Fourteen years in resistance

β-lactam and β-lactamase inhibitor combinations in the treatment of extended-spectrum β-lactamase producing Enterobacteriaceae: time for a reappraisal in the era of few antibiotic options?

The spread of extended-spectrum β-lactamase (ESBL) genes in Enterobacteriaceae such as Escherichia coli or Klebsiella spp is a major challenge to modern medical practice. Carbapenems are the treatment of choice for serious infections caused by ESBL producers; however, carbapenem resistance has increased globally. ESBL producers might be susceptible to β-lactam-β-lactamase inhibitor (BLBLI) combination antibiotics such piperacillin-tazobactam or amoxicillin-clavulanate. These drugs are frequently avoided in serious infections caused by ESBL producers because of the inoculum effect in-vitro (especially for piperacillin-tazobactam), animal data suggesting inferior efficacy when compared with carbapenems, concerns about pharmacokinetic-pharmacodynamic drug target attainment with standard doses, and poor outcomes shown in some observational studies. Prospective cohort data and a meta-analysis suggest that BLBLIs are non-inferior to carbapenems in the treatment of bloodstream infections caused by ESBL producers. We examine why BLBLIs are perceived as inferior in the treatment of infection with ESBL producers, and discuss data that suggest these concerns might not be strongly supported by clinical evidence.

Homogeneity of antimicrobial policy, yet heterogeneity of antimicrobial resistance: antimicrobial non-susceptibility among 108,717 clinical isolates from primary, secondary and tertiary care patients in London

OBJECTIVES

We examined the 4 year trend in antimicrobial susceptibilities and prescribing across levels of care at two London teaching hospitals and their multisite renal unit, and for the surrounding community.

METHODS

Laboratory and pharmacy information management systems were interrogated, with antimicrobial use and susceptibilities analysed between hospitals, within hospitals and over time.

RESULTS

A total of 108,717 isolates from 71,687 patients were identified, with significant differences (at P < 0.05) in antimicrobial susceptibility between and within hospitals. Across the 4 years, rates of ESBL-/AmpC-producing Enterobacteriaceae ranged from 6.4% to 10.7% among community isolates, 17.8% to 26.9% at ward level and 25.2% to 52.5% in critical care. Significant variations were also demonstrated in glycopeptide-resistant enterococci (ward level 6.2%-17.4%; critical care 21.9%-56.3%), MRSA (ward level 18.5%-38.2%; critical care 12.5%-47.9%) and carbapenem-resistant Pseudomonas spp. (ward level 8.3%-16.9%; critical care 19.9%-53.7%). Few instances of persistently higher resistance were seen between the hospitals in equivalent cohorts, despite persistently higher antimicrobial use in Hospital 1 than Hospital 2. We found significant fluctuations in non-susceptibility year on year across the cohorts, but with few persistent trends.

CONCLUSIONS

The marked heterogeneity of antimicrobial susceptibilities between hospitals, within hospitals and over time demands detailed, standardized surveillance and appropriate benchmarking to identify possible drivers and effective interventions. Homogeneous antimicrobial policies are unlikely to continue to be suitable as individual hospitals join hospital networks, and policies should be tailored to local resistance rates, at least at the hospital level, and possibly with finer resolution, particularly for critical care.

Genome Sequence of a Multidrug-Resistant Strain of Klebsiella pneumoniae, BAMC 07-18, Isolated from a Combat Injury Wound

Klebsiella pneumoniae is an important infectious agent of surgical sites and combat wounds. Antibiotic resistance and tolerance are common impediments to the healing of chronic infections. Here, we report the genome sequence of a highly multidrug-resistant strain of K. pneumoniae, BAMC 07-18, isolated from a combat wound of a soldier.

Structural variations of the cell wall precursor lipid II and their influence on binding and activity of the lipoglycopeptide antibiotic oritavancin

Oritavancin is a semisynthetic derivative of the glycopeptide antibiotic chloroeremomycin with activity against Gram-positive pathogens, including vancomycin-resistant staphylococci and enterococci. Compared to vancomycin, oritavancin is characterized by the presence of two additional residues, a hydrophobic 4'-chlorobiphenyl methyl moiety and a 4-epi-vancosamine substituent, which is also present in chloroeremomycin. Here, we show that oritavancin and its des-N-methylleucyl variant (des-oritavancin) effectively inhibit lipid I- and lipid II-consuming peptidoglycan biosynthesis reactions in vitro. In contrast to that for vancomycin, the binding affinity of oritavancin to the cell wall precursor lipid II appears to involve, in addition to the D-Ala-D-Ala terminus, other species-specific binding sites of the lipid II molecule, i.e., the crossbridge and D-isoglutamine in position 2 of the lipid II stem peptide, both characteristic for a number of Gram-positive pathogens, including staphylococci and enterococci. Using purified lipid II and modified lipid II variants, we studied the impact of these modifications on the binding of oritavancin and compared it to those of vancomycin, chloroeremomycin, and des-oritavancin. Analysis of the binding parameters revealed that additional intramolecular interactions of oritavancin with the peptidoglycan precursor appear to compensate for the loss of a crucial hydrogen bond in vancomycin-resistant strains, resulting in enhanced binding affinity. Augmenting previous findings, we show that amidation of the lipid II stem peptide predominantly accounts for the increased binding of oritavancin to the modified intermediates ending in D-Ala-D-Lac. Corroborating our conclusions, we further provide biochemical evidence for the phenomenon of the antagonistic effects of mecA and vanA resistance determinants in Staphylococcus aureus, thus partially explaining the low frequency of methicillin-resistant S. aureus (MRSA) acquiring high-level vancomycin resistance.

