pISSN 2466-1384 eISSN 2466-1392 大韓獸醫學會誌 (2017) 第 57 卷 第 3 號 Korean J Vet Res(2017) 57(3) : 201~204 https://doi.org/10.14405/kjvr.2017.57.3.201

Isolation and identification of cuniculi from a rabbit with keratoconjunctivitis

Dong-Kun Yang*, Ha-Hyun Kim, Jae-Young Yoo, Suk-Kyung Lim, Soon-Seek Yoon, In-Soo Cho Animal and Plant Quarantine Agency, Ministry of Agriculture, Food and Rural Affairs, Gimcheon 39660, Korea,

(Received: July 3, 2017; Revised: August 1, 2017; Accepted: August 10, 2017)

Abstract: A Gram-negative, catalase- and oxidase-positive, coccus-shaped bacterium was isolated from a rabbit with keratoconjunctivitis. Colonies of the isolate were round, smooth, and exhibited hemolytic activity on 5% sheep blood agar. Scanning electron microscopy revealed 0.4 to 0.5 μm diameter oval cocci. Partial 16S rRNA gene (1446 bp) sequence analysis demonstrated the isolate had significant homology with the Moraxella cuniculi CCUG2154 strain isolated from a rabbit in Germany in 1973. Our isolate was designated as APQAB1701. Antibiotic susceptibility tests demonstrated that APQAB1701 was sensitive to 24 antibiotics; 3 of the antibiotics (nalidixic acid, spectinomycin, and colistin) had minimal inhibitory concentrations ≥ 32 µg/mL against the isolate. Keywords: Moraxella cuniculi, identification, isolation, rabbits

The genus Moraxella is a Gram-negative bacterium that farm. Three swab samples were collected from around eye- causes opportunistic infection in humans and animals [6]. lid of the infected rabbit and other seven samples were also Morphologically, Moraxella species are short rods or cocco- collected from two rabbits showing wasting disease. All bacilli, or in the case of Moraxella (M.) catarrhalis, diplo- swab samples were cultured on blood and chocolate agar cocci. In humans, M. catarrhalis is the best-known Moraxella plates to isolate . The plates were incubated for 24 h spp. [7]. M. lacunata and M. osloensis have been reported to at 37oC. The colonies were passed three times to obtain pure cause blepharoconjunctivitis and hematological malignan- colonies and tested using Gram staining and catalase and oxi- cies in humans [3, 6]. In veterinary medicine, M. bovis is the dase tests. The morphology of the isolate was observed using causative agent of infectious bovine keratoconjunctivitis, which electron microscopy. Bacteria enriched in brain heart infu- is characterized by conjunctivitis, keratitis, corneal opacity, sion broth were fixed with 2% glutaraldehyde overnight, and and ulceration, a clinical syndrome called pinkeye [4, 10]. As with 1% osmium tetroxide in phosphate-buffered saline for 2 h. a strict aerobe, M. bovis is confined to the cornea and con- The fixed bacteria were coated with gold ions and then observed junctiva, resulting in a progressive, non-self-limiting keratitis, under a JSM/LV-6460 electron microscope (JEOL, Japan). ulceration and, ultimately, rupture of the cornea. The disease Genomic DNA was extracted from the isolated colonies is relatively common, infecting cattle worldwide, although using a genomic DNA extraction kit (iNtRON Biotechnology, there have been no reports of M. bovis or M. spp among Korea), according to the manufacturer’s instructions. PCR domestic animals in South Korea. In this study, we isolated was used to amplify the 16S rRNA gene using the forward and identified M. cuniculi from a rabbit with clinical kerato- primer 5'-AGA GTT TGA TCM TGG CTC AG-3' and conjunctivitis and named the isolate APQAB1701. This reverse primer 5'-TAC CGY TAC CTT GTT ACG ACT T-3'. study investigated the biological/morphological characteris- The sequencing reactions were performed in a DNA Engine tics and antibiotic resistance of the APQAB1701 isolate. Tetrad 2 Peltier Thermal Cycler (Bio-Rad Laboratories, USA) A disease associated with conjunctivitis and congestion of using the ABI BigDye(R) Terminator v3.1 Cycle Sequenc- the eyelid was reported in a 1-year-old rabbit raised on a ing Kit (Applied Biosystems, USA), following the manufac- farm in Gyeongsang Province, Korea, in 2017. The farm turer’s protocols. Single-pass sequencing was performed with raising about 200 rabbits had morbidity rate of 1 to 2%, and each template using sequencing primers (forward 5'-GGA the mortality rate was close to zero. The farm had one rabbit TTA GAT ACC CTG GTA-3', reverse 5'-CCG TCA ATT with conjunctivitis and hyperplasia of the eyelid. Ten swab CMT TTR AGT TT-3'). The fluorescent-labeled fragments samples from three rabbits were collected from the rabbit were purified using the method recommended by Applied

