PENICILLIN: ITS ANTIBACTERIAL EFFECT IN WHOLE BLOOD AND SERUM FOR THE HEMOLYTIC STREPTOCOCCUS AND STAPHYLOCOCCUS AUREUS

Anti-microbial Effects In Vitro and In Vivo of Alstonia scholaris

Alstonia scholaris could be used as a traditional medicinal plant in China for the treatment of acute respiratory, which might be caused by respiratory tract infections. The investigation tested the anti-infective effects of total alkaloids extract (TA) from leaves of A. scholaris, and as a result, TA inhibited herpes simplex virus type 1 (HSV-1), respiratory syncytial virus (RSV) and influenza A virus (H1N1) in vitro respectively. In addition, the survival days of mice were prolonged, and the lung weights and mortality of mice were decreased significantly, after oral administrated TA in H1N1 and beta-hemolytic streptococcus infectious models in vivo respectively. The finding supported partly the traditional usage of A. scholaris in the treatment of respiratory infections.

Biology and management of methicillin resistant Staphylococcus aureus in cystic fibrosis

Staphylococcus aureus is one of the earliest bacteria isolated from the respiratory tract in people with cystic fibrosis (CF). Its methicillin resistant form, MRSA, has gained attention due to the rapid increase in the last decades and worse outcomes with chronic infection. In the United States, prevalence of MRSA in CF is around 27%, but is much lower (3-18%) in most other countries. Methicillin is typically genetically encoded by the mecA gene, which encodes for an alternative penicillin binding protein (PRBa). This PRBa has low affinity to β-lactams, thereby enabling growth of S. aureus in the presence of penicillinase resistant penicillins and most other β-lactams. Non-mecA positive strains of MRSA, so-called borderline resistant (BORSA) have also been described. In addition to production of toxins, the virulence of S. aureus is conferred by its adaptability allowing persistence in face of antibiotic therapies and host defense. These adaptive growth mechanisms include small colony variants, biofilms, and growth under anaerobic conditions. Several reports have described successful eradication of MRSA, yet only two randomized trials of eradication during early infection have been conducted. A list of MRSA specific antibiotics with dosing relevant to CF patients is presented here. Many of these require special dosing in people with CF. Novel antibiotics are in trials for skin and soft tissue infections and it is unclear if and when those might be available for lung infections. Thus the best strategies for MRSA would be primary prevention.

β-Lactams and β-Lactamase Inhibitors: An Overview

β-Lactams are the most widely used class of antibiotics. Since the discovery of benzylpenicillin in the 1920s, thousands of new penicillin derivatives and related β-lactam classes of cephalosporins, cephamycins, monobactams, and carbapenems have been discovered. Each new class of β-lactam has been developed either to increase the spectrum of activity to include additional bacterial species or to address specific resistance mechanisms that have arisen in the targeted bacterial population. Resistance to β-lactams is primarily because of bacterially produced β-lactamase enzymes that hydrolyze the β-lactam ring, thereby inactivating the drug. The newest effort to circumvent resistance is the development of novel broad-spectrum β-lactamase inhibitors that work against many problematic β-lactamases, including cephalosporinases and serine-based carbapenemases, which severely limit therapeutic options. This work provides a comprehensive overview of β-lactam antibiotics that are currently in use, as well as a look ahead to several new compounds that are in the development pipeline.

Beta-lactam antibiotics: from antibiosis to resistance and bacteriology

This review focuses on the era of antibiosis that led to a better understanding of bacterial morphology, in particular the cell wall component peptidoglycan. This is an effort to take readers on a tour de force from the concept of antibiosis, to the serendipity of antibiotics, evolution of beta-lactam development, and the molecular biology of antibiotic resistance. These areas of research have culminated in a deeper understanding of microbiology, particularly in the area of bacterial cell wall synthesis and recycling. In spite of this knowledge, which has enabled design of new even more effective therapeutics to combat bacterial infection and has provided new research tools, antibiotic resistance remains a worldwide health care problem.

The rate of bactericidal action of penicillin in vitro as a function of its concentration, and its paradoxically reduced activity at high concentrations against certain organisms

1. The concentrations of penicillin G which (a) reduced the net rate of multiplication, (b) exerted a net bactericidal effect, and (c) killed the organisms at a maximal rate, have been defined for a total of 41 strains of α- and β-hemolytic streptococci, Staphylococcus aureus and Staphylococcus albus, Diplococcus pneumoniae, and the Reiter treponoma. 2. The concentration which killed the organisms at a maximal rate was 2 to 20 times the minimal effective level ("sensitivity" as ordinarily defined). With some organisms, even a 32,000-fold increase beyond this maximally effective level did not further increase the rate of its bactericidal effect. However, with approximately half the strains here studied (all 4 strains of group B β-hemolytic streptococci, 4 of 5 group C strains, 5 of 7 strains of Streptococcus fecalis, 2 of 4 other α-hemolytic streptococci, and 4 of 9 strains of staphylococci), when the concentration of penicillin was increased beyond that optimal level, the rate at which the organisms died was paradoxically reduced rather than increased, so that the maximal effect was obtained only within a relatively narrow optimal zone. 3. There were marked differences between bacterial species, and occasionally between different strains of the same species, not only with respect to the effective concentrations of penicillin, but also with respect to the maximal rate at which they could be killed by the drug in any concentration. Although there was a rough correlation between these two factors, there were many exceptions; individual strains affected only by high concentrations of penicillin might nevertheless be killed rapidly, while strains sensitive to minute concentrations might be killed only slowly. 4. Within the same bacterial suspension, individual organisms varied only to a minor degree with respect to the effective concentrations of penicillin. They varied strikingly, however, in their resistance to penicillin as measured by the times required to kill varying proportions of the cells.

