Bacterial Growth Research Articles

Development and Evaluation of Preparations Based on Ethanol Extract of Chrysopogon zizanioides, Asteracantha longifolia, Asparagus racemosus, Tinospora cordifolia

The emergence of antibiotic-resistant bacteria poses a critical challenge to global public health, necessitating the exploration of alternative therapeutic strategies. This study investigates the antimicrobial potential of bioactive compounds derived from four medicinal plants: Chrysopogon zizanioides, Asteracantha longifolia, Asparagus racemosus, and Tinospora cordifolia. These plants, traditionally used in various medicinal systems, contain compounds such as khusimol, stigmasterol, lupeol, shatavarin IV, asparagamine A, tinosporin, and cordifolioside A, which have shown promising antimicrobial properties against resistant pathogens. Two formulations were developed: Formulation 1, designed for oral administration, and Formulation 2, a topical cream, both targeting antibiotic-resistant strains like methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Escherichia coli (MDR E. coli). The Minimum Inhibitory Concentration (MIC) of each extract and formulation was determined using a microdilution method. Results indicate that these plant-based formulations exhibit significant inhibitory effects on bacterial growth, with potential applications as complementary therapies to conventional antibiotics. This study highlights the potential of these medicinal plants as sources of novel antimicrobial agents, providing a sustainable approach to combating antibiotic resistance.

The preservative effect of the black rice's cold, hot and ultrasonic ethanol extracts on the storage quality of beef patties

SummaryThis work aimed to determine the total anthocyanin and phenolic contents and antioxidant capacity of extracts of the black rice's cold, hot and ultrasonic‐assisted extracts and their preservative effect on the storage quality of beef patties. The three extracts exhibited high anthocyanin, phenolic content and antioxidant capacity, and they were used in beef patties at five treatments (negative control without extract, positive control with 0.01% butylated hydroxytoluene (BHT), 7.5% cold extract, 7.5% hot extract and 7.5% ultrasound‐assisted extract). Raw and cooked beef patties were tested at 0, 3, 6, 9 and 12 days of cold storage in aerobically packaged polyethylene containers regarding pH, oxidative stability, antioxidant capacity and microbial quality. While adding black rice extracts did not influence the proximate composition of raw samples (P > 0.05), it slowed down the pH and lipid oxidation during storage and provided pH and thiobarbituric acid reactive substances (TBARS) stability in all final products. The BHT and treatments with extract indicated a higher 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) value than the negative control. Also, the incorporation of black rice extracts slightly retarded bacterial growth. These results suggest that the black rice extracts at 7.5% can be used effectively to protect beef patties from microbial spoilage and oxidation during cold storage for 12 days.

Phytochemical Diversity and Biological Effects of Juniperus thurifera L., Essential Oil : A Comparative Study using In Vitro and In Silico Methods.

This study aims to elucidate the phytochemical diversity and biological activities of J. thurifera essential oil (JTEO) through a comparative analysis of samples from two distinct regions: Tensift-Al Haouz and Azilal, using both in vitro and in silico methods. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed 21 components in the Tensift-Al Haouz JTEO (99.99% of the oil) and 23 components in the Azilal JTEO (99.58% of the oil), with oxygenated monoterpenes being the predominant compounds in both. The biological activities were assessed in vitro. Antioxidant properties, evaluated using DPPH, FRAP, and ABTS assays, showed significant activity in both oils. Antibacterial activity was tested against two strains of Gram-positive and two strains of Gram-negative bacteria, with both oils demonstrating notable bacterial growth inhibition. Enzymatic assays assessed the antidiabetic (α-amylase and α-glucosidase), dermo-protective (tyrosinase and elastase), and neuroprotective (AChE and BChE) activities. Both oils displayed substantial inhibitory effects across all tested activities, with variations attributed to their distinct chemical compositions. In silico analyses of six target enzymes confirmed significant binding affinities of the major compounds. Notably, 2,2'-Thiobis(6-tert-butyl-p-cresol) exhibited strong binding affinities with AChE, BChE, α-amylase, α-glucosidase, tyrosinase, and elastase, with binding energies ranging from -10.0 to -6.2 kcal/mol.

Formulation of Dual-Functional Nonionic Cetomacrogol Creams Incorporated with Bacteriophage and Human Platelet Lysate for Effective Targeting of MDR P. aeruginosa and Enhanced Wound Healing.

