Clinical importance of extended-spectrum beta-lactamase (PER-1-type)-producing Acinetobacter spp. and Pseudomonas aeruginosa strains

Co-regulation of biofilm formation and antimicrobial resistance in Acinetobacter baumannii: from mechanisms to therapeutic strategies

In recent years, multidrug-resistant Acinetobacter baumannii has emerged globally as a major threat to the healthcare system. It is now listed by the World Health Organization as a priority one for the need of new therapeutic agents. A. baumannii has the capacity to develop robust biofilms on biotic and abiotic surfaces. Biofilm development allows these bacteria to resist various environmental stressors, including antibiotics and lack of nutrients or water, which in turn allows the persistence of A. baumannii in the hospital environment and further outbreaks. Investigation into therapeutic alternatives that will act on both biofilm formation and antimicrobial resistance (AMR) is sorely needed. The aim of the present review is to critically discuss the various mechanisms by which AMR and biofilm formation may be co-regulated in A. baumannii in an attempt to shed light on paths towards novel therapeutic opportunities. After discussing the clinical importance of A. baumannii, this critical review highlights biofilm-formation genes that may be associated with the co-regulation of AMR. Particularly worthy of consideration are genes regulating the quorum sensing system AbaI/AbaR, AbOmpA (OmpA protein), Bap (biofilm-associated protein), the two-component regulatory system BfmRS, the PER-1 β-lactamase, EpsA, and PTK. Finally, this review discusses ongoing experimental therapeutic strategies to fight A. baumannii infections, namely vaccine development, quorum sensing interference, nanoparticles, metal ions, natural products, antimicrobial peptides, and phage therapy. A better understanding of the mechanisms that co-regulate biofilm formation and AMR will help identify new therapeutic targets, as combined approaches may confer synergistic benefits for effective and safer treatments.

Synergistic Role of Plant Extracts and Essential Oils against Multidrug Resistance and Gram-Negative Bacterial Strains Producing Extended-Spectrum β-Lactamases

Plants, being the significant and natural source of medication for humankind against several ailments with characteristic substances hidden on them, have been recognized for many centuries. Accessibility of various methodologies for the revelation of therapeutically characteristic items has opened new avenues to redefine plants as the best reservoirs of new structural types. The role of plant metabolites to hinder the development and movement of pathogenic microbes is cherished. Production of extended-spectrum β-lactamases is an amazing tolerance mechanism that hinders the antibacterial treatment of infections caused by Gram-negative bacteria and is a serious problem for the current antimicrobial compounds. The exploration of the invention from sources of plant metabolites gives sustenance against the concern of the development of resistant pathogens. Essential oils are volatile, natural, complex compounds described by a solid odor and are framed by aromatic plants as secondary metabolites. The bioactive properties of essential oils are commonly controlled by the characteristic compounds present in them. They have been commonly utilized for bactericidal, virucidal, fungicidal, antiparasitic, insecticidal, medicinal, and antioxidant applications. Alkaloids are plant secondary metabolites that have appeared to have strong pharmacological properties. The impact of alkaloids from Callistemon citrinus and Vernonia adoensis leaves on bacterial development and efflux pump activity was assessed on Pseudomonas aeruginosa. Plant-derived chemicals may have direct antibacterial activity and/or indirect antibacterial activity as antibiotic resistance modifying agents, increasing the efficiency of antibiotics when used in combination. The thorough screening of plant-derived bioactive chemicals as resistance-modifying agents, including those that can act synergistically with antibiotics, is a viable method to overcome bacterial resistance. The synergistic assessment studies with the plant extract/essential oil and the antibiotic compounds is essential with a target for achieving a redesigned model with sustainable effects which are appreciably noticeable in specific sites of the plants compared to the entirety of their individual parts.

Extended-spectrum β-lactamases: an update on their characteristics, epidemiology and detection

Extended-spectrum β-lactamase (ESBL)-producing Gram-negative pathogens are a major cause of resistance to expanded-spectrum β-lactam antibiotics. Since their discovery in the early 1980s, they have spread worldwide and an are now endemic in Enterobacterales isolated from both hospital-associated and community-acquired infections. As a result, they are a global public health concern. In the past, TEM- and SHV-type ESBLs were the predominant families of ESBLs. Today CTX-M-type enzymes are the most commonly found ESBL type with the CTX-M-15 variant dominating worldwide, followed in prevalence by CTX-M-14, and CTX-M-27 is emerging in certain parts of the world. The genes encoding ESBLs are often found on plasmids and harboured within transposons or insertion sequences, which has enabled their spread. In addition, the population of ESBL-producing Escherichia coli is dominated globally by a highly virulent and successful clone belonging to ST131. Today, there are many diagnostic tools available to the clinical microbiology laboratory and include both phenotypic and genotypic tests to detect β-lactamases. Unfortunately, when ESBLs are not identified in a timely manner, appropriate antimicrobial therapy is frequently delayed, resulting in poor clinical outcomes. Several analyses of clinical trials have shown mixed results with regards to whether a carbapenem must be used to treat serious infections caused by ESBLs or whether some of the older β-lactam-β-lactamase combinations such as piperacillin/tazobactam are appropriate. Some of the newer combinations such as ceftazidime/avibactam have demonstrated efficacy in patients. ESBL-producing Gram-negative pathogens will continue to be major contributor to antimicrobial resistance worldwide. It is essential that we remain vigilant about identifying them both in patient isolates and through surveillance studies.

Acinetobacter baumannii: Its Clinical Significance in Human and Veterinary Medicine

Acinetobacter baumannii is a Gram-negative, opportunistic pathogen, causing severe infections difficult to treat. The A. baumannii infection rate has increased year by year in human medicine and it is also considered as a major cause of nosocomial infections worldwide. This bacterium, also well known for its ability to form biofilms, has a strong environmental adaptability and the characteristics of multi-drug resistance. Indeed, strains showing fully resistant profiles represent a worrisome problem in clinical therapeutic treatment. Furthermore, A. baumannii-associated veterinary nosocomial infections has been reported in recent literature. Particularly, carbapenem-resistant A. baumannii can be considered an emerging opportunistic pathogen in human medicine as well as in veterinary medicine.

