Pathogenic Bacteria

What Are Pathobionts?

Pathogenic bacteria especially when they become dominant = pathobionts (10)

How Many Human Pathogens Exist and How Many Deaths Do They Cause?

To date, approximately 1400 species of human pathogens have been identified, including viruses, bacteria, fungi, protozoa, and helminths. As the Earth Microbiome Project advances, this number is expected to raise dramatically (4). These­ pathogens­ cause­ 16 million deaths each year, and this situation is predicted to worsen in the future (5). Pathogenic bacteria are overrepresented in the microbial databases (11)

Which Pathogens Cause Emerging Infectious Diseases in Humans?

Pathogens comprised of viruses, bacteria, gut microbiome, and Parasites / Parasitism are a leading cause of ever-emerging diseases in humans (12)

Which Bacteria Are Classified as WHO Priority 1 Pathogens?

Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa are part of the World Health Organization's Priority 1 group of pathogens. These bacteria are acknowledged as significant contributors to mortality associated with antimicrobial resistance (AMR) (13)

How Do Pathogenic Bacteria Use Metabolism to Survive, Cause Disease, and Evade Host Immunity?

Bacterial metabolism is crucial for both the virulence and the survival of pathogens within a host. Furthermore, these pathogens have developed advanced metabolic strategies to manipulate host immune responses, thereby promoting infection (6)

How Do Bacterial Pathogens Acquire Nutrients From Their Hosts?

The success of bacterial pathogens relies on sophisticated strategies for scavenging nutrients from their hosts (“nutritional virulence factors’’). Other pathogens compete effectively with the host for nutrients that are available as a result of normal host physiology (14)

How Do Intracellular Bacterial Pathogens Acquire Nutrients, Manipulate Host Metabolism, and Survive Stress?

Intracellular bacterial pathogens have developed ways to survive and multiply inside the host. They adjust their metabolism to cope with immune responses, environmental changes, and drugs.

• Nutrient Acquisition: Pathogens find ways to gather necessary nutrients from the host.


• Host Metabolism Modulation: They change the host's metabolic processes to their advantage.


• Stress-Induced Changes: Pathogens adapt their metabolism in response to stress, aiding in their survival and virulence (8).
  Intracellular pathogens are largely or completely dependent on host nutrients (9)

Pathogens Genetically Adapt to Life Within a Host

Pathogens undergo significant genetic adaptations when associated with the host (15)

How Do Pathogenicity Islands and Phages Drive the Evolution of Hypervirulent Strains Like MRSA?

The presence of strain-specific variations complicates the development of effective therapies. Dominant lineages of pathogens often possess unique virulence profiles, influenced by mobile genetic elements such as pathogenicity islands and phages. These elements facilitate horizontal gene transfer, leading to the evolution of hypervirulent clones, such as methicillin-resistant Staphylococcus aureus (MRSA) (7)

How Do Pathogen-Derived Metabolites Increase Bacterial Virulence?

Metabolites from pathogenic bacteria can signal between bacteria and hosts. This communication can enhance virulence. It helps in biofilm formation and activating virulence traits (16, 17, 18).

When Does the Gut Microbiome Become Pathogenic?

Although the gut microbiome is generally symbiotic or commensal, some microbiome members become pathogenic under certain circumstances (10)

Which Gut Bacteria Can Trigger Pathogenic Reactions?

Bacteria such as Escherichia coli, Fusobacterium nucleatum, and Helicobacter pylori can cause pathogenic reactions in the host (19)

What Diseases Are Caused by Enteric Pathogens?

Enteric pathogens, including a diverse plethora of enteric viruses, cause acute and chronic diseases (20)

How Do Pathogenic Bacteria Evade Cell-Autonomous Immunity?

Pathogenic bacteria have evolved diverse mechanisms to counteract cell-autonomous immunity, which otherwise guards both immune and non-immune cells from the onset of an infection (21, 22)

What Are Pathogen-Associated Molecular Patterns?

Pathogen-associated molecular patterns (PAMPs), which are motifs such as bacterial LPS and viral nucleic acid features (23)

How Does Metabolic Flexibility Help Pathogenic Bacteria Survive in the Host?

Most pathogenic bacteria exhibit remarkable metabolic flexibility, allowing them to adapt to various niches within their hosts and exploit available nutrients effectively (24). Pathogenic bacteria release metabolites to outcompete others (25, 26)

How Do Intracellular Pathogens Exploit Host Cellular Machinery?

For example, some intracellular pathogens hijack autophagic or proteolytic cellular machinery to release amino acids that can be exploited as carbon and energy sources (27, 28)

Which Low-Abundance Gut Bacteria Can Become Pathogenic?

There are also pathogenic species (Bad Guys (certain harmful bacteria)) such as Campylobacter jejuni, Salmonella enterica, Bacteroides fragilis, Vibrio cholera, and Escherichia coli, but in a low abundance (0.1% or less) (29)

Which Bacterial Species Are Recognized as Gut Pathogens?

