Pasteurella species are small, nonmotile, gram-negative, bipolar-staining facultative anaerobes present in the oropharynx of the majority of healthy dogs and cats, and are the causative agents of zoonotic infections in humans 1234567. The frequent occurrences of infections due to Pasteurella species have been documented to date accompanied by the recent popularity of pets. Indeed, human pasteurellosis are most often caused by dog and cat bites, resulting in cellulitis and subcutaneous abscesses 8910. Pasteurella species are infrequently caused systemic infectious diseases and mostly strike in patients with underlying diseases. P. multocida is the most recurrent species in human infections 11, but other species may be involved, such as P. canis, and P. dagmatis 712. Automated systems are generally used for the identification of Pasteurella isolates. 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 rare case of dual infections due both to P. canis and to P. dagmatis, focusing on the limitations of automated Vitek 2 system using GN cards (Nippon sysmex bio-Mérieux, Co., Ltd., Tokyo, Japan) as well as commercially available kit system, ID-Test HN20 rapid panels (Nissui Pharmaceutical Co., Ltd., Tokyo, Japan), for exact identification of Pasteurella species.

A previously healthy 25-year-old female patient was admitted to the department of emergency and critical care in Azumino Red Cross Hospital, Azumino, 3998292, Japan on March 3 in 2010. She complained of a severe inflammation accompanied by sensations of burning along the circumference of thumb root part in her left hand. She was bitten by her pet dog two days before, and her injured area was 15 mm in length and 10 mm in depth. An X-ray examination on her admission manifested that she had no fracture of the bones. Skin examination of her left hand revealed inflammation, swelling, and sharp pain without purulent discharges. No regional lymphadenopathy was noted. Two distinctive Pasteurella isolates were recovered as the causative agents. After treating the injured area with the gentamicin-ointment, she was initially administered for 3 days with cefazolin (1 g) as intravenous drip infusion, and then switched to oral administration of cefcapene pivoxil (300 mg/day) therapy for additional 5 days. Her skin inflammation, swelling, and tenderness disappeared, but she felt a slight sensation at the injured site on 9 March in 2010, and she continued the oral administration of cefcapene pivoxil (300 mg/day) until her last consultation on 12 March in 2010, when she was confirmed the complete recovery.

Pasteurella species, causative agents of zoonotic infections in humans, are the inhabitants in the oropharynx of the majority of healthy dogs and cats 1234567. Indeed, they have been isolated from 20 to 30% of dog-bite wounds and more than 50% of cat-bite wounds 15. Most Pasteurella infections occur in people who have frequent contact with pet animals 7. Among the Pasteurella species, recently described species of the organism, called P. dagmatis, has previously been known as Pasteurella "gas", Pasteurella new species 1 or Pasteurella pneumotropica type Henriksen that is rarely implicated in human pathology 716. However, P. dagmatis is often isolated simultaneously with other bacteria 17, and misidentification may have contributed to the slightly underestimated frequency of its isolation 18. Pasteurella acquired from pets may cause a variety of infections, including tonsillitis, sinusitis, and epiglottiditis 1920. We report a rare case of P. dagmatis infection together with P. canis resulting from a dog bite.

To the best of our knowledge, this is the sixth human case report of P. dagmatis isolation. The incidence of P. dagmatis infection has been increasing in many countries. The previously described five cases were as follows; one case was P. dagmatis endocarditis, occurred in a healthy man after a cat-bite 21, the second case was complicated by vertebral osteomyelitis, involved the native mitral valve of a cirrhotic woman with a known history of animal contact 22, the third case was spondylodiscitis in a diabetic patient 23, the fourth case was a septicemia due to P. dagmatis in a diabetic patient 12, and the fifth case was a wound infection together with P. multocida resulting from a cat bite 24. The above five cases demonstrated that continuous contact with small animals such as dogs or cats might be a risk factor for transmission of Pasteurella species for humans. Our sixth case was also apparently associated with a dog bite.

As far as we can predict, the dual or simultaneous infectious diseases due to two different Pasteurella species have been documented only once in 1988, just descrived above as the fifth case 24). That is to say, our case report caused by both P. canis and P. dagmatis was the second to be documented, to the best of our knowledge.

The three isolates of Gram-negative coccobacilli with positive catalase and oxidase reactions were finally identified as P. dagmatis for strain-A, P. canis for strain-B, and P. canis for strain-C, respectively. ID-Test HN20 panels correctly identified strain-A as 100% P. dagmatis, but misidentified both the strain-B and strain-C as 100% P. multocida. On the contrary, Vitek 2 GN cards (Nippon sysmex bio-Mérieux) misidentified the strain-A as P. pneumotropica, but correctly identified both the strain-B and strain-C as P. canis.

The species name P. pneumotropica in the Vitek 2 system database (Nippon sysmex bioMérieux) might be P. dagmatis, formerly known as P. pneumotropica type Henricksen. It is with this fact that the Vitek 2 system database (Nippon sysmex bioMerieux) contained only P. multocida, P. canis, P. aerogenes, and P. pneumotropica for identification, and P. dagmatis was not included in the database until now. Suggestions should be made to manufacturers to improve their database; however, it is also important for routine clinical microbiology laboratories to know the limitation of the commercial identification systems, such as Vitek 2 (Nippon sysmex bioMérieux) and ID-Test HN20 rapid systems (Nissui Pharmaceutical). As not every laboratory has equipped to handle molecular assays, it will certainly help clinical microbiologists to remember that differential biochemical properties of oxidase, catalase, ornithine decarboxylase, urease activity, and indole production as shown in Table 4, fermentation of maltose, mannose, sucrose, and glucose are given by ID-Test HN20 panels (Nissui Pharmaceutical) or Vitek 2 GN cards (Nippon sysmex bioMérieux).

In addition, although ID-Test HN20 Rapid panels (Nissui Pharmaceutical) actually contained P. canis in the database, strain-B and strain-C were both misidentified as P. multocida. These findings apparently indicated that widely used identification systems prove to be unreliable in the accurate identification of Pasteurella species, especially P. dagmatis. Therefore, the remarkably underestimated frequency of isolation of P. dagmatis may possibly be ascribed to the misidentification of the species.

The authors declare that they have no competing interests.