Carbapenem-resistant gram-negative bacterial infections and risk factors for acquisition in a Kenyan intensive care unit

BACKGROUND

Carbapenem-resistant Gram-negative bacteria (CR-GNB) are a critical public health threat globally; however, there are inadequate surveillance data, especially in intensive care units (ICU), to inform infection prevention and control in many resource-constrained settings. Here, we assessed the prevalence of CR-GNB infections and risk factors for acquisition in a Kenyan ICU.

METHODS

A hospital-based cross-sectional study design was adopted, recruiting 162 patients clinically presenting with bacterial infection after 48 h of ICU admission, from January to October 2022 at the Nairobi West Hospital, Kenya. Demographics and clinical data were collected by case report form. The type of sample collected, including blood, tracheal aspirate, ascitic tap, urine, stool, and sputum depended on the patient's clinical presentation and were transported to the hospital Microbiology laboratory in a cool box for processing within 2 h. The samples were analyzed by cultured and BD Phoenix system used for isolates' identity and antimicrobial susceptibility.

RESULTS

CR-GNB infections prevalence was 25.9% (42/162), with Klebsiella pneumoniae (35.7%, 15/42) and Pseudomonas aeruginosa (26.2%, 11/42) predominating. All isolates were multidrug-resistant (MDR). P. aeruginosa and A. baumannii were 100% colistin-resistant, while K. pneumoniae (33.3%) was tigecycline-resistant. History of antibiotics (aOR = 3.40, p = 0.005) and nasogastric tube (NGT) use (aOR = 5.84, p = < 0.001) were the risk factors for infection.

CONCLUSION

Our study highlights high MDR- and CR-GNB infections in ICU, with prior antibiotic exposure and NGT use as risk factors, and diminishing clinical value of colistin and tigecycline. In this study setting and beyond, strict implementation of antimicrobial stewardship programs and adherence to infection prevention and control through monitoring, evaluation and feedback are warranted to curb CR-GNB infections, especially among the risk groups.

Efficacy and mortality of ceftazidime/avibactam-based regimens in carbapenem-resistant Gram-negative bacteria infections: A retrospective multicenter observational study

OBJECTIVES

Limited data on clinical and microbiological efficacy, patient mortality, and other associated factors are available for ceftazidime/avibactam (CAZ/AVI)-based regimens for carbapenem-resistant Gram-negative bacteria (CR-GNB). This study aimed to assess these issues retrospectively using multicenter data.

METHODS

This multicenter study included CR-GNB infected patients treated with CAZ/AVI-based regimens for more than three days. Patient characteristics, bacterial culture reports, drug-sensitivity test results, and antibiotic use, including CAZ/AVI use, were extracted from the patient's clinical records. The clinical and microbiological efficacy of the combined drug regimen and patient mortality were evaluated according to corresponding definitions. Univariate and multivariate logistic regressions were performed to explore the efficacy and mortality-related factors.

RESULTS

A total of 183 patients with CR-GNB infection were considered for the analysis according to the inclusion and exclusion criteria. After the treatment of CAZ/AVI-based regimens, the clinical efficacy was 75.4 %. The 7-day microbial efficacy and clearance rate after treatment were 43.7 % and 66.0 %, respectively. Moreover, 30-day all-cause and in-hospital mortality were 11.5 % and 14.2 %, respectively. Harboring renal dysfunction (creatinine clearance rate (CCR) of<20 mL/min), cardiovascular diseases, and digestive system diseases were independent risk factors for poor clinical efficacy of CAZ/AVI-based regimens. Bloodstream infection (BSI), patients with the adjusted doses of CAZ/AVI, and CAZ/AVI co-administration with carbapenem were independently associated factors of bacterial clearance by CAZ/AVI-based regimens. Age, total hospital stays, use of mechanical ventilation, and cumulative CAZ/AVI dose were independent factors associated with all-cause mortality.

CONCLUSION

CAZ/AVI was an effective drug in treating CR-GNB infection. CAZ/AVI that is mostly excreted by the kidney and is accumulated in renal impairment should be renally adjusted. Renal dysfunction and the adjusted dose of CAZ/AVI were associated with efficacy. Clinicians should individualize CAZ/AVI regimen and dose by the level of renal function to achieve optimal efficacy and survival. The efficacy of CAZ/AVI in the treatment of CR-GNB infection, as well as the implementation of individualized precision drug administration of CAZ/AVI according to patients' different infection sites, renal function, bacterial types, bacterial resistance mechanisms, blood concentration monitoring and other conditions need to be further studied in multicenter.