Trends in serotype distribution and antimicrobial susceptibility in Salmonella enterica isolates from humans in Belgium, 2009 to 2013

The Belgian National Reference Centre for Salmonella received 16,544 human isolates of Salmonella enterica between January 2009 and December 2013. Although 377 different serotypes were identified, the landscape is dominated by S. enterica serovars Typhimurium (55%) and Enteritidis (19%) in a ratio which is inverse to European Union averages. With outbreaks of Salmonella serotypes Ohio, Stanley, and Paratyphi B variant Java as prime examples, 20 serotypes displayed significant fluctuations in this 5-year period. Typhoid strains account for 1.2% of Belgian salmonellosis cases. Large-scale antibiotic susceptibility analyses (n = 4,561; panel of 12 antibiotics) showed declining resistance levels in S. Enteritis and Typhimurium isolates for 8 and 3 tested agents, respectively. Despite low overall resistance to ciprofloxacin (4.4%) and cefotaxime (1.6%), we identified clonal lineages of Salmonella serotypes Kentucky and Infantis displaying rising resistance against these clinically important drugs. Quinolone resistance is mainly mediated by serotype-specific mutations in GyrA residues Ser83 and Asp87 (92.2% not wild type), while an additional ParC_Ser80Ile mutation leads to ciprofloxacin resistance in 95.5% S. Kentucky isolates, which exceeds European averages. Plasmid-mediated quinolone resistance (PMQR) alleles qnrA1 (n = 1), qnrS (n = 9), qnrD1 (n = 4), and qnrB (n = 4) were found in only 3.0% of 533 isolates resistant to nalidixic acid. In cefotaxime-resistant isolates, we identified a broad range of Ambler class A and C β-lactamase genes (e.g., bla(SHV-12), blaTEM-52, bla(CTX-M-14), and bla(CTX-M-15)) commonly associated with members of the family Enterobacteriaceae. In conclusion, resistance to fluoroquinolones and cefotaxime remains rare in human S. enterica, but clonal resistant serotypes arise, and continued (inter)national surveillance is mandatory to understand the origin and routes of dissemination thereof.

The β-Lacta test for direct detection of extended-spectrum-β-lactamase-producing Enterobacteriaceae in urine

With the β-Lacta test, production of extended-spectrum β-lactamases (ESBLs) was assayed in 200 urine samples showing Gram-negative bacilli during direct microscopic examination. While 168 samples tested negative, all samples yielding ESBL-producing Enterobacteriaceae after culture gave positive (n = 30) or uninterpretable (n = 2) results. The sensitivity and specificity of ESBL detection were 94% and 100%, respectively.

Novel antibiotic treatment for skin and soft tissue infection

PURPOSE OF REVIEW

Acute bacterial skin and skin structure infection (ABSSSI) is a common and significant indication for antibiotic treatment. The microbial aetiology is becoming more resistant to available antibiotics and the treatment of patients is additionally challenged by extremes of age, obesity, diabetes and other co-morbidities. This review examines recent antimicrobial developments.

RECENT FINDINGS

In many parts of the world, multidrug-resistant (MDR) staphylococci are the predominant cause of ABSSSI in both the community and in hospital. Increasing resistance in Gram-negative organisms presents problems in the management of surgical-site infections. Most new antibiotics have been developed to treat MDR Gram-positive bacteria and there are few agents to treat infections caused by MDR Gram-negative pathogens.

SUMMARY

A number of novel agents are available clinically, with other agents of related chemical structure under development. There are no entirely new classes of antibiotics. Maintaining the efficacy of antimicrobial treatment require effective antibiotic stewardship, good infection prevention and the development of further new antibiotics.

Risk factors, outcome and impact of empirical antimicrobial treatment in extended-spectrum β-lactamase-producing Escherichia coli bacteraemia

BACKGROUND

To investigate patient characteristics and empirical antimicrobial treatment of extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) bacteraemia, to determine risk factors, outcome and impact of empirical antimicrobial treatment.

METHODS

We performed a retrospective case-control study of all patients diagnosed with ESBL-EC from January 2011 to September 2012. The control group consisted of patients with non-ESBL E. coli bacteraemia. The groups were compared with respect to empirical treatment, risk factors and outcome, using univariate and multivariate analysis.

RESULTS

The study consisted of 70 consecutive cases of ESBL-producing and 140 controls of non-ESBL-producing E. coli bacteraemia. ESBL-EC prevalence of bloodstream invasive E. coli isolates was 6.1%. The independent risk factor found for ESBL-EC bacteraemia was a prior culture with ESBL production (p < 0.001). A higher frequency of inappropriate empirical antibiotic treatment (p < 0.001) and a trend towards worse outcome was observed in patients infected with ESBL-EC and empirical guidelines were more often not followed (p = 0.013). If the guidelines were followed this was associated with adequate initial antibiotic treatment (p < 0.001).

