In vitro activity of three carbapenem antibiotics. Comparative studies with biapenem (L-627), imipenem, and meropenem against aerobic pathogens isolated worldwide

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

Worldwide distribution and environmental origin of the Adelaide imipenemase (AIM-1), a potent carbapenemase in Pseudomonas aeruginosa

Carbapenems are potent broad-spectrum β-lactam antibiotics reserved for the treatment of serious infections caused by multidrug-resistant bacteria such as Pseudomonas aeruginosa. The surge in P. aeruginosa resistant to carbapenems is an urgent threat, as very few treatment options remain. Resistance to carbapenems is predominantly due to the presence of carbapenemase enzymes. The assessment of 147 P. aeruginosa isolates revealed that 32 isolates were carbapenem non-wild-type. These isolates were screened for carbapenem resistance genes using PCR. One isolate from wastewater contained the Adelaide imipenemase gene (bla _AIM-1) and was compared phenotypically with a highly carbapenem-resistant clinical isolate containing the bla _AIM-1 gene. A further investigation of wastewater samples from various local healthcare and non-healthcare sources as well as river water, using probe-based qPCR, revealed the presence of the bla _AIM-1 gene in all the samples analysed. The widespread occurrence of bla _AIM-1 throughout Adelaide hinted at the possibility of more generally extensive spread of this gene than originally thought. A blast search revealed the presence of the bla _AIM-1 gene in Asia, North America and Europe. To elucidate the identity of the organism(s) carrying the bla _AIM-1 gene, shotgun metagenomic sequencing was conducted on three wastewater samples from different locations. Comparison of these nucleotide sequences with a whole-genome sequence of a P. aeruginosa isolate revealed that, unlike the genetic environment and arrangement in P. aeruginosa, the bla _AIM-1 gene was not carried as part of any mobile genetic elements. A phylogenetic tree constructed with the deduced amino acid sequences of AIM-1 suggested that the potential origin of the bla _AIM-1 gene in P. aeruginosa might be the non-pathogenic environmental organism, Pseudoxanthomonas mexicana.

Mechanisms for Rapid Evolution of Carbapenem Resistance in a Clinical Isolate of Pseudomonas aeruginosa

Infections by Pseudomonas aeruginosa are difficult to cure due to its high intrinsic and acquired antibiotic resistance. Once colonized the human host, and thanks to antibiotic treatment pressure, P. aeruginosa usually acquires genetic mutations which provide bacteria with antibiotic resistance as well as ability to better adapt to the host environment. Deciphering the evolutionary traits may provide important insights into the development of effective combinatory antibiotic therapy to treat P. aeruginosa infections. In this study, we investigated the molecular mechanisms by which a clinical isolate (ISP50) yields a carbapenem-resistant derivative (IRP41). RNAseq and genomic DNA reference mapping were conducted to compare the transcriptional profiles and in vivo evolutionary trajectories between the two isolates. Our results demonstrated that oprD mutation together with ampC hyper-expression contributed to the increased resistance to carbapenem in the isolate IRP41. Furthermore, a ldcA (PA5198) gene, encoding murein tetrapeptide carboxypeptidase, has been demonstrated for the first time to negatively influence the ampC expression in P. aeruginosa.

Evaluating biapenem dosage regimens in intensive care unit patients with Pseudomonas aeruginosa infections: a pharmacokinetic/pharmacodynamic analysis using Monte Carlo simulation