Clinical effectiveness of tigecycline in combination therapy against nosocomial pneumonia caused by CR-GNB in intensive care units: a retrospective multi-centre observational study

BACKGROUND

Tigecycline has in vitro bacteriostatic activity against a broad spectrum of bacteria, including carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the role of tigecycline in treatment of nosocomial pneumonia caused by CR-GNB remains controversial and clinical evidences are limited. We aimed to investigate the clinical benefits of tigecycline as part of the combination treatment of nosocomial CR-GNB pneumonia in intensive care unit (ICU).

METHODS

This multi-centre cohort study retrospectively enrolled ICU-admitted patients with nosocomial pneumonia caused by CR-GNB. Patients were categorized based on whether add-on tigecycline was used in combination with at least one anti-CR-GNB antibiotic. Clinical outcomes and all-cause mortality between patients with and without tigecycline were compared in the original and propensity score (PS)-matched cohorts. A subgroup analysis was also performed to explore the differences of clinical efficacies of add-on tigecycline treatment when combined with various anti-CR-GNB agents.

RESULTS

We analysed 395 patients with CR-GNB nosocomial pneumonia, of whom 148 received tigecycline and 247 did not. More than 80% of the enrolled patients were infected by CR-Acinetobacter baumannii (CRAB). A trend of lower all-cause mortality on day 28 was noted in tigecycline group in the original cohort (27.7% vs. 36.0%, p = 0.088). In PS-matched cohort (102 patient pairs), patients with tigecycline had significantly lower clinical failure (46.1% vs. 62.7%, p = 0.017) and mortality rates (28.4% vs. 52.9%, p < 0.001) on day 28. In multivariate analysis, tigecycline treatment was a protective factor against clinical failure (PS-matched cohort: aOR 0.52, 95% CI 0.28-0.95) and all-cause mortality (original cohort: aHR 0.69, 95% CI 0.47-0.99; PS-matched cohort: aHR 0.47, 95% CI 0.30-0.74) at 28 days. Kaplan-Meier survival analysis in subgroups of patients suggested significant clinical benefits of tigecycline when added to a colistin-included (log rank p value 0.005) and carbapenem-included (log rank p value 0.007) combination regimen.

CONCLUSIONS

In this retrospective observational study that included ICU-admitted patients with nosocomial pneumonia caused by tigecycline-susceptible CR-GNB, mostly CRAB, tigecycline as part of a combination treatment regimen was associated with lower clinical failure and all-cause mortality rates.

Efficacy of adjunctive nebulized colistin in critically ill patients with nosocomial carbapenem-resistant Gram-negative bacterial pneumonia: a multi-centre observational study

OBJECTIVES

To investigate the association between adjunctive nebulized colistin and treatment outcomes in critically ill patients with nosocomial carbapenem-resistant Gram-negative bacterial (CR-GNB) pneumonia.

METHODS

This retrospective, multi-centre, cohort study included individuals admitted to the intensive care unit with nosocomial pneumonia caused by colistin-susceptible CR-GNB. Enrolled patients were divided into groups with/without nebulized colistin as adjunct to at least one effective intravenous antibiotic. Propensity score matching was performed in the original cohort (model 1) and a time-window bias-adjusted cohort (model 2). The association between adjunctive nebulized colistin and treatment outcomes was analysed.

RESULTS

In total, 181 and 326 patients treated with and without nebulized colistin, respectively, were enrolled for analysis. The day 14 clinical failure rate and mortality rate were 41.4% (75/181) versus 46% (150/326), and 14.9% (27/181) versus 21.8% (71/326), respectively. In the propensity score-matching analysis, patients with nebulized colistin had lower day 14 clinical failure rates (model 1: 41% (68/166) versus 54.2% (90/166), p 0.016; model 2: 35.3% (41/116) versus 56.9% (66/116), p 0.001). On multivariate analysis, nebulized colistin was an independent factor associated with fewer day 14 clinical failures (model 1: adjusted odds ratio (aOR) 0.59, 95% CI 0.37-0.92; model 2: aOR 0.37, 95% CI 0.21-0.65). Nebulized colistin was not associated independently with a lower 14-day mortality rate in the time-dependent analysis in both models 1 and 2.

CONCLUSIONS

Adjunctive nebulized colistin was associated with lower day 14 clinical failure rate, but not lower 14-day mortality rate, in critically ill patients with nosocomial pneumonia caused by colistin-susceptible CR-GNB.

Forecasting models of infections due to carbapenem-resistant Gram-negative bacteria in an intensive care unit in an endemic area

OBJECTIVES

The aim of this study was to forecast the monthly incidence rates of infections [infections/1000 bed-days (IBD)] due to carbapenem-resistant Klebsiella pneumoniae (CRKP), carbapenem-resistant Pseudomonas aeruginosa (CRPA), carbapenem-resistant Acinetobacter baumannii (CRAB) and total carbapenem-resistant Gram-negative bacteria (CRGNB) in an endemic intensive care unit (ICU) during the subsequent year (December 2016-December 2017) following the observational period.

