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

Rapid slide agglutination (RSA), quantitative plate agglutination, slow tube agglutination (STA), and ring precipitation (RP) tests were performed on 200 isolates of Haemophilus pleuropneumoniae by using the type sera produced in rabbits against five known serotype strains and one strain 202. RSA and RP tests both yielded the same results as those by STA. None of the agglutination procedures could be used for serotyping isolates that autoagglutinated in saline. The RP test was successfully used for serotyping such strains. The specificity of the RSA and RP tests was confirmed by cross-absorption studies. All of the isolates except two had strong serotype-specific activities. The most common serotype isolated in Quebec was serotype 1, followed by serotypes 5 and 2. None of the isolates belonged to serotypes 3 and 4. Only two isolates were found to be untypable; they could possibly belong to serotype(s) not yet defined. The RSA and RP tests may be at least as reliable as the STA test, but easier to perform, less expensive, and much more rapid than any of the other methods reported. Of all the procedures studied by us, the RP test proved to be the method of choice for serotyping H. pleuropneumoniae; hence, it should replace the STA test for serotyping H. pleuropneumoniae.

Evaluation of slide agglutination and ring precipitation tests for capsular serotyping of Haemophilus pleuropneumoniae

A coagglutination test for the identification and serotyping of Haemophilus pleuropneumoniae is described. A total of 360 H. pleuropneumoniae strains were isolated from pulmonary tissues of feeder pigs which died of acute pleuropneumonia. All of the isolates were serotyped by coagglutination, and the results were confirmed by the ring precipitation test. The most common serotype isolated in Quebec was serotype 1, followed by serotypes 5, 2, and 7. None of the isolates belonged to serotypes 3, 4, or 6. Mixed infections due to H. pleuropneumoniae of more than one serotype in the same animal were encountered. Serotype 1 was the only common isolate among the mixed-serotype infections. The coagglutination test was more sensitive than was the ring precipitation test. Serotyping by the coagglutination test is inexpensive, rapid, reliable, and easy to perform.

Identification and serotyping of Haemophilus pleuropneumoniae by coagglutination test.

A case of human endocarditis due to Streptococcus suis in North America.

Polyvalent coagglutination reagents (PRs) have been evaluated for the serotyping of Streptococcus suis. Monovalent antisera produced against 28 S. suis reference strains have been grouped to obtain five different pools. A total of 249 field isolates previously identified and belonging to different serotypes were tested with PRs prepared by two different procedures: (i) monovalent coagglutination reagents were individually prepared and mixed in equal proportions, and (ii) antisera were mixed in equal proportions before the addition of the Staphylococcus aureus suspension. Only antisera tested by a tube agglutination test with 2-mercaptoethanol and presenting titers of 1:32 or higher were used. Results obtained with PRs prepared by both procedures were similar, and there was a very good correlation between the capsular type of the isolate and the reaction obtained with PRs. Thus, from a practical viewpoint, it is suggested that PRs be prepared by the first procedure. To isolates, were tested in parallel with both the PRs and the monovalent coagglutination reagents over a 1-year period. Ninety-nine percent of the typeable and all of the untypeable isolates were correctly identified. Serotyping with PRs is suggested to be a very useful and reliable screening procedure, particularly when a large number of S. suis isolates have to be serotyped. In addition, the choice of antisera to be included in a given pool is facultative and should be oriented to the needs of a region or a country.

Use of polyvalent coagglutination reagents for serotyping of Streptococcus suis.

A convenience sample of 234 colostral specimens, collected directly from the nursing bottle immediately prior to the first feeding, was studied. Samples originated from 6 farms and were collected over 24 months. Routine bacteriologic techniques were used to quantify the bacterial load of the colostrum, as well as to identify the bacteria. Overall, at least 1 microorganism was cultured from 221 colostral samples (94.4%). By using the upper tolerance level of 100 000 bacteria/mL, 84 samples (35.9%) were considered contaminated. Staphylococcus spp. (57.7%), gram-negative rods (47.9%), coliforms (44.0%), and Streptococcus uberis (20.5%) were among the most frequently isolated bacteria. The relative risk (RR) of contamination with more than 100 000 bacteria/mL was significantly greater in warm months [RR = 2.55, 95% confidence interval (CI): 1.63 to 4.02] than in cool months and in colostrum offered to male calves (RR = 1.55, 95% CI: 1.09 to 2.20). Bacterial load was also associated with the farm of origin (P < 0.0001). When assessing colostrum management, one should consider bacterial contamination. Multiple factors are likely associated with the degree of contamination, and farm-specific factors may be important. Further studies are necessary to evaluate the impact of bacterial contamination of colostrum on neonatal health.

Robert Higgins

Papers

Evaluation of slide agglutination and ring precipitation tests for capsular serotyping of Haemophilus pleuropneumoniae

Identification and serotyping of Haemophilus pleuropneumoniae by coagglutination test.

A case of human endocarditis due to Streptococcus suis in North America.

Use of polyvalent coagglutination reagents for serotyping of Streptococcus suis.

Bacterial contamination of colostrum fed to newborn calves in Québec dairy herds.