Successful development of phage-based therapeutics and their utility predominantly depend on the mode and route of phage administration. Topical and site-directed phage application evokes minimal immune clearance and allows more phage-host adsorption, thereby ensuring higher phage efficacy. However, a notable drawback of conventional topical phage applications is the absence of sustained release. Occlusive emollients guarantee the controlled release of active pharmaceutical ingredients (APIs), thereby facilitating administration, preventing moisture loss, and acting as a skin barrier. In this study, we developed phage and human platelet lysate (h-PL) incorporated cetomacrogol-based creams for combined phage therapy and wound healing. The base material for phage immobilization was formulated by emulsifying paraffin and sterile water with cetomacrogol (emulsifying agent). Specifically, we incorporated a Pseudomonas aeruginosa-infecting lytic phage vB_PaeM_M12PA in the formulation and characterized its genome in this study. Cetomacrogol, a nonionic PEG (polyethylene glycol) based ether, rendered phage stability and allowed initial burst release followed by continuous controlled release of phages from the embedding matrix in the initial 6-8 h. Rheological studies showed that the material has elastic properties with storage moduli (G') values ranging from 109.51 ± 2.10 to 126.02 ± 3.13 kPa, indicating frequency-independent deformation. Platelet lysates in the cream acted as wound healing agents, and in vitro evaluation of cell migration and wound healing capacity of h-PL showed a significant enhancement by the sixth hour compared to untreated groups. The phage-incorporated cream showed sustained phage release in solid media and a significant reduction in bacterial growth in liquid cultures. In vivo wound healing studies in 6-week-old Wistar rats with full-thickness excision wounds and subsequent histopathological studies showed that the formulation enhanced wound healing and tissue restoration efficiency. In conclusion, the study unveils a promising approach for integrated phage therapy and wound healing strategies.

Clinical and biochemical factors for bacteria in bile among patients with acute cholangitis.

Acute cholangitis is a clinical syndrome caused by a bacterial infection in the biliary system. The bacteria could exist in the bile before bile drainage despite empirical antibiotic treatment. Patients with acute cholangitis admitted to a tertiary hospital in Southeastern China from August 2011 to September 2021 were involved when bile cultures were performed. Patient information before bile cultures and during hospitalization was extracted from the clinical record database. The risk factors related to bacteria in bile were assessed by univariable and multivairable logistic regression analysis, respectively. A total of 533 patients (66.05%) had bacterial growth in bile. Alanine aminotransferase concentration [odds ratio (OR) = 0.998, P < 0.001], absolute monocyte count (OR = 0.335, P = 0.001), and duration of antibiotic use (OR = 0.933, P = 0.026) were negatively correlated with bacteria in bile. In contrast, C-reactive protein (OR = 1.006, P = 0.003), thrombin time (OR = 1.213, P = 0.033), prothrombin time (OR = 1.210, P = 0.011), and age (OR = 1.025, P < 0.001) were positively correlated with bacteria in bile. Based on an area under the receiver operating characteristic curve of 0.737 (95% CI, 0.697-0.776, P < 0.001), combining these seven variables could efficiently predict the presence of bacteria in bile among patients with acute cholangitis. The combination of clinical indicators before bile drainage could predict the risk of bacteria in bile for patients with acute cholangitis.

OpgH is an essential regulator of Caulobacter morphology.

