B. Increased human mortality
Higher case fatality rates are seen for human patients infected with AMR organisms compared with those infected with antibiotic sensitive organisms12.
Multi-drug Resistant Salmonella
Helms et al. (2002) found that patients infected with pansusceptible Salmonella Typhimurium were 2.3 times more likely to die within 2 years after infection than persons in the general Danish population, and that patients infected with strains resistant to ampicillin, chloramphenicol, streptomycin, sulfonamide and tetracycline were 4.8 times (95% CI 2.2 to 10.2) more likely to die within 2 years. Furthermore, they established that quinolone resistance in this organism was associated with a mortality rate 10.3 times higher than the general population13. Evidence is also mounting that, for some pathogens, increases in virulence often accompany acquisition of resistance.
Physicians rely on empirical treatments when therapy is urgent and cannot wait for laboratory testing; however, empirical antibiotic treatments fail if the pathogen has gained resistance. Examples are the failure of quinolones in treating invasive salmonellosis or the failure of vancomycin in managing infection with nosocomial vancomycin-resistant enterococci (VRE).
While some antibiotics are used empirically as the “first line of defense”, other more toxic, more expensive or narrow spectrum antibiotics are reserved for use as the ”last line of defense” against infections due to resistant pathogens. However, resistance to even the “last defense” antibiotics has now been documented., e.g. vancomycin failure in treating for methicillin-resistant Staphylococcus aureus (MRSA).
Additionally, the acquisition of AMR traits by some pathogens may be accompanied by additional pathogenicity and virulence genetic factors that increase the probability of patient death.
The Impact Of Antimicrobial Resistance In The Developing World
The impact of AMR to the older and cheaper antibiotics is probably greater in developing countries where more expensive treatment alternatives are unavailable or unaffordable. It is impossible to quantify the increased human morbidity and mortality occurring in developing countries due to treatment failure with older antibiotics such as tetracyclines and penicillins that may be the only antibiotics available to people living in poverty.
In some instances, death may occur due to therapeutic failure of the antibiotic of last resort. These types of drugs are usually reserved as the last choice when other less toxic, less expensive drugs have been ineffective. There are cases however, in which resistance to these antibiotics of last resort have been documented. In such instances, treatment failure can be fatal.
Empirical treatments are experienced-based, therapeutic regimens generally administered prior to confirmatory diagnosis.