Meropenem and imipenem activity against Pseudomonas aeruginosa isolates from the MYSTIC Program

Prevalence of Extended Spectrum β-Lactamase and Antimicrobial Susceptibility Pattern of Clinical Isolates of Pseudomonas from Patients of Khyber Pakhtunkhwa, Pakistan

Majority of gram negative pathogenic bacteria are responsible for extended spectrum β-lactamases (ESBLs) production, which show resistance to some newer generation of antibiotics. The study was aimed at evaluating the prevalence of ESBL and antibiotic susceptibility pattern of Pseudomonas isolates collected during 2010 to 2014 from tertiary care hospitals of Peshawar, Pakistan. Out of 3450 samples, 334 Pseudomonas spp. isolates comprised of 232 indoor and 102 outdoor patients were obtained from different specimens and their susceptibility pattern was determined against 20 antibiotics. Antimicrobial susceptibility testing was carried out using the Kirby-Bauer agar diffusion method and ESBL production was detected by Synergy Disc Diffusion technique. The mean age group of the patients was 29.9 + 9.15 years. Meronem showed best activity (91.02%) from class carbapenem, β-lactam and β-lactamase inhibitors exhibited 69.16% activity, and doxycycline had a diminished activity (10.18%) to Pseudomonas spp. Outdoor isolates were more resistant than the indoor and during the course of the study the sensitivity rate of antibiotics was gradually reducing. ESBL production was observed in 44.32% while the remaining was non-ESBL. The moderate active antibiotics were amikacin (50.7%), SCF (51.4%), TZP (52.7%), and MXF (54.1%) among ESBL producing isolates. Lack of antibiotic policy, irrational uses (3GCs particularly), and the emergence of antibiotic resistant organisms in hospitals may be causes of high antibiotic resistance.

Comparative in vitro activity of Meropenem, Imipenem and Piperacillin/tazobactam against 1071 clinical isolates using 2 different methods: a French multicentre study

BACKGROUND

Meropenem is a carbapenem that has an excellent activity against many gram-positive and gram-negative aerobic, facultative, and anaerobic bacteria. The major objective of the present study was to assess the in vitro activity of meropenem compared to imipenem and piperacillin/tazobactam, against 1071 non-repetitive isolates collected from patients with bacteremia (55%), pneumonia (29%), peritonitis (12%) and wound infections (3%), in 15 French hospitals in 2006. The secondary aim of the study was to compare the results of routinely testings and those obtained by a referent laboratory.

METHOD

Susceptibility testing and Minimum Inhibitory Concentrations (MICs) of meropenem, imipenem and piperacillin/tazobactam were determined locally by Etest method. Susceptibility to meropenem was confirmed at a central laboratory by disc diffusion method and MICs determined by agar dilution method for meropenem, imipenem and piperacillin/tazobactam.

RESULTS

Cumulative susceptibility rates against Escherichia coli were, meropenem and imipenem: 100% and piperacillin/tazobactam: 90%. Against other Enterobacteriaceae, the rates were meropenem: 99%, imipenem: 98% and piperacillin/tazobactam: 90%. All Staphylococci, Streptococci and anaerobes were susceptible to the three antibiotics. Against non fermeters, meropenem was active on 84-94% of the strains, imipenem on 84-98% of the strains and piperacillin/tazobactam on 90-100% of the strains.

CONCLUSIONS

Compared to imipenem, meropenem displays lower MICs against Enterobacteriaceae, Escherichia coli and Pseudomonas aeruginosa. Except for non fermenters, MICs90 of carbapenems were <4 mg/L. Piperacillin/tazobactam was less active against Enterobacteriaceae and Acinetobacter but not P. aeruginosa. Some discrepancies were noted between MICs determined by Etest accross centres and MICs determined by agar dilution method at the central laboratory. Discrepancies were more common for imipenem testing and more frequently related to a few centres. Overall MICs determined by Etest were in general higher (0.5 log to 1 log fold) than MICs by agar dilution.

