Antimicrobial susceptibility of Gram-negative organisms isolated from patients hospitalised with pneumonia in US and European hospitals: results from the SENTRY Antimicrobial Surveillance Program, 2009-2012

Increasing relevance of Gram-positive cocci in urinary tract infections: a 10-year analysis of their prevalence and resistance trends

Urinary tract infections (UTIs) are the third most common types of infection in human medicine worldwide. There is increasing appreciation for the pathogenic role of Gram-positive cocci (GPC) in UTIs, as they have a plethora of virulence factors, maintaining their pathogenicity and high affinity for the epithelial cells of the urinary tract. The study was carried out using microbiological data collected corresponding to the period between 2008 and 2017. Antimicrobial susceptibility testing was performed using the disk diffusion method and E-tests. The age range of patients affected from the outpatient and inpatient groups differed significantly (43 [range 0.7–99] vs. 68 [range 0.4–99] years; p = 0.008). 3962 GPCs were obtained from inpatient and 4358 from outpatient samples, corresponding to 20.5 ± 2.8% (range 17.5–26.8%) and 20.6 ± 2.6% (range 17.8–26.0%) of all positive urine samples (p > 0.05); in both groups, Enterococcus spp. were the most prevalent (outpatients: 79.6%; inpatients: 88.5%). High-level aminoglycoside resistance in enterococci was noted in 31.0–46.6% of cases. A pronounced increase in the number of MRSA was seen in the second half of the study period (0.6–1.9% vs. 9.8–11.6%; p = 0.038). The ratio of VRE isolates was 0.16%, no VISA/VRSA isolates were detected.

Therapeutic Efficacy of Novel Antimicrobial Peptide AA139-Nanomedicines in a Multidrug-Resistant Klebsiella pneumoniae Pneumonia-Septicemia Model in Rats

Antimicrobial peptides (AMPs) have seen limited clinical use as antimicrobial agents, largely due to issues relating to toxicity, short biological half-life, and lack of efficacy against Gram-negative bacteria. However, the development of novel AMP-nanomedicines, i.e., AMPs entrapped in nanoparticles, has the potential to ameliorate these clinical problems. The authors investigated two novel nanomedicines based on AA139, an AMP currently in development for the treatment of multidrug-resistant Gram-negative infections. AA139 was entrapped in polymeric nanoparticles (PNPs) or lipid-core micelles (MCLs). The antimicrobial activity of AA139-PNP and AA139-MCL was determined in vitro The biodistribution and limiting doses of AA139-nanomedicines were determined in uninfected rats via endotracheal aerosolization. The early bacterial killing activity of the AA139-nanomedicines in infected lungs was assessed in a rat model of pneumonia-septicemia caused by extended-spectrum β-lactamase-producing Klebsiella pneumoniae In this model, the therapeutic efficacy was determined by once-daily (q24h) administration over 10 days. Both AA139-nanomedicines showed equivalent in vitro antimicrobial activities (similar to free AA139). In uninfected rats, they exhibited longer residence times in the lungs than free AA139 (∼20% longer for AA139-PNP and ∼80% longer for AA139-MCL), as well as reduced toxicity, enabling a higher limiting dose. In rats with pneumonia-septicemia, both AA139-nanomedicines showed significantly improved therapeutic efficacy in terms of an extended rat survival time, although survival of all rats was not achieved. These results demonstrate potential advantages that can be achieved using AMP-nanomedicines. AA139-PNP and AA139-MCL may be promising novel therapeutic agents for the treatment of patients suffering from multidrug-resistant Gram-negative pneumonia-septicemia.

Geographical and temporal variation in the frequency and antimicrobial susceptibility of bacteria isolated from patients hospitalized with bacterial pneumonia: results from 20 years of the SENTRY Antimicrobial Surveillance Program (1997-2016)

BACKGROUND

The SENTRY Antimicrobial Surveillance Program monitors the frequency of occurrence and antimicrobial susceptibility of organisms from various infection types worldwide.

METHODS

A total of 102 995 bacterial isolates were consecutively collected (one per patient) in 1997-2016 from 258 medical centres in North America (n = 44 999; 113 centres), Europe (n = 30 988; 61 centres from 22 nations), the Asia-Pacific region (APAC; n = 16 503; 67 centres from 12 nations) and Latin America (n = 10 505; 17 centres from 7 nations). Organisms were isolated from respiratory tract specimens and tested for susceptibility by broth microdilution methods in a central laboratory.

RESULTS

Staphylococcus aureus (n = 24 351) and Pseudomonas aeruginosa (n = 22 279) were the most common organisms overall. Klebsiella spp. (n = 10 565) ranked third in North America, Europe and APAC. The proportion of Gram-negatives increased from 70.0%-74.7% to 80.9%-82.6% in Europe, APAC and Latin America, and remained stable (65.5%-66.1%) in North America. Methicillin resistance rates decreased substantially in all four regions from 2005-06 to 2015-16 among S. aureus isolates. P. aeruginosa susceptibility to meropenem decreased overall in the initial years, but increased in the last years of the investigation. Among Klebsiella spp. isolates, susceptibility to ceftriaxone/meropenem decreased from 85.9%/99.3% to 58.6%/85.8% in Europe and from 91.8%/99.5% to 81.6%/93.9% in APAC during the study period.

CONCLUSIONS

Rank order and susceptibility rates varied widely by geographical region and over time. The occurrence of some resistance phenotypes increased, though others decreased over the 20 years of the SENTRY Antimicrobial Surveillance Program.

Ceftazidime-Avibactam in Combination With Fosfomycin: A Novel Therapeutic Strategy Against Multidrug-Resistant Pseudomonas aeruginosa

Previously, by targeting penicillin-binding protein 3, Pseudomonas-derived cephalosporinase (PDC), and MurA with ceftazidime-avibactam-fosfomycin, antimicrobial susceptibility was restored among multidrug-resistant (MDR) Pseudomonas aeruginosa. Herein, ceftazidime-avibactam-fosfomycin combination therapy against MDR P. aeruginosa clinical isolate CL232 was further evaluated. Checkerboard susceptibility analysis revealed synergy between ceftazidime-avibactam and fosfomycin. Accordingly, the resistance elements present and expressed in P. aeruginosa were analyzed using whole-genome sequencing and transcriptome profiling. Mutations in genes that are known to contribute to β-lactam resistance were identified. Moreover, expression of blaPDC, the mexAB-oprM efflux pump, and murA were upregulated. When fosfomycin was administered alone, the frequency of mutations conferring resistance was high; however, coadministration of fosfomycin with ceftazidime-avibactam yielded a lower frequency of resistance mutations. In a murine infection model using a high bacterial burden, ceftazidime-avibactam-fosfomycin significantly reduced the P. aeruginosa colony-forming units (CFUs), by approximately 2 and 5 logs, compared with stasis and in the vehicle-treated control, respectively. Administration of ceftazidime-avibactam and fosfomycin separately significantly increased CFUs, by approximately 3 logs and 1 log, respectively, compared with the number at stasis, and only reduced CFUs by approximately 1 log and 2 logs, respectively, compared with the number in the vehicle-treated control. Thus, the combination of ceftazidime-avibactam-fosfomycin was superior to either drug alone. By employing a "mechanism-based approach" to combination chemotherapy, we show that ceftazidime-avibactam-fosfomycin has the potential to offer infected patients with high bacterial burdens a therapeutic hope against infection with MDR P. aeruginosa that lack metallo-β-lactamases.

Increased financial burdens and lengths of stay in patients with healthcare-associated infections due to multidrug-resistant bacteria in intensive care units: A propensity-matched case-control study

Background and objectives

Incidence rates of healthcare-associated infections (HAIs) depend upon infection control policy and practices, and the effectiveness of the implementation of antibiotic stewardship. Amongst intensive care unit (ICU) patients with HAIs, a substantial number of pathogens were reported to be multidrug-resistant bacteria (MDRB). However, impacts of ICU HAIs due to MDRB (MDRB-HAIs) remain understudied. Our study aimed to evaluate the negative impacts of MRDB-HAIs versus HAIs due to non-MDRB (non-MRDB-HAIs).

Methods

Among 60,317 adult patients admitted at ICUs of a 2680-bed medical centre in Taiwan between January 2010 and December 2017, 279 pairs of propensity-score matched MRDB-HAI and non-MRDB-HAI were analyzed.

