Pseudomonas aeruginosa acquisition on an intensive care unit: relationship between antibiotic selective pressure and patients' environment

Epidemiology of healthcare-associated Pseudomonas aeruginosa in intensive care units: are sink drains to blame?

BACKGROUND

Pseudomonas aeruginosa (PA) is a common cause of healthcare-associated infection (PA-HAI) in the intensive care unit (ICU).

AIM

To describe the epidemiology of PA-HAI in ICUs in Ontario, Canada, and to identify episodes of sink-to-patient PA transmission.

METHODS

This was a prospective cohort study of patients in six ICUs from 2018 to 2019, with retrieval of PA clinical isolates, and PA-screening of antimicrobial-resistant organism surveillance rectal swabs, and of sink drain, air, and faucet samples. All PA isolates underwent whole-genome sequencing. PA-HAI was defined using US National Healthcare Safety Network criteria. ICU-acquired PA was defined as PA isolated from specimens obtained ≥48 h after ICU admission in those with prior negative rectal swabs. Sink-to-patient PA transmission was defined as ICU-acquired PA with close genomic relationship to isolate(s) previously recovered from sinks in a room/bedspace occupied 3-14 days prior to collection date of the relevant patient specimen.

FINDINGS

Over ten months, 72 PA-HAIs occurred among 60/4263 admissions. The rate of PA-HAI was 2.40 per 1000 patient-ICU-days; higher in patients who were PA-colonized on admission. PA-HAI was associated with longer stay (median: 26 vs 3 days uninfected; P < 0.001) and contributed to death in 22/60 cases (36.7%). Fifty-eight admissions with ICU-acquired PA were identified, contributing 35/72 (48.6%) PA-HAIs. Four patients with five PA-HAIs (6.9%) had closely related isolates previously recovered from their room/bedspace sinks.

CONCLUSION

Nearly half of PA causing HAI appeared to be acquired in ICUs, and 7% of PA-HAIs were associated with sink-to-patient transmission. Sinks may be an under-recognized reservoir for HAIs.

Characteristics of Pseudomonas aeruginosa infection in intensive care unit before (2007-2010) and after (2011-2014) the beginning of an antimicrobial stewardship program

Objectives

To investigate the factors associated with Pseudomonas aeruginosa isolates in intensive care unit (ICU) before and after an antimicrobial stewardship program.

Materials

Monocentric retrospective cohort study. Patients admitted to the ICU in 2007-2014 were included. Characteristics of P. aeruginosa patients were compared to overall ICU population. Clinical and microbiological characteristics of P. aeruginosa patients before (2007-2010) and after (2011-2014) the beginning of the AMP were compared.

Results

Overall, 5,263 patients were admitted to the ICU, 274/5,263 (5%) had a P. aeruginosa isolate during their staying. In 2011-2014, the percentage P. aeruginosa isolates reduced (7% vs 4%, P ≤ .0001). Patients with P. aeruginosa had higher rates of in-hospital death (43% vs 20%, P < .0001) than overall ICU population. In 2011-2014, rates of multidrug-resistant (11% vs 2%, P = .0020), fluoroquinolone-resistant (35% vs 12%, P < .0001), and ceftazidime-resistant (23% vs 8%, P = .0009) P. aeruginosa reduced. Treatments by fluoroquinolones (36% vs 4%, P ≤ .0001), carbapenems (27% vs 9%, P = .0002), and third-generation cephalosporins (49% vs 12%, P ≤ .0001) before P. aeruginosa isolation reduced while piperacillin (0% vs 13%, P < .0001) and trimethoprim-sulfamethoxazole (8% vs 26%, P = .0023) increased. Endotracheal intubation reduced in 2011-2014 (61% vs 35%, P < .0001). Fluoroquinolone-resistance was higher in patients who received endotracheal intubation (29% vs 17%, P = .0197). Previous treatment by fluoroquinolones (OR = 2.94, P = .0020) and study period (2007-2010) (OR = 2.07, P = .0462) were the factors associated with fluoroquinolone-resistance at the multivariate analysis.

Conclusions

Antibiotic susceptibility in P. aeruginosa isolates was restored after the reduction of endotracheal intubation, fluoroquinolones, carbapenems, and third-generation cephalosporins and the increased use of molecules with a low ecological footprint, as piperacillin and trimethoprim-sulfamethoxazole.

Efficacy and safety of a structured de-escalation from antipseudomonal β-lactams in bloodstream infections due to Enterobacterales (SIMPLIFY): an open-label, multicentre, randomised trial

BACKGROUND

De-escalation from broad-spectrum to narrow-spectrum antibiotics is considered an important measure to reduce the selective pressure of antibiotics, but a scarcity of adequate evidence is a barrier to its implementation. We aimed to determine whether de-escalation from an antipseudomonal β-lactam to a narrower-spectrum drug was non-inferior to continuing the antipseudomonal drug in patients with Enterobacterales bacteraemia.

METHODS

An open-label, pragmatic, randomised trial was performed in 21 Spanish hospitals. Patients with bacteraemia caused by Enterobacterales susceptible to one of the de-escalation options and treated empirically with an antipseudomonal β-lactam were eligible. Patients were randomly assigned (1:1; stratified by urinary source) to de-escalate to ampicillin, trimethoprim-sulfamethoxazole (urinary tract infections only), cefuroxime, cefotaxime or ceftriaxone, amoxicillin-clavulanic acid, ciprofloxacin, or ertapenem in that order according to susceptibility (de-escalation group), or to continue with the empiric antipseudomonal β-lactam (control group). Oral switching was allowed in both groups. The primary outcome was clinical cure 3-5 days after end of treatment in the modified intention-to-treat (mITT) population, formed of patients who received at least one dose of study drug. Safety was assessed in all participants. Non-inferiority was declared when the lower bound of the 95% CI of the absolute difference in cure rate was above the -10% non-inferiority margin. This trial is registered with EudraCT (2015-004219-19) and ClinicalTrials.gov (NCT02795949) and is complete.

