Clinical Microbiology Laboratory, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer-Sheva 84101, Israel
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Abstract |
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Introduction |
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Despite the increasing recognition of K. kingae as an important cause of invasive infections, information on the antibiotic susceptibility profiles of the organism remains limited.1,5,6 This study was conducted to examine the prevalence of antimicrobial drug resistance in a large collection of K. kingae isolates.
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Materials and methods |
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Identification of the organism was based on the typical morphological and physiological characteristics of the species: Gram-negative bacteria that appeared as pairs or short chains of small bacilli with tapered ends; growth and production of ß-haemolysis on trypticase soy agar with added 5% sheep haemoglobin (blood-agar medium) and failure to grow on MacConkey agar; positive oxidase and negative catalase; urease production; motility; and indole reactions and production of acid from glucose and maltose, but not from other sugars.
Isolates were thawed and subcultured twice on blood-agar plates. Antibiotic susceptibilities to trimethoprim sulphamethoxazole, erythromycin, clindamycin, tetracycline, chloramphenicol, gentamicin and ciprofloxacin were determined by the disc diffusion method of Kirby and Bauer on MuellerHinton plates with 5% added sheep blood (Hy Laboratories, Rehovot, Israel). Antibiotic content of the discs (manufactured by Oxoid, Hampshire, UK) was as follows: trimethoprimsulphamethoxazole 1.25 and 23.75 µg, respectively, erythromycin 15 µg, clindamycin 2 µg, tetracycline 30 µg, chloramphenicol 30 µg, gentamicin 10 µg and ciprofloxacin 5 µg. As there are no standardized criteria for determining antibiotic susceptibility of K. kingae, disc diffusion results were interpreted according to the NCCLS guidelines for Staphylococcus aureus.7
Presence of ß-lactamase was determined by the nitrocefin method. Because different penicillins and cephalosporins are widely used for the treatment of systemic infections, penicillin was selected as the ß-lactam group representative. The MIC of penicillin G was determined by the Etest (AB Biodisk, Solna, Sweden) on the same medium.
In addition, the influence of prolonged incubation of plates and atmosphere on susceptibility testing results was also studied. A random subset of 10 isolates was incubated with and without added 5% CO2, and zones of inhibition around discs and Etest strips were read after 24 and 48 h of incubation. Three capnophilic isolates (including ATCC 23332) were tested in the CO2-enriched atmosphere only.
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Results |
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Discussion |
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Other reports of K. kingae isolates from patients with invasive infections, however, suggest that susceptibility of the organism to antibiotics is not uniform.3,9,10 Production of ß-lactamase has been detected in an isolate from an adult AIDS patient with bacteraemia, and in three of five K. kingae isolates from children with bacteraemia or skeletal infections in Iceland.3,9 In addition, sporadic resistance to the trimethoprimsulphamethoxazole combination and to ciprofloxacin has also been reported.3,10
The results of the present study, which comprises a large number of organisms isolated from individuals living in different geographical areas of Israel and collected over a 12 year period, show that antimicrobial susceptibility patterns of K. kingae are quite uniform and predictable. All test organisms were ß-lactamase negative, exhibited low penicillin MICs and were susceptible to erythromycin, gentamicin, chloramphenicol, tetracycline and ciprofloxacin, and all but one were susceptible to trimethoprimsulphamethoxazole. This finding is consistent with the clinical observation that invasive K. kingae infections respond promptly to antimicrobial therapy and especially to drugs such as ß-lactams, macrolides or trimethoprimsulphamethoxazole, which are often administered empirically to young children.14 On the other hand, a large fraction of isolates were found to be resistant to clindamycin. This observation is consistent with the resistance of K. kingae isolates to lincomycin, a related antimicrobial drug, reported in other studies.1,5
Susceptibility of isolates to glycopeptides was not tested because this class of antimicrobial drugs is ineffective against Gram-negative organisms due to the large size of the molecule, which cannot pass through the outer membrane to reach the peptidoglycan target site. In fact, in a previous study we have used a vancomycin-containing selective medium to inhibit growth of Gram-positive flora and facilitate the isolation of K. kingae from pharyngeal cultures.4
In recent years, important paediatric pathogens such as Streptococcus pneumoniae, H. influenzae and Moraxella catarrhalis have developed resistance to ß-lactams, macrolides or trimethoprimsulphamethoxazole. These organisms are commonly carried in the respiratory tract of young children and are therefore frequently exposed to selective antibiotic pressure. A few years ago, it was demonstrated that K. kingae is also a component of the normal respiratory flora of young children.4 In a prospective study conducted among young attendees at a day-care centre in southern Israel, 109 of 624 (27.5%) throat cultures yielded K. kingae and 35 of 48 (72.9%) children yielded the organism at least once over an 11 month period.4 The results of the present study show that despite the frequent respiratory carriage of the organism, K. kingae remains susceptible to antimicrobial drugs that are commonly prescribed to young children with bacteraemia or skeletal infections.
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Notes |
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References |
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2 . Goutzmanis, J. J., Gonis, G. & Gilbert, G. L. (1991). Kingella kingae infection in children: ten cases and a review of the literature. Pediatric Infectious Disease Journal 10, 67783.[ISI][Medline]
3 . Birgisson, H., Steingrimsson, O. & Gudnason, T. (1997). Kingella kingae infections in paediatric patients: 5 cases of septic arthritis, osteomyelitis and bacteraemia. Scandinavian Journal of Infectious Diseases 29, 4958.[ISI][Medline]
4 . Yagupsky, P. & Dagan, R. (1997). Kingella kingae: an emerging cause of invasive infections in young children. Clinical Infectious Diseases 24, 8606.[ISI][Medline]
5 . Prère, M. F., Seguy, M., Vezard, Y. & Lareng, M. B. (1986). Sensibilitè aux antibiotiques de Kingella kingae. Pathologie Biologie 34, 6047.[ISI][Medline]
6 . Jensen, K. T., Schonheyder, H. & Thomsen, V. F. (1994). In-vitro activity of ß-lactam and other antimicrobial agents against Kingella kingae. Journal of Antimicrobial Chemotherapy 33, 63540.[ISI][Medline]
7 . National Committee for Clinical Laboratory Standards. (1999). Performance Standards for Antimicrobial Susceptibility Testing: Ninth Informational Approved Standard Supplement M100-S9. NCCLS, Wayne, PA.
8 . Kugler, K. C., Biedenbach, D. J. & Jones, R. N. (1999). Determination of the antimicrobial activity of 29 clinically important compounds tested against fastidious HACEK group organisms. Diagnostic Microbiology and Infectious Diseases 34, 736.[ISI][Medline]
9 . Sordillo, E. M., Rendel, M., Sood, R., Belinfanti, J., Murray, O. & Brook, D. (1993). Septicemia due to beta-lactamase-positive Kingella kingae. Clinical Infectious Diseases 17, 8189.[ISI][Medline]
10 . Giamarellou, H. & Galanakis, N. (1987). Use of intravenous ciprofloxacin in difficult-to-treat infections. American Journal of Medicine 82, 34651.[ISI][Medline]
Received 28 February 2000; returned 21 June 2000; revised 11 September 2000; accepted 9 October 2000