Ribotyping and restriction endonuclease analysis reveal a novel clone of Bordetella bronchiseptica in seals

Comparison of ribotyping and sequence-based typing for discriminating among isolates of Bordetella bronchiseptica

PvuII ribotyping and MLST are each highly discriminatory methods for genotyping Bordetella bronchiseptica, but a direct comparison between these approaches has not been undertaken. The goal of this study was to directly compare the discriminatory power of PvuII ribotyping and MLST, using a single set of geographically and genetically diverse strains, and to determine whether subtyping based on repeat region sequences of the pertactin gene (prn) provides additional resolution. One hundred twenty-two isolates were analyzed, representing 11 mammalian or avian hosts, sourced from the United States, Europe, Israel and Australia. Thirty-two ribotype patterns were identified; one isolate could not be typed. In comparison, all isolates were typeable by MLST and a total of 30 sequence types was identified. An analysis based on Simpson's Index of Diversity (SID) revealed that ribotyping and MLST are nearly equally discriminatory, with SIDs of 0.920 for ribotyping and 0.919 for MLST. Nonetheless, for ten ribotypes and eight MLST sequence types, the alternative method discriminates among isolates that otherwise type identically. Pairing prn repeat region typing with ribotyping yielded 54 genotypes and increased the SID to 0.954. Repeat region typing combined with MLST resulted in 47 genotypes and an SID of 0.944. Given the technical and practical advantages of MLST over ribotyping, and the nominal difference in their SIDs, we conclude MLST is the preferred primary typing tool. We recommend the combination of MLST and prn repeat region typing as a high-resolution, objective and standardized approach valuable for investigating the population structure and epidemiology of B. bronchiseptica.

The 2000 Canine Distemper Epidemic in Caspian Seals (Phoca caspica): Pathology and Analysis of Contributory Factors

More than 10,000 Caspian seals ( Phoca caspica) were reported dead in the Caspian Sea during spring and summer 2000. We performed necropsies and extensive laboratory analyses on 18 seals, as well as examination of the pattern of strandings and variation in weather in recent years, to identify the cause of mortality and potential contributory factors. The monthly stranding rate in 2000 was up to 2.8 times the historic mean. It was preceded by an unusually mild winter, as observed before in mass mortality events of pinnipeds. The primary diagnosis in 11 of 13 seals was canine distemper, characterized by broncho-interstitial pneumonia, lymphocytic necrosis and depletion in lymphoid organs, and the presence of typical intracytoplasmic inclusion bodies in multiple epithelia. Canine distemper virus infection was confirmed by phylogenetic analysis of reverse transcriptase-polymerase chain reaction products. Organochlorine and zinc concentrations in tissues of seals with canine distemper were comparable to those of Caspian seals in previous years. Concurrent bacterial infections that may have contributed to the mortality of the seals included Bordetella bronchiseptica (4/8 seals), Streptococcus phocae (3/8), Salmonella dublin (1/8), and S. choleraesuis (1/8). A newly identified bacterium, Corynebacterium caspium, was associated with balanoposthitis in one seal. Several infectious and parasitic organisms, including poxvirus, Atopobacter phocae, Eimeria- and Sarcocystis-like organisms, and Halarachne sp. were identified in Caspian seals for the first time.

Novel, host-restricted genotypes of Bordetella bronchiseptica associated with phocine respiratory tract isolates

During a succession of phocine morbillivirus outbreaks spanning the past 25 years, Bordetella bronchiseptica was identified as a frequent secondary invader and cause of death. The goal of this study was to evaluate genetic diversity and the molecular basis for host specificity among seal isolates from these outbreaks. MLST and PvuII ribotyping of 54 isolates from Scottish, English or Danish coasts of the Atlantic or North Sea revealed a single, host-restricted genotype. A single, novel genotype, unique from that of the Atlantic and North Sea isolates, was found in isolates from an outbreak in the Caspian Sea. Phylogenetic analysis based either on MLST sequence, ribotype patterns or genome-wide SNPs consistently placed both seal-specific genotypes within the same major clade but indicates a distinct evolutionary history for each. An additional isolate from the intestinal tract of a seal on the south-west coast of England has a genotype otherwise found in rabbit, guinea pig and pig isolates. To investigate the molecular basis for host specificity, DNA and predicted protein sequences of virulence genes that mediate host interactions were used in comparisons between a North Sea isolate, a Caspian Sea isolate and each of their closest relatives as inferred from genome-wide SNP analysis. Despite their phylogenetic divergence, fewer nucleotide and amino acid substitutions were found in comparisons of the two seal isolates than in comparisons with closely related strains. These data indicate isolates of B. bronchiseptica associated with respiratory disease in seals comprise unique, host-adapted and highly clonal populations.

Respiratory disease associated with Bordetella bronchiseptica in a Hoffmann's two-toed sloth (Choloepus hoffmanni)

A 2-yr-old female captive-born Hoffmann's two-toed sloth (Choloepus hoffmanni) presented with respiratory disease. A severe inspiratory dyspnea with nasal congestion was observed with open-mouthed breathing and bilateral mucopurulent nasal exudate. Despite initial treatment with broad-spectrum antimicrobial therapy and anti-inflammatory and supportive care, the dyspnea persisted. The animal was anesthetized for bronchoscopy to obtain a deep tracheal sample. Based on culture of Bordetella bronchiseptica and sensitivity, a combination of systemic enrofloxacin, dexamethasone, and coupage with nebulization of saline, gentamicin, and albuterol as well as supportive care resulted in full recovery after 6 weeks of treatment.