This study was conducted to identify optimal dosage regimens and estimate pharmacokinetic/pharmacodynamic (PK/PD) characteristics of short-infusion (SI) versus extended-infusion (EI) biapenem against Pseudomonas aeruginosa infections in Chinese intensive care unit (ICU) patients. A total of 85 strains of P. aeruginosa were collected, and the minimum inhibitory concentration (MIC) of biapenem was measured by the serial two-fold agar dilution method. We designed four frequently used clinical regimens: biapenem 300 mg I.V. q12h, q8h, and q6h, and 600 mg q12h. The Monte Carlo Simulation (MCS) was performed using previously published pharmacokinetic data to calculate the probability of target attainment (PTA) and the cumulative fraction of response (CFR) of these regimens as an SI (0.5 h) and an EI (1 h, 2 h, 3 h, and 4 h). For a target of 40%fT_>MIC (serum drug concentration remains above the MIC for a dosing period), none of the regimens achieved any CFRs>90% for P. aeruginosa, multidrug-resistant P. aeruginosa (MDR-PA) and even non-MDR-PA. The traditional biapenem SI regimens most commonly seen in clinical practice were insufficient in treating both MDR and non-MDR P. aeruginosa in ICU patients. However, biapenem 600 mg q12h over 2-4 h EI regimens could achieve CFR>90% with 20%fT_>MIC. Clinical trials should aim to validate the potentially greater PK/PD index with higher, more frequent doses and longer extended infusions.

In Vitro activities of combinations of rifampin with other antimicrobials against multidrug-resistant Acinetobacter baumannii

The antimicrobial treatment of multidrug-resistant (MDR) Acinetobacter baumannii infections has become a great challenge for medical staff all over the world. Increasing numbers of MDR A. baumannii infections have been identified and reported, but effective clinical treatments for them are decreasing. The objective of this study was to investigate the in vitro activities of combinations of rifampin (an established antimicrobial) and other antimicrobials, including biapenem, colistin, and tigecycline, against 73 clinical isolates of MDR A. baumannii. In total, 73 clinical isolates of MDR A. baumannii were collected from two A-level general hospitals in Beijing, and the MICs of rifampin, biapenem, colistin, and tigecycline were determined. The checkerboard method was used to determine the fractional inhibitory concentration indices (FICIs), that is, whether the combinations acted synergistically against these isolates. The MIC50, MIC90, and MICrange of rifampin combined with biapenem, colistin, and tigecycline against the isolates were clearly lower than those for four antimicrobials (rifampin, biapenem, colistin, and tigecycline) that were used alone. Combinations of rifampin with biapenem, colistin, and tigecycline individually demonstrated the following interactions: synergistic interactions (FICI ≤ 0.5) for 31.51%, 34.25%, and 31.51% of the isolates, partially synergistic interactions (0.5 < FICI < 1) for 49.31%, 43.83%, and 47.94% of the isolates, and additive interactions (FICI = 1) for 19.18%, 21.92%, and 20.55% of the isolates, respectively. There were no indifferent (1 < FICI < 4) or antagonistic (FICI ≥ 4) interactions. Therefore, combinations of rifampin with biapenem, colistin, or tigecycline may be future therapeutic alternatives for the treatment of MDR A. baumannii infections.

Imipenem and meropenem: Comparison of in vitro activity, pharmacokinetics, clinical trials and adverse effects

OBJECTIVE

To compare and contrast imipenem and meropenem in terms of in vitro activity, pharmacokinetics, clinical efficacy and adverse effects.

DATA SELECTION

MEDLINE search from 1975 to 1997 and follow-up of references.

DATA EXTRACTION

Clinical trials comparing imipenem with meropenem, or either imipenem or meropenem with standard therapy in the treatment of serious infections were selected.

DATA SYNTHESIS

Imipenem, the first carbapenem, was first marketed in 1987; meropenem was introduced to the market in 1996. In general, imipenem is more active against Gram-positive cocci while meropenem is more active against Gram-negative bacilli. The agents display similar pharmacokinetics. Clinical studies in patients with serious infections (intra-abdominal infection, respiratory infection, septicemia, febrile neutropenia) report similar bacteriological and clinical cure rates with imipenem and meropenem. Meropenem is approved for the treatment of bacterial meningitis, whereas imipenem is not. Adverse effects are similar.

CONCLUSIONS

Current literature supports the use of imipenem at a dose of 500 mg every 6 h and meropenem at 1 g every 8 h for the treatment of severe infections. For the treatment of serious infections, imipenem (500 mg every 6 h or 2 g/day [$98/day]) is more economical than meropenem (1 g every 8 h or 3 g/day [$142/day]) based on acquisition cost.

ESBLs: A Clear and Present Danger?