Principal findings

Between the MDRB-HAI group and the non-MDRB-HAI group, significant differences were found in overall hospital costs, costs of medical and nursing services, medication, and rooms/beds, and in ICU length-of-stay (LOS). As compared with the non-MDRB-HAI group, the mean of the overall hospital costs of patients in the MDRB-HAI group was increased by 26%; for categorized expenditures, the mean of costs of medical and nursing services of patients in the MDRB-HAI group was increased by 8%, of medication by 26.9%, of rooms/beds by 10.3%. The mean ICU LOS in the MDRB-HAI group was increased by 13%. Mortality rates in both groups did not significantly differ.

Conclusions

These data clearly demonstrate more negative impacts of MDRB-HAIs in ICUs. The quantified financial burdens will be helpful for hospital/government policymakers in allocating resources to mitigate MDRB-HAIs in ICUs; in case of need for clarification/verification of the medico-economic burdens of MDRB-HAIs in different healthcare systems, this study provides a model to facilitate the evaluations.

Global priority pathogens: virulence, antimicrobial resistance and prospective treatment options

Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Salmonella spp. are part of a group of pathogens that pose a major threat to human health due to the emergence of multidrug-resistant strains. Moreover, these bacteria have several virulence factors that allow them to successfully colonize their hosts, such as toxins and the ability to produce biofilms, resulting in an urgent need to develop new strategies to fight these pathogens. In this review, we compile the most up-to-date information on the epidemiology, virulence and resistance of these clinically important microorganisms. Additionally, we address new therapeutic alternatives, with a focus on molecules with antivirulence activity, which are considered promising to combat multidrug-resistant bacteria.

A 10-year single-center experience on Stenotrophomonas maltophilia resistotyping in Szeged, Hungary

Stenotrophomonas maltophilia is an aerobic, oxidase-negative and catalase-positive bacillus. S. maltophilia is a recognized opportunistic pathogen. Due to the advancements in invasive medical procedures, organ transplantation and chemotherapy of malignant illnesses, the relevance of this pathogen increased significantly. The therapy of S. maltophilia infections is challenging, as these bacteria show intrinsic resistance to multiple classes of antibiotics, the first-choice drug is sulfamethoxazole/trimethoprim. Our aim was to assess the epidemiology of S. maltophilia from various clinical samples and the characterization of resistance-levels and resistotyping of these samples over a long surveillance period. The study included S. maltophilia bacterial isolates from blood culture samples, respiratory samples and urine samples and the data for the samples, received between January 2008 until December 2017, a total of 817 S. maltophilia isolates were identified (respiratory samples n = 579, 70.9%, blood culture samples n = 175, 21.4% and urine samples n = 63, 7.7%). Levofloxacin and colistin-susceptibility rates were the highest (92.2%; n = 753), followed by tigecycline (90.5%, n = 739), the first-line agent sulfamethoxazole/trimethoprim (87.4%, n = 714), while phenotypic resistance rate was highest for amikacin (72.5% of isolates were resistant, n = 592). The clinical problem of sulfamethoxazole/trimethoprim-resistance is a complex issue, because there is no guideline available for the therapy of these infections.

The Burden of Bloodstream Infections due to Stenotrophomonas Maltophilia in the United States: A Large, Retrospective Database Study

Background

Stenotrophomonas maltophilia is an opportunistic pathogen observed in both nosocomial and community-onset infections. S. maltophilia is intrinsically resistant to many currently available broad-spectrum antibiotics and is often not included in antimicrobial resistance surveillance studies or stewardship programs’ guidelines.

Methods

A retrospective cohort study of patients with S. maltophilia bloodstream infection (BSI) in the United States was conducted using the 2010–2015 US Premier Healthcare Database. This study described patient characteristics, infection characteristics, antibiotic treatment, and discharge status.

Results

S. maltophilia was the most common carbapenem-resistant, gram-negative pathogen causing BSIs in this database. Of 486 unique patients with S. maltophilia BSI, 44.6% were assessed as community-onset, 95% of cultures were susceptible to trimethoprim-sulfamethoxazole (TMP-SMX), and 84% were susceptible to fluoroquinolones; 39.1% of patients received a potentially effective antibiotic (fluoroquinolone, doxycycline, ceftazidime, minocycline, or TMP-SMX) during the empiric treatment period (≤3 days post–index culture date), whereas 85.8% received a potential effective antibiotics during the definitive treatment period. The most common antibiotic received as definitive treatment was levofloxacin (48.9%). TMP-SMX was used infrequently empirically (10.5%) and in 38.3% during the definitive period. Compared with BSIs caused by other carbapenem-resistant gram-negative pathogens, S. maltophilia BSIs were more likely to be community-onset, and were more likely to be discharged to home and to have a lower mortality rate.

Conclusions

This study demonstrated that patients at risk for S. maltophilia BSI are highly variable and that standard of care is not clearly defined, leading to questions regarding the appropriateness of antibiotic treatment among patients. Further efforts are needed to better recognize and treat S. maltophilia BSI.

Contributing Factors to the Clinical and Economic Burden of Patients with Laboratory-Confirmed Carbapenem-Nonsusceptible Gram-Negative Respiratory Infections

PURPOSE

This study examined patient- and hospital-level predictor variables that contribute to worse clinical and economic outcomes in patients with carbapenem-nonsusceptible respiratory infections.

PATIENTS AND METHODS

Electronic data (January 2013 to September 2015) were from 78 US hospitals. Nonduplicate, gram-negative respiratory isolates were considered carbapenem-nonsusceptible if they tested resistant/intermediate to imipenem, meropenem, doripenem, or ertapenem. Potential predictors of outcomes (in-hospital mortality, 30-day readmission, length of stay [LOS], hospital total cost, and net gain/loss per patient) were examined using univariate analysis and generalized linear mixed models. Statistical significance and model goodness-of-fit criteria were used to identify significant predictors.

RESULTS

A total of 1488 carbapenem-nonsusceptible respiratory patients were identified. Overall, the mortality rate was 13.7%, 30-day readmission rate was 20.6%, mean LOS was 20 days, mean total cost was $54,158, and mean net loss was $139 per patient. Our models showed that hospital-onset infection, higher clinical severity, mechanical ventilation/intensive care unit status, polymicrobial infection, and underlying diseases were all significant predictors for mortality, LOS, and total cost. Hospital-onset infections were also associated with a significantly greater net loss (P≤.01), and underlying disease significantly impacted readmissions (P=.03). The number of prior admissions, hospital characteristics, and payer type were also found to significantly impact measured outcomes.

CONCLUSION

Carbapenem-nonsusceptible respiratory infections are associated with a considerable clinical and economic burden. The impact of hospital-onset infections on both clinical and economic outcomes highlights the continued need for action on this modifiable risk factor through antimicrobial stewardship and optimal therapy, thereby reducing the burden in this patient population.

Attributable burden in patients with carbapenem-nonsusceptible gram-negative respiratory infections

Objective

We aimed to describe the clinical and economic burden attributable to carbapenem-nonsusceptible (C-NS) respiratory infections.

Methods

This retrospective matched cohort study assessed clinical and economic outcomes of adult patients (aged ≥18 years) who were admitted to one of 78 acute care hospitals in the United States with nonduplicate C-NS and carbapenem-susceptible (C-S) isolates from a respiratory source. A subset analysis of patients with principal diagnosis codes denoting bacterial pneumonia or other diagnoses was also conducted. Isolates were classified as community- or hospital-onset based on collection time. A generalized linear mixed model method was used to estimate the attributable burden for mortality, 30-day readmission, length of stay (LOS), cost, and net gain/loss (payment minus cost) using propensity score-matched C-NS versus C-S cohorts.

Results

For C-NS cases, mortality (25.7%), LOS (29.4 days), and costs ($81,574) were highest in the other principal diagnosis, hospital-onset subgroup; readmissions (19.4%) and net loss (-$9522) were greatest in the bacterial pneumonia, hospital-onset subgroup. Mortality and readmissions were not significantly higher for C-NS cases in any propensity score-matched subgroup. Significant C-NS–attributable burden was found for both other principal diagnosis subgroups for LOS (hospital-onset: 3.7 days, P = 0.006; community-onset: 1.5 days, P<0.001) and cost (hospital-onset: $12,777, P<0.01; community-onset: $2681, P<0.001).

Conclusions

Increased LOS and cost burden were observed in propensity score-matched patients with C-NS compared with C-S respiratory infections; the C-NS–attributable burden was significant only for patients with other principal diagnoses.

Stenotrophomonas maltophilia susceptibility to ceftazidime-avibactam combination versus ceftazidime alone

OBJECTIVE

To compare the minimum inhibitory concentrations (MIC) of the ceftazidime-avibactam (CZA) combination versus ceftazidime alone (TZ) for Stenotrophomonas maltophilia.

