Emerging invasive liver abscess caused by K1 serotype Klebsiella pneumoniae in Korea

Pyogenic liver abscess in pediatric populations in beijing (2008-2023)

BACKGROUND

Data on pyogenic liver abscess (PLA) of children in China have been limited. We aimed to summarize the clinical feather, microbiological characteristics, management, and outcome of PLA in children.

METHOD

We retrospectively reviewed PLA cases from January 2008 to June 2023 at Beijing Children's Hospital. Clinical characteristics, pathogens and management were analyzed.

RESULTS

We diagnosed 57 PLA patients in our center. The median onset age was 4.5 years and the male-to-female ratio was 1.6:1. The median diagnostic time was nine days and the median length of stay was 22 days. Twenty-eight patients (49.1%) had predisposing factors, around 71.4% of the patients had malignant hematology and primary immunodeficiency disease. Patients with underlying factors were more likely to have extrahepatic organ involvement (p = 0.024), anemia (p < 0.001), single abscess (p = 0.042), unilateral involvement (p = 0.039), and small size of the abscess (p = 0.008). Twenty-four patients (42.1%) had extrahepatic organ involvement. Pathogens were identified in 17 patients (29.8%), the most common pathogens were Klebsiella pneumoniae and Staphylococcus aureus. The positive rate of metagenomic next-generation sequencing (mNGS) was 87.5% (7/8). On multivariable analysis, the extrahepatic organ involved (p = 0.029) and hepatomegaly (p = 0.025) were two independent factors associated with poor outcomes.

CONCLUSIONS

PLA is usually seen in children with predisposing factors. Malignant hematology and primary immunodeficiency disease were the most common underlying diseases. Extrahepatic organ involvement and hepatomegaly are associated with poor prognosis. Increased use of mNGS could be beneficial for identifying pathogens.

Liver Fibrosis Scores as Predictors of Blood-Culture-Positive and Sepsis in Patients with Klebsiella pneumoniae Liver Abscess

Objective

Klebsiella pneumoniae liver abscess (KPLA) is an invasive infectious disease with a considerable prevalence and complications. This study aimed to determine the predicted value of aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 index (FIB-4) for positive blood cultures and sepsis in patients with KPLA.

Methods

We evaluated 248 consecutive participants diagnosed with KPLA. Demographic characteristics, clinical features, and laboratory test results of the participants were recorded. Multivariate logistic regression analysis was performed to identify the risk factors. Receiver operating characteristic (ROC) analyses were conducted to evaluate the discriminatory ability of APRI and FIB-4.

Results

30.2% (75 of 248) KPLA patients presented with positive blood cultures, and 70 (28.2%) developed sepsis. Among the positive blood culture and sepsis groups, the APRI and FIB-4 showed statistically significant increases. Multivariate analysis showed that APRI (odds ratio [OR] = 1.190, 95% confidence interval [CI] 1.051-1.347, p = 0.006) and FIB-4 (OR = 1.110, 95% CI 1.046-1.179, p = 0.001) were independent prognostic factors for positive blood cultures. Both APRI (OR = 1.505, 95% CI 1.149-1.988, p = 0.004) and FIB-4 (OR = 1.187, 95% CI 1.054-1.336, p = 0.005) were independent risk factors for sepsis. The area under the ROC curve (AUC) of APRI and FIB-4 for predicting positive blood cultures of KPLA was 0.783 and 0.766, respectively. APRI had an AUC of 0.801, with a sensitivity and specificity of 71.4% and 81.5%, respectively, for predicting sepsis in patients with KPLA, and the prediction performance of APRI was better than that of FIB-4 (AUC = 0.798).

Conclusion

In our study, APRI and FIB-4 are effective methods for predicting KPLA patients with positive blood cultures and sepsis.

Macrophage-depleted young mice are beneficial in vivo models to assess the translocation of Klebsiella pneumonia from the gastrointestinal tract to the liver in the elderly

Pathobionts are commensal intestinal microbiota capable of causing systemic infections under specific conditions, such as environmental changes or aging. However, it is unclear how pathobionts are recognized by the intestinal mucosal immune system under physiological conditions. This study demonstrates that the gut pathobiont Klebsiella pneumoniae causes injury to the epithelium and translocates to the liver in specific pathogen-free mice treated with clodronate-liposomes that depleted macrophages. In the clodronate-liposome-treated mice, indigenous classical K. pneumoniae (cKp) with non-K1/K2 capsular serotypes were isolated from the liver, indicating that gut commensal cKp translocated from the gastrointestinal tract to the liver due to the depletion of intestinal macrophages. Oral inoculation of isolated cKp to clodronate-liposome-treated mice significantly reduced the survival rates compared to that of non-treated mice. Our findings demonstrate that intestinal mucosal macrophages play a pivotal role in sensing commensal cKp and suppressing their translocation to the liver. This study demonstrates that clodronate-liposome-treated mouse models are effective for screening and evaluating drugs that prevent the translocation of cKp to the liver, providing new insights into the development of preventive protocols against K. pneumoniae infection.

Virulence Factors and Carbapenem-Resistance Mechanisms in Hypervirulent Klebsiella Pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP) has emerged as a novel variant of K. pneumoniae, exhibiting distinct phenotypic and genotypic characteristics that confer increased virulence and pathogenicity. It is not only responsible for nosocomial infections but also community-acquired infections, including liver abscesses, endophthalmitis, and meningitis, leading to significant morbidity and mortality. HvKP has been reported all over the world, but it is mainly prevalent in Asia Pacific, especially China. Moreover, hvKP can acquire carbapenemase genes resulting in the emergence of carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP), which possesses both high virulence and drug resistance capabilities. Consequently, CR-hvKP poses substantial challenges to infection control and presents serious threats to global public health. In this paper, we provide a comprehensive summary of the epidemiological characteristics, virulence factors, and mechanisms underlying carbapenem resistance in hvKP strains with the aim of offering valuable insights for practical prevention strategies as well as future research.

A novel phage putative depolymerase, Depo16, has specific activity against K1 capsular-type Klebsiella pneumoniae

Klebsiella pneumoniae, especially hypervirulent K. pneumoniae (hvKP), is a common opportunistic pathogen that often causes hospital- and community-acquired infections. Capsular polysaccharide (CPS) is an important virulence factor of K. pneumoniae. Some phages encode depolymerases that can recognize and degrade bacterial polysaccharides. In this study, the lytic bacteriophage vB_KpnP_ZK1 (abbreviated as ZK1) was isolated using serotype K1 hvKP as the host. Although amino acid sequence BLAST analysis indicated that the tail fiber protein Depo16 of phage ZK1 showed no significant similarity to any reported phage depolymerases, it displayed enzymatic activities that are characteristic of phage depolymerases. After expression and purification, Depo16 could efficiently remove the capsular polysaccharide layer that surrounds the surface of serotype K1 K. pneumoniae. Although no bactericidal activity was detected, Depo16 makes serotype K1 K. pneumoniae sensitive to peritoneal macrophages (PMs). In addition, in a mouse bacteremia model of serotype K1 K. pneumoniae, 25 µg of Depo16 was effective in significantly prolonging survival. Depo16 treatment can reduce the bacterial load in blood and major tissues and alleviate tissue damage in mice. This indicates that the putative depolymerase Depo16 is a potential antibacterial agent against serotype K1 K. pneumoniae infections.IMPORTANCEKlebsiella pneumoniae often causes hospital-acquired infections and community-acquired infections. Capsular polysaccharide (CPS) is one of the crucial virulence factors of K. pneumoniae. K1 and K2 capsular-type K. pneumoniae strains are the most prevalent serotypes of hypervirulent K. pneumoniae (hvKP). In this study, a novel K. pneumoniae phage named vB_KpnP_ZK1 was isolated, and its putative depolymerase Depo16 showed low homology with other reported phage depolymerases. Depo16 can specifically degrade the K. pneumoniae K1 capsule making this serotype sensitive to peritoneal macrophages. More importantly, Depo16 showed a significant therapeutic effect in a mouse bacteremia model caused by serotype K1 K. pneumoniae. Thus, Depo16 is a potential antibacterial agent to combat serotype K1 K. pneumoniae infections.

The Rapid Emergence of Hypervirulent Klebsiella Species and Burkholderia pseudomallei as Major Health Threats in Southeast Asia: The Urgent Need for Recognition as Neglected Tropical Diseases

The World Health Organization (WHO)'s list of neglected tropical diseases (NTDs) highlights conditions that are responsible for devastating health, social and economic consequences, and yet, they are overlooked and poorly resourced. The NTD list does not include conditions caused by Gram-negative bacilli (GNB). Infections due to GNB cause significant morbidity and mortality and are prevalent worldwide. Southeast Asia is a WHO region of low- and middle-income countries carrying the largest burden of NTDs. Two significant health threats in Southeast Asia are Burkholderia pseudomallei (causing melioidosis) and hypervirulent Klebsiella pneumoniae (HvKp). Both diseases have high mortality and increasing prevalence, yet both suffer from a lack of awareness, significant under-resourcing, incomplete epidemiological data, limited diagnostics, and a lack of evidence-based treatment. Emerging evidence shows that both melioidosis and HvKp are spreading globally, including in high-income countries, highlighting the potential future global threat they pose. In this article, we review both conditions, identifying current trends and challenges in Southeast Asia and areas for future research. We also argue that melioidosis and HvKp merit inclusion as NTDs, and that mandatory global surveillance and reporting systems should be established, and we make an urgent call for research to better understand, detect, and treat these neglected diseases.