FINDINGS

2030 patients were screened between Oct 5, 2016, and Jan 23, 2020, of whom 171 were randomly assigned to the de-escalation group and 173 to the control group. 164 (50%) patients in the de-escalation group and 167 (50%) in the control group were included in the mITT population. 148 (90%) patients in the de-escalation group and 148 (89%) in the control group had clinical cure (risk difference 1·6 percentage points, 95% CI -5·0 to 8·2). The number of adverse events reported was 219 in the de-escalation group and 175 in the control group, of these, 53 (24%) in the de-escalation group and 56 (32%) in the control group were considered severe. Seven (5%) of 164 patients in the de-escalation group and nine (6%) of 167 patients in the control group died during the 60-day follow-up. There were no treatment-related deaths.

INTERPRETATION

De-escalation from an antipseudomonal β-lactam in Enterobacterales bacteraemia following a predefined rule was non-inferior to continuing the empiric antipseudomonal drug. These results support de-escalation in this setting.

FUNDING

Plan Nacional de I+D+i 2013-2016 and Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spanish Network for Research in Infectious Diseases; Spanish Clinical Research and Clinical Trials Platform, co-financed by the EU; European Development Regional Fund "A way to achieve Europe", Operative Program Intelligence Growth 2014-2020.

Unravelling the Distinctive Virulence Traits and Clonal Relationship among the Pseudomonas aeruginosa Isolates from Diabetic Patients

Infections with P. aeruginosa are three times more common in people with diabetes than in non-diabetic individuals. Investigations disclosing the distinguishing traits of P. aeruginosa strains to cause respiratory and wound infection in diabetics is limited. Wound swab and sputum from infected diabetic patients were used for the isolation of P. aeruginosa. The confirmed isolates were evaluated for their virulence factor production, antibiotic susceptibility, and clonal relationship. The study confirmed the increased virulence of sputum isolates characterized by their multidrug resistant nature, strong biofilm formation at 72h [(p<0.05) =0.003)] and 96h [(p<0.05) =0.002)] and elaboration of proteolytic enzymes (40.0%). Albeit the fact that wound isolates were less virulent than the sputum isolates, there was an increased siderophore production (77.0%). Nearly 90.0% of the isolates including sputum and wound were resistant to colistin. Random Amplified Polymorphic DNA analysis showed no distinct lineages of wound and sputum isolates. The study disclosed the higher prevalence of virulent P. aeruginosa in causing infection in the diabetics. No distinct lineages of the wound and sputum isolates indicated their ability to adapt to different host environments. To the best of our knowledge, this is the first study to show the difference in virulence traits among the P. aeruginosa strains isolated from sputum and wound of diabetic patients. Our study distinctly reveals the significance of periodic examination of antibiotic resistance and virulence factors of P. aeruginosa in order to recognize the possible co-regulatory mechanism involved in their expression.

Structural equation modelling the relationship between anti-fungal prophylaxis and Pseudomonas bacteremia in ICU patients

Purpose

Animal models implicate candida colonization facilitating invasive bacterial infections. The clinical relevance of this microbial interaction remains undefined and difficult to study directly. Observations from studies of anti-septic, antibiotic, anti-fungal, and non-decontamination-based interventions to prevent ICU acquired infection collectively serve as a natural experiment.

Methods

Three candidate generalized structural equation models (GSEM), with Candida and Pseudomonas colonization as latent variables, were confronted with blood culture and respiratory tract isolate data derived from 464 groups from 279 studies including studies of combined antibiotic and antifungal exposures within selective digestive decontamination (SDD) interventions.

Results

Introducing an interaction term between Candida colonization and Pseudomonas colonization substantially improved GSEM model fit. Model derived coefficients for singular exposure to anti-septic agents (− 1.23; − 2.1 to − 0.32), amphotericin (− 1.78; − 2.79 to − 0.78) and topical antibiotic prophylaxis (TAP; + 1.02; + 0.11 to + 1.93) versus Candida colonization were similar in magnitude but contrary in direction. By contrast, the model-derived coefficients for singular exposure to TAP, as with anti-septic agents, versus Pseudomonas colonization were weaker or non-significant. Singular exposure to amphotericin would be predicted to more than halve candidemia and Pseudomonas bacteremia incidences versus literature benchmarks for absolute differences of approximately one percentage point or less.

Conclusion

GSEM modelling of published data supports the postulated interaction between Candida and Pseudomonas colonization towards promoting bacteremia among ICU patients. This would be difficult to detect without GSEM modelling. The model indicates that anti-fungal agents have greater impact in preventing Pseudomonas bacteremia than TAP, which has no impact.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-022-00429-8.

Pseudomonas aeruginosa: a clinical and genomics update

Antimicrobial resistance (AMR) has become a global medical priority that needs urgent resolution. Pseudomonas aeruginosa is a versatile, adaptable bacterial species with widespread environmental occurrence, strong medical relevance, a diverse set of virulence genes and a multitude of intrinsic and possibly acquired antibiotic resistance traits. P. aeruginosa causes a wide variety of infections and has an epidemic-clonal population structure. Several of its dominant global clones have collected a wide variety of resistance genes rendering them multi-drug resistant (MDR) and particularly threatening groups of vulnerable individuals including surgical patients, immunocompromised patients, Caucasians suffering from cystic fibrosis (CF) and more. AMR and MDR especially are particularly problematic in P. aeruginosa significantly complicating successful antibiotic treatment. In addition, antimicrobial susceptibility testing (AST) of P. aeruginosa can be cumbersome due to its slow growth or the massive production of exopolysaccharides and other extracellular compounds. For that reason, phenotypic AST is progressively challenged by genotypic methods using whole genome sequences (WGS) and large-scale phenotype databases as a framework of reference. We here summarize the state of affairs and the quality level of WGS-based AST for P. aeruginosa mostly from clinical origin.

