Drug therapy. Beta-lactam antibiotics (2)

Construction of a quaternary stereogenic center by asymmetric hydroformylation: a straightforward method to prepare chiral α-quaternary amino acids

The construction of chiral quaternary carbon stereocenters has been a long-standing challenge in organic chemistry. Particularly, α-quaternary amino acids that are of high importance in biochemistry still lack a straightforward synthetic method. We here reported a hydroformylation approach to access chiral quaternary stereogenic centers, which has been a long-standing challenge in transition metal catalysis. α,β-Unsaturated carboxylic acid derivatives undergo hydroformylation with a rhodium catalyst to generate an α-quaternary stereocenter under mild conditions. By using this method, a variety of chiral α-quaternary amino acids could be synthesized with satisfactory enantioselectivity. In-depth investigation revealed that the regioselectivity is dramatically influenced by the electronic properties of the substituents attached to the target C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bond. By applying NMR and DFT analyses, the chiral environment of a rhodium/Yanphos complex was depicted, based on which a substrate-catalyst interaction model was proposed.

A rhodium-catalyzed asymmetric hydroformylation reaction was reported to construct chiral α-quaternary amino acid derivatives. High chemo-, regio- and enantioselectivity were realized in one step.

Gelatin Methacryloyl Hydrogels for the Localized Delivery of Cefazolin

The tuneability of hydrogels renders them promising candidates for local drug delivery to prevent and treat local surgical site infection (SSI) while avoiding the systemic side-effects of intravenous antibiotic injections. Here, we present a newly developed gelatin methacryloyl (GelMA)-based hydrogel drug delivery system (GelMA-DDS) to locally deliver the broad-spectrum antibiotic cefazolin for SSI prophylaxis and treatment. Antibiotic doses from 3 µg to 90 µg were loaded in photocrosslinked GelMA hydrogel discs with 5 to 15% w/v polymer concentration and drug encapsulation efficiencies, mechanical properties, crosslinking and release kinetics, as well as bacterial growth inhibition were assessed. Our results demonstrate that all GelMA groups supported excellent drug encapsulation efficiencies of up to 99%. Mechanical properties of the GelMA-DDS were highly tuneable and unaffected by the loading of small to medium doses of cefazolin. The diffusive and the proteolytic in vitro drug delivery of all investigated cefazolin doses was characterized by a burst release, and the delivered cefazolin amount was directly proportional to the encapsulated dose. Accelerated enzymatic degradation of the GelMA-DDS followed zero-order kinetics and was dependent on both the cefazolin dose and GelMA concentration (3-13 h). Finally, we demonstrate that cefazolin delivered from GelMA induced a dose-dependent antibacterial efficacy against S. aureus, in both a broth and a diffusive assay. The cefazolin-loaded GelMA-DDS presented here provides a highly tuneable and easy-to-use local delivery system for the prophylaxis and treatment of SSI.

Bicarbonate Resensitization of Methicillin-Resistant Staphylococcus aureus to β-Lactam Antibiotics

Endovascular infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major health care concern, especially infective endocarditis (IE). Standard antimicrobial susceptibility testing (AST) defines most MRSA strains as “resistant” to β-lactams, often leading to the use of costly and/or toxic treatment regimens. In this investigation, five prototype MRSA strains, representing the range of genotypes in current clinical circulation, were studied.

Endovascular infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major health care concern, especially infective endocarditis (IE). Standard antimicrobial susceptibility testing (AST) defines most MRSA strains as “resistant” to β-lactams, often leading to the use of costly and/or toxic treatment regimens. In this investigation, five prototype MRSA strains, representing the range of genotypes in current clinical circulation, were studied. We identified two distinct MRSA phenotypes upon AST using standard media, with or without sodium bicarbonate (NaHCO₃) supplementation: one highly susceptible to the antistaphylococcal β-lactams oxacillin and cefazolin (NaHCO₃ responsive) and one resistant to such agents (NaHCO₃ nonresponsive). These phenotypes accurately predicted clearance profiles of MRSA from target tissues in experimental MRSA IE treated with each β-lactam. Mechanistically, NaHCO₃ reduced the expression of two key genes involved in the MRSA phenotype, mecA and sarA, leading to decreased production of penicillin-binding protein 2a (that mediates methicillin resistance), in NaHCO₃-responsive (but not in NaHCO₃-nonresponsive) strains. Moreover, both cefazolin and oxacillin synergistically killed NaHCO₃-responsive strains in the presence of the host defense antimicrobial peptide (LL-37) in NaHCO₃-supplemented media. These findings suggest that AST of MRSA strains in NaHCO₃-containing media may potentially identify infections caused by NaHCO₃-responsive strains that are appropriate for β-lactam therapy.