Multidrug Resistance (MDR) and Collateral Sensitivity in Bacteria, with Special Attention to Genetic and Evolutionary Aspects and to the Perspectives of Antimicrobial Peptides-A Review

Antibiotic poly-resistance (multidrug-, extreme-, and pan-drug resistance) is controlled by adaptive evolution. Darwinian and Lamarckian interpretations of resistance evolution are discussed. Arguments for, and against, pessimistic forecasts on a fatal “post-antibiotic era” are evaluated. In commensal niches, the appearance of a new antibiotic resistance often reduces fitness, but compensatory mutations may counteract this tendency. The appearance of new antibiotic resistance is frequently accompanied by a collateral sensitivity to other resistances. Organisms with an expanding open pan-genome, such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae, can withstand an increased number of resistances by exploiting their evolutionary plasticity and disseminating clonally or poly-clonally. Multidrug-resistant pathogen clones can become predominant under antibiotic stress conditions but, under the influence of negative frequency-dependent selection, are prevented from rising to dominance in a population in a commensal niche. Antimicrobial peptides have a great potential to combat multidrug resistance, since antibiotic-resistant bacteria have shown a high frequency of collateral sensitivity to antimicrobial peptides. In addition, the mobility patterns of antibiotic resistance, and antimicrobial peptide resistance, genes are completely different. The integron trade in commensal niches is fortunately limited by the species-specificity of resistance genes. Hence, we theorize that the suggested post-antibiotic era has not yet come, and indeed might never come.

High Prevalence of Multi-Drug Resistance and Extended Spectrum Beta Lactamase Production in Non-Fermenting Gram-Negative Bacilli in Ethiopia

Background

Emergence of resistance to multiple antimicrobial agents in Non-Fermenting Gram-Negative Bacilli is a major problem to public health, as it limits drug treatment options against infections. The aim of this study was to determine the prevalence of multi-drug resistance and extended spectrum beta lactamase production in Non-Fermenting Gram-Negative Bacilli.

Materials and methods

Different clinical samples were collected and processed following standard procedures. Each sample was then inoculated onto culture media. Identification, drug susceptibility testing, and extended spectrum beta lactamase production of the isolates were carried out by using the VITEK 2 compact system.

Results

Among 996 clinical samples, 135 samples yielded Non-Fermenting Gram-Negative Bacilli of which Pseudomonas and Acinetobacter species were the commonest isolates. The overall drug resistance rates of Non-Fermenting Gram-Negative Bacilli were above 80% against ampicillin (89.6%), cefuroxime axetil (88.9%), nitrofurantoin (85.9%), cefalotin (84.4%), cefoxitin (83.7%), cefazolin (83.0%), and cefuroxime (83.0%). Tobramycin with a resistance rate of 19.3% was the most active antimicrobial agent. Out of 135 isolates, 81.5% were multi-drug resistant of which 13.3% were extensively drug resistant and 10.4% were pandrug resistant. Extended spectrum beta lactamase production was detected in 48.9% of the isolates.

Conclusions

The spectrum of bacterial species isolated was diverse. The isolates demonstrated high level of drug resistance in different classes of antibiotics. The magnitude of multi-drug resistance and the level of extended spectrum beta lactamase production were high. Hence, further studies on multi-drug resistant and extended spectrum beta lactamase producing Non-Fermenting Gram-Negative Bacilli both in the community and in hospital setting are essential.

Prevalence of Extended Spectrum Betalactamase (ESBL) and Metallobetalactamase (MBL) Producing Pseudomonas aeruginosa and Acinetobacter baumannii Isolated from Various Clinical Samples

This study was conducted with an objective to find the prevalence of extended spectrum betalactamase (ESBL) and metallobetalactamase (MBL) in P. aeruginosa and A. baumannii isolates obtained from various clinical samples. It was conducted in the Department of Microbiology, Adesh Institute of Medical Sciences and Research, Bathinda, over a period of two years from July 2014 to June 2016. Clinical specimens including urine, pus, blood, high vaginal swabs, respiratory samples, and various body fluids were processed and P. aeruginosa and A. baumannii isolates were identified by standard protocols. Antibiotic sensitivity testing for all isolates was done using Kirby-Bauer disc diffusion method. Disc potentiation test was performed to check ESBL and MBL production in these bacteria. Maximum ESBL positive isolates of P. aeruginosa were observed among pus samples and maximum MBL positive isolates were detected in tracheal aspirates. A. baumannii showed maximum positivity for ESBL and MBL production in endotracheal secretions. This study gives an alarming sign towards high prevalence of cephalosporin and carbapenem resistance due to production of extended spectrum betalactamases and metallobetalactamases, respectively. Early detection, stringent antibiotic policies, and compliance towards infection control practices are the best defenses against these organisms.

High prevalence of the PER-1 gene among carbapenem-resistant Acinetobacter baumannii in Riyadh, Saudi Arabia

The prevalence of carbapenem-resistant Acinetobacter baumannii in Saudi Arabia and their resistance genetic mechanisms are yet to be identified. We studied the prevalence and genetic diversity of extended-spectrum beta-lactamase genes, particularly the PER-1 gene, among carbapenem-resistant A. baumannii strains from patients at a tertiary care hospital in Riyadh, Saudi Arabia between 2006 and 2014. Fresh subcultured samples were tested for antimicrobial susceptibility minimum inhibitory concentration (MIC). Total genomic DNA was extracted from each isolate and further used for polymerase chain reaction (PCR) genotyping, sequence-based typing (SBT) of PER-1 and OXA-51-like gene, and multilocus sequence typing (MLST) of positive isolates. Randomly selected clinical isolates (n = 100) were subjected to MLST. A total of 503 isolates were characterized as multidrug-resistant (MDR) using the MIC. Isolates were further PCR tested for bla _-TEM and bla _-PER-1 resistance genes (n = 503). The genotyping results showed that 68/503 (14 %) isolates were positive to bla TEM. The genotyping results of PER-1-like genes showed that 384/503 (76.3 %) were positive among MDR Acinetobacter isolates. Based on SBT, the majority of these isolates were clustered into three main groups including isolates harboring PER-1: AB11 (bla _-PER-1), isolate AB16 (bla _-PER-1), and, finally, the plasmid pAB154 (bla _-PER-7). Remarkably, many isolates were concealing the PER-1 gene and harboring the TEM resistance genes as well. MLST results for selected isolates (n = 100) identified four main sequence types (STs: 2, 19, 20, and 25) and four novel isolates (ST 486-489). We report 76.3 % prevalence of the PER-1 resistance gene among Acinetobacter clinical isolates from Riyadh, Saudi Arabia. Further work is needed to explore the clinical risks and patient outcome with such resistance related to healthcare-associated infections and investigate the genetic and molecular mechanisms that confer the MDR phenotype.

