Quinolones

Penicillins

Cephalosporins

chemically modify the antibiotic,  render it inactive through physical removal from the cell, or modify target site so that it is not recognized by the antibiotic.

Efflux pumps are high-affinity reverse transport systems located in the membrane that transport the antibiotic out of the cell.

A specific enzyme modifies the antibiotic in a way that it loses its activity. In the case of streptomycin, the antibiotic is chemically modified so that it will no longer bind to the ribosome to block protein synthesis.

ncreased production of the antibiotic’s target enzyme so that there are too many of them and the antibiotics cannot inactivate them all

methylation -- a process by which enzymes add a small molecular tag to a particular location on a nucleotide -- a molecule that is the structural unit of RNA and DNA

facilitates the proper functioning of the bacterial ribosome -- a gigantic macromolecular machine that is responsible for making proteins that bacteria need to survive

antibiotics bind to the ribosome, disrupting its function and thereby killing the bacteria

Conjugation: this is direct cell-to-cell contact between two cells through what is called a "conjugation tube". This tube allows for the transfer of genetic material (DNA, plasmids) to another cell so that it can integrate the resistance into its genome

when a cell dies the DNA that is left over can be absorbed by another cell near to it. When the cell dies, the bacterial wall breaks down and allows the material within to become accessible to other cells. When this material codes for genetic resistance to antibiotics, transfer occurs and the new cell is now resistant

Transduction: this occurs when genetic material is transferred from one cell to another through a bacteriophage. When bacteriophages infect cells and begin to proliferate in them, some bacterial DNA can sometimes be incorporated into the viral genome. When the bacteriophages are released and infect other cells, other cells can become resistant depending on what bacterial DNA was transferred

Most current bactericidal antimicrobials, which are the focus of this review, inhibit DNA synthesis, RNA synthesis, cell wall synthesis, or protein synthesis

Quinolones are derivatives of nalidixic acid, which was discovered as a byproduct of chloroquine (quinine) synthesis

Nalidixic acid and other first generation quinolones (i.e., oxolinic acid) are rarely used today owing to their toxicity17. Second (i.e., ciprofloxacin), third (i.e., levofloxacin) and fourth (i.e., gemifloxacin) generation quinolone antibiotics (Table 1) can be classified based on their chemical structure along with qualitative differences in how these drugs kill bacteria

Cocci are spherical cells, bacilli are rod-shaped. Bacteria of either shape that have thick cell walls are termed gram positive because of the way they take up the Gram stain. Those with thin cell walls are termed gram negative

Spirochaetes: corkscrew-shaped bacteria that fall into three species, all of which cause specific diseases

Rickettsia: bacteria from the Rickettsiaceae family, which can only live and survive inside other living cells

a recent database lists the existence of more than 20,000 potential resistance genes (r genes) of nearly 400 different types, predicted in the main from available bacterial genome sequences

produced a nine-minute animation