Molecular and antigenic characterization of Bordetella bronchiseptica isolated from a wild southern sea otter (Enhydra lutris nereis) with severe suppurative bronchopneumonia

Bordetella bronchiseptica was isolated in pure culture from the lung, abdomen, and intestine of a wild free-ranging southern sea otter (Enhydra lutris nereis) with severe, suppurative bronchopneumonia. Immunohistochemistry, using antiserum raised to B. bronchiseptica, revealed strong positive staining of bacteria attached to bronchial ciliated epithelia as well as scattered positive staining in affected alveoli. Western blot analysis demonstrated that virulence factors, filamentous hemagglutinin, pertactin, and adenylate cyclase toxin are produced by the sea otter B. bronchiseptica isolate. Ribotype analysis using Pvu II restriction digests indicated that this isolate is most similar to strains commonly obtained in domestic dogs and cats.

Comparison of ribotyping and restriction enzyme analysis for inter- and intraspecies discrimination of Bordetella avium and Bordetella hinzii

Bordetella avium is an avian respiratory disease pathogen responsible for substantial economic losses to the turkey industry. The inability to distinguish isolates has hampered outbreak investigations and prevents a complete understanding of transmission mechanisms. Isolates of Bordetella hinzii, often referred to as B. avium-like or as Alcaligenes faecalis type II prior to 1995, have also been acquired from the respiratory tracts of diseased poultry but are not believed to be pathogenic for birds. Therefore, differentiating between B. avium and B. hinzii is of importance for veterinary diagnostic laboratories. It was recently reported that both PvuII ribotyping and HinfI/DdeI restriction endonuclease analysis (REA) show promise for distinguishing isolates of B. avium and B. hinzii. Here we compare the ability of these techniques to discern inter- and intraspecies differences. While both approaches distinguished numerous types within a species, only REA was sufficiently discriminatory for routine use as an epidemiologic tool. Both techniques clearly distinguish between B. avium and B. hinzii, although the results of ribotyping are more easily interpreted. Ribotyping and REA identified numerous, previously unrecognized B. hinzii strains from a collection of bordetella isolates, including one acquired from a rabbit. This is the first report of B. hinzii isolation from a nonhuman mammalian species. At least some of the newly recognized B. hinzii isolates have been previously reported to cause disease in poults, suggesting that the pathogenicity of this agent for poultry should be more rigorously examined.

Molecular epidemiology of feline bordetellosis in two animal shelters in California, USA

"Kennel cough" in dogs in animal shelters is readily transmissible, reduces adoption rates, and commonly leads to the euthanasia of affected dogs. In cats, tracheobronchitis, conjunctivitis, and pneumonia have been associated with Bordetella bronchiseptica infection-but most cases of upper-respiratory infection (URI) probably are caused by herpesvirus and calicivirus, and many B. bronchiseptica culture-positive cats are clinically normal. Our prospective observational study was undertaken to document the contribution of B. bronchiseptica to disease in cats and dogs from two animal shelters undergoing outbreaks of canine kennel cough, to evaluate whether cross-species transmission might have occurred, and to determine if the presence of infected cats represented a risk to dogs. Clinically defined cases of kennel cough in dogs and URI in cats were investigated in two shelters by calculating clinical-disease incidence, alveolar-lavage cytological examination, bacterial and viral cultures, antibiotic-susceptibility testing, and molecular fingerprinting by pulsed-field gel electrophoresis. In a 40-cat and 40-dog "no-kill" shelter, the prevalences of culture positivity were 47% for B. bronchiseptica and 36% for calicivirus at the same time as two resident dogs demonstrated clinical cough. When no dogs had kennel cough 3 months later, 10% of cats were B. bronchiseptica-culture-positive and 63% calicivirus positive. In a large traditional shelter, the incidence of kennel cough in dogs increased over 12 weeks to a maximum of 19 cases/week/120 dogs, during which time the culture prevalence was 23% for B. bronchiseptica in dogs and 47% in cats. Three to 6 months before the kennel-cough epidemic, no dogs or cats were B. bronchiseptica positive. Very little genetic variability was detected in isolates from these shelters; all isolates except one corresponded to a single strain type which was identical to the pattern in a vaccine used in these shelters. Isolates from other cats, a horse, a llama, and a sea otter were genetically distinct from the shelter isolates. There was widespread resistance to cephalosporins and ampicillin, but low or no resistance to amoxicillin/clavulanate, trimethoprim-sulfamethoxazole, tetracycline, and enrofloxacin. Greater percent resistance was observed in the traditional shelter than in the no-kill shelter and feline isolates were more likely to be resistant than canine isolates.

Restriction endonuclease analysis discriminates Bordetella bronchiseptica isolates

One hundred ninety-five Bordetella bronchiseptica isolates from 12 different host species worldwide were characterized by restriction enzyme analysis (REA). These isolates had previously been categorized into 19 PvuII ribotypes. Twenty restriction endonucleases were evaluated for use in REA. Digestion of chromosomal DNA with HinfI, followed by submarine electrophoresis in agarose gels and staining with ethidium bromide, produced DNA fragments in the 4.0- to 10-kb range, which readily discriminated B. bronchiseptica isolates, resulting in 48 fingerprint patterns. Moreover, AluI digestion of chromosomal DNA produced 39 distinct fingerprint profiles with DNA fragments ranging from 6.0 to 20.0 kb. While REA frequently provided more discriminatory power than ribotyping, there were examples where the use of ribotyping was more discriminatory than REA. Passage of selected isolates up to passage 25 did not change the REA profile. Moreover, the Bvg phase did not alter the fingerprint profile of chromosomal DNA from B. bronchiseptica strains digested with HinfI or AluI. Based on the results presented herein, the combination of REA and ribotyping should provide valuable information in understanding the molecular epidemiology of B. bronchiseptica infections.