Susceptibility Pattern and Distribution of Oxacillinases and bla PER-1 Genes among Multidrug Resistant Acinetobacter baumannii in a Teaching Hospital in Iran

Acinetobacter baumannii (A. baumannii) is an important nosocomial pathogen in healthcare institutions. β-Lactamase-mediated resistance is the most common mechanism for carbapenem resistance in A. baumannii. The aim of this study was to determine the antibiotic resistance pattern, to detect OXA encoding genes, class A, bla_PER-1, and to detect the presence of ISAba1. A total of 124 A. baumannii isolates were collected from hospitalized patients in a teaching hospital in Kashan, Iran. The susceptibility of isolates to different antibiotics was determined by disk-diffusion method. PCR was used to detect bla_PER-1, bla_OXA-23, bla_OXA-24, bla_OXA-51, bla_OXA-58, and ISAba1 genes. All isolates were resistant to ceftazidime, ceftriaxone, and cefotaxime. All of the isolates revealed susceptibility to polymyxin B and colistin. Ninety-six percent of the isolates were extensive drug resistance (XDR), 5.6% extended spectrum beta-lactamase (ESBL), and 54.8% metallo-beta-lactamase (MBL). All isolates were positive for bla_OXA-51 and ISAba1. bla_OXA-23,  bla_OXA-24, and bla_OXA-58 were found in 79.8%, 25%, and 3.2%, respectively. The frequency rate of bla_PER-1 gene was 52.4%. Multidrug resistant A. baumannii isolates are increasing in our setting and extensively limit therapeutic options. The high rate presence of class D carbapenemase-encoding genes, mainly bla_OXA-23 carbapenemases, is worrying and alarming as an emerging threat in our hospital.

Pseudomonas aeruginosa: arsenal of resistance mechanisms, decades of changing resistance profiles, and future antimicrobial therapies

Antimicrobial resistance is one of the most serious public health issues facing humans since the discovery of antimicrobial agents. The frequent, prolonged, and uncontrolled use of antimicrobial agents are major factors in the emergence of antimicrobial-resistant bacterial strains, including multidrug-resistant variants. Pseudomonas aeruginosa is a leading cause of nosocomial infections. The abundant data on the increased resistance to antipseudomonal agents support the need for global action. There is a paucity of new classes of antibiotics active against P. aeruginosa. Here, we discuss recent antibacterial resistance profiles and mechanisms of resistance by P. aeruginosa. We also review future potential methods for controlling antibiotic-resistant bacteria, such as phage therapy, nanotechnology and antipseudomonal vaccines.

Antibiotic resistance and extended spectrum beta-lactamases: Types, epidemiology and treatment

Antibiotic resistance is a problem of deep scientific concern both in hospital and community settings. Rapid detection in clinical laboratories is essential for the judicious recognition of antimicrobial resistant organisms. Production of extended-spectrum β-lactamases (ESBLs) is a significant resistance-mechanism that impedes the antimicrobial treatment of infections caused by Enterobacteriaceae and is a serious threat to the currently available antibiotic armory. ESBLs are classified into several groups according to their amino acid sequence homology. Proper infection control practices and barriers are essential to prevent spread and outbreaks of ESBL producing bacteria. As bacteria have developed different strategies to counter the effects of antibiotics, the identification of the resistance mechanism may help in the discovery and design of new antimicrobial agents. The carbapenems are widely regarded as the drugs of choice for the treatment of severe infections caused by ESBL-producing Enterobacteriaceae, although comparative clinical trials are scarce. Hence, more expeditious diagnostic testing of ESBL-producing bacteria and the feasible modification of guidelines for community-onset bacteremia associated with different infections are prescribed.

Acinetobacter baumannii displays inverse relationship between meropenem resistance and biofilm production

In this study the ability for biofilm production among meropenem (MEM)-resistant and -susceptible Acinetobacter baumannii isolates was verified. MEM susceptibility and biofilm production were screened in 116 isolates. Meropenem-resistant A. baumannii isolates showed a reduced ability to produce biofilms compared to those susceptible to MEM (P<0.0001). The results suggest an inverse relationship between biofilm production and MEM resistance in nosocomial A. baumanni isolates.

Global spread of drug-resistant Acinetobacter baumannii: molecular epidemiology and management of antimicrobial resistance

Acinetobacter baumannii is an opportunistic Gram-negative pathogen with increasing relevance in a variety of hospital-acquired infections especially among intensive care unit patients. Resistance to antimicrobial agents is the main reason for A. baumannii spread. A. baumannii outbreaks described worldwide are caused by a limited number of genotypic clusters of multidrug-resistant strains that successfully spread among hospitals of different cities and countries. In this article, we will focus on the mechanisms responsible for resistance to antimicrobials and disinfectants in A. baumannii and the epidemiology of drug-resistant A. baumannii in healthcare facilities. We will also discuss the therapeutic and infection control strategies for management of drug-resistant A. baumannii epidemics.

Multidrug-resistant Acinetobacter baumannii: mechanisms of virulence and resistance

Infection due to Acinetobacter baumannii has become a significant challenge to modern healthcare systems. The organism shows a formidable capacity to develop antimicrobial resistance, yet the clinical impact of A. baumannii infection remains unclear. Much is known about the processes involved in multidrug resistance, but those underlying the pathogenicity and virulence potential of the organism are only beginning to be elucidated. In this article, we provide an overview of current knowledge, focusing on mechanisms of pathogenesis, the molecular basis of resistance and options for treatment in the absence of novel therapeutic agents.

