Clinical and microbiological characteristics of peritoneal dialysis-related peritonitis caused by Klebsiella pneumoniae in southern Taiwan

Microbial Profile, Peritoneal Fluid White Blood Cell Count, and Outcome of Peritoneal Dialysis-Related Peritonitis at Indonesian Tertiary Hospital

Introduction

Peritonitis caused by peritoneal dialysis (PD) remains a common complication of continuous ambulatory PD (CAPD). The purpose of this study is to determine the microbial profile in CAPD-related peritonitis, the optimal cutoff of white blood cell (WBC) count, and the percentage of polymorphonuclear (PMN) in CAPD fluid in the prediction of CAPD-related peritonitis, together with the outcome of CAPD-related peritonitis at an Indonesian tertiary hospital. This is a retrospective cohort study of CAPD-related peritonitis patients at Indonesian tertiary hospitals from November 2020 to October 2022.

Methods

Patients with suspected CAPD-related peritonitis who were tested for CAPD fluid culture and WBC count in CAPD fluid were eligible for this study. Patient's diagnosis and outcome obtained from medical records. Differences in clinical outcomes by category of microorganisms were analyzed with Fisher exact test. The Mann-Whitney test and receiver operating characteristic curve were used to determine optimal WBC and PMN cutoff.

Results

This study included 58 patients and 102 episodes of CAPD-related peritonitis. CAPD-related peritonitis was caused by 29.4% Gram-negative bacteria, 21.5% Gram-positive bacteria, 7.8% fungi, and 6.9% polymicrobial bacteria. CAPD fluid WBC count >79 cells/μL and PMN percentage >50% had a sensitivity of 76.4% and a specificity of 92.9% in predicting CAPD-related peritonitis. There was a significant difference in outcome between Gram-negative and Gram-positive bacterial peritonitis.

Conclusions

It is critical to understand the microbial profile in CAPD-related peritonitis. Lower WBC count cutoff points in CAPD fluids may improve sensitivity in predicting CAPD-related peritonitis.

Epidemiology of extended-spectrum β-lactamases in Enterobacterales in Taiwan for over two decades

The emergence of antimicrobial resistance among microorganisms is a serious public health concern, and extended-spectrum β-lactamases (ESBL)-producing Enterobacterales is one of the major concerns among antibiotic-resistant bacteria. Although the prevalence of ESBL in Enterobacterales has been increasing with time, the prevalence of ESBL could differ according to the species, hospital allocation, sources of infections, nosocomial or community acquisitions, and geographic regions. Therefore, we conducted a comprehensive review of the epidemiology of ESBL-producing Enterobacterales in Taiwan. Overall, the rates of ESBL producers are higher in northern regions than in other parts of Taiwan. In addition, the genotypes of ESBL vary according to different Enterobacterales. SHV-type ESBLs (SHV-5 and SHV-12) were the major types of Enterobacter cloacae complex, but Serratia marcescens, Proteus mirabilis, Escherichia coli, and Klebsiella pneumoniae were more likely to possess CTX-M-type ESBLs (CTX-M-3 and CTX-M-14). Moreover, a clonal sequence type of O25b-ST131 has been emerging among urinary or bloodstream E. coli isolates in the community in Taiwan, and this clone was potentially associated with virulence, ESBL (CTX-M-15) production, ciprofloxacin resistance, and mortality. Finally, the evolution of the genetic traits of the ESBL-producing Enterobacterales isolates helps us confirm the interhospital and intrahospital clonal dissemination in several regions of Taiwan. In conclusion, continuous surveillance in the investigation of ESBL production among Enterobacterales is needed to establish its long-term epidemiology.

The Public Health Burden of Virulent Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae Strains Isolated from Diseased Horses

Background: Klebsiella pneumoniae has been associated with both nosocomial and community-acquired infections with mounting public health concern throughout the world. The purpose of this study was to investigate the burden of virulent extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae among diarrheic horses or those with respiratory illness to underscore the public health implication of such strains. Materials and Methods: Rectal and nasal swabs were gathered from 100 diseased horses (50 diarrheic and 50 with respiratory illness). The collected swabs were processed for isolation of ESBL-producing K. pneumoniae using a selective medium followed by phenotypic and molecular identification of the isolates. All ESBL-producing K. pneumoniae strains were investigated for six virulence genes (type 3 fimbrial adhesin [mrkD], enterobactin [entB], regulator of mucoid phenotype A [rmpA], Klebsiella ferric iron uptake [kfu], mucoviscosity-associated gene A [magA], and type 2 capsular polysaccharide [K2]). Results: Of the 100 examined animals, ESBL-producing K. pneumoniae was recovered from 13 (13%), with isolation rates in horses suffering from diarrhea and respiratory illness being 20% and 6%, respectively. Among the obtained isolates, bla TEM and bla SHV were found in all strains (100%) followed by bla CTX-M in 92.3%, while none of the isolates had bla OXA. In addition, 13 ESBL-producing K. pneumoniae strains exhibited a multidrug resistance (MDR) pattern. Regarding the occurrence of virulence genes among the isolates, mrkD (100%) and entB (100%) were the most predominant virulence genes followed by rmpA (76.9%) and kfu (46.2%). On the contrary, magA and K2 were negative in all ESBL-producing strains. Furthermore, this work provides four K. pneumoniae mrkD partial sequences that displayed high genetic relatedness with those obtained from human to clarify the public health burden of such isolates. Conclusion: The occurrence of virulent ESBL-producing K. pneumoniae among diseased horses highlights the potential role of this animal in the epidemiology of such virulent and antimicrobial-resistant strains, which may have great public health threat.

Infective endocarditis caused by Enterobacteriaceae: phenotypic and molecular characterization of Escherichia coli and Klebsiella pneumoniae in Rio de Janeiro, Brazil

The etiological agent for infective endocarditis (IE), a life-threatening disease, is usually gram-positive bacteria. However, gram-negative bacteria can rarely cause IE and 4% of cases are associated with morbidity and mortality. This study aimed to characterize Escherichia coli and Klebsiella pneumoniae isolates from the blood of patients with IE. The characteristics of blood isolates were compared with those of urinary isolates from patients with urinary tract infections (UTIs). The results of this study revealed that K. pneumoniae isolates from patients with IE were phylogenetically related to those from patients with UTI. Additionally, the resistance phenotype, resistance gene, virulence gene, and plasmid profiles were similar between the blood and urinary isolates. The isolates belonging to the sequence types (STs) 76, 36, 101 (K. pneumoniae), and 69 (E. coli) are reported to be associated with drug resistance. The Enterobacteriaceae isolates from patients with IE did not produce extended-spectrum β-lactamase or carbapenemase. Additionally, this study investigated the virulence phenotype, biofilm formation ability, and the ability to adhere to the epithelial cells in vitro of the isolates. The isolates from patients with IE exhibited weaker biofilm formation ability than the urinary isolates. All isolates from patients with IE could adhere to the renal epithelial cells. However, three isolates from patients with UTIs could not adhere to the epithelial cells. The closely related K. pneumoniae isolates (648, KP1, KP2, KP3, and KP4) could not form biofilms or adhere to the epithelial cells. In summary, the molecular analysis revealed that the genetic characteristics of IE-causing K. pneumoniae and E. coli were similar to those of UTI-causing isolates. These isolates belonged to the STs that are considered treatable. Genetically similar isolates did not exhibit the same virulence phenotype. Thus, these non-hypervirulent clones must be monitored as they can cause complex infections in susceptible hosts.

Peritoneal dialysis-related peritonitis caused by gram-negative organisms: ten-years experience in a single center

Objectives

Concerns are increasing about the clinical characteristics of gram- negative bacterial peritonitis for providing reference for clinical diagnosis, treatment and prevention.

Methods

A retrospective analysis was performed examining patients who developed peritoneal dialysis-related peritonitis (PDRP) from 1 January 2009 to 31 December 2018.

Results

Among 898 PD patients, 677 episodes of peritonitis occurred in 344 patients. Over 10 years, the proportion of gram-negative bacterial peritonitis increased from 0% to 26.15% (p = .045). E. coli was the leading cause (38.51%) of the 148 cases of gram-negative bacterial peritonitis. The increase of E. coli peritonitis between the first 5 and the last 5 years was obvious (20.45% vs. 46.15%). The antimicrobial sensitivity of gram-negative organisms to cefotaxime decreased from 71.43% to 55.84% (p = .017). In the gram-negative group, the effluent white cell count (WCC) on the first day was larger (OR: 1.374;95%CI: 1.248–1.563; p < .001), the time required for the WCC to normalize was longer (OR: 1.100;95%CI: 1.037–1.189; p = .003), and the level of C-reactive protein (CRP) was higher (OR: 1.038;95%CI: 1.026–1.042; p < .001) than those in the gram-positive group. The complete cure rate and treatment failure rate of gram-negative bacteria peritonitis were 87.8% and 12.2% respectively.

Conclusions

Over 10 years, the proportion of gram-negative bacterial peritonitis increased, with E. coli epidermidis being the most common pathogen. More effluent WCC on the first day, longer time required for the WCC to normalize, and higher level of CRP are more common for gram-negative bacterial peritonitis. Prognosis of gram-negative bacterial peritonitis is worse.

Continuous ambulatory peritoneal dialysis peritonitis: Microbiology and outcomes

Context

Continuous ambulatory peritoneal dialysis (CAPD) is now a preferred mode of the treatment in patients with end-stage renal disease, but peritonitis remains to be a shortcoming of CAPD. High-culture negativity, emerging drug resistance and peritoneal dialysis (PD)-related morbidity and mortality have been a challenge to tackle.

Aims

The present study was taken up to compare the the various culture methods and to identify the spectrum of organisms causing CAPD peritonitis and their outcome.

Settings and Design

A prospective, observational, cross-sectional study was conducted at a tertiary care teaching hospital in Hyderabad over a period of 1 year.

Subjects and Methods

Dialysate fluid from 100 episodes of clinically suspected peritonitis in 75 patients was processed by conventional centrifuging, water lysis, direct inoculation and addition of centrifuged pellet into brain-heart infusion broth and by automated blood culture system. Identification and antibiotic susceptibility of organisms was done, and the outcome of PD-related peritonitis was analysed.

Statistical Analysis Used

The categorical data and continuous data were analysed using the Chi-square test and Student's t-test, respectively. P < 0.05 was considered statistically significant.

Results

Of the 100 PD fluids, 87 were culture positive. Automated blood culture systems detected 87 episodes, whereas conventional centrifuge method detected only 53 episodes (P = 0.00001). Peritonitis due to Gram-negative organisms (62.3%) was higher than that of Gram-positive peritonitis (31.1%) and fungi (6.4%). Nineteen per cent episodes were constituted by relapse (9), refractory (4), recurrent (4) and repeat (2) peritonitis. Outcomes were analysed as recovery (77%), catheter removal (15%) and death (2.6%).

Conclusions

Direct inoculation of peritoneal fluid into automated blood culture bottles increases the positivity rate and also aids in the early detection of CAPD peritonitis, helping reduce morbidity and mortality of PD patients.

Nanoparticle reinforced bacterial outer-membrane vesicles effectively prevent fatal infection of carbapenem-resistant Klebsiella pneumoniae

Infection resulting from carbapenem-resistant Klebsiella pneumoniae (CRKP) is an intractable clinical problem. Outer membrane vesicles (OMVs) from CRKP are believed to be potential vaccine candidates. However, their immune response remains elusive due to low structural stability and poor size homogeneity. In this study, hollow OMVs were reinforced internally by size-controlled BSA nanoparticles to obtain uniform and stable vaccines through hydrophobic interaction. The result showed that the BSA-OMV nanoparticles (BN-OMVs) were homogenous with a size around 100 nm and exhibited a core-shell structure. Remarkably, subcutaneous BN-OMVs vaccination mediated significantly higher CRKP specific antibody titers. The survival rate of the mice infected with a lethal dose of CRKP was increased significantly after BN-OMV immunization. The adoptive transfer experiment demonstrated that the protective effect of BN-OMVs was dependent on humoral and cellular immunity. This study demonstrated that the structure optimization improved the immune efficacy of OMVs for vaccine development against CRKP.

CelB is a suitable marker for rapid and specific identification of Klebsiella pneumoniae by the loop-mediated isothermal amplification (LAMP) assay

Klebsiella pneumoniae belongs to Enterobacteriaceae, which is the commonest bacterium causing nosocomial respiratory tract infection. It ranks second in bacteremia and urinary tract infection in gram-negative bacteria. Therefore, the rapid and accurate identification of K. pneumoniae was of great significance for the guide of clinical medication, and timely treatment of patients. The purpose of this study was to establish a rapid and sensitive molecular detection method for K. pneumoniae based on loop-mediated isothermal amplification (LAMP) technology. Firstly, local BLAST and NCBI BLAST were used to analyze the genome of K. pneumoniae. According to the principle of interspecific and intraspecific specificity, CelB (GenBank ID 11847805) was selected as the specific gene. Then, the LAMP and PCR identification systems were established with this target gene. Thirty-six clinical isolates of K. pneumoniae and 50 non-K. pneumoniae were used for the specific evaluation, and both LAMP and PCR could specifically distinguish K. pneumoniae from non-K. pneumoniae. A 10-fold series diluted positive plasmids and simulated infected blood samples were used as the templates in the sensitivity assay, and the results showed that the sensitivity could reach 1 copy/reaction. In summary, a rapid, specific, and sensitive LAMP method was established to detect K. pneumoniae in clinics.

