This informative video from the Centers for Disease Control and Prevention outlines the problem of antibiotic resistance, what the potential effects might be, and what might be done about it.
Antibiotic resistance has grown into a bigger problem because of a variety of factors that can feed into each other. When infrastructure is poor, and disease is common, it can lead to greater use of antibiotics, which promotes the evolution of bacterial strains that are resistant to drugs. Poor sanitation can also create an environment where pathogenic microbes can thrive and share resistance genes among one another. Those are only two examples of why antibiotic resistance is a rising threat to public health.
There could be a way out for humanity, however. Reducing the unnecessary use of antibiotics, and working to improve infrastructure are just some of the ways that we can fight the spread of antibiotic-resistant microbes.