Cephalexin-induced acute generalized exanthematous pustulosis

Cephalexin is a cephalosporin antibiotic that is commonly used in the treatment of infectious diseases. We report a patient exhibiting a rare adverse effect of cephalexin: drug-induced Acute Generalized Exanthematous Pustulosis (AGEP). We present this case because of the scarcity of reports associating cephalexin with AGEP in hopes that clinicians will consider AGEP in their differential diagnosis in the appropriate clinical setting.

Mechanical Genomic Studies Reveal the Role of d-Alanine Metabolism in Pseudomonas aeruginosa Cell Stiffness

The mechanical properties of bacteria are important for protecting cells against physical stress. The cell wall is the best-characterized cellular element contributing to bacterial cell mechanics; however, the biochemistry underlying its regulation and assembly is still not completely understood. Using a unique high-throughput biophysical assay, we identified genes coding proteins that modulate cell stiffness in the opportunistic human pathogen Pseudomonas aeruginosa. This approach enabled us to discover proteins with roles in a diverse range of biochemical pathways that influence the stiffness of P. aeruginosa cells. We demonstrate that d-Ala—a component of the peptidoglycan—is tightly regulated in cells and that its accumulation reduces expression of machinery that cross-links this material and decreases cell stiffness. This research demonstrates that there is much to learn about mechanical regulation in bacteria, and these studies revealed new nonessential P. aeruginosa targets that may enhance antibacterial chemotherapies or lead to new approaches.

The stiffness of bacteria prevents cells from bursting due to the large osmotic pressure across the cell wall. Many successful antibiotic chemotherapies target elements that alter mechanical properties of bacteria, and yet a global view of the biochemistry underlying the regulation of bacterial cell stiffness is still emerging. This connection is particularly interesting in opportunistic human pathogens such as Pseudomonas aeruginosa that have a large (80%) proportion of genes of unknown function and low susceptibility to different families of antibiotics, including beta-lactams, aminoglycosides, and quinolones. We used a high-throughput technique to study a library of 5,790 loss-of-function mutants covering ~80% of the nonessential genes and correlated P. aeruginosa individual genes with cell stiffness. We identified 42 genes coding for proteins with diverse functions that, when deleted individually, decreased cell stiffness by >20%. This approach enabled us to construct a “mechanical genome” for P. aeruginosa. d-Alanine dehydrogenase (DadA) is an enzyme that converts d-Ala to pyruvate that was included among the hits; when DadA was deleted, cell stiffness decreased by 18% (using multiple assays to measure mechanics). An increase in the concentration of d-Ala in cells downregulated the expression of genes in peptidoglycan (PG) biosynthesis, including the peptidoglycan-cross-linking transpeptidase genes ponA and dacC. Consistent with this observation, ultraperformance liquid chromatography-mass spectrometry analysis of murein from P. aeruginosa cells revealed that dadA deletion mutants contained PG with reduced cross-linking and altered composition compared to wild-type cells.

Investigation of the Persistence of Penicillin G and Dihydrostreptomycin Residues in Milk of Lactating Buffaloes ( Bubalus bubalis) Using Ultra-High-Performance Liquid Chromatography and Tandem Mass Spectrometry

The purpose of this research was to evaluate the persistence of penicillin G and dihydrostreptomycin in milk of lactating buffaloes following intramuscular injection of procaine penicillin G (200000 IU/mL) and dihydrostreptomycin sulfate (250 mg/mL) every 24 h for 3 days. Milk samples were collected twice daily up to the 13th milking post-treatment and analyzed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry. The analytical method has been validated according to Commission Decision 2002/657/EC. The highest concentrations of penicillin G (275 μg kg^-1) and dihydrostreptomycin (220.5 μg kg^-1) were detected in the milk of the first milkings post-treatment, and levels were below the maximum residue limit of 4 and 200 μg kg^-1 in all treated buffaloes at milkings 12 and 2, respectively. The results of this study demonstrate that a nine-milking withdrawal time set for bovine milk was not adequate for depletion of penicillin G in lactating buffaloes.

Inhibitory effect by new monocyclic 4-alkyliden-beta-lactam compounds on human platelet activation

In the present study some new beta-lactam compounds were screened for their ability to inhibit human platelet activation. In particular four compounds differing in the group on the nitrogen atom of the azetidinone ring were investigated. A beta-lactam having an ethyl 2-carboxyethanoate N-bound group was demonstrated to inhibit, in the micromolar range, both the Ca(2+) release from endoplasmic reticulum, induced either by thrombin or by the ATPase inhibitor thapsigargin, and the Ca(2+) entry in platelets driven by emptying the endoplasmic reticulum. The compound also inhibited the platelet aggregation induced by a variety of physiological agonists including ADP, collagen, thrombin and thrombin mimetic peptide TRAP. The beta-lactam reduced the phosphorylation of pleckstrin (apparent MW 47 kDa), elicited by thrombin but not by the protein kinase C activator phorbol ester. Accordingly it did not significantly affect the aggregation evoked by phorbol ester or Ca(2+) ionophore. It was concluded that the beta-lactam likely exerts its anti-platelet-activating action by hampering the agonist induced cellular Ca(2+) movements. The beta-lactam concentration, which significantly inhibited platelet activation, only negligibly affected the cellular viability. Even if it is still premature to draw definitive conclusions, the present results suggest that this new compound might constitute a tool of potential clinical interest and the starting-point for the synthesis of new more beneficial anti-thrombotic compounds.