Thrombocytopenia in Klebsiella pneumoniae liver abscess: a retrospective study on its correlation with disease severity and potential causes

Objective

Thrombocytopenia is commonly associated with infectious diseases and serves as an indicator of disease severity. However, reports on its manifestation in conjunction with Klebsiella pneumoniae liver abscess (KPLA) are scarce. The present study sought to elucidate the correlation between thrombocytopenia and KPLA severity and delve into the etiological factors contributing to the incidence of thrombocytopenia.

Materials and methods

A retrospective analysis of the clinical data from patients with KPLA admitted between June 2012 and June 2023 was performed. Baseline characteristics, biochemical assessments, therapeutic interventions, complications, and clinical outcomes were compared between patients with and without thrombocytopenia. To investigate the potential etiologies underlying thrombocytopenia, the association between platelet count reduction and thrombophlebitis was examined, with a particular focus on platelet consumption. Furthermore, bone marrow aspiration results were evaluated to assess platelet production anomalies.

Results

A total of 361 KPLA patients were included in the study, among whom 60 (17%) had concurrent thrombocytopenia. Those in the thrombocytopenia group exhibited significantly higher rates of thrombophlebitis (p = 0.042), extrahepatic metastatic infection (p = 0.01), septic shock (p = 0.024), admissions to the intensive care unit (p = 0.002), and in-hospital mortality (p = 0.045). Multivariate analysis revealed that thrombocytopenia (odds ratio, 2.125; 95% confidence interval, 1.114-4.056; p = 0.022) was independently associated with thrombophlebitis. Among the thrombocytopenic patients, eight underwent bone marrow aspiration, and six (75%) had impaired medullar platelet production. After treatment, 88.6% of thrombocytopenic patients (n = 47) demonstrated recovery in their platelet counts with a median recovery time of five days (interquartile range, 3-6 days).

Conclusions

Thrombocytopenia in patients with KPLA is indicative of increased disease severity. The underlying etiologies for thrombocytopenia may include impaired platelet production within the bone marrow and augmented peripheral platelet consumption as evidenced by the presence of thrombophlebitis.

General Overview of Klebsiella pneumonia: Epidemiology and the Role of Siderophores in Its Pathogenicity

The opportunistic pathogen Klebsiella pneumoniae (K. pneumoniae) can colonize mucosal surfaces and spread from mucosae to other tissues, causing fatal infections. Medical equipment and the healthcare setting can become colonized by Klebsiella species, which are widely distributed in nature and can be found in water, soil, and animals. Moreover, a substantial number of community-acquired illnesses are also caused by this organism worldwide. These infections are characterized by a high rate of morbidity and mortality as well as the capacity to spread metastatically. Hypervirulent Klebsiella strains are thought to be connected to these infections. Four components are critical to this bacterium's pathogenicity-the capsule, lipopolysaccharide, fimbriae, and siderophores. Siderophores are secondary metabolites that allow iron to sequester from the surrounding medium and transport it to the intracellular compartment of the bacteria. A number of variables may lead to K. pneumoniae colonization in a specific area. Risk factors for infection include local healthcare practices, antibiotic use and misuse, infection control procedures, nutrition, gender, and age.

Genotypic characterization of hypervirulent Klebsiella pneumoniae (hvKp) in a tertiary care Indian hospital

Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging pathogen and causes endophthalmitis, liver abscess, osteomyelitis, meningitis, and necrotizing soft tissue infections in both immunodeficient and healthy people. The acquisition of the antibiotic resistance genes of hvKp has become an emerging concern throughout the globe. In this study, a total of 74 K. pneumoniae isolates were collected and identified by VITEK2 and blaSHV gene amplification. Out of these, 18.91% (14/74) isolates were identified as hvKp by both phenotypic string test and genotypic iucA PCR amplification. The antibiotic susceptibility revealed that 57.14% (8/14) isolates were multidrug-resistant (MDR) and 35.71% (5/14) isolates were extremely drug-resistant (XDR). All the isolates were resistant to β-lactam, β-lactamase + inhibitor groups of antibiotics, and the least resistance to colistin. Of 14 hvKp isolates, all isolates are positive for iroB (100%), followed by iutA (92.85%), peg344 (85.71%), rmpA (57.14%), and magA (21.42%) genes. Among serotypes, K1 was the most prevalent serotype 21.4% (3/14), followed by K5 14.3% (2/14). The most common carbapenemase gene was blaOXA-48 (78.57%) followed by blaNDM (14.28%) and blaKPC (14.28%) which co-carried multiple resistance genes such as blaSHV (100%), blaCTX-M (92.85%), and blaTEM (78.57%). About 92.85% (13/14) of hvKp isolates were strong biofilm producers, while one isolate (hvKp 10) was the only moderate biofilm producer. The (GTG)5-PCR molecular typing method revealed high diversity among the hvKp isolates in the tertiary care hospital. Our findings suggest that MDR-hvKp is an emerging pathogen and a challenge for clinical practice. In order to avoid hvKp strain outbreaks in hospital settings, robust infection control and effective surveillance should be implemented.

Modified Impedance Sensing System Determination of Virulence Characteristics of Pathogenic Bacteria Klebsiella Species

An impedance sensing system is a family of biosensors that measure changes in electrical impedance to perform their functions. Physical and chemical changes in the impedance of the sensing element, such as changes in the concentration of a target analyte or changes in the physical properties of the sensing element, can result in changes in the impedance of the sensing element. Many impedance biosensors have been developed for the detection of pathogens in the past few decades. Several types of biosensors have been developed for the detection of infections, including transduction elements, biorecognition components, and electrochemical approaches. In this review, we discuss the characteristics and pathogenic factors associated with 2,3-butanediol-producing Klebsiella pneumoniae collected using impedance sensors. An impedance sensing system was introduced as a great method for monitoring the virulence factors of Klebsiella spp. in situ. Klebsiella pneumoniae produces virulence factors, including capsules, lipopolysaccharides, fimbriae, and siderophores, as part of its pathogenesis. It is possible to examine virulence factors' pathogenic characteristics in vitro and in vivo using real tissues or mouse models in order to conduct experiments. For the monitoring of virulence factors in situ, a novel alternative method has been developed to mimic the environment of real tissues. For the purpose of developing tissue-mimicking models, mucin and mannose were used to modify the surface of gold electrodes. These components are known to contribute to the adhesion of pathogens to epithelial cells in mammals.

Genomic epidemiology and heterogeneity of Providencia and their blaNDM-1-carrying plasmids

Providencia as an opportunistic pathogen can cause serious infection, and moreover the emergence of multi-drug-resistant Providencia strains poses a potentially life-threatening risk to public health. However, a comprehensive genomic study to reveal the population structure and dissemination of Providencia is still lacking. In this study, we conducted a genomic epidemiology analysis on the 580 global sequenced Providencia isolates, including 257 ones sequenced in this study (42 ones were fully sequenced). We established a genome sequence-based species classification scheme for Providencia, redefining the conventional 11 Providencia species into seven genocomplexes that were further divided into 18 genospecies, providing an extensively updated reference for Providencia species discrimination based on the largest Providencia genome dataset to date. We then dissected the profile of antimicrobial resistance genes and the prevalence of multi-drug-resistant Providencia strains among these genocomplexes/genospecies, disclosing the presence of diverse and abundant antimicrobial resistance genes and high resistance ratios against multiple classes of drugs in Providencia. We further dissected the genetic basis for the spread of blaNDM-1 in Providencia. blaNDM-1 genes were mainly carried by five incompatible (Inc) groups of plasmids: IncC, IncW, IncpPROV114-NR, IncpCHS4.1-3, and IncpPrY2001, and the last three were newly designated in this study. By tracking the spread of blaNDM-1-carrying plasmids, IncC, IncpPROV114-NR, IncpCHS4.1-3, and IncpPrY2001 plasmids were found to be highly involved in parallel horizontal transfer or vertical clonal expansion of blaNDM-1 among Providencia. Overall, our study provided a comprehensive genomic view of species differentiation, antimicrobial resistance prevalence, and plasmid-mediated blaNDM-1 dissemination in Providencia.

Endogenous Endophthalmitis From a Klebsiella pneumoniae Liver Abscess: The Incidence, Risk Factors, and Utility of Imaging

PURPOSE

We investigated the rate of ophthalmologic examinations to detect endogenous endophthalmitis in patients with pyogenic liver abscesses (PLAs) and the incidence and risk factors of endophthalmitis from a PLA caused by Klebsiella pneumoniae (PLA-K).

DESIGN

Retrospective case series.

METHODS

A total of 536 patients admitted to a university hospital in Korea to treat PLAs during 2012-2022 were included. The proportion of patients who were referred for ophthalmologic examinations was investigated and the incidence of endophthalmitis in 248 patients with PLA-K was calculated. Univariate and multivariate logistic regression analyses were performed to define risk factors including demographic characteristics, underlying diseases, radiologic findings, and systemic conditions.

RESULTS

A comprehensive ophthalmologic examination was performed in 73.7% of all patients with PLAs, and the incidence of endophthalmitis from a PLA-K was 7.3%. A liver abscess >5 cm increased the incidence of endogenous endophthalmitis 4-fold compared with smaller abscesses (odds ratio [OR] = 4.01 [95% confidence interval {CI}, 1.02-15.78], P = .047) and portal or hepatic vein thrombophlebitis increased the incidence approximately 4-fold (OR = 4.04 [95% CI, 1.10-14.83], P = .036). Acute cholangitis was approximately 8-fold (OR = 8.33 [95% CI, 1.25-55.71], P = .029), and disseminated intravascular coagulation was approximately 6-fold (OR = 5.76 [95% CI, 1.22-27.21], P = .027) more related to prevalence of endophthalmitis. Other extrahepatic infections increased the incidence approximately 43-fold (OR = 43.06 [95% CI, 10.14-182.90], P < .001).