Management of meningitis due to antibiotic-resistant Acinetobacter species

Acinetobacter meningitis is becoming an increasingly common clinical entity, especially in the postneurosurgical setting, with mortality from this infection exceeding 15%. Infectious Diseases Society of America guidelines for therapy of postneurosurgical meningitis recommend either ceftazidime or cefepime as empirical coverage against Gram-negative pathogens. However, assessment of the pharmacodynamics of these cephalosporins in cerebrospinal fluid suggests that recommended doses will achieve pharmacodynamic targets against fewer than 10% of contemporary acinetobacter isolates. Thus, these antibiotics are poor options for suspected acinetobacter meningitis. From in vitro and pharmacodynamic perspectives, intravenous meropenem plus intraventricular administration of an aminoglycoside may represent a superior, albeit imperfect, regimen for suspected acinetobacter meningitis. For cases of meningitis due to carbapenem-resistant acinetobacter, use of tigecycline is not recommended on pharmacodynamic grounds. The greatest clinical experience rests with use of polymyxins, although an intravenous polymyxin alone is inadvisable. Combination with an intraventricularly administered antibiotic plus removal of infected neurosurgical hardware appears the therapeutic strategy most likely to succeed in this situation. Unfortunately, limited development of new antibiotics plus the growing threat of multidrug-resistant acinetobacter is likely to increase the problems posed by acinetobacter meningitis in the future.

Screening for MRSA: a flawed hospital infection control intervention

Focusing hospital resources on a single antibiotic-resistant pathogen as a sole approach to infection control is inherently flawed. We applied attributable mortality principles to a basic model of bloodstream infections to outline the argument. Screening for methicillin-resistant Staphylococcus aureus alone made sense in the 1980s, but the ongoing emergence of vancomycin-resistant enterococci and antibiotic-resistant strains of gram-negative rods and Candida species, as well as the recognition of the value of team-based infection control programs, support a population-based approach.

MYSTIC Europe 2007: activity of meropenem and other broad-spectrum agents against nosocomial isolates

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program is a longitudinal antimicrobial surveillance study that has been in existence since 1997 in centers that are actively prescribing meropenem. This report examines the results from the study in Europe in 2007. A total of 5208 isolates were examined for activity (MIC) of meropenem and other broad-spectrum antibacterial comparators. Cumulative susceptibility rates using Clinical and Laboratory Standards Institute criteria against all methicillin-susceptible staphylococci were imipenem (97.7%) > meropenem (97.3%) > piperacillin/tazobactam (96.2%) > tobramycin (94.2%) > gentamicin (92.0%) > ciprofloxacin (84.0%) > ceftazidime (39.8%). Against all species of Enterobacteriaceae, the rates were meropenem (99.4%) > imipenem (98.3%) > tobramycin (92.0%) > gentamicin (89.5%) > ceftazidime (86.2%) > piperacillin/tazobactam (85.5%) > ciprofloxacin (84.2%). Meropenem was most effective against the nonfermenters, although multidrug-resistant Acinetobacter spp. and imipenem-resistant Pseudomonas aeruginosa strains were reported. The continued need for surveillance studies such as MYSTIC is exemplified, and results from these types of surveillance can, hopefully, help in the correct choice of empiric therapy.

Clinical review: balancing the therapeutic, safety, and economic issues underlying effective antipseudomonal carbapenem use

Antipseudomonal carbapenems have played a useful role in our antimicrobial armamentarium for 20 years. However, a review of their use during that period creates concern that their clinical effectiveness is critically dependent on attainment of an appropriate dosing range. Unfortunately, adequate carbapenem dosing is missed for many reasons, including benefit/risk misconceptions, a narrow therapeutic window for imipenem and meropenem (due to an increased rate of seizures at higher doses), increasingly resistant pathogens requiring higher doses than are typically given, and cost containment issues that may limit their use. To improve the use of carbapenems, several initiatives should be considered: increase awareness about appropriate treatment with carbapenems across hospital departments; determine optimal dosing regimens for settings where multidrug resistant organisms are more likely encountered; use of, or combination with, an alternative antimicrobial agent having more favorable pharmacokinetic, pharmacodynamic, or adverse event profile; and administer a newer carbapenem with lower propensity for resistance development (for example, reduced expression of efflux pumps or greater stability against carbapenemases).

