Antibiotic-resistant Gram-negative Bacteria Research Articles

Active surveillance for multidrug-resistant Gram-negative bacteria in the intensive care unit

A short-term program of performing serial active screening cultures (ASC) in the intensive care unit was instituted to establish a method for the detection of antibiotic-resistant Gram-negative bacteria (GNB) and the local rates of colonisation. Of all submitted ASC, 25.9% (30/116 collected swabs) isolated an antibiotic-resistant GNB. ChromID ESBL agar (bioMérieux, France) identified the majority of these organisms, with the additional antibiotic-impregnated media [MacConkey agar (MCA) with ciprofloxacin, MCA with gentamicin and MCA with ceftazidime] adding limited benefit. Compared to swabs performed on admission, 37.8% (14/37) of patients cultured a new antibiotic-resistant isolate on discharge. Serial screening in intensive care has the ability to identify patients with unrecognised colonisation with antibiotic-resistant GNB; however, the increase in the laboratory workload and logistical challenges in the collection of the surveillance swabs may limit this program's expansion.

Scolopendrasin I: a novel antimicrobial peptide isolated from the centipede Scolopendra subspinipes mutilans

In a previous report, we identified several candidate antimicrobial peptides through de novo RNA sequencing of the centipede Scolopendra subspinipes mutilans . Here, we identify and characterize one of these peptides, Scolopendrasin I. We identified the centipede antimicrobial peptide Cecropin from the centipede transcriptome using an SVM algorithm, and subsequently analyzed the amino acid sequence for predicted secondary structure using a GOR algorithm. We identified an alpha helical region of Cecropin and named it Scolopendrasin I. We then assessed antimicrobial and hemolytic activity of Scolopendrasin I. Scolopendrasin I showed antimicrobial activity against various microbes, including antibiotic-resistant Gram-negative bacteria, in a radial diffusion assay. Scolopendrasin I had potent antibacterial activity against acne-associated microbes in a colony count assay and showed no hemolytic activity in a hemolysis assay. In addition, we confirmed that Scolopendrasin I bound to the surface of bacteria via a specific interaction with lipoteichoic acid and lipopolysaccharide, two components of bacterial cell membranes. In conclusion, the results presented here provide evidence that this is an efficient strategy for antimicrobial peptide candidate identification and that Scolopendrasin I has potential for successful antibiotic development.

Urosepsis: Overview of the Diagnostic and Treatment Challenges.

Urosepsis is defined as sepsis caused by an infection in the urogenital tract. In approximately 30% of all septic patients the infectious focus is localized in the urogenital tract, mainly due to obstructions at various levels, such as ureteral stones. Urosepsis may also occur after operations in the urogenital tract. In urosepsis, complete bacteria and components of the bacterial cell wall from the urogenital tract trigger the host inflammatory event and act as exogenous pyrogens on eukaryotic target cells of patients. A burst of second messenger molecules leads to several different stages of the septic process, from hyperactivity to immunosuppression. As pyelonephritis is the most frequent cause for urosepsis, the kidney function is therefore most important in terms of cause and as a target organ for dysfunction in the course of the sepsis.Since effective antimicrobial therapy must be initiated early during sepsis, the empiric intravenous therapy should be initiated immediately after microbiological sampling. For the selection of appropriate antimicrobials, it is important to know risk factors for resistant organisms and whether the sepsis is primary or secondary and community or nosocomially acquired. In addition, the preceding antimicrobial therapies should be recorded as precisely as possible. Resistance surveillance should, in any case, be performed locally to adjust for the best suitable empiric treatment. Treatment challenges arise from the rapid increase of antibiotic resistance in Gram-negative bacteria, especially extended-spectrum β-lactamase (ESBL)-producing bacteria. Treatment of urosepsis comprises four basic strategies I) supportive therapy (stabilizing and maintaining blood pressure), II) antimicrobial therapy, III) control or elimination of the complicating factor, and IV) specific sepsis therapy.