Pseudomonas aeruginosa - a phenomenon of bacterial resistance

Pseudomonas aeruginosa is one of the leading nosocomial pathogens worldwide. Nosocomial infections caused by this organism are often hard to treat because of both the intrinsic resistance of the species (it has constitutive expression of AmpC beta-lactamase and efflux pumps, combined with a low permeability of the outer membrane), and its remarkable ability to acquire further resistance mechanisms to multiple groups of antimicrobial agents, including beta-lactams, aminoglycosides and fluoroquinolones. P. aeruginosa represents a phenomenon of bacterial resistance, since practically all known mechanisms of antimicrobial resistance can be seen in it: derepression of chromosomal AmpC cephalosporinase; production of plasmid or integron-mediated beta-lactamases from different molecular classes (carbenicillinases and extended-spectrum beta-lactamases belonging to class A, class D oxacillinases and class B carbapenem-hydrolysing enzymes); diminished outer membrane permeability (loss of OprD proteins); overexpression of active efflux systems with wide substrate profiles; synthesis of aminoglycoside-modifying enzymes (phosphoryltransferases, acetyltransferases and adenylyltransferases); and structural alterations of topoisomerases II and IV determining quinolone resistance. Worryingly, these mechanisms are often present simultaneously, thereby conferring multiresistant phenotypes. This review describes the known resistance mechanisms in P. aeruginosa to the most frequently administrated antipseudomonal antibiotics: beta-lactams, aminoglycosides and fluoroquinolones.

Effects of combined treatment with sansanmycin and macrolides on Pseudomonas aeruginosa and formation of biofilm

OBJECTIVE

To observe the effects of combined treatment with sansanmycin and macrolides on Pseudomonas aeruginosa and formation of biofilm.

METHODS

Micro-dilution method was used to determine the minimal inhibitory concentrations (MICs) of sansanmycin, gentamycin, carbenicillin, polymyxin B, roxithromycin, piperacillin, and tazobactam. PA1 and PA27853 biofilms were observed under optical microscope after staining and under SEM after treatment with sansanmycin at different dosages and combined treatment with sansanmycin and roxithromycin. Viable bacteria in PA1 and PA27853 biofilms were counted after treatment with sansanmycin at different dosages or combined treatment with sansanmycin and roxithromycin.

RESULTS

The MIC of sansanmycin was lower than that of gentamycin and polymyxin B, but was higher than that of carbenicillin. Roxithromycin enhanced the penetration of sansanmycin to PA1 and PA27853 strains through biofilms. PA1 and PA27853 biofilms were gradually cleared with the increased dosages of sansanmycin or with the combined sansanmycin and roxithromycin.

CONCLUSION

Sub-MIC levels of roxithromycin and sansanmycin substantially inhibit the generation of biofilms and proliferation of bacteria. Therefore, combined antibiotics can be used in treatment of intractable bacterial infection.

Febrile neutropenia

This review summarizes the current status and diagnostic-therapeutic challenges in febrile neutropenia. Patients with neutropenia-associated infections have a poor prognosis. A large meta-analysis of trials assessing prophylactic antibiotics has shown significant survival benefits; clinical significance of resistance is unclear. Administering broad-spectrum antibiotics to established febrile neutropenic patients has become selective, vancomycin is withheld unless absolutely necessary, and low-risk patients are identified with biological markers. Such patients are now managed with oral antibiotics at home or even without antibiotics. Protracted prolonged neutropenia is the setting par excellence for invasive fungal infections. Conventional amphotericin B administered to such risk patients reduces the incidence of fungal infections. New antifungal drugs have heightened efficacy and lowered toxicity. Novel antifungal diagnostic tests include imaging, particularly the CT "halo" sign (aspergillosis), and serology (glucan, galactomannan), and provide earlier diagnosis and treatment and better outcomes. Negative tests may indicate withholding antifungal therapy. High intermittent dosing of liposomal amphotericin B seems as safe and as effective as standard dosing regimens, but at half the drug acquisition cost. The use of nonantibiotic agents has offered alternative management strategies. Recombinant interleukin-11 reduces bacteremia, through a cytoprotective mechanism on the gut. rhIL-11 releases C-reactive protein and causes shedding of soluble TNF receptor-1, modulating the immunological milieu and the systemic inflammatory response. Other candidate molecules include RANTES and long-pentraxin 3. Recombinant growth factors reduce febrile episodes, permitting completion of chemotherapy, increase overall survival, and minimize infection mortality.

Imported PER-1 producing Pseudomonas aeruginosa, PER-1 producing Acinetobacter baumanii and VIM-2-producing Pseudomonas aeruginosa strains in Hungary

Introduction

Pseudomonas aeruginosa and Acinetobacter baumanii are important nosocomial pathogens with wide intrinsic resistance. However, due to the dissemination of the acquired resistance mechanisms, such as extended-spectrum beta-lactamase (ESBL) and metallo beta-lactamase (MBL) production, multidrug resistant strains have been isolated more often.

Case presentation

We report a case of a Hungarian tourist, who was initially hospitalized in Egypt and later transferred to Hungary. On the day of admission PER-1-producing P. aeruginosa, PER-1 producing A. baumannii, SHV-5-producing Klebsiella pneumoniae and VIM-2-producing P. aeruginosa isolates were subcultured from the patient's samples in Hungary. Comparing the pulsed-field gel electrophoresis (PFGE) patterns of the P. aeruginosa strains from the patient to the P. aeruginosa strains occurring in this hospital, we can state that the PER-1-producing P. aeruginosa and VIM-2-producing P. aeruginosa had external origin.

Conclusion

This is the first report of PER-1-producing P. aeruginosa,and PER-1-producing A. baumanii strains in Hungary. This case highlights the importance of spreading of the beta-lactamase-mediated resistance mechanisms between countries and continents, showing the importance of careful screening and the isolation of patients arriving from a different country.

Molecular epidemiology of PER-1 extended spectrum beta-lactamase among gram-negative bacteria isolated at a tertiary care hospital

The bla(PER-1) presence was sought by PCR in 289 ceftazidime resistant Gram-negative bacteria isolated at Dokuz Eylul University Hospital (Turkey) between 1998 and 2003. PER-1 production rates were 32.3, 33.9, 14.9 and 37.9% in the 1998-2000 period, 2001, 2002 and 2003, respectively. bla(PER-1) was detected in 46.2 and 35.9% of ceftazidime-resistant Pseudomonas aeruginosa and Acinetobacter baumannii isolates, respectively. ERIC-PCR results revealed that dissemination of two endemic clones for both P. aeruginosa (X and Y) and A. baumannii (A and B) was responsible for the high prevalence. Results of the conjugation tests and plasmid curing experiments suggested that bla(PER-1) was located on the chromosome in the representative strains. It was also shown for the first time that bla(PER-1) in a clinical isolate was associated with class-1 integron which could facilitate dissemination of bla(PER-1) among bacteria.