PATIENTS AND METHODS

MIC comparison was performed by E-tests. We assumed that CZA was more effective in vitro than TZ alone when CZA led to a category change from "Resistant" with TZ alone to "Susceptible" or "Intermediate" with CZA, or if the MIC of CZA was at least 4-fold lower than the MIC of TZ for TZ-susceptible isolates.

RESULTS

For the 54 clinical isolates included in the study, CZA showed better results in terms of the proportion of susceptible isolates (66.7% vs. 38.9%, P<0.01), MIC₅₀ (2μg/mL vs. 12μg/mL, P<0.05), and MIC distribution. According to our definition, CZA was also more effective in vitro than TZ alone for 50% of the isolates.

CONCLUSION

Using CZA for empirical treatments in severe or polymicrobial infections with S. maltophilia seems appropriate.

The Role of Gram-Negative Bacteria in Urinary Tract Infections: Current Concepts and Therapeutic Options

Urinary tract infections (UTIs) are some of the most common infections in human medicine worldwide, recognized as an important public health concern to healthcare systems around the globe. In addition, urine specimens are one of the most frequently submitted samples for culture to the clinical microbiology laboratory, exceeding the number of most of the other sample types. The epidemiology, species-distribution and susceptibility-patterns of uropathogens vary greatly in a geographical and time-dependent manner and it also strongly correlated with the reported patient population studied. Nevertheless, many studies highlight the fact that the etiological agents in UTIs have changed considerably, both in nosocomial and community settings, with a shift towards "less common" microorganisms having more pronounced roles. There is increasing demand for further research to advance diagnostics and treatment options, and to improve care of the patients. The aim of this review paper was to summarize current developments in the global burden of UTI, the diagnostic aspects of these infectious pathologies, the possible etiological agents and their virulence determinants (with a special focus on the members of the Enterobacterales order), current guidelines and quality indicators in the therapy of UTIs and the emergence of multidrug resistance in urinary pathogens.

Selecting the dosage of ceftazidime-avibactam in the perfect storm of nosocomial pneumonia

PURPOSE

Ceftazidime-avibactam is a novel β-lactam/β-lactamase inhibitor combination recently approved in Europe and the USA for the treatment of adults with hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), among other indications. In the phase III REPROVE trial (NCT01808092), ceftazidime-avibactam demonstrated non-inferiority to meropenem for the treatment of patients with nosocomial pneumonia (NP), including VAP. As ceftazidime-avibactam was not studied in patients with NP prior to REPROVE, selecting an appropriate dosage regimen in the "perfect storm" of NP required careful consideration of potential determinants and confounders of response specific to the NP patient population.

METHODS

This review describes the series of preclinical studies and pharmacokinetic/pharmacodynamic (PK/PD) analyses that supported ceftazidime-avibactam dosage selection for patients with NP/VAP (2000/500 mg by 2-h intravenous infusion every 8 h, adjusted for renal function). In parallel, important considerations for antibiotic dosage selection in patients with NP are highlighted, including adequate drug penetration into the lungs, the suitability of murine-derived plasma PK/PD targets, evaluation of MIC distributions against clinical bacterial isolates from patients with NP, and consideration of PK in patients with NP, who are often critically ill. These analyses also supported the European approval of ceftazidime-avibactam for adults with HAP, including VAP, before the completion of REPROVE.

CONCLUSIONS

This work serves as a successful practical example of dosage design for a new antibacterial drug therapy in the indication of NP, including VAP, where previous drug therapies have failed, possibly as a result of evaluation of too few variables, thereby limiting the accuracy of pharmacodynamic predictions.

Outcomes of Stenotrophomonas maltophilia hospital-acquired pneumonia in intensive care unit: a nationwide retrospective study

Background

There is little descriptive data on Stenotrophomonas maltophilia hospital-acquired pneumonia (HAP) in critically ill patients. The optimal modalities of antimicrobial therapy remain to be determined. Our objective was to describe the epidemiology and prognostic factors associated with S. maltophilia pneumonia, focusing on antimicrobial therapy.

Methods

This nationwide retrospective study included all patients admitted to 25 French mixed intensive care units between 2012 and 2017 with hospital-acquired S. maltophilia HAP during intensive care unit stay. Primary endpoint was time to in-hospital death. Secondary endpoints included microbiologic effectiveness and antimicrobial therapeutic modalities such as delay to appropriate antimicrobial treatment, mono versus combination therapy, and duration of antimicrobial therapy.

Results

Of the 282 patients included, 84% were intubated at S. maltophilia HAP diagnosis for duration of 11 [5–18] days. The Simplified Acute Physiology Score II was 47 [36–63], and the in-hospital mortality was 49.7%. Underlying chronic pulmonary comorbidities were present in 14.1% of cases. Empirical antimicrobial therapy was considered effective on S. maltophilia according to susceptibility patterns in only 30% of cases. Delay to appropriate antimicrobial treatment had, however, no significant impact on the primary endpoint. Survival analysis did not show any benefit from combination antimicrobial therapy (HR = 1.27, 95%CI [0.88; 1.83], p = 0.20) or prolonged antimicrobial therapy for more than 7 days (HR = 1.06, 95%CI [0.6; 1.86], p = 0.84). No differences were noted in in-hospital death irrespective of an appropriate and timely empiric antimicrobial therapy between mono- versus polymicrobial S. maltophilia HAP (p = 0.273). The duration of ventilation prior to S. maltophilia HAP diagnosis and ICU length of stay were shorter in patients with monomicrobial S. maltophilia HAP (p = 0.031 and p = 0.034 respectively).

Conclusions

S. maltophilia HAP occurred in severe, long-stay intensive care patients who mainly required prolonged invasive ventilation. Empirical antimicrobial therapy was barely effective while antimicrobial treatment modalities had no significant impact on hospital survival.

Trial registration

clinicaltrials.gov, NCT03506191

Treatment Options for Carbapenem-resistant Gram-negative Bacterial Infections

Antimicrobial resistance has become one of the greatest threats to public health, with rising resistance to carbapenems being a particular concern due to the lack of effective and safe alternative treatment options. Carbapenem-resistant gram-negative bacteria of clinical relevance include the Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii, and more recently, Stenotrophomonas maltophilia. Colistin and tigecycline have been used as first-line agents for the treatment of infections caused by these pathogens; however, there are uncertainties regarding their efficacy even when used in combination with other agents. More recently, several new agents with activity against certain carbapenem-resistant pathogens have been approved for clinical use or are reaching late-stage clinical development. They include ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, plazomicin, eravacycline, and cefiderocol. In addition, fosfomycin has been redeveloped in a new intravenous formulation. Data regarding the clinical efficacy of these new agents specific to infections caused by carbapenem-resistant pathogens are slowly emerging and appear to generally favor newer agents over previous best available therapy. As more treatment options become widely available for carbapenem-resistant gram-negative infections, the role of antimicrobial stewardship will become crucial in ensuring appropriate and rationale use of these new agents.

Ventilator-associated pneumonia due to Stenotrophomonas maltophilia: Risk factors and outcome

BACKGROUND

Stenotrophomonas maltophilia (SM) is increasingly identified in intensive care unit (ICU). This study aim to identify risk factors for SM ventilator-associated pneumonia (VAP) and whether it affects ICU mortality METHODS: Two nested matched case-control studies were performed based in OUTCOMEREA database. The first episodes of SM-VAP patients were matched with two different control groups: VAP due to other micro-organisms (VAP-other) and Pseudomonas aeruginosa VAP (Pyo-VAP). Matching criteria were the hospital, the SAPS II, and the previous duration of mechanical ventilation (MV).

RESULTS

Of the 102 SM-VAP patients (6.2% of all VAP patients), 92 were matched with 375 controls for the SM-VAP/other-VAP matching and 84 with 237 controls for the SM-VAP/Pyo-VAP matching. SM-VAP risk factors were an exposition to ureido/carboxypenicillin or carbapenem during the week before VAP, and respiratory and coagulation components of SOFA score upper to 2 before VAP. SM-VAP received early adequate therapy in 70 cases (68.6%). Risk factors for Day-30 were age (OR = 1.03; p < 0.01) and Chronic heart failure (OR = 3.15; p < 0.01). Adequate treatment, either monotherapy or combination of antimicrobials, did not modify mortality. There was no difference in 30-day mortality, but 60-day mortality was higher in patients with SM-VAP compared to Other-VAP (P = 0.056).