CONCLUSIONS

Patients with ESBL-EC frequently received inappropriate empirical treatment and guidelines were more often not followed. A prior culture of ESBL-producing bacteria was an independent predictor and risk factor for ESBL-EC bacteraemia. Since the prevalence of ESBL-producing E. coli is increasing the importance of adequate guidelines must be emphasized.

Identification of anti-virulence compounds that disrupt quorum-sensing regulated acute and persistent pathogenicity

Etiological agents of acute, persistent, or relapsing clinical infections are often refractory to antibiotics due to multidrug resistance and/or antibiotic tolerance. Pseudomonas aeruginosa is an opportunistic Gram-negative bacterial pathogen that causes recalcitrant and severe acute chronic and persistent human infections. Here, we target the MvfR-regulated P. aeruginosa quorum sensing (QS) virulence pathway to isolate robust molecules that specifically inhibit infection without affecting bacterial growth or viability to mitigate selective resistance. Using a whole-cell high-throughput screen (HTS) and structure-activity relationship (SAR) analysis, we identify compounds that block the synthesis of both pro-persistence and pro-acute MvfR-dependent signaling molecules. These compounds, which share a benzamide-benzimidazole backbone and are unrelated to previous MvfR-regulon inhibitors, bind the global virulence QS transcriptional regulator, MvfR (PqsR); inhibit the MvfR regulon in multi-drug resistant isolates; are active against P. aeruginosa acute and persistent murine infections; and do not perturb bacterial growth. In addition, they are the first compounds identified to reduce the formation of antibiotic-tolerant persister cells. As such, these molecules provide for the development of next-generation clinical therapeutics to more effectively treat refractory and deleterious bacterial-human infections.

Antibiotic resistant and tolerant bacterial pathogens are responsible for acute, chronic and persistent human infections recalcitrant to any current treatments. Therefore, there is an urgent need to identify new antimicrobial drugs that will help circumvent the current antibiotic resistance crisis. Bacterial pathogens often develop resistance to antibiotic drugs that target bacterial growth or viability. In contrast, strategies that specifically target virulence pathways non-essential for growth could limit selective resistance, and thus are candidates for the development of next-generation antimicrobial therapeutics. In this study we target the bacterial communication system MvfR (PqsR), which is known to control virulence of the opportunistic bacterial pathogen Pseudomonas aeruginosa. We identified and improved upon new small molecules that effectively silence the MvfR communication system, and as a result block P. aeruginosa virulence both in vitro and in vivo. Moreover, these new compounds are the first known to restrict the ability of bacteria to form antibiotic-tolerant cells and consequently proved to be very effective at preventing persistent infection in a mammalian infection model. Because of their ability to simultaneously block acute and persistent infections, these new molecules may provide a very strong basis for the development of next generation antimicrobials.

Bactericidal activities of GM flax seedcake extract on pathogenic bacteria clinical strains

BACKGROUND

The antibiotic resistance of pathogenic microorganisms is a worldwide problem. Each year several million people across the world acquire infections with bacteria that are antibiotic-resistant, which is costly in terms of human health. New antibiotics are extremely needed to overcome the current resistance problem.

RESULTS

Transgenic flax plants overproducing compounds from phenylpropanoid pathway accumulate phenolic derivatives of potential antioxidative, and thus, antimicrobial activity. Alkali hydrolyzed seedcake extract containing coumaric acid, ferulic acid, caffeic acid, and lignan in high quantities was used as an assayed against pathogenic bacteria (commonly used model organisms and clinical strains). It was shown that the extract components had antibacterial activity, which might be useful as a prophylactic against bacterial infection. Bacteria topoisomerase II (gyrase) inhibition and genomic DNA disintegration are suggested to be the main reason for rendering antibacterial action.

CONCLUSIONS

The data obtained strongly suggest that the seedcake extract preparation is a suitable candidate for antimicrobial action with a broad spectrum and partial selectivity. Such preparation can be applied in cases where there is a risk of multibacterial infection and excellent answer on global increase in multidrug resistance in pathogenic bacteria.

Epidemiology of infections due to extended-spectrum Beta-lactamase-producing bacteria in a pediatric intensive care unit

OBJECTIVES

To determine the proportion of infections caused by extended-spectrum ß-lactamase (ESBL)-producing Klebsiella or Escherichia coli Gram-negative organisms in the pediatric intensive care unit (PICU), and to identify risk factors for these infections.

METHODS

A retrospective, single-center chart review of patients admitted to a PICU in a 5-year period with infections caused by Klebsiella species or E coli was completed. Data collected include demographics, length of stay, outcome, and relevant risk factors previously defined in the literature.

RESULTS

A total of 110 isolates were cultured from 94 patients. A total of 53% of the isolates were E coli, and the remainder were Klebsiella subspecies. Of the 110 isolates, 13 isolates (11.8%) in 7 patients were ESBL positive. The ESBL-producing isolates were equally distributed amongE coli and Klebsiella and were primarily cultured from tracheal aspirates. Most of the ESBL-positive isolates (9 of 13; 69%) were cultured from patients who received ceftazidime and/or cefotaxime in the preceding 30 days. Patients infected with E coli had higher PRISM 1 scores and were more likely to have a Foley catheter, whereas infections with Klebsiella were more common in mechanically ventilated males. Although not statistically significant, 80% of patients who were infected with non-ESBL-producing organisms survived to hospital discharge versus 57% of those infected with ESBL-producing E coli and Klebsiella.

