- Volume 7, Issue 2, 2025

Non-symbiotic Bradyrhizobium are among the most abundant and ubiquitous microbes in bulk soils globally. Despite this, most available genomic resources for Bradyrhizobium are derived from plant-associated strains. We present high-quality draft genomes for 17 Bradyrhizobium and four Nitrobacteraceae cultures isolated from bulk semiarid soils in Arizona, USA. The genome sizes range from 5.99 to 10.4 Mbp. Phylogenomic analysis of the 21 genomes indicates they fall into four clades. Two of the clades are nested within the Bradyrhizobium genus. The other two clades were associated with Nitrobacteraceae outgroups basal to Bradyrhizobium. All genomes lack genes coding for molybdenum or vanadium nitrogenases, and nod genes that code for proteins involved in nodulation, suggesting these isolates are free-living, non-symbiotic and do not fix dinitrogen gas. These genomes offer new resources for investigating free-living Bradyrhizobium lineages.

Acinetobacter baumannii is an important nosocomial pathogen causing high infections and morbidity among affected individuals, and most studies focus on nosocomial strains. However, A. baumannii can also be isolated from healthy community individuals. This study compared the pathogenicity of hospital and community A. baumannii isolates using Galleria mellonella and human cell cultures. The insect model, G. mellonella, and in vitro HeLa cell line were used with ten A. baumannii isolates (six community and four hospital isolates from Segamat, Malaysia). G. mellonella killing assays and HeLa cell adherence, invasion and cytotoxicity assays were performed to investigate the virulence and invasion potential of the isolates. Out of the ten isolates investigated, three community and two hospital isolates were found to be highly virulent in the G. mellonella infection model, killing 100% of larvae within 96 h. These strains were also found to be invasive and have significant cytotoxicity in HeLa cells. Our study revealed that community- and hospital-isolated A. baumannii could be equally virulent judged by both model systems. Undoubtedly, besides hospital settings, the presence of highly virulent A. baumannii in community reservoirs poses a significant public health risk and requires additional investigation.

We report the genome sequence of the bldA39 (J1700) mutant of Streptomyces coelicolor, a historically important strain that is deficient in sporulation and antimicrobial production. The S. coelicolor J1700 strain was used extensively from the 1980s onwards to underpin important discoveries in development and antibiotic production in Streptomyces. The bldA gene encodes a leucyl tRNA, required for the translation of the rare TTA codon found in ~2% of genes in Streptomyces. The whole genome of S. coelicolor J1700 was obtained via Illumina sequencing and mapped to the S. coelicolor M145 reference genome. Analysis of the genome sequence compared to S. coelicolor M145 identified the known bldA39 mutation (T>C) and revealed more than 300 further mutations, likely associated with the S. coelicolor J1501 genetic background the strain was created in, including the nature of the hisA1 and uraA1 alleles used extensively in genetic mapping experiments and several mutations in natural product biosynthetic gene clusters. This work highlights the importance of whole-genome sequencing of historically important strains.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to evolve, potentially leading to variants of concern that could become more transmissible, resist treatment, evade host immunity and reduce the effectiveness of currently available vaccines. Improved vaccines are still required as vaccination remains the most effective strategy against this virus. We have produced two SARS-CoV-2 virus-like particles (VLPs) using a baculovirus BacMam expression platform and examined their immunogenicity in mice. VLP1 contains the spike protein from the Wuhan strain, whereas VLP2 contains that of an Omicron variant. Mice immunized with VLP1 and boosted with VLP2 developed significantly higher antibodies in the sera, as well as higher numbers of IFN-γ secreting cells than the control group. Furthermore, both VLPs induced virus-neutralizing antibodies against Wuhan and Omicron variants. In conclusion, VLPs have the potential for the development of a safe and effective vaccine against SARS-CoV-2 variants.