CONCLUSIONS

In a large series, independent risk factors for the SM-VAP were ureido/carboxypenicillin or carbapenem exposure the week before VAP, and respiratory and coagulation components of the SOFA score > 2 before VAP. Mortality risk factors of SM-VAP were age and chronic heart failure. Adequate treatment did not improve SM-VAP prognosis.

Comparative In Vivo Antibacterial Activity of Human-Simulated Exposures of Cefiderocol and Ceftazidime against Stenotrophomonas maltophilia in the Murine Thigh Model

Cefiderocol is a novel siderophore cephalosporin that utilizes bacterial ferric iron transports to cross the outer membrane. Cefiderocol shows high stability against all classes of β-lactamases, rendering it extremely potent against carbapenem- and multidrug-resistant Gram-negative organisms. Using a neutropenic murine thigh model, we compared the efficacies of human-simulated exposures of cefiderocol (2 g Q8H 3 h infusion) and ceftazidime (2 g Q8H 2 h infusion) against Stenotrophomonas maltophilia, an emerging opportunistic Gram-negative organism associated with serious and often fatal nosocomial infections. Twenty-four S. maltophilia isolates were studied, including isolates resistant to ceftazidime, trimethoprim-sulfate, and/or levofloxacin. The thighs were inoculated with bacterial suspensions of 10⁸ CFU/mL and the human-simulated regimens were administered over 24 h. Efficacy was measured as the change in log₁₀CFU/thigh at 24 h compared with 0 h controls. Cefiderocol human-simulated exposure demonstrated potent bacterial killing; mean bacterial reduction at 24 h was -2.67 ± 0.68 log₁₀CFU/thigh with ≥ 2 log-reduction achieved in 21 isolates (87.5%) and ≥ 1 log-reduction achieved in the remaining three isolates (12.5%). In comparison, ceftazidime human-simulated exposure produced mean bacterial reduction of -1.38 ± 1.49 log₁₀CFU/thigh among 10 ceftazidime-susceptible isolates and mean bacterial growth of 0.64 ± 0.79 log₁₀CFU/thigh among 14 ceftazidime-non-susceptible isolates. While ceftazidime showed modest efficacy against most susceptible isolates, humanized cefiderocol exposures resulted in remarkable in vivo activity against all S. maltophilia isolates examined, inclusive of ceftazidime-non-susceptible isolates. The potent in vitro and in vivo activity of cefiderocol supports the development of this novel compound for managing S. maltophilia infections.

Higher MICs (>2 mg/L) Predict 30-Day Mortality in Patients With Lower Respiratory Tract Infections Caused by Multidrug- and Extensively Drug-Resistant Pseudomonas aeruginosa Treated With Ceftolozane/Tazobactam

Background

Ceftolozane/tazobactam (C/T) efficacy and safety in ventilator-associated pneumonia (VAP) is being evaluated at a double dose by several trials. This dosing is based on a pharmacokinetic (PK) model that demonstrated that 3 g q8h achieved ≥90% probability of target attainment (50% ƒT > minimal inhibitory concentration [MIC]) in plasma and epithelial lining fluid against C/T-susceptible P. aeruginosa. The aim of this study was to evaluate the efficacy of different C/T doses in patients with lower respiratory infection (LRI) due to MDR- or XDR-P. aeruginosa considering the C/T MIC.

Methods

This was a multicenter retrospective study of 90 patients with LRI caused by resistant P. aeruginosa who received a standard or high dose (HDo) of C/T. Univariable and multivariable analyses were performed to identify independent predictors of 30-day mortality.

Results

The median age (interquartile range) was 65 (51-74) years. Sixty-three (70%) patients had pneumonia, and 27 (30%) had tracheobronchitis. Thirty-three (36.7%) were ventilator-associated respiratory infections. The median C/T MIC (range) was 2 (0.5-4) mg/L. Fifty-four (60%) patients received HDo. Thirty-day mortality was 27.8% (25/90). Mortality was significantly lower in patients with P. aeruginosa strains with MIC ≤2 mg/L and receiving HDo compared with the groups with the same or higher MIC and dosage (16.2% vs 35.8%; P = .041). Multivariate analysis identified septic shock (P < .001), C/T MIC >2 mg/L (P = .045), and increasing Charlson Comorbidity Index (P = .019) as independent predictors of mortality.

Conclusions

The effectiveness of C/T in P. aeruginosa LRI was associated with an MIC ≤2 mg/L, and the lowest mortality was observed when HDo was administered for strains with C/T MIC ≤2 mg/L. HDo was not statistically associated with a better outcome.

Microbial cause of ICU-acquired pneumonia: hospital-acquired pneumonia versus ventilator-associated pneumonia

PURPOSE OF REVIEW

Successful treatment of patients with hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) remains a difficult and complex undertaking. Better knowledge of the pathogens involved in that setting may allow reassessment of our current modalities of therapy and definition of better protocols.

RECENT FINDINGS

Microorganisms responsible for HAP/VAP differ according to geographic areas, ICU patients' specific characteristics, durations of hospital and ICU stays before onset of the disease, and risk factors for MDR pathogens. However, a number of studies have shown that Gram-negative bacilli (GNB) - particularly Pseudomonas aeruginosa and Enterobacteriaceae - cause many of the respiratory infections in this setting, with minimal differences between HAP and VAP, indicating that the cause depends more on the underlying clinical condition of patients rather than previous intubation.

SUMMARY

When selecting initial antimicrobial therapy in patients with HAP/VAP, more attention should be paid to individual risk factors for MDR pathogens, severity of the clinical situation, and the local epidemiology than to the type of pneumonia.

Antibacterial mechanism of peptide Cec4 against Acinetobacter baumannii

Background

A case of Acinetobacter baumannii (A. baumannii), known as gram-negative bacteria, causes a range of nosocomial infections. Due to the continuous detection of multi-drug resistant A. baumannii in the clinic, there is an urgent need to find alternative therapies, including broad-spectrum antibacterial peptides (AMP). Recently it has been found that the peptide Cec4 has good antibacterial activity against A. baumannii, but the antibacterial mechanism remains elusive.

Materials and methods

The basic structure of Cec4 was analyzed by circular dichroism (CD) spectroscopy, and the potential antibacterial mechanism of Cec4 was detected by flow cytometry, transmission electron microscopy, fluorescence and confocal microscopy. The minimum inhibitory concentration (MIC) of antimicrobial peptides against various A. baumannii was determinated with broth microdilution techniques. The biofilm formation and the sensitivity detection of biofilms to antimicrobial peptides were detected by crystal violet staining.

Results

In this study, the main secondary structure of the antibacterial peptide Cec4 is α-helix (99.7%) in the hydrophobic environment. Furthermore, after the treatment with Cec4, an amount of leakage of A. baumannii and the destruction of its cell membrane were detected. Moreover, it was observed that FITC-Cec4 can enter the cell, and more cells were held in the G1 phase with peptide Cec4. However, the DNA binding assay of the peptide Cec4 indicates that the peptide does not target DNA. In addition, peptide Cec4 was superior in reducing adherent biofilms of A. baumannii compared to conventional antibiotics and has no cytotoxicity.

Conclusion

It is apparent that the antibacterial peptide Cec4 may achieve rapid sterilization by multi-target interaction and presents an attractive therapeutic option for the prevention and control of A. baumannii infections.

Incidence and Risk Factors Associated with Multi-Drug-Resistant Pathogens in a Critically Ill Trauma Population: A Retrospective Cohort Study

Background: Multi-drug resistance is considered a serious health threat particularly in the intensive care unit (ICU) setting. Studies evaluating multi-drug-resistant (MDR) pathogens in critically ill trauma patients are limited. The objectives were to describe the incidence of MDR, extensive-drug-resistant (XDR), and pan-drug-resistant (PDR) organism growth in ICU patients admitted with traumatic injuries and to identify any risk factors associated with MDR growth. Patients and Methods: This was a retrospective single-center cohort study of all ICU adult patients identified via the institution's trauma registry from January 1, 2016 to August 31, 2017. Patients were included if they had positive culture growth with susceptibility data taken during the index hospitalization. Patients were excluded if their cultures were drawn within 48 hours of emergency department triage. Study groups were defined based on the presence of at least one MDR pathogen during the index hospitalization. Results: A total of 2,578 charts were reviewed and 95 patients (mean age, 60 years; 66 males [69%]) with 201 total cultures were included. The majority of positive cultures were from respiratory (69%) and urinary (16%) sources. Of the 201 positive cultures, the majority of species identified was Enterobacteriaceae (47%), Staphylococcus (32%), Enterococcus (7%), Acinetobacter (5%), and Pseudomonas (3%). Of the 95 patients with positive cultures, the incidence of MDR, XDR, and PDR organisms was found to be 31%, 17%, and 0%, respectively. Augmented renal clearance (ARC) was the only risk factor associated with an increased risk for MDR organism growth (adjusted odds ratio 9.78, 95% confidence interval [CI] 2.56-37.41; p = 0.001). Conclusions: In this cohort of critically ill trauma patients, the incidence of an MDR pathogen occurred in 31% of patients. This is the first study to find an association of ARC and multi-drug resistance, which should be further validated as a potential cause for MDR organisms.

