In Vitro Susceptibility of Multi-Drug Resistant Klebsiellapneumoniae Strains Causing Nosocomial Infections to Fosfomycin. A Comparison of Determination Methods

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

Evaluation of the in vitro susceptibility of clinical isolates of NDM-producing Klebsiella pneumoniae to new antibiotics included in a treatment regimen for infections

Background

Due to the growing resistance to routinely used antibiotics, the search for new antibiotics or their combinations with effective inhibitors against multidrug-resistant microorganisms is ongoing. In our study, we assessed the in vitro drug susceptibility of Klebsiella pneumoniae strains producing New Delhi metallo-β-lactamases (NDM) to antibiotics included in the Infectious Diseases Society of America (IDSA) and European Society of Clinical Microbiology and Infectious Diseases (ESCMID) recommendations.

Methods

A total of 60 strains of NDM-producing K. pneumoniae were obtained from different patients hospitalized at the 4th Military Hospital in Wroclaw between 2019 and 2022 and subjected to drug susceptibility to selected antibiotics, including the effects of drug combinations.

Results

Among the tested antibiotics, the highest sensitivity (100%) was observed for cefiderocol, eravacycline (interpreted according to the European Committee on Antimicrobial Susceptibility Testing [EUCAST]), and tigecycline. Sensitivity to intravenous fosfomycin varied depending on the method used. Using the "strip stacking" method, determining cumulative sensitivity to ceftazidime/avibactam and aztreonam demonstrated 100% in vitro sensitivity to this combination among the tested strains.

Conclusion

The in vitro susceptibility assessment demonstrated that, the best therapeutic option for treating infections caused by carbapenemase-producing strains seems to be a combination of ceftazidime/avibactam with aztreonam. Due to the safety of using both drugs, cost effectiveness, and the broadest indications for use among the tested antibiotics, this therapy should be the first-line treatment for carbapenemase-producing Enterobacterales infections. Nevertheless, a comprehensive evaluation of the efficacy of treating infections caused by NDM-producing K. pneumoniae strains should include not only in vitro susceptibility assessment but also an analysis of clinical cases.

Clinical Features and Outcomes of VAP Due to Multidrug-Resistant Klebsiella spp.: A Retrospective Study Comparing Monobacterial and Polybacterial Episodes

VAP due to multidrug-resistant (MDR) bacteria is a frequent infection among patients in ICUs. Patient characteristics and mortality in mono- and polybacterial cases of VAP may differ. A single-centre, retrospective 3-year study was conducted in the four ICUs of a Lithuanian referral university hospital, aiming to compare both the clinical features and the 60-day ICU all-cause mortality of monobacterial and polybacterial MDR Klebsiella spp. VAP episodes. Of the 86 MDR Klebsiella spp. VAP episodes analyzed, 50 (58.1%) were polybacterial. The 60-day mortality was higher (p < 0.05) in polybacterial episodes: overall (50.0 vs. 27.8%), in the sub-group with less-severe disease (SOFA < 8) at VAP onset (45.5 vs. 15.0%), even with appropriate treatment (41.7 vs. 12.5%), and the sub-group of extended drug-resistant (XDR) Klebsiella spp. (46.4 vs. 17.6%). The ICU mortality (44.0 vs. 22.5%) was also higher in the polybacterial episodes. The monobacterial MDR Klebsiella spp. VAP was associated (p < 0.05) with prior hospitalization (61.1 vs. 40.0%), diabetes mellitus (30.6 vs. 5.8%), obesity (30.6 vs. 4.7%), prior antibiotic therapy (77.8 vs. 52.0%), prior treatment with cephalosporins (66.7 vs. 36.0%), and SOFA cardiovascular ≥ 3 (44.4 vs. 10.0%) at VAP onset. Patients with polybacterial VAP were more likely (p < 0.05) to be comatose (22.2 vs. 52.0%) and had a higher SAPS II score (median [IQR] 45.0 [35.25-51.1] vs. 50.0 [40.5-60.75]) at VAP onset. Polybacterial MDR Klebsiella spp. VAP had distinct demographic and clinical characteristics compared to monobacterial, and was associated with poorer outcomes.

