The current state of multidrug-resistant gram-negative bacilli in North America

Towards new bioactive fluorine-containing 1,3,4-oxadiazole-amide derivatives: synthesis, antibacterial activity, molecular docking and molecular dynamics simulation study

Through the approach of molecular hybridization, this study rationally designed and synthesized new trifluoromethyl-1,3,4-oxadiazole amide derivatives, denoted as 1a-1n. The findings reveal that these novel molecules exhibit potent inhibitory effects against various bacterial strains. Thereinto, compounds 1c, 1d, 1i, 1j and 1n, demonstrate relatively superior antimicrobial performance against B. cereus FM314, with a minimum inhibitory concentration (MIC) of 0.03907 μg/mL. Molecular docking analysis suggests the potential importance of the Ser57 and Thr125 amino acid residues (PDB ID: 4EI9) in contributing to the inhibitory activity against B. cereus. The consistency of these results was further corroborated through subsequent molecular dynamics simulations and MMPBSA validations. The insights gained from this study serve to facilitate the rational design and efficient development of novel eco-friendly antimicrobial inhibitors based on the trifluoromethyl-1,3,4-oxadiazole amide scaffold.

Pseudomonas aeruginosa in Nepali hospitals: poor outcomes amid 10 years of increasing antimicrobial resistance

OBJECTIVE

To determine antimicrobial resistance patterns and prevalence of multi- (MDR, i.e., resistant to ⩾3 classes of antimicrobial agents) and extensively (XDR, i.e., resistant to ⩾3, susceptible to ⩽2 groups of antibiotics) drug-resistant strains of Pseudomonas aeruginosa.

METHODS

This was a cross-sectional study conducted in Nepal Mediciti Hospital, Lalitpur, Nepal, using standard microbiological methods with Kirby Bauer disc diffusion to identify antimicrobial susceptibility.

RESULTS

P. aeruginosa (n = 447) were most frequently isolated in respiratory (n = 203, 45.4%) and urinary samples (n = 120, 26.8%). AWaRe Access antibiotics showed 25-30% resistance, Watch antibiotics 30-55%. Susceptibility to AWaRe Reserve antibiotics remains high; however, 32.8% were resistant to aztreonam. Overall, 190 (42.5%) were MDR and 99 (22.1%) XDR (first Nepali report) based on mainly non-respiratory samples. The majority of infected patients were >40 years (n = 229, 63.2%) or inpatients (n = 181, 50.0%); 36 (15.2%) had an unfavourable outcome, including death (n = 25, 10.5%). Our larger study showed a failure of improvement over eight previous studies covering 10 years.

CONCLUSION

Antibiotic resistance in P. aeruginosa occurred to all 19 AWaRe group antibiotics tested. Vulnerable patients are at significant risk from such resistant strains, with a high death rate. Sustainable and acceptable antibiotic surveillance and control are urgently needed across Nepal, as antimicrobial resistance has deteriorated over the last decade.

Dimeric lipo-α/sulfono-γ-AA hybrid peptides as broad-spectrum antibiotic agents

There is an urgent need to develop novel antibiotic agents that can combat emerging drug resistance. Herein, we report the design and investigation of a class of short dimeric antimicrobial lipo-α/sulfono-γ-AA hybrid peptides. Some of these peptides exhibit potent and broad-spectrum antimicrobial activity toward both clinically related Gram-positive and Gram-negative bacteria. The TEM study suggests that these hybrid peptides can compromise bacterial membranes and lead to bacterial death. Membrane depolarization and fluorescence microscopy studies also indicate that the mechanism of action is analogous to host-defense peptides (HDPs). Furthermore, the lead compound shows the ability to effectively inhibit biofilms formed from MRSA and E. coli. Further development of the short dimeric lipo-α/sulfono-γ-AA hybrid peptides may lead to a new generation of antimicrobial biomaterials to combat drug resistance.

It's Not Easy Being Green: A Narrative Review on the Microbiology, Virulence and Therapeutic Prospects of Multidrug-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most frequent cause of infection among non-fermenting Gram-negative bacteria, predominantly affecting immunocompromised patients, but its pathogenic role should not be disregarded in immunocompetent patients. These pathogens present a concerning therapeutic challenge to clinicians, both in community and in hospital settings, due to their increasing prevalence of resistance, and this may lead to prolonged therapy, sequelae, and excess mortality in the affected patient population. The resistance mechanisms of P. aeruginosa may be classified into intrinsic and acquired resistance mechanisms. These mechanisms lead to occurrence of resistant strains against important antibiotics-relevant in the treatment of P. aeruginosa infections-such as β-lactams, quinolones, aminoglycosides, and colistin. The occurrence of a specific resistotype of P. aeruginosa, namely the emergence of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) strains, has received substantial attention from clinical microbiologists and infection control specialists; nevertheless, the available literature on this topic is still scarce. The aim of this present review paper is to provide a concise summary on the adaptability, virulence, and antibiotic resistance of P. aeruginosa to a readership of basic scientists and clinicians.

Direct Antimicrobial Susceptibility Testing on Clinical Urine Samples by Optical Tracking of Single Cell Division Events

With the increasing prevalence of antibiotic resistance, the need to develop antimicrobial susceptibility testing (AST) technologies is urgent. The current challenge has been to perform the antibiotic susceptibility testing in short time, directly with clinical samples, and with antibiotics over a broad dynamic range of clinically relevant concentrations. Here, a technology for point-of-care diagnosis of antimicrobial-resistant bacteria in urinary tract infections, by imaging the clinical urine samples directly with an innovative large volume solution scattering imaging (LVSi) system and analyzing the image sequences with a single-cell division tracking method is developed. The high sensitivity of single-cell division tracking associated with large volume imaging enables rapid antibiotic susceptibility testing directly on the clinical urine samples. The results demonstrate direct detection of bacterial infections in 60 clinical urine samples with a 60 min LVSi video, and digital AST of 30 positive clinical samples with 100% categorical agreement with both the clinical culture results and the on-site agar plating validation results. This technology provides opportunities for precise antibiotic prescription and proper treatment of the patient within a single clinic visit.

In Vivo Activity of QPX7728, an Ultrabroad-Spectrum Beta-Lactamase Inhibitor, in Combination with Beta-Lactams against Carbapenem-Resistant Klebsiella pneumoniae

Resistance to beta-lactams has created a major clinical issue. QPX7728 is a novel ultrabroad-spectrum cyclic boronic acid beta-lactamase inhibitor with activity against both serine and metallo-beta-lactamases developed to address this resistance for use in combination with beta-lactam antibiotics. The objective of these studies was to evaluate the activity of QPX7728 in combination with multiple beta-lactams against carbapenem-resistant Klebsiella pneumoniae isolates in a neutropenic mouse thigh infection model. Neutropenic mice were infected with strains with potentiated beta-lactam MICs of ≤2 mg/liter in the presence of 8 mg/liter QPX7728. Two strains of carbapenem-resistant K. pneumoniae were tested with aztreonam, biapenem, cefepime, ceftazidime, ceftolozane, and meropenem alone or in combination with 12.5, 25, or 50 mg/kg of body weight of QPX7728 every 2 hours for 24 hours. Treatment with all beta-lactams alone either was bacteriostatic or allowed for bacterial growth. The combination of QPX7728 plus each of these beta-lactams produced bacterial killing at all QPX7728 doses tested. Overall, these data suggest that QPX7728 administered in combination with different partner beta-lactam antibiotics may have utility in the treatment of bacterial infections due to carbapenem-resistant K. pneumoniae.

