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.

Antimicrobial susceptibility of viridans group streptococci in Taiwan with an emphasis on the high rates of resistance to penicillin and macrolides in Streptococcus oralis.

Abstract: The in-vitro susceptibilities of 13 antimicrobial agents were determined for 207 isolates of viridans group streptococci recovered from patients with significant infections in Taiwan during 1995 and 1997. Variable degrees of susceptibility existed among nine species. High-level penicillin resistance (MIC > or = 4.0 mg/L) was found most frequently in Streptococcus oralis (35%), followed by Streptococcus mitis (20%) and Streptococcus salivarius (8%). However, S. salivarius showed the lowest rate of susceptibility to penicillin (50%). Macrolide resistance also occurred most frequently in S. oralis isolates (55%) but in none of Streptococcus mutans. Penicillin and macrolides tended to be less active against isolates recovered from non-invasive sites than against those isolated from invasive sites. Imipenem was the most active beta-lactam against penicillin-resistant isolates. Ofloxacin, vancomycin and teicoplanin showed good in-vitro activity against all isolates, with MIC90s of 2, 1 and 0.25 mg/L, respectively. None of these isolates displayed high-level resistance to gentamicin and most isolates were susceptible to chloramphenicol. These results indicate the species-related variability of susceptibility, especially to penicillin, macrolides and tetracycline. In addition to S. mitis, S. oralis also displayed high rates of resistance to penicillin and macrolides. The difference in susceptibilities between species of viridans streptococci indicates the importance of accurate identification and the need for continuing surveillance of antimicrobial resistance.

Increased production of penicillin-binding protein 2, increased detection of other penicillin-binding proteins, and decreased coagulase activity associated with glycopeptide resistance in Staphylococcus aureus.

Abstract: The mechanism of glycopeptide resistance in the genus Staphylococcus is unknown. Since these antimicrobial compounds act by binding the peptidoglycan precursor terminus, the target of transglycosylase and transpeptidase enzymes, it was hypothesized that resistance might be mediated in Staphylococcus aureus by increased production or activity of these enzymes, commonly called penicillin-binding proteins (PBPs). To evaluate this possibility, glycopeptide-resistant mutants were prepared by passage of several clinical isolates of this species in nutrient broth containing successively increasing concentrations of the glycopeptide vancomycin or teicoplanin. Decreased coagulase activity and increased resistance to lysostaphin were uniformly present in the vancomycin-resistant mutants. Peptidoglycan cross-linking increased in one resistant isolate and decreased in two resistant isolates. The amounts of radioactive penicillin that bound to each PBP in susceptible and resistant strains were compared; PBP2 production was also evaluated by Western blotting. Increased penicillin labeling and production of PBP2 were found in all resistant derivatives selected by either vancomycin or teicoplanin. Moreover, the increase in PBP2 penicillin labeling occurred early in a series of vancomycin-selected derivatives and was strongly correlated (r > 0.9) with the increase in vancomycin and teicoplanin MIC. An increase in penicillin labeling also occurred, variably, in PBP1, PBP3, and/or PBP4. These data demonstrate a strong correlation between resistance to glycopeptides and increased PBP activity and/or production in S. aureus. Such an increase could allow PBPs to better compete with glycopeptides for the peptidoglycan precursor.

Genetic relationships of penicillin-susceptible and -resistant Streptococcus pneumoniae strains isolated on different continents.

Abstract: Sixty-six strains of Streptococcus pneumoniae isolated in different parts of the world, 46 resistant and 22 susceptible to penicillin, were subdivided by multilocus enzyme electrophoresis into 28 distinct electrophoretic types (ETs). The ETs to which penicillin-susceptible strains were assigned differed from those containing resistant isolates of the same serotype. Five common clones could be recognized among the penicillin-resistant bacteria by combining the ETs, the antigenic properties of penicillin-binding proteins PBP 1a and 2b, and the tetracycline and chloramphenicol resistance profiles. Two clones were found in Finland and were associated with capsular serotypes 6B and 23F, respectively. Two clones were from Spain (type 6B and 9V, respectively). The fifth clone was isolated in South Africa and in Spain and contained both serotype 23F isolates and one type 19F strain. The other resistant strains were represented by rare isolates distributed among 12 other ETs, confirming that resistance to penicillin has evolved by multiple branches. Because capsular type was mixed in several ETs, the results also demonstrate that it may vary among very closely related pneumococci.

Post-antibiotic effects in experimental infection models: relationship to in-vitro phenomena and to treatment of infections in man

Abstract: Persistent suppression of bacterial growth, called the post-antibiotic effect (PAE), has been studied in six different animal infection models. Prolonged in-vivo PAEs are observed for all antimicrobials with staphylococci and for imipenem and inhibitors of protein and nucleic acid synthesis with streptococci and Gram-negative bacilli. Penicillins and cephalosporins produce short or no in-vivo PAEs with these latter organisms. The presence of neutrophils prolongs the in-vivo PAEs found with aminoglycosides and quinolones. Simulation of human pharmacokinetics also enhances the duration of in-vivo PAE for aminoglycosides. In-vivo PAEs tend to be longer than those observed in vitro. The in-vitro PAE for penicillin with streptococci has been observed in vivo in only one of four experimental infection models. The presence of a prolonged in-vivo PAE can allow wider dosing intervals. The primary clinical application of the in-vivo PAE has been with once-daily dosing of aminoglycosides.

A pharmacologic evaluation of penicillin in children with purulent meningitis

Abstract: We undertook a prospective study of the pharmacokinetics of penicillin G (administered intravenously every four hours for a total of b50,000 U per kilogram per day) in the cerebrospinal fluid of children with purulent meningitis. Both the absolute mean cerebrospinal-fluid penicillin concentration (0.8, 0.7 and 0.3 microgram per milliliter) and the percentage of the simultaneous serum penicillin concentration measurable in the cerebrospinal fluid (18.4, 9.9, 4.9 per cent) declined on the first, fifth and 10th days of therapy, respectively. A mean peak cerebrospinal-fluid penicillin concentration of 0.96 micrograms per milliliter was measured at least transiently on all three study days. This pharmacokinetic pattern correlated with the return of cerebrospinal-fluid protein concentration toward normal (P less than 0.01). Penicillin G in the dosage studied is adequate therapy for most streptococcal and meningococcal meningitis in children; an increased dosage may be necessary when the minimal inhibitory concentration of penicillin to the etiologic agent is unusually high.