Brucellosis is a serious public health problem worldwide and can affect any organ system. Due to brucellosis\'s variable clinical presentation, ranging from subclinical to fully symptomatic, and limited available information, it poses a diagnostic challenge. In this study, we reported a case series of patients with diverse presentations. In addition, we briefly described the pathophysiology and mechanisms of Brucella in the body. These case presentations will be valuable in increasing the awareness of physicians. A prompt diagnosis is crucial, as detecting some clues of the infection in its early stages can help avoid misdiagnoses.

Current antibiograms cannot discern the particular effect of a specific antibiotic when the bacteria are incubated with a mixture of antibiotics. To prove that this task is achievable, Escherichia coli strains were treated with ciprofloxacin for 45 min, immobilized on a slide and stained with SYBR Gold. In susceptible strains, the nucleoid relative surface started to decrease near the MIC, being progressively condensed as the dose increased. The shrinkage level correlated with the DNA fragmentation degree. Ciprofloxacin-resistant bacilli showed no change. Additionally, E. coli strains were incubated with ampicillin for 45 min and processed similarly. The ampicillin-susceptible strain revealed intercellular DNA fragments that increased with dose, unlike the resistant strain. Co-incubation with both antibiotics revealed that ampicillin did not modify the nucleoid condensation effect of ciprofloxacin, whereas the quinolone partially decreased the background of DNA fragments induced by ampicillin. Sixty clinical isolates, with different combinations of susceptibility-resistance to each antibiotic, were co-incubated with the EUCAST breakpoints of susceptibility of ciprofloxacin and ampicillin. The morphological assay correctly categorized all the strains for each antibiotic in 60 min, demonstrating the feasible independent evaluation of a mixture of quinolone and beta-lactam. The rapid phenotypic assay may shorten the incubation times and necessary microbial mass currently required for evaluation.

KKL-35 is a new oxadiazole compound with potent broad-spectrum antibacterial activity against a number of gram-positive and gram-negative bacteria. However, its influences on bacterial growth are unclear. This study is to investigate phenotypic changes of Staphylococcus aureus (SA) caused by KKL-35 and evaluate antibacterial activity of combinations of KKL-35 with 7 class of antibiotics available in medical facilities. KKL-35-treated SA showed significantly lower survival under stresses of NaCl and H2O2 than DMSO (21.03 ± 2.60% vs. 68.21 ± 5.31% for NaCl, 4.91 ± 3.14% vs. 74.78 ± 2.88% for H2O2). UV exposure significantly decreased survival of SA treated with KKL-35 than DMSO-treated ones (23.91 ± 0.71% vs. 55.45 ± 4.70% for 4.2 J/m2, 12.80 ± 1.03% vs. 31.99 ± 5.99% for 7.0 J/m2, 1.52 ± 0.63% vs. 6.49 ± 0.51% for 14.0 J/m2). KKL-35 significantly decreased biofilm formation (0.47 ± 0.12 vs. 1.45 ± 0.21) and bacterial survival in the serum resistance assay (42.27 ± 2.77% vs. 78.31 ± 5.64%) than DMSO. KKL-35 significantly decreased ethidium bromide uptake and efflux, as well as the cell membrane integrity. KKL-35 had low cytotoxicity and low propensity for resistance. KKL-35 inhibited SA growth in concentration-independent and time-dependent manners, and showed additivity when combined with the majority class of available antibiotics. Antibiotic combinations of KKL-35 with ciprofloxacin, rifampicin, or linezolid significantly decreased bacterial loads than the most active antibiotic in the corresponding combination. Thus, KKL-35 inhibits growth of SA by decreasing bacterial environmental adaptations, biofilm formation, membrane uptake and efflux, as well as increasing antibiotic sensitivity. Its potent antibacterial activity, low cytotoxicity, low propensity for resistance, and wide choices in antibiotic combinations make KKL-35 a promising leading compound to design new antibiotics in monotherapies and combination therapies to treat bacterial infections.

Photodynamic therapy (PDT) is an established therapy used for the treatment of cutaneous skin cancers and other non-infective ailments. There has been recent interest in the opportunity to use aPDT (antimicrobial PDT) to treat skin and soft tissue infections. PDT utilizes photosensitizers that infiltrate all cells and \"sensitize\" them to a given wavelength of light. The photosensitizer is simply highly absorbent to a given wavelength of light and when excited will produce, in the presence of oxygen, damaging oxygen radicals and singlet oxygen. Bacterial cells are comparatively poor at combatting oxidative stress when compared with human cells therefore a degree of selective toxicity can be achieved with aPDT.In this chapter, we outline methodologies for testing aPDT in vitro using standard lab equipment.