Geriatric pharmacology

With the dramatic demographic change that has resulted in the "graying of the population" has come a compelling interest in the health and health concerns of older adults. The increasing incidence and prevalence of systemic diseases, especially chronic diseases, among older adults, and the concomitant increase in medication use, have provided impetus for the subspecialty of geriatric pharmacology. This article reviews the physiologic changes, nonphysiologic aspects, and pharmacologic changes associated with aging and their implications for dental practice.

Systemic antibiotic agents

Understanding the breadth of systemic antimicrobial agents available for use by the dermatologist and their associated side-effect profiles and drug interactions allows the clinician to offer patients optimal care in the management of cutaneous infectious disease.

Antimicrobial therapy in the elderly

This article focuses on the special characteristics of infection in the elderly and provides an update of the principles of antibiotic selection, use of specific antibiotics, and empiric use of antimicrobials in the treatment of infectious diseases in this particularly vulnerable group. Antituberculous, antifungal, and antiviral agents are mentioned briefly; detailed information regarding these classes of agents in reference to aging can be found in standard reviews of antimicrobial therapy in the elderly.

Five-year survey of cefotaxime resistance in Spain

During 1991-1995 a Spain collaborative study group surveyed the resistance to cefotaxime both in community as well as in hospital isolates of bacteria. The isolates tested during the study period of 5 years were 813, 875, 3631, 3184, and 3050 strains, respectively. Antimicrobial activity of cefotaxime was assayed by broth or agar microdilution, in accordance with criteria of the National Committee of Clinical Laboratory Standards (NCCLS). Cefotaxime resistance included 2.5% of all isolates: 2.6% Enterobacteriaceae, 1.7% Streptococcus pneumoniae, 0.5% Haemophilus influenzae, 0.0% Haemophilus spp., and 0.0% Moraxella catarrhalis. The overall incidence of resistance to cefotaxime decreased fro member of Enterobacteriaceae from 3.6% in 1991 to 2.5% in 1995. The incidence of resistance varied with the species and was highest in Enterobacter and in Citrobacter freundii.

Serology of antibodies to second- and third-generation cephalosporins associated with immune hemolytic anemia and/or positive direct antiglobulin tests

BACKGROUND

First-generation cephalosporins rarely caused immune hemolytic anemia (IHA). Second- and third-generation cephalosporins, especially cefotetan and ceftriaxone, are increasingly associated with severe, sometimes fatal IHA.

STUDY DESIGN AND METHODS

Samples from 53 patients with drug-induced IHA and/or positive direct antiglobulin test (DAT) were tested. Patients' sera were tested against drug-treated red cells (RBCs) and untreated or enzyme-treated RBCs, with and without the addition of drug solution. Eluates from patients' RBCs were tested against drug-treated and untreated RBCs.

RESULTS

Forty-three patients had antibodies to cefotetan, 8 to ceftriaxone, 1 to cefoxitin, and 1 to cefotaxime. All patients had a positive DAT; only anticefoxitin and anti-cefotetan were demonstrable in RBC eluates. Sera containing anti-cefoxitin, anti-cefotaxime, and anti-cefotetan reacted with drug-treated RBCs (100%) and untreated or enzyme-treated RBCs in the presence of drug (98% or 100%, respectively). All of the ceftriaxone antibodies reacted with untreated or enzyme-treated RBCs in the presence of drug, but those tested did not react with ceftriaxone-treated RBCs. In addition to cefotetan-dependent antibodies, 19 (44%) and 14 (33%) of 43 sera contained drug-independent antibodies when tested with and without the presence of a polyethylene glycol potentiator, respectively.

CONCLUSION

Cefotetan is by far the most common cause of drug-induced IHA. All cefotetan antibodies and the single examples of cefoxitin and cefotaxime antibodies reacted with drug-coated RBCs, and most, in contrast to the reactions of antibodies to first-generation cephalosporins (e.g., cephalothin), also reacted with RBCs (not treated with drug) in the presence of the drug. Ceftriaxone antibodies reacted only by the latter mechanism. Drug-independent antibodies (i.e., those reacting without any drug being present) were detected in 33 to 44 percent of patients' sera containing cefotetan antibodies, depending on the sensitivity of the method used.