Comparative Epidemiology and Resistance Trends of Proteae in Urinary Tract Infections of Inpatients and Outpatients: A 10-Year Retrospective Study

Compared with infections caused by other bacterial pathogens, urinary tract infections (UTIs) caused by Proteae are often more severe and associated with a higher rate of recurrence, sequelae, and pyelonephritis. The aim of this retrospective study was to assess and compare the prevalence of UTIs caused by different species of the Proteae tribe (namely Proteus, Morganella and Providencia species) and the antibiotic resistance levels isolated from inpatients and outpatients in a primary- and tertiary-care teaching hospital in the Southern Great Plain of Hungary, during a 10-year study period. To evaluate the resistance trends of isolated strains, amoxicillin/clavulanic acid, ceftriaxone, meropenem, ertapenem, gentamicin, ciprofloxacin, and fosfomycin were chosen as indicator antibiotics, based on local antibiotic utilization data. Members of Proteae were more frequently isolated in the case of inpatients (7.20 ± 1.74% vs. 5.00 ± 0.88%; p = 0.0031), P. mirabilis was the most frequently isolated member of the group. The ratio of resistant strains to sulfamethoxazole/trimethoprim, ciprofloxacin, ceftriaxone, and fosfomycin was significantly higher in the inpatient group. In the case of amoxicillin/clavulanic acid, ceftriaxone, ciprofloxacin, and sulfamethoxazole/trimethoprim, the ratio of resistant isolates was markedly higher between 2013–2017 (p < 0.01). Resistance developments of Proteae, coupled with their intrinsic non-susceptibility to several antibiotics (tetracyclines, colistin, nitrofurantoin) severely limits the number of therapeutic alternatives, especially for outpatients.

Comparative Epidemiology and Resistance Trends of Common Urinary Pathogens in a Tertiary-Care Hospital: A 10-Year Surveillance Study

Background and Objective: Urinary tract infections (UTIs) are common in human medicine, affecting large patient populations worldwide. The principal cause of UTIs is uropathogenic Escherichia coli (UPEC) and Klebsiella, both in community and nosocomial settings. The assessment of local data on prevalence and resistance is essential to evaluate trends over time and to reflect on the national situation, compared to international data, using the methods of analytical epidemiology. Materials and Methods: The aim of this study was to assess resistance trends and epidemiology of UTIs caused by E. coli and Klebsiella species in inpatients and outpatients at a tertiary-care hospital in Hungary, using microbiological data. To evaluate resistance trends, several antibiotics were chosen as indicator drugs, based on local utilization data. Results: E. coli was the most prevalent isolate, representing 56.75 ± 4.86% for outpatients and 42.29 ± 2.94% for inpatients. For E. coli, the ratio of resistant strains for several antibiotics was significantly higher in the inpatient group, while in Klebsiella, similar trends were only observed for gentamicin. Extended-spectrum β-lactamase (ESBL)-producing isolates were detected in 4.33-9.15% and 23.22-34.22% from outpatient, 8.85-38.97% and 10.89-36.06% from inpatient samples for E. coli and Klebsiella, respectively. Conclusions: Resistance developments in common UTI pathogens (especially to fosfomycin, sulfamethoxazole-trimethoprim, fluoroquinolones, and 3rd generation cephalosporins), seriously curb therapeutic options, especially in outpatient settings.

In vitro studies evaluating the activity of imipenem in combination with relebactam against Pseudomonas aeruginosa

BACKGROUND

The prevalence of antibiotic resistance is increasing, and multidrug-resistant Pseudomonas aeruginosa has been identified as a serious threat to human health. The production of β-lactamase is a key mechanism contributing to imipenem resistance in P. aeruginosa. Relebactam is a novel β-lactamase inhibitor, active against class A and C β-lactamases, that has been shown to restore imipenem susceptibility. In a series of studies, we assessed the interaction of relebactam with key mechanisms involved in carbapenem resistance in P. aeruginosa and to what extent relebactam might overcome imipenem non-susceptibility.

RESULTS

Relebactam demonstrated no intrinsic antibacterial activity against P. aeruginosa, had no inoculum effect, and was not subject to efflux. Enzymology studies showed relebactam is a potent (overall inhibition constant: 27 nM), practically irreversible inhibitor of P. aeruginosa AmpC. Among P. aeruginosa clinical isolates from the SMART global surveillance program (2009, n = 993; 2011, n = 1702; 2015, n = 5953; 2016, n = 6165), imipenem susceptibility rates were 68.4% in 2009, 67.4% in 2011, 70.4% in 2015, and 67.3% in 2016. With the addition of 4 μg/mL relebactam, imipenem susceptibility rates increased to 87.6, 86.0, 91.7, and 89.8%, respectively. When all imipenem-non-susceptible isolates were pooled, the addition of 4 μg/mL relebactam reduced the mode imipenem minimum inhibitory concentration (MIC) 8-fold (from 16 μg/mL to 2 μg/mL) among all imipenem-non-susceptible isolates. Of 3747 imipenem-non-susceptible isolates that underwent molecular profiling, 1200 (32%) remained non-susceptible to the combination imipenem/relebactam (IMI/REL); 42% of these encoded class B metallo-β-lactamases, 11% encoded a class A GES enzyme, and no class D enzymes were detected. No relationship was observed between alleles of the chromosomally-encoded P. aeruginosa AmpC and IMI/REL MIC.

CONCLUSIONS

IMI/REL exhibited potential in the treatment of carbapenem-resistant P. aeruginosa infections, with the exception of isolates encoding class B, some GES alleles, and class D carbapenemases.

Management of ventilator-associated pneumonia (VAP) caused by resistant gram-negative bacteria: which is the best strategy to treat?

Introduction: Treatment of ventilator-associated pneumonia (VAP) is a major challenge. The increase in multi-drug resistant bacteria has not been accompanied by the validation of new drugs, or by any new antimicrobial strategies to exploit the available agents. VAP due to Gram-negative bacteria has increased mortality, both due to the resistant pathogens themselves and due to inappropriate treatment. Local epidemiology, patients' characteristics and clinical responses provide the most important information for therapeutic decision-making. Moreover, data on VAP therapy due to resistant bacteria are lacking, and the choice of treatment is often based on clinical practice and individual experience. Areas covered: This review summarizes the strategies available for treating the three most prevalent resistant Gram-negative organisms causing VAP: Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae. The review covers the results of a Pubmed search, clinical practice guidelines and reviews, and the authors' experience. Expert opinion: The existing evidence focuses on bloodstream infections or other sites rather than pneumonia and there are no recommendations for the treatment of VAP by multi-drug resistant Gram-negative bacteria, especially for combination regimens. The approval of new drugs is needed to provide effective and safe alternatives for treating carbapenemase-producing strains. Precision medicine and personalized approach are also fundamental in future research.

Resistance Trends and Epidemiology of Citrobacter-Enterobacter-Serratia in Urinary Tract Infections of Inpatients and Outpatients (RECESUTI): A 10-Year Survey

Background and objectives: Urinary tract infections (UTIs) are the third most common infections in humans, representing a significant factor of morbidity, both among outpatients and inpatients. The pathogenic role of Citrobacter, Enterobacter, and Serratia species (CES bacteria) has been described in UTIs. CES bacteria present a therapeutic challenge due to the various intrinsic and acquired resistance mechanisms they possess. Materials and Methods: The aim of this study was to assess and compare the resistance trends and epidemiology of CES pathogens in UTIs (RECESUTI) in inpatients and outpatients during a 10-year study period. To evaluate the resistance trends of isolated strains, several antibiotics were chosen as indicator drugs based on local utilization data. 578 CES isolates were obtained from inpatients and 554 from outpatients, representing 2.57 ± 0.41% of all positive urine samples for outpatients and 3.02 ± 0.40% for inpatients. E. cloacae was the most prevalent species. Results: The ratio of resistant strains to most of the indicator drugs was higher in the inpatient group and lower in the second half of the study period. ESBL-producing isolates were detected in 0-9.75% from outpatient and 0-29.09% from inpatient samples. Conclusions: Resistance developments of CES bacteria, coupled with their intrinsic non-susceptibility to several antibiotics, severely limits the number of therapeutic alternatives, especially for outpatients.

