Contagious equine metritis eradicated from Japan.

Contagious equine metritis (CEM), a contagious venereal disease of horses, invaded Japan in 1980 and spread in the Thoroughbred population of the Hidaka-Iburi district of Hokkaido. To eradicate CEM, we ran a program aimed at detecting Taylorella equigenitalis, the causal agent, in carrier horses by using the PCR test, followed by culling or treatment. In 2001, the first year of the program, 12,356 Thoroughbred racing stallions and mares were tested and 11 carriers were found. Four, two, one, and one carrier mares were detected in 2002, 2003, 2004, and 2005, respectively, by application of the program at the same scale as in 2001. No PCR-positive horses were found from 2006 to 2010. These results strongly suggest that CEM was eradicated from Japan by 2010.

Bending loss of elliptical-hole core circular-hole holey fibers bent in arbitrary bending directions.

A holey fiber having a core with an elliptical-hole lattice structure, which is referred to as an elliptical-hole core circular-hole holey fiber (EC-CHF), can be easily designed as a single-polarization fiber by using the fundamental space-filling modes of the core and cladding lattices. However, because the guided mode in an EC-CHF has a polarization that arises from the large geometric anisotropy of the core lattice, the influence of the bending direction on the bending loss is a crucial issue for the practical implementation of EC-CHFs. Here, the bending losses of an EC-CHF bent in arbitrary angular orientations with respect to the core cross section are calculated numerically using the equivalent anisotropic step-index circular fiber model for a real EC-CHF, and the influence of the bending direction of the fiber on the bending loss is discussed.

Genetic variation among Staphylococcus aureus strains from bovine milk and their relevance to methicillin-resistant isolates from humans.

In genetic analysis of bovine Staphylococcus aureus isolates that are recognized as an important pathogenic bacterium in bovine mastitis, multilocus sequence typing (MLST) showed strong correlation to the results of pulsed-field gel electrophoresis, coa PCR-restriction fragment length polymorphism (RFLP), spa typing, and the coagulase serotyping method. According to MLST results, strains derived from sequence type 97 (ST97) and ST705 were suggested as not only dominant bovine S. aureus lineages in Japan but also pandemic bovine S. aureus lineages. Although both lineages seem to be distantly related to each other by phylogenetic analysis, both had common characteristics, i.e., lukM/lukF'-PV and coagulase serotype VI. These characteristics were very rare among minor bovine strains and human strains and may contribute to the host specificity of these lineages. Four methicillin-resistant S. aureus (MRSA) isolates were first confirmed from bovine milk in Japan; these isolates showed geno- and serotypes that were identical or similar to those of human MRSA isolates in Japan (ST5, staphylococcal cassette chromosome mec type II [SCCmec II], Spa type t002 or t375, and coagulase serotype II, and ST89, SCCmec IIIa, Spa type t5266, and coagulase serotype I). ST5 and ST89 are uncommon among bovine isolates in the world, whereas these STs are common among human MRSA isolates in Japan.

Epidemiological analysis of Staphylococcus aureus isolated from cows and the environment of a dairy farm in Japan.

A case of Staphylococcus aureus intramammary infection (IMI) on a Japanese dairy farm was monitored for 9 months. S. aureus isolates from cows and environmental samples consisted of specific strains with sequence types 352 and 705, as determined by multilocus sequence typing. Clonal strains of these sequence types are isolated from cows worldwide, indicating that they are adapted to the bovine environment. These results explain why many IMI cases are persistent and lead to subclinical mastitis. The strain isolated from milk was identical to those isolated from the cows' bodies and cows carrying S. aureus, milking units, personnel, heifers and cats in the dairy barn. These locations and factors should be emphasized as sources and routes of strains causing IMI.

Anomaly of mode field in multistep index profile multimode fiber.

A remarkable anomaly of a mode field in multistep-index multimode fibers was observed. It is demonstrated by a finite-element modal analysis that the highest field peak locations of guided modes with the anomaly shift toward the core-cladding boundary drastically.

Squeezed lattice elliptical-hole holey fiber with extremely high birefringence.

A novel highly flat elliptical-hole holey fiber with a squeezed lattice is introduced for achieving extremely high birefringence. The fiber consists of two kinds of elliptical holes with the same major axis length and different minor axis lengths for the core and cladding regions. Numerical results demonstrate a modal birefringence exceeding 0.065.

Serotyping of Mannheimia haemolytica isolates from bovine pneumonia: 1987-2006.