Extended spectrum β-lactamases (ESBLs) are enzymes produced by a variety of Gram negative bacteria which confer an increased resistance to commonly used antibiotics. They are a worrying global public health issue as infections caused by such enzyme-producing organisms are associated with a higher morbidity and mortality and greater fiscal burden. Coupled with increasing prevalence rates worldwide and an ever diminishing supply in the antibiotic armamentarium, these enzymes represent a clear and present danger to public health. This article aims to give an overview of the current situation regarding ESBLs, with a focus on the epidemiology and management of such infections.

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.

Biapenem

Biapenem is a new parenteral carbapenem antibacterial agent with a broad spectrum of in vitro antibacterial activity encompassing many Gram-negative and Gram-positive aerobic and anaerobic bacteria, including species producing beta-lactamases. Biapenem is more stable than imipenem, meropenem and panipenem to hydrolysis by human renal dihydropeptidase-I (DHP-I), and therefore does not require the coadministration of a DHP-I inhibitor. After intravenous administration, biapenem is widely distributed and penetrates well into various tissues (e.g. lung tissue) and body fluids (e.g. sputum, pleural effusion, abdominal cavity fluid). In randomised, nonblind or double-blind clinical trials, biapenem showed good clinical and bacteriological efficacy (similar to that of imipenem/ cilastatin) in the treatment of adult patients with intra-abdominal infections, lower respiratory infections or complicated urinary tract infections. Biapenem is generally well tolerated. The most common adverse events in clinical trials were skin eruptions/rashes, nausea and diarrhoea.

Postantibiotic effect of meropenem and ciprofloxacin in the presence of 5-fluorouracil

BACKGROUND

The postantibiotic effect (PAE) of meropenem and ciprofloxacin was studied in the presence of the antineoplastic agent 5-fluorouracil (5-FU). The purpose of the study was to investigate whether the PAEs of the combinations differed from the PAEs of the antibiotics alone.

METHODS

The PAEs of the combinations of 5-FU plus meropenem or ciprofloxacin were determined with viable counts against four reference strains of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli and two clinical isolates of S. epidermidis. The results were compared with the PAEs of the antibiotics drugs and 5-FU alone. The gram-positive strains were tested for slime production, both alone and in the presence of 5-FU.

RESULTS

Against two of the three tested strains of S. epidermidis, the combination of ciprofloxacin and 5-FU gave a synergistic prolongation of the PAE in comparison with the PAEs induced by the drugs alone. The combinations showed indifference against the other bacteria. The combination of meropenem and 5-FU had a synergistic PAE against one of the three tested strains of S. epidermidis and an additive effect against E. coli but showed indifference against the rest of the strains.

CONCLUSIONS

The presence of 5-FU did not influence the PAEs of the antibiotics against most of the tested strains, but caused a synergistic prolongation of the PAEs induced by ciprofloxacin and meropenem against some of the tested strains of S. epidermidis. 5-FU inhibited slime production in the same S. epidermidis strains, which might have contributed to the longer PAE.

Bacterial resistance: a worldwide problem

The therapeutic crisis produced by emerging antimicrobial resistances has compromised the chemotherapy of hospitalized patients with serious infections. For the most prevalent resistance problems, meropenem, a new carbapenem, appears to provide a potency and spectrum for: 1) extended-spectrum beta-lactamase-producing Enterobacteriaceae; 2) Bush-Jacoby-Merdeiros group 1 enzyme-producing ceftazidime-resistant Enterobacter spp., Citrobacter freundii, and some Serratia spp.; 3) ceftazidime- and imipenem-resistant Pseudomonas aeruginosa; and 4) some Streptococcus spp. with elevated penicillin MICs. Documented in vitro study results using 1997 gram-negative blood stream infection isolates indicate a wider spectrum and a two- to fourfold greater potency for meropenem compared with imipenem. This was especially true for P. aeruginosa where 93.4% of strains were susceptible to meropenem (84.1% for imipenem). Also among over 30,000 reported in vitro meropenem results from the United States and Europe, 90.6% of gram-positive cocci and 99.1% of anaerobes were inhibited at < or = 4 microg/ml. Over 90% of ceftazidime-resistant blood stream infection strains were meropenem susceptible, a rate greater than those of imipenem, ciprofloxacin, and gentamicin. As the clinical utility of many contemporary antimicrobial agents is challenged by emerging resistance, the carbapenems (meropenem, imipenem) appear positioned for a greater role in the treatment of infections in hospitalized patients.

