Final answer:
Infections caused by antibiotic-resistant bacteria and difficult-to-treat fungal infections can lead to fatalities because these microorganisms do not respond well to traditional antibiotic treatments.
Step-by-step explanation:
Antibiotic-resistant bacteria cause infections in humans that do not yield to standard antibiotics and often end in fatality. At the current time, serious problems are arising due to bacteria such as 'golden staphs', and those responsible for tuberculosis and pneumonia, developing resistance to antibiotics that were previously effective. This resistance can be attributed to various factors, including the excessive use of antibiotics leading to the natural selection of resistant strains. Furthermore, fungal infections are particularly difficult to treat because they are eukaryotes like humans and do not respond to traditional antibiotics, which can be deadly especially for those with compromised immune systems.