Bacterial growth and division rely on intricate regulation of morphogenetic complexes to remodel the cell envelope without compromising envelope integrity. Significant progress has been made in recent years towards understanding the regulation of cell wall metabolic enzymes. However, other cell envelope components play a role in morphogenesis as well. A primary factor required to protect envelope integrity in low osmolarity environments is OpgH, the synthase of osmoregulated periplasmic glucans (OPGs). Here, we demonstrate that OpgH is essential in the α-proteobacterium Caulobacter crescentus. Unexpectedly, depletion of OpgH or attempted complementation with a catalytically dead OpgH variant results in striking asymmetric bulging and cell lysis. These shape defects are accompanied by reduced cell wall synthesis and mislocalization of morphogenetic complexes. Interestingly, overactivation of the CenKR two-component system that has been implicated in cell envelope stress homeostasis in α-proteobacteria phenocopies the morphogenetic defects associated with OpgH depletion. Each of these perturbations leads to an increase in the levels of the elongasome protein, MreB, and decreases in the levels of divisome proteins FtsZ and MipZ as well as OpgH, itself. Constitutive production of OpgH during CenKR overactivation prevents cell bulging, but cells still exhibit morphogenetic defects. We propose that OPG depletion activates CenKR, leading to changes in the expression of cell envelope-related genes, but that OPGs also exert CenKR-independent effects on morphogenesis. Our data establish a surprising function for an OpgH homolog in morphogenesis and reveal an essential role of OpgH in maintaining cell morphology in Caulobacter.IMPORTANCEBacteria must synthesize and fortify the cell envelope in a tightly regulated manner to orchestrate growth and adaptation. Osmoregulated periplasmic glucans (OPGs) are important, but poorly understood, constituents of Gram-negative cell envelopes that contribute to envelope integrity and protect against osmotic stress. Here, we determined that the OPG synthase OpgH plays a surprising, essential role in morphogenesis in Caulobacter crescentus. Loss of OpgH causes asymmetric cell bulging and lysis via misregulation of the localization and activity of morphogenetic complexes. Overactivation of the CenKR two-component system involved in envelope homeostasis phenocopies OpgH depletion, suggesting that depletion of OpgH activates CenKR. Because cell envelope integrity is critical for bacterial survival, understanding how OpgH activity contributes to morphogenesis and maintenance of envelope integrity could aid in the development of antibiotic therapies.

Vitamin B12 ameliorates gut epithelial injury via modulating the HIF-1 pathway and gut microbiota

Inflammatory bowel diseases (IBDs) are immune chronic diseases characterized by recurrent episodes, resulting in continuous intestinal barrier damage and intestinal microbiota dysbiosis. Safe strategies aimed at stabilizing and reducing IBDs recurrence have been vigorously pursued. Here, we constructed a recurrent intestinal injury Drosophila model and found that vitamin B12 (VB12), an essential co-factor for organism physiological functions, could effectively protect the intestine and reduce dextran sulfate sodium-induced intestinal barrier disruption. VB12 also alleviated microbial dysbiosis in the Drosophila model and inhibited the growth of gram-negative bacteria. We demonstrated that VB12 could mitigate intestinal damage by activating the hypoxia-inducible factor-1 signaling pathway in injured conditions, which was achieved by regulating the intestinal oxidation. In addition, we also validated the protective effect of VB12 in a murine acute colitis model. In summary, we offer new insights and implications for the potential supportive role of VB12 in the management of recurrent IBDs flare-ups.

The evolution of heteroresistance via small colony variants in Escherichia coli following long term exposure to bacteriostatic antibiotics

Traditionally, bacteriostatic antibiotics are agents able to arrest bacterial growth. Despite being traditionally viewed as unable to kill bacterial cells, when they are used clinically the outcome of these drugs is frequently as effective as when a bactericidal drug is used. We explore the dynamics of Escherichia coli after exposure to two ribosome-targeting bacteriostatic antibiotics, chloramphenicol and azithromycin, for thirty days. The results of our experiments provide evidence that bacteria exposed to these drugs replicate, evolve, and generate a sub-population of small colony variants (SCVs) which are resistant to multiple drugs. These SCVs contribute to the evolution of heteroresistance and rapidly revert to a susceptible state once the antibiotic is removed. Stated another way, exposure to bacteriostatic drugs selects for the evolution of heteroresistance in populations previously lacking this trait. More generally, our results question the definition of bacteriostasis as populations exposed to bacteriostatic drugs are replicating despite the lack of net growth.

Enhanced diabetic foot ulcer treatment with a chitosan-based thermosensitive hydrogel loaded self-assembled multi-functional nanoparticles for antibacterial and angiogenic effects

Inhibiting bacterial growth and promoting angiogenesis are essential for enhancing wound healing in diabetic patients. Excessive oxidative stress at the wound site can also lead to an accumulation of reactive oxygen species. To address these challenges, a smart thermosensitive hydrogel loaded with therapeutic agents was developed. This formulation features self-assembled nanoparticles named CIZ, consisting of chlorogenic acid (CA), indocyanine green (ICG), and zinc ions (Zn2+). These nanoparticles are loaded into a chitosan-β-glycerophosphate hydrogel, named CIZ@G, which enables rapid gel formation under photothermal effects. The hydrogel demonstrates good biocompatibility and effectively releases drugs into diabetic foot ulcers (DFU) wound. Benefiting from the dual actions of CA and zinc ions, the hydrogel exhibits potent antioxidative and anti-inflammatory effects, enhances the expression of vascular endothelial growth factor (VEGF) and Platelet endothelial cell adhesion molecule-1 (CD31), and promotes angiogenesis. Both in vitro and in vivo experiments confirm that CIZ@G can effectively inhibit the growth of Staphylococcus aureus post-laser irradiation and accelerate wound remodeling within 14 days. This approach offers a new strategy for the treatment of diabetic foot ulcers (DFU), potentially transforming patient care in this challenging clinical area.