High dietary zinc supplementation increases the occurrence of tetracycline and sulfonamide resistance genes in the intestine of weaned pigs

BackgroundDietary zinc oxide is used in pig nutrition to combat post weaning diarrhoea. Recent data suggests that high doses (2.5 g/kg feed) increase the bacterial antibiotic resistance development in weaned pigs. Therefore, the aim of this study was to investigate the development of enterobacterial antibiotic resistance genes in the intestinal tract of weaned pigs.FindingsWeaned pigs were fed diets for 4 weeks containing 57 (low), 164 (intermediate) or 2425 (high) mg kg−1 analytical grade ZnO. DNA extracts from stomach, mid-jejunum, terminal ileum and colon ascendens were amplified by qPCR assays to quantify copy numbers for the tetracycline (tetA) and sulfonamide (sul1) resistance genes in Gram-negative bacteria. Overall, the combined data (n = 336) showed that copy numbers for tetracycline and sulfonamide resistance genes were significantly increased in the high zinc treatment compared to the low (tetA: p value < 10−6; sul1: p value = 1 × 10−5) or intermediate (tetA: P < 1.6 × 10−4; sul1: P = 3.2 × 10−4) zinc treatment. Regarding the time dependent development, no treatment effects were seen 1 week after weaning, but significant differences between high and low/intermediate zinc treatments evolved 2 weeks after weaning. The increased number of tetA and sul1 copies was not confined to the hind gut, but was already present in stomach contents.ConclusionsThe results of this study suggest that the use of high doses of dietary zinc beyond 2 weeks after weaning should be avoided in pigs due to the possible increase of antibiotic resistance in Gram-negative bacteria.Electronic supplementary materialThe online version of this article (doi:10.1186/s13099-015-0071-3) contains supplementary material, which is available to authorized users.

What is new in selective decontamination of the digestive tract?

What is new in selective decontamination of the digestive tract?

Assay for drug discovery: Synthesis and testing of nitrocefin analogues for use as β-lactamase substrates

We report on the synthesis of three nitrocefin analogues and their evaluation as substrates for the detection of β-lactamase activity. These compounds are hydrolyzed by all four Ambler classes of β-lactamases. Kinetic parameters were determined with eight different β-lactamases, including VIM-2, NDM-1, KPC-2, and SPM-1. The compounds do not inhibit the growth of clinically important antibiotic-resistant gram-negative bacteria in vitro. These chromogenic compounds have a distinct absorbance spectrum and turn purple when hydrolyzed by β-lactamases. One of these compounds, UW154, is easier to synthesize from commercial starting materials than nitrocefin and should be significantly less expensive to produce.

Selective oropharyngeal decontamination versus selective digestive decontamination in critically ill patients: a meta-analysis of randomized controlled trials.

