This was a 38-year-old female who had given birth by normal delivery 10 days earlier and was exclusively breastfeeding, although complicated by inverted nipples, who came to Accident and Emergency due to poor progress of left-sided mastitis. She had a five-day history of pain, engorged breasts, inability to express milk and a fever of 38 °C. There was no purulent discharge from the nipple and her other breast was normal. She reported being treated with oral cloxacillin for four days, with worsening of her symptoms. Her previous medical history included asthma and having undergone surgery for hidradenitis suppurativa and synovial osteochondromatosis of the hip.
On examination, her left breast was enlarged and erythematous in appearance, with a 5−6-cm painful, lumpy, fluctuant area in the upper outer quadrant. Examination of the right breast was normal.
On the same day she attended Accident and Emergency, the abscess was drained and abundant purulent contents were removed. In addition, it was decided to admit her for empirical IV antibiotic therapy with amoxicillin-clavulanic acid (2 g/200 mg every 8 h).
In the laboratory, the sample was processed for Gram staining and standard bacteriological culture in aerobic and anaerobic atmosphere (seeded on blood agar, MacConkey agar, chocolate agar, Schaedler agar and thioglycolate broth).
Gram staining showed the presence of abundant polymorphonuclear cells accompanied by clusters of Gram-variable bacilli (Fig. 1); cultures were negative at 48 h.
Clinical course and diagnosis
In view of the staining result, it was decided to prolong the incubation for five more days (a total of seven days) and to perform direct 16S ribosomal RNA PCR on the sample. Culture was negative after seven days and PCR was positive. The amplified product was sent for Sanger sequencing to the Instituto de Investigación Sanitaria (IIS) [Health Research Institute] Biobizkaia sequencing platform. The sequence obtained was analysed with the MEGA5 program and compared with the NCBI database: it showed a 99% similarity with Lawsonella clevelandensis reference sequences.
In light of the PCR result and in the absence of growth in prolonged cultures, the sample (which had been stored at −4 °C for one week) was recovered and Ziehl-Neelsen staining was performed.
The staining showed accumulations of acid-fast bacilli (Fig. 2). In addition, the sample was reseeded on Schaedler agar and incubated in an individual anaerobic atmosphere with observation every 48 h. After 10 days, pure growth of greyish, non-haemolytic microcolonies was observed. No identification was obtained by mass spectrometry (Bruker MALDI-TOF) and identification was confirmed by PCR for 16S ribosomal RNA, with a positive result for L. clevelandensis. The microorganism was not viable for antibiotic susceptibility testing.
The patient was discharged 48 h after admission as she was making good progress and she was maintained on the same oral treatment (875 mg/8 h) for seven days.
Closing remarksL. clevelandensis is a pleomorphic, Gram-positive, anaerobic and partially acid-fast bacterium, first reported by Harrington et al.1 in 2013, with four reported cases of abscesses in different locations. Phylogenetic analysis of 16S ribosomal RNA gene sequences together with cellular fatty acid analysis have determined that L. clevelandensis is in the suborder Corynebacterineae.2 It is a slow-growing microorganism which, in some cases, has been isolated after incubation of the sample in enriched medium under strict anaerobic conditions for 4–13 days.3 This bacterium is difficult to identify by conventional methods because its protein spectrum is not included in the MALDI-TOF (Bruker or bioMerieux) databases. Morphologically, it can mimic other microorganisms, primarily Nocardia spp.,4 which can lead to inappropriate antibiotic therapy. The use of molecular techniques is therefore necessary to detect and identify the microorganism.5
Clinically, unlike other anaerobic microorganisms that usually cause polymicrobial abscesses, L. clevelandensis is associated with the formation of monomicrobial abscesses in different locations (spine, breast, brain and liver). To date, fewer than 20 cases of L. clevelandensis infections have been reported worldwide and this is the first case reported in Spain. The environmental niche of L. clevelandensis is still unknown. It is not known whether this microorganism is part of the skin flora, but this possibility has been suggested because of reported cases of breast abscess and postoperative infection.1 This case reflects the need to implement molecular techniques for the identification of non-culturable or slow-growing microorganisms.
FundingThe article did not receive funding of any kind.
The authors declare that they have no conflicts of interest.