Antimicrobial agents for the dermatologist. I. Beta-lactam antibiotics and related compounds

We review the newer antimicrobial agents that are being employed by dermatologists with increased frequency as well as some of the more commonly used older agents. Particular emphasis is based on selection factors such as causative pathogens and their resistance profiles, routes of administration, toxicity, drug interactions, and dosing requirements. Emphasis in this review is on the newer classes of antimicrobials such as third- and fourth-generation cephalosporins; beta-lactam, beta-lactamase inhibitor combination agents; monobactams; carbapenems; macrolides; and fluoroquinolones. Dermatologic indications and treatment alternatives are highlighted; this will expand the practicing clinician's therapeutic armamentarium and enable him/her to make rational decisions concerning treatment approaches to infectious disease problems encountered in daily practice.

Antibiotic selection in obstetric patients

Penicillin and ampicillin are valuable antibiotics in obstetrics because of their excellent activity against group A and group B streptococci. In addition, ampicillin is the treatment of choice for enterococcal infections, particularly urinary tract infections. Limited spectrum cephalosporins are of primary value as prophylactic agents. Ceftriaxone, an intermediate spectrum agent, is an excellent drug for treatment of infections caused by N. gonorrhoeae. Extended spectrum cephalosporins, penicillins, and carbapenems provide sufficient coverage against pathogenic organisms to be used as single agents for treatment of polymicrobial infections such as chorioamnionitis and puerperal endometritis. Alternatively, combination regimens such as clindamycin or metronidazole plus an aminoglycoside or aztreonam are also highly effective in this clinical situation. Erythromycin and azithromycin have value primarily for treatment of endocervical chlamydial infections and mycoplasma pneumonia in obstetric patients and for intrapartum prophylaxis against group B streptococcal infection in patients who are allergic to beta-lactam antibiotics.

Meropenem monotherapy versus cefotaxime plus metronidazole combination treatment for serious intra-abdominal infections

In an open, randomised, multicentre trial, the efficacy and tolerability of empirical meropenem monotherapy (1 g intravenously every 8 hours) and cefotaxime (2 g every 8 hours) plus metronidazole (0.5 g intravenously every 8 hours) for 5 to 10 days was compared in 94 patients with serious intra-abdominal infection who required surgery. Eighty-three patients had an evaluable clinical response. Significantly more patients in the meropenem group had a satisfactory clinical response at the end of treatment (41/43 [95.3%] vs 30/40 [75.0%]; p = 0.008). The bacteriological response was also higher in the meropenem group (31/33 vs 26/32). In the bacteriologically evaluable population, a satisfactory clinical response was observed in 31/33 of those who received meropenem compared to 24/32 of the cefotaxime/metronidazole recipients (p = 0.03). Empirical meropenem monotherapy should prove a useful alternative to the currently standard combination treatment for serious intraabdominal infections.

Pharmacokinetics of ceftriaxone in healthy horses

Five healthy Equidae (4 horses and one pony) were given a single i.v. dose of ceftriaxone (50 mg/kg bwt) to determine the pharmacokinetics and concentration in cerebrospinal fluid (CSF). Blood was drawn from an i.v. jugular catheter and CSF from a pre-placed, intrathecal catheter. Serum and CSF concentrations were determined by high performance liquid chromatography. The mean serum concentration of ceftriaxone was 144.7 micrograms/ml 15 min after injection and declined to 0.3 microgram/ml 10 h after injection. The elimination rate constant (lambda 2) was 0.63 +/- s.e. 0.23/h, the elimination half-life (t 1/2) was 1.62 +/- s.e. 0.42 h and the apparent volume of distribution at steady state (Vd(ss)) was 330.8 +/- 11.8 ml/kg bwt. Clearance was 312.7 +/- 38 ml/h/kg bwt and mean residence time was 1.13 +/- 0.14 h. Mean CSF concentration was 0.60 +/- 0.14 microgram/ml at 3 h after injection and 0.4 +/- 0.31 microgram/ml at 8 h. Ceftriaxone may be useful in the treatment of bacterial infections in horses. Its ability to penetrate the CSF should make it effective in the treatment of bacterial meningitis.

Cefotaxime. Unchanged antibacterial activity over years?

During recent years new mechanisms of beta-lactam resistance have developed with the genetic origin on the chromosome or plasmids. Nevertheless, most multicenter studies can demonstrate that cefotaxime has retained its antibacterial activity toward the relevant species. However, it is important to follow the development of resistance closely in hospitals, where epidemic outbreaks of bacterial strains with extended-spectrum beta-lactamases can create difficulties in the treatment of infectious diseases.

