Topic
Penicillin
About: Penicillin is a research topic. Over the lifetime, 17916 publications have been published within this topic receiving 368480 citations. The topic is also known as: penicillin antibiotic & PCN.
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325 citations
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325 citations
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TL;DR: The borderline in vitro susceptibility or resistance to PRPs in most of these S. aureus strains is mediated by beta-lactamase and they are not heteroresistant or intrinsically resistant.
Abstract: We showed that most Staphylococcus aureus strains that have borderline or intermediate susceptibility to the penicillinase-resistant penicillins (PRPs) react this way because of the activity of their beta-lactamase on these antimicrobial agents These strains produced large amounts of staphylococcal beta-lactamase that rapidly hydrolyzed penicillin and partially hydrolyzed the PRPs Susceptibility to hydrolysis was penicillin greater than oxacillin greater than cephalothin greater than methicillin The borderline results and the hydrolysis could be prevented by the beta-lactamase inhibitors clavulanic acid and sulbactam For intrinsically methicillin-resistant (heteroresistant) S aureus, the inhibitors reduced the penicillin MICs, but the strains remained resistant to all the beta-lactam antimicrobial agents, including penicillin We conclude that the borderline in vitro susceptibility or resistance to PRPs in most of these S aureus strains is mediated by beta-lactamase and they are not heteroresistant or intrinsically resistant We do not know whether this in vitro resistance is expressed clinically
321 citations
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TL;DR: With the continuing rise in resistance, judicious use of oral antimicrobial agents is necessary in all age groups.
Abstract: The susceptibilities of Streptococcus pneumoniae (1,476 strains) and untypeable Haemophilus influenzae (1,676 strains) to various oral β-lactam, macrolide-azalide, and fluoroquinolone antimicrobial agents were determined by broth microdilution. Organisms were isolated from specimens obtained from outpatients in six geographic regions of the United States. MIC data were interpreted according to pharmacodynamically derived breakpoints applicable to the oral agents tested. Among H. influenzae strains, 41.6% were β-lactamase positive. Virtually all H. influenzae strains were susceptible to amoxicillin-clavulanate (98%), cefixime (100%), and ciprofloxacin (100%), while 78% were susceptible to cefuroxime, 57% were susceptible to amoxicillin, 14% were susceptible to cefprozil, 9% were susceptible to loracarbef, 2% were susceptible to cefaclor, and 0% were susceptible to azithromycin and clarithromycin. Among S. pneumoniae isolates, 49.6% were penicillin susceptible, 17.9% were intermediate, and 32.5% were penicillin resistant, with penicillin MICs for 50 and 90% of the isolates tested of 0.12 and 4 μg/ml, respectively. Overall, 94% of S. pneumoniae isolates were susceptible to amoxicillin and amoxicillin-clavulanate, 69% were susceptible to azithromycin and clarithromycin, 63% were susceptible to cefprozil and cefuroxime, 52% were susceptible to cefixime, 22% were susceptible to cefaclor, and 11% were susceptible to loracarbef. Although ciprofloxacin has marginal activity against S. pneumoniae, no high-level fluoroquinolone-resistant strains were found. Significant cross-resistance was found between penicillin and macrolides-azalides among S. pneumoniae isolates, with 5% of the penicillin-susceptible strains being macrolide-azalide resistant, compared with 37% of the intermediate isolates and 66% of the resistant isolates. Resistance was highest in S. pneumoniae isolates from patients younger than 10 years of age, middle ear and paranasal sinus specimens, and the southern half of the United States. With the continuing rise in resistance, judicious use of oral antimicrobial agents is necessary in all age groups.
320 citations
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TL;DR: Probably the MRSA PBP evolved by recombination of two genes: an inducible type I penicillinase gene and a PBP gene of a bacterium, causing the formation of a β‐lactam‐inducible MRSAPBP.
312 citations