Comparison of the effects of Lactobacillus plantarum versus imipenem on infected burn wound healing

Background: Infection of burn wounds is one of the most important problems in the world. Lactobacillus plantarum is known for burn wound healing because of the immunomodulatory and anti-microbial roles. This study was performed to compare the effects of L. plantarum and imipenem - alone and in combination - on infected burn wound healing. Methods: Burn wounds were experimentally induced on 50 rats in three test groups (germ and supernatant of L. plantarum ) and two control groups (n=10 each) and were inoculated with Pseudomonas aeruginosa. During a 14-day period, wounds in all groups were daily treated topically. The data were analyzed using one-way analysis of variance followed by Tukey-Kramer and LSD. A p-value of < 0.05 was considered as statistically significant. Results: The mean size of the wound on day 14 after the treatment in the probiotic group was significantly lower than the control and the supernatant treated groups (p<0.05). The percentage of wound healing was significantly higher in the probiotic pellet treated group compared to the imipenem and the supernatant groups (by Anova test: 69.58%, p=0.022). The mean leukocyte count in the probiotic pellet group (12110) and supernatant group (13650) was significantly higher than the imipenem group (7670) (p=0.002 and 0.001, respectively). Wound cultures revealed that the percentage of cases where the pathogens had no growth was significantly different among the comparison groups. In all three test groups, P. aeruginosa was completely eliminated in comparison to the positive control group (p<0.05). Conclusion: The results of our study showed that L. plantarum and its by-products promote wound healing and can be used as an alternative to antibiotics to treat ulcer infections caused by resistant bacteria.

Microfluidic systems for rapid antibiotic susceptibility tests (ASTs) at the single-cell level

Infectious diseases caused by multidrug resistant (MDR) bacterial pathogens are impending threats to global health. Since delays in identifying drug resistance would significantly increase mortality, fast and accurate antibiotic susceptibility tests (ASTs) are critical for addressing the antibiotic resistance issue. However, the conventional methods for ASTs are always labor-intensive, imprecise, complex and slow (taking 2-3 days). To address these issues, some advanced microfluidic systems have been designed for rapid phenotypic and genotypic analysis of antibiotic resistance. This review highlights the recent development of microfluidics-based ASTs at the single-cell or single-molecule level for guiding antibiotic treatment decisions and predicting therapeutic outcomes.

Resistance Levels and Epidemiology of Non-Fermenting Gram-Negative Bacteria in Urinary Tract Infections of Inpatients and Outpatients (RENFUTI): A 10-Year Epidemiological Snapshot

Background: Urinary tract infections (UTIs) are one of the most common infections in the human medicine, both among outpatients and inpatients. There is an increasing appreciation for the pathogenic role of non-fermenting Gram-negative bacteria (NFGNBs) in UTIs, particularly in the presence of underlying illnesses. Methods: The study was carried out using data regarding a 10-year period (2008-2017). The antimicrobial susceptibility testing was performed using the disk diffusion method, E-tests, and broth microdilution. Results: NFGNB represented 3.46% ± 0.93% for the outpatients, while 6.43% ± 0.81% of all positive urine samples for the inpatients (p < 0.001). In both groups, Pseudomonas spp. (78.7% compared to 85.1%) and Acinetobacter spp. (19.6% compared to 10.9%), were the most prevalent. The Acinetobacter resistance levels were significantly higher in inpatients isolates (p values ranging between 0.046 and <0.001), while the differences in the resistance levels of Pseudomonas was not as pronounced. The β-lactam-resistance levels were between 15-25% and 12-28% for the Acinetobacter and Pseudomonas spp., respectively. 4.71% of Acinetobacter and 1.67% of Pseudomonas were extensively drug resistant (XDR); no colistin-resistant isolates were recovered. Conclusions: Increasing resistance levels of the Acinetobacter spp. from 2013 onward, but not in the case of the Pseudomonas spp. Although rare, the drug resistant NFGNB in UTIs present a concerning therapeutic challenge to clinicians with few therapeutic options left.

Paromomycin production from Streptomyces rimosus NRRL 2455: statistical optimization and new synergistic antibiotic combinations against multidrug resistant pathogens

BACKGROUND

Response surface methodology (RSM) employing Box-Behnken design was used to optimize the environmental factors for the production of paromomycin, a 2 deoxystreptamine aminocyclitol aminoglycoside antibiotic, (2DOS-ACAGA) from Streptomyces (S.) rimosus NRRL 2455. Emergence of bacterial resistance caught our attention to consider the combination of antimicrobial agents. The effect of paromomycin combination with other antimicrobial agents was tested on some multiple drug resistant isolates. To the best of our knowledge, this is the first report on optimization of paromomycin production from S. rimosus NRRL 2455. A Quadratic model and response surface method were used by choosing three model factors; pH, incubation time and inoculum size. A total of 17 experiments were done and the response of each experiment was recorded. Concerning the effect of combining paromomycin with different antimicrobial agents, it was tested using the checkerboard assay against six multidrug resistant (MDR) pathogens including; Pseudomonas (P.) aeruginosa (2 isolates), Klebsiella (K.) pneumoniae, Escherichia (E.) coli, methicillin sensitive Staphylococcus aureus (MSSA) and methicillin resistant Staphylococcus aureus (MRSA). Paromomycin was tested in combination with ceftriaxone, ciprofloxacin, ampicillin/sulbactam, azithromycin, clindamycin and doxycycline.

RESULTS

The optimum conditions for paromomycin production were a pH of 6, an incubation time of 8.5 days and an inoculum size of 5.5% v/v using the optimized media (soybean meal 30 g/L, NH4CL 4 g/L, CaCO3 5 g/L and glycerol 40 ml/L), 28 °C incubation temperature, and 200 rpm agitation rate that resulted in 14 fold increase in paromomycin production as compared to preliminary fermentation level using the basal medium. The tested antibiotic combinations showed either synergistic effect on paromomycin activity on most of the tested MDR pathogens (45.83%), additive effect in 41.67% or indifferent effect in 12.5%.

CONCLUSION

RSM using multifactorial design was a helpful and a reliable method for paromomycin production. Paromomycin combination with ceftriaxone, ciprofloxacin, ampicillin/sulbactam, azithromycin, clindamycin or doxycycline showed mostly synergistic effect on certain selected clinically important MDR pathogens.

Prevalence of Acinetobacter baumannii in Saudi Arabia: risk factors, antimicrobial resistance patterns and mechanisms of carbapenem resistance

Acinetobacter baumannii is an important opportunistic pathogen due to its capabilities for developing mechanisms of resistance to a wide range of antimicrobial agents including carbapenems. This review described the risk factors, antimicrobial susceptibility and mechanisms of carbapenem resistance of A. baumannii from different geographical regions of Saudi Arabia. Several factors including complexity of intensive care unit (ICU) environments, increased numbers of patients with serious diseases, wide spread gastrointestinal colonization and extensive use of antimicrobial drugs led to a wide prevalence of A. baumannii infections in hospitals in Saudi Arabia. A. baumannii has been noted to be less susceptible to antimicrobials agents, including carbapenems, over time, resulting in the evolution of multidrug-resistant (MDR) strains. Dissemination of MDR A. baumannii is attributed to the extreme use of wide-spectrum antimicrobial drugs in hospitals, cross infection between inpatients, invasive ICU procedures, and hospitalized patients with diabetic and cancer those are under frequent invasive diagnostic and therapeutic interventions. Although an increasing prevalence of colistin and tigecycline resistance has been reported in many hospitals, combinations of these agents with carbapenems or other antibiotics remain the best therapeutic choice and reasonably safe to treat patients with MDR A. baumannii infections. The wide distribution of carbapenem resistant A. baumannii (CRAB) due to several mechanisms with diverse genetic determinants has been documented. Although OXA-23 β-lactamase and OXA-51 β-lactamase are the most common genes responsible for CRAB, other novel genes such as blaVIM, PER-1-like and GES-5 have been discovered in carbapenem resistant strains. The high rates of MDR A. baumannii in Saudi hospitals indicate that extensive investigation into the molecular basis of MDR and developing new therapies of CRAB is needed. Moreover, the development of a local antibiogram database coupled with a nationwide antimicrobial stewardship and infection prevention program might help to improve our knowledge of the resistance patterns of A. baumannii, and in developing a treatment protocol for decreasing the infection burden in Saudi Arabia.