Outbreak of Pseudomonas aeruginosa infections with PER-1 extended-spectrum beta-lactamase in Warsaw, Poland: further evidence for an international clonal complex

Forty-one Pseudomonas aeruginosa isolates with extended-spectrum beta-lactamases (ESBLs) from a hospital in Warsaw, Poland, were analyzed. Thirty-seven isolates from several wards were collected over 9 months in 2003 and 2004. The isolates were recovered from patients with multiple types of infections, mostly respiratory tract and postoperative wound infections. All 41 isolates produced the PER-1 ESBL, originally observed in Turkey but recently also identified in several countries in Europe and the Far East. The bla(PER-1) gene resided within the Tn1213 composite transposon, which was chromosomally located. Pulsed-field gel electrophoresis and multilocus sequence typing (MLST) revealed the presence of three separate clones among the isolates. Two of these, corresponding to sequence types (STs) ST244 and ST235, were responsible for parallel outbreaks. Apart from PER-1, all the isolates produced OXA-2 oxacillinase. ST235 isolates additionally expressed a novel enzyme, OXA-74, differing by one amino acid from the OXA-17 ESBL identified originally in PER-1- and OXA-2-positive P. aeruginosa isolates from Ankara, Turkey, in 1992. These earlier Ankara isolates with PER-1, OXA-2, and OXA-17 were also classified into ST235, which is a single-locus variant of two other STs, ST227 and ST230. ST227, ST230, and ST235 all correspond to the recently described clonal complex BG11, which seems to be internationally distributed, having spread in Turkey, Greece, Italy, Hungary, Poland, Sweden, and much of Russia. It is associated with various beta-lactamases, including PER-1 and VIM metalloenzymes. This work further demonstrates the value of MLST of P. aeruginosa.

Biochemical characterization of PER-2 and genetic environment of blaPER-2

PER-2 was the first detected and the second most prevalent extended-spectrum beta-lactamase in clinical pathogens isolated in Argentina and was also reported only in other South American countries. Citrobacter freundii 33587 was isolated in 1999 in Buenos Aires and was resistant to all tested beta-lactams except cephamycins and carbapenems. The strain produced both plasmid-borne TEM-1 and PER-2 (pI 5.4), which could be transferred by conjugation. By PCR screening, thermal asymmetric interlaced PCR, and DNA sequencing, we detected an ISPa12/IS1387a insertion sequence upstream of bla(PER-2), previously reported as also being associated with bla(PER-1). The presence of similar structures upstream of bla(PER-1) and bla(PER-2) suggests a common origin and mobilization. Compared to bla(PER-1) genes, an additional putative promoter for bla(PER-2) was found. PER-2 kinetic analysis showed its high hydrolysis efficiencies toward both CTX and CAZ (k(cat)/K(m), 0.76 and 0.43 microM(-1).s(-1), respectively).

Occurrence of PER-1 producing clinical isolates of Pseudomonas aeruginosa in Japan and their susceptibility to doripenem

The acquisition of resistance by extended-spectrum beta-lactamases (ESBL) has been reported primarily for Enterobacteriaceae, but there are few reports on the isolation of ESBL-producing Pseudomonas aeruginosa. PER-1-type ESBL producing P aeruginosa has been found in various regions around the world but there are no reports of clinical isolates in Japan. During our susceptibility surveillance studies over a 10 year period, we found four clinical isolates resistant to ceftazidime due to production of PER-1. They were resistant to ceftazidime but susceptible in the presence of clavulanic acid, a class A beta-lactamase inhibitor. The strains had the ability to hydrolyze ceftazidime. They also had the gene for PER-1-type ESBL. This is the first report of the isolation of PER-1 producing strains in Japan. These four strains were resistant to ceftazidime, cefepime and aztreonam with MICs of 64 microg/ml or more, but were more susceptible to carbapenem antibiotics. In particular, doripenem, which is a novel carbapenem antibiotic, showed good antibacterial activity with a MIC of 2 or 4 microg/ml, which was more potent than meropenem and imipenem. Doripenem also showed good therapeutic efficacy against a systemic infection of mice with a PER-1 producing strain, and was also more potent in vivo than imipenem or meropenem.

Distinct antimicrobial resistance patterns and antimicrobial resistance-harboring genes according to genomic species of Acinetobacter isolates

Using 58 isolates of Acinetobacter species recovered from a university hospital between August 2004 and March 2005, we performed genomic identification by amplified rRNA gene restriction analysis (ARDRA) and investigated the existence of metallo-beta-lactamase (MBL) producers and extended-spectrum beta-lactamase (ESBL) producers. Genomic species identification of Acinetobacter strains using ARDRA showed that 40 strains were genomic species 2 (Acinetobacter baumannii), 9 were 13 sensu Tjernberg and Ursing (13TU), 5 were Acinetobacter phenon 6/ct 13TU, and 4 were Acinetobacter genospecies 3. Among 58 strains, 13 isolates were MBL producers carrying bla(IMP-1) or bla(VIM-2) and 13 isolates were ESBL producers carrying bla(PER-1). Notably, the MBL producers were mostly 13TU, Acinetobacter phenon 6/ct 13TU, and Acinetobacter genospecies 3, which showed susceptibility to ciprofloxacin and ampicillin-sulbactam. However, 12 of 13 strains carrying bla(PER-1) were A. baumannii, showing multidrug resistance. The data revealed that the antimicrobial resistance patterns and resistance-harboring genes of Acinetobacter species are remarkably distinct according to the genomic species of Acinetobacter isolates.

Attributable mortality of Acinetobacter baumannii infections in critically ill patients: a systematic review of matched cohort and case-control studies

INTRODUCTION

There has been a continuing controversy about whether infection with Acinetobacter baumannii increases morbidity and mortality independently of the effect of other confounding factors.

