The nutritional composition and cell size of microbial biomass for food applications are defined by the growth conditions.

BACKGROUND: It is increasingly recognized that conventional food production systems are not able to meet the globally increasing protein needs, resulting in overexploitation and depletion of resources, and environmental degradation. In this context, microbial biomass has emerged as a promising sustainable protein alternative. Nevertheless, often no consideration is given on the fact that the cultivation conditions affect the composition of microbial cells, and hence their quality and nutritional value. Apart from the properties and nutritional quality of the produced microbial food (ingredient), this can also impact its sustainability. To qualitatively assess these aspects, here, we investigated the link between substrate availability, growth rate, cell composition and size of Cupriavidus necator and Komagataella phaffii. RESULTS: Biomass with decreased nucleic acid and increased protein content was produced at low growth rates. Conversely, high rates resulted in larger cells, which could enable more efficient biomass harvesting. The proteome allocation varied across the different growth rates, with more ribosomal proteins at higher rates, which could potentially affect the techno-functional properties of the biomass. Considering the distinct amino acid profiles established for the different cellular components, variations in their abundance impacts the product quality leading to higher cysteine and phenylalanine content at low growth rates. Therefore, we hint that costly external amino acid supplementations that are often required to meet the nutritional needs could be avoided by carefully applying conditions that enable targeted growth rates. CONCLUSION: In summary, we demonstrate tradeoffs between nutritional quality and production rate, and we discuss the microbial biomass properties that vary according to the growth conditions.

Why do lactic acid bacteria thrive in chain elongation microbiomes?

Efficient waste management is necessary to transition towards a more sustainable society. An emerging trend is to use mixed culture biotechnology to produce chemicals from organic waste. Insights into the metabolic interactions between community members and their growth characterization are needed to mediate knowledge-driven bioprocess development and optimization. Here, a granular sludge bioprocess for the production of caproic acid through sugar-based chain elongation metabolism was established. Lactic acid and chain-elongating bacteria were identified as the two main functional guilds in the granular community. The growth features of the main community representatives (isolate Limosilactobacillus musocae G03 for lactic acid bacteria and type strain Caproiciproducens lactatifermentans for chain-elongating bacteria) were characterized. The measured growth rates of lactic acid bacteria (0.051 ± 0.005 h-1) were two times higher than those of chain-elongating bacteria (0.026 ± 0.004 h-1), while the biomass yields of lactic acid bacteria (0.120 ± 0.005 g biomass/g glucose) were two times lower than that of chain-elongating bacteria (0.239 ± 0.007 g biomass/g glucose). This points towards differential growth strategies, with lactic acid bacteria resembling that of a r-strategist and chain-elongating bacteria resembling that of a K-strategist. Furthermore, the half-saturation constant of glucose for L. mucosae was determined to be 0.35 ± 0.05 g/L of glucose. A linear trend of caproic acid inhibition on the growth of L. mucosae was observed, and the growth inhibitory caproic acid concentration was predicted to be 13.6 ± 0.5 g/L, which is the highest reported so far. The pre-adjustment of L. mucosae to 4 g/L of caproic acid did not improve the overall resistance to it, but did restore the growth rates at low caproic acid concentrations (1-4 g/L) to the baseline values (i.e., growth rate at 0 g/L of caproic acid). High resistance to caproic acid enables lactic acid bacteria to persist and thrive in the systems intended for caproic acid production. Here, insights into the growth of two main functional guilds of sugar-based chain elongation systems are provided which allows for a better understanding of their interactions and promotes future bioprocess design and optimization.

Atypical Skull-Base Osteomyelitis: Comprehensive Review and Multidisciplinary Management Viewpoints.

Atypical skull-base osteomyelitis is a rare but fatal disease that usually involves infection of the ethmoid, sphenoid, occipital, or temporal bones that form the skull base. Unlike typical (so-called otogenic), atypical skull-base osteomyelitis has no otogenic cause. Instead, some authors call atypical skull-base osteomyelitis sinonasal, since the infection most often originates from the nose and paranasal sinuses. Diagnosing and treating this disease is challenging. To assist in managing atypical skull-base osteomyelitis, a review of the most recent literature, with patient cases and multidisciplinary perspectives from otolaryngologists, neurosurgeons, radiologists, infectious disease specialists, pathologists, and clinical microbiologists, is provided in this paper.

High-rate conversion of lactic acid-rich streams to caproic acid in a fermentative granular system.

Lactic acid-driven chain elongation enables upgrading low-value organic streams into caproic acid. Recently, volumetric production rates over 0.5 g L-1 h-1have been reported for carbohydrate-rich streams in expanded granular sludge bed (EGSB) reactors. However, many target streams contain mixtures of carbohydrates and lactic acid, and little is known about their impact on product profile and microbial ecology, or the importance of carbohydrates as substrate to achieve high rates. This manuscript investigated varying glucose-to-lactate ratios and observed that decreasing glucose-content eliminated odd-chain by-products, while glucose omission required acetic acid addition to support lactic acid conversion. Decreasing the glucose-content fed resulted in decreasing amounts of granular biomass, with the disappearance of granules when no glucose was fed. Lowering the HRT to 0.3 days while feeding only lactic and acetic acid likely triggered re-granulation, enabling the highest lactic acid-driven caproic acid production rates reported thus far at 16.4 ± 1.7 g L-1 d-1.

Pre-exposure prophylaxis for HIV with oral tenofovir disoproxil fumarate/emtricitabine in men who have sex with men: Slovenian national demonstration project.