Risk factors for hospitalized patients with resistant or multidrug-resistant Pseudomonas aeruginosa infections: a systematic review and meta-analysis

Background

Identifying risk factors predicting acquisition of resistant Pseudomonas aeruginosa will aid surveillance and diagnostic initiatives and can be crucial in early and appropriate antibiotic therapy. We conducted a systematic review examining risk factors of acquisition of resistant P. aeruginosa among hospitalized patients.

Methods

MEDLINE®, EMBASE®, and Cochrane Central were searched between 2000 and 2016 for studies examining independent risk factors associated with acquisition of resistant P. aeruginosa, among hospitalized patients. Random effects model meta-analysis was conducted when at least three or more studies were sufficiently similar.

Results

Of the 54 eligible articles, 28 publications (31studies) examined multi-drug resistant (MDR) or extensively drug resistant (XDR) P. aeruginosa and 26 publications (29 studies) examined resistant P. aeruginosa. The acquisition of MDR P. aeruginosa, as compared with non-MDR P. aeruginosa, was significantly associated with intensive care unit (ICU) admission (3 studies: summary adjusted odds ratio [OR] 2.2) or use of quinolones (4 studies: summary adjusted OR 3.59). Acquisition of MDR or XDR compared with susceptible P. aeruginosa was significantly associated with prior hospital stay (4 studies: summary adjusted OR 1.90), use of quinolones (3 studies: summary adjusted OR 4.34), or use of carbapenems (3 studies: summary adjusted OR 13.68). The acquisition of MDR P. aeruginosa compared with non-P. aeruginosa was significantly associated with prior use of cephalosporins (3 studies: summary adjusted OR 3.96), quinolones (4 studies: summary adjusted OR 2.96), carbapenems (6 studies: summary adjusted OR 2.61), and prior hospital stay (4 studies: summary adjusted OR 1.74). The acquisition of carbapenem-resistant P. aeruginosa compared with susceptible P. aeruginosa, was statistically significantly associated with prior use of piperacillin-tazobactam (3 studies: summary adjusted OR 2.64), vancomycin (3 studies: summary adjusted OR 1.76), and carbapenems (7 studies: summary adjusted OR 4.36).

Conclusions

Prior use of antibiotics and prior hospital or ICU stay was the most significant risk factors for acquisition of resistant P. aeruginosa. These findings provide guidance in identifying patients that may be at an elevated risk for a resistant infection and emphasize the importance of antimicrobial stewardship and infection control in hospitals.

Why Can't We Just Use PCR? The Role of Genotypic versus Phenotypic Testing for Antimicrobial Resistance Testing

There is a need for phenotypic susceptibility testing that is expeditious and that can be performed directly from clinical specimens. While rapid pathogen identification is important, it is the susceptibility result that is essential for antimicrobial optimization. The options for rapid susceptibility testing are limited, with the majority of commercial tests available offering genotypic resistance detection only. In this article, a laboratorian and a clinician discuss the benefits and limitations of genotypic and phenotypic susceptibility testing and provide examples of how results should be interpreted to maximize the clinical utility.

Activity of Simulated Human Dosage Regimens of Meropenem and Vaborbactam against Carbapenem-Resistant Enterobacteriaceae in an In Vitro Hollow-Fiber Model

The objective of these studies was to evaluate the exposures of meropenem and vaborbactam that would produce antibacterial activity and prevent resistance development in carbapenem-resistant Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae strains when tested at an inoculum of 10⁸ CFU/ml. Thirteen K. pneumoniae isolates, three Enterobacter cloacae isolates, and one Escherichia coli isolate were examined in an in vitro hollow-fiber model over 32 h. Simulated dosage regimens of 1 to 2 g of meropenem with 1 to 2 g of vaborbactam, with meropenem administered every 8 h by a 3-h infusion based on phase 1 or phase 3 patient pharmacokinetic data, were studied in the model. A dosage of 2 g of meropenem in combination with 2 g of vaborbactam was bactericidal against K. pneumoniae, E. cloacae, and E. coli strains, with meropenem-vaborbactam MICs of up to 8 mg/liter. When the vaborbactam exposure was adjusted to the levels observed in patients enrolled in phase 3 trials (24-h free AUC, ∼550 mg · h/liter, versus 320 mg · h/liter in the phase 1 studies), 2 g of meropenem with 2 g of vaborbactam was also bactericidal against strains with meropenem-vaborbactam MICs of 16 mg/liter. In addition, this level of vaborbactam also suppressed the development of resistance observed using phase 1 exposures. In this pharmacodynamic model, exposures similar to 2 g of meropenem in combination with 2 g of vaborbactam administered every 8 h by a 3-h infusion in phase 3 trials produced antibacterial activity and suppressed the development of resistance against carbapenem-resistant KPC-producing strains of Enterobacteriaceae.

Activity of Meropenem-Vaborbactam in Mouse Models of Infection Due to KPC-Producing Carbapenem-Resistant Enterobacteriaceae

Meropenem-vaborbactam (Vabomere) is highly active against Gram-negative pathogens, especially Klebsiella pneumoniae carbapenemase (KPC)-producing, carbapenem-resistant Enterobacteriaceae The objective of these studies was to evaluate the efficacy of meropenem alone and in combination with vaborbactam in mouse thigh and lung infection models. Thighs or lungs of neutropenic mice were infected with KPC-producing carbapenem-resistant Enterobacteriaceae, with meropenem MICs ranging from ≤0.06 to 8 mg/liter in the presence of 8 mg/liter vaborbactam. Mice were treated with meropenem alone or meropenem in combination with vaborbactam every 2 h for 24 h to provide exposures comparable to 2-g doses of each component in humans. Meropenem administered in combination with vaborbactam produced bacterial killing in all strains tested, while treatment with meropenem alone either produced less than 0.5 log CFU/tissue of bacterial killing or none at all. In the thigh model, 11 strains were treated with the combination of meropenem plus vaborbactam (300 plus 50 mg/kg of body weight). This combination produced from 0.8 to 2.89 logs of bacterial killing compared to untreated controls at the start of treatment. In the lung infection model, two strains were treated with the same dosage regimen of meropenem and vaborbactam. The combination produced more than 1.83 logs of bacterial killing against both strains tested compared to untreated controls at the start of treatment. Overall, these data suggest that meropenem-vaborbactam may have utility in the treatment of infections due to KPC-producing carbapenem-resistant Enterobacteriaceae.

Simple and Fast Detection of Resistance to Antibiotic Inhibitors of Protein Synthesis in Gram-Negative Pathogens Through Evaluation of Mitomycin C-Induced Cell Elongation

Increasing the resistance of Gram-negative pathogens to antibiotics that inhibit protein synthesis is of great concern. In life-threatening situations, an early detection of antibiotic resistance may improve patient outcome. A rapid assay for the identification of antibiotic resistance to gentamicin, tobramycin, and tigecycline has been designed and tested in clinical strains of Acinetobacter baumannii, Pseudomonas aeruginosa, and the Enterobacteriaceae Escherichia coli and Klebsiella pneumoniae. Exponentially growing cultures were incubated with 0.5 mg/L mitomycin C (MMC) for 2 hr (10 mg/L for A. baumannii), which induced significant cell enlargement as visualized under the microscope. Addition of the appropriate antibiotic dose 15 min before the addition of MMC prevented elongation when the strain was susceptible to the antibiotic, thereby inhibiting protein synthesis. Cell enlargement was not precluded in the antibiotic resistant strains, where protein synthesis had not been successfully inhibited. In comparison with the standard dilution-based antibiogram, the sensitivity of the assay was 100% and the specificity ranged between 96.0% and 100%. Results were obtained after 2 hr and 45 min from exponentially growing cultures. The procedure is easy, reliable, and demonstrates the suitability of the evaluation of simple morphological changes, which are protein synthesis dependent, for the rapid detection of antibiotic resistance.

