Robert Higgins

Bio: Robert Higgins is an academic researcher from Université de Montréal. The author has contributed to research in topics: Streptococcus suis & Serotype. The author has an hindex of 45, co-authored 247 publications receiving 6360 citations. Previous affiliations of Robert Higgins include Veterinary Laboratories Agency & Laval University.

Description of 14 new capsular types of Streptococcus suis.

Abstract: Fourteen new capsular types of Streptococcus suis (types 9 to 22) are described. All reference strains are morphologically and biochemically similar to types previously described. Reference strain types 9 to 13, 15, 16, and 22 were isolated from diseased pigs, whereas types 17 to 19 and 21 came from clinically healthy pigs; type 14 was isolated from a human case of meningitis, and type 20 was isolated from a diseased calf. The group T streptococcus of de Moor has been included in the typing system as type 15. Two-way cross-reactions between types 6 and 16 and a one-way cross-reaction between types 2 and 22 have been demonstrated. In addition, several cross-reactions probably not due to capsular material were detected among different types by using the coagglutination test. This test should not be used alone; weak or multiple positive reactions must be confirmed by the capsular reaction test or the capillary precipitation test.

An update on Streptococcus suis identification.

Abstract: Streptococcus suis is a worldwide cause of a variety sular type 2 isolate was recovered in pure culture from of porcine infections. It has been isolated from cases lungs and kidneys of a 41⁄2-month-old aborted bovine of meningitis, bronchopneumonia, arthritis, pericarfetus and its placenta. This suggests that S. suis may ditis, endocarditis, polyserositis, septicemia, rhinitis, be pathogenic for more than 1 animal species. and abortion.20,22,24 Different alpha-hemolytic strepIn Canada, it was reported that 94% of 4-8-weektococci were ascribed to Lancefield groups R, S, RS, old clinically healthy piglets harbored S. suis in their and T in 1963.5 Other investigators working with capnasal cavities, and 79% of these isolates did not belong sulated streptococci similar to de Moor’s groups S and to the 9 capsular types.3 Recently, we demonstrated R realized that the polysaccharides involved in serothat almost 90% of these untypeable isolates belong to typing originated from the capsular material rather than only 4 of the new capsular types (types 17, 18, 19, and from the cell wall. They considered these isolates as a 21, unpublished data). Other investigators have atnew species (Streptococcus suis) within the Lancefield tributed the development of rhinitis4,7,22 to untypeable group D, with 2 capsular types: 1 and 2, respectively. S. suis isolates. At this time, it is not possible to know The de Moor’s group RS was also added as S. suis type whether any of the capsular types of S. suis belong to 1⁄2.26 In 1983, 6 new capsular types of S. suis origithe normal flora of the nasal cavity or whether they nating from diseased pigs were described. 20 In 1987 represent real pathogens. Of the new capsular types, the species was officially recognized, l4 but the authors types 9 and 22 are more frequently found in diseased demonstrated by DNA hybridization that S. suis was pigs than in healthy ones. An outbreak of S. suis type not closely related to group D streptococci. 9 infection recently occurred in swine in Canada? Despite the presence of 9 capsular types of S. suis, Although 22 of 23 capsular types of S. suis are present untypeable isolates were still frequently reported. These in North America, our studies revealed that almost isolates were recovered from diseased4,10,12,13,22,24,25 and 30% of isolates recovered from diseased pigs are still clinically healthy pigs.2,3,21 More recently, 14 new capuntypeable (unpublished data). sular types have been described.9 Some of the reference As the number of capsular types increases, serotypstrains originated from diseased pigs, whereas others ing becomes more complicated, and it could soon bewere from the nasal cavities of clinically healthy pigs. come limited to reference laboratories. Even biochemOne strain was isolated from a diseased calf (capsular ical identification, when used alone, can be misleading. type 20) and another from a human case of meningitis Thus, veterinary diagnostic laboratories face a difficult (capsular type 14). Isolates belonging to capsular type situation. There is an urgent need for a standardization 14 have recently been recovered from diseased pigs in of both the biochemical identification of S. suis and our laboratory as well as in Denmark and Belgium (Dr. the techniques for capsular typing. The purpose of this J. Henrichsen, personal communication, 1989). This paper is to summarize the knowledge of biochemical confirms that types other than capsular type 2 could characterization and serotyping of S. suis and to suggest be involved in a zoonosis.9 In addition to the bovine means to facilitate the proper identification of this incapsular type 20, several other S. suis isolates have fectious agent of growing importance. been recovered from ruminants.9,12 Capsular type 16 Streptococcus suis is a gram-positive coccus that ocwas recently isolated in our laboratory from lungs of curs singly, frequently in pairs, or occasionally in short a calf suffering from bronchopneumonia, and a capchains. The organism grows well in aerobiosis, but growth is often enhanced by microaerophilic condiFrom the Research Group in Swine Infectious Diseases, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, tions. The majority of strains are alpha-hemolytic on

Bacteria and fungi of marine mammals: a review.

Abstract: A list of the different bacterial and fungal agents isolated from marine mammals in different parts of the world is presented. Importance is given to some of the most recently identified bacterial agents, including Actinobacillus delphinicola, A. scotiae, and Brucella spp. A list, in alphabetical order, of bacteria recovered from different tissues or organs from marine mammals is presented for the integumentary, respiratory, digestive, genitourinary, and reticuloendothelial systems. Infectious bacterial agents associated with abscesses and with cases of septicemia are also listed. Information about the different fungal agents recovered from marine mammals is summarized. A section covering some of the zoonotic infectious agents recovered from marine mammals is included.