METHODS

We performed a systematic review of matched case-control and cohort studies examining the mortality attributable to infection with or acquisition of A. baumannii (infection or colonization). We included in our review studies that compared mortality and/or morbidity of patients with acquisition of or infection with A. baumannii (cases) with the outcomes of matched patients without A. baumannii isolation from clinical specimens (controls). The relevant studies were identified from searches of the PubMed and the Cochrane Library databases. Two independent reviewers performed the literature search, study selection, and data extraction from nine identified relevant studies.

RESULTS

The attributable mortalities, in the hospital and in the intensive care unit, of patients with A. baumannii infection in six matched case-control studies included in our review ranged from 7.8% to 23% and from 10% to 43%, respectively. In addition, a statistically significantly higher mortality was reported for patients with A. baumannii acquisition; that is, colonization or infection (cases) compared with controls without such an acquisition in all four reviewed studies that reported data on this comparison.

CONCLUSION

Although definitive statements about the mortality attributable to the acquisition of A. baumannii cannot be made from the available studies because of their methodological heterogeneity, the reviewed data suggest that infection with or acquisition of A. baumannii seems to be associated with increased mortality.

Genetic analysis of a multiresistant strain of Pseudomonas aeruginosa producing PER-1 beta-lactamase

A multiresistant strain of Pseudomonas aeruginosa, PA2345, belonging to serotype O:1, was isolated at the Teaching Hospital of Besançon, France. Resistance to beta-lactams, including third-generation cephalosporins, depended upon a chromosomally-located composite transposon carrying the bla(PER-1) gene encoding extended-spectrum beta-lactamase PER-1. PA2345 was unrelated genotypically to two previous PER-1-producing isolates of P. aeruginosa. Sequence analysis of the transposon in PA2345 revealed the presence of two insertion sequences (ISPa23 and ISPa24) with very different predicted transposases (TnpA1, TnpA2), which were both bordered by closely related 16-bp inverted repeats. High resistance of PA2345 to aminoglycosides was caused, in part, by a chromosomal class-I integron containing gene cassettes aadB, encoding an ANT(2'') enzyme, and aadA11, encoding a new ANT(3'') enzyme with 281 amino-acids that conferred elevated resistance to streptomycin and spectinomycin. Stable overproduction of efflux system MexXY contributed to resistance to amikacin, while mutations in the quinolone resistance-determining regions of gyrA and parC accounted for the high resistance of PA2345 to fluoroquinolones. The study indicates that multidrug resistance in P. aeruginosa might arise from sequential acquisition of a variety of mechanisms provided by both horizontal gene transfers and mutations in chromosomal genes.

Pseudomonas aeruginosa bloodstream infections: risk factors and treatment outcome related to expression of the PER-1 extended-spectrum beta-lactamase

BACKGROUND

Bloodstream infection (BSI) due to Pseudomonas aeruginosa (Pa) has relevant clinical impact especially in relation to drug resistance determinants. The PER-1 extended-spectrum beta-lactamase (ESBL) is a common enzyme conferring high-level resistance to anti-pseudomonal cephalosporins. Risk factors and treatment outcome of BSI episodes caused by PER-1-positive Pa (PER-1-Pa) strains were compared to those caused by ESBL-negative Pa isolates (ESBL-N-Pa).

METHODS

Twenty-six BSI cases due to ceftazidime-resistant Pa strains have been investigated. MIC values of anti-pseudomonal drugs were determined by the Etest method (AB Biodisk, Solna, Sweden). The double-disk synergy test was used to detect ESBL production. PCR amplification and DNA sequencing were used to characterize ESBL types. Clinical records of BSI-patients were examined retrospectively. Demographic data, underlying diseases (McCabe-Jackson classification and Charlson weighted index), risk factors, antimicrobial therapy, and treatment outcome were evaluated in cases due to ESBL-positive and cases due to ESBL-N-Pa isolates. Unpaired Student's t-test, Mann-Whitney U-test, Fisher's exact test and the chi2 test were used for statistical analysis.

RESULTS

Nine Pa isolates expressed the PER-1 ESBL; the remaining 17 isolates did not produce ESBLs. Severe sepsis (P = 0.03), bladder and intravascular catheters (both P = 0.01), immunosuppressive therapy (P = 0.04), and mechanical ventilation (P = 0.03) were significantly associated with BSI due to PER-1-Pa. Empirical treatment (P = 0.02) and treatment after ID/AST (P < 0.01) were rarely adequate in PER-1-Pa cases. With regard to treatment outcome, 77.8% BSI cases due to PER-1-Pa vs. 28.6% cases due to ESBL-N-Pa isolates failed to respond (P < 0.03). All cases due to PER-1-Pa that were treated with carbapenems (alone or in combination with amikacin) failed to respond. In contrast, 7/8 cases due to ESBL-N-Pa given carbapenems were responders.

CONCLUSION

Therapeutic failure and increased hospital costs are associated with BSI episodes caused by PER-1-Pa strains. Thus, recognition and prompt reporting of ESBL-production appears a critical factor for the management of patients with serious P. aeruginosa infections.

Detection and genotyping of SHV beta-lactamase variants by mass spectrometry after base-specific cleavage of in vitro-generated RNA transcripts

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) after base-specific cleavage of PCR-amplified and in vitro-transcribed bla(SHV) genes was used for the identification and genotyping of SHV beta-lactamases. For evaluation, bla(SHV) stretches of 21 clinical Enterobacteriaceae isolates were PCR amplified using T7 promoter-tagged forward and reverse primers, respectively. In vitro transcripts were generated with T7 RNA and DNA polymerase in the presence of modified analogues replacing either CTP or UTP. Using RNase A, the in vitro transcripts were base-specifically cleaved at every "T" or "C" position. Resulting cleavage products were analyzed by MALDI-TOF MS, generating a characteristic signal pattern based on the fragment masses. All 21 individual SHV genes were identified unambiguously using reference sequences, and the results were in perfect concordance with those obtained by fluorescent dideoxy sequencing, which represents the current standard method. As multiple point mutations can be detected in a single assay and newly emerged mutations which are not yet described in public databases can be identified too, MALDI-TOF MS appears to be an ideal tool for analysis of sequence polymorphisms in resistance-associated gene loci.

