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Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. [1] Their defining characteristic is that their cell envelope consists of a thin peptidoglycan cell wall sandwiched between an inner ( cytoplasmic ) membrane and an outer ...
A review of investigational antibiotics shows that several new agents will become available in the coming years, even though the pace of antimicrobial research has proven far too slow. Overuse of antimicrobial agents and problems with infection control practices have led to the development of multidrug-resistant gram-negative bacterial infections.
Some bacteria are naturally resistant to certain antibiotics; for example, gram-negative bacteria are resistant to most β-lactam antibiotics due to the presence of β-lactamase. Antibiotic resistance can also be acquired as a result of either genetic mutation or horizontal gene transfer. [156]
TEM-1 is the most commonly encountered beta-lactamase in gram-negative bacteria. Up to 90% of ampicillin resistance in E. coli is due to the production of TEM-1. [17] Also responsible for the ampicillin and penicillin resistance that is seen in H. influenzae and N. gonorrhoeae in increasing numbers.
Bacteria are capable of sharing these resistance factors in a process called horizontal gene transfer where resistant bacteria share genetic information that encodes resistance to the naive population. [6] Antibiotic inactivation: bacteria create proteins that can prevent damage caused by antibiotics, they can do this in two ways.
β-Lactam antibiotics are indicated for the prevention and treatment of bacterial infections caused by susceptible organisms. At first, β-lactam antibiotics were mainly active only against gram-positive bacteria, yet the recent development of broad-spectrum β-lactam antibiotics active against various gram-negative organisms has increased their usefulness.
A spheroplast (or sphaeroplast in British usage) is a microbial cell from which the cell wall has been almost completely removed, as by the action of penicillin or lysozyme. According to some definitions, the term is used to describe Gram-negative bacteria. [3] [4] According to other definitions, the term also encompasses yeasts.
For example, resistance to vancomycin in S. aureus is due to additional peptidoglycan synthesis that makes the cell wall much thicker preventing effective penicillin entry. [47] Resistance in Gram-negative bacteria is due to mutational variations in the structure and number of porins. [52]