Bilateral massive adrenal hemorrhage

A systematic review of the etiopathogenesis of adrenal hemorrhage reveals that the factors that determine the occurrence of this complication in a patient can be identified prospectively. Such prospective diagnostic suspicion allows the significance of the otherwise nonspecific clinical features heralding this catastrophe to be appreciated in the precrisis interval. Confirmation of the diagnosis is achieved by visual demonstration of bilaterally enlarged and hyperdense adrenal glands on a CT scan and by demonstration of adrenocortical failure on hormonal evaluation. Preemptive steroid therapy and diagnostic evaluation during the precrisis period prevent the occurrence of a potentially disastrous adrenal crisis in a patient who is seriously ill from other problems and who cannot afford a setback of this severity. Because steroid therapy delayed until the stage of crisis may be unsuccessful in salvaging such a patient, prospective recognition must be based on identifying the patient at risk for BMAH and recognizing the significance of the nonspecific clinical features that accompany it in the appropriate clinical context.

Serum sickness-like reactions associated with cefprozil therapy

Four patients had serum sickness-like reactions during treatment with cefprozil, a new cephalosporin. Two patients had had previous mild reactions associated with cephalosporin therapy. It remains uncertain whether cefprozil-associated serum sickness-like reaction represents a unique or a class-related adverse drug reaction.

Transport of beta-lactam antibiotics in kidney brush border membrane. Determinants of their affinity for the oligopeptide/H+ symporter

This study was designed to determine whether beta-lactam antibiotics (cephalosporins and penicillins) are all substrates for the renal oligopeptide/H+ symporter and, if so, whether the transport system discriminates among the numerous beta-lactam antibiotics. We used [3H]glycylglutamine, [3H]cephalexin, and [3H]-ampicillin as probes for the transport of oligopeptides, cephalosporins, and penicillins in kidney brush border membrane vesicles, respectively. Among the beta-lactam antibiotics, only those with an alpha-amino group in the phenylacetamido moiety were found to interact with the oligopeptide/H+ symporter. Aminocephalosporins displayed high affinities (KiS generally < 250 microM), whereas aminopenicillins displayed low affinities (Ki 0.78-3.03 mM). These differences in affinities appeared to be a consequence of conformational features of the substrates, especially the sterical location of the carboxy group. The affinities of aminolactams for the oligopeptide/H+ symporter were, furthermore, related to the hydrophobicity of the phenylglycyl chains and the substituents attached to the thiazolidine and dihydrothiazine ring. In sharp contrast to the uptake of [3H]glycylglutamine and [3H]cephalexin, the uptake of [3H]ampicillin was not dependent on a pH gradient and was inhibited by various beta-lactam antibiotics, whether or not they contained an alpha-amino group. Our data suggest that: (a) the transport of aminocephalosporins is largely mediated by the oligopeptide/H+ symporter, which is highly influenced by the substrate structure; and (b) penicillins are transported by another system, which is less discriminative with respect to substrate structure.

Multilaboratory evaluation of the in vitro activity of 13 beta-lactam antibiotics against 1474 clinical isolates of aerobic and anaerobic bacteria

The in vitro activity of 13 beta-lactam antibiotics against 1474 recent clinical isolates was evaluated in a multilaboratory study. The most active antibiotic tested in this study was imipenem (98.5% of the strains were susceptible), followed by ticarcillin-clavulanate (91.4%), cefoperazone (90.0%), ceftazidime (87.9%), cefotaxime (87.7%), ceftriaxone (87.0%), ceftizoxime (86.3%), cefotetan (78.5%), ampicillin-sulbactam (77.9%), cefoxitin (73.5%), cefuroxime (70.9%), cefonicid (64.5%), and cefazolin (57.9%).

Prospective evaluation of effects of broad-spectrum antibiotics on gastrointestinal yeast colonization of humans

This study evaluated the effects of broad-spectrum antibiotics on the gastrointestinal (G.I.) yeast flora of humans and correlated the findings with those obtained from a mouse model of G.I. colonization by Candida albicans. We prospectively studied 46 adult cancer patients who received one of five broad-spectrum antibiotics (ceftriaxone, ceftazidime, ticarcillin-clavulanic acid, imipenem-cilastatin, and aztreonam) as therapy for infections. Quantitative examination of yeast colonization of stools was conducted at the baseline, at the end of antibiotic treatment, and 1 week after discontinuation of therapy. Antibiotics with anaerobic activity (ticarcillin-clavulanic acid) or high G.I. concentrations (ceftriaxone) caused a higher and more sustained increase in G.I. colonization by yeasts than did antibiotics with poor anaerobic activity (ceftazidime and aztreonam) or a low G.I. concentration (imipenem-cilastatin). These results were similar to those obtained with a mouse model of G.I. colonization by C. albicans that involved the same antibiotics. Hence, the mouse model may be useful for evaluation of yeast colonization of the human G.I. tract.