Can Pharmacokinetic and Pharmacodynamic Principles Be Applied to the Treatment of Multidrug-Resistant Acinetobacter?

OBJECTIVE:

To discuss treatment options that can be used for treatment of Acinetobacter infections.

DATA SOURCES:

A MEDLINE search (1966-November 2010) was conducted to identify English-language literature on pharmacotherapy of Acinetobacter and the bibliographies of pertinent articles. Programs and abstracts from infectious diseases meetings were also searched. Search terms included Acinetobacter, multidrug resistance, pharmacokinetics, pharmacodynamics, Monte Carlo simulation, nosocomial pneumonia, carbapenems, polymyxins, sulbactam, aminoglycosides, tetracyclines, tigecycline, rifampin, and fluoroquinolones.

DATA SELECTION AND DATA EXTRACTION:

All articles were critically evaluated and all pertinent information was included in this review.

DATA SYNTHESIS:

Multidrug resistant (MDR) Acinetobacter, defined as resistance to 3 or more antimicrobial classes, has increased over the past decade. The incidence of carbapenem-resistant Acinetobacter is also increasing, leading to an increased use of dose optimization techniques and/or alternative antimicrobials, which is driven by local susceptibility patterns. However, Acinetobacter infections that are resistant to all commercially available antibiotics have been reported. General principles are available to guide dose optimization of aminoglycosides, β-lactams, fluoroquinolones, and tigecycline for infections due to gram-negative pathogens. Unfortunately, data specific to patients with Acinetobacter infections are limited. Recent pharmacokinetic-pharmacodynamic information has shed light on colistin dosing. The dilemma with colistin is its concentration-dependent killing, which makes once-daily dosing seem like an attractive option, but its short postantibiotic effect limits a clinician's ability to extend the dosing interval. Localized delivery of antimicrobials is also an attractive option due to the ability to increase drug concentration at the infection site while minimizing systemic adverse events, but more data are needed regarding this approach.

CONCLUSIONS:

Increased reliance on dosage optimization, combination therapy, and localized delivery of antimicrobials are methods to pursue positive clinical outcomes in MDR Acinetobacter infections since novel antimicrobials will not be available for several years. Well-designed clinical trials with MDR Acinetobacter are needed to define the best treatment options for these patients.

Observations of resistance through minimum inhibitory concentrations trends for respiratory specimens of commonly isolated organisms

OBJECTIVE

The objective of this study was to determine minimum inhibitory concentration (MIC) trends among common bacterial organisms found in respiratory isolates in the trauma intensive care unit setting.

METHODS

In this retrospective observational study, MIC data was reviewed over a three year period from January 2009 to December 2011 for the three most frequently identified organisms isolated from respiratory specimens in a trauma intensive care unit along with corresponding hospital data.

RESULTS

The most frequently isolated bacterial species identified were Staphylococcus aureus (229 isolates), Pseudomonas aeruginosa (129 isolates), and Acinetobacter species (87 isolates) in the analysis within our institution from 2009-2011. There was considerable variability among the MIC trends for the analyzed organisms. For Pseudomonas isolates, observed sensitivities were as high as 100% for antibiotics ciprofloxacin and imipenem in 2009, but decreased over the next two years in 2010 and 2011. There was considerable variability among the MIC trends for Acinetobacter over the three year period for the antibiotics tested. The MIC data for most Staphylococcus aureus isolates over the three years were sensitive to vancomycin with little change in the observed MIC data.

CONCLUSION

The data reported is observational and indicates the need for future studies to establish a valid relationship of the MIC data over time in our institution particularly among our gram negative organisms, to monitor patterns of antimicrobial resistance.

Clinical and economic impact of meropenem resistance in Pseudomonas aeruginosa-infected patients

BACKGROUND

The emergence of carbapenem resistance has had a significant impact on both clinical and economic outcomes.

METHODS

A retrospective, observational cohort study was performed in a 433-bed tertiary care medical center. The cohort was established from all inpatients with Pseudomonas aeruginosa-positive cultures over a 3-year period. Two multivariate models were developed: a logistic regression model to evaluate the primary outcome of in-hospital mortality and a linear regression model to evaluate the secondary outcome of total hospital cost.

RESULTS

The adjusted odds ratio for in-hospital mortality among patients with meropenem-resistant isolates was 2.89 (95% confidence interval [CI], 1.15-7.28). There were significantly more deaths in the meropenem-resistant group (28.1% vs 8.9%, P = .003). Patients with meropenem-resistant P aeruginosa experienced a 4-day increase in median length of stay versus those in the meropenem-susceptible group (14 vs 9 days, P = .004). Likewise, the percentage of patients who required intensive care unit (ICU) admission increased from 42% to 81.3% (P <.001). Meropenem resistance was also associated with a significant increase in total hospital cost by a factor of 1.42 among patients who were not admitted to the ICU (95% CI, 1.03-1.95).

CONCLUSIONS

Our results demonstrate that meropenem resistance was a significant predictor of in-hospital mortality. Carbapenem resistance also resulted in a significant increase in hospital cost, but only among patients who were not admitted to the ICU.

Fosfomycin antimicrobial prophylaxis for transrectal ultrasound-guided biopsy of the prostate: A prospective randomised study

Objectives

To compare the incidence of infectious complications after single-dose fosfomycin vs. standard fluoroquinolone (FQ)-based prophylaxis in patients undergoing transrectal ultrasound-guided biopsy of the prostate (TRUSBx), as there is an alarming trend worldwide of increasing resistance to FQs limiting their suitability as appropriate prophylaxis for TRUSBx.

Patients and methods

A prospective study was conducted in 412 consecutive patients undergoing TRUSBx between February 2012 and June 2015. Patients were randomly divided into two groups; Group 1 (202 patients) who received single-dose fosfomycin (3 g, orally) 1–2 h before TRUSBx and Group 2 (210 patients) who received routine empirical prophylaxis in the form of oral ciprofloxacin 500 mg and metronidazole 500 mg at least 1 h before TRUSBx and continued this twice daily for 3 days before TRUSBx. We recorded all febrile and afebrile urinary tract infections (UTIs) within the 4 weeks after the procedure.

Results

There was no difference in baseline demographics between the two groups. Total infectious complications occurred in four (1.9%) and 18 (8.5%) patients in Groups 1 and 2, respectively, which was statistically significant (P = 0.001). Escherichia coli was the most common isolated pathogen from urine cultures in all patients with infectious complications (68%). The other isolated bacterium, Klebsiella pneumoniae, was detected in four patients (18%). Urine cultures revealed FQ-resistant strains (73%), all of which were extended-spectrum β-lactamase-producing E. coli and K. pneumoniae.

Conclusions

Single-dose fosfomycin before TRUSBx significantly reduces infectious complications when compared with standard therapy. Fosfomycin is an effective agent for antimicrobial prophylaxis in patients undergoing TRUSBx, particularly in populations where FQ resistance is common.

Is colistin effective in the treatment of infections caused by multidrug-resistant (MDR) or extremely drug-resistant (XDR) gram-negative microorganisms in children?