CONCLUSIONS

Almost 12% of E coli and Klebsiella isolates in this patient population tested positive for ESBL production. ESBL production was equally distributed between E coli and Klebsiella species. These organisms were cultured from 7% of the study patients. As reported in previous studies, patients infected with ESBL-producing organisms most often had received prior cephalosporins and had a longer length of stay in the PICU.

Antimicrobial susceptibility and extended-spectrum beta-lactamase rates in aerobic gram-negative bacteria causing intra-abdominal infections in Vietnam: report from the Study for Monitoring Antimicrobial Resistance Trends (SMART 2009-2011)

Treatment options for multidrug-resistant pathogens remain problematic in many regions and individual countries, warranting ongoing surveillance and analysis. Limited antimicrobial susceptibility information is available for pathogens from Vietnam. This study determined the bacterial susceptibility of aerobic gram-negative pathogens of intra-abdominal infections among patients in Vietnam during 2009-2011. A total of 905 isolates were collected from 4 medical centers in this investigation as part of the Study for Monitoring Antimicrobial Resistance Trends. Antimicrobial susceptibility and extended-spectrum beta-lactamase (ESBL) rates among the appropriate species were determined by a central laboratory using Clinical and Laboratory Standards Institute methods. Among the species collected, Escherichia coli (48.1% ESBL-positive) and Klebsiella pneumoniae (39.5% ESBL-positive) represented the majority (46.4%) of the isolates submitted for this study. Ertapenem MIC90 values were lowest for these 2 species at 0.12 and 0.25μg/mL and remained unchanged for ESBL-positive isolates. Imipenem MIC90 values were also the same for all isolates and ESBL-positive strains at 0.25 and 0.5μg/mL, respectively. Ertapenem MIC90 values for additional species with sufficient numbers for analysis, including Enterobacter cloacae, Proteus mirabilis, Acinetobacter baumannii, and Pseudomonas aeruginosa, were 1, 0.06, >4, and >4μg/mL, respectively. Analysis of beta-lactamases in a subset of 132 phenotypically ESBL-positive Enterobacteriaceae demonstrated that CTX-M variants, particularly CTX-M-27 and CTX-M-15, were the predominant enzymes. High resistance rates in Vietnam hospitals dictate continuous monitoring as antimicrobial inactivating enzymes continue to spread throughout Asia and globally.

Barriers to the effective treatment of sepsis: antimicrobial agents, sepsis definitions, and host-directed therapies

Sepsis is a complex clinical syndrome involving both infection and a deleterious host immune response. Antimicrobial agents are key elements of sepsis treatment, yet despite great strides in antimicrobial development in the last decades, sepsis continues to be associated with unacceptably high mortality (~30%). This is the result, on one hand, of the rise of antimicrobial resistant organisms and, on the other hand, of the dearth of effective host-directed immune therapies. A major obstacle to the development of good host-directed therapies is the lack of understanding of the host immune response. The problem is exacerbated by poor nonspecific clinical definitions of disease. Poor definitions have had a profound impact on sepsis research, from epidemiologic studies to the failed clinical trials of host-directed therapies. Therefore, better definitions must be developed to enable advancement in the field.

Bugs, hosts and ICU environment: countering pan-resistance in nosocomial microbiota and treating bacterial infections in the critical care setting

ICUs are areas where resistance problems are the largest, and these constitute a major problem for the intensivist's clinical practice. Main resistance phenotypes among nosocomial microbiota are (i) vancomycin-resistance/heteroresistance and tolerance in grampositives (MRSA, enterococci) and (ii) efflux pumps/enzymatic resistance mechanisms (ESBLs, AmpC, metallo-betalactamases) in gramnegatives. These phenotypes are found at different rates in pathogens causing respiratory (nosocomial pneumonia/ventilator-associated pneumonia), bloodstream (primary bacteremia/catheter-associated bacteremia), urinary, intraabdominal and surgical wound infections and endocarditis in the ICU. New antibiotics are available to overcome non-susceptibility in grampositives; however, accumulation of resistance traits in gramnegatives has led to multidrug resistance, a worrisome problem nowadays. This article reviews microorganism/infection risk factors for multidrug resistance, suggesting adequate empirical treatments. Drugs, patient and environmental factors all play a role in the decision to prescribe/recommend antibiotic regimens in the specific ICU patient, implying that intensivists should be familiar with available drugs, environmental epidemiology and patient factors.

