Aztreonam in the treatment of gram-negative bacterial meningitis

The Blood-Brain Barrier and Pharmacokinetic/Pharmacodynamic Optimization of Antibiotics for the Treatment of Central Nervous System Infections in Adults

Bacterial central nervous system (CNS) infections are serious and carry significant morbidity and mortality. They encompass many syndromes, the most common being meningitis, which may occur spontaneously or as a consequence of neurosurgical procedures. Many classes of antimicrobials are in clinical use for therapy of CNS infections, some with established roles and indications, others with experimental reporting based on case studies or small series. This review delves into the specifics of the commonly utilized antibacterial agents, updating their therapeutic use in CNS infections from the pharmacokinetic and pharmacodynamic perspectives, with a focus on the optimization of dosing and route of administration that have been described to achieve good clinical outcomes. We also provide a concise synopsis regarding the most focused, clinically relevant information as pertains to each class and subclass of antimicrobial therapeutics. CNS infection morbidity and mortality remain high, and aggressive management is critical in ensuring favorable patient outcomes while averting toxicity and upholding patient safety.

Treatment ofPseudomonas aeruginosainfection in critically ill patients

Critically ill patients are on the increase in the present clinical setting. Aging of our population and increasingly aggressive medical and therapeutic interventions, including implanted foreign bodies, organ transplantation and advances in the chemotherapy of malignant diseases, have created a cohort of particularly vulnerable patients. Pseudomonas aeruginosa is one of the leading gram-negative organisms associated with nosocomial infections. This organism is frequently feared because it causes severe hospital-acquired infections, especially in immunocompromised hosts, and is often antibiotic resistant, complicating the choice of therapy. The epidemiology, microbiology, mechanisms of resistance and currently available and future treatment options for the most relevant infections caused by P. aeruginosa are reviewed.

Management of neonatal sepsis by Gram-negative pathogens

For the pediatrician and neonatologist who care for term and preterm infants, the challenge remains to keep these infants free of infection after delivery in special-care nurseries and neonatal intensive care units. Studies of complications associated with term infants at risk due to maternal factors, as well as preterm infants after early delivery, have demonstrated that sepsis is a major cause of neonatal mortality and morbidity. Infections due to Gram-negative organisms are increasingly being reported from neonatal units. Moreover, Gram-negative organisms that are multidrug resistant are on the increase and pose a formidable clinical challenge. In this article, we review current epidemiology, risk factors, clinical features, diagnosis, therapy and preventive measures related to Gram-negative infections in neonates.

Neonatal bacteremia: patterns of antibiotic resistance

OBJECTIVE

To determine the incidence and evaluate the antimicrobial-susceptibility patterns of bacterial infections in our neonatal units.

DESIGN

Retrospective surveillance study.

SETTING

The neonatal units of the Hadassah University Hospitals, Jerusalem, Israel.

PATIENTS

All newborns admitted from January 1994 through February 1999.

METHODS

The records of all patients with positive blood and cerebrospinal fluid cultures were reviewed. Bacteremia was considered early-onset (vertical) when occurring within the first 72 hours of life and late-onset (nosocomial) when occurring later. The prevalence and antibiotic-resistance patterns of vertically transmitted and nosocomially acquired strains were compared and studied over time.

RESULTS

219 of 35,691 newborn infants had at least one episode of bacteremia (6.13/1,000 live births). There were 305 identified organisms, of which 21% (1.29/1,000 live births) were considered vertically transmitted and 79% nosocomially acquired. The most common organism causing early-onset disease (29.2%) was group B streptococcus (0.38/1,000 live births), whereas coagulase-negative staphylococci (51%) were the most prevalent in late-onset disease. All gram-positive bacteria were susceptible to vancomycin. Most gram-positive organisms other than staphylococci were susceptible to ampicillin. Gram-negative organisms represented 31% of all isolates. Generally, there was a trend of increasing resistance to commonly used antibiotics among nosocomially acquired gram-negative organisms, compared to those vertically transmitted, with statistically significant differences for ampicillin and mezlocillin (P<.05 and P<.01, respectively). Over the years, a trend toward an increasing resistance to antibiotics was observed among gram-negative organisms.

CONCLUSIONS

The trend of increasing bacterial resistance to commonly used antibiotics necessitates the implementation of a rational empirical treatment strategy, based on local susceptibility data, reserving certain agents for emerging resistant pathogens.

Antimicrobial and anti-inflammatory treatment of bacterial meningitis

Mortality and morbidity rates of bacterial meningitis are still unacceptably high, and thus, new, potent antimicrobial agents and adjuvant anti-inflammatory strategies are being evaluated to improve patient outcome. With the declining rates of Haemophilus influenzae type B infections, after the introduction of conjugated vaccines, research to find preventive measures for Streptococcus pneumoniae and Neisseria meningitidis infections is underway. In the meantime, scientific effort is being directed optimally to treat disease caused by multiresistant pneumococcal strains.

Antibiotic use in the emergency department. III. The quinolones, new beta lactams, beta lactam combination agents, and miscellaneous antibiotics

This article reviews several new, relatively broad-spectrum antibiotics that have utility in the emergency department (ED). The quinolones have excellent activity against gram-negative organisms, including gonococcus, and are characterized by very high bioavailability after oral administration. The new beta-lactams aztreonam and imipenem have broad spectra but limited usefulness to the emergency physician, and should be reserved for judicious use in severe infections, particularly those involving Pseudomonas. Clavulanate, sulbactam, and tazobactam are themselves antimicrobials that have been combined with beta-lactams such as ampicillin and ticarcillin to produce agents with significant potential utility in the ED; these are typically not first-line agents, however, and their use should be governed by both clinical and cost concerns. Finally, three older antibiotics--vancomycin, metronidazole, and clindamycin--are reviewed with respect to updated indications for their use in the ED.

Clinical pharmacokinetics of aztreonam. An update

Plasma concentrations of aztreonam follow a 2-compartment open model with a distribution half-life of 0.20 hours after intravenous injection. The volume of distribution at steady-state (Vss) after intravenous and intramuscular injection is about 0.16 L/kg (0.42 L/kg for free drug). After intramuscular injection, absorption is almost complete. Absorption after intraperitoneal administration in patients with peritonitis is 92%. Over a large dosage range, plasma concentrations increase dose proportionally. In healthy individuals, about 56% of the drug is plasma protein bound. Diffusion into tissues is generally slow, and the ratio between mean tissue and plasma aztreonam concentration seems to depend mainly on tissue composition. Aztreonam penetrates into cerebrospinal fluid (CSF) more rapidly in patients with inflamed meninges than in those with noninflamed meninges. Diffusion through the placenta is poor, as is diffusion into breastmilk. Aztreonam is predominantly eliminated by the kidney, partly by active tubular excretion. Extrarenal clearance appears to be through hepatic excretion. Metabolism occurs to a very limited extent. Total plasma clearance (CLp) in healthy adults is about 5.6 L/h and the terminal elimination half-life is 1.7 to 2.0 hours. CLp is similar in both children and adults when expressed as a function of bodyweight. However, in neonates, especially in low birthweight infants, CLp is lower. In various disease states, the Vss of aztreonam is not appreciably different from that found in healthy individuals. However, patients with low serum albumin levels (e.g. burn patients, critically ill patients and those with cirrhosis of the liver) generally have an increased volume of distribution. The elimination half-life of the drug is dependent on renal function.(ABSTRACT TRUNCATED AT 250 WORDS)