METHODS

A 52-month observational period (August 2012-November 2016) was used. Two forecasting models, including a simple seasonal model for CRGNB, CRKP and CRPA and Winters' additive model for CRAB infections, were applied.

RESULTS

The models predicted the highest infection rates for CRKP, CRAB and CRGNB in January and September 2017 (23.8/23.4, 24.6/28.5 and 46.8/46.7 IBD, respectively) and for CRPA in February and March 2017 (8.3 and 7.9, respectively). The highest observed rates for CRKP, CRAB and CRGNB were indeed in January and September 2017 (25.6/19.0, 34.2/23.8 and 59.8/42.8 IBD, respectively); and for CRPA in February and March of the same year (15.2 and 12.7, respectively). The increased rates may be associated with personnel's annual work programme and behavioural factors.

CONCLUSION

Forecasting models in endemic ICUs may assist in implementation strategies for infection control measures.

Antimicrobial treatment challenges in the era of carbapenem resistance

Infections due to carbapenem-resistant Gram-negative bacteria are burdened by high mortality and represent an urgent threat to address. Clinicians are currently at a dawn of a new era in which antibiotic resistance in Gram-negative bacilli is being dealt with by the availability of the first new antibiotics in this field for many years. Although new antibiotics have shown promising results in clinical trials, there is still uncertainty over whether their use will improve clinical outcomes in real world practice. Some observational studies have reported a survival benefit in carbapenem-resistant Enterobacteriaceae bloodstream infections using combination therapy, often including "old" antibiotics such as colistin, aminoglycosides, tigecycline, and carbapenems. These regimens, however, are linked to increased risk of antimicrobial resistance, and their efficacy has yet to be compared to new antimicrobial options. While awaiting more definitive evidence, antibiotic stewards need clear direction on how to optimize the use of old and novel antibiotic options. Furthermore, carbapenem-sparing regimens should be carefully considered as a potential tool to reduce selective antimicrobial pressure.

Revival of old antibiotics: needs, the state of evidence and expectations

The gap between the emergence of antibiotic resistance and new antibiotic development has drawn attention to old antibiotics whose spectrum of coverage frequently comprises highly resistant bacteria. However, these antibiotics have frequently not undergone the structured process of antibiotic development of modern antibiotics, from pharmacokinetic/pharmacodynamic (PK/PD) studies establishing safe and effective dosing, establishment of susceptibility breakpoints, to clinical trials establishing clinical safety and effectiveness. In this review, we highlight the gaps for which we need old antibiotics in community- and hospital-acquired infections. Reviewing recently published and ongoing randomised controlled trials (RCTs) shows advances in our understanding of the efficacy and effectiveness of oral fosfomycin, mecillinam and nitrofurantoin for cystitis, and of trimethoprim/sulfamethoxazole for complicated skin infections caused by methicillin-resistant Staphylococcus aureus (MRSA) in the community. Summarising older evidence shows the inferiority of chloramphenicol versus modern antibiotics for severe infections. We lack studies on severe infections caused by carbapenem-resistant Gram-negative bacteria and other multidrug-resistant (MDR) bacteria in hospitalised and critically ill patients; ongoing studies assessing colistin and intravenous fosfomycin might fill in some gaps. In the re-development process of old antibiotics, we mandate modern PK/PD studies comprising special populations as well as RCTs addressing the target population of patients in need of these antibiotics powered to examine patient-relevant outcomes. Structured antibiotic re-development from the laboratory to evidence-based treatment recommendations requires public funding, multidisciplinary collaboration, international co-ordination, and methods to streamline the recruitment of critically ill patients infected by MDR bacteria.

Risk factors for hospital-acquired pneumonia caused by carbapenem-resistant Gram-negative bacteria in critically ill patients: a multicenter study in Korea

We performed a case-control study to identify risk factors of carbapenem-resistant Gram-negative bacteria (CRGNB) as an increasing cause of hospital-acquired pneumonia (HAP). The study included critically ill adult patients with HAP whose microbial etiology was identified at eight tertiary centers in Korea between June 2008 and December 2009. Eighty two patients with 86 isolates of CRGNB (62 Acinetobacter baumannii, 14 Pseudomonas aeruginosa, and 10 Stenotrophomonas maltophilia) were included in the case group, and 122 patients with carbapenem-susceptible Gram-negative bacteria were included in the control group. Diabetes mellitus (adjusted odds ratio [aOR] 2.82, 95% confidence interval [95% CI] 1.25-6.38), radiologic score ≥5 (aOR 4.56, 95% CI 2.36-8.81), prior fluoroquinolone (aOR 2.39. 95% CI = 1.07-5.35), or carbapenem usage (aOR 2.82, 95% CI 1.75-17.83) were found to be independent risk factors. Fluoroquinolone and carbapenem should be cautiously used to avoid HAP caused by CRGNB.