In vitro activity of tigecycline against isolates collected from complicated skin and skin structure infections and intra-abdominal infections in Africa and Middle East countries: TEST 2007-2012

Complicated skin and skin structure infections (cSSSIs) and intra-abdominal infections (IAIs) are problematic due to decreasing therapeutic options available against multidrug-resistant pathogens common among these types of infections. A total of 2245 isolates from African and the Middle Eastern (AfME) countries were collected to determine in vitro activity for tigecycline and comparators during 2007-2012 as part of the Tigecycline Evaluation Surveillance Trial program. Tigecycline was launched in the AfME in 2007 and remains active against a wide range of targeted pathogens worldwide. Isolates were recovered from cSSSI (1990) and IAI (255) from 38 sites in 11 AfME countries. Staphylococcus aureus was the most common species from cSSSI (27.9%), and the methicillin-resistant S. aureus rate was 25%. Enterococcus spp. (7.1%) and Streptococcus agalactiae (2.9%) were other common Gram-positive pathogens represented. Enterobacter spp. (14.5%), Pseudomonas aeruginosa (13.9%), Escherichia coli (11.4%), Klebsiella spp. (10.9%), and Acinetobacter spp. (7.2 %) were the most common Gram-negative species collected. Tigecycline MIC(90) values were 0.25 μg/mL against S. aureus. E. coli and Enterobacter spp. had tigecycline MIC(90) values of 1 and 2 μg/mL, respectively. E. coli was the most frequently collected species from IAI (28.3%), followed by Klebsiella spp. (20.8%), Enterococcus spp. (11.8%), and Stenotrophomonas maltophilia (6.3%). Isolates collected from IAI had the following tigecycline MIC(90) values: E. coli (1 μg/mL), Klebsiella spp. and other Enterobacteriaceae (2 μg/mL), Enterococcus spp. (0.25 μg/mL), and S. maltophilia (1 μg/mL). Tigecycline in vitro activity was observed against a broad spectrum of bacterial species, including strains resistant to other antimicrobial classes.

New β-lactamase inhibitors: a therapeutic renaissance in an MDR world

As the incidence of Gram-negative bacterial infections for which few effective treatments remain increases, so does the contribution of drug-hydrolyzing β-lactamase enzymes to this serious clinical problem. This review highlights recent advances in β-lactamase inhibitors and focuses on agents with novel mechanisms of action against a wide range of enzymes. To this end, we review the β-lactamase inhibitors currently in clinical trials, select agents still in preclinical development, and older therapeutic approaches that are being revisited. Particular emphasis is placed on the activity of compounds at the forefront of the developmental pipeline, including the diazabicyclooctane inhibitors (avibactam and MK-7655) and the boronate RPX7009. With its novel reversible mechanism, avibactam stands to be the first new β-lactamase inhibitor brought into clinical use in the past 2 decades. Our discussion includes the importance of selecting the appropriate partner β-lactam and dosing regimens for these promising agents. This "renaissance" of β-lactamase inhibitors offers new hope in a world plagued by multidrug-resistant (MDR) Gram-negative bacteria.

Clinical epidemiology of the global expansion of Klebsiella pneumoniae carbapenemases

Klebsiella pneumoniae carbapenemases (KPCs) were originally identified in the USA in 1996. Since then, these versatile β-lactamases have spread internationally among Gram-negative bacteria, especially K pneumoniae, although their precise epidemiology is diverse across countries and regions. The mortality described among patients infected with organisms positive for KPC is high, perhaps as a result of the limited antibiotic options remaining (often colistin, tigecycline, or aminoglycosides). Triple drug combinations using colistin, tigecycline, and imipenem have recently been associated with improved survival among patients with bacteraemia. In this Review, we summarise the epidemiology of KPCs across continents, and discuss issues around detection, present antibiotic options and those in development, treatment outcome and mortality, and infection control. In view of the limitations of present treatments and the paucity of new drugs in the pipeline, infection control must be our primary defence for now.

Withdrawal of Staphylococcus aureus from intensive care units in Turkey

BACKGROUND

In the past, Staphylococcus aureus infections have displayed various patterns of epidemiologic curves in hospitals, particularly in intensive care units (ICUs). This study aimed to characterize the current trend in a nationwide survey of ICUs in Turkey.

METHODS

A total of 88 ICUs from 36 Turkish tertiary hospitals were included in this retrospective study, which was performed during the first 3 months of both 2008 (period [P] 1) and 2011 (P2). A P value ≤.01 was considered significant.

RESULTS

Although overall rates of hospital-acquired infection (HAI) and device-associated infection densities were similar in P1 and P2, the densities of HAIs due to S aureus and methicillin-resistant S aureus (MRSA) were significantly lower in P2 (P < .0001). However, the proportion of HAIs due to Acinetobacter was significantly higher in P2 (P < .0001).

CONCLUSIONS

The incidence of S aureus infections is declining rapidly in Turkish ICUs, with potential impacts on empirical treatment strategies in these ICUs.

Pharmacokinetics and in vivo antistaphylococcal efficacy of TXY541, a 1-methylpiperidine-4-carboxamide prodrug of PC190723

