First Documented: 1886 Illness Caused: Lung infections, Pneumonia Antibiotic Resistance: Medium Virulence: Worrying Klebsiella pneumoniae can cause a range of infections and has proven to be very resistance to a range of antibiotics. Primarily affecting middle-aged and older men with weakened immune systems, this bacteria can be dangerous but is mostly ‘opportunistic’ and is far less likely to affect healthy adults. Due to its high levels of resistance, it is common in the US to perform tests to identify which strain is present in a patient to better inform doctors of how to treat them. This is slowing the rate at which resistance is built up but this bacteria is still of concern across the globe.