The study of staphylococci has a long way to go, due to the great significance both for humans and for dairy or companion animals of their large number of virulence factors. Their resistance to ...antibiotics makes these microorganisms become highly pathogenic species that can cause infections ranging from mild to fatal. Staphylococci, especially S. aureus and strains resistant to methicillin (MRSA), are among the most studied microorganisms worldwide. This book covers recent advances in the study of staphylococci. The book is divided into four sections that cover four important events for the study and combat of staphylococci: colonization, epidemiology and pathogenesis, diagnosis, and new treatments. Staphylococci can present a broad spectrum of resistance to antibiotics, which is why their elimination has become difficult. The final section of the book is devoted to new compounds for the fight against staphylococci. We hope that the information contained in this book will be useful for the study and investigation of these medically important microorganisms.
The pathogenicity of Escherichia coli strains that cause cervico-vaginal infections (CVI) is due to the presence of several virulence genes. The objective of this study was to define the variability ...regarding the genotype of antibiotic resistance, the transcription profiles of virulence genes after in vitro infection of the vaginal cell line A431 and the phylogroup composition of a group of cervico-vaginal E. coli strains (CVEC). A total of 200 E. coli strains isolated from Mexican women with CVI from two medical units of the Mexican Institute of Social Security were analysed. E. coli strains and antibiotic resistance genes were identified using conventional polymerase chain reaction (PCR), and phylogroups were identified using multiplex PCR. Virulence gene transcription was measured through reverse-transcriptase real-time PCR after infection of the vaginal cell line A431. The most common antibiotic resistance genes among the CVEC strains were aac(3)II, TEM, dfrA1, sul1, and qnrA. The predominant phylogroup was B2. The genes most frequently transcribed in these strains were fimH, papC, irp2, iroN, kpsMTII, cnf1, and ompT, mainly in CVEC strains isolated from chronic and occasional vaginal infections. The strains showed a large diversity of transcription of the virulence genes phenotype and antibiotic resistance genotype, especially in the strains of phylogroups, B2, A, and D. The strains formed 2 large clusters, which contained several subclusters. The genetic diversity of CVEC strains was high. These strains have a large number of transcription patterns of virulence genes, and one-third of them carry three to seven antibiotic resistance genes.
Heritability and genetic correlations for body weight at harvest size (BW), grow‐out survival (SU), and log‐transformed infectious hypodermal and hematopoietic necrosis virus (IHHNV) load (VLln) in ...Litopenaeus vannamei were estimated. Data were obtained in 2012 from a shrimp breeding population in Mexico using 12,440 shrimp for BW and 16,814 shrimp for SU, and quantitative polymerase chain reaction determinations from 160 full‐sib families were obtained for VLln. DNA was extracted from pooled muscle samples of six shrimp per family for a total of 960 individuals. Heritability estimates for BW, SU, and VLln at the family mean and at individual levels were 0.24 ± 0.08, 0.02 ± 0.01, 0.42 ± 0.45, and 0.08 ± 0.11, respectively. Genetic correlation estimates of BW with SU, BW with VLln, and VLln with SU were 0.40, −0.04, and −0.57, respectively. Our results suggest that VLln has genetic variation and a favorable genetic association with BW and SU. No serious drawbacks were found from selection responses estimated using single‐trait and multitrait indices to increase BW and SU and decrease VLln. Favorable correlated responses for IHHNV tolerance estimated as BW/VLln and SU/VLln were also found. This study offers new insights into the possibility of using IHHNV viral load as a possible selection criterion in L. vannamei breeding programs.
The aim of this study was to characterize the Staphylococcus aureus strains isolated from periodontal lesions of patients, to determine the expression of genes involved in cell adhesion upon their ...infection of human epithelial cells using an in vitro model, its biofilm formation, and its resistance to antibiotics.
S. aureus was analysed by PCR, Kirby–Bauer, and pulsed-field gel electrophoresis (PFGE), measuring gene expression by real-time PCR after infection of human cells in vitro.
S. aureus was identified in 18.6% (50/268) of the samples. All strains (n = 50) possessed the virulence genes spa (Staphylococcal protein A), coa (coagulase), and icaAB (intercellular adhesin); 96% (n = 48) possessed clfB (clumping factor B), and 88% (n = 44) possessed ebps (elastin-binding protein) and sdrD (serine aspartate repeat protein D). All strains were resistant to methicillin, ampicillin, dicloxacillin, cefotaxime, and penicillin, and were multidrug resistant to 6–12 antibiotics. PFGE analysis showed 37 different pulsed-field types and most strains (60.4%) had a unique pulsed-field type. Twenty-four distinct combinations of virulence genes and antibiotic-resistant phenotypes were identified.
Although S. aureus has been considered a transient member of the oral microbiota, our results indicate a high-level expression of virulence genes and multidrug resistance in the strains isolated from periodontal lesions. These strains might complicate the successful treatment of the disease.
