Community-acquired Klebsiella pneumoniae bacteremia: global differences in clinical patterns

Bloodstream Coinfections and Antimicrobial Resistance in Hospitalized COVID-19 Patients: A Single-center Retrospective Study

BACKGROUND/AIM

Bloodstream infections in patients with COVID-19 are linked to higher mortality rates, whilst data on epidemiology and resistance patterns remains scarce to guide management and prevent antibiotic resistance. This research focuses on the prevalence, clinical features, causative microorganisms, and antimicrobial susceptibility of bacterial and fungal secondary bloodstream co-infections in hospitalized patients with COVID-19.

PATIENTS AND METHODS

In this retrospective study analysis of 230 patients with COVID-19 from Central Taiwan (June 2021 to June 2022), pathogens were identified via MALDI-TOF MS and Vitek 2 system with Clinical & Laboratory Standards Institute (CLSI) standards.

RESULTS

In the cohort, 17.8% experienced bloodstream infections, resulting in a total of 45 isolates from the 41 bloodstream infection patients: predominantly gram-positive bacteria (Staphylococcus and Enterococcus) at 69%, gram-negative at 29% (Escherichia coli and Klebsiella pneumoniae), and fungi at 2%. Infected patients showed significantly elevated levels of white blood count (WBC), C-reactive protein (CRP) and procalcitonin (PCT). Of note, resistance to common antibiotics, such as fluoroquinolones, cephalosporins, and oxacillin was significant, especially in K. pneumoniae, Acinetobacter species, and S. aureus infections.

CONCLUSION

Our study highlights the influence of bacterial infections in hospitalized patients with COVID-19. The bacterial infections were discovered to impact the clinical trajectory of COVID-19, potentially exacerbating or mitigating its symptoms, severity and fatality. These insights are pivotal to addressing clinical challenges in COVID-19 management and underscoring the need for tailored medical interventions. Understanding these co-infections is thus essential for optimizing patient care and improving overall outcomes in the post COVID-19 pandemic era.

Hypervirulent Klebsiella pneumoniae in a South African tertiary hospital-Clinical profile, genetic determinants, and virulence in Caenorhabditis elegans

Introduction

A distinct strain of Klebsiella pneumoniae (K. pneumoniae) referred to as hypervirulent (hvKp) is associated with invasive infections such as pyogenic liver abscess in young and healthy individuals. In South Africa, limited information about the prevalence and virulence of this hvKp strain is available. The aim of this study was to determine the prevalence of hvKp and virulence-associated factors in K. pneumoniae isolates from one of the largest tertiary hospitals in a South African province.

Methods

A total of 74 K. pneumoniae isolates were received from Pelonomi Tertiary Hospital National Health Laboratory Service (NHLS), Bloemfontein. Virulence-associated genes (rmpA, capsule serotype K1/K2, iroB and irp2) were screened using Polymerase Chain Reaction (PCR). The iutA (aerobactin transporter) gene was used as a primary biomarker of hvKp. The extracted DNAs were sequenced using the next-generation sequencing pipeline and the curated sequences were used for phylogeny analyses using appropriate bioinformatic tools. The virulence of hvKp vs. classical Klebsiella pneumoniae (cKp) was investigated using the Caenorhabditis elegans nematode model.

Results

Nine (12.2%) isolates were identified as hvKp. Moreover, hvKp was significantly (p < 0.05) more virulent in vivo in Caenorhabditis elegans relative to cKp. The virulence-associated genes [rmpA, iroB, hypermucoviscous phenotype (hmv) phenotype and capsule K1/K2] were significantly (p < 0.05) associated with hvKp. A homology search of the curated sequences revealed a high percentage of identity between 99.8 and 100% with other homologous iutA gene sequences of other hvKp in the GenBank.

Conclusion

Findings from this study confirm the presence of hvKp in a large tertiary hospital in central South Africa. However, the low prevalence and mild to moderate clinical presentation of infected patients suggest a marginal threat to public health. Further studies in different settings are required to establish the true potential impact of hvKp in developing countries.

[Effect of intestinal nitrate on growth of Klebsiella pneumoniae and its regulatory mechanism]

OBJECTIVE

To explore the effect of intestinal nitrates on the growth of Klebsiella pneumoniae and its regulatory mechanisms.

METHODS

K. pneumoniae strains with nitrate reductase narG and narZ single or double gene knockout or with NarXL gene knockout were constructed and observed for both aerobic and anaerobic growth in the presence of KNO3 using an automated bacterial growth analyzer and a spectrophotometer, respectively. The mRNA expressions of narG and narZ in K. pneumoniae in anaerobic cultures in the presence of KNO3 and the effect of the binary regulatory system NarXL on their expresisons were detected using qRT-PCR. Electrophoretic mobility shift assays (EMSA) and MST analysis were performed to explore the specific regulatory mechanisms of NarXL in sensing and utilizing nitrates. Competitive experiments were conducted to examine anaerobic growth advantages of narG and narZ gene knockout strains of K. pneumoniae in the presence of KNO3.

RESULTS

The presence of KNO3 in anaerobic conditions, but not in aerobic conditions, promoted bacterial growth more effectively in the wild-type K. pneumoniae strain than in the narXL gene knockout strain. In anaerobic conditions, the narXL gene knockout strain showed significantly lowered mRNA expressions of narG and narZ (P < 0.0001). EMSA and MST experiments demonstrated that the NarXL regulator could directly bind to narG and narZ promoter regions. The wild-type K. pneumoniae strain in anaerobic cultures showed significantly increased expressions of narG and narZ mRNAs in the presence of KNO3 (P < 0.01), and narG gene knockout resulted in significantly attenuated anaerobic growth and competitive growth abilities of K. pneumoniae in the presence of KNO3 (P < 0.01).

CONCLUSION

The binary regulatory system NarXL of K. pneumoniae can sense changes in intestinal nitrate concentration and directly regulate the expression of nitrate reductase genes narG and narZ to promote bacterial growth.

Prognosis and Characteristics of Hypermucoviscous Klebsiella pneumoniae Infection in Critically Ill Patients: A Case Series

Introduction Hypermucoviscous Klebsiella pneumoniae (hvKP) is related to invasive infections; however, there have been very few comprehensive reports on the clinical features and prognosis of critically ill patients with the infection. Methods We conducted a retrospective case series in a general intensive care unit in Japan. Patients with positive blood cultures for KP between January 1, 2020 and December 31, 2022 were included. hvKP was defined by the positivity in the string test. We analyzed the patient's characteristics at baseline, including comorbidities, abscess formation, Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) II score, septic shock, duration of hospitalization, 30-day mortality, and infection site. Results A total of 24 patients had a positive blood culture for KP; nine patients (37.5%) were positive for the string test (hvKP) while 15 (62.5%) were negative (non-hvKP). In both groups, the patients were old (mean age, hvKP 80.4 vs. non-hvKP 75.7 years) and more often male (five patients (55.6%) vs. 12 patients (80.0%)). No statistically significant difference was found between the two groups in terms of comorbidities, such as diabetes mellitus, chronic obstructive pulmonary disease, chronic kidney disease, and malignancy. No statistical difference was seen in abscess formation (two patients [22.2%] vs. one patient (6.7%)), SOFA score (5.2±4.8 vs. 4.7±3.4), APACHE II score (19.6 (15.0-20.0) vs. 17.0 (11.2-20.8)), septic shock (five patients (55.6%) vs. four patient (26.7%)), duration of hospitalization (37.2 (12.0-51.0) vs. 32.3 (9.5-21.0)), and 30-day mortality (two patients (22.2%) vs. two patients (13.3%)). Two cases with hvKP died within 24 h. No significant difference was seen in the infection sources; respiratory infection (2 (22.2%) vs. 1 (6.7%)), hepatobiliary infection (2 (22.2%) vs. 7 (46.7%)), and genitourinary infection (1 (11.1%) vs. 5 (33.3%)). Conclusions Critically ill patients with hvKP infection showed characteristics similar to those reported previously. However, the disease could rapidly become severe and have a poor prognostic outcome.

Analysis of virulence profiles in clinical isolates of Klebsiella pneumoniae from renal abscesses: clinical significance of hypervirulent isolates

Introduction

Klebsiella pneumoniae can cause a wide range of infections. Hypervirulent K. pneumoniae (hvKp), particularly associated with the K1 and K2 capsular types, is an increasingly significant microorganism with the potential to cause invasive infections, including renal abscesses. Despite the rising prevalence of hvKp infections, information on renal abscesses caused by K. pneumoniae is limited, and the clinical significance of hvKp associated with specific virulence genes remains elusive.

Methods

This study performed at a 1200-bed tertiary hospital sought to identify the clinical and microbiological characteristics of renal abscesses caused by K. pneumoniae, focusing on various virulence genes, including capsular serotypes and multilocus sequence typing (MLST).