Avian mycoplasmosis, caused by Mycoplasma synoviae and Mycoplasma gallisepticum, poses significant economic challenges due to respiratory issues, reduced egg production and soft eggshells. The variable lipoprotein haemagglutinin (VlhA) protein, crucial for pathogenicity, comprises conserved (MSPB) and variable (MSPA) regions. The aim of this study was to identify the conserved region of vlhA gene sequences in field strain. We examined vlhA sequences from field strains collected in central Mexico (Jalisco and Mexico City). Specifically, we analysed 124 deformed eggs and 10 laying hens from 9 farms with Hy-line and Bovans breeds. Using PCR targeting the mgc2 and 16S rRNA genes, we characterized 24 field strains, 4 of which were Myc. synoviae and 20 of which were Myc. gallisepticum. We analysed the vlhA regions, based on the AF035624.1 reference sequence, with American Type Culture Collection strains as positive controls. Additionally, we validated the PCR with 20 negative samples from Mycoplasma isolation without the need for cultivation. We identified two amplification regions: MSPB and MSPA. Bioanalysis revealed relationships between our field samples and avian Mycoplasma sequences in GenBank, alongside similarities with lipoproteins present in Acholeplasma laidlawii PG8 and Escherichia coli. Given the significance of the VlhA protein in pathogenicity and immune evasion, the identified conserved sequences hold potential as therapeutic targets and for phylogenetic studies.

Blood culture (BC) investigation remains the gold standard for the diagnosis of bloodstream infections. However, BC contamination can have clinical implications for the patient, cost implications for service providers and less well-documented, environmental impacts. Efforts to reduce BC contamination are a long-standing theme in quality improvement initiatives in emergency departments (EDs) and hospitals, prompted by hospital costs, healthcare inefficiencies and antimicrobial stewardship efforts. The WHO’s global analysis of healthcare waste in the context of COVID-19 has reported that tens of thousands of tonnes of extra medical waste were produced from the response to the COVID-19 pandemic, basing its estimates on the quantity of personal protective equipment. Additionally, recent literature has also shown increased BC contamination rates during the COVID-19 pandemic. We performed a retrospective review of the trend of BC contamination during the COVID-19 pandemic in our institution’s ED. We further discuss some of the potential implications of BC contamination, including potential environmental, economic and efficiency implications.

Background. Klebsiella pneumoniae is part of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, K. pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) group of multidrug-resistant (MDR) pathogens. K. pneumoniae is the leading cause of antimicrobial resistance-associated mortality and the second leading cause of nosocomial bloodstream infections (BSIs), globally and in sub-Saharan Africa. Therefore, it was aimed to determine the antibiotic resistance patterns of K. pneumoniae isolated from blood cultures of patients with features of sepsis at Mulago National Referral Hospital, Uganda.

Methods. The cross-sectional study on patients with features of sepsis utilized K. pneumoniae (n=30) isolated from positive blood culture specimens. The antibiotic resistance profile was determined by the Clinical and Laboratory Standards Institute’s Kirby–Bauer disc diffusion method, which was used to classify the isolates as susceptible, intermediate and resistant. K. pneumoniae isolates that were resistant to third-generation cephalosporins were subjected to extended-spectrum β-lactamase (ESBL) screening and confirmation using the double-disc synergy test using cefotaxime, ceftazidime, ceftriaxone, cefotaxime–clavulanic acid and ceftazidime–clavulanic acid. The results were analysed for frequencies.

Results. K. pneumoniae isolates showed emerging resistance to imipenem at 13% (4 out of 30) followed by amikacin at 17% (5 out of 30). There was intermediate resistance to gentamycin at 60% (18 out of 30). However, K. pneumoniae showed the highest resistance to piperacillin at 100% (30 out of 30) followed by sulphamethoxazole-trimethoprim and cefepime, both showing a percentage of 97% (29 out of 30). Up to 16 out of 30 (53.3%) of K. pneumoniae were positive for ESBL production, whilst 14 out of 30 (46.7%) were negative.

Conclusion. There was a high prevalence of antibiotic-resistant ESBL-producing K. pneumoniae isolates from BSI of patients with features of sepsis in Uganda’s Mulago National Referral Hospital.

Effective public health measures for communicable diseases rely on the ability to identify infectious individuals and prevent transmission from those individuals. For severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the presence of replication-competent virus in specimens from an individual is the gold standard for confirming infectiousness. However, viral culture from clinical specimens is difficult and infrequently performed. Instead, infectiousness may be inferred based on the abundance of viral RNA (or viral load) in a specimen, which is more easily assessed. For this reason, understanding the relationship between RNA viral load and infectious viral titre has important implications for public health strategy. In this case report, we quantified incident, longitudinal SARS-CoV-2 viral loads collected from saliva and nasal-swab specimens, and viral titre from nasal-swab specimens. We observed that the relationship between viral load and viral titre decreases by over five orders of magnitude throughout the course of the infection. Our work demonstrates the potential for infectious virus even in specimens with low viral loads collected during the early phases of infection.