Antibiotic resistance of non-fermenting Gram-negative bacilli isolated at a large Infectious Diseases Hospital in North-Eastern Romania, during an 11-year period

A Five-Year Trend Analysis of Antibacterial Resistance Patterns Among Non-fermenting Gram-Negative Bacilli: A Retrospective Study From the ICU Settings of a Tertiary Care Hospital

INTRODUCTION

Non-fermenting gram-negative bacilli (NFGNB) infections have emerged as a serious health concern in ICUs. Multi-drug resistant (MDR) strains of NFGNB can evolve by acquiring resistance genes to at least one agent in three or more antibacterial categories. This study aimed to analyse the prevalence of NFGNB, the distribution of MDR strains, and antibiotic resistance trends of NFGNB in different ICUs of a tertiary care hospital over a period of five years.

MATERIALS AND METHODS

This retrospective study was conducted in a tertiary care teaching hospital in eastern India, including a total of 20,256 samples received from various ICUs over five years. Data retrieved from the Laboratory Information System (LIS) of the hospital, and repetitive isolates from the same patients, were excluded. All samples were processed according to standard microbiological protocols by automated systems. Data were entered into a Microsoft Excel spreadsheet (Microsoft® Corp., Redmond, WA, USA), analysed using Epi Info software, and presented using descriptive statistics. Chi-square and Fisher's exact tests (where appropriate) were used as tests of significance, with a p-value of <0.05 considered statistically significant.

RESULTS

A total of 18,032 culture-positive samples out of 20,256 samples showed growth of 18,659 bacteria. Out of these, 952 isolates were NFGNB. The prevalence of NFGNB was found to be 5.10% among all isolated bacteria. The predominant sources were respiratory samples (37.3%). Acinetobacter spp. emerged as the most prevalent NFGNB (46.5%), followed by Pseudomonas spp. (31%) and Burkholderia spp. (14.3%). Among the NFGNB isolates, 61.76% exhibited MDR, with the highest prevalence of MDR strains seen in Elizabethkingia spp. (94.7%). Among the most prevalent NFGNB, Acinetobacter spp., 64.8% were MDR strains. Trend analysis of antibiotic resistance patterns of Acinetobacter spp. indicated a substantial increase for trimethoprim-sulfamethoxazole by 18.5%, minocycline (44.4%), amikacin (20.4%), and ceftazidime (7.4%), whereas there was a reduced trend in resistance to carbapenems (6.5%), ciprofloxacin (4.7%), and cefepime (3.7%) over five years. In Pseudomonas spp., resistance to meropenem increased by 17.4%, and for ceftazidime (11.8%), amikacin (10.6%), and piperacillin-tazobactam (7.9%), whereas resistance to aztreonam diminished by 13.9%. Burkholderia spp. exhibited a 23.5% escalation in resistance to meropenem and ceftazidime (5.9%), while resistance to levofloxacin experienced a decrease of 30.2%.

CONCLUSIONS

The study showed the prevalence of various NFGNB as 5.10% in ICU settings, with Acinetobacter spp. (46.5%) being the most common isolated bacteria. Notably, 61.76% of the isolates were MDR. Antibiotic trend analysis over five years showed increasing resistance of Acinetobacter spp. to trimethoprim-sulfamethoxazole, minocycline, and ceftazidime, with improved susceptibility for carbapenems, ciprofloxacin, and cefepime. Pseudomonas spp. showed increased susceptibility to aztreonam and rising resistance for meropenem, piperacillin-tazobactam, ceftazidime, and amikacin. In Burkholderia spp., there was increased susceptibility to levofloxacin and rising resistance to meropenem and ceftazidime. These findings focus on the need for vigilant antibiotic stewardship, with the adoption of appropriate infection prevention and control practices to restrict the emergence and spread of MDR NFGNB infections in ICU settings of hospitals.

Current viewpoint on the epidemiology of nonfermenting Gram-negative bacterial strains

PURPOSE OF REVIEW

This article aims to review the epidemiology of nonfermenting Gram-negative bacilli (NFGNB) based on recent literature reports, particularly, of the less common, but with emerging clinical significance species.

RECENT FINDINGS

The reported frequency of multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa is increasing, with very significant variability, however, between different countries. Apart from the major NFGNB, that is, A. baumannii and P. aeruginosa, already recognized as of critical importance healthcare risks, several other NFGNB genera have been increasingly associated with diverse severe infections, such as Stenotrophomonas maltophilia, Burkholderia spp., Elizabethkingia spp., Chryseobacterium spp., Achromobacter spp., Alcaligenes spp., Sphingomonas spp., Shewanella spp. and Ralstonia spp., among others.

