The evolution of Pseudomonas aeruginosa during antibiotic rotation in a medical intensive care unit: the RADAR-trial

Bacterial spread between patients may contribute to the high prevalence of antibiotic-resistant pathogens within ICUs. The aim of this study was to evaluate the fate of Pseudomonas aeruginosa during the different antibiotic regimens. Susceptibility patterns and genotyping were performed to determine whether there was a predominant clone and to track the spread of resistant strains within the unit. Twenty-eight different ribotypes were found among 82 Pseudomonas isolates. Four ribotypes accounted for 42 (51%) isolates and were designated the "major clones" occurring throughout multiple cycles. The ribotypes with multiple occurrences were more resistant to antibiotics than ribotypes that appeared only once. The correlation of antibiotic use with antibiotic resistance and the finding of a large number of ribotypes suggested that de novo development of antibiotic resistance is a likely event in P. aeruginosa. In addition, ribotypes associated with antibiotic resistance appeared to have a survival advantage and can become frequent colonizers in the ICU.

Toxicity classification and evaluation of four pharmaceuticals classes: antibiotics, antineoplastics, cardiovascular, and sex hormones

Four different classes of environmental concern are quantitatively and qualitatively assessed for environmental hazards; antibiotics (n = 226), antineoplastics (n = 81), cardiovascular (n = 272), and sex hormones (n = 92). These along with an ECOSAR scan of all pharmaceuticals (n = 2848) were then classified according to the OECD aquatic toxicity classification system. The predicted species susceptibility is: daphnid > fish > algae, and the predicted rank order of relative toxicity: sex hormones > cardiovascular = antibiotics > antineoplastics (Table 1). Generally, a relatively large proportion (1/3) of all pharmaceuticals are potentially very toxic to aquatic organisms (Table 2). The qualitative risk assessment ranking relative to probability and potential severity for human and environmental health effects is: antibiotics > sex hormones > cardiovascular > antineoplastics. (Q)SARs and pharmacodynamic information should be used to prioritize and steer experimental risk assessments of pharmaceuticals, and potentially, also be used in new drug discovery optimizing efficacy and in minimising environmental hazards of new products. Nuclear receptors are relatively well conserved in evolution. Currently, antibacterial resistance represents the most significant human health hazard, and potentially the largest non-target organism hazard is sex hormones acting as endocrine modulators in wildlife. Data for the individual compounds are accessible via.

Retour vers la sensibilité aux antibiotiques des souches de Staphylococcus aureus résistant à la méticilline (SARM) : relation entre génotype et antibiotype

The objective of our study was to investigate the relationship between molecular epidemiology and antibiotic susceptibility of MRSA during a four-year period. In this aim, we determined the antibiotype of all MRSA identified during a yearly period of 3 months and typed 50 consecutive non-replicate MRSA isolates of each year. We also recorded antibiotic use. Susceptibility rates to gentamicin, tobramycin and ofloxacin remained stable, respectively, 95, 16 and 4%. In contrast, the proportion of MRSA susceptible to erythromycin progressively increased from 7.0% to 32.5% (P < 0.001). PFGE analysis of genomic DNA from the 200 isolates revealed 15 different clones. We identified two epidemic clones, which contained 150 (clone A) and 28 isolates (clone C), respectively. The proportion of isolates belonging to clone A decreased during the study from 86% to 66%. Conversely, clone C increased from 4% to 22%. The increase of erythromycin-susceptibility within MRSA was caused by the emergence of clone C. Non-epidemic strains were more frequently susceptible to ofloxacin (31.8% vs. 1.1%) and tobramycin (45.4% vs. 16.8%) than epidemic strains. Antimicrobial use had not significantly varied during the study. The proportion of beta-lactams, fluoroquinolones, macrolides and aminosides was 71.8, 13.9, 5.0 and 3.8% of the total antibiotic use, respectively. In our hospital, MRSA isolates became more susceptible to antimicrobial of minor use. The selection pressure exerted by beta-lactams and fluoroquinolones was in favor of the spread of strains resistant to these both major antibiotic classes.

