b-haemolytic groupA streptococci, and anaerobic bacteria [2]. Aerobic bacteria promoteanaerobic growth by inducing tissue hypoxia, reducing redoxpotential and producing necessary nutrients for anaerobic growthas succinate [3].

Considering the three bacteria isolated from recurrent abscessesin our patient, the respective role of each bacterium is difficult toassess.

Gram-positive anaerobic cocci (GPAC), a major part of normalhuman flora colonizing skin, are the most common anaerobescultured from soft tissue infections. F. magna represents the mostcommon species [4]. The F. magna as well as S. aureus genomesencode virulence factors, which could explain its spreadingthrough subcutaneous tissues as well as S. aureus [5]. Usinga mouse abscess model, a synergy was demonstrated betweenanaerobic bacteria and S. aureus in their ability to induce abscesses[6]. It is often recovered in pure culture from a range of seriousinfections, notably in infected foot ulcers in diabetics, superficialabscesses and bone and joint infections. In a series of patients withseptic arthritis, F. magna was the most common anaerobe causinga chronic low-grade infection, which needed aggressive surgeryand prolonged courses of antibiotics for successful eradication [4].The case reported here highlights the importance of F. magna inmixed infections with other aerobic bacteria, as shown before [6]. F.magna, which was isolated from deep tissue specimens in spite ofsuccessive treatments, may contribute to the chronicity of thelesions.

S. aureus is the most common pathogen involved in acutebacterial skin infections. A synergistic role of S. aureus withanaerobic Gram-positive cocci including F. magna was previouslyshown [6]. In our patient, the presence of S. aureus in the thirdrecurrent abscess underlines the need for prolonged adequateantibiotic therapy.

D. hominis was shown in 1994 to comprise the former CDCcoryneform groups 3 and 5 bacteria [7]. This species, from thehuman skin flora, was first considered to be non-pathogenic [7].Nevertheless, in the last decade, D. hominis was the cause ofa cerebral abscess, a bacteremia, a peritoneal dialysis-associatedperitonitis and a chronic osteomyelitis in patients with immu-nosuppression and/or artificial devices [8–11]. In our observation,the patient suffered from an intermediate form of cellulitis withrecurrent abscesses. His major risk factors were hyperkeratosisresulting from a forefoot malformation, a toe-web intertrigo,which are a major portal of entry [2] and a history of erysipelas.However he was not diabetic or immunosuppressed. Deter-mining the role of D. hominis in the pathogenesis of the lesions isdifficult. The fact that D. hominis was isolated from threedifferent perioperative specimens is clinically significant. To thebest of our knowledge, this is the first time that D. hominis canbe considered as an opportunistic pathogen in an immunocom-petent patient.

Combinations of antibiotics effective against both aerobic andanaerobic bacteria, including b-lactams plus inhibitor, clindamycinand fluoroquinolones, are indicated for the treatment of necrotizingfasciitis [2]. Pristinamycin is an oral well-tolerated antibiotic witha potent antistaphylococcal, antistreptococcal, and antianaerobicactivity. Resistance to clindamycin in GPAC is due to an RNA-methylase causing a cross-resistance to macrolide–lincosamide–streptogramin B (MLSB phenotype). MLSB resistance reducesbactericidal activity of pristinamycin without affecting the minimalinhibitory concentration. Moxifloxacin is a new fluoroquinolonewith broad-spectrum bactericidal activity including anaerobicbacteria, excellent oral bioavailability, and good tissue penetration.In the case reported here, clinical success was achieved by usinga combination of antibiotherapy including moxifloxacin, andcomplete protection from weight bearing until healing.

The bacterial diagnosis of polymicrobial infection requiresseveral enriched media. Co-infection with slow-growing anaerobicbacteria like F. magna should be kept in mind. Liquid culture mediaare useful as primary solid culture media can dry out after somedays of incubation. The anaerobic liquid media should be observedafter at least two weeks and systematically sub-cultured on bloodagar incubated under anaerobic conditions, if there is any slightestdoubt about their positivity.

This case focuses on the diversity and magnitude of abscessformation. Preliminary antibacterial therapy should be adapted tothe presence of anaerobic bacteria in late cultures. Moreover, theremoval of pressure on affected feet known as off-loading remainsa challenge, as seen in the management of neuropathic diabetic footulcers.

References

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[10] Radtke A, Bergh K, Oien CM, Bevanger LS. Peritoneal dialysis-associated peri-tonitis caused by Dermabacter hominis. J Clin Microbiol 2001;39(9):3420–1.

[11] Van Bosterhaut B, Boucquey P, Janssens M, Wauters G, Delmee M. Chronicosteomyelitis due to Actinomyces neuii subspecies neuii and Dermabacterhominis. Eur J Clin Microbiol Infect Dis 2002;21(6):486–7.