Characterization of six new capsular types (23 through 28) of Streptococcus suis.

Abstract: Six new capsular types of Streptococcus suis (types 23 to 28) are described. All reference strains were isolated from diseased pigs and were morphologically and biochemically similar to previously described capsular types 1 to 22. Clear and specific reactions were obtained for each of the new capsular types with three different typing techniques; no cross-reactions were detected among them or with other S. suis capsular types. Their capsular material presented similar ultrastructural characteristics, as shown by electron microscopy, and fimbriae similar to those described for other capsular types of S. suis were observed. When untypeable field isolates were tested with antisera raised against the six new capsular types, capsular type 23 appeared to be the most prevalent, representing more than 50% of all these isolates. Most isolates were recovered from cases of pneumonia, septicemia, and meningitis. Presumptive biochemical identification described for S. suis capsular types 1 to 22 may also be used for capsular types 23 to 28. Images

Developmental effects of endocrine-disrupting chemicals in wildlife and humans.

Abstract: Large numbers and large quantities of endocrine-disrupting chemicals have been released into the environment since World War II. Many of these chemicals can disturb development of the endocrine system and of the organs that respond to endocrine signals in organisms indirectly exposed during prenatal and/or early postnatal life; effects of exposure during development are permanent and irreversible. The risk to the developing organism can also stem from direct exposure of the offspring after birth or hatching. In addition, transgenerational exposure can result from the exposure of the mother to a chemical at any time throughout her life before producing offspring due to persistence of endocrine-disrupting chemicals in body fat, which is mobilized during egg laying or pregnancy and lactation. Mechanisms underlying the disruption of the development of vital systems, such as the endocrine, reproductive, and immune systems, are discussed with reference to wildlife, laboratory animals, and humans.

Leptospirosis: a zoonotic disease of global importance

Abstract: In the past decade, leptospirosis has emerged as a globally important infectious disease. It occurs in urban environments of industrialised and developing countries, as well as in rural regions worldwide. Mortality remains significant, related both to delays in diagnosis due to lack of infrastructure and adequate clinical suspicion, and to other poorly understood reasons that may include inherent pathogenicity of some leptospiral strains or genetically determined host immunopathological responses. Pulmonary haemorrhage is recognised increasingly as a major, often lethal, manifestation of leptospirosis, the pathogenesis of which remains unclear. The completion of the genome sequence of Leptospira interrogans serovar lai, and other continuing leptospiral genome sequencing projects, promise to guide future work on the disease. Mainstays of treatment are still tetracyclines and beta-lactam/cephalosporins. No vaccine is available. Prevention is largely dependent on sanitation measures that may be difficult to implement, especially in developing countries.

Impact of 16S rRNA Gene Sequence Analysis for Identification of Bacteria on Clinical Microbiology and Infectious Diseases

Abstract: The traditional identification of bacteria on the basis of phenotypic characteristics is generally not as accurate as identification based on genotypic methods. Comparison of the bacterial 16S rRNA gene sequence has emerged as a preferred genetic technique. 16S rRNA gene sequence analysis can better identify poorly described, rarely isolated, or phenotypically aberrant strains, can be routinely used for identification of mycobacteria, and can lead to the recognition of novel pathogens and noncultured bacteria. Problems remain in that the sequences in some databases are not accurate, there is no consensus quantitative definition of genus or species based on 16S rRNA gene sequence data, the proliferation of species names based on minimal genetic and phenotypic differences raises communication difficulties, and microheterogeneity in 16S rRNA gene sequence within a species is common. Despite its accuracy, 16S rRNA gene sequence analysis lacks widespread use beyond the large and reference laboratories because of technical and cost considerations. Thus, a future challenge is to translate information from 16S rRNA gene sequencing into convenient biochemical testing schemes, making the accuracy of the genotypic identification available to the smaller and routine clinical microbiology laboratories.

Surface Proteins of Gram-Positive Bacteria and Mechanisms of Their Targeting to the Cell Wall Envelope

Abstract: The cell wall envelope of gram-positive bacteria is a macromolecular, exoskeletal organelle that is assembled and turned over at designated sites. The cell wall also functions as a surface organelle that allows gram-positive pathogens to interact with their environment, in particular the tissues of the infected host. All of these functions require that surface proteins and enzymes be properly targeted to the cell wall envelope. Two basic mechanisms, cell wall sorting and targeting, have been identified. Cell well sorting is the covalent attachment of surface proteins to the peptidoglycan via a C-terminal sorting signal that contains a consensus LPXTG sequence. More than 100 proteins that possess cell wall-sorting signals, including the M proteins of Streptococcus pyogenes, protein A of Staphylococcus aureus, and several internalins of Listeria monocytogenes, have been identified. Cell wall targeting involves the noncovalent attachment of proteins to the cell surface via specialized binding domains. Several of these wall-binding domains appear to interact with secondary wall polymers that are associated with the peptidoglycan, for example teichoic acids and polysaccharides. Proteins that are targeted to the cell surface include muralytic enzymes such as autolysins, lysostaphin, and phage lytic enzymes. Other examples for targeted proteins are the surface S-layer proteins of bacilli and clostridia, as well as virulence factors required for the pathogenesis of L. monocytogenes (internalin B) and Streptococcus pneumoniae (PspA) infections. In this review we describe the mechanisms for both sorting and targeting of proteins to the envelope of gram-positive bacteria and review the functions of known surface proteins.