Results

Over an 8-year period, 64 patients with suspected renal abscesses were reviewed. Ten patients diagnosed with K. pneumoniae-related renal abscesses were ultimately enrolled in the study. Among the isolates from the 10 patients, capsular serotype K2 was predominant (40.0%), followed by K1 (30.0%). The most common sequence type by MLST was 23 (40.0%). In particular, six patients (60.0%) harbored specific genes indicative of hvKp: iucA, peg-344, rmpA, and rmpA2.

Conclusions

Our findings highlight the importance of hvKp as a pathogen in renal abscesses. Although the nature of hvKp is relatively unknown, it is widely recognized as a highly virulent pathogen that can infect relatively healthy individuals of various ages and simultaneously cause infections at multiple anatomical sites. Therefore, when treating patients with K. pneumoniae-related renal abscesses, caution is necessary when considering the characteristics of hvKp, such as potential bacteremia, multi-organ abscess formation, and metastatic spread.

Insights into the preventive actions of natural compounds against Klebsiella pneumoniae infections and drug resistance

Klebsiella pneumoniae is a type of Gram-negative bacteria that causes a variety of infections, including pneumonia, bloodstream infections, wound infections, and meningitis. The treatment of K. pneumoniae infection depends on the type of infection and the severity of the symptoms. Antibiotics are generally used to treat K. pneumoniae infections. However, some strains of K. pneumoniae have become resistant to antibiotics. This comprehensive review examines the potential of natural compounds as effective strategies against K. pneumonia infections. The alarming rise in antibiotic resistance underscores the urgent need for alternative therapies. This article represents current research on the effects of diverse natural compounds, highlighting their anti-microbial and antibiofilm properties against K. pneumonia. Notably, compounds such as andrographolide, artemisinin, baicalin, berberine, curcumin, epigallocatechin gallate, eugenol, mangiferin, piperine, quercetin, resveratrol, and thymol have been extensively investigated. These compounds exhibit multifaceted mechanisms, including disruption of bacterial biofilms, interference with virulence factors, and augmentation of antibiotic effectiveness. Mechanistic insights into their actions include membrane perturbation, oxidative stress induction, and altered gene expression. While promising, challenges such as limited bioavailability and varied efficacy across bacterial strains are addressed. This review further discusses the potential of natural compounds as better alternatives in combating K. pneumonia infection and emphasizes the need for continued research to harness their full therapeutic potential. As antibiotic resistance persists, these natural compounds offer a promising avenue in the fight against K. pneumonia and other multidrug-resistant pathogens.

Antibiotic resistance: a global crisis, problems and solutions

Healthy state is priority in today's world which can be achieved using effective medicines. But due to overuse and misuse of antibiotics, a menace of resistance has increased in pathogenic microbes. World Health Organization (WHO) has announced ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) as the top priority pathogens as these have developed resistance against certain antibiotics. To combat such a global issue, it is utmost important to identify novel therapeutic strategies/agents as an alternate to such antibiotics. To name certain antibiotic adjuvants including: inhibitors of beta-lactamase, efflux pumps and permeabilizers for outer membrane can potentially solve the antibiotic resistance problems. In this regard, inhibitors of lytic domain of lytic transglycosylases provide a novel way to not only act as an alternate to antibiotics but also capable of restoring the efficiency of previously resistant antibiotics. Further, use of bacteriophages is another promising strategy to deal with antibiotic resistant pathogens. Taking in consideration the alternatives of antibiotics, a green synthesis nanoparticle-based therapy exemplifies a good option to combat microbial resistance. As horizontal gene transfer (HGT) in bacteria facilitates the evolution of new resistance strains, therefore identifying the mechanism of resistance and development of inhibitors against it can be a novel approach to combat such problems. In our perspective, host-directed therapy (HDT) represents another promising strategy in combating antimicrobial resistance (AMR). This approach involves targeting specific factors within host cells that pathogens rely on for their survival, either through replication or persistence. As many new drugs are under clinical trials it is advisable that more clinical data and antimicrobial stewardship programs should be conducted to fully assess the clinical efficacy and safety of new therapeutic agents.

Child deaths caused by Klebsiella pneumoniae in sub-Saharan Africa and south Asia: a secondary analysis of Child Health and Mortality Prevention Surveillance (CHAMPS) data

BACKGROUND

Klebsiella pneumoniae is an important cause of nosocomial and community-acquired pneumonia and sepsis in children, and antibiotic-resistant K pneumoniae is a growing public health threat. We aimed to characterise child mortality associated with this pathogen in seven high-mortality settings.

METHODS

We analysed Child Health and Mortality Prevention Surveillance (CHAMPS) data on the causes of deaths in children younger than 5 years and stillbirths in sites located in seven countries across sub-Saharan Africa (Ethiopia, Kenya, Mali, Mozambique, Sierra Leone, and South Africa) and south Asia (Bangladesh) from Dec 9, 2016, to Dec 31, 2021. CHAMPS sites conduct active surveillance for deaths in catchment populations and following reporting of an eligible death or stillbirth seek consent for minimally invasive tissue sampling followed by extensive aetiological testing (microbiological, molecular, and pathological); cases are reviewed by expert panels to assign immediate, intermediate, and underlying causes of death. We reported on susceptibility to antibiotics for which at least 30 isolates had been tested, and excluded data on antibiotics for which susceptibility testing is not recommended for Klebsiella spp due to lack of clinical activity (eg, penicillin and ampicillin).

FINDINGS

Among 2352 child deaths with cause of death assigned, 497 (21%, 95% CI 20-23) had K pneumoniae in the causal chain of death; 100 (20%, 17-24) had K pneumoniae as the underlying cause. The frequency of K pneumoniae in the causal chain was highest in children aged 1-11 months (30%, 95% CI 26-34; 144 of 485 deaths) and 12-23 months (28%, 22-34; 63 of 225 deaths); frequency by site ranged from 6% (95% CI 3-11; 11 of 184 deaths) in Bangladesh to 52% (44-61; 71 of 136 deaths) in Ethiopia. K pneumoniae was in the causal chain for 450 (22%, 95% CI 20-24) of 2023 deaths that occurred in health facilities and 47 (14%, 11-19) of 329 deaths in the community. The most common clinical syndromes among deaths with K pneumoniae in the causal chain were sepsis (44%, 95% CI 40-49; 221 of 2352 deaths), sepsis in conjunction with pneumonia (19%, 16-23; 94 of 2352 deaths), and pneumonia (16%, 13-20; 80 of 2352 deaths). Among K pneumoniae isolates tested, 121 (84%) of 144 were resistant to ceftriaxone and 80 (75%) of 106 to gentamicin.

INTERPRETATION

K pneumoniae substantially contributed to deaths in the first 2 years of life across multiple high-mortality settings, and resistance to antibiotics used for sepsis treatment was common. Improved strategies are needed to rapidly identify and appropriately treat children who might be infected with this pathogen. These data suggest a potential impact of developing and using effective K pneumoniae vaccines in reducing neonatal, infant, and child deaths globally.

FUNDING

Bill & Melinda Gates Foundation.

Involvement of Tn3 transposon in formation and transmission of hypervirulent and carbapenem-resistant Klebsiella pneumoniae

IMPORTANCE

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is resistant to most common antibiotics, becoming the most important and prevalent nosocomial opportunity pathogen. Besides, K. pneumoniae can also cause severe community-acquired infections, such as primary liver abscess and endophthalmitis. These pathogens are commonly referred to as hvKp. CRKP and hvKp have evolved separately, each occupying its own clonal lineage and exhibiting a variety of properties. Our study provides important insights into the evolutionary events related to the arousal of virulence and drug resistance in K. pneumoniae through plasmid transmission, mediated by Tn3 transposon. Our study also provides evidence that multiple mechanisms contribute to the successful transfer of non-conjugative virulence plasmid, and the involvement of transposons enhances the efficiency. A good knowledge of its transmission mechanisms is fundamental to finding effective strategies to combat these threatening pathogens. Transposons are widely present in bacteria, spreading resistance and virulence genes between the environment and humans. Therefore, emerging transposon-mediated hypervirulent and carbapenem-resistant pathogens should be highly valued.

The clinical characteristics and therapeutic outcomes of adult patients with community-acquired spontaneous bacterial meningitis with a fulminant clinical course in Taiwan

PURPOSE

To examine the clinical characteristics of adult patients with community-acquired spontaneous bacterial meningitis (CASBM) with a fulminant clinical course.

MATERIALS AND METHODS

The clinical features and therapeutic outcomes of 127 adult CASBM patients were analyzed. The patients were divided into two groups as those with and without a fulminant clinical course. Fulminant clinical course was defined as meningitis presenting initially with marked consciousness disturbance (Glasgow Coma Scale score < 8) or a rapid deterioration in consciousness level within 48 h of hospitalization.

RESULTS

Among the 127 enrolled patients, 69 had a fulminant clinical course (47 men and 22 women) and 58 did not. The patients with a fulminant clinical course had a significantly higher incidence of end-stage renal disease (ESRD), severe clinical manifestations and higher mortality rate, and the survivors had significantly worse therapeutic outcomes. Klebsiella (K.) pneumoniae (50 strains) was the most important pathogen for the development of a fulminant clinical course, and all strains were susceptible to ceftriaxone and ceftazidime. With treatment, 50.7% (35/69) of the patients with a fulminant clinical course died, and the presence of K. pneumoniae infection was significant prognostic factor.

