Letter to the Editor
Dog bite wound infection by Pasteurella dagmatis
misidentified as Pasteurella pneumotropica by automated
system Vitek 2
To the Editor:
Human pasteurellosis are most often caused by dog and
cat bites, resulting in cellulitis and subcutaneous abscesses.
The second most common site of infection or colonization is
the respiratory tract. Systemic diseases are uncommon and
mostly occur in patients with underlying diseases. Pasteur-
ella multocida is the most frequent species in human
infections, but other species may be involved, such as Pas-
teurella canis, Pasteurella dagmatis,andPasteurella
stomatis (Allison and Clarridge, 2005; David et al., 1996;
Escande and Lion, 1993; Gautier-Lerestif et al., 2003; Holst
et al., 1992; Talan et al., 1999). Automated systems are
commonly used for Pasteurella identification. However, the
failure of commercial systems to satisfactorily identify
microorganisms is of concern, and unusual identification
should be correlated with patient's clinical pictures. We are
reporting here a case of misidentification of P. dagmatis by
automated system Vitek 2.
A 62-year-old man was admitted to the hospital with a
right forearm wound. He had been bitten 5 days before,
and the wound had been sutured. On examination, he was
apyrexial, though he was treated with paracetamol. Skin
examination of the right forearm revealed inflammation,
swelling, tenderness, and subcutaneous and necrotic
lesions with purulent discharges. No regional lymphadeno-
pathy was noticed. The patient was initially treated for 5
days with oral amoxicillin (3 g/day). He was switched to
levofloxacin (500 mg/day) therapy for 3 weeks. Swabs of
patient's wounds were cultured in chocolate agar supple-
mented with Polyvitex and horse blood agar (aerobically
and anaerobically). After 24 h at 37 °C, nonmotile colonies
of nonhemolytic Gram-negative coccobacilli with positive
catalase and oxidase were obtained. The isolate was
identified as 95% Pasteurella pneumotropica with very
good identification confidence level (biochemical profiles =
0001210350040201) by Vitek 2 GN card (ref 21341;
bioMérieux, Marcy l'Etoile, France) used as recommended
by the manufacturer. P. pneumotropica is usually found in
rodents, seldom in humans (in rodents-inflicted injuries). P.
pneumotropica is a routine test item of microbiologic
monitoring of laboratory mice and rats (Hayashimoto et al.,
2005). Considering these elements and clinical data of patients,
API 20E system (bioMérieux), using a 4-McFarland inoculum
after 18 h at 37 °C, was performed, and the isolate was
identified as 98.3% P. m u l t o c i d a (code number = 0044024)
with 0.94 of confidence level. Surprisingly, with regard to P.
multocida, the ornithine decarboxylase (ODC) assay was
negative and mannitol was not fermented. Urea was hydrolyzed
with the Vitek 2 GN card but not with the API 20E system. Urea
indole medium (bioMérieux) confirmed the urease production
by the isolate. The organism fermented maltose, sucrose, and
glucose but neither lactose nor mannitol, and it was urease
positive and ODC negative. Finally, considering the clinical
features and isolates, the biochemical profile identification of P.
dagmatis was suggested. Antibiotic susceptibility testing, using
a disk-diffusion technique on Mueller–Hinton agar with 5%
sheep blood, showed that this bacterium was susceptible to
amoxicillin, amoxicillin–clavulanic acid, cefotaxime, trimetho-
prim–sulfamethoxazole, ofloxacin, and erythromycin. Mole-
cular identification was then assessed by sequencing the
amplification products of 16S rRNA obtained with 515F and
1492R primers (Relman et al., 1992). The sequences
comparison with known 16S rRNA gene in the BIBI database
by BLAST search revealed 100% homology with P. dagmatis
strain AY362920 (Devulder et al., 2003).
Until now, the Vitek 2 system database contained only
P. multocida, P. canis, Pasteurella aerogenes, and P.
pneumotropica for identification. P. pneumotropica present
in the Vitek 2 system database may be P. dagmatis,
formerly known as P. pneumotropica type Henricksen.
Suggestions were made to manufacturers to improve their
database. It is also important for routine clinical micro-
biology laboratories to know the limitation of the
commercial identification systems. However, not every
laboratory has molecular assay capability. It will certainly
Available online at www.sciencedirect.com
Diagnostic Microbiology and Infectious Disease 65 (2009) 347 –348
www.elsevier.com/locate/diagmicrobio
Table 1
Phenotypic characteristics of P. dagmatis and P. pneumotropica
P. dagmatis P. pneumotropica
Catalase + +
Oxidase + +
ODC − +
Urease + +
Indole + +
ONPG − +
ONPG = ortho-nitrophenyl-β-
D
-galactopyranoside.
0732-8893/$ – see front matter © 2009 Elsevier Inc. All rights reserved.