CONCLUSIONS

Clinicians should consider the risk of endogenous endophthalmitis when PLA-K patients have large liver abscesses (>5 cm), acute cholangitis, portal or hepatic vein thrombophlebitis, disseminated intravascular coagulation, or other extrahepatic infections.

Pyogenic liver abscess complicated with endogenous endophthalmitis caused by Klebsiella pneumoniae: A case report and Literature Review

OBJECTIVE

Pyogenic liver abscess (PLA) is a common surgical infectious disease caused by various pathogens. Klebsiella pneumoniae is a relatively recent cause, often affecting patients with low immunity. Endogenous endophthalmitis (EE), a rare and serious complication of PLA, may appear with eye symptoms before PLA. By reviewing a case of Klebsiella pneumoniae-induced PLA complicated with EE, we want to summarize the information about the characteristics, causes, and complications of PLA based on the literature review.

METHODS

This case report describes a 37-year-old male who had fever high to 39°C for 10 days experienced blurred vision followed by nonlight perception vision. He reported a history of diabetes irregularly taking oral medications and insulin therapy. Imaging examination found a large low-density area in the right lobe of the liver with an unclear border and vague surrounding fat gap. The blood culture was not positive. The culture of the drainage fluid from the liver puncture showed Klebsiella pneumonia. Blood and liver puncture drainage fluid were sent for microbial high-throughput gene detection with next-generation sequencing technology (NGS), which confirmed the diagnosis of Klebsiella pneumoniae-induced PLA complicated with EE.

RESULTS

The patient's surgical incision had healed well at discharge, and he could feel light at his left eye. But the patient was lost to follow-up since the third month after discharge.

CONCLUSION

By reviewing this case and summarize the information about the characteristics, causes, and complications of PLA based on the literature review, we concluded that it is necessary to promptly perform liver puncture drainage and empirically use antibiotics for patients with PLA, especially those with poor glycemic control, to avoid serious complications such as EE.

Cost-minimization analysis of oral versus intravenous antibiotic treatment for Klebsiella pneumoniae liver abscess

A cost-minimization analysis was conducted for Klebsiella pneumoniae liver abscess (KLA) patients enrolled in a randomized controlled trial which found oral ciprofloxacin to be non-inferior to intravenous (IV) ceftriaxone in terms of clinical outcomes. Healthcare service utilization and cost data were obtained from medical records and estimated from self-reported patient surveys in a non-inferiority trial of oral ciprofloxacin versus IV ceftriaxone administered to 152 hospitalized adults with KLA in Singapore between November 2013 and October 2017. Total costs were evaluated by category and payer, and compared between oral and IV antibiotic groups over the trial period of 12 weeks. Among the subset of 139 patients for whom cost data were collected, average total cost over 12 weeks was $16,378 (95% CI, $14,620-$18,136) for the oral ciprofloxacin group and $20,569 (95% CI, $18,296-$22,842) for the IV ceftriaxone group, largely driven by lower average outpatient costs, as the average number of outpatient visits was halved for the oral ciprofloxacin group. There were no other statistically significant differences, either in inpatient costs or in other informal healthcare costs. Oral ciprofloxacin is less costly than IV ceftriaxone in the treatment of Klebsiella liver abscess, largely driven by reduced outpatient service costs.Trial registration: ClinicalTrials.gov Identifier NCT01723150 (7/11/2012).

Occurrence and Molecular Study of Hypermucoviscous/Hypervirulence Trait in Gut Commensal K. pneumoniae from Healthy Subjects

Hypervirulent Klebsiella pneumoniae (hvKp) is emerging worldwide. Hypermucoviscousity is the characteristic trait that distinguishes it from classic K. pneumoniae (cKp), which enables Kp to cause severe invasive infections. This research aimed to investigate the hypermucoviscous Kp (hmvKp) phenotype among gut commensal Kp isolated from healthy individuals and attempted to characterize the genes encoding virulence factors that may regulate the hypermucoviscosity trait. Using the string test, 50 identified Kp isolates from healthy individuals’ stool samples were examined for hypermucoviscosity and investigated by transmission electron microscopy (TEM). Antimicrobial susceptibility profiles of Kp isolates were determined using the Kirby Bauer disc method. Kp isolates were tested for genes encoding different virulence factors by PCR. Biofilm formation was assayed by the microtiter plate method. All Kp isolates were multidrug-resistant (MDR). Phenotypically, 42% of isolates were hmvKp. PCR-based genotypic testing revealed the hmvKp isolates belonged to capsular serotype K2. All study Kp isolates harbored more than one virulence gene. The genes magA and rmpA were not detected, while the terW gene was present in all isolates. The siderophores encoding genes entB and irp2 were most prevalent in hmvKp isolates (90.5%) and non-hmvKp (96.6%), respectively. hmvKp isolates harbored the genes wabG and uge with rates of 90.5% and 85.7%, respectively. The outcomes of this research highlight the potential health risk of commensal Kp to cause severe invasive diseases, owing to being hmvKp and MDR, and harboring multiple virulence genes. The absence of essential genes related to hypermucoviscosity such as magA and rmpA in hmvKp phenotypes suggests the multifactorial complexity of the hypermucoviscosity or hypervirulence traits. Thus, further studies are warranted to verify the hypermucoviscosity-related virulence factors among pathogenic and commensal Kp in different colonization niches.

Liver abscess complicated with multiple organ invasive infection caused by hematogenous disseminated hypervirulent Klebsiella pneumoniae: A case report

Hypervirulent Klebsiella pneumoniae (hvKp) causes increasing infections in healthy individuals from the community. In severe cases, it can cause multiple organ infection with invasive metastasis of blood sources, seriously threatening the patients' life. Rapid and accurate diagnosis of the pathogen becomes the key to timely antibiotic treatment to improve the prognosis. This article reports a case of liver abscess complicated with multiple organ invasive infection caused by hematogenous-disseminated hvKp. K. pneumoniae was identified by culture and metagenomic next-generation sequencing (mNGS) using blood and liver abscess drainage fluid. The isolates from the two samples were subsequently identified with high homology (99.999%) by whole genome sequencing. In addition, multiple virulence genes were detected in the two isolates and the string test was positive, indicating hvKp with hypermucoviscosity phenotype. Multiple antibiotic treatments were given. The conditions of the patient were stable but the temperature remained high. Surgical drainage treatment was performed, and the patient's body temperature immediately dropped to normal. He finally recovered after 6 months of follow-up. mNGS using body fluids can facilitate the rapid diagnosis of pathogens. For hvKp infection, choosing a better antibiotic therapy and receiving surgical drainage can significantly improve the prognosis of the patient.

Clinical and genomic characterization of hypervirulent Klebsiella pneumoniae (hvKp) infections via passive surveillance in Southern California, 2020–2022

Hypervirulent Klebsiella pneumoniae (hvKp) is more invasive and virulent than classical K. pneumoniae, and requires specialized treatment. To raise clinical awareness, this study determined the prevalence, clinical characteristics, and genomic epidemiology of hvKp infections in Southern California (SoCal) by conducting a passive surveillance in a single large academic medical center. We report here that hvKp infections were more common than expected, accounting for 2.6% of invasive K. pneumoniae infections, and presented with a wide disease spectrum, occasionally mimicking tumors, even co-infecting a COVID-19 patient. Most infections were community acquired with no recent international travel, suggesting hvKp strains are circulating in the community. Genomic analysis revealed genetic diversity, with the K1-ST23 lineage predominating but not clonal, and multiple sequence types of K2 including a SoCal unique K2-ST66 sublineage that had been unrecognized. Our findings highlight the urgency of heightened awareness of hvKp infection in the US, the need for rapid diagnosis of hvKp, and the necessity of implementing robust surveillance programs for hvKp at the institutional or local level.

Emergence of K1 ST23 and K2 ST65 hypervirulent klebsiella pneumoniae as true pathogens with specific virulence genes in cryptogenic pyogenic liver abscesses Shiraz Iran

Hypervirulent Klebsiella pneumoniae (hvKp) pathotype is emerging worldwide in pyogenic liver abscesses (PLAs). However, the role of virulence factors in pathogenicity remains unclear. On the other hand, the epidemiology of PLAs in Iran is unknown. From July 2020 to April 2022, bacterial species were isolated and identified from the drainage samples of 54 patients with PLAs. K. pneumoniae as the most common pathogen of pyogenic liver abscesses was identified in 20 (37%) of the 54 patients. We analyzed the clinical and microbiological characteristics of K. pneumoniae-related pyogenic liver abscesses. Antibiotic susceptibility testes and string test were performed. 16S rRNA, antibiotic resistance, and virulence genes were determined by polymerase chain reaction amplification. Clonal relatedness of isolates was identified by multilocus sequence typing. Virulence levels were assessed in the Galleria mellonella larval infection model. Four hvKp isolates (K1/K2) were found to be responsible for cryptogenic PLAs, and 16 classical K. pneumoniae isolates (non-K1/K2) were associated with non-cryptogenic PLAs. Three capsular serotype K1 strains belonged to sequence type 23 (ST23) and one K2 strain to ST65. Meanwhile, the non-K1/K2 strains belonged to other STs. ST231 was the most common strain among the classical K. pneumoniae strains. Compared with the non-K1/K2 strains, capsular serotypes K1/K2 strains were less resistant to antibiotics, had positive string test results, and had more virulence genes. In Galleria mellonella, a concentration of 10⁶ colony-forming units of the K1 hvKp strain resulted in 100% death at 24 hours, confirming the higher virulence of the hvKp strain compared with cKp. K. pneumoniae isolates represented that the acquisition of any plasmid or chromosomal virulence genes contributes to pathogenicity and high prevalence in PLAs. Meanwhile, hvKp isolates with a specific genetic background were detected in cryptogenic PLAs.