Extended-spectrum beta-lactamases: a clinical update

Extended-spectrum beta-lactamases (ESBLs) are a rapidly evolving group of beta-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these beta-lactamases. This extends the spectrum of beta-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

PER-1 is still widespread in Turkish hospitals among Pseudomonas aeruginosa and Acinetobacter spp

PER-1 type beta-lactamases were screened among ceftazidime-resistant clinical isolates of Acinetobacter spp. and Pseudomonas aeruginosa. A total of 176 non-repetitive isolates (84 Acinetobacter spp. and 92 P. aeruginosa) were collected during a three month surveillance period. Isolates were obtained from seven intensive care units of seven university hospitals. All strains were screened for bla(PER-1) alleles by PCR. Of the strains, 31% and 55.4% of Acinetobacter spp. and P. aeruginosa were positive for bla(PER-1) type genes, respectively.

Tn5393d, a complex Tn5393 derivative carrying the PER-1 extended-spectrum beta-lactamase gene and other resistance determinants

In Alcaligenes faecalis FL-424/98, a clinical isolate that produces the PER-1 extended-spectrum beta-lactamase, the bla(PER-1) gene was found to be carried on a 44-kb nonconjugative plasmid, named pFL424, that was transferred to Escherichia coli by electroporation. Investigation of the genetic context of the bla(PER-1) gene in pFL424 by means of a combined cloning and PCR mapping approach revealed that the gene is associated with a transposonlike element of the Tn3 family. This 14-kb element is a Tn5393 derivative of original structure, named Tn5393d, which contains the transposition module and the strAB genes typical of other members of the Tn5393 lineage plus additional resistance determinants, including the bla(PER-1) gene and a new allelic variant of the aphA6 aminoglycoside phosphotransferase gene, named aphA6b, whose product is active against kanamycin, streptomycin, and amikacin. Tn5393d apparently originated from the consecutive insertion of two composite transposons into a Tn5393 backbone carrying the aphA6b and the bla(PER-1) genes, respectively. The putative composite transposon carrying bla(PER-1), named Tn4176, is made of two original and nonidentical insertion sequences of the IS4 family, named IS1387a and IS1387b, of which one is interrupted by the insertion of an original insertion sequence of the IS30 family, named IS1066. In pFL424, Tn5393d is inserted into a Tn501-like mercury resistance transposon. Transposition of Tn5393d or modules thereof containing the bla(PER-1) gene from pFL424 to small multicopy plasmids or to a bacterial artificial chromosome was not detected in an E. coli host harboring both replicons.

Infections in Patients with Febrile Neutropenia: Epidemiology, Microbiology, and Risk Stratification

Determinations of the type and setting of empirical therapy for immunocompromised patients with fever are complicated by the characteristics of the underlying illness and the effects of treatments already received, as well as by changing microbiological patterns and trends in drug resistance at national and institutional levels. Several systems have been proposed to distinguish patients who could benefit from outpatient antibiotic therapy from patients who require hospitalization. Practical considerations may decide whether the necessary monitoring during the period of neutropenia can be achieved.

Antimicrobial resistance of Acinetobacter spp. in Europe

Bacteria of the genus Acinetobacter are ubiquitous in nature. These organisms were invariably susceptible to many antibiotics in the 1970s. Since that time, acinetobacters have emerged as multiresistant opportunistic nosocomial pathogens. The taxonomy of the genus Acinetobacter underwent extensive revision in the mid-1980s, and at least 32 named and unnamed species have now been described. Of these, Acinetobacter baumannii and the closely related unnamed genomic species 3 and 13 sensu Tjernberg and Ursing (13TU) are the most relevant clinically. Multiresistant strains of these species causing bacteraemia, pneumonia, meningitis, urinary tract infections and surgical wound infections have been isolated from hospitalised patients worldwide. This review provides an overview of the antimicrobial susceptibilities of Acinetobacter spp. in Europe, as well as the main mechanisms of antimicrobial resistance, and summarises the remaining treatment options for multiresistant Acinetobacter infections.

Multifocal detection of multidrug-resistant Pseudomonas aeruginosa producing the PER-1 extended-spectrum beta-lactamase in Northern Italy

Forty-four nonreplicate clinical isolates of Pseudomonas aeruginosa that were resistant to extended-spectrum cephalosporins (ceftazidime and cefepime) and aztreonam, that putatively produced an acquired extended- spectrum beta-lactamase (ESBL), according to the results of a double-disk synergy test, and that had been involved in nosocomial outbreaks were obtained from six different hospitals in northern Italy and screened for the presence of bla(PER) ESBL determinants. Twenty isolates, associated with nine independent outbreaks that occurred in five hospitals in the Milan area and its surroundings during 1995-2000, were found to carry an acquired bla(PER-1) gene. PER-1 producers representative of the nine outbreaks exhibited a multidrug resistance (MDR) phenotype, including resistance to extended-spectrum cephalosporins, aztreonam, meropenem, aminoglycosides, and in most cases, imipenem and ciprofloxacin. An analysis of macrorestriction profiles of their genomic DNAs by pulsed-field gel electrophoresis revealed an overall clonal diversity of the PER-1 producers, although interhospital clonal spread was also observed. The bla(PER-1) gene was not transferable and appeared to be chromosomally located. An analysis of the EcoRI and EcoRV restriction fragment length polymorphisms of the bla(PER-1) locus revealed identical patterns for all isolates, and the characterization of a 1.9-kb region containing bla(PER-1) revealed a conserved structure in representatives of the various clonal lineages. The present findings indicate that MDR P. aeruginosa clones producing the PER-1 ESBL are endemic to this area of northern Italy, where they have been circulating since the mid-1990s and have been associated with several nosocomial outbreaks.

Multidrug-resistant Acinetobacter infections: an emerging challenge to clinicians

OBJECTIVE

To review and evaluate clinically relevant epidemiology, microbiology, and clinical studies regarding the treatment of multidrug-resistant Acinetobacter infections.

DATA SOURCES

Pertinent literature was identified by a MEDLINE search (1966-September 2003) and through secondary bibliographies of pertinent articles.

STUDY SELECTION AND DATA EXTRACTION

All English-language articles identified from data sources were evaluated for clinical relevance.