The benzamide derivative PC190723 was among the first of a promising new class of FtsZ-directed antibacterial agents to be identified that exhibit potent antistaphylococcal activity. However, the compound is associated with poor drug-like properties. As part of an ongoing effort to develop FtsZ-targeting antibacterial agents with increased potential for clinical utility, we describe herein the pharmacodynamics, pharmacokinetics, in vivo antistaphylococcal efficacy, and mammalian cytotoxicity of TXY541, a novel 1-methylpiperidine-4-carboxamide prodrug of PC190723. TXY541 was found to be 143-times more soluble than PC190723 in an aqueous acidic vehicle (10mM citrate, pH 2.6) suitable for both oral and intravenous in vivo administration. In staphylococcal growth media, TXY541 converts to PC190723 with a half-life of approximately 8h. In 100% mouse serum, the TXY541-to-PC190723 conversion was much more rapid (with a half-life of approximately 3min), suggesting that the conversion of the prodrug in serum is predominantly enzyme-catalyzed. Pharmacokinetic analysis of both orally and intravenously administered TXY541 in mice yielded a half-life for the PC190723 conversion product of 0.56h and an oral bioavailability of 29.6%. Whether administered orally or intravenously, TXY541 was found to be efficacious in vivo in mouse models of systemic infection with both methicillin-sensitive and methicillin-resistant S. aureus. Toxicological assessment of TXY541 against mammalian cells revealed minimal detectable cytotoxicity. The results presented here highlight TXY541 as a potential therapeutic agent that warrants further pre-clinical development.

Investigational antimicrobial agents of 2013

New antimicrobial agents are always needed to counteract the resistant pathogens that continue to be selected by current therapeutic regimens. This review provides a survey of known antimicrobial agents that were currently in clinical development in the fall of 2012 and spring of 2013. Data were collected from published literature primarily from 2010 to 2012, meeting abstracts (2011 to 2012), government websites, and company websites when appropriate. Compared to what was reported in previous surveys, a surprising number of new agents are currently in company pipelines, particularly in phase 3 clinical development. Familiar antibacterial classes of the quinolones, tetracyclines, oxazolidinones, glycopeptides, and cephalosporins are represented by entities with enhanced antimicrobial or pharmacological properties. More importantly, compounds of novel chemical structures targeting bacterial pathways not previously exploited are under development. Some of the most promising compounds include novel β-lactamase inhibitor combinations that target many multidrug-resistant Gram-negative bacteria, a critical medical need. Although new antimicrobial agents will continue to be needed to address increasing antibiotic resistance, there are novel agents in development to tackle at least some of the more worrisome pathogens in the current nosocomial setting.

Systematic analysis of funding awarded for antimicrobial resistance research to institutions in the UK, 1997-2010

Objectives

To assess the level of research funding awarded to UK institutions specifically for antimicrobial resistance-related research and how closely the topics funded relate to the clinical and public health burden of resistance.

Methods

Databases and web sites were systematically searched for information on how infectious disease research studies were funded for the period 1997–2010. Studies specifically related to antimicrobial resistance, including bacteriology, virology, mycology and parasitology research, were identified and categorized in terms of funding by pathogen and disease and by a research and development value chain describing the type of science.

Results

The overall dataset included 6165 studies receiving a total investment of £2.6 billion, of which £102 million was directed towards antimicrobial resistance research (5.5% of total studies, 3.9% of total spend). Of 337 resistance-related projects, 175 studies focused on bacteriology (40.2% of total resistance-related spending), 42 focused on antiviral resistance (17.2% of funding) and 51 focused on parasitology (27.4% of funding). Mean annual funding ranged from £1.9 million in 1997 to £22.1 million in 2009.

Conclusions

Despite the fact that the emergence of antimicrobial resistance threatens our future ability to treat many infections, the proportion of the UK infection-research spend targeting this important area is small. There are encouraging signs of increased investment in this area, but it is important that this is sustained and targeted at areas of projected greatest burden. Two areas of particular concern requiring more investment are tuberculosis and multidrug-resistant Gram-negative bacteria.

The clinical impact of multidrug-resistant gram-negative bacilli in the management of septic shock

Multi-antibiotic drug-resistant (MDR) gram-negative bacilli are becoming a major threat to the standard care of septic patients. Empiric antimicrobial drug regimens to cover likely bacterial pathogens have to be altered in keeping with the spread of MDR pathogens in the health care setting and in the community. Reliable antibiotics for broad spectrum coverage for sepsis such as extended spectrum β-lactam antibiotics, carbapenems, and fluoroquinolones can no longer be counted upon to provide activity against a range of common, virulent pathogens that cause sepsis. In some regions of Asia, South America, and Eastern Europe in particular, MDR pathogens have become a major concern, necessitating the use of potentially toxic and costly antibiotic combinations as initial antibiotic therapy for septic shock. In this brief review, we will focus on the emergence of MDR gram-negative pathogens, resistance mechanisms, and suggest some management and prevention strategies against MDR pathogens.

Matrix-assisted laser desorption ionization-time of flight (maldi-tof) mass spectrometry for detection of antibiotic resistance mechanisms: from research to routine diagnosis

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been successfully applied as an identification procedure in clinical microbiology and has been widely used in routine laboratory practice because of its economical and diagnostic benefits. The range of applications of MALDI-TOF MS has been growing constantly, from rapid species identification to labor-intensive proteomic studies of bacterial physiology. The purpose of this review is to summarize the contribution of the studies already performed with MALDI-TOF MS concerning antibiotic resistance and to analyze future perspectives in this field. We believe that current research should continue in four main directions, including the detection of antibiotic modifications by degrading enzymes, the detection of resistance mechanism determinants through proteomic studies of multiresistant bacteria, and the analysis of modifications of target sites, such as ribosomal methylation. The quantification of antibiotics is suggested as a new approach to study influx and efflux in bacterial cells. The results of the presented studies demonstrate that MALDI-TOF MS is a relevant tool for the detection of antibiotic resistance and opens new avenues for both clinical and experimental microbiology.