The increasing incidence of infections caused by multidrug-resistant (MDR) or extremely drug-resistant (XDR) gram-negative organisms has led to the reemergence of colistin use. Clinical and demographic data were collected on 94 pediatric patients diagnosed with MDR or XDR gram-negative infections and treated with either a colistin-containing regimen (colistin group) or at least one antimicrobial agent other than colistin (noncolistin group). The overall clinical response rates were 65.8% in the colistin group and 70.0% in the noncolistin group (P = 0.33). The infection-related mortality rates were 11% in the colistin group and 13.3% in the noncolistin group (P = 0.74). There was no statistically significant difference in nephrotoxicity in the colistin and noncolistin groups. Colistin therapy was at least as effective and as safe as beta-lactam antibiotics or quinolones, with or without aminoglycosides, in the treatment of infections caused by gram-negative organisms and may be a therapeutic option in children.

Antimicrobial susceptibilities of respiratory pathogens in the surgical/trauma intensive care unit compared with the hospital-wide respiratory antibiogram in a level I trauma center

BACKGROUND

Unit-specific antibiograms have developed to guide clinicians to appropriate antibiotic choices for subsets of patients. The additional level of a unit- and respiratory-specific antibiogram for surgical and trauma patients defines key differences in susceptibility information for treating hospital-acquired pneumonia.

METHODS

This was a three-year, retrospective single-center study. A total of 729 positive respiratory specimens from 612 patients were analyzed using Quality Compass Pathfinder(®), the antibiotic-reporting software. Culture and susceptibility reports were compared for the surgical/trauma intensive care unit (S/TICU) and the general hospital (excluding the S/TICU but including the medical ICU [MICU]). Data were filtered to include those genera and organisms with a high association with hospital-acquired pneumonia: Acinetobacter, Citrobacter, Enterobacter, Escherichia coli, Haemophilus, Klebsiella, Neisseria, Pseudomonas, Staphylococcus, Stenotrophomonas, Streptococcus, and Serratia.

RESULTS

For gram-negative organisms, susceptibility differences were noted for Acinetobacter and Pseudomonas between the S/TICU and the rest of the hospital. In particular, Acinetobacter was significantly more susceptible to ciprofloxacin (86% vs. 43%; p<0.001), gentamicin (86% vs. 54%; p=0.001), imipenem-cilastatin (93% vs. 55%; p<0.001), trimethoprim-sulfamethoxazole (88% vs. 54%; p=0.001), and tobramycin (50% vs. 0; p=0.012). Pseudomonas isolates from the S/TICU were significantly more susceptible to aztreonam (83% vs. 68%; p=0.037), ciprofloxacin (86% vs. 69%; p=0.019), and imipenem-cilastatin (94% vs. 79%; p=0.01). For gram-positive organisms, Staphylococcus isolates from the S/TICU were significantly more susceptible to erythromycin (81% vs. 57%; p=0.007) and trimethoprim-sulfamethoxazole (98% vs. 91%; p=0.034) than were the hospital isolates.

CONCLUSIONS

For key respiratory pathogens, such as Pseudomonas, Acinetobacter, and Staphylococcus, surgical and trauma patients present greater susceptibility to several antibiotics. Although this information cannot be extrapolated to other institutions, it does provide a basis for comparable institutions to consider developing unit- and collection-site-specific antibiograms for infections that affect surgical/trauma patients commonly.

Probable Nonconvulsive Status Epilepticus With the Use of High-Dose Continuous Infusion Ceftazidime

Multidrug resistant (MDR) bacterial infections are a major concern of health care providers due to their increasing incidence and associated mortality. In some cases, few or no antibiotics have preserved activity. Beta-lactam administration via continuous infusion can optimize time over minimum inhibitory concentration (MIC). In some cases, use of high-dose continuous infusion (HDCI) may be necessary to achieve serum levels in excess of nonsusceptible MIC values. The use of HDCI beta-lactams is not without risk, specifically neurotoxic adverse effects, which appear dose related. We describe a 64-year-old male who experienced myoclonus and nonconvulsive status epilepticus while receiving HDCI ceftazidime for treatment of multidrug resistant Pseudomonas aeruginosa bacteremia. This report serves as a cautionary example of the potential toxicities associated with HDCI beta-lactams and supports the importance of risk-benefit analysis prior to and during treatment. Additionally, the use of serum drug level monitoring may be necessary to better prevent or predict toxicity.

Establishment and validation of a 384-well antibacterial assay amenable for high-throughput screening and combination testing

A 384-well-based antibacterial assay amenable for high-throughput screening and combination testing is described. The assay uses 100-500nL of test compounds and tolerates up to 2.5% dimethyl sulfoxide concentrations. It can be used for screening compound libraries and testing combinatory/synergistic/antagonistic effects of antibiotics, small molecules, and natural product extracts.

Development and validation of a high-throughput cell-based screen to identify activators of a bacterial two-component signal transduction system

CpxRA is a two-component signal transduction system (2CSTS) found in many drug-resistant Gram-negative bacteria. In response to periplasmic stress, CpxA autophosphorylates and donates a phosphoryl group to its cognate response regulator, CpxR. Phosphorylated CpxR (CpxR-P) upregulates genes involved in membrane repair and downregulates multiple genes that encode virulence factors, which are trafficked across the cell membrane. Mutants that constitutively activate CpxRA in Salmonella enterica serovar Typhimurium and Haemophilus ducreyi are avirulent in mice and humans, respectively. Thus, the activation of CpxRA has high potential as a novel antimicrobial/antivirulence strategy. Using a series of Escherichia coli strains containing a CpxR-P-responsive lacZ reporter and deletions in genes encoding CpxRA system components, we developed and validated a novel cell-based high-throughput screen (HTS) for CpxRA activators. A screen of 36,000 compounds yielded one hit compound that increased reporter activity in wild-type cells. This is the first report of a compound that activates, rather than inhibits, a 2CSTS. The activity profile of the compound against CpxRA pathway mutants in the presence of glucose suggested that the compound inhibits CpxA phosphatase activity. We confirmed that the compound induced the accumulation of CpxR-P in treated cells. Although the hit compound contained a nitro group, a derivative lacking this group retained activity in serum and had lower cytotoxicity than that of the initial hit. This HTS is amenable for the screening of larger libraries to find compounds that activate CpxRA by other mechanisms, and it could be adapted to find activators of other two-component systems.

Ertapenem-Resistant Enterobacteriaceae Risk Factors for Acquisition and Outcomes

Background and Objective.

Carbapenem resistance among Enterobacteriaceae is of concern because of increasing prevalence and limited therapeutic options. Limited research has been focused on understanding ertapenem resistance as a more sensitive marker for resistance to other carbapenems. We sought to determine risk factors for acquisition of ertapenem-resistant, meropenem-susceptible, or intermediate Enterobacteriaceae and to assess associated patient outcomes.

Design.

Retrospective case-control study among adult hospitalized inpatients.

Setting.

A 902-bed quaternary care urban hospital.

Results.

Sixty-two cases of ertapenem-resistant Enterobacteriaceae were identified from March 14, 2006, through October 31, 2007, and 62 unmatched control patients were randomly selected from other inpatients with cultures positive for ertapenem-susceptible Enterobacteriaceae. Thirty-seven (60%) of case patient isolates were Enterobacter cloacae, 20 (32%) were Klebsiella pneumoniae, and 5 (8%) were other species of Enterobacteriaceae. Risk factors for ertapenem-resistant Enterobacteriaceae infection included intensive care unit stay (odds ratio [OR], 4.6 [95% confidence interval {CI}, 2.0–10.3]), vancomycin-resistant Enterococcus colonization (OR, 7.1 [95% CI, 2.4–21.4]), prior central venous catheter use (OR, 10.0 [95% CI, 3.0–33.1]), prior receipt of mechanical ventilation (OR, 5.8 [95% CI, 2.1–16.2]), exposure to any antibiotic during the 30 days prior to a positive culture result (OR, 18.5 [95% CI, 4.9–69.9]), use of a β-lactam during the 30 days prior to a positive culture result (OR, 6.9 [95% CI, 3.0–16.0], and use of a carbapenem during the 30 days prior to a positive culture result (OR, 18.2 [95% CI, 2.6–130.0]). For the 62 case patients, 30-day outcomes from the time of positive culture result were 24 discharges (39%), 10 deaths (16%), and 28 continued hospitalizations (44%). The final end point of the hospitalization was discharge for 44 patients (71%) and death for 18 patients (29%).

