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.

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

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.

https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(03)00830-2.pdf

Leptospirosis: a zoonotic disease of global importance

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.

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

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.

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

Developmental effects of endocrine-disrupting chemicals in wildlife and humans

In the latter part of 1991 an unusual neurological disease was recognised on several farms in England. This report describes the case histories and clinical, biochemical and pathological findings in six calves and two lambs aged from two to 44 weeks obtained from five of these farms. Laminar cerebrocortical necrosis and severe bilateral necrosis of the thalamus and/or striatum progressing to cavitation were recognised in their brains. These changes are similar to those of experimental sulphate toxicity. Morbidity rates of 16 to 48 per cent and mortality rates of 0 to 8 per cent were recorded. The affected animals did not respond to vitamin B1 treatment; the erythrocyte transketolase levels of in-contact cattle and of one untreated affected calf and one untreated lamb were within the normal range. All five farms had recently introduced a proprietary concentrate ration containing ammonium bicarbonate. After this ration was withdrawn no new cases of nervous clinical disease were observed. It is suggested that, in at least some cases, the morphology and topography of lesions may distinguish sulphate induced polioencephalomalacia from that of sporadic thiamine-dependent cerebrocortical necrosis.

Polioencephalomalacia associated with the ingestion of ammonium sulphate by sheep and cattle

Production and characterization of two Streptococcus suis capsular type 2 mutants.

Birds of prey are often affected with external ocular injuries that are routinely treated with antimicrobial agents used for small animals. The resident ocular bacterial and fungal flora is still unknown in birds of prey and this knowledge would be very useful in assessing the accuracy of treatments. In a study involving 65 raptors with healthy eyes, swabs were taken from both eyes to identify the resident bacterial and fungal flora. Fifty-five birds had a positive culture in one or both eyes. Both gram-positive and gram-negative organisms were isolated, with a predominance of Staphylococcus spp., which were found in 52.3% of cultures. Only two fungal species, Aspergillus spp. and Cladosporium spp. were found. The overall results of this study are similar to previous studies carried out in humans and other animals.

Bacterial and fungal flora in healthy eyes of birds of prey.

Serological properties of antigens extracted from strains of Haemophilus pleuropneumoniae belonging to seven different serotypes were investigated. Antisera were prepared in rabbits against Formalin-treated whole cell suspensions as well as autoclaved cell suspensions. Saline and heat extracts and their alcohol precipitate antigens of H. pleuropneumoniae were used in the indirect hemagglutination test. All the antigens used were easily adsorbed directly onto sheep erythrocytes. Saline extract antigen showed maximum type specificity. Heating of the whole cell suspension revealed the cross-reactive minor antigenic determinants. Thus, the heat extract preparations had both type-specific and species-specific antigens. It is suggested that the indirect hemagglutination test may be useful for both serotyping and serodiagnosis of H. pleuropneumoniae infections in pigs.

Determination of antigenic specificity and relationship among Haemophilus pleuropneumoniae serotypes by an indirect hemagglutination test.

The study was undertaken to determine the prevalence, in the nasal cavities, of Streptococcus suis in four to eight week old clinically healthy piglets. Streptococci biochemically compatible with S. suis were isolated from 94% of piglets and 98% of farms. Of the 782 isolates submitted to serotyping, only 164 (21%) were included in the nine official serotypes. These 164 typable isolates originated from 121 (31%) of the 388 piglets and from 36 (73%) of the 49 farms included in the study. The most frequent serotypes found in piglets were, in decreasing order, 3, 4, 8 and 2. Serotype 1 was not detected in this survey. As many as 32% of piglets were found positive for two different serotypes and three different serotypes were found in 1%.

Robert Higgins

Papers

Polioencephalomalacia associated with the ingestion of ammonium sulphate by sheep and cattle

Production and characterization of two Streptococcus suis capsular type 2 mutants.

Bacterial and fungal flora in healthy eyes of birds of prey.

Determination of antigenic specificity and relationship among Haemophilus pleuropneumoniae serotypes by an indirect hemagglutination test.

Prevalence of Streptococcus suis in four to eight week old clinically healthy piglets.