When Multidrug-Resistant Organism (MDRO)-Positive ICU Patient Isolation and Cohorting Is Not Feasible, What Comes Next?

Background The need for the implementation of an infection prevention strategy that included patient isolation and a cohorting procedure emerged in our ICU. Yet, isolation, as well as cohorting, were not feasible due to certain barriers associated with a high colonization pressure, open-plan ICU, inadequate bed separation, a limited number of isolation rooms, and nursing shortage. Despite these limitations, we tried to upgrade our ICU's infection prevention efforts by developing the "universal use of contact precautions approach" for infection prevention and control for all the patients with and without multidrug-resistant organisms (MDROs), cohorting, and single room isolation. The study aimed to evaluate the effectiveness of our approach. Methods A prospective cohort study using surveillance screening cultures for Methicillin-resistant Staphylococcus aureus (MRSA) and MDROs for a period of 18 weeks from October 1, 2018, to January 31, 2019. The main purpose of the approach was to isolate all patients (regardless of their MDRO/MRSA status) in their own bed space as if they were in an isolation room for the entire duration of their ICU hospitalization, in such a way as to prevent horizontal transmission of infection (infection acquisition) in our open-plan ICU.  Results Seventy-eight patients were admitted to our ICU for a total of 942 patient-days; a total of 432 swabs were collected during the study period. A total of 17 (21.8%) patients were admitted with a pre-existing infection while two (2.5%) patients acquired an infection during their ICU stay (one with Acinetobacter baumannii andone with Pseudomonas aeruginosa; 1.28 acquisition per 1000 patient-days). No transmission was documented for Klebsiella pneumoniae, Enterococcus faecalis, and Staphylococcus aureus. Conclusions Our MDRO acquisition rates suggested that the implementation of our infection control strategy potentially prevents the horizontal transmission of pathogens in an open-plan ICU, despite the high colonization pressure and the lack of isolation and cohorting procedures.

Clinico-epidemiological profile of Acinetobacter and Pseudomonas infections, and their antibiotic-resistant pattern in a tertiary care center, Western Nepal

Background:

Infections caused by Acinetobacter species and Pseudomonas species, especially multidrug-resistant (MDR) strains pose a serious management challenge with a public health threat.

Materials and Methods:

A hospital-based retrospective study of patients who were infected with Acinetobacter spp or Pseudomonas aeruginosa was carried out at Manipal Teaching Hospital from 2014 to 2016.

Results:

A total of 170 cases of infections with Acinetobacter spp. and 313 cases with Pseudomonas aeruginosa were studied. The rate of nosocomial infections was higher than non-nosocomial infections. ICU was found as the major hub for both the organisms; (53.5% of cases due to Acinetobacter spp. and 39.6% due to Pseudomonas aeruginosa). Most isolates were of respiratory tract origin (Acinetobacter 74.7% and Pseudomonas aeruginosa 65.8%). Percentage resistance of Acinetobacter spp. towards polymyxin B was found to be quite low (18.8%). Similarly, resistance rates of Pseudomonas aeruginosa against amikacin were also found to be low, i.e., 17.4%. A higher prevalence of multidrug resistance was seen among Acinetobacter spp than among Pseudomonas aeruginosa (75.9% vs. 60.1%). The hospital stay was longer for patients infected with MDR isolate (p=0.001 for Acinetobacter spp. and p=0.003 for Pseudomonas aeruginosa). The mortality rate was higher in infections due to Acinetobacter spp (15.9%) as compared to Pseudomonas aeruginosa (8.3%).

Conclusion:

This study reveals that infections caused by Acinetobacter species and Pseudomonas aeruginosa are associated with prolonged hospital stay and high in-hospital mortality. These emphasize the need for prudent use of antibiotics and aggressive infection control strategies.

Variable impact of an antimicrobial stewardship programme in three intensive care units: time-series analysis of 2012-2017 surveillance data

BACKGROUND

Preprescription authorization (PPA) and postprescription review with feedback (PPRF) were successively implemented in 2012 and 2016 in our 1500-bed hospital.

AIM

The impact of PPA and PPRF on carbapenems use and resistance levels of Pseudomonas aeruginosa was assessed in three intensive care units (ICUs).

METHODS

Carbapenems use (in DDDs/1000 occupied bed-days) and resistance of P. aeruginosa (percentage of non-susceptible (I+R) isolates to imipenem and/or meropenem) were analysed using a controlled interrupted time-series method. Two periods were compared: 2012-2015 (PPA) and 2016-2017 (PPA+PPRF). Models were adjusted on the annual incidence of extended-spectrum β-lactamase-producing enterobacteriacae.

FINDINGS

Carbapenem use was stable over the PPA period in all ICUs, with a significant change of slope over the PPA+PPRF period only in ICU1 (β2 = -12.8, 95% confidence interval (CI) = -19.5 to -6.1). There was a switch from imipenem to meropenem during the PPA period in all three units. Resistances of P. aeruginosa were stable over the study period in ICU1 and ICU2, and significantly decreased over the PPA+PPRF period in ICU3 (β2 = -0.18, CI = -0.3 to -0.03).

CONCLUSION

In real-life conditions and with the same antimicrobial stewardship programme (AMSP) led by a single team, the impact of PPRF was heterogeneous between ICUs. Factors driving the impact of AMSPs should be further assessed in comparable settings through real-life data, to target where they could prove cost-effective.

Prevention of hospital-acquired pneumonia

PURPOSE OF REVIEW

Hospital-acquired pneumonia (HAP) is the leading cause of death from hospital-acquired infection. Little work has been done on strategies for prevention of HAP. This review aims to describe potential HAP prevention strategies and the evidence supporting them. Oral care and aspiration precautions may attenuate some risk for HAP. Oral and digestive decontamination with antibiotics may be effective but could increase risk for resistant organisms. Other preventive measures, including isolation practices, remain theoretical or experimental.