DATA SYNTHESIS

Acinetobacter baumannii has emerged as a worldwide problem as a nosocomial pathogen in hospitalized patients. Acinetobacter spp. can cause a multitude of infections including pneumonia, bacteremia, meningitis, urinary tract infections, and skin and soft tissue infections, and the mortality associated with these infections is high. Isolates resistant to almost all commercially available antimicrobials have been identified, thus limiting treatment options. The development of new agents and reappraisal of older compounds (ie, polymyxins, ampicillin/sulbactam) are necessary as we consider the optimal treatment of these multidrug-resistant organisms.

CONCLUSIONS

There is no simple answer to the treatment of Acinetobacter infections. Eradication of Acinetobacter spp. requires adherence to good infection control practices and prudent antibiotic use, as well as effective antimicrobial therapy. Alternative therapies such as colistin, ampicillin/sulbactam, and tetracycline are potential options, but prospective, randomized, controlled trials are still lacking.

Extended-spectrum beta-lactamases in Klebsiella pneumoniae bloodstream isolates from seven countries: dominance and widespread prevalence of SHV- and CTX-M-type beta-lactamases

A huge variety of extended-spectrum beta-lactamases (ESBLs) have been detected during the last 20 years. The majority of these have been of the TEM or SHV lineage. We have assessed ESBLs occurring among a collection of 455 bloodstream isolates of Klebsiella pneumoniae, collected from 12 hospitals in seven countries. Multiple beta-lactamases were produced by isolates with phenotypic evidence of ESBL production (mean of 2.7 beta-lactamases per isolate; range, 1 to 5). SHV-type ESBLs were the most common ESBL, occurring in 67.1% (49 of 73) of isolates with phenotypic evidence of ESBL production. In contrast, TEM-type ESBLs (TEM-10 type, -12 type, -26 type, and -63 type) were found in just 16.4% (12 of 73) of isolates. The finding of TEM-10 type and TEM-12 type represents the first detection of a TEM-type ESBL in South America. PER (for Pseudomonas extended resistance)-type beta-lactamases were detected in five of the nine isolates from Turkey and were found with SHV-2-type and SHV-5-type ESBLs in two of the isolates. CTX-M-type ESBLs (bla(CTX-M-2) type and bla(CTX-M-3) type) were found in 23.3% (17 of 73) of isolates and were found in all study countries except for the United States. We also detected CTX-M-type ESBLs in four countries where they have previously not been described-Australia, Belgium, Turkey, and South Africa. The widespread emergence and proliferation of CTX-M-type ESBLs is particularly noteworthy and may have important implications for clinical microbiology laboratories and for physicians treating patients with serious K. pneumoniae infections.

Outbreak of extended-spectrum beta-lactamase VEB-1-producing isolates of Acinetobacter baumannii in a French hospital

Twelve clonally related and multidrug-resistant Acinetobacter baumannii isolates were recovered during a 4-month period from 12 patients hospitalized at the Valenciennes Hospital in France. Antibiograms determined by the double-disk diffusion technique on cloxacillin-containing plates detected a clavulanic acid-inhibited extended-spectrum beta-lactamase (ESBL). PCR and sequencing identified the gene encoding the Ambler class A ESBL VEB-1. This gene was located on the chromosome and was part of a class 1 integron identical to that previously identified in Pseudomonas aeruginosa isolates from Thailand. Additionally, seven clonally related bla(VEB-1)-positive A. baumannii strains were identified in the immediate environment of the hospitalized patients. This is the first report of the ESBL VEB-1 in Acinetobacter spp. and the first description of VEB-1-producing strains as a source of an outbreak occurring outside Southeast Asia. This report underlines the difficulty of the identification of ESBLs in A. baumannii.

Occurrence of extended-spectrum beta-lactamases among Escherichia coli isolates from hospitalized and healthy children

The prevalence of extended-spectrum beta-lactamases (ESBL) was determined among isolates of Escherichia coli (n = 63) isolated from hospitalized (43) and healthy (20) children. Ten isolates (21%) were ESBL-positive for two screening tests, the double disk-synergy test and the Oxoid Combination Disk method. One ESBL-positive isolate came from a healthy child. The transfer frequency of oxyimino-beta-lactam resistance from ESBL-producing isolates to E. coli K12 C600 recipient strain ranged from 10(-8) to 10(-5) per donor cell. Donor strains and transconjugants displayed susceptibility patterns typical of ESBL producers. They were resistant to oxyimino-beta-lactams but susceptible to clavulanic acid and carbapenems. Seven out of the 10 ESBL-positive isolates were found to produce MR/MS fimbria, which may play an important role in the colonization of the human intestinal mucosa.

High prevalence of PER-1 extended-spectrum beta-lactamase-producing Acinetobacter spp. in Korea

PER-1, an extended-spectrum beta-lactamase, has been reported only in Europe. We detected PER-1 in 53 of 97 acinetobacters in Korea, mainly in the sputum of intensive care unit patients. Pulsed-field gel electrophoresis analysis suggested that clonal spread had occurred. Only PCR reliably detected PER-1 producers. PER-1 producers may also exist in other Asian countries.

Treatment of febrile neutropenia: what is new?

PURPOSE OF THE REVIEW

To identify the more recent challenges in the treatment of patients with febrile neutropenia following antineoplastic chemotherapy or bone marrow transplant published in the English language in the period late 2000-early 2002 regarding: changes in etiology of bacteremia in neutropenic patients; new options for initial empirical antibacterial therapy; factors associated with the risk of developing infection in cancer patients; prediction of prognosis in febrile neutropenia; oral therapy; need for a specific anti-Gram-positive coverage in persistently febrile and neutropenic patients.

RECENT FINDINGS

Findings may be summarized according with the identified topics as follows: many centers are reporting an increase in the incidence of Gram-negative bacteremias; piperacillin-tazobactam could be safely administered as monotherapy of febrile neutropenia; congenital factors and intensity of chemotherapy and other medical interventions, such as antifungal prophylaxis, are recognized as of increasing importance in the determination of infectious risk; it is now possible to identify patients with a good prognosis (low risk) by means of validated scoring systems; oral therapy is feasible in low risk patients; the empirical addition of a glycopeptide in persistently febrile neutropenic patients is not indicated.

SUMMARY

Many of the identified points may have a great impact in the daily management of febrile granulocytopenic patients. However, all recent epidemiological and therapeutical studies underline the absoloute need for the knowledge of the pattern of infecting organisms in each center.