Ecology and etiology of bacterial top rot in maize caused by Klebsiella pneumoniae KpC4

Systematic review and meta-analysis of the potential effects of endophytic bacteria Klebsiella on plant growth promotion and biocontrol of pathogens

Klebsiella is a bacterial genus widely recognized in the medical field but with underexplored potential in agriculture. This study employed a systematic review and meta-analysis to investigate scientific articles on plant growth promotion effects associated with endophytic bacteria Klebsiella species. A total of 39 relevant studies, published between 2012 and 2024, were identified based on strict inclusion and exclusion criteria. The analysis revealed that Klebsiella sp., K. pneumoniae, and K. variicola are cosmopolitan species that have functional versatility in phytohormone production, nutrient solubilization, and pathogen control in agricultural systems in both tropical and temperate zones. The data showed a significant correlation between the use of Klebsiella sp. and plant growth, highlighting the positive impact of these species in controlling aggressive pathogens. These findings underscore the potential of Klebsiella as a biotechnological tool for sustainable agricultural practices, enhancing plant growth and reducing the reliance on chemical inputs. The study further emphasizes the need for future research to deepen genomic characterization and expand the agricultural applications of these bacteria.

Newly isolated Drexlerviridae phage LAPAZ is physically robust and fosters eradication of Klebsiella pneumoniae in combination with meropenem

Due to the spread of multidrug resistance there is a renewed interest in using bacteriophages (briefly: phages) for controlling bacterial pathogens. The objective of this study was the characterization of a newly isolated phage (i.e. phage LAPAZ, vB_KpnD-LAPAZ), its antimicrobial activity against multidrug resistant Klebsiella pneumoniae and potential synergistic interactions with antibiotics. LAPAZ belongs to the family Drexlerviridae (genus: Webervirus) and lysed 30 % of tested strains, whereby four distinct capsular types can be infected. The genome consists of 51,689 bp and encodes 84 ORFs. The latent period is 30 min with an average burst size of 27 PFU/cell. Long-term storage experiments show that LAPAZ is significantly more stable in wastewater compared to laboratory media. A phage titre of 90 % persists up to 30 min at 50 ˚C and entire phage loss was seen only at temperatures > 66 ˚C. Besides stability against UV-C, antibacterial activity in liquid culture medium was consistent at pH values ranging from 4 to 10. Unlike exposure to phage or antibiotic alone, synergistic interactions and a complete bacterial eradication was achieved when combining LAPAZ with meropenem. In addition, synergism with the co-presence of ciprofloxacin was observed and phage resistance emergence could be delayed. Without co-addition of the antibiotic, phage resistant mutants readily emerged and showed a mixed pattern of drug sensitivity alterations. Around 88 % became less sensitive towards ceftazidime, meropenem and gentamicin. Conversely, around 44 % showed decreased resistance levels against ciprofloxacin. Whole genome analysis of a phage-resistant mutant with a 16-fold increased sensitivity towards ciprofloxacin revealed one de novo frameshift mutation leading to a gene fusion affecting two transport proteins belonging to the major facilitator-superfamily (MFS). Apparently, this mutation compromises ciprofloxacin efflux efficiency and further studies are warranted to understand how the non-mutated protein might be involved in phage-host adsorption.

The Cultured Microbiome of Pollinated Maize Silks Shifts after Infection with Fusarium graminearum and Varies by Distance from the Site of Pathogen Inoculation