CONCLUSIONS

The presence of ESRD, initial presentation of altered consciousness, septic shock, seizures and CSF total protein level and K. pneumoniae infection were significantly associated with a fulminant clinical course of adult CASBM, and patients with this specific infectious syndrome had high mortality and morbidity rates. The presence of K. pneumoniae infection is a significant prognostic factor.

Evaluation of virulence of Klebsiella pneumoniae using zebrafish behavior as a biological indicator

INTRODUCTION

Klebsiella pneumoniae is one of the common pathogenic bacteria that can cause infections in hospitals and communities and can cause respiratory, urinary, and other multi-system infections. In recent years, the emergence of highly virulent and drug-resistant Klebsiella pneumoniae has greatly increased the difficulty of treatment for infection. Clinically, it is very important to accurately judge the virulence of isolated Klebsiella pneumoniae for treatment, but there is no better method to evaluate its virulence.

METHODS

In this study, zebrafish were used as a model organism, and the swimming distance was used as a detection index to identify clinically isolated Klebsiella pneumoniae. In this study, we selected two different strains of Klebsiella pneumoniae, i.e., NTUH-K2044 and ATCC BAA-1705, with known high and low virulence, respectively, to infect zebrafish juveniles and evaluated their behavioral ability according to different bacterial concentrations and different developmental times.

RESULTS

It was found that highly virulent Klebsiella pneumoniae caused a significant decrease in the behavioral ability of zebrafish larvae, while low-virulence Klebsiella pneumoniae had relatively little effect.

CONCLUSIONS

These results indicate that it is entirely feasible to assess the virulence of Klebsiella pneumoniae based on behavioral ability.

Klebsiella pneumoniae bacteraemia epidemiology: resistance profiles and clinical outcome of King Fahad Medical City isolates, Riyadh, Saudi Arabia

BACKGROUND AND OBJECTIVES

Klebsiella pneumoniae (K. pneumoniae) is the second leading cause of community-acquired and hospital-acquired gram-negative bloodstream infection (BSI). This study aimed to assess the epidemiological and microbial-resistance characteristics and clinical factors associated with K. pneumoniae BSI in Saudi Arabia.

MATERIALS AND METHODS

Data of 152 K. pneumoniae isolates diagnosed between January 2019 and January 2020 at King Fahad Medical City, Riyadh, Saudi Arabia were evaluated retrospectively. Clinical records of the patients were collected and analysed statistically.

RESULTS

In total, 152 cases of K. pneumoniae BSI were identified. Adult patients (66.4%) were at a higher risk of developing the infection than paediatric patients (33.6%). The rate of infection was slightly higher in women than in men. Neurological disorders were the predominant underlying conditions for the acquisition of K. pneumoniae BSI, at all ages. Most of the deceased patients were adults with multi-organ dysfunction. Klebsiella pneumoniae showed disturbing resistance to amoxicillin-clavulanate and cefuroxime (72.4%), ceftazidime (67.8), cephalothin (76.3%), and to Carbapenems (36.1%).

CONCLUSIONS

The impact of K. pneumoniae BSI was seen not only at the patient level, but also at the community level, and was related to multi-drug resistant infection. These findings provide a better understanding of microbial resistance and its association with patient clinical outcomes.

Characterization and biocontrol efficacy of lytic phage (KPP-1) that infects multidrug resistant Klebsiella variicola

Klebsiella variicola strain was identified from a natural water stream. Novel phage (KPP-1) infecting K. variicola was isolated and characterized. The biocontrol efficacy of KPP-1 against K. variicola-infected adult zebrafish was also investigated. The host K. variicola strain was resistant to six of the antibiotics tested and comprised the virulence genes kfuBC, fim, ureA, and Wza-Wzb-Wzccps. Morphological analysis by transmission electron microscopy revealed that KPP-1 has icosahedron head and tail structures. The latent period and burst size of KPP-1 were 20 min and 88 PFU per infected cell, respectively, at a multiplicity of infection of 0.1. KPP-1 was stable over a broad pH range (3-11), temperature (4-50 °C), and salinity (0.1-3%). KPP-1 inhibits the growth of K. variicola in vitro and in vivo. In the zebrafish infection model, treatment with KPP-1-infected K. variicola demonstrated 56% of cumulative survival. This suggests the possibility of developing KPP-1 as a potential biocontrol agent against multidrug-resistant K. variicola that belongs to the K. pneumoniae complex.

Invasive Klebsiella rhinoscleromatis infection leading to ARDS, septic shock, and death: A rare case report

Rhinoscleroma is an uncommon chronic infection caused by Klebsiella rhinoscleromatis, a gram-negative bacillus that affects the upper respiratory tract. Although the nasal cavity is the most affected area, pulmonary involvement has not been previously documented. This case report describes a 61-year-old man followed for nasal rhinoscleroma who was admitted to the intensive care unit with acute respiratory distress and septic shock due to bilateral infectious bronchopneumonia. Despite immediate intubation and intravenous antibacterial treatment, the patient died 10 days later. Klebsiella rhinoscleromatis was identified in a distal pulmonary swab and blood culture. While cases of rhinoscleroma and bacteremia caused by K rhinoscleromatis infection have been documented, the case we present here is the first to report on acute respiratory distress syndrome caused by fulminant pneumonia along with septic shock.

Concurrent bacterial liver abscess and mild encephalitis/encephalopathy with reversible splenial lesion in a patient with poorly controlled type 2 diabetes

A 34-year-old man with poorly controlled type 2 diabetes was admitted to our hospital because of fever, headache, vomiting, and impaired consciousness. His hemoglobin A1c level was as high as 11.0%. Abdominal computed tomography revealed a bacterial liver abscess, while head magnetic resonance imaging simultaneously showed a high-signal lesion on diffusion-weighted imaging and a low-signal lesion on the apparent diffusion coefficient map of the splenium of the corpus callosum. No significant findings were detected in the cerebrospinal fluid. The latter findings led to a diagnosis of mild encephalitis/encephalopathy with reversible splenial lesions. His impaired consciousness resolved on Day 5 after treatment with ceftriaxone and metronidazole infusion and intensive insulin therapy; magnetic resonance imaging on Day 20 showed that the lesion in the splenium of the corpus callosum had disappeared. We propose that when a person with poorly controlled diabetes develops a bacterial infection and presents with impaired consciousness and headache, clinicians should consider the complications of mild encephalitis/encephalopathy with reversible splenial lesion.

Klebsiella pneumoniae invasive syndrome with liver abscess and purulent meningitis presenting as acute hemiplegia: a case report

BACKGROUND

Klebsiella pneumoniae can infect a variety of sites, with the risk of infection being higher in the immunocompromised state such as diabetes mellitus. A distinct invasive syndrome has been detected mostly in Southeast Asia in the past two decades. A common destructive complication is pyogenic liver abscess that can be complicated by metastatic endophthalmitis as well as the involvement of the central nervous system, causing purulent meningitis or brain abscess.

CASE PRESENTATION

We report a rare case of an invasive liver abscess caused by K. pneumoniae, with metastatic infections of meninges. A 68-year-old man with type 2 diabetes mellitus presented to our emergency department as sepsis. Sudden disturbed consciousness was noticed with presentation of acute hemiplegia and gaze preference mimicking a cerebrovascular accident.

CONCLUSIONS

The above case adds to the scarce literature on K. pneumoniae invasive syndrome with liver abscess and purulent meningitis. K. pneumoniae is a rare cause of meningitis and should raise suspicions about the disease in febrile individuals. In particular, Asian patients with diabetes presenting with sepsis and hemiplegia prompt a more thorough evaluation with aggressive treatment.

Hematogenous prosthetic knee joint infection with Klebsiella pneumoniae caused by asymptomatic gallbladder abscess: a case report and literature review

Klebsiella pneumoniae has the ability to form biofilm; therefore, the treatment of prosthetic joint infection involving K. pneumoniae is often challenging. This report describes the first case of acute hematogenous prosthetic knee joint infection with K. pneumoniae that occurred as a result of an asymptomatic gallbladder abscess. The patient was a 78-year-old man who underwent bilateral total knee arthroplasty 6 years ago. He had pain and swelling in his right knee. The synovial fluid culture of the right knee revealed K. pneumoniae and prosthetic joint infection was diagnosed. Computed tomography revealed a gallbladder abscess in the absence of right upper abdominal pain. The patient underwent simultaneous debridement of the knee and open cholecystectomy. The treatment was successful and the prosthesis was retained. In cases of hematogenous prosthetic joint infection with K. pneumoniae, other sources of infection should be suspected and investigated regardless of whether they are symptomatic.

