Microbial Transmission

Fernando Baquero, Emilio Bouza, Jose A. Gutierrez-Fuentes, Teresa M. Coque, J. A. Gutiérrez-Fuentes

• Publisher: ASM Press
• Year: 2019
• Print ISBN: 9781555819736
• eBook ISBN: 9781683672913
• Edition: 1
• Topic: Medicine
• Subtopic: Medical Microbiology & Parasitology

Microbial transmission, the processes by which microbes transit to new environments, is a significant and broad-reaching concept with applications throughout the biological sciences. This collection of reviews, edited by an international team of experts studying and working across a range of disciplines, explores transmission not just as an idea in disease but as a fundamental biological process that acts in all domains of nature and exerts its force on disparate size scales, from the micro to the macro, and across units of time as divergent as a single bacterial replication cycle and the entire course of evolution.

In five sections, this overview

• Defines the concept of transmission and covers basic processes of transmission, including causality, control strategies, fitness costs, virulence, and selection
• Presents numerous combinations of transmission scenarios across the bacterial, animal, and human interface
• Examines transmission as the defining characteristic of infectious disease
• Presents methods for experimentally verifying and quantifying transmission episodes
• Concludes with important theoretical and modeling approaches

Anyone studying or working in microbial colonization, evolution, pathogenicity, antimicrobial resistance, or public health will benefit from a deeper understanding of Microbial Transmission.

2 Causality in Biological Transmission: Forces and Energies

FERNANDO BAQUERO1

The immediate mental representation of the concept of transmission for the public health epidemiologist, clinical microbiologist, or infectious diseases specialist concerns its application to the transmission of pathogenic microorganisms or the transmission of infections. Note that the widely used term “transmissible diseases” is certainly most inappropriate. Disease is the result of particular cross talk between microbe and host and is never transmissible as such. The infective process is what the microbe produces inside a particular host, which is well illustrated in the Latin origin of the word “infection,” derived from inficere (in + facere): “to put in, to dip into, to do an action inside.” Microbes are transmissible, not the infection. In general biology, the most frequent use of “transmission” applies to the transmission of hereditary characters (to the progeny), as in population genetics (1). To our knowledge, a broad conceptual understanding of transmission has not yet been attempted, although Hugh Dingle has approached the need of expanding the transmission-related concept of migration to different hierarchical levels (2). In this review, I intend to present the concept of transmission in a broad perspective, as a basic biological and evolutionary process, focusing particularly on the causes (forces and energies) governing transmission, a hitherto neglected field in biological and epidemiological research. For this purpose, it is appropriate to review what we collectively have in mind when considering the concept of transmission.

THE COGNITIVE REPRESENTATION OF THE CONCEPT OF TRANSMISSION

Thinking about a concept implies a cognitive representation, producing mental particulars with semantic properties (3), allowing the intelligibility of complex, polysemic processes (4). Paraphrasing Wittgenstein, the limits of our knowledge correspond to the limits of our words, our synthetic cognitive representations. In the case of the concept of transmission, we inevitably construct our cognitive representation with a quite diverse array of “transsumptions” involving knowledge and experiences of different origins that are for natural scientists transposed to the domain of biology (5).

The word “transmission” evokes the movement of a particle or a wave from one part of space to another. Particulate transmission occurs in nuclear fission; transmission (transport) of molecules in the cytoplasm or across cell membranes; transmission of pheromones; neurotransmission in synapsis; transmission of phages and plasmids across bacteria; and transmission of genes and gene sequences between genomes, including fertilization of ovules. Transmission is typically host-to-host transmission of microbes by insects or by microdrops in the air, transmission of multiresistant bacteria in hospitals, mother-child transmission of microbiota, or transmission of bacterial communities from farms to environmental water bodies. Also, there is transmission of gametes by pollinator insects, transmission of seeds by fruits, and transmission of fungal spores. In addition, there are bird migrations and globalized human journeys. Nonparticulate transmission occurs in the oscillatory waves produced by vibration after a stone impacts water, or propagation of a sound, electric light, or radio waves; transmission in the wheels of machines or mechanisms; and fire-to-the-teapot heat transmission. Also, there is cultural transmission of knowledge, cultural values, or even stupid behavior in society. In short, transmission is movement; and life is replication and change, movement.

COMPONENTS OF THE TRANSMISSION PROCESS

Transmission has a site of origin and a termination, a site of end. Reducing our view to biological particulate transmitted entities (ranging from biomolecules to biological ecosystems), and in order to facilitate a general view on transmission, we consider these sites as “patches,” in the meaning used in metapopulation biology. A patch is here defined as a part of space that is occupied by the transmitted entity and separated by an unfit space from other patches that might be able to receive this object (6). Note that this concept of transmission between patches diverges from mere “dispersal”—dispersal is not transmission if a receiving patch does not interact with the transmitted object. Therefore, transmission implies a patch of departure, a nonpatched space to cross, and a patch of reception (7, 8).

This view is obviously inspired from information theory (9, 10), with the classic tripartite composition: a sender or transmitter, located in a particular patch of space, which is the source of the transmitted object; the message; and a receiver patch that interacts with the message. I would like to insist on the point that transmission ...

Table of contents

• Cover
• Microbial Transmission
• I. INTRODUCTION
• II. BASIC PROCESS OF TRANSMISSION
• III. SCENARIO OF TRANSMISSION
• IV. PATIENT-TO-PATIENT TRANSMISSION
• V. EXPERIMENTAL AND THEORETICAL MODES OF TRANSMISSION