RECENT FINDINGS

Hospital-acquired pneumonia occurs because of pharyngeal colonization with pathogenic organisms and subsequent aspiration of these pathogens.

SUMMARY

Most potential HAP prevention strategies remain unproven.

Carbapenem-Nonsusceptible Pseudomonas aeruginosa Isolates from Intensive Care Units in the United States: a Potential Role for New β-Lactam Combination Agents

Pseudomonas aeruginosa, a frequent pathogen in the intensive care unit (ICU), has the propensity to develop antibiotic resistance. In particular, carbapenem-nonsusceptible (NS) P. aeruginosa poses tremendous challenges, and new antibiotics will be needed to treat this phenotype. Here we determine carbapenem nonsusceptibility rates for contemporary P. aeruginosa isolates from U.S. ICUs and in vitro activities of new β-lactam combination agents. Between July 2017 and June 2018, consecutive nonduplicate P. aeruginosa isolates from blood and respiratory tract sources were recovered from patients admitted to the ICUs of 36 geographically diverse U.S. hospitals. Antimicrobial susceptibility to the following antipseudomonal agents was tested: ceftazidime, imipenem, meropenem, ceftazidime-avibactam, and imipenem-relebactam (an investigational β-lactam/β-lactamase inhibitor). MICs and susceptibility rates were measured using Clinical and Laboratory Standards Institute reference broth microdilution methodology. Among the 538 consecutive ICU P. aeruginosa isolates collected, carbapenem nonsusceptibility was observed for 35% of the isolates and was more common among respiratory tract versus bloodstream specimens. Susceptibility rates, MIC₅₀ values, and MIC₉₀ values were as follows: ceftazidime-avibactam, 92.8%, 2 μg/ml, and 8 μg/ml; imipenem-relebactam, 91.5%, 0.25 μg/ml, and 2 μg/ml; ceftazidime, 77.1%, 4 μg/ml, and 64 μg/ml; meropenem, 72.7%, 1 μg/ml, and 16 μg/ml; imipenem, 67.1%, 2 μg/ml, and 16 μg/ml. Most (>75%) of the carbapenem-NS isolates were susceptible to ceftazidime-avibactam and imipenem-relebactam. In these U.S. hospital ICUs, carbapenem-NS P. aeruginosa isolates from respiratory sources were frequently observed. Novel β-lactam combination agents appear to retain active in vitro susceptibility profiles against these isolates and may play a role in the treatment of infections caused by carbapenem-NS P. aeruginosa strains.

Perioperative prophylaxis with ertapenem reduced infections caused by extended-spectrum betalactamase-producting Enterobacteriaceae after kidney transplantation

Backgound

In recent years we have witnessed an increase in infections due to multidrug-resistant organisms in kidney transplant recipients (KTR). In our setting, we have observed a dramatic increase in infections caused by extended-spectrum betalactamase-producing (ESBL) Enterobacteriaceae in KTR. In 2014 we changed surgical prophylaxis from Cefazolin 2 g to Ertapenem 1 g.

Methods

We compared bacterial infections and their resistance phenotype during the first post-transplant month with an historical cohort collected during 2013 that had received Cefazolin.

Results

During the study period 110 patients received prophylaxis with Cefazolin and 113 with Ertapenem. In the Ertapenem cohort we observed a non-statistically significant decrease in the percentage of early bacterial infection from 57 to 47%, with urine being the most frequent source in both. The frequency of infections caused by Enterobacteriaceae spp. decreased from 64% in the Cefazolin cohort to 36% in the Ertapenem cohort (p = 0.005). In addition, percentage of ESBL-producing strains decreased from 21 to 8% of all Enterobacteriaceae isolated (p = 0.015). After adjusted in multivariate Cox regression analysis, male sex (HR 0.16, 95%CI: 0.03–0.75), cefazolin prophylaxis (HR 4.7, 95% CI: 1.1–22.6) and acute rejection (HR 14.5, 95% CI: 1.3–162) were associated to ESBL- producing Enterobacteriaceae infection.

Conclusions

Perioperative antimicrobial prophylaxis with a single dose of Ertapenem in kidney transplant recipients reduced the incidence of early infections due to ESBL-producing Enterobacteriaceae without increasing the incidence of other multidrug-resistant microorganisms or C. difficile.

Impact of a multimodal strategy combining a new standard of care and restriction of carbapenems, fluoroquinolones and cephalosporins on antibiotic consumption and resistance of Pseudomonas aeruginosa in a French intensive care unit

This study aimed to assess whether post-prescription review and feedback (PPRF) of all antibiotics, with restriction of carbapenems, fluoroquinolones and third-generation cephalosporins (3GCs), along with a change in medical standard of care impacted antibiotic consumption and bacterial antimicrobial resistance in a French medical/surgical intensive care unit (ICU). A 4-year before (2007-2010) and after (2011-2014) retrospective comparative study was performed. Antibiotic consumption was evaluated in defined daily doses per 1000 patient-days. The rates of Pseudomonas aeruginosa resistance to piperacillin, ceftazidime, ciprofloxacin, imipenem and amikacin and of AmpC-hyperproducing group 3 Enterobacteriaceae were assessed. Consumption of fluoroquinolones decreased by -85%, carbapenems by -58%, 3GCs by -50% and glycopeptides by -66% (P ≤ 0.0001). Consumption of penicillins with and without β-lactamase inhibitors increased by +72% and +78%, sulfonamides by +172% and macrolides by +267% (P < 0.0001). Pseudomonas aeruginosa resistance rates for all antibiotics tested and the proportion of AmpC-hyperproducing group 3 Enterobacteriaceae decreased (P ≤ 0.01). The median length of stay, use of vasopressors and invasive mechanical ventilation decreased, and the use of renal replacement therapy increased (P < 0.05). The initial severity score (SAPS II) increased (P < 0.01) due to changes in practice, with no impact on in-hospital mortality (P = 0.07). In conclusion, changes in medical care along with PPRF and a restriction of high ecological impact antibiotics were associated with a shift towards the consumption of low ecological impact antibiotics in an ICU. Rates of resistant P. aeruginosa and of AmpC-hyperproducing group 3 Enterobacteriaceae decreased simultaneously.