BACKGROUND: Aztreonam-avibactam (ATM-AVI) combination shows promising effectiveness on most carbapenemase-producing Gram-negatives, yet standardized antibiotic susceptibility testing (AST) methods for evaluating the combination in clinical laboratories is lacking. We aimed to evaluate different ATM-AVI AST approaches.
METHODS: 96 characterized carbapenem-resistant clinical isolates belonging to 9 Enterobacterales (EB; n = 80) and P. aeruginosa (PA; n = 16) species, including 90 carbapenemase producers and 72 strains resistant to both CAZ-AVI and ATM, were tested. Paper disk elution (DE; Bio-Rad) and E-test gradient strips stacking (SS; bioMérieux) were performed for the ATM + CAZ-AVI combination. MIC Test Strip (MTS; Liofilchem) was evaluated for ATM-AVI MIC determination. Results were interpreted applying ATM clinical breakpoints of the EUCAST guidelines and compared to the broth microdilution method (Sensititre, Thermofisher).
RESULTS: According to broth microdilution method, 93% of EB and 69% of PA were tested susceptible to ATM-AVI. The synergistic effect of ATM-AVI was of 95% for EB, but of only 17% for PA. The MTS method yielded higher categorical and essential agreement (CA/EA) rates for both EB (89%/91%) and PA (94%/94%) compared to SS, where the rates were 87%/83% for EB and 81%/81% for PA. MTS and SS yielded 2 and 3 major discrepancies, respectively, while 3 very major discrepancies each were observed for both methods. Concerning the DE method, CA reached 91% for EB and 81% for PA, but high number of very major discrepancies were observed for EB (n = 6; 8%) and for PA (n = 3; 19%).
CONCLUSIONS: The ATM-AVI association displayed excellent in vitro activity against highly resistant clinical Enterobacterales strains. MTS method offers accurate ATM-AVI AST results, while the SS method might serve as better alternative then DE method in assessing the efficacy of ATM + CAZ-AVI combination. However, further investigation is needed to confirm the methods\' ability to detect ATM-AVI resistance.

BACKGROUND: With increasing antibiotic resistance and regulation, the issue of antibiotic combination has been emphasised. However, antibiotic combination prescribing lacks a rapid identification of feasibility, while its risk of drug interactions is unclear.
METHODS: We conducted statistical descriptions on 16 101 antibiotic coprescriptions for inpatients with bacterial infections from 2015 to 2023. By integrating the frequency and effectiveness of prescriptions, we formulated recommendations for the feasibility of antibiotic combinations. Initially, a machine learning algorithm was utilised to optimise grading thresholds and habits for antibiotic combinations. A feedforward neural network (FNN) algorithm was employed to develop antibiotic combination recommendation model (ACRM). To enhance interpretability, we combined sequential methods and DrugBank to explore the correlation between antibiotic combinations and drug interactions.
RESULTS: A total of 55 antibiotics, covering 657 empirical clinical antibiotic combinations were used for ACRM construction. Model performance on the test dataset showed AUROCs of 0.589-0.895 for various antibiotic recommendation classes. The ACRM showed satisfactory clinical relevance with 61.54-73.33% prediction accuracy in a new independent retrospective cohort. Antibiotic interaction detection showed that the risk of drug interactions was 29.2% for strongly recommended and 43.5% for not recommended. A positive correlation was identified between the level of clinical recommendation and the risk of drug interactions.
CONCLUSIONS: Machine learning modelling of retrospective antibiotic prescriptions habits has the potential to predict antibiotic combination recommendations. The ACRM plays a supporting role in reducing the incidence of drug interactions. Clinicians are encouraged to adopt such systems to improve the management of antibiotic usage and medication safety.

We investigated colistin heteroresistance in Citrobacter freundii isolates from Korean hospitals. Using population analysis profiling (PAP), we detected colistin heteroresistance in 31.3% of isolates. Among these, ST217 was the most prevalent clone (58.5%), particularly within colistin-heteroresistant isolates (80.0%). Interestingly, the second most common clone, ST248, was not found in heteroresistant isolates. We identified amino acid changes in PhoQ, PmrA, and PmrB, along with mRNA overexpression in pmrB and arnD. Colistin monotherapy showed no efficacy, but a combination of colistin and ciprofloxacin successfully eradicated all five isolates, even at 0.5 × minimum inhibitory concentrations. This study underscores the high prevalence of colistin heteroresistance in C. freundii isolates, limiting the effectiveness of colistin monotherapy. Combining colistin with ciprofloxacin may offer a viable treatment option for C. freundii infections.