Conclusions.

Ertapenem-resistant Enterobacteriaceae are important nosocomial pathogens. Multiple mechanisms of resistance maybe in operation. Additional study of ertapenem resistance is needed.

Variation in definitions and isolation procedures for multidrug-resistant Gram-negative bacteria: a survey of the Society for Healthcare Epidemiology of America Research Network

OBJECTIVE

To assess definitions, experience, and infection control practices for multidrug-resistant gram-negative bacteria (MDR-GNB), including Enterobacteriaceae, Acinetobacter, and Pseudomonas species, in acute care hospitals.

DESIGN

Cross-sectional survey.

PARTICIPANTS

US and international members of the Society for Healthcare Epidemiology of America (SHEA) Research Network.

METHODS

Online survey that included definitions, infection control procedures, and microbiology capability related to MDR-GNB and other MDR bacteria.

RESULTS

From November 2012 through February 2013, 66 of 170 SHEA Research Network members responded (39% response rate), representing 26 states and 15 countries. More than 80% of facilities reported experience with each MDR-GNB isolate, and 78% had encountered GNB resistant to all antibiotics except colistin (62% Acinetobacter, 59% Pseudomonas, and 52% Enterobacteriaceae species). Participants varied regarding their definitions of "multidrug resistant," with 14 unique definitions for Acinetobacter, 18 for Pseudomonas, and 22 for Enterobacteriaceae species. Substantial variation also existed in isolation practices. Although isolation was commonly used for methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and carbapenem-resistant Enterobacteriaceae (CRE), approximately 20% of facilities did not isolate for MDR Pseudomonas or Acinetobacter. The majority of those that isolated MDR organisms also removed isolation using a wide variety of criteria.

CONCLUSION

Facilities vary significantly in their approach to preventing MDR-GNB transmission. Although practices for MRSA and VRE are relatively standardized, emerging pathogens CRE and other MDR-GNB have highly varied definitions and management. This confusion makes communication difficult, and varied use of isolation may contribute to emergence of these organisms. Public health agencies need to promote standard definitions and management to enable broader initiatives to limit emergence of MDR-GNB.

Biofilm-based infections in long-term care facilities

The recent trend in the early admittance to long-term care facilities (LTCFs) of severely injured patients transferred from general hospitals has given a new dynamic to the incidence of healthcare-associated infections, including biofilm-based infections related to the implant of urinary and intravascular catheters, and the onset of pressure ulcers. Catheter-associated urinary tract infections lead in most of the surveys on LTCFs, approximately 80% of urinary tract infections in these settings being due to the short- or long-term insertion of a urinary catheter. Furthermore, the implantation of intravascular catheters is often responsible for catheter-related bloodstream infections caused by the development of an intraluminal biofilm. Pressure ulcers, frequently occurring in bedridden patients admitted to LTCFs, are also susceptible to infection by biofilm-growing aerobic and anaerobic bacteria, the biofilm formation on the wound being the main reason for its delayed healing.

Antibiotic management of complicated intra-abdominal infections in adults: The Asian perspective

Regional epidemiological data and resistance profiles are essential for selecting appropriate antibiotic therapy for intra-abdominal infections (IAIs). However, such information may not be readily available in many areas of Asia and current international guidelines on antibiotic therapy for IAIs are for Western countries, with the most recent guidance for the Asian region dating from 2007. Therefore, the Asian Consensus Taskforce on Complicated Intra-Abdominal Infections (ACT-cIAI) was convened to develop updated recommendations for antibiotic management of complicated IAIs (cIAIs) in Asia. This review article is based on a thorough literature review of Asian and international publications related to clinical management, epidemiology, microbiology, and bacterial resistance patterns in cIAIs, combined with the expert consensus of the Taskforce members. The microbiological profiles of IAIs in the Asian region are outlined and compared with Western data, and the latest available data on antimicrobial resistance in key pathogens causing IAIs in Asia is presented. From this information, antimicrobial therapies suitable for treating cIAIs in patients in Asian settings are proposed in the hope that guidance relevant to Asian practices will prove beneficial to local physicians managing IAIs.

Dual beta-lactam therapy for serious Gram-negative infections: is it time to revisit?

We are rapidly approaching a crisis in antibiotic resistance, particularly among Gram-negative pathogens. This, coupled with the slow development of novel antimicrobial agents, underscores the exigency of redeploying existing antimicrobial agents in innovative ways. One therapeutic approach that was heavily studied in the 1980s but abandoned over time is dual beta-lactam therapy. This article reviews the evidence for combination beta-lactam therapy. Overall, in vitro, animal and clinical data are positive and suggest that beta-lactam combinations produce a synergistic effect against Gram-negative pathogens that rivals that of beta-lactam-aminoglycoside or beta-lactam-fluoroquinolone combination therapy. Although the precise mechanism of improved activity is not completely understood, it is likely attributable to an enhanced affinity to the diverse penicillin-binding proteins found among Gram negatives. The collective data indicate that dual beta-lactam therapy should be revisited for serious Gram-negative infections, especially in light of the near availability of potent beta-lactamase inhibitors, which neutralize the effect of problematic beta-lactamases.

Trends in multidrug-resistant gram-negative bacilli and the role of prolonged β-lactam infusion in the intensive care unit

Multidrug-resistant gram-negative bacilli are emerging threats in the intensive care unit setting worldwide. Extended-spectrum β-lactamases, AmpC β-lactamases, and carbapenem-resistant Enterobacteriaceae are increasing at an alarming rate, leaving limited therapeutic options. In addition, multidrug resistance among Pseudomonas aeruginosa and Acinetobacter baumannii has widely disseminated and become a frequent cause of nosocomial infections within many intensive care units. Therefore, resistance is increasing to all currently available antibiotics, including cephalosporins, penicillins, aztreonam, carbapenems, fluoroquinolones, and aminoglycosides. Some multidrug-resistant gram-negative bacteria remain susceptible to only a few antibiotics such as tigecycline, fosfomycin, and polymyxins. The steady trend of increasing resistance coupled with the lack of novel antibiotics targeting resistant gram-negative bacilli has forced clinicians to increasingly apply more aggressive dosing strategies, such as prolonged and continuous infusion of β-lactam antibiotics to address the challenges associated with these difficult-to-treat pathogens. Nurses who have a thorough understanding of antibiotic resistance patterns, infection control procedures, and appropriate antibiotic use and dosing regimens, particularly the method of administration, are essential in the battle to preserve the usefulness of antibiotics and prevent further antibiotic resistance.

Role of Tigecycline for the Treatment of Urinary Tract Infections

Objective: To review and critically analyze the literature for the use of tigecycline for the treatment of urinary tract infections (UTIs). Data Sources: A search of the MEDLINE database was performed (2004 to July 2013). Search terms included tigecycline, Tygacil, pyelonephritis, cystitis, and urinary tract infections in addition to a manual search of references from the articles retrieved. Study Selection and Data Exaction: All studies of humans, English-language articles, clinical studies, observational studies, and case reports were evaluated. Data Synthesis: Fourteen cases of tigecycline use for UTIs were identified. No clinical trials were identified via the search of the MEDLINE database. Twelve of the 14 cases described positive clinical outcomes with use of tigecycline for the treatment of UTI. Microbiological clearance was evaluable in 11 patients, of which 9 patients achieved documented microbiological clearance. None of the patients had mortality attributable to the use of tigecycline for the UTI. Two of the 14 cases reported had patients with subsequent cultures growing tigecycline-resistant organisms. Conclusion: Case reports have documented clinical improvement/success with the use of tigecycline for the treatment of UTIs. However, use of tigecycline for the treatment of UTIs remains controversial because of limited data and the lack of randomized control trials demonstrating efficacy. Tigecycline should be avoided for the treatment of UTIs when well-established options such as aminoglycosides and β-lactams are available. When alternative options are nonexistent, tigecycline can be considered.

