ECCMID 2012
Poster N° 1757
Neisseria gonorrhoeae identification,
Usefulness of the Vitek 2 NH card.
Galarza,P; Soloaga,R; Pagano,Irene; Diez, A; Oviedo, Claudia; Pidone,J;
Guelfand,L; Galas,M; Carrion,N.
Hospital Naval “Pedro Mallo”, National Institute of Infectious Diseases ANLIS “Dr Carlos Malbran”
Gonococcal Antimicrobial Surveillance Argentinean Programm. Buenos Aires,Argentina
Introduction
Neisseria species are obligate human pathogens with no other natural host.
N.gonorrhoeae and N.meningitidis are the two main pathogens of the group. Other species of Neisseria such as N.lactamica, N.cinerea, N.lactamica, N.sicca, N.mucosa,
N.subflava, N.elongata are generally considered commensals, but have been implicated as causes of infection in patients who are immuno-compromised.
Symptoms of infection with N.gonorrhoeae (NG) differ depending on the site of infection. It causes urethritis, cervixitis, prostatitis, orchitis, pharyngitis, conjuntivitis,
pelvic inflamatory disease and disseminated gonococcal disease. The main way of transmission is the sexual activity. Infections in children is a sexual abuse indicator.
For these reasons, wrong identification could have serious legal and social consequences
Isolates from primary culture are identified by Gram stain,oxidase and by at least two of the following identification principles: carbohydrate utilisation, detection of
performed enzymes or reactivity with immunological reagents.
The Vitek 2 NH card, based on colorimetric technology, contains 30 biochemical test in the following categories:
 11glycosidase and peptidase tests
 10 acidification tests
 5 alkalinization tests
 4 miscellaneous tests
 The card has a database that includes 27 taxa of gram-negative fastidiuous bacteria
 In medicolegal cases (child and sexual abuse) some reference centers suggest three test: biochemical, inmunological and molecular techniques.
Rapid and reliable identification is critical.
Objetive
The aim of this study was to determine the usefulness and reliability of the Vitek 2C NH card in the identification of NG.
Materials and Methods
A total of 115 unique clinical isolates of N.gonorrhoeae corresponding to different pheonotypic clones from the Gonococcal Antimicrobial Surveillance Argentinean
Programm were tested by Vitek 2 C (bioMerieux, Marcy l’Etoile, France) using the NH card.
The isolates were previously identified to the species level by colony morphology, Gram stain, oxidase, superoxol, utilisation of carbohydrates testing and by latex
agglutination with monoclonal antibodies using Phadebact Monoclonal GC Test (Bactus AB, Sweeden).
GRAM STAIN
SUPEROXOL TEST (H2O2 30 %)
OXIDASE TEST
CARBOHYDRATES UTILISATION
Strains were isolated in pure culture on chocolate agar. A bacterial suspension made in 0,45% aqueous ClNa was adjusted to a
McFarland of 3 with Vitekk 2 Densicheck instrument (bioMerieux).
The time period from preparation of the inoculum to loading of the card was less than 10 minutes.
 The inoculated card was loaded into the Vitek 2C automated identification system according to the manufacturer´s instruction.
A computer-assisted algorithm was used to interpret the results.
 Four identification categories were considered:
A) Correct identification: unambiguous correct identification to the especies level.
B) Low level of discrimination: either identification to the genus level or a low level of discrimination between two or more species, including the correct species.
C) No identification: strains without results
D) Missidentification: The species identified with the NH card was different from the identified using the reference method.
Results
The Vitek 2C NH card correctly identified 111 (96.5%) strains of 115 isolates; one strain was identified with low discrimination (0.86%), another one (0.86%) was
misidentified (N.meningitidis) and another two (1.7%) remained unidentified.
An intermittent reading every 15 min allowed for identification after 6 hours.
Microorganism
N.gonorrhoeae Identification. Perfomarne of Vitek 2C NH card
N.gonorrhoea
e
strains
Total n° of
isolates
tested
115
Correct
Low
Missidentificatio
n
Identification discrimination
% (N)
% (N)
% (N)
96.5 (111)
0.86 (1)
0.86 (1)*
Unidentified
% (N)
1.7 (2)
* N.meningitidis
Conclusion
The new Vitek 2 NH card could be considered a reliable and useful tool for routine use in the rapid NG identification, which would otherwise require testing with multiple
systems.
Our results confirm the findings published by others authors.
References
Alexander,S;Ison,C. Evaluation of commercial kits for the identification of Neisseria gonorrhoeae.J Med Microbiol.54:827-831.2005.
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Funke,G; Desmonceaux,M;Perrot,N; Rogert-Dalbert,C; Bourgeois,C; Pincus,D; Chatellier,S. 2006. Performande of the new Vitek 2 NH card in a routine clinical laboratory, abstr.C-010,Abstr, 106tn Gen Meet.Am.Soc Microbiol. American Society for Microbiolgy, Washington,DC.
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American Society for Microbiolgy, Washington,DC.
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Rennie,R; Brosnikoff,C; Shokoples,S; Reller,L; Mirrett,S; Janda,W; Ristow,K; Krilcich,A. Multicenter evaluationof the new Vitek 2 Neisseria-Haemophilus identification card. J Clin Microbiol. 8:2681-2685.2008