SUMMARY

The exploration of the epidemiology, as well as the pathogenic potential of the of the less frequent, but emerging and increasingly reported NFGNB, is crucial, not only for immunocompromised patients, but also for critically ill patients without overt immunosuppression. As we are heading fast towards a postantibiotic era, such information would contribute to the optimal antimicrobial management, that is, providing prompt, appropriate antimicrobial coverage when needed and, at the same time, avoiding overuse and/or inappropriate use of antimicrobial therapy. Also, it would help to better understand their transmission dynamics and to develop effective prevention strategies.

An Overview of the Impact of Bacterial Infections and the Associated Mortality Predictors in Patients with COVID-19 Admitted to a Tertiary Center from Eastern Europe

1.

BACKGROUND

Literature data on bacterial infections and their impact on the mortality rates of COVID-19 patients from Romania are scarce, while worldwide reports are contrasting. 2.

MATERIALS AND METHODS

We conducted a unicentric retrospective observational study that included 280 patients with SARS-CoV-2 infection, on whom we performed various microbiological determinations. Based on the administration or not of the antibiotic treatment, we divided the patients into two groups. First, we sought to investigate the rates and predictors of bacterial infections, the causative microbial strains, and the prescribed antibiotic treatment. Secondly, the study aimed to identify the risk factors associated with in-hospital death and evaluate the biomarkers' performance for predicting short-term mortality. 3.

RESULTS

Bacterial co-infections or secondary infections were confirmed in 23 (8.2%) patients. Acinetobacter baumannii was the pathogen responsible for most of the confirmed bacterial infections. Almost three quarters of the patients (72.8%) received empiric antibiotic therapy. Multivariate logistic regression has shown leukocytosis and intensive care unit admission as risk factors for bacterial infections and C-reactive protein, together with the length of hospital stay, as mortality predictors. The ROC curves revealed an acceptable performance for the erythrocyte sedimentation rate (AUC: 0.781), and C-reactive protein (AUC: 0.797), but a poor performance for fibrinogen (AUC: 0.664) in predicting fatal events. 4.

CONCLUSIONS

This study highlighted the somewhat paradoxical association of a low rate of confirmed infections with a high rate of empiric antibiotic therapy. A thorough assessment of the risk factors for bacterial infections, in addition to the acknowledgment of various mortality predictors, is crucial for identifying high-risk patients, thus allowing a timely therapeutic intervention, with a direct impact on improving patients' prognosis.

Temporo-spatial variations in resistance determinants and clonality of Acinetobacter baumannii and Pseudomonas aeruginosa strains from Romanian hospitals and wastewaters

Background

Romania is one of the European countries reporting very high antimicrobial resistance (AMR) rates and consumption of antimicrobials. We aimed to characterize the AMR profiles and clonality of 304 multi-drug resistant (MDR) Acinetobacter baumannii (Ab) and Pseudomonas aeruginosa (Pa) strains isolated during two consecutive years (2018 and 2019) from hospital settings, hospital collecting sewage tanks and the receiving wastewater treatment plants (WWTPs) located in the main geographical regions of Romania.

Methods

The strains were isolated on chromogenic media and identified by MALDI-TOF-MS. Antibiotic susceptibility testing and confirmation of ESBL- and CP- producing phenotypes and genotypes were performed. The genetic characterization also included horizontal gene transfer experiments, whole-genome sequencing (WGS), assembling, annotation and characterization.

Results

Both clinical and aquatic isolates exhibited high MDR rates, especially the Ab strains isolated from nosocomial infections and hospital effluents. The phenotypic resistance profiles and MDR rates have largely varied by sampling point and geographic location. The highest MDR rates in the aquatic isolates were recorded in Galați WWTP, followed by Bucharest. The Ab strains harbored mostly bla_OXA-23, bla_OXA-24, bla_SHV, bla_TEM and bla_GES, while Pa strains bla_IMP, bla_VIM, bla_NDM, bla_VEB, bla_GES and bla_TEM, with high variations depending on the geographical zone and the sampling point. The WGS analysis revealed the presence of antibiotic resistance genes (ARGs) to other antibiotic classes, such as aminoglycosides, tetracyclines, sulphonamides, fosfomycin, phenicols, trimethoprim-sulfamethoxazole as well as class 1 integrons. The molecular analyses highlighted: (i) The presence of epidemic clones such as ST2 for Ab and ST233 and ST357 for Pa; (ii) The relatedness between clinical and hospital wastewater strains and (iii) The possible dissemination of clinical Ab belonging to ST2 (also proved in the conjugation assays for bla_OXA-23 or bla_OXA-72 genes), ST79 and ST492 and of Pa strains belonging to ST357, ST640 and ST621 in the wastewaters.

