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.

Altered penicillin-binding proteins in methicillin-resistant strains of Staphylococcus aureus.

Abstract: The penicillin-binding proteins (PBPs) of a methicillin-resistant (MR) and a methicillin-susceptible (MS) Staphylococcus aureus were compared by various approaches involving the use of high-specific-activity [3H]penicillin as a reagent. The MR and MS strains were found to contain PBPs of the same number and electrophoretic mobilities. However, saturation of PBPs 1, 2, and 3 by methicillin in the MR strain required the use of several thousands of micrograms of antibiotic per milliliter, whereas 0.2 to 0.4 micrograms of methicillin per ml was sufficient to effectively compete with [3H]penicillin for the PBPs for the MS strain. Additional experiments indicate that these differences most likely reflect a greatly decreased affinity of the PBPs of the MR strain as compared to those of the MS strain. Shift of the pH of the culture medium of the MR strain from pH 7.0 to 5.2 resulted in an immediate drop in phenotypic resistance to methicillin (from a minimal inhibitory concentration value of 3,200 micrograms/ml at pH 7.0 to 0.8 microgram/ml at pH 5.2). Examination of the methicillin affinities of PBPs in MR bacteria grown at pH 5.2 showed the presence of the same low-affinity PBPs as in bacteria grown at pH 7.0. Thus, the pH-dependent resensitization to methicillin cannot be explained by a parallel increase in the antibiotic affinities of the PBPs.

The response of symptomatic neurosyphilis to high-dose intravenous penicillin G in patients with human immunodeficiency virus infection.

Abstract: Background Infection with the human immunodeficiency virus (HIV) may affect both the natural course of syphilis and the response to treatment. We examined the response to treatment with high-dose penicillin G in HIV-infected patients with symptomatic neurosyphilis. Methods Neurosyphilis was defined by reactivity in serum treponemal tests for syphilis, neurologic manifestations consistent with neurosyphilis, and a positive Venereal Disease Research Laboratory (VDRL) test on cerebrospinal fluid. We identified 11 HIV-infected patients with symptomatic neurosyphilis; 5 had been treated previously for early syphilis with penicillin G benzathine. Patients were treated with 18 million to 24 million units of penicillin G per day administered intravenously for 10 days. Cerebrospinal fluid was examined approximately 6 and 24 weeks after treatment, when the polymerase chain reaction and rabbit inoculation were used to detect Treponema pallidum. Results In four of the seven patients studied 24 weeks after treatment, ...

Treatment and diagnosis of infections caused by drug-resistant Streptococcus pneumoniae.

Abstract: Drug-resistant strains of Streptococcus pneumoniae have now been reported from all continents and have become the predominant pathogens in some areas; many strains are resistant to multiple agents. Because of the importance of pneumococci in the etiology of meningitis, the criteria used to assess susceptibility are conservative: strains with minimal inhibitory concentrations (MICs) of penicillin G of less than or equal to 0.06 microgram/mL are regarded as susceptible, those with MICs of 0.1-1 microgram/mL are considered intermediately resistant, and those with MICs of greater than 1 microgram/mL are designated highly resistant. The diagnosis, treatment, and prevention of infections due to resistant pneumococci are the subjects of this review. Methods of susceptibility testing have now been well defined for pneumococci. Screening for penicillin resistance with 1-microgram oxacillin disks is recommended for all clinically significant isolates. The activity of other beta-lactam agents against penicillin-resistant strains has been documented, and the MICs of a number of non-beta-lactam agents have been determined as well. Treatment of resistant pneumococcal infections depends on the site of infection, the degree of resistance to penicillin G, the resistance of the infecting strain to other agents, the severity of disease, the presence of underlying conditions, and the dose and route of administration of antimicrobial agents. Current recommendations for treatment are based on retrospective case studies, and adequate prospective studies providing more definitive data are needed. Prevention of pneumococcal infections in children less than 2 years of age and in the elderly remains a problem. Improved vaccines must be developed for this purpose.

Antimicrobial resistance of 1,113 Streptococcus pneumoniae isolates from patients with respiratory tract infections in Spain: results of a 1-year (1996-1997) multicenter surveillance study. The Spanish Surveillance Group for Respiratory Pathogens.

Abstract: A nationwide susceptibility surveillance of 1,113 Streptococcus pneumoniae isolates was carried out and found the following percentages of resistance: cefuroxime, 46%; penicillin, 37%; macrolides, 33%; aminopenicillins, 24%; cefotaxime, 13%; and ceftriaxone, 8%. A significant (P < 0.05) seasonality pattern for β-lactam antibiotics was observed. Resistance to macrolides was higher (P < 0.05) in middle-ear samples. Higher percentages of resistance to cefuroxime and macrolides were observed among penicillin-intermediate and -resistant strains, whereas high frequencies of resistance to aminopenicillins and expanded-spectrum cephalosporins were observed only among penicillin-resistant strains.

Evaluation of Antibiotic Diffusion into Cardiac Vegetations by Quantitative Autoradiography

Abstract: The reason bacterial endocarditis is difficult to cure has been controversial for many years. One explanation could be that antibiotic diffusion inside the vegetations is heterogeneous. This hypothesis was investigated by means of an autoradiographic study of diffusion of labeled antibiotics into large infected cardiac vegetations of nutritionally variant Streptococcus endocarditis in rabbits. Ten days after infection, 653 microCi of [3H]penicillin, 410 microCi of [3H]tobramycin, or 174 microCi of [14C]teicoplanin were injected iv over 30 min. Thirty minutes after the end of infusion (T30), vegetation/blood radioactivity ratios were 2.48 +/- 1.27, 2.49 +/- 0.67, and 3.94 +/- 1.19 for penicillin, tobramycin, and teicoplanin, respectively. Autoradiography clearly showed that distribution of the three drugs was different: Tobramycin was homogeneously distributed; penicillin was more concentrated at the periphery but still reached the center of vegetations; teicoplanin was concentrated only at the periphery. The same distribution pattern was observed with teicoplanin at T120 (i.e., one t1/2 beta later) and also after simultaneous infusion of a therapeutic dose (15 mg/kg) of cold teicoplanin. The diffusion gradient exhibited by some antibiotics could explain the difficulty in sterilizing vegetations despite high local concentrations, and the deleterious effect of the size of the vegetations on the therapeutic response.