S. hispanica mucilage/ ZnO based films: Preparation, characterization, and potential application

The use of plastic for food packaging is a major contributor to environmental pollution. To address this issue, biopolymeric films have emerged as a potential alternative to plastic products commonly used in food packaging. These biopolymeric films can be enhanced with antimicrobial agents to make them more effective. This study aimed to develop and evaluate the properties of films made from Salvia hispanica mucilage and ZnO particles. The mucilage was obtained by filtering and drying seeds, while ZnO was synthesized using the forced hydrolysis of ZnC₄H₆O₄ and NaOH. The films were produced by combining the mucilage with varying concentrations of ZnO (0.1, 0.5, and 1.0%) using a casting method. Tests were conducted to evaluate the films' physical, chemical, and biological properties. X-ray diffraction analysis showed that ZnO was present, while scanning electron microscopy revealed the presence of C, O, and Zn elements. Fourier transform infrared spectroscopy confirmed the presence of S. hispanica mucilage. Thermogravimetric analysis showed that the films were thermally stable at temperatures below 225 °C. Dynamic mechanical analysis revealed that the 0.1% film had the best resistance compared to the 0.5% and 1.0% films. Finally, the study found that the antimicrobial activity of the films depended on the concentration, size, and morphology of the ZnO particles. In conclusion, further research is needed to create films that can effectively inhibit pathogenic bacteria growth in food and be a viable alternative to plastic for food packaging.

Microbial growth on temporary pacemaker leads post-TAVR: pathogen spectrum and clinical implications.

Transcatheter aortic valve replacement (TAVR) is an established treatment option for patients with symptomatic severe aortic stenosis across all stages of surgical risk. Rapid pacing during the procedure and the risk for the occurrence of conduction disturbances after TAVR requires the pre-interventional insertion of a temporary pacemaker (TP). However, this approach poses risks, including the risk of infection. For this reason, the following study aimed to investigate microbial growth on temporary pacemaker leads and its association with outcome post-TAVR and to identify associated pathogens and related risk factors. A prospective study was conducted including 344 patients undergoing TAVR at the Heart Centre Bonn. Of these, 97 patients did not require TP leads as they already had permanent pacemakers; this group was considered as comparison group. The TP leads of the remaining 247 patients were removed, sonicated, and cultured to investigate bacterial growth over a period of 14days. Finally, we compared patients without microbial growth (n = 184) and patients with microbial growth (n = 63). The primary endpoint of the study was 30-day all-cause mortality, secondary endpoints were periprocedural infections, the length of the postprocedural hospital stay, 30-day major vascular complications and the 30-day stroke rate. The majority of cases (74.5%) showed no bacterial growth. In the remaining cases (25.5%), diverse microorganisms were identified, mostly non-pathogenic bacteria. The statistical analysis revealed no significant differences between groups according to microbial growth in terms of 30-day mortality (p = 0.446), postprocedural hospital stay (p = 0.401), periprocedural infections (p = 0.434), 30-day major vascular complications (p = 1.0), and 30-day stroke rate (p = 1.0). Notably, the timing of sheath insertion was significantly associated with microbial growth; sheath placement more than 2days prior to the procedure was associated with a significantly higher risk of microbial growth (OR: 2.1; 95% CI 1.1-4.3) (p = 0.030). The presence of temporary leads does not significantly impact clinical outcomes, irrespective of bacterial growth on the lead. However, the timing and duration of sheath placement plays a crucial role in contamination incidence. Thus, temporary leads/sheaths should be placed shortly before the procedure and removed promptly to reduce the risk of contamination/infection.