Fosfomycin for the treatment of resistant gram-negative bacterial infections. Insights from the Society of Infectious Diseases Pharmacists

The antimicrobial agent fosfomycin was discovered in 1969, at a time when bacteria had not yet developed extended-spectrum β-lactamases or carbapenemases. Decades later, it is not uncommon for gram-negative organisms to be multidrug-resistant and even pan-resistant to available antibiotic regimens, leaving clinicians with few therapeutic alternatives. Because fosfomycin has been shown to retain activity against these virulent pathogens, there is renewed interest in its use as a therapeutic agent. Fosfomycin formulations including fosfomycin disodium and the newer tromethamine salt are less toxic than other alternatives and are attractive options for resistant gram-negative and gram-positive infections. Oral fosfomycin tromethamine is approved for urinary tract infections in the United States, and an intravenous formulation is also available outside of the United States for systemic disease. The bactericidal action of fosfomycin occurs at an earlier step in cell wall synthesis than that of β-lactam antibiotics. From an in vitro standpoint, fosfomycin generally has high activity against ESBL- and carbapenemase-producing Enterobacteriaceae; multidrug-resistant Pseudomonas aeruginosa susceptibility appears to be more dependent on the local antibiogram. Fosfomycin formulations have a large volume of distribution, penetrate biofilms, and concentrate in the urine. Both oral and intravenous fosfomycin formulations are effective for a wide range of gram-negative infections and disease severities; however, clinical studies are limited. Fosfomycin formulations are well-tolerated, and mild gastrointestinal distress is the most common adverse effect. The primary limitations of fosfomycin are the lack of established regimens for complicated infections and the lack of availability of the intravenous formulation in the United States. Further study of this promising agent seems warranted in the current climate of antibiotic resistance.

Major variation in MICs of tigecycline in Gram-negative bacilli as a function of testing method

Tigecycline is one of the few remaining therapeutic options for extensively drug-resistant (XDR) Gram-negative bacilli (GNB). MICs of tigecycline to Acinetobacter baumannii have been reported to be elevated when determined by the Etest compared to determinations by the broth microdilution (BMD) method. The study aim was to compare the susceptibility of GNB to tigecycline by four different testing methods. GNB were collected from six health care systems (25 hospitals) in southeast Michigan from January 2010 to September 2011. Tigecycline MICs among A. baumannii, carbapenem-resistant Enterobacteriaceae (CRE), extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, and susceptible Enterobacteriaceae isolates were determined by Etest, BMD, Vitek-2, and MicroScan. Nonsusceptibility was categorized as a tigecycline MIC of ≥4 μg/ml for both A. baumannii and Enterobacteriaceae. The study included 4,427 isolates: 2,065 ESBL-producing Enterobacteriaceae, 1,105 A. baumannii, 888 susceptible Enterobacteriaceae, and 369 CRE isolates. Tigecycline nonsusceptibility among A. baumannii isolates was significantly more common as determined by Etest compared to that determined by BMD (odds ratio [OR], 10.3; P<0.001), MicroScan (OR, 12.4; P<0.001), or Vitek-2 (OR, 9.4; P<0.001). These differences were not evident with the other pathogens. Tigecycline MICs varied greatly according to the in vitro testing methods among A. baumannii isolates. Etest should probably not be used by laboratories for tigecycline MIC testing of A. baumannii isolates, since MICs are significantly elevated with Etest compared to those determined by the three other methods.

The Occurrence of blaCTX-M, blaSHV, and blaTEM Genes in Extended-Spectrum β-Lactamase-Positive Strains of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis in Poland

Bacteria belonging to the Enterobacteriaceae family that produce extended-spectrum β-lactamase (ESBL) enzymes are important pathogens of infections. Increasing numbers of ESBL-producing bacterial strains exhibiting multidrug resistance have been observed. The aim of the study was to evaluate the prevalence of blaCTX-M, blaSHV, and blaTEM genes among ESBL-producing Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis strains and to examine susceptibility to antibiotics of tested strains. In our study, thirty-six of the tested strains exhibited blaCTX-M genes (blaCTX-M-15, blaCTX-M-3, blaCTX-M-91, and blaCTX-M-89). Moreover, twelve ESBL-positive strains harbored blaSHV genes (blaSHV-18, blaSHV-7, blaSHV-2, and blaSHV-5), and the presence of a blaTEM gene (blaTEM-1) in twenty-five ESBL-positive strains was revealed. Among K. pneumoniae the multiple ESBL genotype composed of blaCTX-M-15, blaCTX-M-3, blaSHV-18, blaSHV-7, blaSHV-2, and blaSHV-5 genes encoding particular ESBL variants was observed. Analysis of bacterial susceptibility to antibiotics revealed that, among β-lactam antibiotics, the most effective against E. coli strains was meropenem (100%), whereas K. pneumoniae were completely susceptible to ertapenem and meropenem (100%), and P. mirabilis strains were susceptible to ertapenem (91.7%). Moreover, among non-β-lactam antibiotics, gentamicin showed the highest activity to E. coli (91.7%) and ciprofloxacin the highest to K. pneumoniae (83.3%). P. mirabilis revealed the highest susceptibility to amikacin (66.7%).

Management and prevention of ventilator-associated pneumonia caused by multidrug-resistant pathogens

Ventilator-associated pneumonia (VAP) due to multidrug-resistant (MDR) pathogens is a leading healthcare-associated infection in mechanically ventilated patients. The incidence of VAP due to MDR pathogens has increased significantly in the last decade. Risk factors for VAP due to MDR organisms include advanced age, immunosuppression, broad-spectrum antibiotic exposure, increased severity of illness, previous hospitalization or residence in a chronic care facility and prolonged duration of invasive mechanical ventilation. Methicillin-resistant Staphylococcus aureus and several different species of Gram-negative bacteria can cause MDR VAP. Especially difficult Gram-negative bacteria include Pseudomonas aeruginosa, Acinetobacter baumannii, carbapenemase-producing Enterobacteraciae and extended-spectrum β-lactamase producing bacteria. Proper management includes selecting appropriate antibiotics, optimizing dosing and using timely de-escalation based on antiimicrobial sensitivity data. Evidence-based strategies to prevent VAP that incorporate multidisciplinary staff education and collaboration are essential to reduce the burden of this disease and associated healthcare costs.

Host cell cytotoxicity and cytoskeleton disruption by CerADPr, an ADP-ribosyltransferase of Bacillus cereus G9241

Bacillus cereus G9241 was isolated from a welder suffering from an anthrax-like inhalation illness. B. cereus G9241 encodes two megaplasmids, pBCXO1 and pBC210, which are analogous to the toxin- and capsule-encoding virulence plasmids of Bacillus anthracis. Protein modeling predicted that the pBC210 LF homologue contained an ADP-ribosyltransferase (ADPr) domain. This putative bacterial ADP-ribosyltransferase domain was denoted CerADPr. Iterative modeling showed that CerADPr possessed several conserved ADP-ribosyltransferase features, including an α-3 helix, an ADP-ribosyltransferase turn-turn loop, and a "Gln-XXX-Glu" motif. CerADPr ADP-ribosylated an ~120 kDa protein in HeLa cell lysates and intact cells. EGFP-CerADPr rounded HeLa cells, elicited cytoskeletal changes, and yielded a cytotoxic phenotype, indicating that CerADPr disrupts cytoskeletal signaling. CerADPr(E431D) did not possess ADP-ribosyltransferase or NAD glycohydrolase activities and did not elicit a phenotype in HeLa cells, implicating Glu431 as a catalytic residue. These experiments identify CerADPr as a cytotoxic ADP-ribosyltransferase that disrupts the host cytoskeleton.