Over a period of 20 years, a total of 207 Mannheimia haemolytica samples were isolated from calves affected with pneumonic pasteurellosis and serotyped by the indirect haemagglutination test. Serotypes A1 (102 isolates), A2 (47 isolates) and A6 (42 isolates) were most common; in addition, 16 isolates were serotypes A7, A13, A14 or untypable. The relative prevalence of serotype A6 has increased recently in Japan, as has been reported from other countries. The results of this study provide useful information towards the design of efficient vaccines for the prevention of M. haemolytica infection in Japan.

Single-mode single-polarization holey fiber using anisotropic fundamental space-filling mode.

We present the single-mode single-polarization regime of a circular-hole holey fiber consisting of a core with large elliptical holes. The elliptical holes in the core, which produce large anisotropies, split the fundamental mode into two orthogonally polarized fundamental modes, often referred to as slow and fast modes. This fiber can guide only one polarization state of the fundamental mode when a fundamental space-filling mode index of the cladding region is designed to lie between these indices of the slow and fast modes of the core region. We demonstrate one design example of this fiber and show that the single-polarization regime can be achieved over a wide wavelength range.

Characteristics and epidemiologic genotyping of Staphylococcus aureus isolates from bovine mastitic milk in Hokkaido, Japan.

Two hundred thirty one Staphylococcus aureus isolates from bovine mastitic milk were discriminated into 60 patterns and 16 lineages by pulsed-field gel electrophoresis (PFGE). The tested isolates were also investigated using coagulase and capsule serotyping and PCR for possession of genes that encode staphylococcal enterotoxins (sea to sei), enterotoxin-like toxins (selj to selr), and toxic shock syndrome toxin (tst). One hundred seventy three of the isolates (74.9%) possessed one or more toxin genes, while no egg-yolk factor was detected in most of them. The most common combinations of toxin genes possessed by the tested isolates were sec, seg, sei, sell, and tst, or seg and sei, or sec, seg, sei, sell, seln, and tst. Two hundred and ten of the isolates (91.0%) serotyped coagulase VI, and 207 of the isolates (89.6%) expressed serotype 5 or 8 capsules. These results suggested that isolates belonging to two major lineages have spread all over Hokkaido as bovine mastitic isolates. Additionally, no remarkable difference was recognized in the identification ratio of the isolates that belonged to the two major lineages between mastitis of subclinical origin and mastitis of clinical origin.

Numerical analysis of modal dispersion in graded-index plastic optical fibers.

Modal dispersion properties of a fabricated plastic optical fiber are numerically calculated through a finite-element method. The modal index, group delay, impulse response, and output pulse shape are compared with those for the power-law profile plastic optical fiber; the influence of index profile deviations from the power-law profile is described. It is shown that index profile fluctuations in the actual index profile strongly affect the group delays, even though they are relatively small. On the other hand, they have little effect on the modal indices.

Macrolides and lincomycin susceptibility of Mycoplasma hyorhinis and variable mutation of domain II and V in 23S ribosomal RNA.

A total of 151 strains of Mycoplasma hyorhinis isolated from porcine lung lesions (weaned pigs, n=71, and finishers, n=80) were investigated for their in vitro susceptibility to 10 antimicrobial agents. Thirty-one strains (28 from weaned pigs and 3 from finishers) showed resistance to 16-membered macrolide antibiotics and lincomycin. The prevalence of the 16-membered macrolide-resistant M. hyorhinis strain in weaned pigs from Japanese herds has approximately quadrupled in the past 10 years. Several of the 31 strains were examined for mutations in the 23S ribosomal RNA (rRNA). All field strains tested showed a transition of A to G at position 2059 of 23S rRNA-rendered Escherichia coli. On the other hand, individual tylosin- and lincomycin-resistant mutants of M. hyorhinis were selected in vitro from the susceptible type strain BTS7 by 3 to 9 serial passages in subinhibitory concentrations of each antibiotic. The 23S rRNA sequences of both tylosin and lincomycin-resistant mutants were compared with that of the radical BTS7 strain. The BTS7 mutant strain selected by tylosin showed the same transition as the field-isolated strains of A2059G. However, the transition selected in lincomycin showed mutations in domains II and V of 23S rRNA, G2597U, C2611U in domain V, and the addition of an adenine at the pentameric adenine loop in domain II. The strain selected by lincomycin showed an additional point mutation of A2062G selected by tylosin.

Leukotoxin family genes in Staphylococcus aureus isolated from domestic animals and prevalence of lukM-lukF-PV genes by bacteriophages in bovine isolates.