Appropriate use of the carbapenems

The carbapenems are a group of broad-spectrum beta-lactam antibiotic agents of which there are three parenteral preparations currently available in South Africa, namely imimpenem/cilastatin, meropenem and ertapenem. Owing to the fact that imipenem/cilastatin and meropenem have a broad spectrum of activity that includes Pseudomonas and Acinetobacter species, they are ideal antibiotics for treatment of severe nosocomial infections. In contrast, ertapenem has limited in vitro activity against the latter non-fermentative gram-negative bacteria and is therefore more suitable for the treatment of certain severe community-acquired infections. This statement arises out of concerns about the general abuse of antibiotics such as the carbapenems, with the primary intention of highlighting the appropriate use of these agents.

Mutant prevention concentration: a new tool for choosing treatment in nontuberculous mycobacterial infections

The mutant prevention concentration (MPC) of fluoroquinolones, linezolid, rifabutin, rifampicin and macrolides was determined in 16 nontuberculous Mycobacterium species in order to compare the incidence of resistant mutant occurrence for different antibiotics. Linezolid showed good activity against Mycobacterium gordonae and Mycobacterium kansasii. Rifabutin had a lower MPC values than rifampicin. The fluoroquinolones were more active against M. gordonae and Mycobacterium chelonae. Clarithromycin had better MPC values than azithromycin but its intracellular concentration was high. Mutant prevention concentration may help to establish a better clinico-microbiological correlation, the sub-populations of drug-resistant micro-organisms may be detected by that method. It is still important to administer correct drug doses, to use combined therapies and to find new drugs that are useful in the treatment of these infections.

Characterization of multiple-antimicrobial-resistant Escherichia coli isolates from diseased chickens and swine in China

Escherichia coli isolates from diseased piglets (n = 89) and chickens (n = 71) in China were characterized for O serogroups, virulence genes, antimicrobial susceptibility, class 1 integrons, and mechanisms of fluoroquinolone resistance. O78 was the most common serogroup identified (63%) among the chicken E. coli isolates. Most isolates were PCR positive for the increased serum survival gene (iss; 97%) and the temperature-sensitive hemagglutinin gene (tsh; 93%). The O serogroups of swine E. coli were not those typically associated with pathogenic strains, nor did they posses common characteristic virulence factors. Twenty-three serogroups were identified among the swine isolates; however, 38% were O nontypeable. Overall, isolates displayed resistance to nalidixic acid (100%), tetracycline (98%), sulfamethoxazole (84%), ampicillin (79%), streptomycin (77%), and trimethoprim-sulfamethoxazole (76%). Among the fluoroquinolones, resistance ranged between 64% to levofloxacin, 79% to ciprofloxacin, and 95% to difloxacin. DNA sequencing of gyrA, gyrB, parC, and parE quinolone resistance-determining regions of 39 nalidixic acid-resistant E. coli isolates revealed that a single gyrA mutation was found in all of the isolates; mutations in parC together with double gyrA mutations conferred high-level resistance to fluoroquinolones (ciprofloxacin MIC, >/=8 microg/ml). Class 1 integrons were identified in 17 (19%) isolates from swine and 42 (47%) from chickens. The majority of integrons possessed genes conferring resistance to streptomycin and trimethoprim. These findings suggest that multiple-antimicrobial-resistant E. coli isolates, including fluoroquinolone-resistant variants, are commonly present among diseased swine and chickens in China, and they also suggest the need for the introduction of surveillance programs in China to monitor antimicrobial resistance in pathogenic bacteria that can be potentially transmitted to humans from food animals.