AFM probing the mechanism of synergistic effects of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) with cefotaxime against extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli

Background

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae poses serious challenges to clinicians because of its resistance to many classes of antibiotics.

Methods and Findings

The mechanism of synergistic activity of a combination of (−)-epigallocatechin-3-gallate (EGCG) and β-lactam antibiotics cefotaxime was studied on Extended-spectrum β-lactamase producing Escherichia coli (ESBL-EC), by visualizing the morphological alteration on the cell wall induced by the combination using atomic force microscopy (AFM). Cells at sub-MICs (sub-minimum inhibitory concentrations) of cefotaxime were initially filamentated but recovered to the normal shape later, whereas cells at sub-MICs of EGCG experienced temporal disturbance on the cell wall such as leakage and release of cellular debris and groove formation, but later recovered to the normal shape. In contrast, the combination of cefotaxime and EGCG at their respective sub-MICs induced permanent cellular damages as well as continuous elongation in cells and eventually killed them. Flow cytometry showed that intracellular oxidative stress levels in the cell treated with a combination of EGCG and cefotaxime at sub-MICs were higher than those in the cells treated with either cefotaxime or EGCG at sub-MICs.

Conclusions

These results suggest that the synergistic effect of EGCG between EGCG and cefotaxime against ESBL-EC is related to cooperative activity of exogenous and endogenous reactive oxygen species (ROS) generated by EGCG and cefotaxime, respectively.

Diphosphonium ionic liquids as broad-spectrum antimicrobial agents

PURPOSE

One of the most disturbing trends in recent years is the growth of resistant strains of bacteria with the simultaneous dearth of new antimicrobial agents. Thus, new antimicrobial agents for the use on the ocular surface are needed.

METHODS

We synthesized a variety of ionic liquid compounds, which possess 2 positively charged phosphonium groups separated by 10 methylene units in a "bola"-type configuration. We tested these compounds for antimicrobial activity versus a variety of ocular pathogens, as well as their cytoxicity, in vitro in a corneal cell line and in vivo in mice.

RESULTS

The ionic liquid Di-Hex C10 demonstrated broad in vitro antimicrobial activity at low micromolar concentrations versus gram-negative and gram-positive organisms, including methicillin-resistant Staphylococcus aureus strains and ocular fungal pathogens. Treatment with Di-Hex C10 resulted in bacterial killing in as little as 15 minutes in vitro. Di-Hex C10 showed little cytotoxicity at 1 μM versus a corneal epithelial cell line or at 10 μM in a mouse corneal wound model. We also show that this bis-phosphonium ionic liquid structure is a key because a comparable monophosphonium ionic liquid is cytotoxic to both bacteria and corneal epithelial cells.

CONCLUSIONS

Here, we report the first use of dicationic bis-phosphonium ionic liquids as antimicrobial agents. Our data suggest that diphosphonium ionic liquids may represent a new class of broad-spectrum antimicrobial agents for the use on the ocular surface.

Pharmacodynamics of doripenem in critically ill patients with ventilator-associated Gram-negative bacilli pneumonia

Several pathophysiological changes in critically ill patients are important in determining the therapeutic success of β-lactam antibiotics. The aim of this study was to assess the population pharmacokinetics and probabilities of target attainment (PTAs) of doripenem in patients with ventilator-associated pneumonia, comparing administration by 1-h and 4-h infusion. Patients were randomised into two groups: Group I received a 1-h infusion of 0.5 g every 8 h (q8h) for seven doses; and Group II received a 4-h infusion of 0.5 g q8h for seven doses. A Monte Carlo simulation was performed to determine the PTAs. PTAs of achieving 40% T(>MIC) [exposure time during which the free drug concentration remains above the minimum inhibitory concentration (MIC)] and 75% T(>MIC) are required for effective bactericidal activity of this agent in immunocompetent and immunocompromised hosts, respectively. Values of volume of distribution and total clearance of doripenem in these patients were 17.26±1.83 L and 24.89±1.63 L/h, respectively. For pathogens with a MIC of 1 μg/mL, the PTAs of achieving 40% T(>MIC) following administration of doripenem by a 1-h and 4-h infusion of 0.5 g q8h were 92.95% and 98.32%, respectively. For pathogens with a MIC of 2 μg/mL in immunocompromised hosts, the PTAs of achieving 80% T(>MIC) following administration of doripenem by 1-h and 4-h infusion of 2 g q8h were 56.57% and 91.21%, respectively. In conclusion, these findings indicated that higher than recommended doses in this patient population, particularly neutropenic patients, would be necessary to optimise the pharmacokinetics of doripenem.

Hospital costs of nosocomial multi-drug resistant Pseudomonas aeruginosa acquisition

Background

We aimed to assess the hospital economic costs of nosocomial multi-drug resistant Pseudomonas aeruginosa acquisition.

Methods

A retrospective study of all hospital admissions between January 1, 2005, and December 31, 2006 was carried out in a 420-bed, urban, tertiary-care teaching hospital in Barcelona (Spain). All patients with a first positive clinical culture for P. aeruginosa more than 48 h after admission were included. Patient and hospitalization characteristics were collected from hospital and microbiology laboratory computerized records. According to antibiotic susceptibility, isolates were classified as non-resistant, resistant and multi-drug resistant. Cost estimation was based on a full-costing cost accounting system and on the criteria of clinical Activity-Based Costing methods. Multivariate analyses were performed using generalized linear models of log-transformed costs.

Results

Cost estimations were available for 402 nosocomial incident P. aeruginosa positive cultures. Their distribution by antibiotic susceptibility pattern was 37.1% non-resistant, 29.6% resistant and 33.3% multi-drug resistant. The total mean economic cost per admission of patients with multi-drug resistant P. aeruginosa strains was higher than that for non-resistant strains (15,265 vs. 4,933 Euros). In multivariate analysis, resistant and multi-drug resistant strains were independently predictive of an increased hospital total cost in compared with non-resistant strains (the incremental increase in total hospital cost was more than 1.37-fold and 1.77-fold that for non-resistant strains, respectively).

Conclusions

P. aeruginosa multi-drug resistance independently predicted higher hospital costs with a more than 70% increase per admission compared with non-resistant strains. Prevention of the nosocomial emergence and spread of antimicrobial resistant microorganisms is essential to limit the strong economic impact.

Infectious diseases in the critically ill patients

Infection is common in the critically ill and often results due to the severity of the patient's illness. Recent data suggest 51% of intensive care unit (ICU) patients are infected, and 71% receive antimicrobial therapy. Bacterial infection is the primary concern, although some fungal infections are opportunistic. Infection more than doubles the ICU mortality rate, and the costs associated with infection may be as high as 40% of total ICU expenditures. There are many contemporary antimicrobial resistance concerns that the critical care clinician must consider in managing the pharmacotherapy of infection. Methicillin resistance in Staphylococcus aureus, vancomycin resistance in Enterococci, beta-lactamase resistance in Enterobacteriaceae, multidrug resistance in Pseudomonas aeruginosa and Acinetobacter species, fluoroquinolone resistance in Escherichia coli, and fungal resistance are among the most common issues ICU clinician's must face in managing infection. Critical illness causes changes in pharmacokinetics that influence drug and dosing considerations. Absorption, distribution, metabolism, and excretion may all be affected by the various disease states that define critical illness. Several specific diseases are discussed, including ventilator-associated pneumonia, various fungal infections, gastrointestinal infections due to Clostridium difficile, urinary tract infections, and bloodstream infections. Within each disease section, discussion includes causes and prevention strategies, microbiology, evidence-based guidelines, and important caveats.