Postoperative primary adrenal failure from bilateral hemorrhagic adrenal infarction associated with coagulation factor XI deficiency

A 72-year-old man developed bilateral adrenal hemorrhage causing primary adrenal failure three days after total hip replacement, and was found to have coagulation factor XI deficiency. Factor XI deficiency usually causes mild bleeding which is not predictable on the basis of assayable factor XI levels. There have been no previous reports of bilateral adrenal hemorrhage in factor XI deficiency or other inherited coagulation factor deficiencies. We suggest that the risk of bilateral adrenal hemorrhage should be considered in any preoperative evaluation of patients with factor XI deficiency.

Sorting out the cephalosporins

How can you choose the best cephalosporin to prescribe out of an array that is vast and quickly growing? Dr Brogan simplifies the process by describing the specific advantages as well as the shortcomings of individual agents. He also makes general recommendations based on his experience.

Systemic antibiotic treatment of nosocomial pneumonia

Nosocomial pneumonia continues to represent a significant cause of morbidity and mortality in hospitalized patients. Bacteria are responsible for greater than 90% of the pneumonias, the most common isolates being aerobic Gram-negative bacilli and S. aureus. Cornerstones of treatment are intravenous antibiotics and supportive care. In the individual case the true etiology is usually unknown; therefore empiric broad spectrum treatment is commonly used based on the prevalence of local pathogens, their antibiotic sensitivity pattern and on host factors. Combination antibiotic regimens, including beta-lactams and aminoglycosides, are considered as standard therapy and are associated with clinical success rates of greater than 80%. Monotherapy with broad spectrum antibiotics, such as third generation cephalosporins, imipenem and fluoroquinolones, can be considered as equally effective in non-neutropenic patients and in the absence of P. aeruginosa infection. More active and less toxic antibiotics are still needed for problematic pathogens such as methicillin-resistant S. aureus strains, multiresistant Enterobacteriaceae and Pseudomonas species. Because further improvement in morbidity and mortality may be limited with antibiotics alone, new emphasis should be placed on prevention of infection and the use of immunotherapy.

Antibiotic choices in surgical intensive care unit patients

Antibiotics have dramatically changed the care of the critically ill patient over the last 60 years. Patients with complex physiological conditions present with infectious processes requiring the effective use of antimicrobial drugs. In many situations, the inability to eradicate the infectious process is complicated by the progressive development of resistance among the causative organisms. Systemic antibiotic prophylaxis is warranted only for the prevention of wound infections. Regimens in these cases should use large doses of nontoxic antibiotics covering the spectrum of organisms likely to contaminate the wound. The duration of wound prophylaxis should be short, essentially covering only the period of active wound closure; this is usually less than 24 hours. Prevention of most other infections in the ICU depends on the recognition and correction of the various disturbances of host defenses. Topical antibiotic therapy may reduce the level of colonization for a few specific types of infection. Initial empiric antibiotic therapy should be started for clear indications. The antibiotics chosen should be those most likely to be effective against the probable organisms, those which have the lowest toxicity, and those with the smallest likelihood of inducing multiresistance. They must be adjusted promptly based on the microbiologic sensitivities observed. The realization that the physiology of critical illness may alter the normal relations between drug dosages and the tissue antibiotic levels obtained mandates a different approach to the treatment of these patients. The drug volumes of distribution are generally markedly expanded in these patients. Furthermore, these patients require high tissue antibiotic concentrations to improve the chances for successful therapy. Thus, the antibiotics selected must be capable of providing these levels without significant toxicity to the host. Therapy should be continued based on the clinical response observed. Premature cessation of effective therapy often results in relapse.

Cephalosporins--cefotaxime 10 years later, a major drug with continued use

Cefotaxime has in the past decade proved to be a most useful agent. It has established the efficacy and safety suggested in the early in vitro, pharmacological and clinical papers. It remains an excellent agent to treat many community and hospital-acquired respiratory infections, urinary tract infections, meningitis, particularly in pediatrics, spontaneous bacterial peritonitis and selected abdominal and gynecological infections.

Influence of growth media on Escherichia coli cell composition and ceftazidime susceptibility