Identification of three capsule depolymerases in a bacteriophage infecting Klebsiella pneumoniae capsular types K7, K20, and K27 and therapeutic application

BACKGROUND

Klebsiella pneumoniae capsular types K1, K2, K5, K20, K54, and K57 are prevalent hypervirulent types associated with community infections, and worrisomely, hypervirulent strains that acquired drug resistance have been found. In the search for alternative therapeutics, studies have been conducted on phages that infect K. pneumoniae K1, K2, K5, and K57-type strains and their phage-encoded depolymerases. However, phages targeting K. pneumoniae K20-type strains and capsule depolymerases capable of digesting K20-type capsules have rarely been reported. In this study, we characterized a phage that can infect K. pneumoniae K20-type strains, phage vB_KpnM-20.

METHODS

A phage was isolated from sewage water in Taipei, Taiwan, its genome was analyzed, and its predicted capsule depolymerases were expressed and purified. The host specificity and capsule-digesting activity of the capsule depolymerases were determined. The therapeutic effect of the depolymerase targeting K. pneumoniae K20-type strains was analyzed in a mouse infection model.

RESULTS

The isolated Klebsiella phage, vB_KpnM-20, infects K. pneumoniae K7, K20, and K27-type strains. Three capsule depolymerases, K7dep, K20dep, and K27dep, encoded by the phage were specific to K7, K20, and K27-type capsules, respectively. K20dep also recognized Escherichia coli K30-type capsule, which is highly similar to K. pneumoniae K20-type. The survival of K. pneumoniae K20-type-infected mice was increased following administration of K20dep.

CONCLUSIONS

The potential of capsule depolymerase K20dep for the treatment of K. pneumoniae infections was revealed using an in vivo infection model. In addition, K7dep, K20dep, and K27dep capsule depolymerases could be used for K. pneumoniae capsular typing.

Antimicrobial Resistance Pattern, Pathogenicity and Molecular Properties of Hypervirulent Klebsiella pneumonia (hvKp) among Hospital-Acquired Infections in the Intensive Care Unit (ICU)

Hypervirulent Klebsiella pneumoniae (hvKp) is a new emerging variant of K. pneumoniae that is increasingly reported worldwide. The variant hvKp is known to cause severe invasive community-acquired infections such as metastatic meningitis, pyogenic liver abscesses (PLA) and endophthalmitis, but its role in hospital-acquired infections (HAIs) is little known. The aim of this study was to evaluate the prevalence of hvKp among hospital-acquired (HA) K. pneumoniae infections in the intensive care unit (ICU) and to compare between hvKp and classical K. pneumoniae (cKP) regarding antimicrobial resistance pattern, virulence and molecular characteristics. The study was cross-sectional and included 120 ICU patients suffering from HA K. pneumoniae infections between January and September 2022. K. pneumoniae isolates were subjected to antimicrobial susceptibility testing and detection of extended-spectrum-β-lactamase (ESBL) production by the Phoenix 100 automated microbiology system, string test, biofilm formation, serum resistance assay, and detection of virulence-associated genes (rmpA, rmpA2, magA, iucA) and capsular serotype-specific genes (K1, K2, K5, K20, K57) by polymerase chain reaction (PCR). Of 120 K. pneumoniae isolates, 19 (15.8%) were hvKp. The hypermucoviscous phenotype was more significantly detected in the hvKp group than in the cKP group (100% vs. 7.9%, p ≤ 0.001). The rate of resistance to different antimicrobial agents was significantly higher in the cKP group than that in the hvKp group. Fifty-three strains were identified as ESBL-producing strains, which was more frequent in the cKP group than in the hvKp group (48/101 [47.5%] vs. 5/19 [26.3%], respectively, p ≤ 0.001). The hvKP isolates were highly associated with moderate and strong biofilm formation than cKP isolates (p = 0.018 and p = 0.043 respectively). Moreover, the hvKP isolates were highly associated with intermediate sensitivity and re sistance to serum in the serum resistance assay (p = 0.043 and p = 0.016 respectively). K1, K2, rmpA, rmpA2, magA and iucA genes were significantly associated with hvKp (p ≤ 0.001, 0.004, <0.001, <0.001, 0.037 and <0.001, respectively). However, K5, K20 and K57 were not associated with hvKp. The hvKp strains have emerged as a new threat to ICU patients because of their ability to cause more severe and life-threatening infections than cKP. The string test alone as a laboratory test for screening of hvKp has become insufficient. Recently, hvKp was defined as hypermucoviscous- and aerobactin-positive. It is important to improve the awareness towards the diagnosis and management of hvKp infections.

Improvement and Validation of a Multi-Locus Variable Number of Tandem Repeats Analysis (MLVA8+) for Klebsiella pneumoniae, Klebsiella variicola, and Klebsiella quasipneumoniae

The genotyping of the multidrug-resistant Klebsiella pneumoniae species complex is essential to identify outbreaks and to track their source and spread. The aim of this study was to improve and extend the typeability, availability, cost and time efficiency of an existing multi-locus VNTR analysis (MLVA). A modified scheme (MLVA8+) was adopted and validated for strain-level differentiation of the three Klebsiella species involved in human pathology. A diverse set of 465 K. pneumoniae clinical isolates from 22 hospitals and 3 outpatient laboratories in Bulgaria were studied, where 315 were carbapenem-resistant. The MLVA8+ typeability was significantly improved and the typing data were validated against 158 isolates which were previously typed by WGS. The MLVA8+ results were highly concordant with the classic 7-locus MLST and the novel K. variicola MLST, but had greater congruency coefficients (adjusted Wallace). A major advantage was the differentiation of the hybrid cluster ST258 into its corresponding clades. Furthermore, the applicability of MLVA8+ was demonstrated by conducting a retrospective investigation of the intra-hospital spread of blaKPC-, blaNDM- and blaOXA-48-like producers. The MLVA8+ has improved utility and extended typing scope to K. variicola and K. quasipneumoniae, while its cost and time-to-result were reduced.

Characterization and comprehensive genome analysis of novel bacteriophage, vB_Kpn_ZCKp20p, with lytic and anti-biofilm potential against clinical multidrug-resistant Klebsiella pneumoniae

Introduction

The rise of infections by antibiotic-resistant bacterial pathogens is alarming. Among these, Klebsiella pneumoniae is a leading cause of death by hospital-acquired infections, and its multidrug-resistant strains are flagged as a global threat to human health, which necessitates finding novel antibiotics or alternative therapies. One promising therapeutic alternative is the use of virulent bacteriophages, which specifically target bacteria and coevolve with them to overcome potential resistance. Here, we aimed to discover specific bacteriophages with therapeutic potential against multiresistant K. pneumoniae clinical isolates.

Methods and Results

Out of six bacteriophages that we isolated from urban and medical sewage, phage vB_Kpn_ZCKp20p had the broadest host range and was thus characterized in detail. Transmission electron microscopy suggests vB_Kpn_ZCKp20p to be a tailed phage of the siphoviral morphotype. In vitro evaluation indicated a high lytic efficiency (30 min latent period and burst size of ∼100 PFU/cell), and extended stability at temperatures up to 70°C and a wide range of (2-12) pH. Additionally, phage vB_Kpn_ZCKp20p possesses antibiofilm activity that was evaluated by the crystal violet assay and was not cytotoxic to human skin fibroblasts. The whole genome was sequenced and annotated, uncovering one tRNA gene and 33 genes encoding proteins with assigned functions out of 85 predicted genes. Furthermore, comparative genomics and phylogenetic analysis suggest that vB_Kpn_ZCKp20p most likely represents a new species, but belongs to the same genus as Klebsiella phages ZCKP8 and 6691. Comprehensive genomic and bioinformatics analyses substantiate the safety of the phage and its strictly lytic lifestyle.

Conclusion

Phage vB_Kpn_ZCKp20p is a novel phage with potential to be used against biofilm-forming K. pneumoniae and could be a promising source for antibacterial and antibiofilm products, which will be individually studied experimentally in future studies.

Recent Advances in Nanotechnology for the Management of Klebsiella pneumoniae-Related Infections

Klebsiella pneumoniae is an important human pathogen that causes diseases such as urinary tract infections, pneumonia, bloodstream infections, bacteremia, and sepsis. The rise of multidrug-resistant strains has severely limited the available treatments for K. pneumoniae infections. On the other hand, K. pneumoniae activity (and related infections) urgently requires improved management strategies. A growing number of medical applications are using nanotechnology, which uses materials with atomic or molecular dimensions, to diagnose, eliminate, or reduce the activity of different infections. In this review, we start with the traditional treatment and detection method for K. pneumoniae and then concentrate on selected studies (2015-2022) that investigated the application of nanoparticles separately and in combination with other techniques against K. pneumoniae.