Impact of Real-Time Therapeutic Drug Monitoring on the Prescription of Antibiotics in Burn Patients Requiring Admission to the Intensive Care Unit

As pharmacokinetics after burn trauma are difficult to predict, we conducted a 3-year prospective, monocentric, randomized, controlled trial to determine the extent of under- and overdosing of antibiotics and further evaluate the impact of systematic therapeutic drug monitoring (TDM) with same-day real-time dose adaptation to reach and maintain antibiotic concentrations within the therapeutic range. Forty-five consecutive burn patients treated with antibiotics were prospectively screened. Forty fulfilled the inclusion criteria; after one patient refused to participate and one withdrew consent, 19 were randomly assigned to an intervention group (patients with real-time antibiotic concentration determination and subsequent adaptations) and 19 were randomly assigned to a standard-of-care group (patients with antibiotic administration at the physician's discretion without real-time TDM). Seventy-three infection episodes were analyzed. Before the intervention, only 46/82 (56%) initial trough concentrations fell within the range. There was no difference between groups in the initial trough concentrations (adjusted hazard ratio = 1.39 [95% confidence interval {CI}, 0.81 to 2.39], P = 0.227) or the time to reach the target. However, thanks to real-time dose adjustments, the trough concentrations of the intervention group remained more within the predefined range (57/77 [74.0%] versus 48/85 [56.5%]; adjusted odd ratio [OR] = 2.34 [95% CI, 1.17 to 4.81], P = 0.018), more days were spent within the target range (193 days/297 days on antibiotics [65.0%] versus 171 days/311 days in antibiotics [55.0%]; adjusted OR = 1.64 [95% CI, 1.16 to 2.32], P = 0.005), and fewer results were below the target trough concentrations (25/118 [21.2%] versus 44/126 [34.9%]; adjusted OR = 0.47 [95% CI, 0.26 to 0.87], P = 0.015). No difference in infection outcomes was observed between the study groups. Systematic TDM with same-day real-time dose adaptation was effective in reaching and maintaining therapeutic antibiotic concentrations in infected burn patients, which prevented both over- and underdosing. A larger multicentric study is needed to further evaluate the impact of this strategy on infection outcomes and the emergence of antibiotic resistance during long-term burn treatment. (This study was registered with the ClinicalTrials.gov platform under registration no. NCT01965340 on 27 September 2013.).

Frequency, associated factors and outcome of multi-drug-resistant intensive care unit-acquired pneumonia among patients colonized with extended-spectrum β-lactamase-producing Enterobacteriaceae

Background

We assessed prevalence, associated factors and prognosis of extended-spectrum beta-lactamase-producing Enterobacteriaceae pneumonia acquired in intensive care unit (ESBL-PE pneumonia) among carriers. Variables associated with nosocomial pneumonia caused by carbapenem-resistant bacteria (CRB) were also assessed.

Methods

A 6-year prospective study (May 2009–March 2015) in the medical ICU of an 850-bed university-affiliated hospital was conducted.

Results

Of the 6303 patients admitted, 843 (13.4%) had ESBL-PE carriage detected. Among carriers, 111 (13%) patients developed ICU-acquired pneumonia of whom 48 (43%) had ESBL-PE pneumonia (6% of carriers). By multivariable analysis, SAPS II at admission >43 [OR 2.81 (1.16–6.79)] and colonization with Enterobacter sp. or K. pneumoniae species [OR 10.96 (2.93–41.0)] were independent predictive factors for ESBL-PE pneumonia in colonized patients, whereas receipt of >2 days of amoxicillin/clavulanic acid during the ICU stay [OR 0.24 (0.08–0.71)] was protective. Patients with ESBL-PE pneumonia had a higher SOFA score (p = 0.037) and more frequent septic shock at pneumonia onset (p = 0.047). However, ESBL-PE pneumonia was not an independent predictor of mortality. Twenty-five patients had pneumonia caused by CRB. Chronic renal insufficiency, administration of third-generation cephalosporin within the past 3 months, acute respiratory distress syndrome before pneumonia and prior therapy with a carbapenem or fluoroquinolones were associated with CRB pneumonia in this selected population.

Conclusions

Although few ESBL-PE carriers developed ESBL-PE pneumonia overall, a high proportion of pneumonia were caused by ESBL-PE in carriers developing ICUAP. ESBL-PE pneumonia was not an independent predictor of mortality. As pneumonia caused by CRB is increasing, knowledge of factors associated with ESBL-PE or CRB pneumonia may help empiric therapy of pneumonia among ESBL-PE carriers.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0283-4) contains supplementary material, which is available to authorized users.

Benefits and unintended consequences of antimicrobial de-escalation: Implications for stewardship programs

Sequential antimicrobial de-escalation aims to minimize resistance to high-value broad-spectrum empiric antimicrobials by switching to alternative drugs when testing confirms susceptibility. Though widely practiced, the effects de-escalation are not well understood. Definitions of interventions and outcomes differ among studies. We use mathematical models of the transmission and evolution of Pseudomonas aeruginosa in an intensive care unit to assess the effect of de-escalation on a broad range of outcomes, and clarify expectations. In these models, de-escalation reduces the use of high-value drugs and preserves the effectiveness of empiric therapy, while also selecting for multidrug-resistant strains and leaving patients vulnerable to colonization and superinfection. The net effect of de-escalation in our models is to increase infection prevalence while also increasing the probability of effective treatment. Changes in mortality are small, and can be either positive or negative. The clinical significance of small changes in outcomes such as infection prevalence and death may exceed more easily detectable changes in drug use and resistance. Integrating harms and benefits into ranked outcomes for each patient may provide a way forward in the analysis of these tradeoffs. Our models provide a conceptual framework for the collection and interpretation of evidence needed to inform antimicrobial stewardship.

