Kingella kingae, an emerging pathogen producer arthritis, osteomyelitis, and endocarditis Spondylodiscitis: culture and PCR

Information 05-11-2014.

Kingella kingae is a bacillus or gram - negative cocobacillus, difficult fading, so it sometimes appears as gram - positive, appearing in pairs or short chains, facultative anaerobic, oxidase positive and negative catalase that uses only glucose and maltose. One of its important microbiological characteristics has hampered its isolation is their difficulty to grow on solid media such as agar agar blood or chocolate. Therefore, currently in clinical tables that may be involved is recommended to introduce the sample in any kind of bottles with liquid medium used for blood cultures.

It is now considered an emerging pathogen because it has been seen that is very involved in children 's septic arthritis, as well as producing cases of osteomyelitis, spondylodiscitis and endocarditis. Septic arthritis in children is the leading cause gram - negative in children 2 to 5 years, which mainly produces arthritis of large joints (knee, hip, ankle or shoulder), but occasionally causes metacarpophalangeal, sternoclavicular, and tarsal arthritis. It is also responsible for over 25% of hematógenas spondylodiscitis in children under 4 years.

In its pathogenesis consider that it is a bacterium that colonizes the posterior pharynx, and is transmitted from person to person through respiratory secretions, being highly prevalent in nurseries, the existing close contact among children, which can be found colonizing between 9 and 12% of children aged 1 to 2 years old, although sometimes it has been found colonizing until 28-70% of children of any group as nurseries. During the first year of life it is lower than the prevalence of colonization, attributable to the antibodies transferred from the mother, and is also low in older ages when formed antibodies induced by colonization. Colonization is due to the presence of a pili (fimbriae) type IV. Thanks to the adhesion to mucosal cells and the production of a toxin (RTX), and the provision that produce respiratory viral infections, can invade the epithelium, and passing blood, causing uncomplicated bacteremia, that bears, given its tropism for articular synovium, to cause septic arthritis. At other times it causes through hematogenous spread, osteomyelitis, one Spondylodiscitis or endocarditis.

Microbiological diagnosis is difficult because of the problems discussed his difficulty discolor in the Gram stain, and its difficult development in solids as blood agar or chocolate agar media, so before clinical suspicion in the commented clinical trials , inoculating the sample must be usually monobacteriana in a flask of liquid medium used in blood cultures and observed after growth, making reseeding in one of the rich media commented solid.

The difficulty of conventional microbiological diagnosis by culture methods, is one of the microorganisms candidates to be diagnosed by molecular methods with PCR (polymerase chain reaction (Polymerase Chain Reaction). For this test two molecular targets, gene can be used 16S rRNA or RTX gene. the advantage of the first method is that while other bacteria causing the process could be detected as with the target 16S rRNA gene this gene of any bacteria would be amplified, but has the disadvantage that to know the species of bacteria must proceed to sequencing. the advantage of amplification through the target gene coding RTX its toxin, it is that it requires subsequent sequencing, but would not be detected other possible causes Kingella kingae were not.

For treatment, must be taken into account that it is very sensitive to antimicrobial ?-lactam as (penicillins and cephalosporins, penicillins antistaphylococcal except as oxacillin and the like) bacteria, being very occasional strains producing ?-lactamase. This is important to consider because of the empirical therapeutic recommended in cases of arthritis or osteomyelitis is an antistaphylococcal penicillin, except in areas where a high prevalence of Staphylococcus aureus methicillin-resistant (MRSA), in which case there is recommended associating a ?-lactam with vancomycin. It is also sensitive to aminoglycosides, although these should not be the drugs of choice for its potential toxicity in long term treatment; macrolides, which have the problem that they are not bactericidal antimicrobial; to fluoroquinolones, tetracyclines and chloramphenicol, though these antimicrobials are not of choice for treatment in children, the effects that can have on bone development or toxicity. It is also sensitive to rifampicin, but this antimicrobial is used in Kingella kingae infections, when you want to make a chemoprophylaxis of a group of children in which there has been a case or outbreak of arthritis by this bacterium.

Tests in IVAMI:

• culture for isolation.
• PCR for 16S rRNA and molecular targets RTX gene.

Samples recommended:

arthritis (synovial fluid): depositing 1 to 2 mL of liquid sample in a tube or in a sterile container, preferably polypropylene to prevent breakage, containing 3 mL of a universal transport medium.
Osteomyelitis aspirate or bone lesion biopsy deposited in a sterile tube, preferably polypropylene to prevent breakage.
posterior pharyngeal exudate: exudate swab impregnated posterior pharynx.

Preservation and shipment of sample:

Refrigerated (preferred) for less than 2 days.
Frozen: over 2 days.

Delivery times :

• culture for isolation: 48 to 72 hours.
• PCR for 16S rRNA and molecular targets RTX gene 48 to 72 hours.

Cost of testing: