The present study describes the development of a green synthesis of silver nanoparticles reduced and stabilized by exuded gum from Anacardium occidentale L. and evaluates in vitro their antibacterial and cytotoxic activities. Characterization of cashew gum-based silver nanoparticles (AgNPs) was carried out based on UV–Vis spectroscopy, transmission electron microscopy and dynamic light scattering analysis which revealed that the synthesized silver nanoparticles were spherical in shape, measuring about 4 nm in size with a uniform dispersal. AgNPs presented antibacterial activity, especially against Gram-negative bacteria, in concentrations where no significant cytotoxicity was observed.

The methicillin resistance of bacteria from the genus Staphylococcus and its ability to form biofilms are important factors in pathogenesis of these microorganisms. Thus, the search for new antimicrobials agents, especially from plants, has been intensified. In this context, Terminalia species have been the subject of research for many pharmacological activities. In this study we evaluated the antibacterial, antibiofilm and cytotoxic activities of the ethanol extract (EtE) from Terminalia fagifolia stem bark as well as that of three fractions of the extract (AqF, HaF and WSF). We determined the minimum inhibitory concentration (MIC) by microdilution in 96-well plates, where the strains were exposed to serial dilutions of the ethanol extract and fractions, ranging from 12.5 to 400 μg/mL. We then determined the minimum bactericidal concentration (MBC), seeding the inoculum (10 μL) with concentrations equal to or greater than the MIC in Mueller-Hinton agar. To test the antibiofilm activity biofilm formation was induced in the presence of concentrations equivalent to 1/2, 1/4 and 1/8 of the MIC extract or fraction tested. In addition, the effect of the EtE and the fractions on cell viability was tested by the MTT assay on human MCF-7 breast cancer and mouse fibroblast NIH/3T3. To obtain high-resolution images of the effect of the aqueous fraction on the bacterial morphology, atomic force microscopy (AFM) imaging of treated S. aureus cells was performed. We observed antibacterial activity of EtE and fractions with MICs ranging from 25–200 μg/mL and MBCs ranging from 200–400 μg/mL. Regarding antibiofilm activity, both the EtE as the AqF, HaF and WSF fractions showed significant inhibition of the biofilm formation, with inhibition of biofilms formation of over 80% for some strains. The EtE and fractions showed a moderate cytotoxicity in cell line NIH/3T3 viability and potential antitumoral activity on human breast cancer cell line MCF-7. The microscopic images obtained revealed morphological changes to the S. aureus ATCC 29213 surface caused by AqF, as well as significant size alterations. The results show potential antibacterial, antibiofilm and antitumoral activities of the ethanol extract and fractions of T. fagifolia.

This study evaluated the microbiological quality of milk and Coalho cheese, the prevalence of enterotoxin genes, antimicrobial resistance and determined an inducible MLSB resistance phenotype by the D-test in strains of Staphylococcus aureus isolated from these products. Seventy samples of milk and Coalho cheese were analyzed. S. aureus strains were identified by biochemical tests. The presence of se genes (sea-see) was tested by polymerase chain reaction. The antimicrobial sensitivity of S. aureus strains was evaluated for 13 antimicrobial drugs using the disk diffusion technique and the double-disk diffusion test (D-test) was performed to determine inducible resistance to lincosamide phenotype. The amount of toxin sufficient to cause foodborne diseases is generally observed when Staphylococcus populations exceed 105 CFU mL-1 g-1. In this study, none of the milk samples analyzed showed these counts; however, 73.3% (22/30) of Coalho cheese samples exceeded this value. A total of 109 isolates were identified as S. aureus. The presence of enterotoxin genes was detected in 25.7% of these isolates and amplified only for the sec gene. Most of the isolates (78.5%) were resistant to one or more antimicrobial agents. The D test showed that 25.0% of erythromycin-resistant isolates had the constitutive resistance phenotype, and 3.8% had the inducible resistance phenotype to clindamycin. These results indicate that these dairy products represent a health risk since these bacteria can cause foodborne diseases or may be a possible route for the transfer of antimicrobial resistance to humans.

The emergence of livestock-associated methicillin-resistant Staphylococcus aureus strains (LA-MRSA) and the potential role of pigs in the evolution of these strains has led to increased interest in research of these microorganisms. However, this has contributed to a lack of research in the isolation and characterization of methicillin-susceptible S. aureus strains (MSSA). In this study, the prevalence of S. aureus in pigs in the nursery and finishing stages were analyzed. The susceptibility profiles to antibiotics, tolerance to heavy metals, and biofilm production of the isolates were evaluated using phenotypic and genotypic techniques. A total of 1,250 colonies suggestive of Staphylococcus spp. were isolated from 128 pigs, of which 63.6% (n = 795) belonged to this microbial genus. Sixty-seven colonies isolated from 34 animals (26.5%) were confirmed as S. aureus (8.4%). No strains resistant to copper, zinc, or methicillin were detected; however, all strains presented a resistance profile to at least three different classes of antimicrobials and 21 produced biofilms. These data are of concern, as they indicate the need for increased surveillance in the use of antimicrobials as well as reinforce the importance of studies on MSSA strains.

Streptococcal bacteremia that occurs during invasive dental procedures can lead to infective endocarditis (IE) in children with certain heart diseases. Prior to such procedures, antibiotic prophylaxis (AP) with amoxicillin (AMPC) is recommended. However, the detection of amoxicillin-resistant strains (AMPC-RS) in the mouths of children with heart diseases raises the concern that they would be uncovered by the action of standard AP. This work carried out a systematic review and meta-analysis regarding AMPC-RS carriage in the mouths of children. We consulted databases covering studies between the years 2000 and 2021, following the PRISMA declaration. A meta-analysis was carried out to assess the prevalence of children carrying AMPC-RS in the mouths. The antimicrobial tests were carried out by microdilution (46.2% of articles), disk diffusion (38.3%), and the E-test (15.4%). Streptococcus mitis and S. sanguinis were bacteria with the most found resistance phenotype, with MIC reaching values of 128 µg/mL. Of the 13 selected articles, only 6 presented results that made it possible to calculate the prevalence of children carrying AMPC-RS in their mouths, ranging from 5.5% to 86.3%. Most of the studies were classified as high quality, and the collected data demonstrate the presence of streptococcal strains with different levels of resistance in the collected samples, such as the dental plaque. The meta-analysis pointed to evidence of AMPC-RS being carried, with a prevalence of 21.3% (I² = 0%, p = 0.705). There is an important prevalence of AMPC-RS carriage in the mouths of children. Specific attention should be directed to AP in those susceptible to IE.