The species diversity and ultimate survival of amphibians, one of the major groupings of vertebrate animals, face tremendous challenges today for reasons that are still not entirely understood. Since the 1980s, the pace of amphibian extinction has been alarming, and almost 200 identified species have become extinct. About one-third of all amphibian species have seen dramatic declines in populations, and are now considered to be endangered or threatened with extinction. See also: Biodiversity; Endangered species; Extinction (biology); Extinction of species

It is estimated that 1 gram of soil can be inhabited by up to 10⁹ microorganisms and approximately 60,000 bacterial species. Moreover, soil harbors a vast reservoir of antimicrobial agents, and soil-dwelling bacteria have played a key role in the introduction of antibiotics to treat infectious diseases. Because these resilient bacteria not only produce antibiotics but also are exposed to other antibiotics produced by surrounding strains in the soil, they have developed diverse mechanisms to survive the toxic antimicrobial compounds created around them. Importantly, these mechanisms of robust resistance to numerous classes of antibiotics often resemble the mechanisms of resistance identified in clinical pathogens, including those that infect humans. Thus, scientists are attempting to find possible correlations between antibiotic resistance in soil bacteria and in infectious agents in humans. If correlations can be found, investigators might be able to predict future signs of clinical resistance to certain antibiotics, providing clinicians with methods to circumvent any potential resistance that may emerge. See also: Antibiotic; Antimicrobial agents; Antimicrobial resistance; Bacteria; Clinical microbiology; Drug resistance; Infectious disease; Medical bacteriology; Microbiology; Pathogen; Soil; Soil microbiology

Soil harbors a vast reservoir of antimicrobial agents. In fact, approximately 80% of all clinically implemented antibiotics are derived from soil-dwelling bacteria. However, many bacteria have evolved methods to evade the effects of various antibiotics and thus have acquired resistance to these chemical substances. Today, the increasing resistance of many common disease-causing bacteria to antibiotics is a global health crisis. Therefore, scientists are seeking to develop new antibiotics that can overcome the resistance capabilities of numerous pathogenic bacteria. Arylomycins are considered to be among the most promising of these new compounds. See also: Antibiotic; Antibiotic resistance; Antibiotic resistance in soil bacteria; Antimicrobial agents; Bacteria; Infectious disease; Medical bacteriology; Microbiology; Pathogen; Public health; Soil; Soil microbiology

A compound found in cranberries, called cranberry proanthocyanidin (cPAC), when used in combination with antibiotics, such as tetracycline, prevents resistance to antibiotics in Escherichia coli and Pseudomonas aeruginosa, according to researchers reporting in the journal Advanced Science (May 2019). In addition, the combined use of antibiotics with cPAC inhibits biofilm formation, another a route toward antibiotic resistance. This type of synergy—whereby one substance that does not normally produce a desired effect makes a second substance significantly more effective—is called potentiation. See also: Antibiotic; Antibiotic resistance; Biofilm; Cranberry

There has been substantial progress in the fight against certain drug-resistant organisms that cause serious, often fatal, diseases. However, two drug-resistant microbes—specifically, Candida auris (a fungal yeast) and Acinetobacter (a genus of bacteria)—are responsible for a growing number of drug-resistant infections worldwide. These organisms pose such a potential danger to the health of affected individuals that the Centers for Disease Control and Prevention (CDC) in the United States has added the microbes to its list of pathogenic organisms considered to be urgent public-health threats. [The other pathogens on the CDC's list are Clostridioides difficile (a bacterium formerly known as Clostridium difficile), Neisseria gonorrhoeae (the causative agent of gonorrhea), and various organisms belonging to the Enterobacteriaceae bacterial family.] See also: Bacteria; Candida; Clostridium; Drug resistance; Fungi; Infectious disease; Medical bacteriology; Medical mycology; Microbiology; Pathogen; Public health; Yeast

Tuberculosis (TB) is a chronic infectious disease of humans (as well as animals) primarily involving the lungs. It is caused by the tubercle bacillus Mycobacterium tuberculosis and is transmitted by pathogenic airborne droplets. Approximately 5–10% of individuals infected with the TB bacterium progress to develop the active disease, and these individuals must be treated with a combination of antibiotics, taken for several months, for effective elimination of the disease. However, treatment failure or relapse is on the rise as a result of drug-resistant strains of the M. tuberculosis organism. See also: Antibiotic; Antibiotic resistance; Antimicrobial resistance; Bacteria; Bacteriology; Clinical microbiology; Drug resistance; Lung; Medical bacteriology; Microbiology; Mycobacterial diseases; Pathogen; Tuberculosis

The emergent discipline of evolutionary epidemiology recognizes that pathogens (disease-causing organisms) are biological entities that can evolve quickly to take advantage of ecological or environmental changes that promote their transmission. Virulence, a measure of a microorganism's ability to infect and sicken a host, also evolves, which allows previously mild diseases to become life-threatening ones, or vice versa. Pathogens and virulence evolve because the life cycle of pathogens is typically very short compared to that of their hosts. The majority of bacteria and viruses replicate numerous times daily, enabling natural selection to favor variants that thrive against the relatively stable, more slowly adapting host. In addition, virulence varies not only from pathogen to pathogen, but also from strain to strain. For example, Escherichia coli can cause fatal foodborne illnesses, yet harmless strains of this bacterium inhabit the intestinal tract of humans. Thus, evolutionary epidemiologists seek to explain the factors contributing to the evolution of pathogens and virulence. See also: Bacteria; Disease; Epidemiology; Escherichia; Escherichia coli outbreaks; Food safety and foodborne illness; Infectious disease; Organic evolution; Pathogen; Virulence; Virus

In a breakthrough in the global fight against malaria, the World Health Organization (WHO) is recommending widespread administration of the first-ever malaria vaccine. This first-generation vaccine is intended for children considered to be at high risk in specific regions where the disease is rampant, such as sub-Saharan Africa, Southeast Asia, and the Eastern Mediterranean. The WHO's announcement on October 6, 2021, is expected to significantly curtail the disease's impact, which is felt most acutely in sub-Saharan Africa, where malaria kills more than 260,000 children under the age of five annually. More than 200 million malaria infections occur globally every year (Fig. 1). See also: Infectious disease; Malaria; Vaccination

The influenza virus may be easier to transmit than previously thought, according to a report in the Proceedings of the National Academy of Sciences (January 2018). It turns out that sneezing and coughing are not required to pass on the influenza virus; simply breathing is sufficient. The important takeaway from this study is that avoiding people who are coughing and sneezing and washing your hands, although helpful, will not completely protect you from getting the flu. See also: Infectious disease; Influenza; Virus

The historical use of medicinal mushrooms in the traditional therapies of East Asia has been documented for millennia, and biomedical science is now seeking to validate this ancient mycological knowledge through more rigorous evaluation and testing of the nutritional and medicinal properties of these mushrooms. Because many of the current investigations have confirmed at least some health benefits from the consumption of mushrooms, there has been a concomitant increase in the professional and private cultivation of a number of fungal species. See also: Ethnomycology; Fungal biotechnology; Fungi; Mushroom; Mushroom pharmacy; Mycology