Clostridia have the potential for harmful pathogenic effects. Indigenous pathobionts are e.g. Clostridium difficile and vancomycin-resistant enterococci (30)

How Do Pathogens Affect Human Health?

Pathogens impact health either directly by invading the host or by eliciting an acute inflammatory immune response (12).

How Do Foodborne Pathogens Cause Mammalian Cell Death?

Many foodborne bacterial pathogens, including the non-typhoidal serovars of Salmonella enterica (Salmonella ), directly or indirectly induce mammalian cell death (31)

Inflammatory Responses to Pathogens are More Dangerous in Immunocompromised People

This paradigm of inflammatory immune responses is even more consequential in people who may be immunocompromised (12)

Which Bacterial Taxa Include Known Human Pathogens?

But of the domain Bacteria the bacteroidetes (phylum), Alfaproteobacteria (class), Betaproteobacteria (class), gammaproteobacteria (class), deltaproteobacteria (class), chlamydiae (phylum), Spirochaetes / Spirochaetota (phylum), clostridia (class), bacilli (class) and actinobacteria (phylum) in which known human pathogens exist (32)

How Do Pathogenic Bacteria Use Lectins to Cause Disease?

Pathogenic bacteria use lectins to cause disease. Lectins bind to sugars on host cells. These sugars include cell-surface receptors, N- and O-linked glycans, glycolipids, and glycosaminoglycans (1, 2)

Do ABH and Lewis Blood Group Antigens Increase Infection Risk?

Some bacteria target histo-blood group antigens, such as A, B, and H blood-group antigens and Lewis antigens. As a result, people who carry these antigens may be more vulnerable to infection (1, 2)

How Do Bacterial Lectin Interactions Promote Infection?

These interactions help bacteria recognize and attach to tissues. They also help bacteria avoid the immune system, form biofilms, remain in the body, and damage host cells (3).

References

(1) Heggelund et al. 2017 Curr Opin Struct Biol 44: 190-200
(2) Cooling 2015 Clin Microbiol Rev 28: 801-870
(3) Fares et al. 2025 Trends in Microbiology 33(8): 839-852
(4) Microbiology by numbers 2011 Nat Rev Microbiol 9: 628
(5) WHO Report to the Secretary-General of the United Nations 2019
(6) Acosta & Alonzo 3rd 2023 J Innate Immun 15: 782-803
(7) Touati et al. 2025 Pathogens 14: 386
(8) Nair et al. 2026 Front Microbiol 17: 1783835
(9) Safi et al. 2023 Immunol Rev 314:
(10) Kim et al. 2020c Cell Host & Microbe 27: 345-357
(11) Zou et al. 2019b Nat Biotechnol 37: 179-185
(12) Jash & Sharma 2022 Pathogens 11: 193
(13) Murray et al. 2022 Lancet 399: 629-55
(14) Wang et al. 2023b Cell Host & Microbe 31(8): 1359–1370
(15) Tawk et al. 2023 Cell Host & Microbe 31(5): 811-826
(16) Dunny et al. 2008 Bioessays 30: 296-298
(17) Flemming et al. 2016 Nat Rev Microbiol 14: 563-575
(18) Sionov & Steinberg 2022 Microorganisms 10: 1239
(19) Meng et al. 2020 J Appl Microbiol 129(4): 787-805
(20) Segrist & Cherry 2020 Cell Host & Microbe 27: 329-344
(21) Randow et al. 2013 Science 340: 701-706
(22) Huang et al. 2019 Curr. Opin. Immunol. 60: 71-80
(23) Patel & Minn 2018 Immunity 48: 417
(24) Passalacqua et al. 2016 Microbiol Spectrum 4(3): VMBF-0027-2015
(25) Bragonzi et al. 2012 PLoS One 7: e52330
(26) Costello et al. 2014 Microbiology (Reading) 160: 1474-1487
(27) Price et al. 2011 Science 334: 1553–1557
(28) Niu et al. 2012 Proc. Natl. Acad. Sci. USA 109: 20800–20807
(29) The Human Microbiome Project Consortium 2012 Nature 486(7402): 207-214
(30) Salminen et al. 1998
(31) Storek & Monack 2015 Immunol Rev 265: 112-129
(32) Eckburg et al. 2003

see also:
Acinetobacter baumannii
Antibiotic resistance
Bacteria & Carcinogenesis / Oncogenesis / Tumorigenesis
Bacterial Biofilm / Microbial Biofilm (BF)
Bacterial cellular morphologies
Bacterial Sensing / Quorum Sensing (QS) system
Bad Guys (certain harmful bacteria)
Enteric pathogens
Exometabolome
Glutathione
Opportunistic infections