["In vitro" activity of ten antimicrobial agents against anaerobic bacteria. A collaborative study, 1999-2002]

The antimicrobial activity of ampicillin, ampicillin-sulbactam, cefoxitin, ceftriaxone, imipenem, piperacillin, piperacillin-tazobactam, clindamycin, metronidazole, and azitromycin was assesed against 166 strains of anaerobic bacteria recovered from eight hospitals in Buenos Aires. The strains studied were Bacteroides fragilis group (65), Fusobacterium spp. (26), Prevotella spp. (21), Porphyromonas spp. (10), Clostridium difficile (10), other clostridia (12), and gram-positive cocci (22). The MICs were determined by the agar dilution method according to NCCLS document M11-A5. Metronidazole and piperacillin-tazobactam were the most active antimicrobial agents tested and exhibited MIC90 values of < or = 2 microg/ml and < or = 4 microg/ml against gram-negative organisms, and < or = 2 microg/ml, and < or = 8 microg/ml against gram-positive organisms, respectively. Among beta-lactams the activity against gram-negative rods was in the following order: imipenem > piperacillin > cefoxitin > ceftriaxone > ampicillin. Among the gram-positive bacteria the decreased activity was: piperacillin > imipenem > cefoxitin > ceftriaxone > ampicillin. The majority of the species studied showed different degrees of resistance to clindamycin and azitromycin. Nevertheless, 90% of Fusobacterium nucleatum and Porphyromonas spp. isolates were inhibited by 0.125 mg/ml of clindamycin and azitromycin, respectively.

Short-Duration Therapy for Respiratory Tract Infections

Antimicrobial therapy for community-acquired respiratory tract infections (CARTIs) must be of sufficient duration to result in clinical cure and bacterial eradication. Elimination of the causative bacteria may prevent disease progression, relapse, or recurrence while minimizing the risk for emergence of resistant bacterial strains. Standard 10-day courses of antibiotic therapy often are not completed by patients. This may decrease the likelihood of bacterial eradication and contribute to increased selection of resistant organisms. The ideal antimicrobial agent for the treatment of CARTIs would have an appropriate pharmacokinetic/pharmacodynamic profile for short-course therapy (eg, 5 days) without loss of either clinical or bacteriologic efficacy. Short-course therapy for CARTIs (such as acute bacterial maxillary sinusitis, acute exacerbations of chronic bronchitis, community-acquired pneumonia) has been demonstrated to be effective with antibiotics from several different classes, including the ketolide antimicrobials.

The importance of appropriate antimicrobial dosing: pharmacokinetic and pharmacodynamic considerations

The increasing antimicrobial resistance of common respiratory pathogens has led to a reevaluation of the selection of antimicrobial dosing regimens in terms of their pharmacokinetic (PK) and pharmacodynamic (PD) properties. Pharmacokinetics, when considered as part of a specific dosing regimen, can help determine the time course of drug concentrations in the serum, tissues, body fluids, and at the site of infection. Pharmacodynamics provides surrogate markers for clinical and bacteriologic efficacy based on the relationships between the serum and tissue concentrations of selected antimicrobial agents relative to the mean inhibitory concentrations of causative bacteria over time. Ultimately, the interrelationships between PK and PD parameters measured for standard dosing regimens determine the time course of the drug's concentration at the site of infection and the impact of the agent's bacteriologic and clinical efficacy. In this review, the distinctive patterns of antimicrobial activity based on PK/PD parameters are discussed. Various antibiotics and bacterial pathogens are used as models to demonstrate the utility of PK/PD parameters in predicting the in vivo efficacy of antimicrobial therapy. The use of computer modeling with Monte Carlo population simulations can further enhance the predictability of antimicrobial efficacy when using PK/PD parameters. This article also provides a reevaluation of bacterial susceptibility breakpoints defined by the National Committee for Clinical Laboratory Standards contrasted with the use of PK/PD parameters.