Pseudomonas spp. ISOLATED FROM THE ORAL CAVITY OF HEALTHCARE WORKERS FROM AN ONCOLOGY HOSPITAL IN MIDWESTERN BRAZIL

This cross-sectional study, performed in an oncology hospital in Goiania, aimed to characterize the prevalence of oral colonization and antimicrobial susceptibility of Pseudomonas spp. isolated from the saliva of healthcare workers. Microorganisms were subjected to biochemical tests, susceptibility profile, and phenotypic detection. Of 76 participants colonized with Gram negative bacilli, 12 (15.8%) harbored Pseudomonas spp. Of all isolates, P. aeruginosa (75.0%), P. stutzeri (16.7%), and P. fluorescens (8.3%), were resistant to cefoxitin, and therefore likely to be AmpC producers. The results are clinically relevant and emphasize the importance of surveillance to minimize bacterial dissemination and multiresistance.

In vivo evolution of resistance of Pseudomonas aeruginosa strains isolated from patients admitted to an intensive care unit: mechanisms of resistance and antimicrobial exposure

OBJECTIVES

The main objective of this study was to investigate the relationship among the in vivo acquisition of antimicrobial resistance in Pseudomonas aeruginosa clinical isolates, the underlying molecular mechanisms and previous exposure to antipseudomonal agents.

METHODS

PFGE was used to study the molecular relatedness of the strains. The MICs of ceftazidime, cefepime, piperacillin/tazobactam, imipenem, meropenem, ciprofloxacin and amikacin were determined. Outer membrane protein profiles were assessed to study OprD expression. RT-PCR was performed to analyse ampC, mexB, mexD, mexF and mexY expression. The presence of mutations was analysed through DNA sequencing.

RESULTS

We collected 17 clonally related paired isolates [including first positive samples (A) and those with MICs increased ≥4-fold (B)]. Most B isolates with increased MICs of imipenem, meropenem and ceftazidime became resistant to these drugs. The most prevalent resistance mechanisms detected were OprD loss (65%), mexB overexpression (53%), ampC derepression (29%), quinolone target gene mutations (24%) and increased mexY expression (24%). Five (29%) B isolates developed multidrug resistance. Meropenem was the most frequently (71%) received treatment, explaining the high prevalence of oprD mutations and likely mexB overexpression. Previous exposure to ceftazidime showed a higher impact on selection of increased MICs than previous exposure to piperacillin/tazobactam.

CONCLUSIONS

Stepwise acquisition of resistance has a critical impact on the resistance phenotypes of P. aeruginosa, leading to a complex scenario for finding effective antimicrobial regimens. In the clinical setting, meropenem seems to be the most frequent driver of multidrug resistance development, while piperacillin/tazobactam, in contrast to ceftazidime, seems to be the β-lactam least associated with the selection of resistance mechanisms.

The role of systemic antibiotics in acquiring respiratory tract colonization with gram-negative bacteria in intensive care patients: a nested cohort study

OBJECTIVE

Colonization of the respiratory tract with Gram-negative bacteria in intensive care patients increases the risk of subsequent infections. Application of systemic antibiotics may prevent colonization with Gram-negative bacteria, but this effect has never been quantified. The objective of this study was to determine associations between systemic antibiotic use and acquisition of respiratory tract colonization with Gram-negative bacteria in ICUs.

DESIGN

A nested cohort study.

SETTING

A university hospital and a teaching hospital.

PATIENTS

Patients with ICU stay of more than 48 hours and absence of respiratory tract colonization with Gram-negative bacteria on ICU admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Acquisition was determined through protocolized surveillance. Associations were investigated with Cox regression models with antibiotics as a time-dependent covariate. In all, 250 of 481 patients (52%) acquired respiratory tract colonization with Gram-negative bacteria after a median of 5 days (interquartile range, 3-8 d) (acquisition rate, 77.1/1,000 patient-days at risk). Antibiotic exposure during ICU admission was present in 78% and 72% of the patients with and without acquired Gram-negative bacteria colonization, respectively. In Kaplan-Meier curve analysis, the median times to acquisition of Gram-negative bacteria were 9 days (95% CI, 7.9-10.1) and 6 days (95% CI, 4.8-7.2) in patients receiving and not receiving antibiotics, respectively. In time varying Cox regression analysis, however, the association between acquired colonization and systemic antibiotics was not statistically significant (hazard ratio, 0.90; 95% CI, 0.70-1.16).

CONCLUSIONS

Among patients not colonized with Gram-negative bacteria in the respiratory tract at admission to ICU, systemic antibiotics during ICU stay were not associated with a reduction in acquisition of Gram-negative bacteria carriage in the respiratory tract during the ICU stay.

Acquisition of Pseudomonas aeruginosa and its resistance phenotypes in critically ill medical patients: role of colonization pressure and antibiotic exposure

INTRODUCTION

The objective of this work was to investigate the risk factors for the acquisition of Pseudomonas aeruginosa and its resistance phenotypes in critically ill patients, taking into account colonization pressure.

METHODS

We conducted a prospective cohort study in an 8-bed medical intensive care unit during a 35-month period. Nasopharyngeal and rectal swabs and respiratory secretions were obtained within 48 hours of admission and thrice weekly thereafter. During the study, a policy of consecutive mixing and cycling periods of three classes of antipseudomonal antibiotics was followed in the unit.

