Human salivary aggregation in Streptococcus intermedius type g strains: relationship with IgA

Low microbial abundance and community diversity in the egg capsule of the oviparous cloudy catshark (Scyliorhinus torazame) during oviposition

Vertebrate embryos are protected from bacterial infection by various maternally derived factors, yet little is known about the defence mechanisms in elasmobranchs. This study aimed to characterize the intracapsular environment of freshly laid eggs of the oviparous catshark (Scyliorhinus torazame) by investigating the microbial abundance and microbiota to understand its potential contribution to embryonic defence. The egg capsule of oviparous elasmobranchs is tightly sealed until pre-hatching, after which seawater flows into the capsule, exposing the embryos to the surrounding seawater. We found that early embryos were highly vulnerable to environmental pathogens, suggesting that the embryos are somehow protected from infection before pre-hatching. Indeed, the intracapsular environment of freshly laid eggs exhibited significantly low bacterial density, maintained until pre-hatching. Furthermore, the microbiome inside eggs just after oviposition differed markedly from those of rearing seawater and adult oviducal gland epithelia; these eggs were predominantly populated by an unidentified genus of Sphingomonadaceae. Overall, this study provides compelling evidence that early embryos of oviparous cloudy catshark are incubated in a clean intracapsular environment that potentially plays a significant role in embryonic development in oviparous elasmobranchs.

Assessment of Age-Related Changes of Salivary Immunoglobulin A Levels among Healthy Individuals

Background:

Secretory immunoglobulin A (IgA) is the first line of defense against pathogens that invade mucosal surfaces. It has been reported that the immune system exhibits profound age-related changes. The aim of this study was to investigate the age-dependent changes of salivary IgA among healthy individuals.

Materials and Methods:

Saliva samples were collected from 120 healthy individuals (aged 11–70 years). The salivary IgA concentrations were measured by the use of a single radial immunodiffusion technique and analyzed using the Mann–Whitney U, Kruskal–Wallis, and Chi-square tests.

Results:

The mean salivary IgA levels were 81.11 ± 4.50 mg/dl at age 11–20 years, 92.71 ± 13.76 mg/dl at age 21–30 years, 96.50 ± 4.04 mg/dl at age 31–40 years, 104.96 ± 10.15 mg/dl at age 41–50 years, 113.22 ± 7.85 mg/dl at age 51–60 years, and 91.38 ± 4.77 mg/dl at age 61–70 years. There was a significant difference among the mean salivary IgA levels of different age groups (P < 0.001).

Conclusion:

These results showed that the salivary IgA levels exhibit age-related changes. Oral immunization may be considered to improve oral immunity when the salivary concentrations of IgA begin to decrease during lifetime.

Non-surface Attached Bacterial Aggregates: A Ubiquitous Third Lifestyle

Bacteria are now generally believed to adopt two main lifestyles: planktonic individuals, or surface-attached biofilms. However, in recent years medical microbiologists started to stress that suspended bacterial aggregates are a major form of bacterial communities in chronic infection sites. Despite sharing many similarities with surface-attached biofilms and are thus generally defined as biofilm-like aggregates, these non-attached clumps of cells in vivo show much smaller sizes and different formation mechanisms. Furthermore, ex vivo clinical isolates were frequently reported to be less attached to abiotic surfaces when compared to standard type strains. While this third lifestyle is starting to draw heavy attention in clinical studies, it has a long history in natural and environmental sciences. For example, marine gel particles formed by bacteria attachment to phytoplankton exopolymers have been well documented in oceans; large river and lake snows loaded with bacterial aggregates are frequently found in freshwater systems; multispecies bacterial "flocs" have long been used in wastewater treatment. This review focuses on non-attached aggregates found in a variety of natural and clinical settings, as well as some recent technical developments facilitating aggregate research. The aim is to summarise the characteristics of different types of bacterial aggregates, bridging the knowledge gap, provoking new perspectives for researchers from different fields, and highlighting the importance of more research input in this third lifestyle of bacteria closely relevant to our daily life.