What characteristic allows bacteria to be classified as multidrug-resistant?

Multidrug-resistant bacteria are defined by their ability to resist the effects of multiple antibiotic classes, making option C the correct choice. This characteristic is critical because it complicates treatment options for infections caused by such bacteria, leading to increased morbidity and mortality. When bacteria exhibit resistance to multiple antibiotics, it signals that they possess specific mechanisms, such as the production of enzymes that inactivate the drugs, alterations in drug targets, efflux pumps that expel antibiotics, or impermeable cell walls that prevent drug entry.

In contrast, the other options describe characteristics that do not specifically pertain to multidrug resistance. Surviving extreme temperatures does not correlate with antibiotic resistance; it relates more to environmental adaptations. Resistance to a single antibiotic indicates a bacterial strain that may still be treatable with other available options, thus not fitting the definition of multidrug resistance. Rapid replication is a general characteristic of bacteria and can occur regardless of their antibiotic resistance profile. Hence, the ability to resist multiple antibiotic classes is the defining feature of multidrug-resistant bacteria.