First report of Kocuria marina spontaneous peritonitis in a child

SBP is a rare presentation of peritonitis in childhood. Most cases are due to Streptococcus pneumoniae, Escherichia coli or staphylococcal strains [4]. However, in few cases no pathogen can be identified [5]. To our knowledge, this is both the first description of SBP caused by Kocuria marina in a child, and the first description of a K. marina SBP in a patient with no underlying risk factor.

Kocuria spp are members of the Micrococcaceae family. They are gram-positive, usually aerobic, coccoid, non-encapsulated bacteria. Seventeen species have been recognized so far [6]. They are environmental bacteria that can be encountered in mammals including humans’ skin and in the commensal flora of the oropharynx. Certain species (but not K. marina) have been isolated from traditional Korean fermented seafood [7]. Kocuria-related infections are rare. Bacteremia, peritonitis, brain abscess, endocarditis, cholecystitis and UTI have been described with K. rosea, K. kristinae, K. varians, and K. rhizophila (Table 1).

Kocuria marina has been isolated from marine sediments and first identified in 2004 [8]. In 2009, Lee et al. described two cases of primary peritonitis caused by K. marina in adult patients undergoing peritoneal dialysis [9]. A small case series reported a positive K. marina blood culture in a 57 year-old oncologic patient with a central venous catheter [10]. However, it was considered a contaminant by the authors. We did not find any other report of K. marina infection.

In our patient, the organism was identified on peritoneal fluid samples, obtained at the time of surgery. Contamination of the fluid from the skin or from the intestinal content seems very unlikely because of the sterile skin condition at the time of surgery and the absence of visible intestinal perforation. The sample was seeded on the surface of a 5% sheep blood agar and incubated at 35°C in 5% CO2. After 48 h of incubation, the isolate was identified as Kocuria marina by MALDI-TOF mass spectrometry (score value = 2.014). MALDI target plates were inoculated by picking a freshly grown overnight colony with the tip of a sterile toothpick and smearing the specimen directly onto a ground steel MALDI target plate in a thin film. The microbial film was then overlaid with 1.5 μl of a MALDI matrix (a saturated solution of α-cyano-4-hydroxy-cinnamic acid in 50% acetonitrile–2.5% trifluoroacetic acid) and allowed to dry at room temperature. Mass spectra were acquired using the MALDI-TOF spectrometer in a linear positive mode (Microflex; Bruker Daltonics). Measured mass spectra ranged from 2,000 to 20,000 Da. Extraction of the peaks from the generated mass spectra and their matching against the reference spectra of the integrated database provided by the manufacturer was performed with MALDI Biotyper software (Bruker Daltonics). Unfortunately, the peritoneal fluid could not be sent for PCR-based confirmation of the species and antibiotic susceptibilities were not performed.

According to a 2010 review [6] which focuses on antibiotic susceptibilities for Kocuria species, K. marina should respond to ampicillin and other betalactam-based antibiotics while showing a relative resistance to penicillin [10]. At the time of presentation our patient had been treated with oral cephalosporin for 9 days, which might have covered early symptoms and might explain the acute severe clinical presentation.

Direct infection through cutaneous breaches associated with sea-bathing seems unlikely in our patient [11].