The aroma transformation of Japanese sea bass (Lateolabrax japonicas) through endogenous enzyme incubation during the lag phase of attached microorganisms

Endogenous enzymes play a crucial role in determining fish product aroma. However, the attached microorganisms can promote enzyme production, making it challenging to identify specific aromatic compounds resulting from endogenous enzymes. Thus, we investigated the aroma transformation of Japanese sea bass through enzymatic incubation by controlling attached microorganisms during the lag phase. Our results demonstrate that enzymatic incubation significantly enhances grassy and sweet notes while reducing fishy odors. These changes in aroma are associated with increased levels of 10 volatile compounds and decreased levels of 3 volatile compounds. Among them, previous studies have reported enzyme reaction pathways for octanal, 1-nonanal, vanillin, indole, linalool, geraniol, citral, and 6-methyl-5-hepten-2-one; however, the enzymatic reaction pathways for germacrene D, beta-caryophyllene, pristane, 1-tetradecene and trans-beta-ocimene remain unclear. These findings provide novel insights for further study to elucidate the impact of endogenous enzymes on fish product aromas.

Comparative assessment of plate count and PMA-qPCR methods for modeling the growth of lactic acid bacteria in smoked Turkey ham

This study compared the quantitative polymerase chain reaction (qPCR) method combined with propidium monoazide (PMA) and the plate count (PC) method, both combined with predictive modeling, to describe the behavior of lactic acid bacteria (LAB) in vacuum-packaged sliced smoked turkey ham (STH). The PMA-qPCR method does not allow the DNA amplification of died cells but allow the amplification of viable cells, including the non-culturable. The standard curves relating quantification cycle (Cq) and log10 CFU/g demonstrated good linearity (R2 > 0.95), evidencing its accuracy and reproducibility. These curves were used to quantify Leuconostoc mesenteroides and Weissella viridescens in artificially inoculated STH samples stored at different isothermal temperatures (8, 10, 12, 16 and 20 °C). Firstly, the PMA-qPCR and PC methods were compared, and the analysis demonstrated a good correlation (R2 = 0.99) and agreement between the results. However, the PC method underestimated the quantification of W. viridescens cells by 0.76 log10 CFU/g at 8 °C, suggesting bacterial stress at this temperature, which was not observed for L. mesenteroides. In terms of growth, the maximum specific growth rate increased with rising temperature for both LAB. Predictive modeling indicated that the growth of L. mesenteroides and W. viridescens at 8 °C suggests a shelf life of approximately 4.25 days for STH based on PC data, and 4.13 days based on PMA-qPCR data. In conclusion, the PMA-qPCR method presented an advantage in terms of accuracy, especially under bacterial stress conditions, and proved to be a promising alternative for the quantification of LAB in refrigerated ready-to-eat meat products. The predictive models used were suitable for describing microbial growth, reinforcing the importance of the PMA-qPCR method in shelf life and food safety studies.

Novel Insights in the Application of Probiotic Yeast Saccharomyces boulardii in Dairy Products and Health Promotion

Probiotic organisms are increasingly being incorporated into foods in order to develop products to prevent and reduce many diseases. Saccharomyces boulardii, a probiotic yeast with unique properties, such as viability over a wide pH range, antibiotic resistance, and the ability to reach a steady state, has an advantage over bacterial probiotics. The present review highlights the potential application of S. boulardii in functional fermented dairy products and the genetic engineering of this probiotic microorganism as a therapeutic agent for the treatment of various infectious diseases. It was found that probiotic yeast stimulates the growth of lactic acid bacteria in dairy products, creating favorable conditions and positively affecting the product’s sensory characteristics. Moreover, its viability of more than 106 cfu/mL at the end of the yogurt shelf life confirms its probiotic effect. On the other hand, there is a growing interest in the design of probiotic strains to improve their characteristics and fill existing gaps in their spectrum of action such as the inhibition of some bacterial toxins, as well as anti-inflammatory and immunomodulatory effects. The strengthening of immune functions and effective therapies against various diseases by S. boulardii was confirmed. However, considering this yeast species’ potential, further research is necessary to accurately determine the functional properties in terms of incorporation into food matrices and from the aspect of health and well-being claims.

Characterisation of growth parameters for the extremely acidophilic archaeon Ferroplasma acidiphilum DSM 12658 using a two-step turbidimetric growth measurement method

The acidophilic archaeon Ferroplasma acidiphilum exhibits remarkable adaptations to life in highly acidic environments. Nevertheless, the investigation of its molecular biology is challenging because of the slow growth of the organism, low biomass yield, and limitations of standard growth measurement techniques caused by iron oxidation.•A novel two-step turbidimetric growth measurement (2TGM) method was developed to address the shortcomings associated with iron precipitation in culture media. The method comprises two distinct preparation steps.•The initial 2TGM step involves centrifuging culture samples at high speed to remove F. acidiphilum cells and iron precipitates, thus preparing a blank.•The second 2TGM step involves centrifuging the culture at a lower speed with the objective of selectively removing iron precipitates, thus allowing F. acidiphilum cells to remain suspended in the supernatant. This preparation enables subsequent measurement of cell density.A study on the growth of F. acidiphilum showed a standard logistic pattern with a 35-h lag phase, approximately 9-h doubling time, and 0.042 OD carrying capacity. A new two-step turbidimetric growth measurement (2TGM) method overcomes limitations of existing approaches, enabling further investigation of F. acidiphilum.

Effects of ZinT-Mediated Zinc Sequestration on Metallo-β-Lactamase Function in Escherichia coli

β-lactams are the most prescribed antibiotic class, but their clinical utility is threatened by the production of metallo-β-lactamase (MBL) enzymes by resistant bacteria. MBLs such as NDM-1 employ zinc ions as cofactors, allowing them to degrade β-lactams. The zinc chaperone ZinT transports zinc into the cytoplasm for intracellular functions, potentially decreasing the availability of zinc in the periplasm for MBLs. We hypothesize that when zinc is limited, ZinT could impair NDM-1 activity and make bacteria more susceptible to β-lactams. To determine whether ZinT and NDM-1 compete for periplasmic zinc, bacterial growth and NDM-1 activity were tested in zinc-poor M9 minimal media for NDM-1-producing Escherichia coli strains with different levels of zinT expression. In addition to wild-type and ΔzinT knockout strains, a recombinant zinT-containing plasmid was transformed into ΔzinT knockout cells to produce a complementation strain with increased zinT expression. Growth assays were conducted in M9 with various concentrations of the β-lactam antibiotic, meropenem. Under these conditions, the ΔzinT strain grew in significantly higher meropenem concentrations than the other strains tested. NDM-1 activity assays revealed that the ΔzinT strain hydrolyzed meropenem notably faster than wild-type cells, whereas the complementation strain showed almost no hydrolysis. This suggests that the increased ZinT production in the complementation strain effectively sequestered zinc from NDM-1. These differences in meropenem hydrolysis and bacterial growth were absent in zinc-sufficient Cation-Adjusted Mueller-Hinton Broth, providing evidence that ZinT and NDM-1 compete for periplasmic zinc under nutrient deficiency. Overall, our results elucidate the effects of competing zinc requirements under zinc-deficient conditions resembling the host environment during a bacterial infection. In these zinc-deficient environments, ZinT can deprive NDM-1 of zinc, causing impaired enzymatic activity and bacterial survival. By better understanding how MBLs function under physiological conditions, future investigations can more reliably explore countermeasures to the growing threat of antibiotic resistance.

Prevalence of the Cefazolin Inoculum Effect in Methicillin-Susceptible Staphylococcus aureus Isolates Collected from Kingston Health Sciences Centre.

Background: Staphylococcus aureus is a bacterium that causes serious human infections, including bloodstream infections, pneumonia, deep abscesses, and bone and joint infections. Methicillin-susceptible S. aureus (MSSA) are S. aureus bacteria susceptible to the antibiotic methicillin. Cefazolin is the first-line antibiotic to treat MSSA infections. The cefazolin inoculum effect (CzIE) is a lab phenomenon in which S. aureus is susceptible to cefazolin at a standard bacterial inoculum but develops resistance at a higher cell inoculum. CzIE occurs when the bacteria produce beta-lactamases that degrade cefazolin, preventing the antibiotic from inhibiting cell wall synthesis and allowing bacterial growth. In theory, CzIE may lead to cefazolin treatment failure, but currently, there is insufficient evidence in the literature. Objective: We aimed to determine the prevalence of the CzIE in patients with serious MSSA infections at Kingston Health Sciences Centre (KHSC). Methods: Clinical MSSA isolates from patients with serious infections at KHSC were collected. The MSSA isolates were then tested for CzIE using broth microdilution testing at a standard inoculum (5×10^5 CFU/mL) and a high inoculum (5×10^7 CFU/mL). The CzIE was defined as a ≥ 4-fold increase in minimum inhibitory concentration (MIC) from the standard to the high and with a MIC above the resistant breakpoint of 16 µg/mL. Results: Of the 51 MSSA isolates tested to date, 17 (33%) displayed CzIE, with 13 of the 17 (76%) requiring 64 µg/ml of antibiotic to prevent growth. Conclusion: Our initial testing indicates that the CzIE is common in MSSA infections at KHSC. We will complete testing 100 MSSA isolates for a more precise estimate of CzIE prevalence, which will be followed up with a chart review of the patients to determine if there is a correlation between CzIE and cefazolin treatment failure.