*Corresponding author Tel: +82-54-912-0785, Fax: +82-54-912-0812 E-mail: [email protected] 201 202 Dong-Kun Yang, Ha-Hyun Kim, Jae-Young Yoo, Suk-Kyung Lim, Soon-Seek Yoon, In-Soo Cho

Table 1. Results of antibiotic resistance of Moraxella cuniculi, APQAB1701 Antibiotics MIC (µg/mL) Antibiotics MIC (µg/mL) Amoxicillin < 2 Gentamicin < 1 Ampicillin < 0.25 Neomycin < 2 Penicillin < 0.12 Streptomycin 8 Cefoxitin 4 Spectinomycin 64 Ceftiofur 1 Tetracycline < 2 Cephalothin < 2 Chlortetracycline < 0.5 Clindamycin < 0.25 Oxytetracycline < 0.5 Ciprofloxacin < 0.12 Trimethoprim < 0.12 Danofloxacin < 0.12 Sulfadimethoxine < 256 Enrofloxacin < 0.12 Tiamulin 1 Nalidixic Acid 32 Tilmicosin < 4 Colistin > 32 Tulathromycin 8 Florfenicol 4 Tylosin 2 Chloramphenicol 8 MIC, minimum inhibition concentration.

cosin, tulathromycin, and tylosin. Fig. 1. One eye of the rabbit showed severe keratoconjunctivitis Figure 1 shows the rabbit with severe conjunctivitis and and hyperplasia (A), and the other eye was blinded by inflam- mation (B). Pure isolation of Moraxella cuniculi isolated on hyperplasia around the eyelid. Three pure colonies were iso- chocolate agar (C); the isolate was hemolytic on a 5% sheep lated from four samples obtained from the rabbit cultured on blood agar plate (D). Morphology of the Moraxella cuniculi blood and chocolate agar plates. The nucleotide sequences of APQAB1701 isolated on scanning electron microscopy. The the three colonies identified them as M. cuniculi, Pasteurella bacteria were oval and measured 0.4 to 0.5 µm in diameter (E multocida, and Corynebacterium spp. We named the M. and F). cuniculi isolate APQAB1701 and investigated its biochemi- cal characteristics and morphological features. The isolate was Biosystems, as it removes the unincorporated terminators and Gram-negative, catalase-positive, oxidase-positive, and aero- dNTPs. The samples were subject to electrophoresis in an bic. Colonies of the isolate were circular, smooth, and hemolytic ABI 3730xl DNA Analyzer (Applied Biosystems). The on 5% sheep blood agar (Fig. 2). Morphologically, the iso- nucleotide sequences and accession numbers of the strains late consisted of oval cocci measuring 0.4 to 0.5 µm in diam- used for the phylogenetic analysis were obtained from the eter on electron microscopy (Fig. 1). A 1,446-nucleotide GenBank database (National Center for Biotechnology Infor- partial 16S rRNA gene sequence was determined for the mation, USA). The partial nucleotide sequence of the 16S APQAB1701 isolate and compared with partial 16S rRNA rRNA genes obtained from the isolate was compared with gene sequences of 35 other bacteria obtained from Gen- those of known bacteria using Clustal W 2 [2]. Genetic dis- Bank. The nucleotide sequence analysis showed that the tances were calculated using the Kimura 2-parameter model, APQAB1701 isolate shared identical homology with the and a phylogenetic tree was constructed using the neighbor- CCUG2154 strain, which was isolated from a rabbit in Ger- joining method with 1,000 bootstrap replicates in MEGA6 many in 1973, and had 97% similarity with M. bovis (acces- software [8]. sion No. AF005183) (Fig. 2). The antimicrobial susceptibility To evaluate antibiotic