It is imperative that we first identify the difference between bacteria and viruses. Bacteria are single-celled microorganisms which can be beneficial or detrimental to our health. Bacteria can live in hosts (such as humans) but are also found in many environments across the planet. A virus, however, has no cell structure and requires a host in order to survive. Infections can be caused by viruses or bacteria (e.g., chest infections, UTIs (urinary tract infections), etc.), but the way we treat them differs hugely. Mammalian hosts can have vaccinations against numerous viruses in order to prevent their infection, but viruses such as the common cold are not curable in this way, and usually they just need time to pass before recovery. Bacteria, however, are combated using antibiotics. Later we'll discuss how antibiotics do this but it is important to note this key point: Viruses cannot be killed by antibiotics. 

The Good 

'Good' bacteria are found on our skin, in our airways and digestive systems. These bacteria are the first line of defence, like frontline soldiers, preventing viruses and other potentially detrimental things (such as pathogens) from getting further into our systems and making us unwell. The bacteria found naturally in each of us differs from person to person and is called our microbiome \citep{Eckburg_2005}. The microbiome helps to enhance our immune system. 

The Bad 

These are the disease-causing bacteria and usually become prevalent when our microbiomes are disrupted, meaning the 'bad' bacteria has more room to grow and are no longer regulated by the 'good' bacteria. Examples of disease-causing bacteria are  Staphylococcus aureus (causing infections such as pneumonia and ear infections ), Neisseria meningitidis (causing bacterial meningitis), Clostridium tetani (causing tetanus), etc.      

The Ugly 

The overuse of antibiotics has led to a very ugly situation. By removing good bacteria from our bodies, we've opened up an opportunity for bad bacteria to infiltrate, multiply and spread. 

How antibiotics work

The first antibiotic to be discovered/developed was penicillin (1920), helping countless people since then to overcome bacterial infections.

Pesky Bacteria: Antibiotic Resistance

It should be stated that it is the bacteria itself which becomes resistant, NOT us as individuals. For instance, gonorrhea is developing resistance to antibiotics used to treat it and is the 2nd most commonly reported infectious disease. \citet{cdc}
How do bacteria develop resistance? Unlike mammalian cells, bacterial cells divide and multiply rapidly. As a result, mutations will arise because the bacterial DNA is copied too quickly and thus, errors in the DNA sequence will occur.  
Bacteria also have this ‘nifty’ way of making non-resistant cells, resistant! As if they weren’t annoying enough already. The process is called horizontal gene transfer.