The making of hypervirulent Klebsiella pneumoniae

Klebsiella pneumoniae is a notorious bacterium in clinical practice. Virulence, carbapenem-resistance and their convergence among K. pneumoniae are extensively discussed in this article. Hypervirulent K. pneumoniae (HvKP) has spread from the Asian Pacific Rim to the world, inducing various invasive infections, such as pyogenic liver abscess, endophthalmitis, and meningitis. Furthermore, HvKP has acquired more and more drug resistance. Among multidrug-resistant HvKP, hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP), and carbapenem-resistant hypervirulent K. pneumoniae (CR-HvKP) are both devastating for their extreme drug resistance and virulence. The hypervirulence of HvKP is primarily attributed to hypercapsule, macromolecular exopolysaccharides, or excessive siderophores, although it has many other factors, for example, lipopolysaccharides, fimbriae, and porins. In contrast with classical determination of HvKP, that is, animal lethality test, molecular determination could be an optional and practical method after improvement. HvKP, including Hv-CRKP and CR-HvKP, has been progressing. R-M and CRISPR-Cas systems may play pivotal roles in such evolutions. Hv-CRKP and CR-HvKP, in particular the former, should be of severe concern due to their being more and more prevalent.

Klebsiella pneumoniae Infection as a Mimicker of Multiple Metastatic Lesions

We describe the case of a 42-year-old man with cirrhosis who presented with fever and imaging concerning for metastatic disease from suspected renal cell carcinoma. He had a right renal mass with multiple pulmonary masses and underwent a lung biopsy and oncology consultation. Blood cultures revealed Klebsiella pneumoniae, and all the lesions disappeared after intravenous (IV) antibiotics. Our case attempts to increase awareness of this unique presentation of invasive Klebsiella infections and discusses host factors that can predispose to this condition.

Klebsiella invasive syndrome: a challenging diagnosis

Klebsiella invasive syndrome is a rare condition that typically presents as a liver abscess with metastatic infection, with mortality rates as high as 14% potentially due to diagnostic delay by clinicians. Here, we present a case of a woman in her 60s, who presented with symptoms and signs consistent with meningitis, imaging findings suggestive of possible leptomeningeal carcinomatosis a long with areas of lung consolidation and abdominal nodules and lymphadenopathy, presumably metastatic malignancy. We diagnosed Klebsiella invasive syndrome and treated it conservatively with medical management, including a long course of intravenous antibiotic therapy and supportive care. This is an infrequently encountered clinical entity with potentially fatal consequences, and we hope to add to the existing literature on the subject and drive home the point that it should be considered in the differential diagnoses in the appropriate clinical scenario.

Proteus mirabilis and Klebsiella pneumoniae as pathogens capable of causing co-infections and exhibiting similarities in their virulence factors

The genera Klebsiella and Proteus were independently described in 1885. These Gram-negative rods colonize the human intestinal tract regarded as the main reservoir of these opportunistic pathogens. In favorable conditions they cause infections, often hospital-acquired ones. The activity of K. pneumoniae and P. mirabilis, the leading pathogens within each genus, results in infections of the urinary (UTIs) and respiratory tracts, wounds, bacteremia, affecting mainly immunocompromised patients. P. mirabilis and K. pneumoniae cause polymicrobial UTIs, which are often persistent due to the catheter biofilm formation or increasing resistance of the bacteria to antibiotics. In this situation a need arises to find the antigens with features common to both species. Among many virulence factors produced by both pathogens urease shows some structural similarities but the biggest similarities have been observed in lipids A and the core regions of lipopolysaccharides (LPSs). Both species produce capsular polysaccharides (CPSs) but only in K. pneumoniae these antigens play a crucial role in the serological classification scheme, which in Proteus spp. is based on the structural and serological diversity of LPS O-polysaccharides (OPSs). Structural and serological similarities observed for Klebsiella spp. and Proteus spp. polysaccharides are important in the search for the cross-reacting vaccine antigens.

In vitro activity of celastrol in combination with thymol against carbapenem-resistant Klebsiella pneumoniae isolates

Klebsiella pneumoniae is an opportunistic pathogen causing nosocomial and community-acquired infections. Klebsiella has developed resistance against antimicrobials including the last resort class; carbapenem. Currently, treatment options for carbapenem-resistant-Klebsiella (CRK) are very limited. This study aims to restore carbapenem effectiveness against CRK using celastrol and thymol. Clinical Klebsiella isolates were identified using biochemical and molecular methods. Antimicrobial susceptibility was determined using disk-diffusion method. Carbapenemase-production was tested phenotypically and genotypically. Celastrol and thymol-MICs were determined and the carbapenemase-inhibitory effect of sub-MICs was investigated. Among 85 clinical Klebsiella isolates, 72 were multi-drug-resistant and 43 were meropenem-resistant. Phenotypically, 39 isolates were carbapenemase-producer. Genotypically, bla_NDM1 was detected in 35 isolates, bla_VIM in 17 isolates, bla_OXA in 18 isolates, and bla_KPC was detected only in 6 isolates. Celastrol showed significant inhibitory effect against carbapenemase-hydrolytic activity. Meropenem-MIC did not decrease in presence of celastrol, only 2-fold decrease was observed with thymol, while 4-64 fold decrease was observed when meropenem was combined with both celastrol and thymol. Furthermore, thymol increased CRK cell wall-permeability. Molecular docking revealed that celastrol is superior to thymol for binding to KPC and VIM-carbapenemase. Our study showed that celastrol is a promising inhibitor of multiple carbapenemases. While meropenem-MIC were not affected by celastrol alone and decreased by only 2-folds with thymol, it decreased by 4-64 folds in presence of both celastrol and thymol. Thymol increases the permeability of CRK-envelope to celastrol. The triple combination (meropenem/celastrol/thymol) could be useful for developing more safe and effective analogues to restore the activity of meropenem and other β-lactams.

Identification of the BolA Protein Reveals a Novel Virulence Factor in K. pneumoniae That Contributes to Survival in Host

BolA has been characterized as an important transcriptional regulator, which is induced in the stationary phase of growth and is often associated with bacterial virulence. This study was initiated to elucidate the role of the BolA in the virulence of K. pneumoniae. Using a mouse infection model, we revealed bolA mutant strain yielded significantly decreased bacterial loads in the liver, spleen, lung, and kidney, and failed to form liver abscesses. Gene deletion demonstrated that the bolA was required for siderophore production, biofilm formation, and adhesion to human colon cancer epithelial cells HCT116. Quantitative reverse transcriptase PCR (RT-qPCR) indicated that BolA could impact the expression of pulK, pulF, pulE, clpV, vgrG, entE, relA, and spoT genes on a genome-wide scale, which are related to type II secretion system (T2SS), type VI secretion system (T6SS), guanosine tetraphosphate (ppGpp), and siderophore synthesis and contribute to fitness in the host. Furthermore, the metabolome analysis showed that the deletion of the bolA gene led to decreased pools of five metabolites: biotin, spermine, cadaverine, guanosine, and flavin adenine dinucleotide, all of which are involved in pathways related to virulence and stress resistance. Taken together, we provided evidence that BolA was a significant virulence factor in the ability of K. pneumoniae to survive, and this was an important step in progress to an understanding of the pathways underlying bacterial virulence.

IMPORTANCE BolA has been characterized as an important transcriptional regulator, which is induced in the stationary phase of growth and affects different pathways directly associated with bacterial virulence. Here, we unraveled the role of BolA in several phenotypes associated with the process of cell morphology, siderophore production, biofilm formation, cell adhesion, tissue colonization, and liver abscess. We also uncovered the importance of BolA for the success of K. pneumoniae infection and provided new clues to the pathogenesis strategies of this organism. This work constitutes a relevant step toward an understanding of the role of BolA protein as a master regulator and virulence factor. Therefore, this study is of great importance for understanding the pathways underlying K. pneumoniae virulence and may contribute to public health care applications.

Multidrug-Resistant Bacteria: Their Mechanism of Action and Prophylaxis

In the present scenario, resistance to antibiotics is one of the crucial issues related to public health. Earlier, such resistance to antibiotics was limited to nosocomial infections, but it has now become a common phenomenon. Several factors, like extensive development, overexploitation of antibiotics, excessive application of broad-spectrum drugs, and a shortage of target-oriented antimicrobial drugs, could be attributed to this condition. Nowadays, there is a rise in the occurrence of these drug-resistant pathogens due to the availability of a small number of effective antimicrobial agents. It has been estimated that if new novel drugs are not discovered or formulated, there would be no effective antibiotic available to treat these deadly resistant pathogens by 2050. For this reason, we have to look for the formulation of some new novel drugs or other options or substitutes to treat such multidrug-resistant microorganisms (MDR). The current review focuses on the evolution of the most common multidrug-resistant bacteria and discusses how these bacteria escape the effects of targeted antibiotics and become multidrug resistant. In addition, we also discuss some alternative mechanisms to prevent their infection as well.