Capsule type defines the capability of Klebsiella pneumoniae in evading Kupffer cell capture in the liver

Polysaccharide capsule is the main virulence factor of K. pneumoniae, a major pathogen of bloodstream infections in humans. While more than 80 capsular serotypes have been identified in K. pneumoniae, only several serotypes are frequently identified in invasive infections. It is documented that the capsule enhances bacterial resistance to phagocytosis, antimicrobial peptides and complement deposition under in vitro conditions. However, the precise role of the capsule in the process of K. pneumoniae bloodstream infections remains to be elucidated. Here we show that the capsule promotes K. pneumoniae survival in the bloodstream by protecting bacteria from being captured by liver resident macrophage Kupffer cells (KCs). Our real-time in vivo imaging revealed that blood-borne acapsular K. pneumoniae mutant is rapidly captured and killed by KCs in the liver sinusoids of mice, whereas, to various extents, encapsulated strains bypass the anti-bacterial machinery in a serotype-dependent manner. Using capsule switched strains, we show that certain high-virulence (HV) capsular serotypes completely block KC’s capture, whereas the low-virulence (LV) counterparts confer partial protection against KC’s capture. Moreover, KC’s capture of the LV K. pneumoniae could be in vivo neutralized by free capsular polysaccharides of homologous but not heterologous serotypes, indicating that KCs specifically recognize the LV capsules. Finally, immunization with inactivated K. pneumoniae enables KCs to capture the HV K. pneumoniae. Together, our findings have uncovered that KCs are the major target cells of K. pneumoniae capsule to promote bacterial survival and virulence, which can be reversed by vaccination.

Klebsiella pneumoniae is a major human pathogen. While capsule is the main virulence factor of the pathogen, only several of more than 80 capsule serotypes are frequently identified in invasive infections. However, it remains unclear how capsule contributes to K. pneumoniae virulence. Here we show that capsule type defines K. pneumoniae virulence by differential escape of immune surveillance in the liver. While low-virulence (LV) types are captured by Kupffer cells (KCs), high-virulence (HV) types circumvent the anti-bacterial machinery. Further, inactivated K. pneumoniae vaccine enables KCs to capture the HV K. pneumoniae and protects mice from lethal infection. Our findings explain the clinical prevalence of HV capsule types, and provide promising insights for future vaccine development.

Metagenome Analysis of the Bacterial Characteristics in Invasive Klebsiella Pneumoniae Liver Abscesses

Background

Klebsiella pneumoniae liver abscess (KPLA) combined with extrahepatic migratory infection (EMI) is defined as invasive KPLA (IKPLA) and is associated with a poor prognosis. The mechanism of IKPLA formation is yet to be elucidated. In this study, metagenomic sequencing was used to compare the bacterial characteristics between IKPLA and KPLA to explore the underlying mechanism of invasiveness.

Methods

Clinical details, imaging, and microbial features were retrospectively evaluated by medical record review. Metagenomic sequencing was performed on the pus samples of liver abscesses whose culture results were indicative of monomicrobial Klebsiella pneumoniae (K. pneumoniae). Bacterial diversity and composition in IKPLA and KPLA were comparatively analyzed, and the key pathways and genes that may affect invasiveness were further explored.

Results

Sixteen patients were included in this study. Five patients with EMI were included in the IKPLA group, and the other eleven patients without EMI were assigned to the KPLA group. There was no statistical difference in the hypermucoviscous phenotype and serotype of K. pneumoniae between the two groups. The bacterial diversity of IKPLA was lower than that of KPLA. The abundant taxa in the IKPLA group were primarily species of unclassified Enterobacteriaceae and K. pneumoniae. The KPLA group had a high abundance of the genera Tetrasphaera and Leuconostoc. Metabolic pathway genes represented most of the enriched genes in IKPLA. Fourteen pathogenic genes with significant differences in abundance were identified between the two groups, including ybtS, fepC, phoQ, acrB, fimK, magA, entC, arnT, iucA, fepG, oqxB, entA, tonB, and entF (p < 0.001).

Conclusion

The diversity and bacterial composition of IKPLA were significantly different from those of KPLA. Microbiological changes in the abscess, activation of the related metabolic pathways, and the pathogenic gene expression may constitute a novel mechanism that regulates the invasiveness of KPLA.

Extensively Drug-Resistant Klebsiella pneumoniae Counteracts Fitness and Virulence Costs That Accompanied Ceftazidime-Avibactam Resistance Acquisition

The ability of extensively drug-resistant (XDR) Klebsiella pneumoniae to rapidly acquire resistance to novel antibiotics is a global concern. Moreover, Klebsiella clonal lineages that successfully combine resistance and hypervirulence have increasingly occurred during the last years. However, the underlying mechanisms of counteracting fitness costs that accompany antibiotic resistance acquisition remain largely unexplored. Here, we investigated whether and how an XDR sequence type (ST)307 K. pneumoniae strain developed resistance against the novel drug combination ceftazidime-avibactam (CAZ-AVI) using experimental evolution. In addition, we performed in vitro and in vivo assays, molecular modeling, and bioinformatics to identify resistance-conferring processes and explore the resulting decrease in fitness and virulence. The subsequent amelioration of the initial costs was also addressed. We demonstrate that distinct mutations of the major nonselective porin OmpK36 caused CAZ-AVI resistance that persists even upon following a second experimental evolution without antibiotic selection pressure and that the Klebsiella strain compensates the resulting fitness and virulence costs. Furthermore, the genomic and transcriptomic analyses suggest the envelope stress response regulator rpoE and associated RpoE-regulated genes as drivers of this compensation. This study verifies the crucial role of OmpK36 in CAZ-AVI resistance and shows the rapid adaptation of a bacterial pathogen to compensate fitness- and virulence-associated resistance costs, which possibly contributes to the emergence of successful clonal lineages.

IMPORTANCE Extensively drug-resistant Klebsiella pneumoniae causing major outbreaks and severe infections has become a significant challenge for health care systems worldwide. Rapid resistance development against last-resort therapeutics like ceftazidime-avibactam is a significant driver for the accelerated emergence of such pathogens. Therefore, it is crucial to understand what exactly mediates rapid resistance acquisition and how bacterial pathogens counteract accompanying fitness and virulence costs. By combining bioinformatics with in vitro and in vivo phenotypic approaches, this study revealed the critical role of mutations in a particular porin channel in ceftazidime-avibactam resistance development and a major metabolic regulator for ameliorating fitness and virulence costs. These results highlight underlying mechanisms and contribute to the understanding of factors important for the emergence of successful bacterial pathogens.

The Incidence of Septic Pulmonary Embolism in Patients with Klebsiella pneumoniae Liver Abscess: A Systematic Review and Meta-analysis

Background: Septic pulmonary embolism (SPE) is an associated complication of Klebsiella pneumoniae liver abscess (KPLA). However, previous studies have reported that its incidence varies widely. We conducted a systematic review and meta-analysis to investigate the incidence of SPE in patients with KPLA. We further analyzed their clinical and computed tomography (CT) features. Methods: Two researchers reviewed PubMed, EMBASE, Web of Science, and Cochrane Library databases to identify the articles that reported SPE in patients with KPLA. The search was conducted from the date of establishment of each database up to January 2021. After screening the articles and extracting the data, we used Review Manager 5.3 for analysis and processing. Results: We selected six articles that included 1,158 patients with KPLA. Of these, 70 patients had SPE. The pooled incidence of SPE was 6% (95% confidence interval, 3%–9%). Among patients with SPE, 85% were men, 72% had diabetes, and 52% displayed the feeding vessel sign on the chest CT. The mortality rate was 12%. Quality assessment revealed that half of the included studies had a high quality. Conclusion: The pooled incidence of SPE in patients with KPLA was 6%. Men and patients with diabetes were more prone to SPE. For patients with KPLA who had SPE as an associated complication, the mortality rate was approximately 12%.

Development of Klebsiella pneumoniae Capsule Polysaccharide-Conjugated Vaccine Candidates Using Phage Depolymerases

Klebsiella pneumoniae is an important pathogen associated with nosocomial infection and has developed increasing resistance to antibiotics such as extended-spectrum β-lactams and carbapenem. In recent years, K. pneumoniae isolates have emerged as a major cause of global community-acquired infections such as pneumonia and pyogenic liver abscess. Although serotypes K1 and K2 have been identified as the predominant capsular types associated with invasive infections, no K. pneumoniae vaccine is commercially available, probably due to immunogenicity loss in the traditional depolymerization method to obtain capsule polysaccharide (CPS) for the preparation of conjugated vaccine. In this study, we successfully retained immunogenicity by using K1 (K1-ORF34) and K2 (K2-ORF16) CPS depolymerases that were identified from phages to cleave K1 and K2 CPSs into intact structural units of oligosaccharides with intact modifications. The obtained K1 and K2 oligosaccharides were separately conjugated with CRM197 carrier protein to generate CPS-conjugated vaccines. Immunization experiments of mice showed both K1 and K2 CPS-conjugated vaccines induced anti-CPS antibodies with 128-fold and 64-fold increases of bactericidal activities, respectively, compare to mice without vaccinations. Challenge tests indicated that K1 or K2 CPS-conjugated vaccine and divalent vaccine (a mixture of K1 and K2 CPS-conjugated vaccines) protected mice from subsequent infection of K. pneumoniae by the respective capsular type. Thus, we demonstrated K1 and K2 CPS-conjugated vaccines prepared by CPS depolymerases is a promising candidate for developing vaccines against human K. pneumoniae infections.

Genetic Diversity and Pathogenic Features in Klebsiella pneumoniae Isolates from Patients with Pyogenic Liver Abscess and Pneumonia

While Klebsiella pneumoniae is a common cause of nosocomial and community-acquired infections, including pneumonia and pyogenic liver abscess, little is known about the population structure of this bacterium. In this study, we investigated the prevalence and molecular characteristics of K. pneumoniae isolates from carriers, pyogenic liver abscess patients, and pneumonia patients, and genomic and phenotypic assays were used to determine the differences among the isolates. A total of 232 K. pneumoniae isolates were subtyped into 74 sequence types (STs). The isolates from different sources had their own STs, and the predominant subtypes in liver abscess and pneumonia patients were ST23 and ST11, respectively. Pangenome analysis also distinguished three phylogroups that were consistent with the isolate sources. The isolates collected from liver abscess patients carried significantly more virulence factors, and those from pneumonia patients harbored significantly more resistance genes and replicons. Almost all isolate STs (93/97 [95.88%]) from liver abscesses strongly correlated with the virulence factor salmochelin, while most pneumonia isolate STs (52/53 [98.11%]) from pneumonia did not correlate with salmochelin. The isolates collected from liver abscesses showed higher virulence in the cytotoxicity and mouse models. These data provide genomic support for the proposal that isolates collected from carriers, liver abscess patients, and pneumonia patients have distinct genomic features. Isolates from the different sources are largely nonoverlapping, suggesting that different patients may be infected via different sources. Further studies on the pathogenic mechanisms of salmochelin and other virulence factors will be required.

IMPORTANCE While Klebsiella pneumoniae is a common cause of nosocomial and community-acquired infections, including pneumonia and pyogenic liver abscess, little is known about the population structure of this bacterium. We collected 232 isolates from carriers, pyogenic liver abscess patients, and pneumonia patients, and the isolates from different sources had their own sequence types. Pangenome analysis also distinguished three phylogroups that were consistent with the isolate sources. The isolates collected from liver abscess patients carried significantly more virulence factors, and those from pneumonia patients harbored significantly more resistance genes and replicons. Besides, there was a strong link between salmochelin and liver abscess. The isolates collected from liver abscesses also showed higher virulence in the cytotoxicity and mouse models. Isolates collected from different sources have distinct genomic features, suggesting that different patients may be infected via different sources.

Multi-system Klebsiella sepsis: A tale of destruction form lung to eye

Klebsiella pneumoniae, found in the gastrointestinal flora is a causative agent of hospital-acquired infections. Although isolated organ infections are common, reports of multi-system involvement are rare. We report on a susceptible patient presenting with disseminated Klebsiella infection with concurrent multi-organ disease involving the lung, liver, prostate and eye. He recovered after prolonged therapy but suffered from permanent sequalae. Early diagnosis and aggressive therapy is facilitated by awareness and a high degree of suspicion in at-risk patient groups.

Clinical characteristics and outcome of patients with enterococcal liver abscess

Epidemiology of bacteria isolated from pyogenic liver abscesses change, and an increase in enterococci has been reported in European hospitals. The aim of this study was to investigate the clinical characteristics and outcome of enterococcal PLA. We performed a retrospective analysis of patients with microbiologically confirmed PLA at three German university centers. Indicators of enterococcal PLA were determined using binary logistic regression, and survival analysis was performed using Kaplan-Meier statistics and Cox regression analysis. Enterococci were isolated in 51/133 (38%) patients with PLA. Patients with enterococcal PLA had smaller abscess diameter (4.8 vs. 6.7 cm, p = 0.03) than patients with non-enterococcal PLA, but had more frequent polymicrobial culture results. In univariate logistic regression analysis, alcohol abuse (OR 3.94, 95% CI 1.24-12.49, p = 0.02), hepatobiliary malignancies (OR 3.90, 95% CI 1.86-8.18, p < 0.001) and cirrhosis (OR 6.36, 95% CI 1.27-31.96, p = 0.02) were associated with enterococcal PLA. Patients with enterococcal PLA had a higher mortality than patients with non-enterococcal PLA (hazard ratio 2.92; 95% confidence interval 1.09-7.80; p = 0.03), which remained elevated even after excluding patients with hepatobiliary malignancies, cirrhosis, and transplant recipients in a sensitivity analysis. The increased mortality was associated with non-fecal enterococci but not in patients with Enterococcus faecalis. In this retrospective, multicenter study, enterococcal PLA was common and indicated an increased risk of mortality, underscoring the need for close clinical monitoring and appropriate treatment protocols in these patients.

A population-based study of pyogenic liver abscess in Korea: Incidence, mortality and temporal trends during 2007-2017

BACKGROUND/AIMS

Although the epidemiology of pyogenic liver abscess (PLA) continues to change, only a few population-based studies have been conducted in Korea. This study investigated the epidemiology and clinical outcomes of PLA patients during a period of 10 years.

METHODS

We analysed the Health Insurance Review and Assessment Service data between 2007 and 2017. The data included annual incidence rates, demographic data, underlying diseases, complications and mortality of PLA patients.

RESULTS

The annual incidence of PLA for all age groups was 10.9 per 100 000 population. The incidence was gradually increased from 5.7 per 100 000 in 2007 to 14.4 per 100 000 in 2017. In patients with liver abscess, the prevalence of diabetes and malignancy were 37.24% and 26.5% respectively. Metastatic infection was reported in 1.74% of the patients, and endophthalmitis was most common. The mean in-hospital mortality was 9.6%, and there was no significant difference in mortality by year during the observation period. Mortality increased with age and was greatly affected by the underlying diseases, especially cancer. Based on the multivariate analysis results, the mortality of PLA patients was associated with older age, female sex, diabetes, malignancy and chronic kidney disease.

CONCLUSION

The PLA incidence is rapidly increasing in Korea, especially in people with comorbidities. In addition, the causes and risk factors of PLA infections are changing and thus further research on epidemiology, different diagnosis and management approaches is required.

Endogenous Endophthalmitis and Liver Abscess: A Metastatic Infection or a Coincidence?

Klebsiella pneumoniae is a gram-negative pathogen that is a common cause of severe infections, including pyogenic liver abscess. Dissemination of K. pneumoniae to other organs, including the eye, is associated with significant morbidity and mortality. In the particular case of endogenous endophthalmitis (EE) by K. pneumoniae the prognosis is poor. We report the case of a middle-aged female with K. pneumoniae liver abscess. The patient developed metastatic endophthalmitis that was aggressively treated with systemic antibiotics. The liver abscess resolved with antimicrobials and percutaneous transhepatic drainage, but regarding the endophthalmitis she was discharged from our hospital without recovery of her eyesight. Metastatic spread to the eye should be considered in all patients with liver abscesses who experience ocular signs and symptoms in order to establish a timely diagnosis of EE.

Prevalence and molecular characterization of antibiotic resistance and associated genes in Klebsiella pneumoniae isolates: A clinical observational study in different hospitals in Chattogram, Bangladesh

Objective

This study was performed to investigate the prevalence of multidrug resistance and molecular characterization of Klebsiella pneumoniae (KPN) from clinical isolates in the southern region of Bangladesh. Additional analysis of the prevalence of bla_NDM-1, bla_SHV-11, uge genes of KPN was also carried out among these clinical isolates.

Method

The study was carried out using 1000 clinical isolates collected from two different hospitals of Chattogram. A drug susceptibility test was performed by the disk diffusion method to detect KPN’s response to 16 antibiotics. The presence of antibiotic-resistant and (or) virulent genes bla_NDM-1, bla_SHV-11, uge were investigated using the PCR technique. Isolates having bla_NDM-1, bla_SHV-11, uge gene were further validated by sequencing followed by phylogenetic analysis. Phylogenetic relationships among these isolates were determined by Clustal omega and MEGA7.

Result

A total of 79%, 77%, 74.9%, 71%, 66% and 65% isolates exhibited resistance against cefuroxime, cefixime, cefotaxime, ceftazidime, cefepime and ceftriaxone respectively. The frequency of resistance to other antibiotics varied from 26.5% to 61.8%. PCR analysis showed that 64% of strains harbored bla_NDM-1 gene, and 38% strains harbored bla_SHV-11 gene. Moreover, 47% of samples were carrying uge gene, and 19% of samples carried bla_NDM-1, bla_SHV-11, uge genes together.

Conclusion

In this study, we’ve analysed the pattern of expression as well as prevalence of bla_NDM-1, bla_SHV-11, and uge genes in Klebsiella isolates. Upon molecular and statistical analysis, we found a high prevalence of multi-drug resistance KPN strains in the isolates. The Klebsiella isolates were confirmed to harbor multiple ESBL genes and 64% of the isolates were found to be producing NDM-1. As multidrug resistance is an alarming issue, continuous surveillance and routine clinical detection of resistant bacteria and plasmids are necessary to prevent catastrophic public health incidents.

Epidemiology and risk factors for pyogenic liver abscess in the Calgary Health Zone revisited: a population-based study

Background

Pyogenic liver abscess (PLA), although uncommon in North America, is associated with significant morbidity and mortality. We sought to re-examine the epidemiology, risk factors, and outcomes of PLA in a large, diverse Canadian health zone.

Methods

All Calgary Health Zone (CHZ) residents aged ≥20 with PLA between 2015 and 2017 were identified. Incidence and mortality rates were calculated using census data. Risk factors for PLA were identified using a multivariate analysis. Data was compared to 1999–2003 data, also collected in the CHZ.

Results

There were 136 patients diagnosed with PLA between 2015 and 2017. Incidence rate during this period increased significantly relative to 1999–2003 (3.7 vs 2.3 cases/100,000 population, p < 0.01), however, mortality rates remained similar. The microbiological composition of PLA did not change over this 15-year time period but the number of antimicrobial resistant isolates did increase (8% vs 1%, p = 0.04). The greatest risk factors for PLA relative to general populations included current malignancy, liver-transplant, end-stage renal disease, and cirrhosis. Thirty-day mortality was 7.4% and independent risk factors included polymicrobial bacteremia, absence of abscess drainage, congestive-heart failure, a history of liver disease, and admission bilirubin.

Conclusions

Pyogenic liver abscess is a health concern with rising incidence rate. The increasing prevalence of comorbidities in our population and factors that are associated with risk of PLA suggests this will continue to be an emerging diagnosis of concern. Increasing prevalence of antibiotic resistant organisms compounding unclear optimal treatment regimens is an issue that requires urgent study.

Hepatosplenic Abscess From Klebsiella pneumoniae in Poorly Controlled Diabetic

Invasive Klebsiella pneumoniae infection and pyogenic liver abscess in patients with underlying diabetes mellitus has been well described over the past 3 decades, predominantly in the Southeast Asian population, especially in Taiwan and Korea. K pneumoniae has now become the most common causative pathogen of pyogenic liver abscess in Asian countries. This shift from Escherichia coli to K pneumoniae may also be increasingly occurring in the United States of America and European countries. Compared with the >80% incidence described in Taiwan, the incidence in the United States is still reported to be lower, around 30% to 40%. However, as more evidence and reports come to light, it has become of prime importance to recognize Klebsiella as a significant emerging cause of metastatic infections in patients with uncontrolled diabetes in the United States and not just Southeast Asia, given the significant morbidity and mortality associated with the condition. In this article, we discuss the case of a 53-year-old African American female who presented with diabetic ketoacidosis and was subsequently found to have K pneumoniae pyogenic liver abscess primarily in the left hepatic lobe, bacteremia, and septic metastases to the spleen. She required extensive percutaneous drainage of abscesses and a prolonged course of multiple antibiotics. This case illustrates the growing incidence of invasive K pneumoniae infection in the diabetic population in the United States, and better patient outcomes from prompt recognition and treatment.

Oral vs Intravenous Antibiotics for Patients With Klebsiella pneumoniae Liver Abscess: A Randomized, Controlled Noninferiority Study

BACKGROUND

Klebsiella pneumoniae liver abscess (KLA) is emerging worldwide due to hypermucoviscous strains with a propensity for metastatic infection. Treatment includes drainage and prolonged intravenous antibiotics. We aimed to determine whether oral antibiotics were noninferior to continued intravenous antibiotics for KLA.

METHODS

This noninferiority, parallel group, randomized, clinical trial recruited hospitalized adults with liver abscess and K. pneumoniae isolated from blood or abscess fluid who had received ≤7 days of effective antibiotics at 3 sites in Singapore. Patients were randomized 1:1 to oral (ciprofloxacin) or intravenous (ceftriaxone) antibiotics for 28 days. If day 28 clinical response criteria were not met, further oral antibiotics were prescribed until clinical response was met. The primary endpoint was clinical cure assessed at week 12 and included a composite of absence of fever in the preceding week, C-reactive protein <20 mg/L, and reduction in abscess size. A noninferiority margin of 12% was used.

RESULTS

Between November 2013 and October 2017, 152 patients (mean age, 58.7 years; 25.7% women) were recruited, following a median 5 days of effective intravenous antibiotics. A total of 106 (69.7%) underwent abscess drainage; 71/74 (95.9%) randomized to oral antibiotics met the primary endpoint compared with 72/78 (92.3%) randomized to intravenous antibiotics (risk difference, 3.6%; 2-sided 95% confidence interval, -4.9% to 12.8%). Effects were consistent in the per-protocol population. Nonfatal serious adverse events occurred in 12/72 (16.7%) in the oral group and 13/77 (16.9%) in the intravenous group.

CONCLUSIONS

Oral antibiotics were noninferior to intravenous antibiotics for the early treatment of KLA.

CLINICAL TRIALS REGISTRATION

NCT01723150.

Successful Medical Treatment for Peritonitis Resulting from a Large Pyogenic Liver Abscess Rupture

The rupture of a pyogenic liver abscess (PLA) with peritonitis is a rare occurrence but a surgical emergency with a high mortality rate in the case of gas-forming PLA. Rare cases of ruptured PLA that recovered completely with only medical treatment have been reported. This paper reports a case of a large PLA rupture with peritonitis. In this case, surgical intervention was too risky because of the patient's age and poor general condition. The patient recovered fully with appropriate antibiotic therapy and sufficient percutaneous drainage. Therefore, medical treatment may be considered an alternative option in cases of a ruptured large PLA with peritonitis if surgical intervention is too risky.

Prophylaxis and Treatment against Klebsiella pneumoniae: Current Insights on This Emerging Anti-Microbial Resistant Global Threat

Klebsiella pneumoniae (Kp) is an opportunistic pathogen and the leading cause of healthcare-associated infections, mostly affecting subjects with compromised immune systems or suffering from concurrent bacterial infections. However, the dramatic increase in hypervirulent strains and the emergence of new multidrug-resistant clones resulted in Kp occurrence among previously healthy people and in increased morbidity and mortality, including neonatal sepsis and death across low- and middle-income countries. As a consequence, carbapenem-resistant and extended spectrum β-lactamase-producing Kp have been prioritized as a critical anti-microbial resistance threat by the World Health Organization and this has renewed the interest of the scientific community in developing a vaccine as well as treatments alternative to the now ineffective antibiotics. Capsule polysaccharide is the most important virulence factor of Kp and plays major roles in the pathogenesis but its high variability (more than 100 different types have been reported) makes the identification of a universal treatment or prevention strategy very challenging. However, less variable virulence factors such as the O-Antigen, outer membrane proteins as fimbriae and siderophores might also be key players in the fight against Kp infections. Here, we review elements of the current status of the epidemiology and the molecular pathogenesis of Kp and explore specific bacterial antigens as potential targets for both prophylactic and therapeutic solutions.

Virulence Factors in Hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP) has spread globally since first described in the Asian Pacific Rim. It is an invasive variant that differs from the classical K. pneumoniae (cKP), with hypermucoviscosity and hypervirulence, causing community-acquired infections, including pyogenic liver abscess, pneumonia, meningitis, and endophthalmitis. It utilizes a battery of virulence factors for survival and pathogenesis, such as capsule, siderophores, lipopolysaccharide, fimbriae, outer membrane proteins, and type 6 secretion system, of which the former two are dominant. This review summarizes these hvKP-associated virulence factors in order to understand its molecular pathogenesis and shed light on new strategies to improve the prevention, diagnosis, and treatment of hvKP-causing infection.

Finding Order in the Chaos: Outstanding Questions in Klebsiella pneumoniae Pathogenesis

Klebsiella pneumoniae are Gram-negative facultative anaerobes that are found within host-associated commensal microbiomes, but they can also cause a wide range of infections that are often difficult to treat. These infections are caused by different pathotypes of K. pneumoniae, called either classical or hypervirulent strains.

Klebsiella pneumoniae are Gram-negative facultative anaerobes that are found within host-associated commensal microbiomes, but they can also cause a wide range of infections that are often difficult to treat. These infections are caused by different pathotypes of K. pneumoniae, called either classical or hypervirulent strains. These two groups are genetically distinct, inhabit nonoverlapping geographies, and cause different types of harmful infections in humans. These distinct bacterial groups have also been found to interact differently with the host immune system. Initial innate immune defenses against K. pneumoniae infection include complement, macrophages, neutrophils, and monocytes; these defenses are primary strategies employed by the host to clear infections. K. pneumoniae pathogenesis depends upon the interactions between the microbe and each of these host defenses, and it is becoming increasingly apparent that bacterial genetic diversity impacts the outcomes of these interactions. Here, we highlight recent advances in our understanding of K. pneumoniae pathogenesis, with a focus on how bacterial evolution and diversity impact K. pneumoniae interactions with mammalian innate immune host defenses. We also discuss outstanding questions regarding how K. pneumoniae can frustrate normal immune responses, capitalize upon states of immunocompromise, and cause infections with high mortality.

Deoxycholic Acid and Lithocholic Acid Alleviate Liver Injury and Inflammation in Mice with Klebsiella pneumoniae-Induced Liver Abscess and Bacteremia

Purpose

Klebsiella pneumoniae-induced liver abscess and baiacterem is a serious infectious disease with high mortality. Secondary bile acids (SBAs) are produced by intestinal flora through the metabolism of primary bile acids and play a role in promoting or inhibiting inflammation in some diseases. However, the immunomodulatory role of SBAs in bacterial infections of the liver remains unclear. This study aimed to investigate the anti-inflammatory and liver-protective effects of SBAs in K. pneumoniae-infected mice.

Methods

The absolute concentrations of deoxycholic acid (DCA) and lithocholic acid (LCA) in feces and serum were analyzed, and intestinal flora alterations between K. pneumoniae-infected and healthy control mice were examined. The effect of SBAs was investigated by analyzing the survival, tissue bacterial load, histopathology, and inflammatory factor levels in SBA-treated mice. The expression of crucial proteins implicated in the NF-κB pathway, as well as the G-protein-coupled bile acid receptor TGR5, was detected.

Results

The content of SBAs in feces and serum of the K. pneumoniae-infected group was significantly reduced, and significant changes in the composition of the intestinal flora were detected. The intestinal flora are directly related to the synthesis of SBAs. Ruminococcaceae levels in K. pneumoniae-infected mice were significantly lower than in healthy control mice. Oral administration of SBAs improved the survival and liver pathology of K. pneumoniae-infected mice, and reduced the bacterial load and the level of inflammatory factors. SBAs down-regulated the expression of key proteins in the NF-κB inflammatory signaling pathway, including the phosphorylation of IκBα and NF-κB p50 and the nuclear translocation of NF-κB p65. The protective effect of SBAs may be dependent on high TGR5 expression.

Conclusion

SBAs downregulate the NF-κB inflammatory signaling pathway through TGR5, protecting the liver and inhibiting inflammation in K. pneumoniae-induced liver abscess and bacteremia.

Outer membrane vesicles derived from hypervirulent Klebsiella pneumoniae stimulate the inflammatory response

Hypervirulent Klebsiella pneumoniae (hvKP), an increasing important pathotype, was initially recognized as a cause of severe liver abscesses and subsequently as a cause of other complications posing a clinical threat. Outer membrane vesicles (OMVs) secreted from abundant gram-negative bacteria are considered an important vehicle for delivery of effector molecules to target cells. However, the products and role in bacterial pathogenesis of OMVs secreted from hvKP, have not yet been determined. In order to examine the production of OMVs from hvKP and to determine their effects on the stimulation of the host innate immune response, we used ultracentrifugation to obtain homogeneous OMVs from hvKP ATCC 1706 cultured in vitro. Proteomic analysis was performed and hvKP OMVs were found to contain diverse proteins. Furthermore, hvKP OMVs exhibited discrepant cytotoxic effects on different cell types, in vitro. The vesicles induced the expression of proinflammatory cytokines including interleukin (IL)-6 and IL-8 in host cells. In addition, transtracheal injection of hvKP OMVs in wild-type mice led to an inflammatory response manifested by elevated levels of pro-inflammatory mediators including IL-6, IL-8 and TNF-α in bronchoalveolar lavage fluid (BAL), in accord with in vitro experiments. However, hvKP OMVs were insufficient to kill mice. In summary, OMVs originating from hvKP may serve to provoke the inflammatory response.

A global perspective on the convergence of hypervirulence and carbapenem resistance in Klebsiella pneumoniae

Hypervirulence and carbapenem resistance have emerged as two distinct evolutionary directions for Klebsiella pneumoniae, which pose a great threat in clinical settings. Multiple virulence factors contribute to hypervirulence, and the mechanisms of carbapenem resistance are complicated. However, more and more K. pneumoniae strains have been identified in recent years integrating both phenotypes, resulting in devastating clinical outcomes. Hypervirulent and carbapenem-resistant K. pneumoniae (CR-hvKP) emerged in the early 2010s and thereafter have become increasingly prevalent. CR-hvKP are primarily prevalent in Asia, especially China, but are reported all over the world. Mechanisms for the emergence of CR-hvKP can be summarised by three patterns: (i) carbapenem-resistant K. pneumoniae (CRKP) acquiring a hypervirulent phenotype; (ii) hypervirulent K. pneumoniae (hvKP) acquiring a carbapenem-resistant phenotype; and (iii) K. pneumoniae acquiring both a carbapenem resistance and hypervirulence hybrid plasmid. With their global dissemination, continued surveillance of the emergence of CR-hvKP should be more highly prioritised.

A Molecular Interaction Map of Klebsiella pneumoniae and Its Human Host Reveals Potential Mechanisms of Host Cell Subversion

Klebsiella pneumoniae is a leading cause of pneumonia and septicemia across the world. The rapid emergence of multidrug-resistant K. pneumoniae strains necessitates the discovery of effective drugs against this notorious pathogen. However, there is a dearth of knowledge on the mechanisms by which this deadly pathogen subverts host cellular machinery. To fill this knowledge gap, our study attempts to identify the potential mechanisms of host cell subversion by building a K. pneumoniae-human interactome based on rigorous computational methodology. The putative host targets inferred from the predicted interactome were found to be functionally enriched in the host's immune surveillance system and allied functions like apoptosis, hypoxia, etc. A multifunctionality-based scoring system revealed P53 as the most multifunctional protein among host targets accompanied by HIF1A and STAT1. Moreover, mining of host protein-protein interaction (PPI) network revealed that host targets interact among themselves to form a network (TTPPI), where P53 and CDC5L occupy a central position. The TTPPI is composed of several inter complex interactions which indicate that K. pneumoniae might disrupt functional coordination between these protein complexes through targeting of P53 and CDC5L. Furthermore, we identified four pivotal K. pneumoniae-targeted transcription factors (TTFs) that are part of TTPPI and are involved in generating host's transcriptional response to K. pneumoniae-mediated sepsis. In a nutshell, our study identifies some of the pivotal molecular targets of K. pneumoniae which primarily correlate to the physiological response of host during K. pneumoniae-mediated sepsis.

Maximal diameter of liver abscess independently predicts prolonged hospitalization and poor prognosis in patients with pyogenic liver abscess

Background/aims

This study aimed to investigate the factors associated with prolonged hospital stay and in-hospital mortality in patients with pyogenic liver abscess.

Methods

We retrospectively reviewed data from patients with pyogenic liver abscess who were admitted between 2005 and 2018 at three tertiary hospitals in Jeonbuk province, South Korea. Prolonged hospital stay was defined as a duration of hospital admission of more than 21 days.

Results

A total of 648 patients (406 men and 242 women) diagnosed with pyogenic liver abscess were enrolled in the study. The mean maximal diameter of the liver abscess was 5.4 ± 2.6 cm, and 74.9% of the lesions were single. The three groups were divided according to the maximal diameter of the abscess. Laboratory parameters indicated a more severe inflammatory state and higher incidence of complications and extrahepatic manifestations with increasing abscess size. Rates of percutaneous catheter drainage (PCD) insertion, multiple PCD drainage, and salvage procedures as well as duration of drainage were also higher in the large liver abscess group. Of note, the duration of hospitalization and in-hospital mortality were significantly higher in the large hepatic abscess group. A multivariate analysis revealed that underlying diabetes mellitus, hypoalbuminemia, high baseline high-sensitivity C-reactive protein (hs-CRP) and procalcitonin levels, and large maximal abscess diameter were independent factors associated with prolonged hospital stay. Regarding in-hospital mortality, acute kidney injury at admission and maximal diameter of the abscess were independent factors associated with in-hospital mortality.

Conclusions

A large maximal diameter of the liver abscess at admission indicated prolonged hospitalization and poor prognosis. More aggressive treatment strategies with careful monitoring are warranted in patients with large liver abscesses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-05873-7.

Core Genome Allelic Profiles of Clinical Klebsiella pneumoniae Strains Using a Random Forest Algorithm Based on Multilocus Sequence Typing Scheme for Hypervirulence Analysis

BACKGROUND

Hypervirulent Klebsiella pneumoniae (hvKP) infections can have high morbidity and mortality rates owing to their invasiveness and virulence. However, there are no effective tools or biomarkers to discriminate between hvKP and nonhypervirulent K. pneumoniae (nhvKP) strains. We aimed to use a random forest algorithm to predict hvKP based on core-genome data.

METHODS

In total, 272 K. pneumoniae strains were collected from 20 tertiary hospitals in China and divided into hvKP and nhvKP groups according to clinical criteria. Clinical data comparisons, whole-genome sequencing, virulence profile analysis, and core genome multilocus sequence typing (cgMLST) were performed. We then established a random forest predictive model based on the cgMLST scheme to prospectively identify hvKP. The random forest is an ensemble learning method that generates multiple decision trees during the training process and each decision tree will output its own prediction results corresponding to the input. The predictive ability of the model was assessed by means of area under the receiver operating characteristic curve.

RESULTS

Patients in the hvKP group were younger than those in the nhvKP group (median age, 58.0 and 68.0 years, respectively; P < .001). More patients in the hvKP group had underlying diabetes mellitus (43.1% vs 20.1%; P < .001). Clinically, carbapenem-resistant K. pneumoniae was less common in the hvKP group (4.1% vs 63.8%; P < .001), whereas the K1/K2 serotype, sequence type (ST) 23, and positive string tests were significantly higher in the hvKP group. A cgMLST-based minimal spanning tree revealed that hvKP strains were scattered sporadically within nhvKP clusters. ST23 showed greater genome diversification than did ST11, according to cgMLST-based allelic differences. Primary virulence factors (rmpA, iucA, positive string test result, and the presence of virulence plasmid pLVPK) were poor predictors of the hypervirulence phenotype. The random forest model based on the core genome allelic profile presented excellent predictive power, both in the training and validating sets (area under receiver operating characteristic curve, 0.987 and 0.999 in the training and validating sets, respectively).

CONCLUSIONS

A random forest algorithm predictive model based on the core genome allelic profiles of K. pneumoniae was accurate to identify the hypervirulent isolates.