Pharmacodynamic effects of subinhibitory antibiotic concentrations

The pharmacodynamics of antibiotics have become increasingly important for the determination of optimal dosing regimens. Studies over the past decade have demonstrated marked differences in the time course of antimicrobial activity for different classes of antibiotics both in vitro, in animals and in human trials. One of the explanations for the success of intermittent dosing regimens has been the delay in regrowth after the concentration has fallen under the MIC, the so called postantibiotic effect (PAE). In addition to the PAE, the success of discontinuous dosing regimens may be attributed to both the function of a normal host defence and to the effects of subinhibitory antibiotic concentrations (sub-MICs). It has been shown that there is a difference between the effects of sub-MICs following a suprainhibitory dose (postantibiotic sub-MIC effect; PA SME) and the effects of sub-MICs (SME) alone. It seems that the PA SME is more clinically relevant compared with the PAE, since exposure to suprainhibitory concentrations will always be followed by sub-MICs in vivo. A long PA SME could indicate that longer dosing intervals may be used for that antibiotic /bacterial combination and together with the known effects of sub-MICs on bacterial virulence and the influence of the immune system, it may explain the efficacy of antibiotics with short half-lives even of they are given infrequently.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Tests for bactericidal effects of antimicrobial agents: technical performance and clinical relevance

Bactericidal testing has been used for several decades as a guide for antimicrobial therapy of serious infections. Such testing is most frequently performed when bactericidal antimicrobial agent therapy is considered necessary (such as when treating infectious endocarditis or infection in an immunocompromised host). It has also been used to ensure that the infecting organism is killed by (not tolerant to) usually bactericidal compounds. However, few data are available to support the role of such tests in direct patient care. Several important variables affect the reproducibility of the test results; however, proposed reference methods are now available for performing the MBC test. With minor modifications, these can provide a standardized approach for laboratories that need to perform them. Currently, little evidence is available to support the routine use of such testing for the care of individual patients. However, testing of new (investigational) antimicrobial agents can be beneficial in determining their potential to provide bactericidal antimicrobial activity during clinical use. New methods to assess bactericidal activity are being developed, but as yet none have been rigorously tested in patient care settings; further, for most of these methods, little information is available as to which technical parameters affect their results. In clinical laboratories, all bactericidal tests must be performed with rigorously standardized techniques and adequate controls, bearing in mind the limitations of the currently available test procedures.

Occurrence and reproducibility of the "skip" phenomenon in bactericidal testing of Staphylococcus aureus

A "skip" phenomenon, in which subcultures to determine bactericidal endpoints show discordant results, can make bactericidal testing of Staphylococcus aureus difficult to interpret. Either a single or several consecutive concentrations may be skipped, with insignificant growth from these concentrations, but heavy growth from higher antimicrobic concentrations. Replicate macrodilution minimum bactericidal concentration testing of cephalothin against S. aureus was investigated to determine the frequency and reproducibility of the skip phenomenon in this test. In preliminary testing, the skip phenomenon occurred at 24 hr in 11 of the 30 tests performed on ten S. aureus strains. Incubation of tubes for 48 hr before subculture markedly reduced the number of tests containing a skip tube (four of 30). The skip phenomenon was not reproducible either within concurrent replicate testing or on repeat testing of the same isolate on subsequent days. The ten strains were retested in replicative trials using the macrodilution test comparing Mueller-Hinton broth (MHB) and MHB supplemented with Tween 80. The number of skips occurring in the supplemented broth test was the same (two of 22) at 24 hr as nonsupplemented broth. For reproducible results, macrodilution minimum bactericidal testing requires performance of the test in duplicate, with repeat subculture at 48 hr if the skip phenomenon occurs in both trials at the 24-hr subculture. Killing curves performed on these isolates did not appear to demonstrate any relationship between the skip phenomenon and the paradoxical effect described by Eagle.

John F. Fulton, coccidioidomycosis, and penicillin

When the late Dr. John F. Fulton contracted severe pulmonary coccidioidomycosis in January, 1942, a metastatic lesion posed the threat of further progression and fatal dissemination. The possibility that an untested and generally unavailable antibiotic, penicillin, might be of value in Fulton's illness led his physician, Dr. John Bumstead, to appeal directly to Fulton to obtain this antibiotic, but ostensibly for the benefit of another patient succumbing to hemolytic streptococcal infection. While of no value for Fulton, penicillin was highly successful in the treatment of his other patient and soon of a second one with staphylococcal sepsis and pneumonia. This penicillin, administered in March, 1942, was the first clinical trial of penicillin under the control of the Office of Scientific Research and Development. The unique contribution of Dr. Fulton and of his illness to this event is described.

Prolonged survival of non-multiplying Staphylococcus aureus cells undergoing autolysis in the presence of certain inhibitors of cell wall synthesis

Certain antibiotic compounds including penicillin, cloxacillin and 6-APA caused a prolonged survival of Staph. aureus cells undergoing autolysis in physiologic saline. The retardation of the death rate was dependent upon the type of compound and its concentration. The results suggest that the compounds inhibit the autolytic function of the bacteria.

Antibiotic sensitivities of organisms isolated from mastitic and nonmastitic mammary secretions

Antibiotic sensitivity tests to determine the minimal inhibitory concentrations (MIC) and the minimal lethal concentrations (MLC) for six antibiotics were conducted against mastitic isolates of staphylococci in skim milk and broth. The MIC and the MLC for all the antibiotics except benzylpenicillin were considerably higher in skim milk than in broth. Benzylpenicillin was the most effective antibiotic tested in either medium, and dihydrostreptomycin was the least effective against the organisms tested.

Principles and Practice of Penicillin Therapy in Diseases of the Nervous System

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