Phenotypic Characterization of Virulence Factors and Antibiogram of Klebsiella pneumoniae Isolates from Various Clinical Samples – A Cross Sectional Study

K. pneumoniae is known to cause hospital and community acquired infections. It is usually associated with upper & lower respiratory infections, septicaemia, urinary tract infection, wound infections, neonatal sepsis, meningitis, and endophthalmitis. The virulence factors play a role in its existence in different environmental conditions and therefore help in establishing Klebsiella pneumoniae infection in the human body. Multi drug resistant Klebsiella pneumoniae is an increasing threat to human health. Klebsiella pneumoniae is one of the species recognized as nosocomial pathogens that exhibit multidrug resistance and virulence in ESKAPE group as per WHO. The study was conducted to determine the various virulence factors & the antimicrobial pattern of Klebsiella pneumoniae isolates. A cross sectional observational study, conducted in Department of Microbiology of R.L. Jalappa Hospital and Research Centre, Kolar, Sample size of 150. All 150 Klebsiella pneumoniae isolates collected for the study, The Klebsiella pneumoniae isolates which were positive for various virulence factors were as follows on hemolysis 7(4.66%), capsule 150(100%), Hypermucoviscosity formation 66(44%), biofilm production 81(54%), siderophore production 110(73.33%), protease 135(90%), gelatinase 126(84%), lipase production 119(79.33%), lecithinase activity 82(54.66%). The drug resistance klebsiella pneumoniae were as follows: ESBL producers 24(16.67%), AmpC producers were 22(14.67%), MDR 116(74.20%), extensive drug resistant (XDR) 30(20%), pan drug resistant (PDR) 42(28%), Carbapenem resistance 65.33% reported. The increasing coexistence of virulence factors & antimicrobial resistance pattern is of particular concern. Hence active surveillance for antimicrobial resistance & virulence determinants is imperative now to implement effective control measures to prevent the rapid spread of drug resistance.

Klebsiella pneumoniae liver abscess with purulent meningitis and endogenous endophthalmitis: A case report

This is a rare but typical case of a Klebsiella pneumoniae liver abscess with migratory infections including purulent meningitis and endogenous endophthalmitis. The patient had a chief complaint of 7 days of fever, 4 days of blurry vision, and 4 h of glossolalia. Ultrasound scan and computed tomography (CT) suggested a liver abscess. Both blood and drainage fluid cultures grew K. pneumoniae with a high mucosal phenotype. The patient was finally diagnosed with a K. pneumoniae liver abscess, purulent meningitis, and endogenous K. pneumoniae endophthalmitis in the right eye. Ultrasound-guided percutaneous catheter drainage (PCD) of the liver abscess was performed, and meropenem was used to control infection. The patient was given 0.1 ml of vancomycin (10 g/L) and 0.1 ml of ceftazidime (20 g/L) were by intravitreal injection for the treatment of endophthalmitis. The infection was gradually controlled after such treatments. The patient was discharged from our hospital with an improved condition. However, during the time of follow-up, she developed complications due to severe pneumonia and eventually died in a local hospital. This case revealed that a rapid diagnosis followed by appropriate treatment would improve prognosis and prevent severe metastatic complications.

Genome-Based Analysis of a Multidrug-Resistant Hypervirulent Klebsiella pneumoniae

Reports on multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-hvKP) in recent years indicate the wide-spreading trend of MDR-hvKP. The co-occurrence of hypervirulence and drug resistance poses a great challenge to clinical treatment. In this study, molecular characteristics of an MDR strain hvKP247 and 30 clinically isolated hvKP strains were characterized. The whole genome of hvKP247 belonging to sequence type (ST) 5214 and capsule serotype K1 was sequenced and analyzed. Conjugation experiments were performed to evaluate transferability of the plasmids in hvKP247. We found two new STs among our isolates, ST5570 and ST5571. The ST5214 hvKP247 contained two transferable plasmids: a hybrid virulence plasmid (pHvKP247-vir) carrying transfer-related modules that had self-transferable ability, and a drug-resistant plasmid (pHvKP247-MDR) that could be indirectly transferred with the help of pHvKP247-vir. The virulence-related genes were located on the pHvKP247-vir and chromosomal ICEKp1 mobile genetic element. In conclusion, the hybrid virulence plasmid and the drug-resistant plasmid are co-transferred, which emphasizes the importance of raising public awareness of the simultaneous spread of virulence and resistance genes of MDR-hvKP strains.

Impact of Sub-MIC Eugenol on Klebsiella pneumoniae Biofilm Formation via Upregulation of rcsB

The Rcs phosphorelay system is present in many members of the Enterobacteriaceae. The aim of this study was to illustrate the possible mechanisms of eugenol on ultimate targets of Klebsiella pneumoniae (K. pneumoniae) Rcs phosphorelay, rcsB, and impact on biofilm formation. The minimum inhibitory concentration (MIC) of eugenol against K. pneumoniae KP1 and KP1 ΔrcsB strain was determined using the 2-fold micro-dilution method. Biofilm was measured by crystal violet staining. Transcriptome sequencing was performed to investigate sub-MIC eugenol on K. pneumoniae, and gene expression at mRNA level was analyzed by RT-qPCR. In vitro biofilm formation test and molecular docking were used to evaluate the effect of eugenol and to predict potential interactions with RcsB. MicroScale Thermophoresis (MST) was conducted for further validation. MIC of eugenol against K. pneumoniae KP1 and KP1 ΔrcsB strain was both 200 μg/ml. Transcriptome sequencing and RT-qPCR results indicated that rpmg, degP, rnpA, and dapD were downregulated, while rcsB, rcsD, rcsA, yiaG, and yiaD were upregulated in the eugenol-treated group. ΔrcsB exhibited a weakened biofilm formation capacity. Additional isopropyl-β-d-thiogalactoside (IPTG) hinders biofilm formation, while sub-MIC eugenol could promote biofilm formation greatly. Docking analysis revealed that eugenol forms more hydrophobic bonds than hydrogen bonds. MST assay also showed a weak binding affinity between eugenol and RcsB. These results provide significant evidence that rcsB plays a key role in K. pneumoniae biofilm formation. Sub-MIC eugenol facilitates biofilm formation to a large extent instead of inhibiting it. Our findings reveal the potential risk of natural anti-biofilm ingredients at sub-MIC to treat drug-resistance bacteria.

The Lung Alveolar Cell (LAC) miRNome and Gene Expression Profile of the SP-A-KO Mice After Infection With and Without Rescue With Human Surfactant Protein-A2 (1A0)

Human surfactant protein (SP)-A1 and SP-A2 exhibit differential qualitative and quantitative effects on the alveolar macrophage (AM), including a differential impact on the AM miRNome. Moreover, SP-A rescue (treatment) of SP-A-knockout (KO) infected mice impoves survival. Here, we studied for the first time the role of exogenous SP-A protein treatment on the regulation of lung alveolar cell (LAC) miRNome, the miRNA-RNA targets, and gene expression of SP-A-KO infected mice of both sexes. Toward this, SP-A-KO mice of both sexes were infected with Klebsiella pneumoniae, and half of them were also treated with SP-A2 (1A⁰). After 6 h of infection/SP-A treatment, the expression levels and pathways of LAC miRNAs, genes, and target miRNA-mRNAs were studied in both groups. We found 1) significant differences in the LAC miRNome, genes, and miRNA-mRNA targets in terms of sex, infection, and infection plus SP-A2 (1A⁰) protein rescue; 2) an increase in the majority of miRNA-mRNA targets in both study groups in KO male vs. female mice and involvement of the miRNA-mRNA targets in pathways of inflammation, antiapoptosis, and cell cycle; 3) genes with significant changes to be involved in TP-53, tumor necrosis factor (TNF), and cell cycle signaling nodes; 4) when significant changes in the expression of molecules from all analyses (miRNAs, miRNA-mRNA targets, and genes) were considered, two signaling pathways, the TNF and cell cycle, referred to as “integrated pathways” were shown to be significant; 5) the cell cycle pathway to be present in all comparisons made. Because SP-A could be used therapeutically in pulmonary diseases, it is important to understand the molecules and pathways involved in response to an SP-A acute treatment. The information obtained contributes to this end and may help to gain insight especially in the case of infection.

Review of Known and Unknown Facts of Klebsiella Pneumoniae and its Relationship with Antibiotics

Antibiotics are commonly used to treat bacterial respiratory infections, but they can exacerbate inflammation by releasing microbial components that overstimulate the immune system, leading to greater tissue damage. Klebsiella pneumoniae is a gram-negative, rod-shaped bacteria of the family Enterobacteriaceae. Knowing about Klebsiella pneumoniae is extremely important in the present situation, as it is one of the major causal organisms of pneumonia. Internal and external factors of K. pneumoniae are responsible for the entry and multiplication inside the host. Antibiotics against K. pneumoniae are a class of Penicillins, Cephalosporins, Monobactams, and Carbapenems which have the β-lactam ring in common with variable side chains. Combating the antibiotics by synthesizing the enzymes like beta-lactamases is the main reason for the survival of these organisms against newer generation antibiotics. In this review, we have tried to discuss about Klebsiella pneumoniae, antibiotics, and their mechanism of action.

Metastatic Klebsiella Pneumoniae in an Immunocompetent Patient: A Rare, Atypical Presentation of Klebsiella Syndrome

Metastatic Klebsiella pneumoniae (MKP) is a rare, atypical presentation of Klebsiella syndrome. The disease primarily affects patients with underlying immunocompromised status, but its prevalence in immunocompetent patients without any underlying illness is rare. We present a rare case of MKP in a 41-year-old Caucasian male without prior comorbidities who presented with blurry vision and was found to have MKP. The current case report also discusses the diagnostic modalities, complications, and treatment options of MKP.

