Bacterial infections are common, can add risk and cause harm to people who use drugs. Staphylococcus aureus (also known as S. aureus or ‘staph’) and Streptococcus pyogenes (also known as Group A Streptococcus or GAS) are bacteria of specific concern in people who inject drugs. This booklet gives information on these common bacteria, the harms they may cause and what can be done to reduce risk and harm.