This family of bacteria is typically found in your gut in a perfectly healthy state, according to WebMD, but certain types are resistant to antibiotics and, as a result, are responsible for a host of medical conditions. CRE is usually transmitted in hospitals or nursing homes (via medical equipment inserted into the body) and is typically not a problem for healthy people. When it is transmitted, though, CRE can cause life-threatening blood conditions for which there are no treatments.

If the name of this superbug looks familiar to you, it's probably because it reminds you of the word pneumonia — which makes sense, since Klebsiella pneumoniae is the bacteria that can cause pneumonia in the lungs, per Live Science. It can be found in human mouths, intestines, and skin, and only becomes problematic in a compromised immune system. People who are in hospitals are especially prone to pneumonia, which is one of the reasons that the CDC recommends strict hygiene rituals for hospital patients and professionals.

Fluconazole-resistant Candida is a bit of an outlier on this list since it's technically a fungus — not a bacterium — but the CDC considers it a superbug because it's becoming increasingly resistant to the drugs used to treat it, according to Reuters. When introduced to the bloodstream, Candida can cause serious infections to an already weak immune system.

Commonly known as MRSA, methicillin-resistant Staphylococcus aureus has made periodic headlines over the years. According to WebMD, MRSA often infects people immediately after surgery, spreading from a wound to surrounding tissues and blood. More recently, you've probably heard concerns about outbreaks at schools, particularly among athletes, because the infection can spread via skin-to-skin contact. You're more prone to get MRSA this way if you have a cut.

If you've ever experienced inexplicable GI symptoms after eating or drinking, they may have been caused by this bacteria. According to Reuters, drug-resistant campylobacter typically infects people through contaminated milk, water, or food. It causes all kinds of discomfort — diarrhea, cramps, and fever, to name a few.

If you're anything like me, you've heard of Salmonella mostly in reference to raw cookie dough, which should come as no surprise based on the Reuters description of this pathogen. Non-typhoidal Salmonella is a common food-borne bacteria that can be dangerous when it stops responding to antibiotics. The pathogen causes severe diarrhea, cramps, and fever.

As a group, Escherichia Coli are not necessarily bad for you, according to Live Science. The harmless strains live in the intestines of people and animals, and it's only certain types that can cause problems like diarrhea, urinary tract infections, pneumonia, and other respiratory illnesses. Shiga toxin-producing E.coli is one such harmful strain, and it's transmitted to humans when they eat contaminated food, drink raw milk or contaminated water, or otherwise come in contact with infected, well, feces. (Gross.) Antibiotic treatments are discouraged for this strain.

The name of this superbug is a mouthful, and it's a broad category of bacteria that can produce an antibiotic-destroying enzyme, per Reuters. If you've ever had a UTI, it may have been caused by a strain of ESBL. More serious bloodstream and lung infections can also result when these pathogens are spread through improperly washed hands and surfaces or (less frequently) food.

Maybe you didn't know it was a superbug at the time, but you probably did learn about Neisseria gonorrhoeae in health class. This bacteria causes gonorrhea, which is transmitted sexually, according to WebMD. Hundreds of thousands of people get gonorrhea annually via sexual contact, and the once effective antibiotics are no longer a surefire way to cure it.

Like other superbugs, vancomycin-resistant Enterococcus (VRE) aren't necessarily problematic... until they are. Reuters notes that Enterococci can live in intestines and the female genital tract without causing any problems, but if they spread to the bloodstream or through a medical catheter, they can cause infection. Even vancomycin — an extremely powerful antibiotic — can't fight certain strains.

You may have gotten your share of tuberculosis vaccines over the years, but there is, in fact, a rare type of the disease that is resistant to multiple antibiotics. Per Live Science, TB is "a contagious bacterial infection that involves the lungs, but can spread to other organs." It spreads through contaminated air, and people who have been infected with tuberculosis and don't take their medication are more likely to contract the drug-resistant variety.

People who are receiving medical care may be triggered to overgrow clostridium difficile — informally called C. diff — in the intestine, according to WebMD. Antibiotics and bacteria particles (left in bathrooms, on clothing, etc.) can also trigger overgrowth, which may cause life-threatening diarrhea.

Per Reuters, drug-resistant Streptococcus pneumoniae can cause pneumonia, upper respiratory infections, and meningitis. It's spread via human contact and becomes more problematic over time as certain strains develop resistance to multiple drugs.

Multidrug-resistant acinetobacter is found in soil and water, but can also live on human skin, according to WebMD. One strain in particular — Acinetobacter baumannii — is especially concerning as a hospital germ for patients who are already sick.