BackgroundSelective digestive decontamination (SDD) and selective oropharyngeal decontamination (SOD) are associated with reduced mortality and infection rates among patients in intensive care units (ICUs); however, whether SOD has a superior effect than SDD remains uncertain. Hence, we conducted a meta-analysis of randomized controlled trials (RCTs) to compare SOD with SDD in terms of clinical outcomes and antimicrobial resistance rates in patients who were critically ill.MethodsRCTs published in PubMed, Embase, and Web of Science were systematically reviewed to compare the effects of SOD and SDD in patients who were critically ill. Outcomes included day-28 mortality, length of ICU stay, length of hospital stay, duration of mechanical ventilation, ICU-acquired bacteremia, and prevalence of antibiotic-resistant Gram-negative bacteria. Results were expressed as risk ratio (RR) with 95% confidence intervals (CIs), and weighted mean differences (WMDs) with 95% CIs. Pooled estimates were performed using a fixed-effects model or random-effects model, depending on the heterogeneity among studies.ResultsA total of four RCTs involving 23,822 patients met the inclusion criteria and were included in this meta-analysis. Among patients whose admitting specialty was surgery, cardiothoracic surgery (57.3%) and neurosurgery (29.7%) were the two main types of surgery being performed. Pooled results showed that SOD had similar effects as SDD in day-28 mortality (RR =1.03; 95% CI: 0.98, 1.08; P=0.253), length of ICU stay (WMD =0.00 days; 95% CI: −0.2, 0.2; P=1.00), length of hospital stay (WMD =0.00 days; 95% CI: −0.65, 0.65; P=1.00), and duration of mechanical ventilation (WMD =1.01 days; 95% CI: −0.01, 2.02; P=0.053). On the other hand, compared with SOD, SDD had a lower day-28 mortality in surgical patients (RR =1.11; 95% CI: 1.00, 1.22; P=0.050), lower incidence of ICU-acquired bacteremia (RR =1.38; 95% CI: 1.24, 1.54; P=0.000), and lower rectal carriage of aminoglycosides (RR =2.08; 95% CI: 1.68, 2.58; P=0.000), ciprofloxacin-resistant Gram-negative bacteria (RR =1.84; 95% CI: 1.48, 2.29; P=0.000), and respiratory carriage of third-generation cephalosporin-resistant Gram-negative bacteria (RR =2.50; 95% CI: 1.78, 3.5; P=0.000).ConclusionSOD has similar effects as SDD in clinical outcomes, but has higher incidence of ICU-acquired bacteremia, and higher carriage of antibiotic-resistant Gram-negative bacteria. However, due to the high cost of SDD and the increased risk of development of antibiotic resistance with the widespread use of cephalosporins in SDD, we would recommend SOD as prophylactic antibiotic regimens in patients in the ICU. More well-designed, large-scale RCTs are needed to confirm our findings.

Investigation into combination of an antimicrobial peptide with existing antibiotics against antibiotic resistant clinical isolates of Escherichia coli

Bacterial infections remain the leading killer worldwide which is worsened by the continuous emergence of antibiotic resistance. In particular, antibiotic resistant Gram-negative bacteria are prevalent and extremely difficult to treat. Therefore, rejuvenating the therapeutic potentials of existing antibiotics represents an attractive novel strategy. Antimicrobial peptides have been of great focus recently. Newly derived synthetic lipopeptides have been shown to exhibit antimicrobial activity against bacteria and fungi.

Antibiotic Resistance in Gram-Negative Bacteria Isolated From Blood Cultures

Antibiotic Resistance in Gram-Negative Bacteria Isolated From Blood Cultures

Assessment of copper and zinc salts as selectors of antibiotic resistance in Gram-negative bacteria

Some metals are nowadays considered environmental pollutants. Although some, like Cu and Zn, are essential for microorganisms, at high concentrations they can be toxic or exert selective pressures on bacteria. This study aimed to assess the potential of Cu or Zn as selectors of specific bacterial populations thriving in wastewater. Populations of Escherichia coli recovered on metal-free and metal-supplemented culture medium were compared based on antibiotic resistance phenotype and other traits. In addition, the bacterial groups enriched after successive transfers in metal-supplemented culture medium were identified. At a concentration of 1mM, Zn produced a stronger inhibitory effect than Cu on the culturability of Enterobacteriaceae. It was suggested that Zn selected populations with increased resistance prevalence to sulfamethoxazole or ciprofloxacin. In non-selective culture media, Zn or Cu selected for mono-species populations of ubiquitous Betaproteobacteria and Flavobacteriia, such as Ralstonia pickettii or Elizabethkingia anophelis, yielding multidrug resistance profiles including resistance against carbapenems and third generation cephalosporins, confirming the potential of Cu or Zn as selectors of antibiotic resistant bacteria.

Functional disability and nursing resource use are predictive of antimicrobial resistance in nursing homes.