Regulation of Bacterial Growth and Behavior by Host Plant.

Plants are associated with diverse bacteria in nature. Some bacteria are pathogens that decrease plant fitness, and others are beneficial bacteria that promote plant growth and stress resistance. Emerging evidence also suggests that plant-associated commensal bacteria collectively contribute to plant health and are essential for plant survival in nature. Bacteria with different characteristics simultaneously colonize plant tissues. Thus, plants need to accommodate bacteria that provide service to the host plants, but they need to defend against pathogens at the same time. How do plants achieve this? In this review, we summarize how plants use physical barriers, control common goods such as water and nutrients, and produce antibacterial molecules to regulate bacterial growth and behavior. Furthermore, we highlight that plants use specialized metabolites that support or inhibit specific bacteria, thereby selectively recruiting plant-associated bacterial communities and regulating their function. We also raise important questions that need to be addressed to improve our understanding of plant-bacteria interactions.

Rifampicin tolerance and growth fitness among isoniazid-resistant clinical Mycobacterium tuberculosis isolates from a longitudinal study

Antibiotic tolerance in Mycobacterium tuberculosis reduces bacterial killing, worsens treatment outcomes, and contributes to resistance. We studied rifampicin tolerance in isolates with or without isoniazid resistance (IR). Using a minimum duration of killing assay, we measured rifampicin survival in isoniazid-susceptible (IS, n=119) and resistant (IR, n=84) isolates, correlating tolerance with bacterial growth, rifampicin minimum inhibitory concentrations (MICs), and isoniazid-resistant mutations. Longitudinal IR isolates were analyzed for changes in rifampicin tolerance and genetic variant emergence. The median time for rifampicin to reduce the bacterial population by 90% (MDK90) increased from 1.23 days (IS) and 1.31 days (IR) to 2.55 days (IS) and 1.98 days (IR) over 15–60 days of incubation, indicating fast and slow-growing tolerant sub-populations. A 6 log10-fold survival fraction classified tolerance as low, medium, or high, showing that IR is linked to increased tolerance and faster growth (OR = 2.68 for low vs. medium, OR = 4.42 for low vs. high, p-trend = 0.0003). High tolerance in IR isolates was associated with rifampicin treatment in patients and genetic microvariants. These findings suggest that IR tuberculosis should be assessed for high rifampicin tolerance to optimize treatment and prevent the development of multi-drug-resistant tuberculosis.

Mass Mortality of the Invasive Sea Urchin Diadema setosum in Türkiye, Eastern Mediterranean Possibly Reveals Vibrio Bacteria Infection

ABSTRACTThe invasive Diadema setosum (Leske, 1778) long‐spined sea urchin has been in the Mediterranean Sea since 2006, and then, it has been known that its population density has reached high values on the southern Aegean coasts of Türkiye. This study aimed to report the mass mortality event of D. setosum with the determined agent on the Aegean coast of Türkiye. In addition, it was targeted to provide information on the current status of its density based on seasonal SCUBA diving observations for the period between January 2023 and November 2023. The results showed that the mass mortality of D. setosum was determined in Muğla, Aegean Sea, in August 2023. Spine loss, the mucoid layer at the bottom of the appendages, and the outer body surface were observed as the clinical symptoms of the diseased samples. Bacterial growth was detected on Vibrio‐selected TCBS agar plates, while no other parasitic agents were determined in the coelomic fluid of sea urchins. The results of the biochemical (API 20E) and molecular tests confirmed the isolated bacteria as Vibrio spp. The density of D. setosum showed statistically significant temporal changes, and the highest and lowest mean density values were recorded in autumn and spring, respectively. Environmental stressors, such as increasing sea temperature levels, affect the marine ecosystem and lead to opportunistic pathogens. Long‐term monitoring of disease outbreaks is necessary to understand the interactions between species and the ecosystem.