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AmpC [beta]-lactamases are mostly chromosomally mediated cephalosporinases produced by Gram-negative bacteria that make them resistant to a wide range of beta lactam drugs thereby leading to serious problem in therapy.
Genes encoding AmpC cephalosporinases (AmpC) may be chromosomal or plasmid-based in origin, whereas genes encoding extended-spectrum [beta]-lactamases (ESBLs) are most often carried on mobile genetic elements, such as plasmids or transposons, and cause resistance to all [beta]-lactams except carbapenems and cephamycins (1-4).
1) Reports have established regarding the development of resistance to these inhibitors which might be caused by the hyperproduction of unmodified TEM(TEM named after the patient, Temoniera, from whom it was isolated)-type [beta]-lactamase, or modification of the outer membrane proteins, or production of OXA (Oxacillinase)-type enzymes, or hyperproduction of cephalosporinases.
EXCENELTM (Ceftiofur Sodium) is a new Beta-Lactam, cephalosporinase resistant antibiotic from the third generation of the cephalosporins, chemically ceftiofur is the sodium salt of (6R,7R)-7{[(2-amino-4thiozolyl)-Z- (methoxyimino)acetyl]amino}-3-{[(2-furanylcarbonyl)thio]-8-oxo-5-thia-1-azabicyclo[4.
anthracis genome sequence shows that this organism encodes two beta-lactamases: a penicillinase and a cephalosporinase.
The DDST was also performed on MH agar plates (bioMerieux) containing cloxacillin (150 mg/L) to inhibit cephalosporinase activity of natural producers of those inducible cephalosporinases.
The Carba NP test perfectly differentiates carbapenemase producers (Table 1) from strains that are carbapenem resistant due to non-carbapenemase-mediated mechanisms, such as combined mechanisms of resistance (outer-membrane permeability defect associated with overproduction of cephalosporinase and/or extended-spectrum P-lactamases) or from strains that are carbapenem susceptible but express a broad-spectrum [beta]-lactamase without carbapenemase activity (extended-spectrum [beta]-lactamase, plasmid and chromosome-encoded cephalosporinases) (Table 2).
NDM-1] gene are diverse and can harbor a high number of resistance genes associated with other carbapenemase genes (oxacillinase-48 [OXA-48] types, VIM types), plasmid-mediated cephalosporinase genes, ESBL genes, aminoglycoside resistance genes (16S RNA methylases), macrolide resistance genes (esterase), rifampin (rifampin-modifying enzymes) and sulfamethoxazole resistance genes as a source of multidrug resistance and pandrug resistance (16,17) (Figure 2, panel B).
Despite possessing the gene encoding cephalosporinase, ampC (1), wild strains of E.
AMC resistance mechanisms ([beta]-lactamase overproduction, AmpC cephalosporinase hyperproduction, and inhibitor-resistant penicillinases) (11) might be favored by strong AMC consumption.
Plasmids of this type were recently identified in the United States and in Italy carrying the AmpC-type cephalosporinase CMY2-encoding gene (10).