African cereal fermentations: A review on fermentation processes and microbial composition of non-alcoholic fermented cereal foods and beverages

Africa has a rich tradition of cereal fermentations to produce diverse products including baked goods, porridges, non-alcoholic beverages and alcoholic beverages. Diversity also relates to the choice of the fermentation substrates, which include wheat, maize, teff, sorghum and millet, and the fermentation processes that are used in food production. For fermentation processes that are used in baking and brewing, it is well established that the composition of fermentation microbiota and thus the impact of fermentation on product quality is determined by the choice of fermentation conditions. This link has not been systematically explored for African cereal fermentations. This review therefore aims to provide an overview on the diversity of African fermented cereal products, and to interrogate currently available literature data with respect to the impact of fermentation substrate and fermentation processes on the assembly of fermentation microorganisms and product quality.

High Osmotic Stress Increases OmpK36 Expression through the Regulation of KbvR to Decrease the Antimicrobial Resistance of Klebsiella pneumoniae

Klebsiella pneumoniae is a pathogen known for its high frequency of antimicrobial resistance. Responses to various environmental stresses during its life can influence the resistance to antibiotics. Here, we demonstrate the role and mechanism of KbvR regulator in the response to environmental osmotic stress and in the effect of osmotic stress on antimicrobial resistance. The kbvR mutant strain exhibited increasing tolerance to high osmotic stress and certain antibiotics, including β-lactams. The expression levels of KbvR and outer membrane porin OmpK36 were upregulated in response to high osmotic stress in the wild type (WT), and the deletion of kbvR decreased the expression level of ompK36. The membrane permeability of the kbvR mutant strain was decreased, which was partly restored through the upregulated expression of OmpK36. The DNA affinity purification sequencing (DAP-seq) and microscale thermophoresis (MST) assay disclosed the binding of KbvR to the promoter of the ompK36 gene, indicating that KbvR directly and positively regulated the expression of OmpK36. The high osmotic stress increased the susceptibility to β-lactams and the expression of ompK36 in the WT strain. However, the increased ompK36 expression and the susceptibility to β-lactams in the kbvR mutant strain under high osmotic stress were lower than those of WT. In conclusion, our study has identified that high osmotic stress in the environment influenced the resistance of K. pneumoniae to antibiotics and that the regulation of KbvR with OmpR on the expression of OmpK36 was involved in countering high osmotic stress to change the antimicrobial resistance.

IMPORTANCEKlebsiella pneumoniae is considered a global threat because of the rising prevalence of multidrug-resistant strains and their optimal adaptation to clinical environments and the human host. The sensing and adaption abilities of bacteria to the environmental osmotic stress can change the expression of their outer membrane porins, membrane permeability, and resistance to antibiotics. This study reports that KbvR is a newly found regulator that can be upregulated under high osmotic stress and directly regulate the expression of OmpK36 to change the resistance of K. pneumoniae to β-lactam antibiotics. The results demonstrate how adaptation to high osmotic stress changes the sensitivity of K. pneumoniae to antibiotics. The mechanism can be used to sensitize bacteria to antibiotics and highlight new potential strategies for exploiting shared constraints in governing adaptation to diverse environmental challenges.

An Outbreak of ST859-K19 Carbapenem-Resistant Hypervirulent Klebsiella pneumoniae in a Chinese Teaching Hospital

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) has been increasingly reported worldwide. Here, we report an outbreak caused by sequence type 859-K19 (ST859-K19) CR-hvKP isolates in a teaching hospital in China. Interestingly, K. pneumoniae ST859 was a single-locus variant of ST11 but has never been reported before. A total of 11 nonrepetitive ST859 CR-hvKP isolates were collected from 11 patients, 3 of which died of severe CR-hvKP infection. Antimicrobial susceptibility assay results showed that all the 11 CR-hvKP isolates exhibited high-level resistance to commonly used antibiotics, only remaining susceptible to colistin, tigecycline, and ceftazidime/avibactam. Whole-genome sequencing (WGS) was performed using the Illumina platform for the 11 CR-hvKP isolates, and RJ9299 was further sequenced using the PacBio platform. A phylogram tree using WGS data revealed that all the 11 CR-hvKP isolates were clustered in 1 clade, which probably indicated clone transmission. Determinants of resistance and virulence gene analysis using WGS data confirmed the 11 isolates had almost identical resistance gene profiles (bla_KPC-2, bla_TEM-1B, bla_SHV-187, rmtB, fosA6) and virulence gene (rmpA, rmpA2, iucABCDiutA) profiles, which hint at clone spread again. The complete genome size of RJ9299 was 5,875 kb, including a 5,445-kb chromosome, a 215-kb virulence plasmid (pVir-CR-hvKP-RJ9299), a 109-kb bla_KPC-2-harboring plasmid (pKPC-2-RJ9299), and three circular plasmids. Comparative genomics showed pVir-RJ9299 (IncHI1B type) and pKPC-2-RJ9299 (IncFII-IncR) possessed over 99% similarity to pLVPK and pKPC-CR-hvKP-C789, respectively. Serum resistance assays and a Galleria mellonella infection model showed the 11 isolates exhibited different levels of virulence. This is the first report of an outbreak caused by ST859 CR-hvKP isolates.

IMPORTANCE The emergence of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) in China has posed a great threat to public health, especially in the highly transmissible ST11 clone. With the transmission of virulence and resistance determinants, CR-hvKP isolates have been reported in an increasing number of sequence types (STs), including ST23, ST65, ST1797, ST43, ST231, ST147, ST15, ST383, ST268, ST595, ST375, ST48, and ST307. Here, we report an outbreak caused by ST859-K19 CR-hvKP isolates in a teaching hospital in China. ST859 is a single-locus variant of ST11. There is no literature on ST859 K. pneumoniae in public databases, let alone ST859 CR-hvKP isolates. To our knowledge, this is the first report to depict the molecular and genomic characteristics of ST859 CR-hvKP isolates. Active surveillance approaches should be implemented to promptly find the spread of CR-hvKP isolates in health care settings.

Prostatic Abscess Caused by Klebsiella pneumoniae: A 6-Year Single-Center Study

Hypervirulent Klebsiella pneumoniae (hvKp) is an important strain that can cause multiple organ infections. Although hvKp infection cases are increasing, there is limited information on the prostatic abscesses caused by K. pneumoniae. Furthermore, the clinical significance of hvKp associated with K1 or K2 capsular types or virulence genes in prostatic abscesses remains unclear. Therefore, we aimed to elucidate the clinical and microbiological characteristics of prostatic abscesses caused by K. pneumoniae in relation to various virulence genes. A retrospective study was performed at a 1200-bed tertiary hospital between January 2014 and December 2019. Patients diagnosed with prostatic abscesses with K. pneumoniae isolated from blood, urine, pus, or tissue cultures were enrolled in this study. Our results demonstrate that 30.3% (10/33) of the prostatic abscesses were caused by K. pneumoniae. All strains isolated from patients with prostatic abscesses due to K. pneumoniae were the K1 capsular type, and eight patients (80.0%) carried rmpA and iutA genes that identified hvKp. These findings suggest that hvKp is an important pathogen in prostatic abscesses. Therefore, when treating patients with K. pneumoniae prostatic abscesses, attention should be paid to the characteristics of hvKp, such as bacteremia, multiorgan abscess formation, and metastatic spread.

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.

Molecular Epidemiology of Hypervirulent K. pneumoniae and Problems of Health-Care Associated Infections

The review describes virulence factors of hypervirulent K. pneumoniae (hvKp) including genes determining its virulence and discusses their role in the development of health-care associated infections. The contribution of individual virulence factors and their combination to the development of the hypervirulence and the prospects of using these factors as biomarkers and therapeutic targets are described. Virulence factors of hvKp and “classical” K. pneumoniae strains (cKp) with no hypervirulence genes were compared. The mechanisms of biofilm formation by hvKp and high incidence of its antibiotic resistance are of particular importance for in health care institutions. Therefore, the development of methods for hvKp identification allowing early prevention of severe hvKp infection and novel approaches to abrogate its spreading are new challenges for epidemiology, infection diseases, and critical care medicine. New technologies including bacteriological and molecular studies make it possible to develop innovative strategies to diagnose and treat infection caused by hvKp. These include monitoring of both genetic biomarkers of hvKp and resistance plasmid that carry of virulence genes and antibiotic resistance genes, creation of immunological agents for the prevention and therapy of hvKp (vaccines, monoclonal antibodies) as well as personalized hvKp-specific phage therapies and pharmaceuticals enhancing the effect of antibiotics. A variety of approaches can reliably prepare our medicine for a new challenge: spreading of life-threatening health-care associated infections caused by antibiotic-resistant hvKp strains.