Cationic antimicrobial peptides : issues for potential clinical use

Many different types of organisms use antimicrobial peptides, typically 20-40 amino acids in length, for defence against infection. Most are capable of rapidly killing a wide range of microbial cells. They have been classified according to their active structures into six extensive groups. It is not yet clear how these peptides kill bacterial cells, but it is widely believed that some cationic antimicrobial peptides kill by disrupting bacterial membranes, allowing the free exchange of intra- and extra-cellular ions. The selectivity of these peptides appears to relate to differences between the external membranes of prokaryotic and eukaryotic cells. The action of the peptides may involve the formation of 'barrel-stave' or 'torroidal' pores, the introduction of packing defects in the membrane phospholipids, or large-scale disruption of the membrane by a very dense aggregation of parallel-oriented peptide, called the 'carpet mechanism'. Antimicrobial peptides are attractive candidates for clinical development because of their selectivity, their speed of action and because bacteria may not easily develop resistance against them. Some antimicrobial peptides are already in clinical and commercial use, including ambicin (nisin), polymixin B and gramicidin S. There have been several attempts at developing peptides to make them more suitable for clinical use. For those peptides that act against bacterial membranes, it is possible to differentiate between those structural features that contribute to the specificity of initial membrane binding and those that contribute to the subsequent breach of membrane integrity. The design of novel antimicrobial peptides would necessitate the optimisation of multiple parameters, a problem that has proved difficult to solve. Potential problems to be overcome include high production costs, toxicity against eukaryotic cells, susceptibility to proteolytic degradation and the development of allergies to the peptides. Biosynthesis, using recombinant DNA techniques, could make commercial-scale synthesis feasible but the peptides are usually lethal to the micro-organisms used to produce them. Proteolytic degradation can be reduced by modifying the peptides to contain nonstandard amino acids, or by restricting the use of peptides to topical applications. The problem of sensitisation could be overcome by the use of our own natural antibiotics to prevent or treat infections. Despite early hopes that bacteria would not easily develop resistance to antimicrobial peptides, it is clear that some strains of bacteria already have.

Surveillance of multi-drug resistant Pseudomonas aeruginosa in an urban tertiary-care teaching hospital

Antimicrobial resistance in Pseudomonas aeruginosa is a serious clinical problem. To determine the incidence of multi-drug resistant P. aeruginosa, resistance rates of P. aeruginosa clinical isolates against commonly used antibiotics were evaluated for the period 1998 to 2002. Multi-drug resistance was defined as resistance to at least three of the four drugs, ceftazidime, imipenem, ciprofloxacin, and tobramycin. Resistance to most anti-pseudomonal agents has increased by >20% over the five-year period, with dramatic increases observed with fluoroquinolones, tobramycin, and imipenem (resistance increased by 34-37%). In 1998, 78% of isolates were susceptible to all four anti-pseudomonal agents and no isolate was considered multi-drug resistant. However, in 2002, only 27% of isolates were sensitive to all four of the drugs and 32% were considered multi-drug resistant. Multi-drug resistance in individual institutions may be significantly higher than rates reported in nationwide surveillance studies and may more accurately reflect the true magnitude of local resistance problems. On-going surveillance within individual institutions is critical for the selection of appropriate empiric antimicrobial therapy.

Sensibilidad a antimicrobianos del estreptococo del grupo B de transmisión vertical. Estudio multicéntrico

INTRODUCTION

To investigate the susceptibility of group B streptococci (GBS) to macrolides and lincosamides and assess alternatives for intrapartum chemoprophylaxis in women allergic to penicillin and colonized by a GBS strain resistant to these antibiotics.

METHODS

Multicenter study performed with 131 strains isolated between 1997-2002 from newborns diagnosed with early-onset GBS disease and 479 strains collected in 2002 from the vagina or rectum of pregnant women.

RESULTS

All the GBS (100%) were susceptible to penicillin, ampicillin, vancomycin, quinupristin/dalfopristin, levofloxacin and teicoplanin. Resistance rates were as follows: 12.45% to erythromycin and azithromycin, 11.80% to clindamycin, 11.31%, to josamycin, 1.80% to telithromycin and 0.32% to fosfomycin. Seventy-nine strains had a constitutive MLSB phenotype of resistance, 4 an inducible MLSB phenotype, 3 an M phenotype and 3 were resistant to clindamycin but susceptible to macrolides. The MIC for erythromycin and azithromycin was > 32 mg/L in more than 85% of GBS strains with a constitutive MLSB phenotype, from 0.5 to 4 mg/L in those with an inducible MLSB, and 4 mg/L in those with phenotype M. Fifty-one telithromycin-sensitive strains (all with a constitutive MLSB phenotype) showed induced resistance to telithromycin when erythromycin was present. No significant differences in antimicrobial resistance were found between GBS strains producing invasive neonatal disease and maternal isolates, or among strains from different geographic areas.