RESULTS

Of 850 patients admitted for ≥ 3 days, 751 (88.3%) received an antibiotic, 562 of which (66.1%) were antipseudomonal antibiotics. A total of 68 patients (8%) carried P. aeruginosa upon admission, and among the remaining 782, 104 (13%) acquired at least one strain of P. aeruginosa during their stay. Multivariate analysis selected shock (odds ratio (OR) = 2.1; 95% confidence interval (CI), 1.2 to 3.7), intubation (OR = 3.6; 95% CI, 1.7 to 7.5), enteral nutrition (OR = 3.6; 95% CI, 1.8 to 7.6), parenteral nutrition (OR = 3.9; 95% CI, 1.6 to 9.6), tracheostomy (OR = 4.4; 95% CI, 2.3 to 8.3) and colonization pressure >0.43 (OR = 4; 95% CI, 1.2 to 5) as independently associated with the acquisition of P. aeruginosa, whereas exposure to fluoroquinolones for >3 days (OR = 0.4; 95% CI, 0.2 to 0.8) was protective. In the whole series, prior exposure to carbapenems was independently associated with carbapenem resistance, and prior amikacin use predicted piperacillin-tazobactam, fluoroquinolone and multiple-drug resistance.

CONCLUSIONS

In critical care settings with a high rate of antibiotic use, colonization pressure and non-antibiotic exposures may be the crucial factors for P. aeruginosa acquisition, whereas fluoroquinolones may actually decrease its likelihood. For the acquisition of strains resistant to piperacillin-tazobactam, fluoroquinolones and multiple drugs, exposure to amikacin may be more relevant than previously recognized.

Epidemiology of Clostridium difficile infection: results of a hospital-based study in Krakow, Poland

Over the past two decades Clostridium difficile infection (CDI) has appeared as a major public health threat. We performed a retrospective study based on the records of patients hospitalized for CDI at the University Hospital in Krakow, Poland, between 2008 and 2014. In the study period, CDI occurred in 1009 individuals. There were 790 (78%) individuals who developed infection only once, whereas 219 (22%) developed infection more than once. The percentage of deaths within 14 days of CDI confirmation was 2·4%, with a mean age of 74·2 ± 15·9 years. Crude mortality was 12·9% in medical wards, 5·6% for surgical wards and 27·7% in the ICU setting. The time span between diagnosis and death was 5·1 days on average. Between 2008 and 2012 a 6·5-fold increase of CDI frequency with a posterior stabilization and even reduction in 2013 and 2014 was observed. According to the data analysed, 2/3 patients in our population developed CDI during their hospitalization even though they were admitted for different reasons. Medical wards pose a significantly higher risk of CDI than the surgical ones. Age is a risk factor for CDI recurrence. In the case of patients who died, death occurred shortly after diagnosis. The first CDI episode poses much higher risk of mortality than the consecutive ones.

The "genomic storm" induced by bacterial endotoxin is calmed by a nuclear transport modifier that attenuates localized and systemic inflammation

Lipopolysaccharide (LPS) is a potent microbial virulence factor that can trigger production of proinflammatory mediators involved in the pathogenesis of localized and systemic inflammation. Importantly, the role of nuclear transport of stress responsive transcription factors in this LPS-generated "genomic storm" remains largely undefined. We developed a new nuclear transport modifier (NTM) peptide, cell-penetrating cSN50.1, which targets nuclear transport shuttles importin α5 and importin β1, to analyze its effect in LPS-induced localized (acute lung injury) and systemic (lethal endotoxic shock) murine inflammation models. We analyzed a human genome database to match 46 genes that encode cytokines, chemokines and their receptors with transcription factors whose nuclear transport is known to be modulated by NTM. We then tested the effect of cSN50.1 peptide on proinflammatory gene expression in murine bone marrow-derived macrophages stimulated with LPS. This NTM suppressed a proinflammatory transcriptome of 37 out of 84 genes analyzed, without altering expression of housekeeping genes or being cytotoxic. Consistent with gene expression analysis in primary macrophages, plasma levels of 23 out of 26 LPS-induced proinflammatory cytokines, chemokines, and growth factors were significantly attenuated in a murine model of LPS-induced systemic inflammation (lethal endotoxic shock) while the anti-inflammatory cytokine, interleukin 10, was enhanced. This anti-inflammatory reprogramming of the endotoxin-induced genomic response was accompanied by complete protection against lethal endotoxic shock with prophylactic NTM treatment, and 75% protection when NTM was first administered after LPS exposure. In a murine model of localized lung inflammation caused by direct airway exposure to LPS, expression of cytokines and chemokines in the bronchoalveolar space was suppressed with a concomitant reduction of neutrophil trafficking. Thus, calming the LPS-triggered "genomic storm" by modulating nuclear transport with cSN50.1 peptide attenuates the systemic inflammatory response associated with lethal shock as well as localized lung inflammation.

Respiratory infections in patients undergoing mechanical ventilation

Lower respiratory tract infections in mechanically ventilated patients are a frequent cause of antibiotic treatment in intensive-care units. These infections present as severe sepsis or septic shock with respiratory dysfunction in intubated patients. Purulent respiratory secretions are needed for diagnosis, but distinguishing between pneumonia and tracheobronchitis is not easy. Both presentations are associated with longlasting mechanical ventilation and extended intensive-care unit stay, providing a rationale for antibiotic treatment initiation. Differentiation of colonisers from true pathogens is difficult, and microbiological data show Staphylococcus aureus and Pseudomonas aeruginosa to be of great concern because of clinical outcomes and therapeutic challenges. Key management issues include identification of the pathogen, choice of initial empirical antibiotic, and decisions with regard to the resolution pattern.

Risk factors for Pseudomonas aeruginosa acquisition in intensive care units: a prospective multicentre study

BACKGROUND

Pseudomonas aeruginosa is a major nosocomial pathogen in intensive care units (ICUs); however, endogenous versus exogenous origin of contamination remains unclear.

AIM

To identify individual and environmental ICU risk factors for P. aeruginosa acquisition.