Change of Hypermucoviscosity in the Development of Tigecycline Resistance in Hypervirulent Klebsiella pneumoniae Sequence Type 23 Strains

In this study, we developed tigecycline resistance in Klebsiella pneumoniae ST23 strains in vitro and investigated the change in virulence associated with hypermucoviscosity. In vitro-induced tigecycline-resistant (TGC-IR) K. pneumoniae mutants were obtained from three tigecycline-susceptible (TGC-S) strains, belonging to ST23 and serotype K1, by culturing in media with tigecycline in a stepwise manner. An antimicrobial susceptibility test, string test, mucoviscosity assay, and capsular polysaccharide (CPS) quantification were performed. Biofilm formation and serum resistance were evaluated, and survival rates of bacterial strains in fruit flies and macrophages were measured. Alterations of rpsJ, ramR, soxR, acrR, and marR genes were investigated and the expression levels of ramA and efflux pump genes were evaluated. The hypermucoviscosity phenotype was dramatically decreased in the TGC-IR mutants. Reduced CPS production in TGC-IR mutants was also identified. Increased resistance to most other antimicrobial agents was found in TGC-IR mutants. In addition, the TGC-IR mutants exhibited reduced biofilm formation, low serum resistance, and decreased survival rates within fruit flies and macrophages. Our study shows that development of tigecycline resistance in hypervirulent K. pneumoniae strains result in defects in virulence associated with hypermucoviscosity.

AmpR Increases the Virulence of Carbapenem-Resistant Klebsiella pneumoniae by Regulating the Initial Step of Capsule Synthesis

Background

Non-hypermucoviscous carbapenem-resistant Klebsiella pneumoniae with enhanced virulence lacking hvKP-specific virulence factors is uncommon, and the virulence mechanisms of this organism are not understood.

Methods

Following a retrospective study of carbapenem-resistant K. pneumoniae based on core genome multilocus sequence typing (cgMLST), isolates that caused high mortality were investigated with a genome-wide association study (GWAS), proteome analysis and an animal model.

Results

The subclone of sequence type 11 (ST11) K. pneumoniae, which belongs to complex type 3176 (CT3176) and K-locus 47 (KL47), was highlighted due to the high mortality of infected patients. GWAS analysis showed that transcriptional regulatory gene ampR was associated with the CT3176 isolates. In a mouse model, the mortality, bacterial load and pathological changes of mice infected with ampR-carrying isolates were distinct from those infected with ampR-null isolates. The ampR gene that enhances the virulence of the non-hypermucoviscous KL47 strain was unable to enhance the virulence of hypermucoviscous KL1 strain. Proteome analysis showed that the expression of WcaJ in the ampR⁺ isolates was significantly higher than that in the ampR⁻ isolates. Quantification of capsular polysaccharide confirmed that more capsule polysaccharide was produced by ampR⁺ and ampR-complementary strains compared to ampR⁻ strains. It is suggested that the enhancement of the initial stage of capsule synthesis may be the cause of the enhanced virulence of these non-hypermucoviscous ST11 carbapenem-resistant K. pneumoniae isolates.

Conclusion

Non-hypermucoviscous ST11 carbapenem-resistant K. pneumoniae with enhanced virulence warrants continued surveillance and investigation.

Endogenous endophthalmitis in Klebsiella pneumoniae pyogenic liver abscess: Systematic review and meta-analysis

BACKGROUND

Endogenous endophthalmitis (EE) is a devastating complication that develops as a metastatic infection in patients with Klebsiella pneumoniae pyogenic liver abscess (KPPLA). The existing data are heterogeneous and the actual disease burden and risk factors for the development of EE among patients with KPPLA have not been systematically examined. We performed a systematic review and meta-analysis to examine the incidence of EE, temporal trend of EE, and risk factors for EE in patients with KPPLA.

METHODOLOGY

The MEDLINE, EMBASE, Web of Science, and Cochrane Library databases were searched for articles published from inception to 2020 that evaluated the incidence of EE among patients with KPPLA. By a random-effects method, a pooled estimate of its incidence with 95% confidence intervals was estimated along with examination of its temporal and geographic variations. Pooled odds ratios were calculated for risk factors.

RESULTS

Fifteen retrospective studies reporting data on 11889 patients with KPPLA met the inclusion criteria and were analyzed. With 217 patients developing EE, the pooled incidence of EE was 4.5% (95% confidence interval 2.4% to 8.2%). The heterogeneity was considerable and significant (Cochran's Q 243.5, p < 0.001, I² = 94.2%).

CONCLUSION

This meta-analysis estimates the actual incidence of EE among patients with KPPLA, where EE is reported in about 1 of 22 patients with KPPLA. Infection caused by K1 capsular serotype was an independent risk factor.

Molecular Detection and PCR-RFLP Analysis of Mucoviscosity-Associated Gene A (magA) in Clinical Isolates of Multidrug-Resistant Klebsiella pneumoniae in Bangladesh

Background and Objective:

The mucoviscosity associated gene A (magA) in the hypermucoviscous variants of K. pneumoniae is reported to be associated with invasive infections and considered a virulence factor. We sought to analyze the magA genes in K. pneumoniae isolates in the clinical specimen collected from Bangladesh.

Methods:

We established a multicenter cohort of patients with Klebsiella infection hospitalized at 05 different hospitals between September 2016 and April 2017. We collected 313 K. pneumoniae isolates from patients who consented to participate in the study. The isolates were evaluated for harboring the magA genes using a single-tube multiplexed polymerase chain reaction. The magA genes were analyzed by PCR-RFLP technique using two enzymes, namely PciI and SmaI. Antibiogram assay using 12 commercially available antibiotic discs was performed on all the isolates.

Results:

The presence of K. pneumoniae specific gene (ureD) was confirmed in all the isolates. The percentage of isolates harboring the magA gene was 7.34%(23 isolates), the majority of which was collected from the patients admitted in intensive care units (16 isolates, 69.6%), and infectious diseases wards (5 isolates, 21.7%). PCR-RFLP analysis revealed that for 7 out of 23 isolates, where Sma1 could not cleave the magA gene. All the isolates showed resistance to ampicillin, carbenicillin cefradine, chloramphenicol, erythromycin, kanamycin, and sulphamethoxazole, though the extent was varying. However, imipenem showed 100% sensitivity to all the tested isolates.

Conclusion:

This study demonstrates the presence of the magA gene in multidrug-resistant clinical isolates of K. pneumoniae collected from Bangladesh.

A retrospective study of pyogenic liver abscess caused primarily by Klebsiella pneumoniae vs. non-Klebsiella pneumoniae: CT and clinical differentiation

PURPOSE

The incidence of Klebsiella pneumoniae pyogenic liver abscesses (KP-PLA) is increasing. However, its diagnosis and treatment are often delayed, leading to complications. In this study, we aimed to retrospectively compare computed tomographic (CT) features of KP-PLAs with those of abscesses caused by other bacterial pathogens (non-KP-PLAS) and to further identify prognostic factors for PLA.

METHODS

Data of 219 study patients including clinical presentation, comorbid conditions, metastatic infection, treatment duration, and mortality were retrospectively collated. CT characteristics of abscesses were recorded. Etiology was established by pus and/or blood culture. The differentiating CT features and clinical findings were compared between the monomicrobial KP-PLA and non-KP-PLA groups. Furthermore, factors related to in-hospital case fatality were analyzed.

RESULTS

Multivariate analysis identified thin-walled abscesses, absent rim enhancement, metastatic infection, and absence of underlying biliary tract disease as significant predictors of KP-PLA. With 3/4 criteria applied in combination, a specificity of 96.5% was achieved for KP-PLA diagnosis. The in-hospital mortality rate was 3.7%. Multivariate analysis revealed that diabetes mellitus (P = 0.031), multiple abscesses (P = 0.026), internal gas bubble (P = 0.041), metastatic infection (P = 0.004), and septic shock (P = 0.002) were significantly associated with mortality.

CONCLUSION

Thin-walled abscess, metastatic infection, absence of rim enhancement, and absence of underlying biliary tract disease are potentially useful CT findings for early KP-PLA diagnosis.

Fluoroquinolones as an alternative treatment for Klebsiella pneumoniae liver abscess and impact on hospital length of stay

Klebsiella pneumoniae liver abscess (KPLA) is an endemic disease in East Asia. Patients with KPLA usually require prolonged intravenous (i.v.) β-lactam therapy and hospitalisation. Fluoroquinolones have high oral bioavailability and the potential to shorten the duration of i.v. therapy. The aim of this study was to investigate the feasibility of fluoroquinolones as an alternative treatment for KPLA in Taiwan. Consecutive patients with KPLA in a medical centre in Taiwan between July 2012 and August 2019 were retrospectively enrolled. Clinical characteristics and outcomes were compared between cases treated with β-lactams and fluoroquinolones. A multivariate logistic regression model and propensity-score adjusted analysis were performed to identify independent risk factors for prolonged hospitalisation. A total of 234 patients with KPLA were identified during the study period. Most patients received β-lactams (n = 199; 85.0%), whilst only 35 (15.0%) received fluoroquinolones as the major therapy. Fluoroquinolones had similar clinical efficacy to β-lactams even in critically ill patients. Patients treated with fluoroquinolones had a shorter i.v. antibiotics duration (18.9 ± 7.6 days vs. 28.5 ± 14.7 days; P < 0.001) and hospital length of stay (LOS) (20.9 ± 8.3 days vs. 29.5 ± 16.2 days; P < 0.001) than patients treated with β-lactams. Major therapy with fluoroquinolones was an independent protective factor for hospital LOS > 14 days in all patients and for hospital LOS > 21 days in critically ill patients. In conclusion, fluoroquinolones were an effective alternative treatment for KPLA that resulted in a shorter duration of i.v. therapy and hospital LOS.