Resistenze antibiotiche e nuove molecole: qual è lo scenario attuale?

Antibiotic resistance and new drugs in urologic setting: what we need to know? Urinary tract infections (UTIs) are among the most frequent infectious diseases, and represent an important public health problem with a substantial economic burden. In recent years the chemoresistance of the main uropathogens has significantly increased worldwide. Extended spectrum beta-lactamase (ESBL) production and multi-drug resistant (MDR) clones of Escherichia coli and Klebsiella pneumoniae are limiting available treatment options. Carbapenems and aminoglycosides are still effective in complicated UTI. New beta-lactam combinations such as ceftolozane-tazobactam and ceftazidime-avibactam may be highly useful in treating severe infections while contributing to the carbapenem sparing strategy. For uncomplicated UTI, within older antibiotics, fosfomycin trometamol may be considered a first-choice drug since it is still retaining a good activity against MDR uropathogens. On the other hand, there are extensive data showing that the administration of antimicrobials according to pharmacokinetic/pharmacodynamic (PK/PD) parameters improves the possibility of a positive clinical outcome, particularly in severely ill patients. Evidence is growing that when PK/PD parameters are used to target not only clinical cure. This article discusses the PK/PD characteristics of antimicrobial agents for the treatment of UTIs, and the pharmacological and therapeutic strategies for limiting or preventing bacterial resistance.

Antibiotic resistance profiles and multidrug resistance patterns of Streptococcus pneumoniae in pediatrics: A multicenter retrospective study in mainland China

Emergent resistance to antibiotics among Streptococcus pneumoniae isolates is a severe problem worldwide. Antibiotic resistance profiles for S pneumoniae isolates identified from pediatric patients in mainland China remains to be established.The clinical features, antimicrobial resistance, and multidrug resistance patterns of S pneumoniae were retrospectively analyzed at 10 children's hospitals in mainland China in 2016.Among the collected 6132 S pneumoniae isolates, pneumococcal diseases mainly occurred in children younger than 5 years old (85.1%). The resistance rate of S pneumoniae to clindamycin, erythromycin, tetracycline, and trimethoprim/sulfamethoxazole was 95.8%, 95.2%, 93.6%, and 66.7%, respectively. The resistance rates of S pneumoniae to penicillin were 86.9% and 1.4% in non-meningitis and meningitis isolates, while the proportions of ceftriaxone resistance were 8.2% and 18.1%, respectively. Pneumococcal conjugate vaccine was administered to only 4.1% of patients. Penicillin and ceftriaxone resistance, underling diseases, antibiotic resistant risk factors, and poor prognosis appeared more frequently in invasive pneumococcal diseases. The incidence of multidrug resistance (MDR) was 46.1% in patients with invasive pneumococcal disease which was more than in patients with non-invasive pneumococcal disease (18.3%). Patients with invasive pneumococcal disease usually have several MDR coexistence.S pneumoniae isolates showed high resistance to common antibiotics in mainland China. Penicillin and ceftriaxone resistance rate of invasive streptococcal pneumonia patients were significantly higher than that of non-invasive S pneumoniae patients. Alarmingly, 46.1% of invasive clinical isolates were multidrug resistant, so it is important to continued monitor the resistance of S pneumoniae when protein conjugate vaccine (PCV13) is coming in mainland China.

Epidemiological Trends and Resistance Associated with Stenotrophomonas maltophilia Bacteremia: A 10-Year Retrospective Cohort Study in a Tertiary-Care Hospital in Hungary

Stenotrophomonas maltophilia has been recognized as an emerging nosocomial pathogen in invasive infections of immunocompromised, severely debilitated patients with significant underlying illnesses. The first-choice drug in these infections is sulfamethoxazole-trimethoprim (SMX/TMP), and resistance to this antimicrobial is a daunting challenge for clinicians. The aim of this study was to assess the prevalence of S. maltophilia bacteremia and SMX/TMP-resistance levels at a tertiary-care university hospital. A total of 175 episodes of S. maltophilia bacteremia were identified (2008-2012: n = 82, 2013-2017: n = 93; p = 0.061), 52% of affected patients were 60 years of age, and had recent surgery, severe injuries or underlying conditions (malignant hematologic diseases and solid tumors) in their history. Sixteen percent of isolates were resistant to SMX/TMP (2008-2012: n = 13.8%, 2013-2017: n = 17.2%; p = 0.076), and out of the resistant strains, 32.7% were also resistant to levofloxacin and colistin. Our findings on the SMX/TMP-resistance were similar to global literature data.

Integrating Culture-based Antibiotic Resistance Profiles with Whole-genome Sequencing Data for 11,087 Clinical Isolates

Emerging antibiotic resistance is a major global health threat. The analysis of nucleic acid sequences linked to susceptibility phenotypes facilitates the study of genetic antibiotic resistance determinants to inform molecular diagnostics and drug development. We collected genetic data (11,087 newly-sequenced whole genomes) and culture-based resistance profiles (10,991 out of the 11,087 isolates comprehensively tested against 22 antibiotics in total) of clinical isolates including 18 main species spanning a time period of 30 years. Species and drug specific resistance patterns were observed including increased resistance rates for Acinetobacter baumannii to carbapenems and for Escherichia coli to fluoroquinolones. Species-level pan-genomes were constructed to reflect the genetic repertoire of the respective species, including conserved essential genes and known resistance factors. Integrating phenotypes and genotypes through species-level pan-genomes allowed to infer gene–drug resistance associations using statistical testing. The isolate collection and the analysis results have been integrated into GEAR-base, a resource available for academic research use free of charge at https://gear-base.com.

Randomized Trial of Ceftazidime-Avibactam vs Meropenem for Treatment of Hospital-Acquired and Ventilator-Associated Bacterial Pneumonia (REPROVE): Analyses per US FDA-Specified End Points

Background

Hospital-acquired and ventilator-associated pneumonia (HAP/VAP; nosocomial pneumonia) due to Gram-negative pathogens are associated with significant morbidity and mortality; treatment options for multidrug-resistant infections are limited. The pivotal phase III REPROVE trial evaluated the efficacy of ceftazidime-avibactam (CAZ-AVI) vs meropenem in the treatment of patients with HAP/VAP. Study results for prespecified analyses per US Food and Drug Administration–recommended trial end points are reported here.

Methods

Hospitalized adults with HAP/VAP proven or suspected to be caused by a Gram-negative pathogen were randomized 1:1 to receive CAZ-AVI or meropenem for 7 to 14 days. The primary outcome was 28-day all-cause mortality in the intent-to-treat (ITT) population. Secondary outcomes included clinical cure at test of cure (TOC) in the ITT and microbiological ITT (micro-ITT) populations, and safety and tolerability throughout the study.

Results

hundred seventy randomized patients received treatment and were included in the ITT population (CAZ-AVI, n = 436; meropenem, n = 434). CAZ-AVI was noninferior to meropenem for the primary end point (28-day all-cause mortality; ITT) based on the prespecified 10% noninferiority margin (CAZ-AVI, 9.6%; meropenem, 8.3%; difference, 1.5%; 95% confidence interval [CI], –2.4% to 5.3%) and for the clinical cure end point in the ITT population based on a prespecified –10% noninferiority margin (CAZ-AVI, 67.2%; meropenem, 69.1%; difference, −1.9%; 95% CI, –8.1% to 4.3%). Clinical cure rates at TOC for patients infected with CAZ-nonsusceptible pathogens were similar (CAZ-AVI, 75.5%; meropenem, 71.2%; micro-ITT). Safety data were consistent with established safety profiles for both agents.

Conclusions

CAZ-AVI provides an important new treatment option for HAP/VAP due to Gram-negative pathogens, including CAZ-nonsusceptible strains.