CONCLUSIONS

The high rate of resistance to macrolides and lincosamides in our area makes susceptibility testing mandatory for GBS strains isolated from pregnant women allergic to penicillin.

Combating antibiotic resistance

BACKGROUND

The ADA Council on Scientific Affairs developed this report to provide dental professionals with current information on antibiotic resistance and related considerations about the clinical use of antibiotics that are unique to the practice of dentistry.

OVERVIEW

This report addresses the association between the overuse of antibiotics and the development of resistant bacteria. The Council also presents a set of clinical guidelines that urges dentists to consider using narrow-spectrum antibacterial drugs in simple infections to minimize disturbance of the normal microflora, and to preserve the use of broad-spectrum drugs for more complex infections.

CONCLUSIONS AND PRACTICE IMPLICATIONS

The Council recommends the prudent and appropriate use of antibacterial drugs to prolong their efficacy and promotes reserving their use for the management of active infectious disease and the prevention of hematogenously spread infection, such as infective endocarditis or total joint infection, in high-risk patients.

NMR evidence for independent domain structures in zoocin A, an antibacterial exoenzyme

NMR was used to obtain spectroscopic evidence supporting a two domain model for zoocin A in which an N-terminal catalytic domain is linked by a threonine-proline rich linker to a target recognition domain responsible for recognizing the cell wall of bacteria susceptible to the bacteriolytic action of the enzyme. When cloned and separately expressed, each domain retains the folding found in the whole enzyme. Additionally, spectroscopy suggests that the target recognition domain has a conformation typical of a soluble globular protein, while the catalytic domain aggregates at low millimolar concentrations.

Pharmacological treatment of acute otitis media in children. A comparison among seven locations: Tenerife, Barcelona and Valencia (Spain), Toulouse (France), Smolensk (Russia), Bratislava (Slovakia) and Sofia (Bulgaria)

OBJECTIVE

To describe patterns observed in the treatment of acute otitis media (AOM) in several locations of five countries.

PATIENTS AND METHODS

Cross-sectional, descriptive study. Random sample of 12,264 paediatric outpatients seen by paediatricians or general practitioners (GPs). Data on patient demographics, diagnoses and treatment were collected. Diagnoses were coded by ICD-9 and drugs by ATC classification. Patients diagnosed with AOM (ICD-9 codes: 381 and 382) were selected for analysis.

RESULTS

Cases of AOM (873) accounted for 7.1% of the sample. There is a clear variation in the percentage of children diagnosed with AOM and treated with antibiotics in the different locations, antibiotic prescriptions being higher in Barcelona (93% of children), and lowest in Smolensk (56.4 % of children were treated without antibiotics). The antibiotics used varied widely: ampicillin use is almost limited to Smolensk (26.7%) and Bratislava (13.8%), whereas amoxicillin plus clavulanic acid is the choice in Toulouse (33.8%), Valencia (30.2%) and Barcelona (28.9%), and cephalosporins are more frequently prescribed in Tenerife (51.7%). Finally, macrolides are used in Barcelona (18.3%), Valencia (17.5%) and Tenerife (13.6%), but not prescribed in Toulouse or Sofia. Prescriptions of anti-inflammatory drugs were only relevant in Valencia (31.7%), Tenerife (27.2%) and Toulouse (17.4%) and of otological preparations in Sofia, where almost each child received ear drops (91.9%). Nasal preparations are commonly used only in Sofia (41.9%), Bratislava (65.5%) and Smolensk (68.6%).

CONCLUSION

Despite the general agreement of most guidelines, wide differences in the treatment of uncomplicated AOM in children are observed. Non-antibiotic therapy for AOM and the use of first-choice antibiotics should be more actively encouraged in the primary care centres. Studies to measure prevailing rates of antibiotic resistance in these populations are needed.

Evaluation of the mandibular third molar pericoronitis flora and its susceptibility to different antibiotics prescribed in france

This work assessed the polymicrobial flora of mandibular third molar pericoronitis. Obligate anaerobes were found in almost all cases (32 of 35). Amoxicillin and pristinamycin were the most effective against the flora, particularly aerobic organisms. Metronidazole alone or combined with spiramycin was the most effective drug against obligate anaerobes.

