Pyelonephritis caused by Mannheimia varigena in a Holstein calf.

A 7-day-old calf died following development of mild respiratory symptoms. Postmortem examination revealed the kidneys were inflamed, and Gram-negative bacteria was detected in the kidneys, supporting the diagnosis of suppurative pyelonephritis. Mannheimia varigena antigen was found in the lesions and the cytoplasm of macrophages and neutrophils in the renal cortex. The Gram-negative bacilli from the kidney were identified as M. varigena by sequencing the 16S rDNA. Although M. varigena is known to cause bovine respiratory disease syndrome, shipping fever, and meningitis, it was unknown that it could also cause suppurative pyelonephritis. Our study provides the first evidence of suppurative pyelonephritis caused by M. varigena in cattle and information that would improve our understanding, diagnosis, and treatment for M. varigena infections.

Septicemic Actinobacillus suis infection in a neonatal piglet with multifocal necrotic glossitis.

Five-day-old neonatal piglets presented with debilitation and ananastasia. At the necropsy of one piglet, the apex of the tongue was found to be discolored dark red, and disseminated white foci were found on the cut surface. Many white foci were also found in the lungs and on the serosa of the liver and spleen. Histopathological findings revealed multifocal necrotic glossitis and pneumonia with Gram-negative bacilli. The bacilli were identified as Actinobacillus suis through immunohistochemical, biochemical, and genetic tests, including 16S rRNA gene sequencing. Although A. suis usually causes inflammation in thoracic and abdominal organs, lesions were also found in the tongue in the present case. This study is the first report of glossitis caused by A. suis.

Bovine vegetative endocarditis caused by Streptococcus suis.

A 5-month-old crossbred beef steer died after exhibiting astasia. A postmortem examination revealed verrucous endocarditis and numerous renal hemorrhages. Gram-positive bacteria were identified in the necrotic lesions of the verruca and mitral valve via histopathological analysis. Multifocal necrosis and hemorrhage were detected in the renal cortex. Gram-positive cocci isolated from the verruca were identified via biochemical tests and 16S rRNA gene sequence analysis as Streptococcus suis. Serotyping indicated that the S. suis isolates were untypable, following which these isolates were classified as a new sequence type (ST1000) via multi-locus sequence typing. S. suis is an important pathogen of pigs. However, clinical cases in cattle are rare. This report is intended to provide information that may be useful in the diagnosis of streptococcal disease in cattle.

A frameshift mutation in the rRNA large subunit methyltransferase gene rlmA II determines the susceptibility of a honey bee pathogen Melissococcus plutonius to mirosamicin.

American foulbrood (AFB) and European foulbrood (EFB) caused by Paenibacillus larvae and Melissococcus plutonius, respectively, are major bacterial infections of honey bees. Although macrolides (mirosamicin [MRM] and tylosin) have been used to prevent AFB in Japan, macrolide-resistant P. larvae have yet to be found. In this study, we revealed that both MRM-resistant and -susceptible strains exist in Japanese M. plutonius and that a methyltransferase gene (rlmA II ) was disrupted exclusively in MRM-susceptible strains due to a single-nucleotide insertion. The M. plutonius RlmAII modified G748 of 23S rRNA, and the deletion of rlmA II resulted in increased susceptibility to MRM and the loss of modification at G748, suggesting that methylation at G748 by RlmAII confers MRM resistance in M. plutonius. The single-nucleotide mutation in MRM-susceptible strains was easily repaired by spontaneous deletion of the inserted nucleotide; however, intact rlmA II was only found in Japanese M. plutonius and not in a Paraguayan strain tested or any of the whole-genome-sequenced European strains. MRM has been used in apiculture only in Japan. Although M. plutonius is not the target of this drug, the use of MRM as a prophylactic drug for AFB may have influenced the antibiotic susceptibility of the causative agent of EFB.

Population structure and antimicrobial susceptibility of Paenibacillus larvae isolates from American foulbrood cases in Apis mellifera in Japan.

Paenibacillus larvae is the causative agent of American foulbrood (AFB), the most destructive disease of the honey bee brood. In this study, we investigated the population structure and antimicrobial susceptibility of Japanese P. larvae using 100 isolates isolated between 1993 and 2017 in 17 prefectures. Using repetitive-element PCR and multilocus sequence typing, isolates from diverse origins were classified into six genotypes, including the novel genotype ERIC II-ST24. Among these genotypes, ERIC I-ST15 is the most common in Japan, while ERIC II-ST10 isolates were found to be increasing during the 2010s. Regardless of genotype or origin, all isolates were susceptible to the major antimicrobials used in the control of AFB, including mirosamicin and tylosin, which were approved for the prevention of AFB in Japan in 1999 and 2017 respectively. Despite nearly 20 years of use, mirosamicin is still effective against Japanese P. larvae in vitro; however, the development of AFB in honey bee colonies may not always be suppressed by this drug. The case information collected in this study provides insight into the conditions under which prophylactic medicine may not exert sufficient preventive effects in vivo.