Cell composition and surface properties of Escherichia coli were modified by using various growth media to investigate the role of yet uncharacterized components in ceftazidime susceptibility. An eightfold dilution of Luria broth was used as the basic growth medium and was supplemented with up to 4% phosphate, 5% glucose, or 12% L-glutamate. Decreases in cephaloridine and ceftazidime susceptibility, of two- and eightfold, respectively, were observed only in the glucose-enriched medium. The outer membrane permeability to ceftazidime and cephaloridine was evaluated by crypticity indices. Indices were unchanged under all growth conditions. Fluorometry of whole cells with 1-N-phenylnaphthylamine showed that glucose does not affect the interaction of this hydrophobic probe with the membranes but showed that elevated concentrations of phosphate or glutamate cause a marked increase in cell hydrophobicity, which, in turn, correlates with an increase in the susceptibility of E. coli to nalidixic acid. Growth in phosphate- or glutamate-enriched media caused an augmentation in major phospholipid species and may explain the increased hydrophobicity and susceptibility of E. coli to nalidixic acid. These data showed that E. coli susceptibility to ceftazidime is not influenced by cell surface hydrophobicity and suggested that the contribution of a nonspecific lipophilic diffusion route for entry of ceftazidime into cells is not likely to occur or is distinct from that of more hydrophobic molecules such as nalidixic acid. Finally, the penicillin-binding proteins of the E. coli cells were also investigated. Penicillin-binding protein 8 was only markedly labeled with 125I-penicillin V in inner membranes extracted from cells grown with glucose. Results of this study suggest that the unexpected change in penicillin-binding protein 8 observed in the presence of glucose may be responsible for the increase in MICs of cephaloridine and ceftazidime.

In vitro activity and beta-lactamase stability of GR69153, a new long-acting cephalosporin

GR69153, a new parenteral cephalosporin, inhibited 90% of Escherichia coli, Klebsiella oxytoca, Proteus mirabilis, Citrobacter diversus, shigellae, and salmonellae at less than 0.25 micrograms/ml (MIC90). It had activity comparable to those of ceftazidime, cefpirome, cefepime, and E-1040. Against cephalosporinase-producing Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens, MICs ranged from 0.12 to greater than 32 micrograms/ml, and cefpirome and cefepime were the most active agents against these species. Pseudomonas aeruginosa was highly susceptible to GR69153, and for this organism the MIC90 was less than or equal to 2 micrograms/ml, which was similar to the E-1040 MIC90, but most Pseudomonas cepacia and Xanthomonas maltophilia isolates were resistant. GR69153 inhibited Haemophilus influenzae and Moraxella branhamella at less than or equal to 0.5 micrograms/ml. For Staphylococcus aureus GR69153 MICs were similar to those of ceftazidime and E-1040. Enterococci and listeriae were resistant to GR69153, but Streptococcus pyogenes and Streptococcus pneumoniae were inhibited by 0.5 micrograms/ml. The activity of GR69153 was not affected by serum. GR69153 was not inactivated by the beta-lactamases of Staphylococcus aureus, TEM-1, TEM-2, SHV-1, and BRO-1, but it was hydrolyzed by TEM-3, TEM-9, and morganellae. GR69153 had overall activity comparable to those of commercially available parenteral cephalosporins or those found in clinical investigations. It is more active against bacteroides than most available aminothiazolyl parenteral cephalosporins are. GR69153 is hydrolyzed by the new plasmid beta-lactamases, and thus, its primary value may be related to its pharmacological properties.

Comparative antimicrobial activity of ceftibuten against multiply-resistant microorganisms from Belgium

To study the activity of ceftibuten, we obtained multiply-resistant isolates from approximately 20 hospitals in Belgium. Against Enterobacteriaceae, all of the tested comparative compounds were more active than cefaclor, and ceftibuten and tigemonam were the most active of the agents tested. Ceftibuten MIC50s were less than or equal to 1 microgram/ml for most enteric bacilli species and 85% of strains were susceptible (less than or equal to 8 micrograms/ml). This level of activity compared favorably to that recorded for cefaclor (less than or equal to 8 micrograms/ml), cefetamet (less than or equal to 4 micrograms/ml), and cefteram (less than or equal to 1 microgram/ml), that is, 37%, 69%, and 59%, respectively. Ceftibuten, cefetamet, cefteram, and tigemonam were highly active against isolates of Haemophilus influenzae and Neisseria gonorrhoeae. None of the comparative agents were as active as cefaclor against staphylococcal isolates. Against streptococci, cefteram was the most active, and tigemonam the least active of the agents. The MIC90s of ceftibuten for strains of Streptococcus pneumoniae and Streptococcus pyogenes were 2 micrograms/ml and 0.5 microgram/ml, respectively. Strains of Streptococcus agalactiae were resistant to both ceftibuten and tigemonam; cefaclor and cefteram inhibited 100% of isolates of this species. Strains of Enterococcus faecalis and Pseudomonas aeruginosa were consistently resistant to all of the compounds. Overall, ceftibuten exhibited potent activity against many multiply-resistant clinical isolates.

Effects of broad-spectrum antimicrobial agents on yeast colonization of the gastrointestinal tracts of mice

Male Crl:CD1 (ICR) BR mice, 3 months old, were fed regular chow or chow containing Candida albicans. Subsequently, both groups were treated with either antibiotics or normal saline for 10 days. Stool cultures were obtained to determine the extent of C. albicans colonization immediately before treatment, at the end of treatment, and 1 week after the discontinuation of treatment. Animals in the antibiotic-treated groups had substantially higher Candida counts than control animals fed C. albicans, especially if they received ceftriaxone, cefoperazone, or ticarcillin-clavulanic acid. There was no evidence of Candida dissemination to internal organs.