Antibiotic-resistance in medically important bacteria isolated from commercial herbal medicines in Africa from 2000 to 2021: a systematic review and meta-analysis

Background

Antimicrobial resistance is swiftly increasing all over the world. In Africa, it manifests more in pathogenic bacteria in form of antibiotic resistance (ABR). On this continent, bacterial contamination of commonly used herbal medicine (HM) is on the increase, but information about antimicrobial resistance in these contaminants is limited due to fragmented studies. Here, we analyzed research that characterized ABR in pathogenic bacteria isolated from HM in Africa since 2000; to generate a comprehensive understanding of the drug-resistant bacterial contamination burden in this region.

Methods

The study was conducted according to standards of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). We searched for articles from 12 databases. These were: PubMed, Science Direct, Scifinder scholar, Google scholar, HerbMed, Medline, EMBASE, Cochrane Library, International Pharmaceutical Abstracts, Commonwealth Agricultural Bureau Abstracts, African Journal Online, and Biological Abstracts. Prevalence and ABR traits of bacterial isolates, Cochran’s Q test, and the I² statistic for heterogeneity were evaluated using MedCalcs software. A random-effects model was used to determine the pooled prevalence of ABR traits. The potential sources of heterogeneity were examined through sensitivity analysis, subgroup analysis, and meta-regression at a 95% level of significance.

Findings

Eighteen studies met our inclusion criteria. The pooled prevalence of bacterial resistance to at least one conventional drug was 86.51% (95% CI = 61.247–99.357%). The studies were highly heterogeneous (I² = 99.17%; p < 0.0001), with no evidence of publication bias. The most prevalent multidrug-resistant species was Escherichia coli (24.0%). The most highly resisted drug was Ceftazidime with a pooled prevalence of 95.10% (95% CI = 78.51–99.87%), while the drug-class was 3^rd generation cephalosporins; 91.64% (95% CI = 78.64–96.73%). None of the eligible studies tested isolates for Carbapenem resistance. Extended Spectrum β-lactamase genes were detected in 89 (37.2%) isolates, mostly Salmonella spp., Proteus vulgaris, and K. pneumonia. Resistance plasmids were found in 6 (5.8%) isolates; the heaviest plasmid weighed 23,130 Kilobases, and Proteus vulgaris harbored the majority (n = 5; 83.3%).

Conclusions

Herbal medicines in Africa harbor bacterial contaminants which are highly resistant to conventional medicines. This points to a potential treatment failure when these contaminants are involved in diseases causation. More research on this subject is recommended, to fill the evidence gaps and support the formation of collaborative quality control mechanisms for the herbal medicine industry in Africa.

Acute femoral osteomyelitis due to hypermucoviscous Klebsiella pneumonia

Hypervirulent hypermucoviscous Klebsiella pneumoniae strains have emerged as clinically important pathogens causing invasive infections. K. pneumoniae osteomyelitis is uncommon in adult patients, and may mimic bone tumors on presentation. We report a patient with left rectus femoris muscle abscess and acute osteomyelitis of the left femur due to hypermucoviscous K. pneumoniae with negative blood culture, who was initially thought to have left thigh tumor. The patient's infection resolved with surgical drainage and debridement and intravenous and antibiotic therapy.

Polyketide-derived macrobrevins from marine macroalga-associated Bacillus amyloliquefaciens as promising antibacterial agents against pathogens causing nosocomial infections

Marine heterotrophs are treasured bio-resources of antimicrobial metabolites, and herein we report the biosynthetic potential of Bacillus amyloliquefaciens (ex. Fukumoto) Priest et al. (Bacillaceae) strain MTCC 12713 isolated from an intertidal macroalga Kappaphycus alvarezii (Doty) L.M.Liao (Rhodophyta: Solieriaceae). The bacterium showed promising biological activities against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis. Genome mining of B. amyloliquefaciens MTCC 12713 predicted the gene clusters coding for biosynthesis of antibacterial metabolites. Bioactivity-guided purification was directed to isolate four homologous members of trans-acyltransferase polyketide synthase-derived antibiotics, which were classified as macrobrevin analogues. The compounds exhibited antibacterial activities against nosocomial pathogens, for example, methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Klebsiella pneumoniae and Pseudomonas aeruginosa with a range of MIC values from 1.56 to 6.25 μg/mL, although standard antibiotic chloramphenicol was active at 6.25-12.5 μg/mL. Conspicuously, the macrobrevin compound encompassing hexahydro-41-hydroxy-macrobrevin-31-acetate functionality, displayed considerably greater antagonistic activities against methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Vibrio parahaemolyticus, P. aeruginosa, K. pneumoniae, and Streptococcus pyogenes (MIC 1.56 μg/mL) compared to the positive controls and other macrobrevin analogues. Trans-AT polyketide synthase-stimulated biosynthetic pathway of macrobrevin compounds, through repetitive decarboxylative Claisen condensation between acetyl-S-KS domain and malonate-S-ACP units could corroborate the structural elucidation. In the genome mining study, among the 34 biosynthetic gene clusters, a hybrid trans-acyltransferase (trans-AT) pks/nrps gene cluster, which extends up to ∼81 Kb, was recognized in the genome of B. amyloliquefaciens MTCC 12713. The pks/nrps cluster revealed 46% similarity to trans-AT PKS-derived macrobrevin isolated from a mesophilic bacterium Brevibacillus sp. Leaf182 associated with the phyllosphere of the wild-type genotype of Arabidopsis thaliana. The binding positions for macrobrevins with S. aureus peptide deformylase showed docking score of larger than 14 kcal/mol, which was considerably greater than macrolactin N and actinonin (<10 kcal/mol). These present findings documented that the marine heterotrophic B. amyloliquefaciens MTCC 12713 could be used to develop prospective antibacterial agents belonging to macrobrevin analogues for biotechnological and pharmaceutical applications.

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.

Molecular prevalence of resistance determinants, virulence factors and capsular serotypes among colistin resistance carbapenemase producing Klebsiella pneumoniae: a multi-centric retrospective study

The emergence of colistin-carbapenem-resistant Klebsiella pneumoniae (CCR-Kp) in bloodstream infection results in high mortality, and virulence factor contributes further to the difficulty of treatment. A total of 158 carbapenem-resistant K. pneumoniae (CRKP) isolates causing bloodstream infection were collected from three Indian tertiary care hospitals during the 9-month study period, of which 27 isolates exhibited resistance to both colistin and carbapenem antibiotics. In this study, all the strains were characterized for antimicrobial resistance, virulence factors and capsular serotypes that facilitate the development of colistin and carbapenem-resistant K.pneumoniae (CCR-Kp) in bloodstream infection. Fourteen isolates displayed extremely drug resistance (XDR), susceptible only to tigecycline, and the remaining 13 isolates displayed multidrug resistance (MDR). The gene prevalence analysis for CCR-Kp isolates showed the predominance of bla KPC (81.48%) followed by bla NDM (62.96%), bla VIM (37.03%) and bla IMP (18.51%) genes. The distribution of virulence genes was found to be fimH (81.48%), wabG (59.25%), mrkD (55.56%), entB (48.15%), irp1 (33.33%), and rmpA (18.52%). The capsular serotypes K1, K2, K5 and K54 have been identified in 16 isolates. The absence of plasmid-mediated colistin resistance (mcr) genes implies the involvement of other mechanisms. The ERIC and (GTG)5 molecular typing methods detected 18 and 22 distinct clustering patterns among the CCR-Kp isolates, respectively. A strong correlation between ERIC and (GTG)5 genotyping method was established with antimicrobial resistance patterns and virulence determinants at P < 0.05, while no correlation was found with capsular serotyping. Similar virulence and resistance typing among the isolates suggest hospital-acquired infection in a health care setup. These outcomes will advance our awareness of CCR-Kp outbreaks associated with tertiary care hospitals and help forecast their occurrence in the near future.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03056-4.

The gut microbiome and microbial metabolites in acute myocardial infarction

Emerging evidence has highlighted the role of the gut microbiome in human health. However, the integrative role of the gut microbiome and microbial metabolites in acute myocardial infarction (AMI) remains unclear. The current study profiled the microbial community through 16S rRNA gene sequencing and shotgun metagenomic sequencing, and measured fecal short-chain fatty acids and circulating choline pathway metabolites among 117 new-onset AMI cases and 78 controls. Significant microbial alternations were observed in AMI patients compared with controls (P = 0.001). The abundances of nine species (e.g., Streptococcus salivarius, Klebsiella pneumoniae) were positively associated, and one species (Roseburia hominis) was inversely associated with AMI status and severity. A gut microbial score at disease onset was associated with the risk of major adverse cardiovascular events in 3.2 years (hazard ratio [95% CI]: 2.01 [1.04-4.24]) in AMI patients. The molar proportions of fecal acetate and butyrate were higher, and the circulating levels of choline and carnitine were lower in AMI patients than in controls. In addition, disease classifiers showed that AMI cases and controls had a more distinct pattern in taxonomical composition than in pathways or metabolites. Our findings suggested that microbial composition and functional potentials were associated with AMI status and severity.