The main resistance mechanism of bacteria to penicillin is based on its own production of enzymes, the
penicillinases, which degrade the penicillin before it can have effect (Daum, 2007).
The presence of [beta]-lactamase confers resistance to
penicillinase -labile penicillins (e.g.
Staphylococcal resistance to penicillin is mediated by
penicillinase (a form of [beta]-lactamase) production: an enzyme that cleaves the P-lactam ring of the penicillin molecule, rendering the antibiotic ineffective.
Inhibition of
penicillinase by epigallocatechin gallate resulting in restoration of antibacterial activity of penicillin against penicillinase-proclucing Staphylococcus aureus.
The injection is used to treat infections caused by
penicillinase producing staphylococci, which have shown susceptibility to the drug.
However, a combination of a new cephalosporinase and
penicillinase provides inactivation of a broad spectrum of 13-lactam antibiotics, including cephalosporins of the third and fourth generation.
Reductions were found for all classes of antibiotics other than
penicillinase resistant penicillins but were largest and significant individually for phenoxymethylpenicillins (penicillin V) (7.3%, 0.4 - 13.7%) and macrolides (7.7%, 1.1 - 13.8%).
Further, Shah and Narang (26) reported that Gram-positive organisms were highly susceptible to meropenem including Staphylococci (
penicillinase negative and positive), Coagulase-Negative staphylococci (CONS), Streptococci, Enterococcus.
It holds the advantage of being a superb inducer of the mecA gene and is less affected by
penicillinase hyper-producing isolates than oxacillin.
Acquisition of resistance by transduction is common in gram positive bacteria like Staphylococcus (
penicillinase plasmid); where as in gram negative bacteria conjugation is a major mechanism of transfer of drug resistance and can occur in unrelated genera.