Microbiology of peritoneal dialysis-related infection and factors of refractory peritoneal dialysis related peritonitis: A ten-year single-center study in Taiwan

BACKGROUND

Peritoneal dialysis (PD)-related infection is a serious complication of patients with PD. Refractory peritonitis may lead to failure of PD, shift to hemodialysis (HD) or death. Besides, microbiologic resistance increased worldwide that might impact the treatment choice for such infections. Investigating the causative pathogens and risk factors of PD-related infections in Taiwan was warranted.

METHODS

This is a retrospective study involving patients with PD from 2007 to 2016 in a southern Taiwan hospital. Patient characteristics, microbiological data, outcomes, and factors associated with refractory peritonitis were analyzed.

RESULTS

There were 190 episodes of PD-related peritonitis in 110 patients from this cohort. Gram-positive organisms were the leading cause of PD-related peritonitis, but gram-negative organisms, esp. Pseudomonas aeruginosa, were predominant for exit site infection and tunnel infection. The incidence of peritonitis was 0.25 episode per patient-year (1 episode per 47.69 months). The refractory rate was 14.2% (27/190). Methicillin resistance was noted in 2 (13.3%) of 15 Staphylococcus aureus isolates. Of 114 isolates, 72.8% (83) were susceptible to either cefazolin or gentamicin. Staphylococcus spp. and Escherichia coli infections were significantly associated with refractory peritonitis. Baseline hyponatremia (<130 mmol/L) was independently associated with refractory peritonitis.

CONCLUSION

Gram-positive organisms remained major cause of PD-related peritonitis. About three quarters of causative pathogens were susceptible to the recommended empirical treatment for PD-related peritonitis. Baseline hyponatremia (<130 mmol/L) was independently associated with refractory peritonitis. Staphylococcus spp. and E. coli infections had important roles for refractory peritonitis.

Clinical and microbiological characteristics of peritoneal dialysis-related peritonitis caused by Escherichia coli in southern Taiwan

Peritonitis is a serious complication and major cause of treatment failure in patients undergoing peritoneal dialysis (PD). Escherichia coli is the major pathogen in extraintestinal Gram-negative infections, including PD-related peritonitis. The outcomes of E. coli peritonitis in PD varied from relatively favorable outcomes to a higher incidence of treatment failure. The aim of this study was to investigate the impact of bacterial virulence and host characteristics on the outcomes of PD-related peritonitis caused by E. coli. From January 2000 to June 2016, a total of 47 episodes of monomicrobial and 10 episodes of polymicrobial E. coli PD-related peritonitis, as well as 89 episodes of monomicrobial Gram-positive (56 Staphylococcus spp. and 33 Streptococcus spp.) PD-related peritonitis cases, were retrospectively enrolled. Clinical features, E. coli bacterial virulence, and outcomes were analyzed. Compared to Streptococcus spp. peritonitis, E. coli peritonitis had a higher peritoneal catheter removal rate (38 versus 12%; P = 0.0115). Compared to the monomicrobial group, patients in polymicrobial group were older and had higher peritoneal catheter removal rate (80 versus 38%; P = 0.0324). Treatment failure of E. coli peritonitis was associated with more polymicrobial peritonitis and immunocompromised comorbidity, longer duration of PD therapy, and more antimicrobial resistance. E. coli isolates with more iron-related genes had higher prevalence of phylogenetic group B2 and papG II, iha, ompT, and usp genes. This study demonstrates the important roles of clinical and bacterial characteristics in the outcomes of monomicrobial and polymicrobial E. coli PD-related peritonitis.