A review of the in vitro activity of meropenem and comparative antimicrobial agents tested against 30,254 aerobic and anaerobic pathogens isolated world wide

The in vitro activity of meropenem (formerly SM-7738), a new carbapenem, was compared with that of imipenem and five other broad-spectrum antimicrobials (ceftazidime, cefotaxime, piperacillin, piperacillin/tazobactam, and ciprofloxacin) against 30,254 clinically significant pathogens isolated in nine countries worldwide. Overall, the carbapenems, meropenem and imipenem, were the most active drugs. Meropenem was four- to 64-fold more active than imipenem against Gram-negative bacteria, including the Enterobacteriaceae, Pseudomonas aeruginosa, Burkholderia cepacia, Haemophilus influenzae, and Neisseria meningitidis. Meropenem was also quite active against ceftazidime-resistant strains of Enterobacteriaceae, inhibiting 87.5 to 100% at < or = 4 micrograms/ml. In contrast, imipenem was four- to eight-fold more active than meropenem against Gram-positive species, including methicillin-susceptible strains of Staphylococcus aureus and Staphylococcus epidermidis, Streptococcus pneumoniae, and Enterococcus faecalis. Among the anaerobes, strains resistant to meropenem or imipenem were encountered very rarely. These extensive data provide additional in vitro support for the clinical use of meropenem as a broad spectrum antimicrobial agent active against key pathogenic species of bacteria.

Activities of levofloxacin, ofloxacin, and ciprofloxacin, alone and in combination with amikacin, against acinetobacters as determined by checkerboard and time-kill studies

A total of 101 Acinetobacter genospecies (77 Acinetobacter baumannii strains and 24 non-A. baumannii strains) were tested for their susceptibilities to levofloxacin, ofloxacin, and ciprofloxacin and for synergy between the quinolones and amikacin by checkerboard titration and time-kill analyses. The MICs at which 50% of the isolates are inhibited (MIC50)/MIC90s for the 101 strains were as follows (in micrograms per milliliter): levofloxacin, 0.25/16.0; ofloxacin, 0.5/32.0; ciprofloxacin, 0.25/> 64.0; and amikacin, 1.0/> 32.0. At empiric breakpoints of < or = 2.0 microg/ml, 61% of the strains were susceptible to all three quinolones. At a breakpoint of < or = 16.0 microg/ml, 84% of the strains were susceptible to amikacin. Checkerboard titrations yielded synergistic fractional inhibitory concentration (FIC) indices (< or = 0.5) for one strain with levofloxacin and amikacin and for two strains with ofloxacin and amikacin. Indices of > 0.5 to 1.0 were seen for 57, 54, and 55 strains with levofloxacin plus amikacin, ofloxacin plus amikacin, and ciprofloxacin plus amikacin, respectively, and indices of > 1.0 in 43, 45, and 46 strains, respectively, were found with the above three combinations. No strains yielded antagonistic FIC indices (> 4.0). Most FIC results of > 1.0 occurred in strains for which the quinolone MICs were > 2.0 microg/ml and for which the amikacin MICs were > or = 32.0 microg/ml. By contrast, synergy (defined as > or = 2 log10 decrease compared to the more active compound alone by time-kill analysis) was found in all seven strains tested for which the quinolone MICs were < or = 2.0 microg/ml. For eight other strains for which the quinolone MICs were > 2.0 microg/ml as determined by time-kill analysis, quinolone and amikacin concentrations in combination were usually too high to permit clinical use. Time-kill analysis was found to be more sensitive in detecting synergy than was the checkerboard method.