To use a simple measure of activities of daily living, wounds, and indwelling devices (urinary catheter, feeding tube) to predict prevalent, new, and intermittent multidrug-resistant organism (MDRO) acquisition in nursing home (NH) residents. Secondary analysis, prospective cohort study. Southeast Michigan NHs (n = 15). NH residents (N = 111, mean age 81) with two or more monthly visits (729 total). Monthly microbiological surveillance for MDROs from multiple anatomic sites from enrollment until discharge or 1 year. The Arling scale, previously developed as a measure of NH residents' need (time-intensity) for nursing resources, was used to predict prevalent and time to new or intermittent acquisition (months) of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and antibiotic-resistant gram-negative bacteria (R-GNB) colonization using multiple-failure accelerated time-factor survival analysis, controlling for comorbidity, hospitalization, and antibiotic use in the prior month. One-fifth of participants had a wound, and one-third had a device. There were 60 acquisitions of MRSA, 56 of R-GNB, and 15 of VRE. Expected time to acquisition was less than 1 year for MRSA (median 6.7 months) and R-GNB (median 4.5 months) and more than 1 year for VRE (median 40 months). Arling score was associated with earlier new MRSA and VRE acquisition. A resident with only mild functional impairment and no device or wound would be expected to acquire MRSA in 20 months, versus 5 months for someone needing the most-intense nursing contact. MDRO acquisition is common in community NHs. Need for nursing care predicts new MDRO acquisition in NHs, suggesting potential mechanisms for MDRO acquisition and strategies for future interventions for high-risk individuals (e.g., enhanced barrier precautions).

The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria.

The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.

How to Manage Infections Caused by Antibiotic Resistant Gram-negative Bacteria - EBMT Educational Meeting from the Severe Aplastic Anaemia and Infectious Diseases Working Parties, Naples, Italy, 2014

Withdrawn by the publisher.

Plasmid mediated antibiotic resistance in isolated bacteria from burned patients.

Background:Nowadays, the treatment of burned patients is difficult because of the high frequency of infection with antibiotic resistance bacteria.Objectives:This study was conducted to evaluate the level of antibiotic resistance in Gram-negative bacteria and its relation with the existence of plasmid.Materials and Methods:The samples were collected from two hundred twenty hospitalized burned patients in Isfahan burn hospital during a three-month period (March 2012 to June 2012). The samples were isolated and the Gram-negative bacteria were identified using phenotypic method and API 20E System. Antibiotic susceptibility and plasmid profile were determined by standard Agar disc diffusion and plasmid spin column extraction methods.Results:Totally 117 Gram-negative bacteria were isolated, the most common were Pseudomonas aerugionsa (37.6%), P. fluorescens (25.6%), Acinetobacter baumanii (20/5%) and Klebsiella pneumoniae (7.6%), respectively. The isolates showed high frequency of antibiotic resistance against ceftazidime and co-amoxiclave (100%) and low frequency of antibiotic resistance against amikacin with (70%).The results indicated that 60% of the isolates harboured plasmid. On the other hand, the patients infected with A. baumanii and P. aeruginosa were cured (with 60% frequency) whereas, those infected with P. fluorescens were not cured. Hence, probably antibiotic resistance markers of A. baumanii and P. aeruginosa are plasmid mediated; however, P. fluorescens is chromosomally mediated.Conclusions:Based on our findings, P. aerugionsa is a major causative agent of wound infections and amikacin could be considered as a more effective antibiotic for treatment of the burned patients.

Antibiotic-resistant gram-negative bacterial infections in patients with cancer.

Patients with cancer are at high risk for infections caused by antibiotic resistant gram-negative bacteria. In this review, we summarize trends among the major pathogens and clinical syndromes associated with antibiotic resistant gram-negative bacterial infection in patients with malignancy, with special attention to carbapenem and expanded-spectrum β-lactam resistance in Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia--all major threats to our cancer patients. Optimal therapy for these antibiotic-resistant pathogens still remains to be determined.