Evolution of Antibiotic Resistance in Escherichia coli and Klebsiella pneumoniae Clinical Isolates in a Multi-Profile Hospital over 5 Years (2017-2021)

In recent years, we have witnessed a growing drug resistance among bacteria, which is associated with the use and availability of an increasing number of broad-spectrum antimicrobial agents, as well as with their irrational and excessive use. The present study aims to analyze changes in the drug resistance of Gram-negative Enterobacterales: Escherichia coli and Klebsiella pneumoniae, isolated from infections in a multi-profile hospital over five years (from 2017 to 2021). Among the practical outcomes of the evaluation of these data will be the possibility of determining changes in susceptibility to the antibiotics used in the hospital. In turn, this will help propose new therapeutic options, especially for empirical therapy that is necessary in severe infections. The analysis of the use of individual groups of antibiotics allowed for identification of the causes of the increasing resistance of Gram-negative bacilli. The highest number of infections whose etiological agent was K. pneumoniae ESBL(+) and E. coli ESBL(+) was observed in 2018. In the analyzed five-year period, the number of multi-resistant (MDR) K. pneumoniae strains increased successively, which seems to be related to the growing use, especially in the pandemic period, of broad-spectrum antibiotics, mainly penicillins with inhibitors, third-generation cephalosporins, and carbapenems.

Assessment of the Susceptibility of Clinical Gram-Negative and Gram-Positive Bacterial Strains to Fosfomycin and Significance of This Antibiotic in Infection Treatment

Multidrug resistance of bacteria has prompted intensive development work on new medicines, but also the search for effective options among the oldest antibiotics. Although intravenous fosfomycin (IVFOS) seems to be an interesting proposal, the recommended agar dilution method for susceptibility determination poses a major problem in routine diagnostic testing. As a consequence, there is a lack of comprehensive data on the frequency of isolation of susceptible or resistant strains. This fact triggered the disposition of EUCAST concerning the revision of IVFOS breakpoints (BPs), including withdrawal of BPs for Enterobacterales (excluding E. coli) and coagulase-negative staphylococci. Therefore, the aim of this study was to assess the activity of fosfomycin against numerous clinical strains using recommended methods. Materials and methods: A total of 997 bacterial strains were tested from the following genera: Enterobacterales, Pseudomonas spp., Staphylococcus spp., Acinetobacter spp., and Enterococcus spp., for which there are currently no BPs. The strains were isolated from various clinical materials from patients hospitalized in five hospitals. During the investigation, the recommended agar dilution method was used. Susceptibility to other antibiotics and resistance mechanisms were determined using an automatic method (Phoenix) the disk diffusion method, and E-tests. MIC values of fosfomycin were estimated for all strains and for susceptible and multidrug-resistant (MDR) strains individually. Results: Except for Acinetobacter and Enterococcus, 83% of the strains were susceptible to IVFOS, including the largest percentage of S. aureus and E. coli. Klebsiella spp. turned out to be the least susceptible strains (66%). The highest proportion of susceptibility to fosfomycin was found among strains that were sensitive to other antibiotics (80.9%), and the lowest was found among Gram-negative carbapenemase-producing bacteria (55.6%) and ESBL+ bacteria (61.6%). The MIC evaluation revealed the lowest MIC₅₀ and MIC₉₀ values for S. aureus (0.5 mg/L and 1 mg/L, respectively) and E. coli (4 mg/L and 32 mg/L, respectively). The highest values of MIC₅₀ were found for Acinetobacter spp. (256 mg/L), while the highest values of MIC₉₀ were found for Acinetobacter spp. and Klebsiella spp. (256 mg/L and 512 mg/L, respectively). Conclusions: IVFOS appears to be suitable for the treatment of many infections, including the empirical treatment of polymicrobial infections and those caused by MDR strains, since the sensitivity of the studied strains to this antibiotic in different groups ranged from 66% to as much as 99%. Sensitivity to fosfomycin was also demonstrated by 60% of carbapenem-resistant strains; therefore, IVFOS is one of the few therapeutic options that can be effective against the most resistant Gram-negative rods. In light of the general consultation posted by EUCAST, obtaining data such as IVFOS MIC value distributions may be vital for the decision of implementing fosfomycin into breakpoint tables.

