Biomaterial Database

Suppression of intrinsic resistance to methicillin and other penicillins in Staphylococcus aureus. 1972

L D Sabath, and S J Wallace, and D A Gerstein

The pH of the medium in which staphylococcal susceptibility to penicillins was determined was found to make a profound difference (128- to 8,000-fold) in the expression of "intrinsic" resistance, whereas beta-lactamase-mediated resistance was only slightly affected by pH; methicillin-resistant staphylococci that are beta-lactamase-negative are models of pure intrinsic resistance, and the common beta-lactamase-producing organisms (methicillin-susceptible) are examples of pure beta-lactamase-mediated resistance. Methicillin-resistant staphylococci were unable to express their resistance at pH 5.2. However, growth of methicillin-resistant organisms in acid (pH 5.2) medium, followed by susceptibility testing at pH 7.4, showed no elimination of the genotype for intrinsic resistance, indicating that the pH effect was due to suppression, rather than to elimination of the gene determining the intrinsic resistance. These pH changes had little effect on the susceptibility of staphylococci that possessed neither intrinsic resistance nor beta-lactamase-mediated resistance. Thus, the suppression of "intrinsic" resistance was highly specific, and probably not the result of a change in ionization of the antibiotic, which would have been expected to affect all cells essentially equally. It is unlikely that foci of inflammation in man become sufficiently acid to suppress methicillin resistance of the staphylococci causing infection and inflammation.

UI	MeSH Term	Description	Entries
D008712	Methicillin	One of the PENICILLINS which is resistant to PENICILLINASE but susceptible to a penicillin-binding protein. It is inactivated by gastric acid so administered by injection.	Penicillin, Dimethoxyphenyl,Methicillin Hydrate, Monosodium Salt,Methicillin Monohydrate, Monosodium Salt,Methicillin Sodium,Meticillin,Metin,Staphcillin,Dimethoxyphenyl Penicillin
D008826	Microbial Sensitivity Tests	Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).	Bacterial Sensitivity Tests,Drug Sensitivity Assay, Microbial,Minimum Inhibitory Concentration,Antibacterial Susceptibility Breakpoint Determination,Antibiogram,Antimicrobial Susceptibility Breakpoint Determination,Bacterial Sensitivity Test,Breakpoint Determination, Antibacterial Susceptibility,Breakpoint Determination, Antimicrobial Susceptibility,Fungal Drug Sensitivity Tests,Fungus Drug Sensitivity Tests,Sensitivity Test, Bacterial,Sensitivity Tests, Bacterial,Test, Bacterial Sensitivity,Tests, Bacterial Sensitivity,Viral Drug Sensitivity Tests,Virus Drug Sensitivity Tests,Antibiograms,Concentration, Minimum Inhibitory,Concentrations, Minimum Inhibitory,Inhibitory Concentration, Minimum,Inhibitory Concentrations, Minimum,Microbial Sensitivity Test,Minimum Inhibitory Concentrations,Sensitivity Test, Microbial,Sensitivity Tests, Microbial,Test, Microbial Sensitivity,Tests, Microbial Sensitivity
D010403	Penicillin Resistance	Nonsusceptibility of an organism to the action of penicillins.	Penicillin Resistances,Resistance, Penicillin,Resistances, Penicillin
D010406	Penicillins	A group of antibiotics that contain 6-aminopenicillanic acid with a side chain attached to the 6-amino group. The penicillin nucleus is the chief structural requirement for biological activity. The side-chain structure determines many of the antibacterial and pharmacological characteristics. (Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed, p1065)	Antibiotics, Penicillin,Penicillin,Penicillin Antibiotics
D003470	Culture Media	Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN.	Media, Culture
D013210	Staphylococcus	A genus of gram-positive, facultatively anaerobic, coccoid bacteria. Its organisms occur singly, in pairs, and in tetrads and characteristically divide in more than one plane to form irregular clusters. Natural populations of Staphylococcus are found on the skin and mucous membranes of warm-blooded animals. Some species are opportunistic pathogens of humans and animals.