Antibiotic rotation strategies to reduce antimicrobial resistance in Gram-negative bacteria in European intensive care units: study protocol for a cluster-randomized crossover controlled trial.

BackgroundIntensive care units (ICU) are epicenters for the emergence of antibiotic-resistant Gram-negative bacteria (ARGNB) because of high rates of antibiotic usage, rapid patient turnover, immunological susceptibility of acutely ill patients, and frequent contact between healthcare workers and patients, facilitating cross-transmission.Antibiotic stewardship programs are considered important to reduce antibiotic resistance, but the effectiveness of strategies such as, for instance, antibiotic rotation, have not been determined rigorously. Interpretation of available studies on antibiotic rotation is hampered by heterogeneity in implemented strategies and suboptimal study designs. In this cluster-randomized, crossover trial the effects of two antibiotic rotation strategies, antibiotic mixing and cycling, on the prevalence of ARGNB in ICUs are determined. Antibiotic mixing aims to create maximum antibiotic heterogeneity, and cycling aims to create maximum antibiotic homogeneity during consecutive periods.Methods/DesignThis is an open cluster-randomized crossover study of mixing and cycling of antibiotics in eight ICUs in five European countries. During cycling (9 months) third- or fourth-generation cephalosporins, piperacillin-tazobactam and carbapenems will be rotated during consecutive 6-week periods as the primary empiric treatment in patients suspected of infection caused by Gram-negative bacteria. During mixing (9 months), the same antibiotics will be rotated for each consecutive antibiotic course. Both intervention periods will be preceded by a baseline period of 4 months. ICUs will be randomized to consecutively implement either the mixing and then cycling strategy, or vice versa. The primary outcome is the ICU prevalence of ARGNB, determined through monthly point-prevalence screening of oropharynx and perineum. Secondary outcomes are rates of acquisition of ARGNB, bacteremia and appropriateness of therapy, length of stay in the ICU and ICU mortality. Results will be adjusted for intracluster correlation, and patient- and ICU-level variables of case-mix and infection-prevention measures using advanced regression modeling.DiscussionThis trial will determine the effects of antibiotic mixing and cycling on the unit-wide prevalence of ARGNB in ICUs.Trial registrationClinicalTrials.gov NCT01293071 December 2010.

Integrating rapid diagnostics and antimicrobial stewardship improves outcomes in patients with antibiotic-resistant Gram-negative bacteremia

An intervention for Gram-negative bloodstream infections that integrated mass spectrometry technology for rapid diagnosis with antimicrobial stewardship oversight significantly improved patient outcomes and reduced hospital costs. As antibiotic resistance rates continue to grow at an alarming speed, the current study was undertaken to assess the impact of this intervention in a challenging patient population with bloodstream infections caused by antibiotic-resistant Gram-negative bacteria. A total of 153 patients with antibiotic-resistant Gram-negative bacteremia hospitalized prior to the study intervention were compared to 112 patients treated post-implementation. Outcomes assessed included time to optimal antibiotic therapy, time to active treatment when inactive, hospital and intensive care unit length of stay, all-cause 30-day mortality, and total hospital expenditures. Integrating rapid diagnostics with antimicrobial stewardship improved time to optimal antibiotic therapy (80.9 h in the pre-intervention period versus 23.2 h in the intervention period, P < 0.001) and effective antibiotic therapy (89.7 h versus 32 h, P < 0.001). Patients in the pre-intervention period had increased duration of hospitalization compared to those in the intervention period (23.3 days versus 15.3 days, P = 0.0001) and longer intensive care unit length of stay (16 days versus 10.7 days, P = 0.008). Mortality among patients during the intervention period was lower (21% versus 8.9%, P = 0.01) and our study intervention remained a significant predictor of survival (OR, 0.3; 95% confidence interval [CI], 0.12-0.79) after multivariate logistic regression. Mean hospital costs for each inpatient survivor were reduced $26,298 in the intervention cohort resulting in an estimated annual cost savings of $2.4 million (P = 0.002). Integration of rapid identification and susceptibility techniques with antimicrobial stewardship resulted in significant improvements in clinical and financial outcomes for patients with bloodstream infections caused by antibiotic-resistant Gram-negatives. The intervention decreased hospital and intensive care unit length of stay, total hospital costs, and reduced all-cause 30-day mortality.