Design, synthesis, antibacterial activity evaluation and molecular docking study of pleuromutilin derivatives bearing amide side chains

A seize of pleuromutilin derivatives containing amide side chains were designed and synthesized as potential antibiotics against Methicillin-resistant Staphylococcus aureus (MRSA). Among all target compounds (compounds 11-30), compound 25 was found to have the strongest antibacterial activity against MRSA (minimum inhibitory concentration = 0.5 μg/ml). The result of the time-kill curves indicated that compound 25 could repress the growth of MRSA in vitro obviously (-3.72 log10 CFU/ml reduction). Furthermore, molecular docking studies demonstrated that compound 25 was localized in the binding pocket of 50S ribosomal subunit (ΔGb = -8.99 kcal/mol). Besides, compound 25 displayed low cytotoxicity to RAW 264.7 cells. The results suggested that compound 25 might be further developed into a novel antimicrobial agent against MRSA.

Occurrence and Characteristics of Carbapenem-Resistant Klebsiella pneumoniae Strains Isolated from Hospitalized Patients in Poland-A Single Centre Study

The global emergence and spread of genes responsible for the production of ESBL (extended-spectrum beta-lactamases) and carbapenemases in Klebsiella pneumoniae isolates poses a serious threat to public health. The aim of this study was to retrospectively analyze the frequency of occurrence and drug resistance of selected alarm agents isolated from patients of the specialist hospital in Wrocław. A total of 13,528 clinical materials collected from patients of a specialist hospital in Wrocław were analyzed in the period from 1 January 2020 to 31 December 2020. Overall, 3894 bacterial strains were isolated from clinical materials, including 416 K. pneumoniae isolates. K. pneumoniae that showed resistance to ETP (ertapenem) and/or MEM (meropenem) were tested using phenotypic tests for the detection of KPC (carbapenemase-producing Klebsiella), MBL (metallo-β-lactamase) and OXA-48 (oxacilinase-48) carbapenemases. In the case of a positive or doubtful result of the phenotypic test, immunochromatographic tests and the CarbaNP test were performed. In total, 58 K. pneumoniae isolates resistant to 1 or more carbapenem antibiotics were isolated. Of the 58 strains, 16 (27.6%) were isolated from rectal swabs conducted on CPE (carbapenemase-producing Enterobacteriaceae) carriers. In the case of CRE (carbapenem-resistant Enterobacteriaceae) K. pneumoniae, carbapenemases were detected in 28/58 (48.3%) isolates. Notably, 23/28 K. pneumoniae isolates produced MBL/NDM (New Delhi metallo-β-lactamase) (82.1%), 5/28 produced VIM (Verona-intergon-encoded metallo-β-lactamase) (14.3%), and one produced MBL/NDM + OXA-48. Carbapenemases were detected in 13 of 16 (81.3%) carbapenem-resistant K. pneumoniae isolates derived from rectal swabs. The significant participation of CRE and CPE isolates in the infections proves the need to test patients admitted to hospital wards for their status as a CPE carrier in order to limit the emergence of new epidemic outbreaks.

Clonal Dissemination of Clinical Carbapenem-Resistant Klebsiella pneumoniae Isolates Carrying fosA3 and bla KPC-2 Coharboring Plasmids in Shandong, China

Treatment strategies of infection by carbapenem-resistant Klebsiella pneumoniae (CRKP) are limited. Fosfomycin, a broad-spectrum antibiotic, has attracted renewed interest in combination therapy to fight K. pneumoniae infections. However, reports on fosfomycin-resistant K. pneumoniae are increasing. Among the 57 CRKP strains, 40 (70.2%) were resistant to fosfomycin. Thus, whole-genome sequencing and bioinformatics analysis were conducted to reveal molecular characteristics of fosfomycin-resistant K. pneumoniae. Twenty-three isolates coharbored fosA^kp and fosA3, with K. pneumoniae carbapenemase (KPC)-producing ST11-KL64-wzi64-O2 (n = 13) and ST11-KL47-wzi209-OL101 (n = 8), the predominating clonal groups, while fosA3 was not detected in isolates carrying class B carbapenemase genes. Twenty-two (out of 26) ST11-KL64 strains were positive for rmpA2, of which 12 carried fosA3. Four of the 23 fosA3-positive isolates could successfully transfer their fosfomycin-resistant determinants to Escherichia coli J53Azi^R. All four strains belonged to ST11-KL47 with the same pulsed-field gel electrophoresis profile, and their transconjugants acquired fosfomycin, carbapenem, and aminoglycoside resistance. A 127-kb conjugative pCT-KPC-like hybrid plasmid (pJNKPN52_KPC_fosA) coharboring fosA3, bla_KPC–2, bla_CTX–M–65, bla_SHV–12, rmtB, and bla_TEM–1 was identified. ST11-KL64 and ST11-KL47 K. pneumoniae, with higher resistance and virulence, should be critically monitored to prevent the future dissemination of resistance.

