With the advent of the antibiotic era, antibiotic use and overuse has led to the rapid spread of acquired antibiotic resistance, creating a major threat to public health. It has been estimated that more than 2.8 million infections and 35,000 deaths per year in the United States are caused by antibiotic-resistant bacteria and fungi. In addition to increased morbidity and mortality, resistant infections also add considerable costs to the global healthcare system. 
The emergence and spread of new forms of resistance continues to alarm CDC experts, especially resistance shared through genetic mobile elements, as antibiotic-resistant microbes can transmit their resistance genes, increasing resistance. Carbapenem-resistant Enterobacteriaceae (CRE) has emerged worldwide as an urgent antibiotic resistance threat, leaving more toxic or less effective treatment options, such as colistin and tigecycline. Unfortunately, the recent emergence of tigecycline and colistin-resistant isolates further reduces the availability of ideal antibiotic agents to combat this “nightmare bacteria”.  Candida auris  is an emerging multidrug-resistant fungus that presents a serious global health threat. Besides causing severe infections,  C. auris  can be difficult to detect with standard laboratory methods and has caused outbreaks as it spreads easily between hospitalized patients and nursing home residents. Additionally,  Clostridioides difficile  causes life-threatening diarrhea and colitis (inflammation of the colon), mostly in people who have had both recent medical care and antibiotics. Recent studies on resistance mechanisms, epidemiology, diagnosis and treatment of bacteria and fungi are making significant progress on combating these new threats, and now is the time to arrange a Research Topic to present and highlight these novel findings. 
The present Research Topic of  Frontiers in Medicine  will feature authoritative articles on etiology, pathogenesis, virulence, resistance, diagnosis, treatment and control of bacteria and fungi. We seek an interdisciplinary approach, with authors acting as researchers in academic institutes, public health organizations, and hospitals, as well as those who work in fields including environmental, veterinary, molecular, and clinical microbiology. We welcome papers from leading researchers in the fields of the following themes:
• Carbapenem-resistant  Enterobacterales , Carbapenem-resistant  Acinetobacter baumannii , Carbapenem-resistant  Pseudomonas aeruginosa 
• Tigecycline/Colistin-resistant gram-negative bacteria
• New ß-Lactam-ß-Lactamase Inhibitor Combinations (such as CAZ-AVI, ATM-AVI) -resistant gram-negative bacteria
• Multidrug-resistant  Candida auris 
• Drug-resistant  Aspergillus fumigatus ,  Candida albicans ,  Cryptococcus , and dimorphic fungi
•  Clostridioides difficile 
• Methicillin-resistant  Staphylococcus aureus  (MRSA) 
• Vancomycin-resistant  Enterococcus  (VRE)
• Linezolid-resistant gram-positive bacteria
• Other topics on emerging and existing antibiotic resistance in bacteria and fungi
With the advent of the antibiotic era, antibiotic use and overuse has led to the rapid spread of acquired antibiotic resistance, creating a major threat to public health. It has been estimated that more than 2.8 million infections and 35,000 deaths per year in the United States are caused by antibiotic-resistant bacteria and fungi. In addition to increased morbidity and mortality, resistant infections also add considerable costs to the global healthcare system. 
The emergence and spread of new forms of resistance continues to alarm CDC experts, especially resistance shared through genetic mobile elements, as antibiotic-resistant microbes can transmit their resistance genes, increasing resistance. Carbapenem-resistant Enterobacteriaceae (CRE) has emerged worldwide as an urgent antibiotic resistance threat, leaving more toxic or less effective treatment options, such as colistin and tigecycline. Unfortunately, the recent emergence of tigecycline and colistin-resistant isolates further reduces the availability of ideal antibiotic agents to combat this “nightmare bacteria”.  Candida auris  is an emerging multidrug-resistant fungus that presents a serious global health threat. Besides causing severe infections,  C. auris  can be difficult to detect with standard laboratory methods and has caused outbreaks as it spreads easily between hospitalized patients and nursing home residents. Additionally,  Clostridioides difficile  causes life-threatening diarrhea and colitis (inflammation of the colon), mostly in people who have had both recent medical care and antibiotics. Recent studies on resistance mechanisms, epidemiology, diagnosis and treatment of bacteria and fungi are making significant progress on combating these new threats, and now is the time to arrange a Research Topic to present and highlight these novel findings. 
The present Research Topic of  Frontiers in Medicine  will feature authoritative articles on etiology, pathogenesis, virulence, resistance, diagnosis, treatment and control of bacteria and fungi. We seek an interdisciplinary approach, with authors acting as researchers in academic institutes, public health organizations, and hospitals, as well as those who work in fields including environmental, veterinary, molecular, and clinical microbiology. We welcome papers from leading researchers in the fields of the following themes:
• Carbapenem-resistant  Enterobacterales , Carbapenem-resistant  Acinetobacter baumannii , Carbapenem-resistant  Pseudomonas aeruginosa 
• Tigecycline/Colistin-resistant gram-negative bacteria
• New ß-Lactam-ß-Lactamase Inhibitor Combinations (such as CAZ-AVI, ATM-AVI) -resistant gram-negative bacteria
• Multidrug-resistant  Candida auris 
• Drug-resistant  Aspergillus fumigatus ,  Candida albicans ,  Cryptococcus , and dimorphic fungi
•  Clostridioides difficile 
• Methicillin-resistant  Staphylococcus aureus  (MRSA) 
• Vancomycin-resistant  Enterococcus  (VRE)
• Linezolid-resistant gram-positive bacteria
• Other topics on emerging and existing antibiotic resistance in bacteria and fungi