Coming from the Wild: Multidrug Resistant Opportunistic Pathogens Presenting a Primary, Not Human-Linked, Environmental Habitat

Abstract

The use and misuse of antibiotics have made antibiotic-resistant bacteria widespread nowadays, constituting one of the most relevant challenges for human health at present. Among these bacteria, opportunistic pathogens with an environmental, non-clinical, primary habitat stand as an increasing matter of concern at hospitals. These organisms usually present low susceptibility to antibiotics currently used for therapy. They are also proficient in acquiring increased resistance levels, a situation that limits the therapeutic options for treating the infections they cause. In this article, we analyse the most predominant opportunistic pathogens with an environmental origin, focusing on the mechanisms of antibiotic resistance they present. Further, we discuss the functions, beyond antibiotic resistance, that these determinants may have in the natural ecosystems that these bacteria usually colonize. Given the capacity of these organisms for colonizing different habitats, from clinical settings to natural environments, and for infecting different hosts, from plants to humans, deciphering their population structure, their mechanisms of resistance and the role that these mechanisms may play in natural ecosystems is of relevance for understanding the dissemination of antibiotic resistance under a One-Health point of view.

Evolution of Habitat-Dependent Antibiotic Resistance in Pseudomonas aeruginosa

“… Pseudomonas aeruginosa is a nosocomial opportunistic pathogen ( 1 , 2 ), producing infections in immunocompromised patients and in people with underlying diseases ( 3 – 8 ). This bacterium is able to grow in several body locations, being one of the main causative agents of chronic infections in the lungs of cystic fibrosis (CF) or chronic obstructive pulmonary disease (COPD) patients ( 3 ) and also being a major cause of urinary tract infections (UTIs) ( 9 , 10 ).…”

Prevalence and Antimicrobial Resistance of Enterococcus Species: A Retrospective Cohort Study in Italy

“…received particular attention due to its ability to cause urinary tract infection, bacteremia, and infective endocarditis [ 8 , 9 ]. Enterococci are Gram-positive, opportunistic microorganisms that normally inhabit the human gastrointestinal tract [ 10 ]. Among Enterococcus spp., E. faecium and E. faecalis are the third leading cause of nosocomial infections after S. aureus and P. aeruginosa [ 11 ].…”

A systematic review of enteric pathogens and antibiotic resistance genes in outdoor urban aerosols

“…136 Overall, the majority of enteric bacteria and viruses reported in the studies targeted and detected commensal enteric microbiota or opportunistic pathogens that typically only cause disease in immunocompromised individuals. Recent evidence reveals the growing relevance of opportunistic pathogens in clinical settings, particularly in the context of their low susceptibility to antibiotics and environmental origins 137 . Frank pathogens, which cause disease even in immunocompetent individuals are less represented in the review, making up less than half (39%) of all unique microbes reported at the strain and species levels across all studies (Table 2).…”