Prediction of major antibiotic resistance in Escherichia coli and Klebsiella pneumoniae in Singapore, USA and China using a limited set of gene targets

Antibiotic resistance in Gram-negative bacteria, especially Enterobacteriaceae, can be conferred by a large number of different acquired resistance genes, although it appears that relatively few dominate. A previous survey of Escherichia coli and Klebsiella pneumoniae isolates from Sydney, Australia, revealed that a limited set of genes could reliably predict resistance to third-generation cephalosporins (3GCs) and aminoglycosides. Here we tested E. coli and K. pneumoniae isolates with a cefotaxime, ceftriaxone and/or ceftazidime minimum inhibitory concentration of ≥2μg/mL from China and Singapore, with significantly higher resistance rates than Australia, as well as the USA. Few targets were needed to predict non-susceptibility to 3GCs (95/95; 100%) and gentamicin (47/51; 92%). The gene types detected here are consistent with previous surveys in similar countries with similar resistance rates, where the majority of 3GC resistance can be explained by blaCTX-M genes. This study identified a limited set of genes capable of predicting resistance to 3GC and aminoglycoside antibiotics and implies a restriction in the global resistance gene pool that can be exploited for diagnostic purposes.

Prior colonization is associated with increased risk of antibiotic-resistant Gram-negative bacteremia in cancer patients

We hypothesized that prior colonization with antibiotic-resistant Gram-negative bacteria is associated with increased risk of subsequent antibiotic-resistant Gram-negative bacteremia among cancer patients. We performed a matched case-control study. Cases were cancer patients with a blood culture positive for antibiotic-resistant Gram-negative bacteria. Controls were cancer patients with a blood culture not positive for antibiotic-resistant Gram-negative bacteria. Prior colonization was defined as any antibiotic-resistant Gram-negative bacteria in surveillance or non-sterile-site cultures obtained 2–365 days before the bacteremia. Thirty-two (37%) of 86 cases and 27 (8%) of 323 matched controls were previously colonized by any antibiotic-resistant Gram-negative bacteria. Prior colonization was strongly associated with antibiotic-resistant Gram-negative bacteremia (odds ratio [OR] 7.2, 95% confidence interval [CI] 3.5–14.7) after controlling for recent treatment with piperacillin-tazobactam (OR 2.5, 95% CI 1.3–4.8). In these patients with suspected bacteremia, prior cultures may predict increased risk of antibiotic-resistant Gram-negative bacteremia.

Accurate automated annotation of DNA sequences related to antibiotic resistance in Gram-Negative bacteria

Gram-negative bacteria resistant to multiple antibiotics are an increasing global health problem. This resistance is largely due to resistance genes ‘captured’ by mobile genetic elements that move them between DNA molecules in the same cell. Multi-resistance spreads because genes conferring resistance to different classes of antibiotics and associated mobile elements are found in complex modular clusters on resistance plasmids that can transfer between cells, including different species. Increasing numbers of such plasmids are being sequenced, including by next-generation methods, but are often poorly annotated as current analysis software only gives general names to genes and suggest putative functions. We have developed an automated annotation system (Attacca) for DNA sequences relating to antibiotic resistance in Gram-negative bacteria that accurately and precisely annotates resistance genes and associated mobile elements. Attacca uses a database of relevant ‘features’ and computational grammars derived known rules about the behaviour of different mobile elements to annotate fragments of features and find informative signals that give information about movement of mobile elements. Attacca also creates diagrams of annotated sequences that facilitate detailed comparative analysis to help understand the evolution and spread of multi-resistance. We plan to make Attacca available via a website.