Glossary of terms

For those interested we have provided a compilation of the most common terms used. 

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Antibiotics or antibacterials are drugs used in the treatment and prevention of bacterial infections. They either kill the bacteria directly or stop if from reproducing.


An antimicrobial is an agent that kills or inhibits the growth of microorganisms and includes, among others, antibacterials, antimycobacterial drugs, antivirals, antifungals, and antiparasital drugs.


Antivirals are drugs used specifically for treating viral infections e.g. herpes infections, HIV.
They are not effective against  bacterial infections.


Bacteria constitute a large domain of prokaryotic microorganisms (unicellular organism without a nucleus). Human flora contains ten times more bacterial cells as there are human cells in the body, with the largest number being in the gut flora and on the skin.

The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, and some are even beneficial. However, several species of bacteria are pathogenic and cause infectious diseases, including cholera, syphilis, anthrax, and leprosy.

Bacteria are classified into two large groups; gram positive and gram negative based on a staining method which differentiates between bacteria by the chemical and physical properties of their cell wall.


Bacteremia is the presence of bacteria in the blood stream. Blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal.

Bacteria can enter the bloodstream as a severe complication of infections such as pneumonia or meningitis, during surgery, or due to catheters and other foreign bodies entering the arteries or veins.


A substance that kills bacteria is bactericidal, e.g. disinfectants, antiseptics, or antibiotics.


A biological or chemical agent that stops bacteria from reproducing while not necessarily killing them is bacteriostatic.


β-lactam antibiotics are a broad class of antibiotics, containing a β-lactam ring in their molecular structure, including penicillin derivatives, cephalosporins, monobactams, and carbapenems. β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics.


A biofilm is any group of microorganisms in which cells stick to each other and adhere to a surface. Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial and hospital settings. A grouping of bacterial cells that forms a film on a surface will provide extra protection against antibiotics.


A broad-spectrum antibiotic refers to an antibiotic that acts against a wide range of disease-causing bacteria. It acts against both Gram-positive and Gram-negative bacteria, in contrast to a narrow-spectrum antibiotic, which is effective against specific families of bacteria only.


The Centers for Disease Control and Prevention, the leading national public health institute of the United States. (www.cdc.gov)


The European Centre for Disease Prevention and Control. An independent agency of the European Union (EU) whose mission is to strengthen Europe's defences against infectious diseases. It was established in 2004 and is located in Solna, Sweden. (www.ecdc.europa.eu)


The 6 most important bacteria which are resistant to multiple medications (Enterococcus, Staphylococcus areus, Klebsiella, Acinetobacter baumannii, Pseudomanas aeruginosa, Enterobacter species) and cause most hospital-acquired infections.

Gain Act

The Generating Antibiotics Incentives Now (GAIN) Act, is a building block for creating the changes that will be needed to get antibiotic drug development back on track.

There is a consensus among the U.S. government, industry and the medical community that the failure of antibiotic development to keep pace with the evolution of bacterial pathogens constitutes a public health crisis, and that new regulatory policies and economic incentives are needed to create a continuous stream of new antibacterial products.

Gram-positive bacteria

Gram-positive bacteria are bacteria that give a positive result in the Gram stain test and look purple-coloured when seen through a microscope. Gram-positive bacteria are more receptive to antibiotics than gram-negative, due to the absence of the outer membrane.

Gram-negative bacteria

Gram-negative bacteria are a group of bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation, making positive identification possible.

Gram negative bacteria have a have a thinner cell wall than gram positive, but are surrounded by an outer membrane which is normally harder to overcome for antibiotics.

Multi drug resistance (MDR)

MDR is antimicrobial resistance exhibited by a species of microorganism to multiple antimicrobial drugs. The types most threatening to public health are MDR bacteria that resist multiple antibiotics. Recognizing different degrees of MDR, the terms extensively drug resistant (XDR) and pandrug-resistant (PDR) have been introduced.


Microbiology is the study of microscopic organisms, those being unicellular (single cell), multicellular (cell colony), or acellular. Microbiology encompasses numerous sub-disciplines including virology, mycology, parasitology, and bacteriology.


Methicillin-resistant Staphylococcus aureus (MRSA): a bacterium responsible for several difficult-to-treat infections in humans. MRSA is any strain of staphylococcus aureus that has developed resistance to beta-lactam antibiotics, which include the penicillins  and cephalosporins.

MRSA is especially troublesome in hospitals, prisons, and nursing homes, where patients with open wounds, invasive devices, and weakened immune systems are at greater risk of nosocomial infection than the general public. MRSA began as a hospital-acquired infection, but has developed limited endemic status and is now sometimes community-acquired and livestock-acquired.


Narrow-spectrum antibiotics are only active against a selected group of bacterial types and are used for the specific infection when the causative organism is known.


Nosocomial infections, also known as hospital-acquired infections, is an infection that is contracted from the environment of a healthcare facility. It can originate from the outside environment, another infected patient, staff that may be infected, or the source of the infection cannot be determined. In some cases the microorganism originates from the patient's own skin microbiota, becoming opportunistic after surgery or other procedures that compromise the protective skin barrier. Nosocomial infections can cause severe pneumonia and infections of the urinary tract, bloodstream and other parts of the body. Many types are difficult to treat with antibiotics, and. In addition, antibiotic resistance can complicate treatment.


The ability of a bacterium to cause disease in a human.


Bacteria needing a much higher dose of an antibiotic than is considered safe or tolerable for the patient. In the press, these organisms are often referred to as ‘superbugs’.


Antibiotic susceptibility or antibiotic sensitivity is the susceptibility of bacteria to antibiotics when given in the normal dose range. Because susceptibility can vary even within a species (with some strains being more resistant than others), antibiotic susceptibility testing is usually carried out to determine which antibiotic will be most successful in treating a bacterial infection.


Tuberculosis or TB (short for tubercle bacillus) is a widespread, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis generally affects the lungs, but can also affect other parts of the body. It is spread through the air when people who have an active TB infection cough, sneeze, or otherwise transmit respiratory fluids through the air. Most infections do not have symptoms, known as latent tuberculosis. About 10% latent infections eventually progresses to active disease which, if left untreated, kills more than 50% of those so infected.


Virulence is the degree to which the bacterium causes disease in a human.


The World Health Organization (WHO) is a specialized agency of the United Nations that is concerned with international public health. It was established in 1948, headquartered in Geneva, Switzerland. Its current priorities include communicable diseases, in particular AIDS, Ebola, malaria and tuberculosis. (www.who.int)


Extensively drug-resistant TB is a more serious form of MDR-TB caused by bacteria that do not respond to the most effective second-line anti-TB drugs, ofen leaving patients without any further treatment options.