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

The salmonella status of nine different broiler-chicken flocks was studied from the day before the chickens were placed in the house until their sixth week of age. The presence of salmonella serotypes in dust, litter, feces, water, and feed was investigated. Dust from different sites was sampled and appeared to be contaminated with salmonellae even after six of the nine houses were disinfected. Defects in the cleaning and disinfection of air inlets and fans seemed to be an important factor for the recontamination of the house. Chickens were often contaminated at the hatchery, and in two houses the percentage of contamination had increased to as much as 82 7% and 88 8% at six weeks of age. Swabbing of intact and fresh feces appeared to be a more reliable technique than culturing the litter for evaluating the shedder state of the flock, and it appeared also to be more rapid and simple than the collection of cloacal swabs.

Studies on the dissemination of Salmonella in nine broiler-chicken flocks.

Characterization of Campylobacter Isolates Recovered from Clinically Healthy Pigs and from Sporadic Cases of Campylobacteriosis in Humans

There are a whole series of emerging and re-emerging zoonotic diseases present in the Northern Hemisphere and the author describes four of them, namely, bartonellosis, leptospirosis, Lyme borreliosis and plague. Reasons for the emergence or re-emergence of such diseases are not clear, but factors such as human demographics, economic development and land use, international travel and commerce, and microbial adaptation, are thought to be involved. Control of emerging and re-emerging diseases has become a major challenge for the international community and it is important to disseminate information about diagnosis and control capabilities, particularly to people working in public health.

https://web.oie.int/boutique/extrait/569582higgins.pdf

Emerging or re-emerging bacterial zoonotic diseases: Bartonellosis, leptospirosis, Lyme borreliosis, plague

The fat cow syndrome developed over a two year period in a 100 cow dairy herd following overfeeding in late lactation and the dry period. It was characterised clinically by a high incidence of parturient paresis and chronic unresponsive ketosis in early lactation. The reproductive performance of the herd was poor throughout this period, with extended calving indices confirming a suggested link between fatty liver and infertility.

Fat cow syndrome in a British dairy herd

To evaluate the relative importance of the various enteropathogens causing neonatal diarrhea in Quebec farrowing operations, observations were made on 749 diarrheic pigs from 325 outbreaks of diarrhea. They were one to 15 days of age, and were obtained alive for necropsy generally within 48 hours of the onset of diarrhea. Some pigs were from severe, explosive outbreaks of diarrhea with high morbidity and mortality rates, while others were from herds with chronic neonatal diarrhea with lower morbidity and mortality rates. A combination of bacteriological, virological and histological methods were used to study the pigs.

Viruses were incriminated in 60%, bacteria in 23% and coccidia in 15.3% of the 325 diarrhea outbreaks. Transmissible gastroenteritis virus was by far the most common enteropathogen with a prevalence of 52%; rotavirus was implicated in 9.2% of the outbreaks while adenovirus was incriminated in 0.30% of the outbreaks. Enterotoxigenic Escherichia coli were involved in 22.4% of the cases while Clostridium perfringens type C was an occasional finding. Coccidia involved in our herds were identified as Isospora suis. The disease was attributed to infection with a single etiologic agent in 590 diarrheic pigs (78%) while combinations of agents were present in only 90 (12%).

The age-specific occurrence of the various enteropathogens was evaluated. Transmissible gastroenteritis virus was the most common enteropathogen in all age groups. Colibacillosis was common in pigs which became diarrheic under five days of age; in this age group, the enterotoxigenic E. coli were frequently found alone, but were usually combined with other agents in older pigs. The prevalence of coccidia was high in pigs which became diarrheic between five and 15 days of age. Rotavirus infection was common in diarrheic pigs older than ten days of age. Although individual baby pigs were commonly infected with a single enteropathogen, it was very common to see more than one agent involved in an outbreak of diarrhea, particularly when pigs of different ages were affected.

Observations on the occurrence of the enteropathogens according to the seasons were also made. Occurrence of transmissible gastroenteritis was throughout the year with the highest prevalence during the fall, winter and spring months. Colibacillosis and coccidiosis were more common in the summer, fall and early winter months with the lowest prevalence in the spring months.

Robert Higgins

Papers

Studies on the dissemination of Salmonella in nine broiler-chicken flocks.

Characterization of Campylobacter Isolates Recovered from Clinically Healthy Pigs and from Sporadic Cases of Campylobacteriosis in Humans

Emerging or re-emerging bacterial zoonotic diseases: Bartonellosis, leptospirosis, Lyme borreliosis, plague

Fat cow syndrome in a British dairy herd

Neonatal diarrhea of pigs in Quebec: infectious causes of significant outbreaks.