The In Vitro Ability of Klebsiella pneumoniae to Form Biofilm and the Potential of Various Compounds to Eradicate It from Urinary Catheters

Urinary infections related to the presence of bacterial biofilm on catheters are responsible for loss of patients’ health and, due to their high frequency of occurrence, generate a significant economic burden for hospitals. Klebsiella pneumoniae is a pathogen frequently isolated from this type of infection. In this study, using a cohesive set of techniques performed under stationary and flow conditions, we assessed the ability of 120 K. pneumoniae strains to form biofilm on various surfaces, including catheters, and evaluated the usefulness of clinically applied and experimental compounds to remove biofilm. The results of our study indicate the high impact of intraspecies variability with respect to K. pneumoniae biofilm formation and its susceptibility to antimicrobials and revealed the crucial role of mechanical flushing out of the biofilm from the catheter’s surface with use of locally active antimicrobials. Therefore, our work, although of in vitro character, may be considered an important step in the direction of efficient reduction of K. pneumoniae biofilm-related hospital infections associated with the presence of urine catheters.

Global Prevalence of Nosocomial Multidrug-Resistant Klebsiella pneumoniae: A Systematic Review and Meta-Analysis

The emergence of nosocomial multidrug-resistant Klebsiella pneumoniae is an escalating public health threat worldwide. The prevalence of nosocomial infections due to K. pneumoniae was recorded up to 10%. In this systematic review and meta-analysis, which were conducted according to the guidelines of Preferred Reporting Items for Systematic Review and Meta-Analysis, 1092 articles were screened from four databases of which 47 studies fulfilled the selected criteria. By performing a random-effect model, the pooled prevalence of nosocomial multidrug-resistant K. pneumoniae was estimated at 32.8% (95% CI, 23.6-43.6), with high heterogeneity (I2 98.29%, p-value < 0.001). The estimated prevalence of this pathogen and a few related studies were discussed, raising awareness of the spread of multidrug-resistant K. pneumoniae in the healthcare setting. The emergence of nosocomial multidrug-resistant K. pneumoniae is expected to increase globally in the future, and the best treatments for treating and preventing this pathogen should be acknowledged by healthcare staff.

Antibiotic Resistance Genes Among Carbapenem-resistant Enterobacterales (CRE) Isolates of Prapokklao Hospital, Chanthaburi Province, Thailand

Background

The global spread of carbapenem-resistant Enterobacterales (CRE) inflicts a severe threat to human health. The CRE infections have resulted in an increased mortality rate in hospitals and other health-care settings worldwide. In this study, the antibiotic-resistance pattern and prevalence of carbapenemase-encoding genes among CRE isolated from patients of one hospital in Thailand were investigated.

Methods

By using conventional biochemical tests, we identified and isolated all species of Enterobacterales from the clinical samples kept at Prapokklao Hospital, Chanthaburi, Thailand, which were collected during 2016–2017. Multidrug-resistant (MDR) bacteria were determined by disc diffusion method and minimum inhibitory concentration (MIC) test strips. Carbapenemase genes were detected by PCR and confirmed by Sanger sequencing.

Results

Klebsiella pneumoniae complex, Escherichia coli, and Enterobacter spp. were isolated from the specimens. Of 9,564 isolated Enterobacterales, 282 were multidrug-resistance (MDR). The MIC test strips revealed that the MDR CRE were resistant to ertapenem (92.9%) and meropenem (81.3%). All these isolates carried carbapenemase-coding genes, including bla_NDM (90%) and bla_IMP (71%), the two most commonly found genes among CRE strains. There were 39.2% of the isolates that carried a combination of bla_NDM-bla_IMP and 22.6% carried combined bla_NDM-bla_IMP-bla_OXA-48-like genes.

Conclusion

This study demonstrates a significantly high prevalence of CRE isolates with the MDR phenotypes. A minority of the isolates carried a single carbapenem-resistant gene, while the majority harbored multiple genes in combination. Regular monitoring of MDR CRE and characterization of their drug resistance are important for guiding treatment, intervention and control of the CRE spread and outbreak in a health-care setting.