METHODS

A five-month prospective multicentric study was performed in ten French ICUs. Adult patients hospitalized in ICU for ≥ 24 h were included and screened for P. aeruginosa colonization on admission, weekly and before discharge. P. aeruginosa acquisition was defined by a subsequent colonization or infection if screening swabs on admission were negative. Water samples were obtained weekly on water taps of the ICUs. Data on patient characteristics, invasive devices exposure, antimicrobial therapy, P. aeruginosa water and patient colonization pressures, and ICU characteristics were collected. Hazard ratios (HRs) were estimated using multivariate Cox model.

FINDINGS

Among the 1314 patients without P. aeruginosa on admission, 201 (15%) acquired P. aeruginosa during their ICU stay. Individual characteristics significantly associated with P. aeruginosa acquisition were history of previous P. aeruginosa infection or colonization, cumulative duration of mechanical ventilation and cumulative days of antibiotics not active against P. aeruginosa. Environmental risk factors for P. aeruginosa acquisition were cumulative daily ward 'nine equivalents of nursing manpower use score' (NEMS) [hazard ratio (HR): 1.47 for ≥ 30 points; 95% confidence interval (CI): 1.06-2.03] and contaminated tap water in patient's room (HR: 1.76; CI: 1.09-2.84).

CONCLUSION

Individual risk factors and environmental factors for which intervention is possible were identified for P. aeruginosa acquisition.

Association between healthcare water systems and Pseudomonas aeruginosa infections: a rapid systematic review

BACKGROUND

Pseudomonas aeruginosa is an opportunistic pathogen with a particular propensity to cause disease in the immunocompromised. Water systems have been reported to contribute to P. aeruginosa transmission in healthcare settings.

AIM

To systematically assess the evidence that healthcare water systems are associated with P. aeruginosa infection; to review aspects of design that can increase their potential to act as a reservoir; and to compare the efficacy of strategies for eradicating contamination and preventing infection.

METHODS

A rapid review methodology with a three-step search strategy was used to identify published studies. Scientific advisors were used to identify unpublished studies.

FINDINGS

Twenty-five relevant studies were included. There was plausible evidence of transmission of P. aeruginosa from water systems to patients and vice versa, although no direct evidence to explain the exact mode of transfer. Two studies provided plausible evidence for effective interventions: point-of-use filters and increasing chlorine disinfection. Non-touch taps and aspects of water system design were identified as probable risk factors for P. aeruginosa biofilm formation and subsequent transmission to patients. Poor hand hygiene or compliance with contact precautions were identified as potential contributory factors; plausible evidence to confirm this was not available.

CONCLUSIONS

Water systems can act as a source of P. aeruginosa infection in healthcare settings, although the route of transmission is unclear. Contamination appears to be confined to the distal ends of a water system and can persist for prolonged periods. Further studies are required to establish effective methods of preventing transmission and eradicating P. aeruginosa from plumbing systems.

A potential role of aminoglycoside resistance in endemic occurrence of Pseudomonas aeruginosa strains in lower airways of mechanically ventilated patients

Altogether, 98 Pseudomonas aeruginosa isolates from a 5-bed intensive care unit were fingerprinted with pulsed-field gel electrophoresis and tested for aminoglycoside resistance genes aac(6')-Ib, aac(3″)-IIa, ant(2″)-Ia, armA, rmtA, and rmtB and integrons and virulence genes/operons phzI, phzII, phzM, phzS, apr, lasB, plcH, plcN, pilA, algD, toxA, exoS, exoT, exoY, and exoU. Two major clusters were identified (49 and 19 isolates), harbouring aac(6')-Ib, blaPSE-1, and ant(3″)-Ia genes or ant(2″)-Ia gene, respectively, on a class I integron. Most virulence genes except for exoU and pilA were found. Only 1 isolate of the minor cluster (8 isolates) and 1 of the 22 sporadic isolates carried integrons (without gene cassettes); virulence profile was highly variable. Comparing the resistance and virulence patterns of endemic and sporadic isolates suggests that integron-borne aminoglycoside resistance is more closely associated with the frequency than virulence. Consequently, aminoglycoside usage may have played a role in maintenance of the endemic clones.

Pseudomonas in augmented care: should we worry?

The problem of Pseudomonas as a nosocomial pathogen is not new, with some authors dating its onset to the start of the antimicrobial era, although other factors, such as the growth of intensive or augmented care, have a part to play. This paper outlines the historical and environmental issues that may be associated with a potential increase in the incidence of this difficult-to-treat pathogen.

Linking antimicrobial prescribing to antimicrobial resistance in the ICU: before and after an antimicrobial stewardship program

Antimicrobials are an effective treatment for many types of infections, but their overuse promotes the spread of resistant microorganisms that defy conventional treatments and complicate patient care. In 2009, an antimicrobial stewardship program was implemented at Mount Sinai Hospital (MSH, Toronto, Canada). Components of this program were to alter the fraction of patients prescribed antimicrobials, to shorten the average duration of treatment, and to alter the types of antimicrobials prescribed. These components were incorporated into a mathematical model that was compared to data reporting the number of patients colonized with Pseudomonas aeruginosa and the number of patients colonized with antimicrobial-resistant P. aeruginosa first isolates before and after the antimicrobial stewardship program. Our analysis shows that the reported decrease in the number of patients colonized was due to treating fewer patients, while the reported decrease in the number of patients colonized with resistant P. aeruginosa was due to the combined effect of treating fewer patients and altering the types of antimicrobials prescribed. We also find that shortening the average duration of treatment was unlikely to have produced any noticeable effects and that further reducing the fraction of patients prescribed antimicrobials would most substantially reduce P. aeruginosa antimicrobial resistance in the future. The analytical framework that we derive considers the effect of colonization pressure on infection spread and can be used to interpret clinical antimicrobial resistance data to assess different aspects of antimicrobial stewardship within the ecological context of the intensive care unit.