Current therapies for pseudomonas aeruginosa

Based on the worldwide prevalence of multidrug-resistant strains of Pseudomas aeruginosa and the fact that no newer antipseudomonal agents are available, this article aims to investigate therapeutic solutions for combating infections caused by P aeruginosa, including multidrug-resistant strains. The article focuses mainly on colistin, the re-emerging old antibiotic that possesses prominent antipseudomonal activity in vitro and on doripenem, a newer carbapenem that seems to be close to its global marketing. Regarding older antipseudomonal antibiotics that have been reviewed extensively, only newer aspects on their use are considered in this article.

The current state of multidrug-resistant gram-negative bacilli in North America

Although much of today's media focuses on multidrug-resistant gram-positive bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, resistance within gram-negative bacilli continues to rise, occasionally creating situations in which few or no antibiotics that retain activity are available. Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella sp are emerging threats nationally. Although carbapenems are considered the antibiotic class of choice to treat ESBL-producing Enterobacteriaceae, the ability of these organisms to produce carbapenemases has now become apparent in some regions throughout the United States. Although still rare, Klebsiella sp that produce KPC-2 retain susceptibility only to tigecycline, polymyxins, and occasionally aminoglycosides. Multidrug resistance among Pseudomonas aeruginosa and Acinetobacter sp has always been apparent across many hospitals in the United States. Recent surveillance indicates increasing resistance to all currently available antibiotics, including carbapenems, cephalosporins, penicillins, fluoroquinolones, and aminoglycosides. Against many strains, only polymyxins retain activity; however, resistance has also been reported to these agents. Fortunately, resistance mechanisms such as metallo-beta-lactamases are still rare in the United States. As no new antibiotics with novel mechanisms against many of these gram-negative bacilli are expected to be developed in the foreseeable future, careful and conservative use of agents combined with good infection control practices is required.

Meropenem: a review of its use in the treatment of serious bacterial infections

Meropenem (Merrem, Meronem) is a broad-spectrum antibacterial agent of the carbapenem family, indicated as empirical therapy prior to the identification of causative organisms, or for disease caused by single or multiple susceptible bacteria in both adults and children with a broad range of serious infections. Meropenem is approved for use in complicated intra-abdominal infection (cIAI), complicated skin and skin structure infection (cSSSI) and bacterial meningitis (in paediatric patients aged > or = 3 months) in the US, and in most other countries for nosocomial pneumonia, cIAI, septicaemia, febrile neutropenia, cSSSI, bacterial meningitis, complicated urinary tract infection (UTI), obstetric and gynaecological infections, in cystic fibrosis patients with pulmonary exacerbations, and for the treatment of severe community-acquired pneumonia (CAP). Meropenem has a broad spectrum of in vitro activity against Gram-positive and Gram-negative pathogens, including extended-spectrum beta-lactamase (ESBL)- and AmpC-producing Enterobacteriaceae. It has similar efficacy to comparator antibacterial agents, including: imipenem/cilastatin in cIAI, cSSSI, febrile neutropenia, complicated UTI, obstetric or gynaecological infections and severe CAP; clindamycin plus tobramycin or gentamicin in cIAI or obstetric/gynaecological infections; cefotaxime plus metronidazole in cIAI; cefepime and ceftazidime plus amikacin in septicaemia or febrile neutropenia; and ceftazidime, clarithromycin plus ceftriaxone or amikacin in severe CAP. Meropenem has also shown similar efficacy to cefotaxime in paediatric and adult patients with bacterial meningitis, and to ceftazidime when both agents were administered with or without tobramycin in patients with cystic fibrosis experiencing acute pulmonary exacerbations. Meropenem showed greater efficacy than ceftazidime or piperacillin/tazobactam in febrile neutropenia, and greater efficacy than ceftazidime plus amikacin or tobramycin in patients with nosocomial pneumonia. Meropenem is well tolerated and has the advantage of being suitable for administration as an intravenous bolus or infusion. Its low propensity for inducing seizures means that it is suitable for treating bacterial meningitis and is the only carbapenem approved in this indication. Thus, meropenem continues to be an important option for the empirical treatment of serious bacterial infections in hospitalized patients.