Abstract
Kingella kingae is an important cause of invasive infections in young children from Western countries. Although increasing reports indicate that this organism is the leading agent of bone and joint infections in early childhood, data on K. kingae infections from resource-limited settings are scarce, and none has yet been reported in Africa. We herein report the diagnostic and epidemiological investigations of the first case of K. kingae arthritis identified in a child from sub-Saharan Africa. A 5-year-old Cameroonian boy presented with a sudden painful limp which appeared in the course of a mild rhinopharyngitis. He lived in Cameroon where he had been vaccinated with BCG at birth and moved to France for holidays 4 days before consultation. There was no history of trauma and he did not have any underlying medical condition. Upon admission, he had a temperature of 36.7°C, and clinical examination revealed right-sided knee tenderness and effusion that was confirmed by ultrasound imaging. Laboratory results showed a white blood cell count of 5,700 cells/mm3, C-reactive protein level of 174 mg/L, and platelet count of 495,000 cells/mm3. He underwent an arthrocentesis and was immediately given intravenous amoxicillin-clavulanate. Conventional cultures from blood samples and synovial fluids were negative. Polymerase chain reaction (PCR) assay targeting the broad-range 16S rRNA gene and real-time quantitative PCR assays targeting Mycobacterium species were negative. Surprisingly, real-time PCR assays targeting the cpn60, rtxA, and rtxB genes of K. kingae were positive. Multicolor fluorescence in situ hybridization specific for K. kingae identified the presence of numerous coccobacilli located within the synovial fluid. Finally, multilocus sequence typing analysis performed on deoxyribonucleic acid directly extracted from joint fluid disclosed a novel K. kingae sequence-type complex. This case report demonstrates that K. kingae may be considered as a potential cause of septic arthritis in children living in sub-Saharan Africa, and hence the burden of K. kingae infection may be not limited to the Western countries. Further studies are required to determine the prevalence of K. kingae infection and carriage in Africa.
Highlights
Kingella kingae is an emerging pathogen recognized as the primary etiology of bone and joint infections in young children from Western countries [1, 2]
Large-scale epidemiological studies based on multilocus sequence typing (MLST) analysis of K. kingae showed that dominant clones belonging to sequence-type complexes 6 (STc-6), -14, -23, and -25 accounted for 72% of strains disseminated worldwide, mainly in the USA, Europe, and Israel, with ST-14 and ST-25 being positively associated with osteoarticular infections [8]
Septic arthritis caused by S. aureus affects most frequently older children and is more prone to result in a higher systemic inflammatory response when compared with K. kingae infections, and the organism is recovered without difficulty by culture of blood and synovial fluid aspirates [10, 16, 17]
Summary
Kingella kingae is an emerging pathogen recognized as the primary etiology of bone and joint infections in young children from Western countries [1, 2]. Harbored in the oropharynx of children aged 6–48 months, the prevalence of K. kingae oropharyngeal carriage ranges from 8 to 23% from studies carried out in Israel, Switzerland, and New Zealand [3,4,5,6] Because this Gram-negative bacterium is usually responsible for a mild to moderate inflammatory response, and its detection is notoriously difficult by conventional culture, diagnosis of K. kingae infection requires a high index of suspicion and the use of adequate detection methods such as real-time quantitative polymerase chain reaction (qPCR) assays [6, 7]. Among the 70 STs of K. kingae that are documented in the multilocus sequence database (MLST) of the Institut Pasteur database (http://bigsdb.pasteur.fr/perl/ bigsdb/bigsdb.pl?db=pubmlst_kingella_seqdef_public&page= downloadProfiles&scheme_id=1), ST-26, which belongs to the highly invasive STc-25, was the closest ST by sharing four alleles, namely, adk-2, cpn, gdh/zwf-13, and recA-2 with the causative strains that were identified (Table 2). Since each of these housekeeping genes is present in one copy in the whole genome of K. kingae, these findings suggested co-infection by strains belonging to distinct STs
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