A FimH inhibitor prevents acute bladder infection and treats chronic cystitis caused by multidrug-resistant uropathogenic Escherichia coli ST131

BACKGROUND

Escherichia coli O25b:H4-ST131 represents a predominant clone of multidrug-resistant uropathogens currently circulating worldwide in hospitals and the community. Urinary tract infections (UTIs) caused by E. coli ST131 are typically associated with limited treatment options and are often recurrent.

METHODS

Using established mouse models of acute and chronic UTI, we mapped the pathogenic trajectory of the reference E. coli ST131 UTI isolate, strain EC958.

RESULTS

We demonstrated that E. coli EC958 can invade bladder epithelial cells and form intracellular bacterial communities early during acute UTI. Moreover, E. coli EC958 persisted in the bladder and established chronic UTI. Prophylactic antibiotic administration failed to prevent E. coli EC958-mediated UTI. However, 1 oral dose of a small-molecular-weight compound that inhibits FimH, the type 1 fimbriae adhesin, significantly reduced bacterial colonization of the bladder and prevented acute UTI. Treatment of chronically infected mice with the same FimH inhibitor lowered their bladder bacterial burden by >1000-fold.

CONCLUSIONS

In this study, we provide novel insight into the pathogenic mechanisms used by the globally disseminated E. coli ST131 clone during acute and chronic UTI and establish the potential of FimH inhibitors as an alternative treatment against multidrug-resistant E. coli.

Continuous increase of the antimicrobial resistance among gram-negative pathogens causing bacteremia: a nationwide surveillance study by the Korean Network for Study on Infectious Diseases (KONSID)

Antimicrobial susceptibility data for all microorganisms isolated from blood culture were collected from 13 institutions in Korea from June to September 2011. Data were compared with our previous studies performed during 2006-2007 and 2008. The prevalence of MRSA in 2011 has rebounded to 63.7% after a slight decrease in 2008. Vancomycin-resistant Enterococcus faecium declined to 24.1%. The resistance rates of Acinetobacter baumannii to imipenem and meropenem increased from 25.4% and 28.8% to 55.4% and 37.5%, respectively. Ciprofloxacin resistance of Escherichia coli has increased from 23.9% to 30.8%. The resistance rate of Klebsiella pneumoniae to ciprofloxacin has increased from 17.7% to 26.5%. Extended spectrum beta-lactamase-producing E. coli and K. pneumoniae have also seen increased levels of resistance, from 8.6% to 18.4% and 13.6% to 28.5%, respectively. An overall increase in antimicrobial resistance among gram-negative pathogens has been observed. Continued surveillance and intervention to slow the propagation of resistance are necessary.

The availability of purine nucleotides regulates natural competence by controlling translation of the competence activator Sxy

Many bacteria are naturally competent, able to bind and take up DNA from their extracellular environment. This DNA can serve as a significant source of nutrients, in addition to providing genetic material for recombination. The regulation of competence in several model organisms highlights the importance of this nutritional function, although it has often been overlooked. Natural competence is induced by starvation in Haemophilus influenzae, the model for competence regulation in the gamma-proteobacteria. This induction depends on the activation of the global metabolic regulator CRP, which occurs upon depletion of phosphotransferase sugars. In this work, we show that the depletion of purine nucleotides under competence-inducing conditions activates the CRP-dependent competence-specific regulator Sxy. Depletion of extra- or intra-cellular purine nucleotides activates Sxy translation, while high levels inhibit it. This is modulated by the stem structure formed by sxy mRNA. The exact mechanism by which the nucleotide depletion signal is transduced is unclear, but it does not involve direct binding of purine intermediates to the sxy stem, and does not require Hfq or competence proteins. Similar regulation occurs in the relatives of H. influenzae, Actinobacillus pneumoniae and A. suis, confirming the importance of processes enabling competent bacteria to exploit the abundant DNA in their environments.

Pharmacokinetic and pharmacodynamics evaluation of ceftobiprole medocaril for the treatment of hospital-acquired pneumonia

INTRODUCTION

Ceftobiprole is a cephalosporin with activity against methicillin-resistant Staphylococcus aureus, Enterobacteriaceae, and Pseudomonas aeruginosa with a promising role in the treatment of hospital-acquired pneumonia (HAP). Cure rates, however, with ceftobiprole at the doses studied may be inferior to conventional treatment in the ventilator-acquired subset of HAP.

AREAS COVERED

Literature was sought using PubMed and through abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy (2006 - 2012) and the European Congress of Clinical Microbiology and Infectious Diseases (2007 - 2012). The authors used the search terms "ceftobiprole," "BAL9141," "RO63-9141," "BAL5788," and 'RO5788." The article discusses the activity, mechanism of action, pharmacokinetics (PK), pharmacodynamics (PD), and clinical trials of ceftobiprole in HAP. The article also provides discussion of how PK/PD parameters play a role in the outcome of HAP treatment and how dosing in ventilator-associated pneumonia (VAP) should be reconsidered in light of altered PK/PD.