Pathophysiologic basis for the use of third-generation cephalosporins

After 10 years of use, the third-generation cephalosporins remain excellent antibiotics. They have superior activity against selected streptococcal species compared with other cephalosporins, and superior activity against Haemophilus, Neisseria, Branhamella, and other less common oral gram-negative aerobic species. Despite a very broad spectrum of activity, the third-generation cephalosporins, like all other cephalosporins, have only poor activity against enterococci, Listeria, Corynebacterium jekeium, and methicillin-resistant staphylococci. Over the past 10 years, the activity of the third-generation cephalosporins against Escherichia coli, Klebsiella, Proteus, Providencia, Serratia, Haemophilus, and Neisseria has remained excellent. Equally as important, though perhaps less well recognized, is the activity of some of these agents against mouth anaerobic species and the anaerobic Bacteroides and Clostridium spp. of the pelvic area. At present, there are two main threats to the continued use of the third-generation cephalosporins. These are the increasing number of infections due to Enterobacter spp., which constitutively produce large amounts of a beta-lactamase that hydrolyzes cephalosporins, and the recent appearance of Klebsiella spp. in many parts of the world that possess new plasmid-mediated beta-lactamases that destroy cefotaxime, ceftazidime, and related third-generation parenteral cephalosporins. Correlation of pharmacologic properties with in vitro activity provides information as to reasonable dosage regimens for the third-generation cephalosporins. For most serious infections cefotaxime, ceftizoxime, and ceftazidime should be given three times a day provided that the patient has relatively normal renal function. Ceftriaxone can be administered once daily in less severe infections. The use of lower doses or less frequent dosing with cefotaxime, ceftizoxime, or ceftazidime is recommended in aged patients whose renal function is impaired. The unique interaction of cefotaxime with its active metabolite, desacetylcefotaxime, allows cefotaxime to be administered less frequently than three times a day in selected anaerobic infections. Correlation of the antibacterial activity and pharmacology of cephalosporins will help us to tailor their use more appropriately, so that the third-generation cephalosporins will remain useful antimicrobial agents for a further decade.

Optimum therapy for acute pelvic inflammatory disease

Neisseria gonorrhoeae is responsible for about one-third to one-half of cases of acute pelvic inflammatory disease (PID), although there is considerable geographical variation. Chlamydia trachomatis is also an important aetiological agent, and is currently isolated 4 times more commonly from the cervix than the gonococcus. However, it is now clear that acute PID is polymicrobial in aetiology. Even when N. gonorrhoeae and/or C. trachomatis are isolated from the endocervix, anaerobes such as Bacteroides fragilis, Peptococcus and Peptostreptococcus and aerobes, especially the Enterobacteriaceae such as E. coli, are also frequently isolated. Bacterial synergism, coinfection with the gonococcus and C. trachomatis and the involvement of multiple other micro-organisms including aerobes and anaerobes and antibiotic resistance make the selection of an optimal antibiotic regimen difficult. The Centers for Disease Control (CDC) recommendations first proposed in 1982 and revised in 1985 emphasise broad spectrum antimicrobial therapy including coverage of C. trachomatis. In September 1989, the CDC revised its recommendation for the treatment of acute PID. Current recommendations include the use of newer third generation cephalosporins such as ceftriaxone, ceftizoxime and cefotaxime which give excellent coverage of the gonococcus and the Enterobacteriaceae. It is still important to include doxycycline or a tetracycline to cover C. trachomatis. For patients with advanced disease or a tubo-ovarian abscess, clindamycin plus gentamicin has been the regimen of choice. Aztreonam, a new monobactam, has several advantages over gentamicin including less toxicity, more dependable blood levels and good coverage of N. gonorrhoeae and the Enterobacteriaceae.

Selective decontamination to reduce gram-negative colonisation and infections after oesophageal resection

181 patients undergoing resection of the oesophagus for carcinoma were randomised to receive selective decontamination (test group) or conventional perioperative antibiotic prophylaxis (controls). 114 patients were finally included in the study: 12 of 56 test patients had 18 infections, whereas 32 of 58 controls acquired 51 infections. Colonisation with aerobic gram-negative microorganisms, and the number of postoperative respiratory tract infections were significantly lower in the test patients. The postoperative therapeutic use of antibiotics was significantly lower in the test group. No endogenous infections were caused by gram-negative bacilli in the test group. Selective decontamination reduces colonisation with gram-negative bacilli and postoperative infections after resection of the oesophagus.