resistance, minimal inhibitory con- of the isolate was tested with standard broth dilution meth- centrations (MICs) were determined on KRNV4F and BOPOGF ods. The isolate was sensitive to 24 antibiotics, and 3 antibi- MIC plates (Trek Diagnostic Systems, USA) using the stan- otics (nalidixic acid, spectinomycin, and colistin) had MICs dard broth dilution methods described in the Clinical and ≥ 32 µg/mL against the isolate (Table 1). Laboratory Standard Institute guidelines for the following 27 Most Moraxella species except M. bovis are considered to antibiotics: amoxicillin/clavulanic acid, ampicillin, penicillin, be part of the normal mucosal flora of humans and animals. cefoxitin, ceftiofur, cephalothin, clindamycin, ciprofloxacin, The Moraxella species implicated in a variety of conditions danofloxacin, enrofloxacin, nalidixic acid, colistin, florfenicol, in humans and domestic animals are frequently found in chloramphenicol, gentamicin, neomycin, streptomycin, spec- mixed bacterial or viral infections [1, 9]. In our study, M. tinomycin, tetracycline, chlortetracycline, oxytetracycline, tri- cuniculi was isolated with P. multocida, and Corynebacte- methoprim/sulfamethoxazole, sulfadimethoxine, tiamulin, tilmi- rium sp., indicating that the bacterium was an opportunistic Isolation and identification of Moraxella cuniculi from rabbit 203

Fig. 2. Phylogenetic tree based on 1446 bp of the 16S rRNA gene. The isolate, APQAB1701, had a 100% similarity with CCUG2154T which was isolated from a German rabbit in 1973. pathogen associated with eye disease. Several Moraxella spe- study was susceptible to 24 antibiotics, and the rabbit infected cies are reported to hemolyze sheep blood, including M. with mixed bacteria containing M. cuniculi will be treated bovis, M. canis, M. caprae, M. caviae, and M. boviae, but not after performing antibiotic susceptibility tests on the collected M. cuniculi [6, 9]. In our study, the M. cuniculi, APQAB1701 samples. isolate showed hemolytic activity on 5% sheep blood agar, In conclusion, we report the identification of M. cuniculi indicating that M. cuniculi produces a hemolysin and should isolated from a Korean rabbit. These findings indicated that be considered pathogenic. Furthermore, it is necessary to M. cuniculi had hemolytic activity in relation to conjunctivi- identify genes encoding potential virulence factors, such as tis and hyperplasia of the eyelid in a rabbit. This study did phospholipases, outer membrane protein and proteolytic not demonstrate the virulence of M. cuniculi. It is therefore enzymes [5]. The 16S rRNA sequence analysis of bacteria is necessary that future studies investigate the virulence of the a reliable method that can be applied for species identifica- isolate in normal rabbit. tion [6, 9]. The pure isolate, APQAB1701 was confirmed to be M. cuniculi, as it showed 100% homology with the Acknowledgments CCUG2154 strain isolated from a rabbit in Germany in 1973. Regarding treatment, the M. cuniculi isolate described in this This work was supported financially by a grant (N1543083- 204 Dong-Kun Yang, Ha-Hyun Kim, Jae-Young Yoo, Suk-Kyung Lim, Soon-Seek Yoon, In-Soo Cho

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