Conclusion

Our study reveals the presence of CP-producing Ab and Pa in all sampling points and the clonal dissemination of clinical Ab ST2 strains in the wastewaters. The prevalent clones were correlated with the presence of class 1 integrons, suggesting that these isolates could be a significant reservoir of ARGs, being able to persist in the environment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-022-01156-1.

Drug Resistance among Major Non-fermenting Gram-negative Pathogens Isolated from Respiratory Tract Infections in a Tertiary Care Hospital of South Karnataka

Non-fermenting gram-negative bacteria (NFGNB) frequently exhibit drug resistance. The purpose of this study was to determine the drug resistance pattern among the NFGNB isolates causing respiratory tract infections (RTIs). A retrospective analysis of the antimicrobial susceptibility pattern of non-fermenters causing RTIs over four years (2016- 2019) was done and the change in drug resistance pattern was studied. A total of 653 cases were obtained that included 191 (29.2%) Moraxella catarrhalis, 283 (43.3%) Pseudomonas aeruginosa, and 132 (20.2%) Acinetobacter baumannii, 47 (7.2%) Stenotrophomonas maltophilia isolates. A higher resistance (82.6%) was observed for piperacillin-tazobactam and cefpirome, followed by imipenem (79.5%) and ciprofloxacin (76.5 %) for A. baumannii isolates. A sharp decline in resistance pattern for piperacillin, cefpirome, Imipenem and cefoperazone-sulbactam in 2019 and an increasing resistance to gentamycin and ciprofloxacin were noted. Among P. aeruginosa isolates, 94% aztreonam and 83.4% cefoperazone-sulbactam resistance were detected. There was an increased resistance for cefpirome and piperacillin and a decreased resistance for Imipenem was recorded in 2019. In cases of M. catarrhalis, 22.51% of isolates were resistant to ciprofloxacin, followed by erythromycin (18.32%) and tetracycline (17.80 %). S. maltophilia showed a 100% sensitivity for co-trimoxazole and 2.1% resistance for ciprofloxacin. A constantly changing antibiotic-resistant pattern of non-fermenters compels for a continuous update of drug-resistant trends through a longitudinal surveillance program in different geographical areas.

Antimicrobial Efficiency of Some Essential Oils in Antibiotic-Resistant Pseudomonas aeruginosa Isolates

Pseudomonas aeruginosa is a non-fermentative Gram-negative opportunistic pathogen, frequently encountered in difficult-to-treat hospital-acquired infections and also wastewaters. The natural resistance of this pathogen, together with the frequent occurrence of multidrug-resistant strains, make current antibiotic therapy inefficient in treating P. aeruginosa infections. Antibiotic therapy creates a huge pressure to select resistant strains in clinical settings but also in the environment, since high amounts of antibiotics are released in waters and soil. Essential oils (EOs) and plant-derived compounds are efficient, ecologic, and sustainable alternatives in the management of various diseases, including infections. In this study, we evaluated the antibacterial effects of four commercial essential oils, namely, tea tree, thyme, sage, and eucalyptus, on 36 P. aeruginosa strains isolated from hospital infections and wastewaters. Bacterial strains were characterized in terms of virulence and antimicrobial resistance. The results show that most strains expressed soluble pore toxin virulence factors such as lecithinase (89–100%) and lipase (72–86%). All P. aeruginosa strains were positive for alginate encoding gene and 94.44% for protease IV; most of the strains were exotoxin producers (i.e., 80.56% for the ExoS gene, 77.78% for the ExoT gene, while the ExoU gene was present in 38.98% of the strains). Phospholipase-encoding genes (plc) were identified in 91.67/86.11% of the cases (plcH/plcN genes). A high antibiotic resistance level was identified, most of the strains being resistant to cabapenems and cephalosporins. Cabapenem resistance was higher in hospital and hospital wastewater strains (55.56–100%) as compared to those in urban wastewater. The most frequently encountered encoding genes were for extended spectrum β-lactamases (ESBLs), namely, bla_CTX-M (83.33% of the strains), bla_SHV (80.56%), bla_GES (52.78%), and bla_VEB (13.89%), followed by carbapenemase-encoding genes (bla_VIM, 8.33%). Statistical comparison of the EOs’ antimicrobial results showed that thyme gave the lowest minimum inhibitory concentrations (MIC) and minimum biofilm eradication concentrations (MBEC) in P. aeruginosa-resistant isolates, making this EO a competitive candidate for the development of efficient and ecologic antimicrobial alternatives.