Activities of beta-lactams against Acinetobacter genospecies as determined by agar dilution and E-test MIC methods

The agar dilution MIC method was used to test activities of ticarcillin, ticarcillin-clavulanate, amoxicillin, amoxicillin-clavulanate, ampicillin, ampicillin-sulbactam, piperacillin, piperacillin-tazobactam, inhibitors alone, ceftazidime, and imipenem against 237 Acinetobacter genospecies. A total of 93.2% of strains were beta-lactamase positive by the chromogenic cephalosporin method. Overall, ampicillin-sulbactam was the most active combination against all strains (MIC at which 50% of the isolates are inhibited [MIC50] and MIC90, 4.0 and 32.0 microg/ml; 86.9% susceptible at < or = 16 microg/ml), followed by ticarcillin-clavulanate (16.0 and 128.0 microg/ml; 85.7% susceptible at < or = 64 microg/ml), piperacillin-tazobactam (16.0 and 128.0 microg/ml; 84.8% susceptible at < or = 64 microg/ml), and amoxicillin-clavulanate (16.0 and 64.0 microg/ml; 54.4% susceptible at < or =16 microg/ml). Ceftazidime and imipenem yielded MIC50s and MIC90s of 8.0 and 64.0 microg/ml (ceftazidime) and 0.5 and 1.0 microg/ml (imipenem), respectively; 71.3% of strains were susceptible to ceftazidime at < or = 16 microg/ml, and 99.2% were susceptible to imipenem at < or = 8 microg/ml. Sulbactam was the most active beta-lactamase inhibitor alone (MIC50 and MIC90, 2.0 and 16.0 microg/ml); clavulanate and tazobactam were less active (16.0 and 32.0 microg/ml for both compounds). Enhancement of beta-lactams by beta-lactamase inhibitors was not always seen in beta-lactamase-positive strains, and activity of combinations such as ampicillin-sulbactam was due to the inhibitor alone. Acinetobacter baumannii was the most resistant genospecies. By contrast, Acinetobacter haemolyticus, Acinetobacter calcoaceticus, Acinetobacter johnsonii, Acinetobacter junii, Acinetobacter radioresistens, and other non-Acinetobacter baumannii strains were more susceptible to all compounds tested. E-test MICs were within 1 dilution of agar dilution MICs in 38.4 to 89.6% of cases and within 2 dilutions in 61.6 to 98.6% of cases.

Imipenem/cilastatin: an update of its antibacterial activity, pharmacokinetics and therapeutic efficacy in the treatment of serious infections

The prototype carbapenem antibacterial agent imipenem has a very broad spectrum of antibacterial activity, encompassing most Gram-negative and Gram-positive aerobes and anaerobes, including most beta-lactamase-producing species. It is coadministered with a renal dehydropeptidase inhibitor, cilastatin, in order to prevent its renal metabolism in clinical use. Extensive clinical experience gained with imipenem/cilastatin has shown it to provide effective monotherapy for septicaemia, neutropenic fever, and intra-abdominal, lower respiratory tract, genitourinary, gynaecological, skin and soft tissues, and bone and joint infections. In these indications, imipenem/cilastatin generally exhibits similar efficacy to broad-spectrum cephalosporins and other carbapenems and is at least equivalent to standard aminoglycoside-based and other combination regimens. Imipenem/cilastatin is generally well tolerated by adults and children, with local injection site events, gastrointestinal disturbances and dermatological reactions being the most common adverse events. Seizures have also been reported, occurring mostly in patients with impaired renal function or CNS pathology, or with excessive dosage. Although it is no longer a unique compound, as newer carbapenems such as meropenem are becoming available, imipenem/cilastatin nevertheless remains an important agent with established efficacy as monotherapy for moderate to severe bacterial infections. Its particular niche is in treating infections known or suspected to be caused by multiresistant pathogens.

Infection Control in a Country with Annual Inflation of 3,600%

The economic crisis that has been seen worldwide affects developing countries such as Brazil even more severely. Worsening budget shortfalls for the healthcare system progressively threaten patient care. Infection control programs also are affected, and basic preventive policies are not implemented. Infection control practitioners face lack of equipment and poor microbiological support. In contrast, the motivation of the infection control people can be maintained through training courses, conferences, and meetings. Administrative support may be the most important single factor determining success in decreasing the infection control rate and should be (but is not always) provided, given that several infection control measures are cost effective.