High prevalence of CTX-M-1 group in ESBL-producing enterobacteriaceae infection in intensive care units in southern Chile

Enterobacteria-producing extended-spectrum β-lactamases (ESBL) play an important role in healthcare infections, increasing hospitalization time, morbidity and mortality rates. Among several ESBLs that emerge from these pathogens, CTX-M-type enzymes had the most successful global spread in different epidemiological settings. Latin America presents high prevalence of CTX-M-2 in ESBL-producing enterobacterial infections with local emergence of the CTX-M-1 group. However, this high prevalence of the CTX-M-1 group has not yet been reported in Chile. The aim of this study was to identify ESBLs among enterobacteria isolated from clinical samples of critically ill patients from southern Chile. One-hundred thirty seven ESBL-producing bacteria were isolated from outpatients from all critical patient units from Hernán Henríquez Aravena Hospital. Phenotype characterization was performed by antibiogram, screening of ESBL, and determination of minimum inhibitory concentration (MIC). PCR was used for genetic confirmation of resistance. Molecular typing was performed by ERIC-PCR. ESBL-producing isolates were identified as Klebsiella pneumoniae (n = 115), Escherichia coli (n = 18), Proteus mirabilis (n = 3), and Enterobacter cloacae (n = 1), presenting multidrug resistance profiles. PCR amplification showed that the strains were positive for blaSHV (n = 111/81%), blaCTX-M-1 (n = 116/84.7%), blaTEM (n = 100/73%), blaCTX-M-2 (n = 28/20.4%), blaCTX-M-9 (0.7%), blaPER-1 (0.7%), and blaGES-10 (0.7%). The multiple production of ESBL was observed in 93% of isolates, suggesting high genetic mobility independent of the clonal relationship. The high frequency of the CTX-M-1 group and a high rate of ESBL co-production are changing the epidemiology of the ESBL profile in Chilean intensive care units. This epidemiology is a constant and increasing challenge, not only in Chile, but worldwide.

Safety and efficacy of a bacteriophage cocktail in an in vivo model of Pseudomonas aeruginosa sinusitis

Pseudomonas aeruginosa (PA) is a bacterial pathogen that frequently displays antibiotic resistance. Its presence within the sinuses of chronic rhinosinusitis sufferers is associated with poorer quality of life. Obligately lytic bacteriophages (phages) are viruses that infect, replicate within, and lyse bacteria, causing bacterial death. The aims of this study were to assess the safety and efficacy of a PA phage cocktail (CT-PA) in a sheep model of rhinosinusitis. The sheep rhinosinusitis model was adapted to simulate PA infection in sheep frontal sinuses. To assess efficacy, after a 7-day biofilm formation period, sheep received twice-daily frontal trephine flushes of CT-PA or saline for 1 week. Biofilm quantitation on frontal sinus mucosa was performed using LIVE/DEAD BacLight staining. To assess safety, sheep received twice-daily frontal trephine flushes of CT-PA or vehicle control for 3 weeks. Blood and fecal samples were collected throughout treatment. Histopathology of frontal sinus, lung, heart, liver, spleen, and kidney tissue was performed. Sinus cilia were visualized using scanning electron microscopy (SEM). The Efficacy arm showed a statistically significant reduction in biofilm biomass with all concentrations of CT-PA tested (P < 0.05). Phage presence in sinuses was maintained for at least 16hours after the final flush. All Safety arm sheep completed 3 weeks of treatment. Phage was detected consistently in feces and sporadically in blood and organ samples. Histology and SEM of tissues revealed no treatment-related damage. In conclusion, CT-PA was able to decrease sinus PA biofilm at concentrations of 10⁸-10¹⁰ PFU/mL. No safety concerns were noted.

Utilization of Vector Autoregressive and Linear Transfer Models to Follow Up the Antibiotic Resistance Spiral in Gram-negative Bacteria From Cephalosporin Consumption to Colistin Resistance

Background

Increasing antibiotic resistance may reciprocally affect consumption and lead to use of broader-spectrum alternatives; a vicious cycle that may gradually limit therapeutic options. Our aim in this study was to demonstrate this vicious cycle in gram-negative bacteria and show the utility of vector autoregressive (VAR) models for time-series analysis in explanatory and dependent roles simultaneously.

Methods

Monthly drug consumption data in defined daily doses per 100 bed-days and incidence densities of gram-negative bacteria (Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, and Acinetobacter baumannii) resistant to cephalosporins or to carbapenems were analyzed using VAR models. These were compared to linear transfer models used earlier.

Results

In case of all gram-negative bacteria, cephalosporin consumption led to increasing cephalosporin resistance, which provoked carbapenem use and consequent carbapenem resistance and finally increased colistin consumption, exemplifying the vicious cycle. Different species were involved in different ways. For example, cephalosporin-resistant Klebsiella spp. provoked carbapenem use less than E. coli, and the association between carbapenem resistance of P. aeruginosa and colistin use was weaker than that of A. baumannii. Colistin use led to decreased carbapenem use and decreased carbapenem resistance of P. aeruginosa but not of A. baumannii.

Conclusions

VAR models allow analysis of consumption and resistance series in a bidirectional manner. The reconstructed resistance spiral involved cephalosporin use augmenting cephalosporin resistance primarily in E. coli. This led to increased carbapenem use, provoking spread of carbapenem-resistant A. baumannii and consequent colistin use. Emergence of panresistance is fueled by such antibiotic-resistance spirals.

Comparison of five commonly used automated susceptibility testing methods for accuracy in the China Antimicrobial Resistance Surveillance System (CARSS) hospitals

Objective

The objective of this study was to evaluate the performance of five commonly used automated antimicrobial susceptibility testing (AST) systems in China (Vitek 2, Phoenix, Microscan, TDR, and DL).

Materials and methods

Two “unknown” isolates, S1 (ESBL-producing Escherichia coli) and S2 (KPC-producing Klebsiella pneumoniae), were sent to 886 hospitals in China for identification and AST. Using broth microdilution method (BMD) as gold standard, minimum inhibitory concentrations (MICs) were determined.

Results

Most hospitals (392, 46.1%) used Vitek 2, followed by 16% each for Phoenix, Microscan, and DL systems, and 5.9% (50) used TDR system. MICs of 22 antimicrobials were evaluated for two study isolates plus three ATCC strains. Individual susceptibility results for three ATCC strains (n=1581) were submitted by 780 (91.2%) hospitals. For each AST system, 8.7% (6/69) to 13.0% (33/253) reported MICs outside the expected range for several drugs. For the two study isolates, TDR and DL systems performed the worst in MIC determination and susceptibility categorization of cefazolin and cefepime, while the Microscan system had difficulties in susceptibility categorization for aztreonam and ertapenem. Categorical agreements were >90% for most antimicrobials tested for both the isolates, among which, using BMD, no essential agreements were noted for ampicillin, piperacillin, cefazolin, cefuroxime, ceftriaxone, and trimethoprim/sulfamethoxazole. All AST systems except Vitek 2 showed unacceptable VMEs for cefazolin (S1 and S2) and major errors for ceftazidime, cefepime, and aztreonam (isolate S1), while Vitek 2 showed a high VME rate for cefepime (10.0%) and meropenem (6.2%) for S2.

Conclusion

None of the five automated systems met the criteria for acceptable AST performance, but Vitek 2 provided a relatively accurate and conservative performance for most of the antimicrobials.

Assessing antimicrobial stewardship initiatives: Clinical evaluation of cefepime or piperacillin/tazobactam in patients with bloodstream infections secondary to AmpC-producing organisms

Management of micro-organisms harbouring AmpC β-lactamases remains challenging. Carbapenems are often considered first-line agents. Due to growing concern regarding carbapenem-resistant Enterobacteriaceae, integrating non-carbapenem treatment strategies is being explored for these pathogens. The primary objective of this study was to evaluate clinical outcomes in patients with bacteraemia secondary to AmpC-producing organisms treated with cefepime or piperacillin/tazobactam (TZP). A retrospective study of adult patients receiving cefepime or TZP for the treatment of AmpC -producing organisms with positive cefoxitin screen (i.e. Citrobacter, Enterobacter or Serratia spp. along with cefoxitin resistance) isolated from blood cultures was conducted. The primary endpoint was clinical cure at end of therapy (EOT). Secondary endpoints included microbiological eradication, frequency of susceptibility changes following treatment, and 7- and 30-day all-cause mortality. Clinical cure at EOT was 87.1%, with 93.2% of patients achieving microbiological eradication. The 7- and 30-day mortality rates were 3.8% and 10.6%, respectively. Organism susceptibility was exceptionally high, with minimum inhibitory concentrations (MICs) of ≤2 μg/mL in 90% of patients treated with cefepime (n = 108). Selection for resistance to third-generation cephalosporins or primary antimicrobial therapy was infrequent at 6.1% (8/132). In conclusion, use of cefepime or TZP for management of AmpC bloodstream infections was associated with clinical and microbiological cure with infrequent selection for resistance.