Designing Antibacterial Compounds through a Topological Substructural Approach

A novel application of TOPological Substructural MOlecular DEsign (TOPS-MODE) was carried out in antibacterial drugs using computer-aided molecular design. Two series of compounds, one containing antibacterial and the other containing non-antibacterial compounds, were processed by a k-means cluster analysis in order to design training and predicting series. All clusters had a p-level < 0.005. Afterward, a linear classification function has been derived toward discrimination between antibacterial and non-antibacterial compounds. The model correctly classifies 94% of active and 86% of inactive compounds in the training series. More specifically, the model showed a global good classification of 91%, i.e., 263 cases out of 289. In predicting series, the model has shown overall predictabilities of 91 and 83% for active and inactive compounds, respectively. Thereby, the model has a global percentage of good classification of 89%. The TOPS-MODE approach, also, similarly compares with respect to one of the most useful models for antimicrobials selection reported to date.

Antibiotic Resistance of Bacterial Ventilator-Associated Pneumonia in Surgical Intensive Care Units

Ventilator-associated pneumonia (VAP) is the most common infection in intensive care units. It is caused by prolonged hospitalization and results in high mortality rates. This retrospective clinical study, of 140 patients in a surgical intensive care unit, aimed to identify the bacterial agents responsible for VAP infection, and determine antibiotic resistance rates in VAP. Antibiotic sensitivity was evaluated by culturing and testing tracheal aspirates from patients with clinical and radiological findings of VAP. The bacteria isolated most frequently were Pseudomonas aeruginosa (33.9%), Staphylococcus aureus (30.0%), Acinetobacter baumannii (26.1%), and Enterobacter species (4.3%). A. baumannii was more prevalent than in previous years. The results of antibiotic sensitivity testing suggested sulbactam/cefoperazone as the most appropriate drug for treating these patients. We suggest, however, that when staphylococcal pneumonia is suspected, a glycopeptide (vancomycin or teicoplanin) or combined trimethoprimsulfamethoxazole is used as first-line therapy until sensitivity results are obtained. In conclusion, development of antibiotic policies for individual hospitals can reduce high antibiotic resistance rates due to VAP.

Intracellular pharmacodynamics of antibiotics

This article establishes the pharmacokinetic-pharmacodynamic parameters that are important when considering the intracellular activity of antibiotics. Generally speaking, the main classes of antibiotics seem to share globally the same properties against extracellular and intracellular organisms. The specific cellular pharmacokinetic properties may modulate those parameters so as to let other ones to become critical. Simple rules, such as equating accumulation and activity, are certainly incorrect, and other determinants need to be added to the equation. Finally, this article emphasizes the fact that much remains to be done in this area before rational therapeutic choices can be made.

Antibiotics GE23077, Novel Inhibitors of Bacterial RNA Polymerase I. Taxonomy, Isolation and Characterization

GE 23077 factors A1, A2, B1 and B2 are novel antibiotics isolated from fermentation broths of an Actinomadura sp. strain. GE23077 antibiotics are cyclic peptides, which inhibit Escherichia coli RNA polymerase at nM concentrations. Both rifampicin-sensitive and rifampicin-resistant polymerases are inhibited, whereas E. coli DNA polymerase and wheat germ RNA polymerase are substantially not affected. In spite of the potent activity on the enzyme, the antibiotics generally show poor activity against whole cell bacteria. The spectrum of activity is restricted to Moraxella catarrhalis, including clinical isolates, with partial activity against Neisseria gonorrhoeae and Mycobacterium smegmatis.

[Effective antibacterial therapy in otorhinolaryngology: bacteriological rationale]

The article presents current views on etiopathogenesis of the diseases associated with contamination with microorganisms; reviews inflammatory ENT diseases in terms of current literature on clinical microbiology of these diseases; characterizes microorganisms more or less specific for each relevant nosological entity; analyses basic groups of antibacterial drugs with formulation of bacteriologically grounded principles of initial antibacterial therapy of ENT inflammation.