Styles transmit pollen-derived sperm nuclei from pollen to ovules, but also transmit environmental pathogens. The microbiomes of styles are likely important for reproduction/disease, yet few studies exist. Whether style microbiome compositions are spatially responsive to pathogens is unknown. The maize pathogen Fusarium graminearum enters developing grain through the style (silk). We hypothesized that F. graminearum treatment shifts the cultured transmitting silk microbiome (TSM) compared to healthy silks in a distance-dependent manner. Another objective of the study was to culture microbes for future application. Bacteria were cultured from husk-covered silks of 14 F. graminearum-treated diverse maize genotypes, proximal (tip) and distal (base) to the F. graminearum inoculation site. Long-read 16S sequences from 398 isolates spanned 35 genera, 71 species, and 238 OTUs. More bacteria were cultured from F. graminearum-inoculated tips (271 isolates) versus base (127 isolates); healthy silks were balanced. F. graminearum caused a collapse in diversity of ~20-25% across multiple taxonomic levels. Some species were cultured exclusively or, more often, from F. graminearum-treated silks (e.g., Delftia acidovorans, Klebsiella aerogenes, K. grimontii, Pantoea ananatis, Stenotrophomonas pavanii). Overall, the results suggest that F. graminearum alters the TSM in a distance-dependent manner. Many isolates matched taxa that were previously identified using V4-MiSeq (core and F. graminearum-induced), but long-read sequencing clarified the taxonomy and uncovered greater diversity than was initially predicted (e.g., within Pantoea). These isolates represent the first comprehensive cultured collection from pathogen-treated maize silks to facilitate biocontrol efforts and microbial marker-assisted breeding.

Novel Virulence Factors Deciphering Klebsiella pneumoniae KpC4 Infect Maize as a Crossing-Kingdom Pathogen: An Emerging Environmental Threat

Klebsiella pneumoniae is not only a human and animal opportunistic pathogen, but a food-borne pathogen. Cross-kingdom infection has been focused on since K. pneumoniae was identified as the pathogen of maize, banana, and pomegranate. Although the pathogenicity of K. pneumoniae strains (from ditch water, maize, and human) on plant and mice has been confirmed, there are no reports to explain the molecular mechanisms of the pathogen. This study uncovered the K. pneumoniae KpC4 isolated from maize top rot for the determination of various virulence genes and resistance genes. At least thirteen plant disease-causing genes are found to be involved in the disruption of plant defense. Among them, rcsB is responsible for causing disease in both plants and animals. The novel sequence types provide solid evidence that the pathogen invades plant and has robust ecological adaptability. It is imperative to perform further studies on the verification of these KpC4 genes’ functions to understand the molecular mechanisms involved in plant−pathogen interactions.

Clinical Characteristics and Risk Factors for Critically Ill Patients with Carbapenem-Resistant Klebsiella pneumonia e (CrKP): A Cohort Study from Developing Country

BACKGROUND

Increasing evidence indicates carbapenem-resistant Klebsiella pneumoniae (CrKP) is increasingly prevalent in intensive care unit (ICU), but its clinical characteristics and risk factors remain unknown.

AIM

The aim of the present study was to evaluate clinical characteristics, risk factors in critically ill patients with CrKP infection.

METHODS

A retrospective study was included in patients from January 2013 to October 2019. Clinical data were collected from CrKP patients on the day of specimen collection admitted to ICU. Multivariable logistic regression was used for risk factors. Receiver operating curve (ROC) and the area under the curve (AUC) with DeLong method of MedCalc software were used. Two-way repeated-measures ANOVA analysis was used to analyze the characteristics of independent risk factors over time.

FINDINGS

A total of 147 adult patients with CrKP were screened, among them, 89 (median age 64.0 years, 66 (74.15%) males) patients with CrKP were finally included, of which 38 patients (42.7%) were non-survival group. Multivariate logistic regression analysis indicated that lactic acid (OR3.04 95% CI 1.38-6.68, P = 0.006), APACHE II score (OR 1.20, 95% CI 1.09-1.33, P < 0.001), tigecycline combined with fosfomycin treatment (OR0.15, 95% CI 0.04-0.65, P = 0.011) are independent risk factors for 28-day mortality in patients with CRKP infection (P<0.05). Combined lactic acid with APACHE II score could predict 28-day mortality, of which AUC value was 0.916 (95% CI, 0.847-0.985), with sensitivity 0.76 and specificity 0.98. ANOVA analysis showed that APACHE II score and lactic acid between the two groups at three-time points were statistically significant, which interactive with time and showed an upward and downward trend with time (P < 0.05).

CONCLUSION

Therapeutic strategy based on improving lactic acid and APACHE II would contribute to the outcome in patients with CrKP infection. Tigecycline combined with fosfomycin could reduce the 28-day mortality in patients with CrKP infection in developing country.