BACKGROUND: Previous studies have demonstrated that fidaxomicin, a macrocyclic lactone antibiotic used to treat recurrent Clostridioides difficile-associated diarrhea, also displays potent in vitro bactericidal activity against Clostridium perfringens strains isolated from humans. However, to date, there is no data on the susceptibility to fidaxomicin of C. perfringens strains of animal origin. On the other hand, although combination therapy has become popular in human and veterinary medicine, limited data are available on the effects of antibiotic combinations on C. perfringens. We studied the in vitro response of 21 C. perfringens strains obtained from dogs and cats to fidaxomicin and combinations of fidaxomicin with six other antibiotics.
RESULTS: When tested by an agar dilution method, fidaxomicin minimum inhibitory concentrations (MICs) ranged between 0.004 and 0.032 µg/ml. Moreover, the results of Etest-based combination assays revealed that the incorporation of fidaxomicin into the test medium at a concentration equivalent to half the MIC significantly increased the susceptibility of isolates to metronidazole and erythromycin in 71.4% and 61.9% of the strains, respectively, and the susceptibility to clindamycin, imipenem, levofloxacin, and vancomycin in 42.9-52.4% of the strains. In contrast, ¼ × MIC concentrations of fidaxomicin did not have any effect on levofloxacin and vancomycin MICs and only enhanced the effects of clindamycin, erythromycin, imipenem, and metronidazole in ≤ 23.8% of the tested strains.
CONCLUSIONS: The results of this study demonstrate that fidaxomicin is highly effective against C. perfringens strains of canine and feline origin. Although fidaxomicin is currently considered a critically important antimicrobial that has not yet been licensed for veterinary use, we consider that the results reported in this paper provide useful baseline data to track the possible emergence of fidaxomicin resistant strains of C. perfringens in the veterinary setting.

The fast emergence and spread of drug-resistant infectious pathogens and the resulting increase in associated and attributable deaths is a major health challenge globally. Misuse of antibiotics, insufficient infection prevention and control (IPC) in hospitals, food, animal feed, and environmental contamination due to drug-resistant microbes and genes have been the main drivers for antimicrobial resistance (AMR). AMR can lead to ineffective drug treatment, persistence of infection, and risk of severe disease especially in frail, immunocompromised, elderly patients. It is estimated that AMR will cause around 10 million deaths every year after 2050, the same number of deaths due to cancer occurring every year in present times. AMR affects the progress towards the Sustainable Development Goals (SDGs) and is crucial for pandemic preparedness and response. Therefore, the international authorities such as G7 and G20, the World Bank, the World Health Organization (WHO), the General Assembly of the United Nations, and the European Union call for innovative antibiotics and strategies to combat this health threat. To underline this emergency, two lists of resistant \"priority pathogens\" and a global research agenda for AMR in human health have been published by the WHO. Although investigation of safe and effective treatments remains a top priority, the pipeline for new antimicrobials is not promising, and alternative solutions are needed urgently. In recent times, the interest in fighting AMR has increased, and a number of preventive or therapeutic options have been explored. In this literature review, we discuss the scientific evidence and the limits of the main proven unconventional strategies to combat the AMR phenomenon in the human sector.

Amoxicillin is recommended as primary treatment for community-acquired bacterial pneumonia (CABP). 5-10% of CABP cases are caused by Chlamydia pneumoniae, an obligate intracellular bacterium which responds to beta-lactam antibiotics by converting to a persistent phenotype. To support rational pharmacotherapy of C. pneumoniae infections, we investigated how clinically relevant concentrations of azithromycin and doxycycline affect amoxicillin induced C. pneumoniae persistence. Given the known role of redox state alterations in the action of bactericidal antibiotics and widespread use of redox-active dietary supplements when experiencing respiratory symptoms, we also studied how redox active compounds affect the studied antibiotic treatments. Our data demonstrate that clinically applied amoxicillin concentrations (10 and 25 mg/l) fail to eradicate C. pneumoniae infection in respiratory epithelial cells. Transmission electron microscopy (TEM) of amoxicillin-treated C. pneumoniae infected cells reveal aberrant bacterial morphology characteristic of chlamydial stress response. Amoxicillin was also found to significantly limit the antichlamydial effect of azithromycin or doxycycline. However, based on quantitative culture and quantitative PCR data, azithromycin was superior to doxycycline in C. pneumoniae eradication either as monotherapy or in combination with amoxicillin. Amoxicillin was also found to decrease respiratory epithelial cell glutathione (GSH) levels, whereas redox-active dibenzocyclooctadiene lignans increased C. pneumoniae load in amoxicillin-treated cultures up to two-fold. These data highlight the impact of relative administration time on the efficacy of antichlamydial antibiotics and indicate unfavorable interactions between amoxicillin and redox-active small molecules.