Background and Objectives: Antimicrobial resistance (AMR) is increasing worldwide and imposes significant life-threatening risks to several different populations, especially to those in intensive care units (ICU). The most commonly isolated organisms in ICU comprise gram-negative bacilli (GNB), and these represent a leading cause of serious infections. This study was conducted to describe the prevalence of resistance in GNB isolated from patients in adults, pediatric, and neonatal ICU in a tertiary-care hospital in Mérida, Mexico. Materials and Methods: A retrospective study was done on samples collected in Neonatal (NICU), Pediatric (PICU) and Adult (AICU) ICU of Unidad Médica de Alta Especialidad, Instituto Mexicano del Seguro Social in Mérida, México. The identification of isolates and antimicrobial susceptibility testing were performed using an automated system. Results: A total of 517 GNB strains were isolated. The most common positive culture was bronchial secretions. Pseudomonas aeruginosa was the prevalent pathogen in NICU and PICU, whereas Escherichia coli was common in the AICU. Overall, GNB exhibited a high resistance rates for Ampicillin (95.85%), Cefuroxime (84.17%), Piperacillin (82.93%), Cefotaxime (78.07%), Ceftriaxone (77.41%), Aztreonam (75.23%), Cefazolin (75.00%), and Ceftazidime (73.19%). There are significant differences in the resistance rates of GNB from different ICUs for penicillins, cephalosporins, carbapenems and fluoroquinolones drugs. Escherichia coli (multidrug-resistant [MDR] = 91.57%, highly resistant microorganisms [HRMO] = 90.36%) and Acinetobacter baumannii (MDR = 86.79%, HRMO = 83.02%) exhibited the highest percentage of MDR and HRMO profiles. The prevalence of the extended-spectrum beta-lactamases (ESBL)-producing isolates was 83.13% in E. coli, 78.84% in Klebsiella pneumoniae, and 66.67% in Proteus mirabilis, respectively. Conclusions: The high resistance rates to drugs were exhibited by our GNB isolates. Continuous surveillance and control of the use of antimicrobials are urgently needed to reduce the emergence and spreading of MDR, HRMO, and/or ESBL-producing bacilli.

Staphylococcus aureus infections are prevalent in healthcare and community environments. Methicillin-resistant S. aureus is catalogued as a superbug of high priority among the pathogens. This Gram-positive coccus can form biofilms and produce toxins, leading to persistent infection and antibiotic resistance. Limited effective antibiotics have encouraged the development of innovative strategies, with a particular emphasis on resistance mechanisms and/or virulence factors. Medicinal aromatic plants have emerged as promising alternative sources. This study investigated the antimicrobial, antibiofilm, and antihemolysis properties of three different chemotypes of Lippia origanoides essential oil (EO) against susceptible and drug-resistant S. aureus strains. The chemical composition of the EO was analyzed using GC-MS, revealing high monoterpene concentrations, with carvacrol and thymol as the major components in two of the chemotypes. The third chemotype consisted mainly of the sesquiterpene β-caryophyllene. The MIC values for the two monoterpene chemotypes ranged from 62.5 to 500 µg/mL for all strains, whereas the sesquiterpene chemotype showed activity against seven strains at concentrations of 125–500 µg/mL, which is the first report of its anti-S. aureus activity. The phenolic chemotypes inhibited biofilm formation in seven S. aureus strains, whereas the sesquiterpene chemotype only inhibited biofilm formation in four strains. In addition, phenolic chemotypes displayed antihemolysis activity, with IC₅₀ values ranging from 58.9 ± 3.8 to 128.3 ± 9.2 µg/mL. Our study highlights the importance of L. origanoides EO from the Yucatan Peninsula, which has the potential for the development of anti-S. aureus agents.

Mulinane- and azorellane-type diterpenoids have unique tricyclic fused five-, six-, and seven-membered systems and a wide range of biological properties, including antimicrobial, antiprotozoal, spermicidal, gastroprotective, and anti-inflammatory, among others. These secondary metabolites are exclusive constituents of medicinal plants belonging to the Azorella, Laretia, and Mulinum genera. In the last 30 years, more than 95 mulinanes and azorellanes have been reported, 49 of them being natural products, 4 synthetics, and the rest semisynthetic and biotransformed derivatives. This systematic review highlights the biosynthetic origin, the chemistry, and the pharmacological activities of this remarkably interesting group of diterpenoids.

Urinary tract infections (UTI) are a severe public health problem and are caused mainly by the uropathogenic Escherichia coli (UPEC). Antimicrobial resistance and limited development of new antimicrobials have led to the reuse of old antibiotics such as fosfomycin. The aim of this study was to evaluate the in vitro efficacy of fosfomycin on a collection of multidrug-resistant (MDR) UPEC and the degradative activity on biofilm producers. A total of 100 MDR UPEC clinical isolates were collected from patients at Mexican second- and third-level hospitals. Microorganism identification was performed using an automated system, the evaluation of the susceptibility of clinical isolates to fosfomycin was performed using the resazurin microtiter assay, and the identification of biofilm producers and the effect of fosfomycin in biofilms were evaluated using the crystal violet method. Among planktonic MDR UPEC, 93% were susceptible to fosfomycin. Eighty-three MDR UPEC were categorized as weak (39.8%), moderate (45.2%), and strong (14.5%) biofilm producers. Fosfomycin exhibited degradative activity ranging from 164.4 µg/mL to 1045 µg/mL. Weak producers required statistically lower concentrations of fosfomycin to destroy the biofilm, contrary to moderate and strong producers. In conclusion, fosfomycin could be an option for the treatment of infections caused by MDR UPEC, for which the antimicrobial treatment is more often becoming limited.