Understanding the biomimetic properties of gallium in Pseudomonas aeruginosa: an XAS and XPS study

Pyochelin (PCH) is a siderophore (extracellular chelator) produced by the pathogenic bacterium Pseudomonas aeruginosa (PAO). PCH is implicated in iron (Fe³⁺) transport to PAO, and is crucial for its metabolism and pathogenicity. Due to the chemical similarity with Fe³⁺, gallium (Ga³⁺) interferes with vital iron-dependent processes in bacterial cells, thereby opening new perspectives for the design of specific metal-based antibacterial drugs. However, the structural basis for the Fe³⁺-mimetic properties of Ga³⁺ complexed with the PCH siderophore is still lacking. A precise knowledge of the coordination chemistry at the metal site is one of the topmost issues in the production of novel biomimetic metal-based drugs. Elucidation of this issue by means of a deep structural spectroscopic investigation could lead to an improved interference with, or a specific inhibition of, relevant biological pathways. For this reason, we applied Synchrotron Radiation induced X-ray Photoelectron Spectroscopy (SR-XPS) and X-ray Absorption Spectroscopy (XAS) to probe the electronic nature and coordination chemistry of Fe³⁺ and Ga³⁺ coordinative sites in PCH metal complexes. Combined XAFS and SR-XPS studies allow us to demonstrate that both Fe and Ga have the same valence state in Fe-PCH and Ga-PCH, and have the same octahedral coordination geometry. Moreover, a similar next neighbour distribution for Fe and Ga, resulting from the EXAFS data analysis, strongly supports similar coordination chemistry at the origin of the biomimetic behaviour of Ga.

Antimicrobial Activity of Murepavadin Tested against Clinical Isolates of Pseudomonas aeruginosa from the United States, Europe, and China

Murepavadin (formerly POL7080), a 14-amino-acid cyclic peptide, and comparators were tested by the broth microdilution method against 1,219 Pseudomonas aeruginosa isolates from 112 medical centers. Murepavadin (MIC_50/90, 0.12/0.12 mg/liter) was 4- to 8-fold more active than colistin (MIC_50/90, 1/1 mg/liter) and polymyxin B (MIC_50/90, 0.5/1 mg/liter) and inhibited 99.1% of isolates at ≤0.5 mg/liter. Only 4 isolates (0.3%) exhibited murepavadin MICs of >2 mg/liter. Murepavadin was equally active against isolates from Europe, the United States, and China.

Ceftazidime-Avibactam Antimicrobial Activity and Spectrum When Tested Against Gram-negative Organisms From Pediatric Patients: Results From the INFORM Surveillance Program (United States, 2011-2015)

BACKGROUND

Ceftazidime-avibactam was approved by the US Food and Drug Administration in 2015 to treat complicated intra-abdominal and urinary tract infections in adults and is under clinical development for treating pediatric patients.

METHODS

Among 53,381 Gram-negative organisms (1 per patient) collected in 2011-2015, 8461 (15.9%) were from pediatric (≤17 years old) patients. The isolates were collected from 82 US medical centers and susceptibility tested against ceftazidime-avibactam (avibactam at fixed 4 μg/mL) and comparators by reference broth microdilution methods. Susceptibility results were stratified by patient age: ≤1 (3671 isolates); 2-5 (1900); 6-12 (1644) and 13-17 years old (1246). Enterobacteriaceae with an extended-spectrum β-lactamase (ESBL) screening-positive phenotype were evaluated by microarray-based assay for genes encoding ESBLs, KPC, NDM and transferable AmpC enzymes.

RESULTS

Ceftazidime-avibactam inhibited >99.9% of all Enterobacteriaceae at the ≤8 μg/mL susceptible break point and was highly active against ESBL screening-positive phenotype Escherichia coli and Klebsiella pneumoniae. Overall, 83.6% of ESBL screening-positive phenotype K. pneumoniae were susceptible to meropenem. Only 1 of 4724 Enterobacteriaceae (0.02%) isolates was nonsusceptible to ceftazidime-avibactam, an Enterobacter aerogenes with a ceftazidime-avibactam minimum inhibitory concentration (MIC) value of 16 μg/mL and negative results for all β-lactamase tested. Ceftazidime-avibactam was very active against Pseudomonas aeruginosa (MIC50/90, 1/4 μg/mL; 99.1% susceptible), including isolates nonsusceptible to meropenem (94.0% susceptible to ceftazidime-avibactam) or piperacillin-tazobactam (91.7% susceptible) or ceftazidime (89.6% susceptible). Ceftazidime-avibactam activity against P. aeruginosa did not vary substantially among age groups (98.8%-99.3% susceptible) or year of isolation (98.5%-100.0% susceptible).

CONCLUSIONS

Ceftazidime-avibactam was very active against a large collection of Gram-negative bacilli isolated from pediatric patients, including P. aeruginosa and Enterobacteriaceae with an ESBL screening-positive phenotype and resistant to carbapenems.

Effect of Porins and blaKPC Expression on Activity of Imipenem with Relebactam in Klebsiella pneumoniae: Can Antibiotic Combinations Overcome Resistance?

Imipenem with relebactam is a novel β-lactam-β-lactamase inhibitor that has activity against most KPC-producing Enterobacteriaceae. Using 10 isolates of KPC-possessing Klebsiella pneumoniae, we assessed the relationship between imipenem-relebactam minimum inhibitory concentrations (MICs) and mechanisms known to contribute to antimicrobial resistance. The effect of adding a second agent was assessed by time-kill experiments. Mutations affecting the genes encoding porins ompK35 and ompK36 and identification of β-lactamases were assessed by PCR. Expression of bla_KPC and acrB was assessed by real-time reverse-transcriptase (RT)-PCR, and production of OmpK36 by SDS-PAGE. Time-kill studies were performed using combinations of imipenem-relebactam with polymyxin B, amikacin, or tigecycline. Seven isolates having a disruption in a single porin, or in neither porin, remained susceptible to imipenem-relebactam. The addition of a second agent did not improve the activity of imipenem-relebactam for these isolates, although the addition of tigecycline was antagonistic for three isolates. Three isolates had major disruptions in both ompK35 and ompK36 that correlated with reduced activity of imipenem-relebactam (MICs 2/4, 8/4, and 512/4 μg/mL). Two of these isolates also had overexpression of bla_KPC, including the isolate with the highest MIC. These isolates were also resistant to polymyxin B and amikacin. The addition of amikacin provided both synergistic and bactericidal activity for the two more resistant isolates. The activity of imipenem-relebactam against K. pneumoniae is affected by major disruptions of both ompK35 and ompK36 and by expression of the KPC gene. Combining imipenem-relebactam with an aminoglycoside may be a promising approach for isolates with reduced susceptibility to imipenem-relebactam.

Clinical Features, Antibiotic Susceptibility Profile, and Outcomes of Infectious Keratitis Caused by Stenotrophomonas maltophilia

PURPOSE

Stenotrophomonas maltophilia, an uncommon cause of infectious keratitis, is difficult to treat because of its resistance to multiple antibiotics. The purpose of this study is to describe the clinical features, antibiotic susceptibility profile, and outcomes of S. maltophilia keratitis.

METHODS

A retrospective review of records from 1987 to 2016 identified 26 eyes of 26 patients who were treated at the Bascom Palmer Eye Institute for an S. maltophilia corneal ulcer. Clinical data were analyzed as to predisposing factors, clinical presentation, antibiotic susceptibility, treatment selection, and clinical outcomes.

RESULTS

Median age at presentation was 65 years (range, 16-98). Twelve patients were using topical corticosteroids, 8 patients had a history of penetrating keratoplasty, and 9 were contact lens wearers. All patients received topical antibiotics, 2 required therapeutic penetrating keratoplasty, and 1 was enucleated. At presentation, 57.7% (15/26) of the patients had visual acuity of 20/400 or worse. At the final visit, only 30.4% (7/23) of the patients had visual acuity worse than 20/400, whereas 65.2% (15/23) of the patients had 20/100 or better. Almost all isolates (25/26, 96.2%) were susceptible to fluoroquinolones and 77.3% (17/22) of them to polymyxin B/trimethoprim. Only 33.3% (5/15) of the tested isolates were susceptible to aminoglycosides and 58.3% (7/12) to cephalosporins.

CONCLUSIONS

Infectious keratitis due to S. maltophilia presents a treatment challenge because of its resistance to aminoglycosides and cephalosporins, which are typically used for empiric broad-spectrum gram-negative coverage as fortified solutions. Fluoroquinolones and polymyxin B/trimethoprim should be considered instead in cases of S. maltophilia infection.