EXPERT OPINION

In patients with normal PK and non-VAP, ceftobiprole is effective for the treatment of HAP in the recommended doses, ceftobiprole is unlikely to achieve the desired PD targets when PK parameters are altered in VAP (e.g., increased volume of distribution and clearance). In these settings, off-label use at higher doses may overcome these limitations; but in the presence of alternative therapies, it cannot be currently recommended.

BLIP-II is a highly potent inhibitor of Klebsiella pneumoniae carbapenemase (KPC-2)

β-Lactamase inhibitory protein II (BLIP-II) is a potent inhibitor of class A β-lactamases. KPC-2 is a class A β-lactamase that is capable of hydrolyzing carbapenems and has become a widespread source of resistance to these drugs for Gram-negative bacteria. Determination of association and dissociation rate constants for binding between BLIP-II and KPC-2 reveals a very tight interaction with a calculated (koff/kon) equilibrium dissociation constant of 76 fM (76 × 10(-15) M).

Chromosome-mediated OXA-48 carbapenemase in highly virulent Escherichia coli

OBJECTIVES

Bacteria multiresistant to antibiotics are widely supposed to be weakly virulent. However, the virulence traits of carbapenem-resistant Enterobacteriaceae have not been investigated. In this work, we investigated the virulence and resistance mechanism of an extraintestinal pathogenic Escherichia coli (ExPEC) strain (LEB15) that exhibited decreased susceptibility to carbapenems.

METHODS

The MICs were determined by a microdilution method. The β-lactamase-encoding gene was identified by PCR and sequencing, and the genetic environment was analysed by PFGE and PCR mapping. The genetic background was investigated by multilocus sequence typing (MLST). Virulence-factor-encoding genes and pathogenic islands (PAIs) were detected by multiplex PCR. Virulence was assessed in a mouse sepsis model.

RESULTS

Strain LEB15 produced a chromosomal OXA-48 carbapenemase. The complete bla(OXA-48)-encoding Tn1999.2 transposon was inserted in the LEB15 chromosome. The strain belonged to an MLST cluster of emerging ExPEC strains (ST-127/ST-22). It had a high pathogenic score and eight PAIs (I536, II536, III536, IV536, VI536, I(CFT073), II(CFT073) and II(J96)) and induced an unusually high lethality in the mouse sepsis model.

CONCLUSIONS

Strain LEB15 combines both an atypical broad accumulation of virulence factors, which confers a strong killer phenotype, and a decrease in susceptibility to carbapenems following the chromosomal acquisition of bla(OXA-48). This association of virulence and carbapenemase in E. coli strains might pose major problems in the future for E. coli infection management.

Novel derivatives of polymyxins

Polymyxin B and colistin (polymyxin E) are bactericidal pentacationic lipopeptides that act specifically on Gram-negative bacteria, first by disrupting their outermost permeability barrier, the outer membrane (OM), and then damaging the cytoplasmic membrane. Both were discovered in the mid-1950s and subsequently used in intravenous therapy, but soon largely abandoned because of nephrotoxicity. The emergence of extremely multiresistant strains has now forced clinicians to reinstate them in the therapy of severe infections caused by such strains. This article reviews recent attempts to develop novel derivatives of polymyxins that exhibit less toxicity and greater potency than the existing drugs. In addition, studies of novel des-fatty acyl-polymyxin derivatives that display activity against Pseudomonas aeruginosa are included. The review also covers recent studies of derivatives that lack potent bactericidal action, but which disrupt the OM, which increases bacterial permeability to other antibiotics, facilitating their entry into the cell.

The global spread of healthcare-associated multidrug-resistant bacteria: a perspective from Asia

Since antibiotics were first used, each new introduced class has been followed by a global wave of emergent resistance, largely originating in Europe and North America where they were first used. Methicillin-resistant Staphylococcus aureus spread from the United Kingdom and North America across Europe and then Asia over more than a decade. Vancomycin-resistant enterococci and Klebsiella pneumoniae carbapenemase-producing K. pneumoniae followed a similar path some 20 years later. Recently however, metallo-β-lactamases have originated in Asia. New Delhi metallo-β-lactamase-1 was found in almost every continent within a year of its emergence in India. Metallo-β-lactamase enzymes are encoded on highly transmissible plasmids that spread rapidly between bacteria, rather than relying on clonal proliferation. Global air travel may have helped facilitate rapid dissemination. As the antibiotic pipeline offers little in the short term, our most important tools against the spread of antibiotic resistant organisms are intensified infection control, surveillance, and antimicrobial stewardship.

Metallo-β-lactamase structure and function

β-Lactam antibiotics are the most commonly used antibacterial agents and growing resistance to these drugs is a concern. Metallo-β-lactamases are a diverse set of enzymes that catalyze the hydrolysis of a broad range of β-lactam drugs including carbapenems. This diversity is reflected in the observation that the enzyme mechanisms differ based on whether one or two zincs are bound in the active site that, in turn, is dependent on the subclass of β-lactamase. The dissemination of the genes encoding these enzymes among Gram-negative bacteria has made them an important cause of resistance. In addition, there are currently no clinically available inhibitors to block metallo-β-lactamase action. This review summarizes the numerous studies that have yielded insights into the structure, function, and mechanism of action of these enzymes.