Update on fosfomycin-modified genes in Enterobacteriaceae

The long-used antibiotic fosfomycin has recently been re-evaluated as a potential regimen for treating extended-spectrum β-lactamases (ESBLs) and carbapenem-resistant Enterobacteriaceae (CRE). Fosfomycin is known for its robust bactericidal effect against ESBL-producing Enterobacteriaceae and CRE. However, fosfomycin-modified genes have been reported in transposon elements and conjugative plasmids, resulting in fosfomycin resistance in parts of East Asia. Here we review reports of fosfomycin-modified (fos) genes in Enterobacteriaceae and assess the efficacy of fosfomycin against multidrug-resistant Enterobacteriaceae infections. At least 10 kinds of fos genes have been identified in the past decade; of these, fosA (and fosA subtypes) and fosC2 are primarily found in Enterobacteriaceae. All fosA subtypes except fosA2 are found in plasmids and transposons, nearby insertion sequence elements, or integrons, indicating that mobilizing elements also play an important role in plasmid-mediated fos genes in Enterobacteriaceae. fosA3, which is prevalent in East Asia, has been transmitted (mostly by animals) within and across continents via IS26 mobile elements. The acquisition of multiple antibiotic resistance genes via plasmids and mobile elements has resulted in a need for combined treatments for Enterobacteriaceae cases. The combination of fosfomycin and carbapenem has been the focus of many in vitro studies, but there is a clear need for additional in vivo investigations involving pharmacokinetics.

The plasmid-mediated fosfomycin resistance determinants and synergy of fosfomycin and meropenem in carbapenem-resistant Klebsiella pneumoniae isolates in Taiwan

BACKGROUND

Epidemiology of fosfomycin susceptibility and the plasmid-mediated fosfomycinase genes of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates in Taiwan remain unclear.

METHODS

642 CRKP clinical isolates were collected from a nation-wide surveillance study (16 hospitals) in Taiwan in 2012-2013. Antimicrobial susceptibilities were determined. PFGE and MLST determined the clonal relatedness. Carbapenemases and fosfomycinases genes were detected by PCR, and their flanking regions were determined by PCR and sequencing. Synergistic activity of meropenem with fosfomycin was examined by the checkerboard method.

RESULTS

In total, 36.4% (234/642) of CRKP isolates in Taiwan were resistant to fosfomycin. Among 234 fosfomycin-resistant CRKP isolates, PFGE analysis revealed 81 pulsotypes. Pulsotype XXIII (n = 63) was predominant and belonged to ST11. 71 had carbapnemases (65 bla_KPC-2-positive, 1 bla_VIM-1-positive and 5 bla_IMP-8-positive) and 62 had fosfomycinases (35 fosA3-positive and 27 foskp96-positive). Only 18.5% (5/27) of foskp96-positive isolates carried foskp96 and bla_KPC-2, while 71.4% (25/35) of fosA3-positive isolates contained fosA3 and bla_KPC-2. There were five types of flanking sequences for fosA3, and 85.7% (30/35) of fosA3 genes were flanked by IS26, suggesting possible horizontal gene transfer. Synergistic effect of fosfomycin and meropenem was observed in all 25 randomly selected pulsotype XXIII strains (100%; 25/25), even those containing fosfomycinase (48%, 12/25) or carbapnemase (96%, 24/25).

CONCLUSIONS

A clone (pulsotype XXIII, ST11) has been found to be prevailing among fosfomycin-resistant CRKP in Taiwan. According to the in vitro data, the combination of fosfomycin and meropenem is a potentially alternative choice.

Vaccination with Klebsiella pneumoniae-derived extracellular vesicles protects against bacteria-induced lethality via both humoral and cellular immunity

The emergence of multidrug-resistant Klebsiella pneumoniae highlights the need to develop preventive measures to ameliorate Klebsiella infections. Bacteria-derived extracellular vesicles (EVs) are spherical nanometer-sized proteolipids enriched with outer membrane proteins. Gram-negative bacteria-derived EVs have gained interest for use as nonliving complex vaccines. In the present study, we evaluated whether K. pneumoniae-derived EVs confer protection against bacteria-induced lethality. K. pneumoniae-derived EVs isolated from in vitro bacterial culture supernatants induced innate immunity, including the upregulation of co-stimulatory molecule expression and proinflammatory mediator production. EV vaccination via the intraperitoneal route elicited EV-reactive antibodies and interferon-gamma-producing T-cell responses. Three vaccinations with the EVs prevented bacteria-induced lethality. As verified by sera and splenocytes adoptive transfer, the protective effect of EV vaccination was dependent on both humoral and cellular immunity. Taken together, these findings suggest that K. pneumoniae-derived EVs are a novel vaccine candidate against K. pneumoniae infections.