Leukotoxin family genes in Staphylococcus aureus isolated from domestic animals were examined by polymerase chain reaction. LukS and lukF genes were detected in all 48 avian and 72 porcine isolates of S. aureus. LukE and lukD genes, located in a putative staphylococcal pathogenicity island (Sapln3/Saplm3), were recognized in 44 (91.7%) of 48 avian isolates, but these genes were not detected in porcine isolates. In 297 bovine isolates collected from mastitic cow's milk and bulk milk from dairy farms in two regions, lukM and lukF-PV(P83) genes in addition to lukS-lukF and lukE-lukD genes were detected in 100 (62.5%) of the 160 isolates from Ishikawa and in118 (86.1%) of the 137 isolates from Hokkaido. When the lysogeny of S. aureus bovine isolates was examined by treatment with mitomycin C, clearing of the culture due to cell lysis was observed in 34 (91.9%) of 37 lukM-lukF-PV(P83) genes--positive isolates. In addition, we isolated a novel lukM-lukF-PV(P83)-carrying (designated phiLukM), and revealed that the lukM-lukF-PV(P83) genes were located very close to an amidase gene on the temperate phage genomes. These results suggest horizontal transmission of lukM-lukF-PV(P83) genes by temperate bacteriophages in S. aureus of bovine origin.

Molecular typing of Staphylococcus aureus isolated from bovine mastitic milk on the basis of toxin genes and coagulase gene polymorphisms.

A total of 270 strains of Staphylococcus aureus, isolated from mastitic milk, were investigated by the polymerase chain reaction for the presence of genes encoding enterotoxins (sea to sej) and a toxic shock syndrome toxin (tst). One hundred eighty three (67.8%) bovine isolates possessed either one or more toxin genes and the most common pattern that coexisted in S. aureus was tst, sec, seg, and sei. Coagulase genotyping revealed 15 patterns, and 161 of the 270 isolates (59.6%) belonged to the coagulase genotype B1. Further, these 161 isolates possessed at least two enterotoxin genes. However, the role of these toxins in udder pathogenicity remains unclear. Moreover, the predominant isolate possessed the enterotoxin genes supporting the theory that superantigenic toxins are important for the udder pathogenesis.

All propagation modes of large-core multimode optical fibers with an arbitrary core profile.

Plastic optical fibers are typical large-core multimode optical fibers. High-bandwidth graded-index plastic optical fibers, which support a great number of propagation modes compared with conventional silica-glass multimode optical fibers, were developed in the 1990s. However, because they support a great number of propagation modes, their modal analyses have been limited to the WKB analysis. We obtain all the propagation modes of a convex-index large-core multimode optical fiber by use of the finite-element method, which has a strong advantage for arbitrary core profiles.

Finite-element modal analysis of large-core multimode optical fibers.

Plastic optical fibers that are a typical large-core multimode optical fiber support a great number of modes compared with conventional silica-glass multimode optical fibers. So far the WKB method hasbeen used for most of the modal analyses of these fibers because of a great number of guided modes. We describe the accurate eigenmodal analysis of large-core multimode optical fibers with the finite-element method (FEM) and compute the propagation constants of all LP modes. In addition, the FEM has a strong advantage for arbitrary core profiles whereas the WKB method is not suitable fornonmonotonic profiles. To demonstrate the advantage, we apply the FEM to the fiber having sinusoidal fluctuations.

Prevalence and characteristics of eae-positive Escherichia coli from healthy cattle in Japan.

The prevalence of eae-positive Escherichia coli (eaeEC) in Japan was examined using rectal stool samples taken from 35 calves less than 1 month old, 107 calves more than 1 to 3 months old, 88 heifers more than 3 to 6 months old, 214 heifers over 6 months old, and cows from 95 farms. Screening with eae PCR revealed the prevalence to be, with increasing age, 31.4, 8.4, 26.1, and 14.5%, respectively. Of 51 selected eaeEC strains, more than 40% were serotyped as O26, O103, O111, O145, or O157, which are frequently detected as enterohemorrhagic E. coli types. Four strains were identified as recently reported intimin types eta, iota, and kappa.

Standards of the in vitro mutation frequency study and the antimicrobial activity study in gut.

In view of the recent rapid increase in incidence of infection with antimicrobial resistant bacteria in human medicine, there is international controversy as to the medical risk that is created by transfer of antimicrobial resistant bacteria and antimicrobial resistant genes, which may be produced through the processes of administration of antimicrobials to food-producing animals, via the food chain. Accordingly, International Cooperation on Harmonization of Technical Requirements for Registration of Veterinary Medicinal Products (VICH) provides the comprehensive guidelines for characterizing selection of antimicrobial resistance by bacteria which may adversely affect human health in order to establish the system of registry of antimicrobial drugs to be administered to food- producing animals. Currently, Japanese Society of Antimicrobials for Animals recognizes the lack of technical test standards in compliance with VICH guidelines in the world and has established the test standards for "in vitro mutation frequency studies" to evaluate the appearance frequency and resistant level of resistant bacteria and those for studies on the "antimicrobial activity in gut" to estimate the effects on intestinal flora from professional aspects.