Prevalence of HIV in Slovenia is low, and men who have sex with men (MSM) have the highest risk for infection. Rates of enrolment into HIV care, initiation of antiretroviral therapy and reaching an undetectable viral load in HIV-infected patients are very high. Prevention of HIV infection for MSM with PrEP is not formally available in Slovenia. The aim of this study was to demonstrate possible implementation of PrEP in Slovenia. Sixty-nine (n = 69) MSM with increased risk for HIV received PrEP with oral tenofovir disproxil fumarate /emtricitabine and acquisition were followed for a mean of 566.6 days. They had 71 episodes of STIs (incidence 61.7 per 100 person-years). No one got acquired HIV infection. Estimated glomerular filtration rate (EGFR) was significantly lower 4 (p = 0.014) and 19 (p = 0.021) months after inclusion; however, there was no clinically significant renal failure (mean EGFR 110-115 mL/min). Self-reported body weight significantly increased after 7 months (p < 0.05). Overall EGFR and self-reported body weight did not change significantly. No significant change in adherence (overall mean 81.0%; 95% CI 77.5%-84.6%; p = 0.728), condom use (p = 0.077) and number of sexual partners (overall mean 2.36 per 30 days; 95% CI 2.06 to 2.65; p = 0.235) was found throughout the study. Participants reported 110 graded adverse effects (AE), 104 (94.5%) grade 1-2 and 6 (5.5%) grade 3-4. No participant discontinued PrEP due to AE. The study showed successful implementation of PrEP among MSM at high risk for HIV infection in Slovenia. Based on the results of our study, PrEP should be formally available in Slovenia.

Ethanol:propionate ratio drives product selectivity in odd-chain elongation with Clostridium kluyveri and mixed communities.

Microbial production of valerate, a five-carbon carboxylate, can occur from propionate and ethanol through a process called odd-chain elongation. The generation of even-chain compounds in this process lowers product selectivity, forming a key challenge. This study investigated factors determining product selectivity during odd-chain elongation in an odd-chain elongating mixed community and the pure culture Clostridium kluyveri DSM555. Incubations at different ratios of ethanol:propionate showed that increasing ratios (from 0.5 to 7) lowered product specificity, as evidenced by a decrease in the odd:even product ratio from 5.5 to 1.5 for C. kluyveri and from 15 to 0.8 for the mixed community. The consistency of these observations with literature data suggests that control of ethanol:propionate ratio offers a robust tool for process control in odd-chain elongation, while the flexible metabolism can also have implications for efficient use of ethanol during even-chain elongation processes.

Surveillance cultures for detection of rectal and lower respiratory tract carriage of colistin-resistant Gram-negative bacilli in intensive care unit patients: comparison of direct plating and pre-enrichment step.

Purpose. Increasing consumption of colistin as treatment for infections with multidrug-resistant (MDR) Gram-negative bacilli (GNB) has been accompanied by increasingly frequent reports of colistin-resistant (ColR) MDR GNB. Higher selective pressure creates a favourable environment that can facilitate the spread of ColR isolates. Monitoring of asymptomatic ColR GNB carriage can give us a better understanding of this emerging healthcare problem, particularly in wards with higher polymyxin selective pressure and prevalence of carbapenem-resistant GNB. Our aim was to assess the ColR GNB colonization rate in intensive care unit (ICU) patients and evaluate the performance of two surveillance protocols using a selective medium.Methodology. A prospective study included 739 surveillance samples (rectal swabs and tracheal aspirates) from 330 patients that were screened for ColR GNB carriage using SuperPolymyxin medium. Two approaches were used: direct sample plating and overnight pre-enrichment of samples followed by plating. Colistin resistance was confirmed with broth microdilution. ColR isolates were molecularly screened for plasmid-mediated mcr genes.Results. A total of 44/739 samples (45 ColR GNB isolates) were positive for ColR GNB, which included 31/330 (9.4 %) colonized patients; mcr genes were not detected. The direct plating method only identified 17/45 (37.8 %) isolates correctly, whereas the pre-enrichment protocol identified all 45 ColR GNB.Conclusion. The colonization rate among our ICU patients was 9.4  %. Based on our findings, the pre-enrichment step is necessary for the determination of ColR GNB carriage - even though the time to result takes an additional day, fewer than half of ColR GNB carriers were detected using the direct plating protocol.

Contribution of sonicate-fluid cultures and broad-range PCR to microbiological diagnosis in vascular graft infections.

BACKGROUND: Vascular graft infections (VGI) are associated with considerable morbidity and mortality, and antimicrobial treatment is an important adjunct to surgical treatment. While microbial aetiology of VGI is often difficult to determine, other techniques such as sonication of implanted material may be used to enhance the recovery of biofilm-associated organisms. METHODS: We performed a retrospective analysis of 22 consecutive patients treated for VGI at University Medical Centre Ljubljana from May 2011 through January 2015. Explanted vascular grafts were flooded with sterile Ringer solution, sonicated for 1 min at a frequency of 40 kHz and inoculated on solid and liquid culture media. Aerobic and anaerobic cultures were performed, incubated for 14 days and any significant bacterial growth was quantitatively evaluated. Additionally, broad-range PCR from sonicate fluid was performed. Microbiological results were compared with the results of preoperatively taken blood cultures and the results of intraoperative tissue cultures (material from peri-graft collection). RESULTS: Identification of the causative organism (irrespective of the method) was achieved in 95.8%. Preoperative blood cultures were positive in 35.3%, intraoperative tissue cultures in 31.8%, sonicate fluid culture in 79.2%, while broad-range PCR from sonicate fluid was positive in 66.7%. In 37.5% the pathogen detected in sonicate fluid culture or broad-range PCR was the only positive microbiological result. CONCLUSIONS: Sonicate fluid culture and broad-range PCR from explanted vascular grafts may contribute to optimization of antimicrobial treatment. Optimal timing of antibiotic therapy before explantation should be further assessed to improve diagnostic yield.