Antimicrobial resistance (AMR) represents a serious threat to global health. The development of new drugs to combat infections caused by bacteria resistant to multiple or even all available ...antibiotics is urgent. Most antibiotics used up to date have been identified from soil microorganisms. The marine environment represents an alternative source with great potential for the identification of microorganisms that produce bioactive molecules, including antibiotics. In this study, we analyzed the antibacterial activity of a collection of 82 bacterial strains isolated from marine water and sediment samples collected from the Southwestern Gulf of Mexico. Eight of the marine isolates inhibited the growth of different pathogenic bacteria, seven of which were identified as presumptive Pseudomonas aeruginosa. Interestingly, genome sequencing and phylogenetic analysis revealed that the remaining marine isolate showing antibacterial activity is a novel Pseudomonas species that we denominated Pseudomonas sp. GOM7, which was not pathogenic in the Galleria mellonella infection model in the conditions tested. Notably, Pseudomonas sp. GOM7 inhibited the growth of multidrug and methicillin-resistant strains of the priority pathogen Staphylococcus aureus. Our results show that the anti-S. aureus compound(s) produced by Pseudomonas sp. GOM7 can be extracted from the culture supernatant of this bacterium with the organic solvent ethyl acetate. Annotation of the Pseudomonas sp. GOM7 genome revealed the presence of several biosynthetic gene clusters predicted to code for possible antimicrobial compounds. Our results further highlight the potential of bacteria from the Gulf of Mexico as a source of novel antimicrobials.
The widespread use of mobile phones (MP) among healthcare personnel might be considered as an important source of contamination. One of the most pathogenic bacteria to humans is
, which can be ...transmitted through the constant use of MP. Nevertheless, which specific type of strains are transmitted and which are their sources have not been sufficiently studied. The aim of this study is to determine the source of contamination of MP and characterize the corresponding genotypic and phenotypic properties of the strains found. Nose, pharynx, and MP samples were taken from a group of health science students. We were able to determinate the clonality of the isolated strains by pulsed-field gel electrophoresis (PFGE) and
gene typing (
type). Adhesin and toxin genes were detected, and the capacity of biofilm formation was determined. Several of the MP exhibited strains of
present in the nose and/or pharynx of their owners. methicillin-susceptible
(MSSA), hospital-acquired methicillin-resistant
(HA-MRSA), and community-acquired methicillin-resistant
(CA-MRSA) strains were found, which indicated a variety of genotypes. This study concludes that MP can be contaminated with the strains of
present in the nose and/or pharynx of the owners; these strains can be of different types and there is no dominant genotype.
Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae) (fall armyworm) is a pest native to the Americas that affects a variety of crops. Its control is based on chemical insecticides. However, ...this practice has been associated with changes in the susceptibility of pests to various insecticides. The use of plant products represents an eco-friendly alternative. The objective of this work was to evaluate the larvicidal activity of the chloroform extract of Senna crotalarioides (Kunth) H.S. Irwin & Barneby (Fabaceae) to control S. frugiperda. The chloroform extract of S. crotalarioides caused significant larval mortality, and reduced pupal weight and adult emergence. The analysis by gas chromatography coupled with mass spectrometry (GC-MS) revealed the presence of 22 compounds in the chloroform extract of S. crotalarioides leaves, with the straight-chain aliphatic fatty alcohol 1-octacosanol as the main component. This study revealed that the leaves of S. crotalarioides synthesize long chain alcohols, which increased the mortality of S. frugiperda in its larval stage, including the pupal stage. The extract also caused a decrease in the S. frugiperda pupal weight. The potential use of the chloroform extract obtained from S. crotalarioides and its principal chemical constituent is proposed as a promising alternative to control S. frugiperda.
Nanoparticles based on metal oxides serve as carrier matrices for molecules of biological interest. In this work, we used different copper complexes that were coupled to TiO₂ nanoparticles. ...Nanoparticles were prepared with the sol-gel method. The Cu/TiO₂ nanoparticles were characterized through ultraviolet-visible and Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, nitrogen physisorption analysis, and scanning electron microscopy. Their biological activity was determined through DNA degradation and their cytotoxic effect on HeLa cells. The Cu/TiO₂ nanoparticles presented a pore size between 2 and 6 nm, the size of nanoparticles agglomerates was between 100 and 500 nm. The nanoparticles of Cu/TiO₂ degraded DNA starting at 15 min. The half maximal inhibitory concentration in HeLa cells depends on the used cooper complexes, the kinetics of cell death is of first order. Results revealed that these nanoparticles could be applied in uterine-cervical cancer treatment.
Nanoparticles have multiple applications, among which is their use as antimicrobial agents in aquaculture. The objective of this work was to determine the antibacterial effect of silver nanoparticles ...(AgNPs) against Vibrio fluvialis in cultured angelfish Pterophyllum scalare. AgNPs were synthetized through chemical reduction and characterized by UV-visible and infrared spectroscopy. Particle size ranged from 60 to 170.8 nm, and scanning electron microscopy revealed cubic and spherical forms. A minimal inhibitory concentration of 222.5 ppm was determined, as well as inhibition halos between 8.66 and 14.3 mm. Inhibition of V. fluvialis growth was observed upon contact with AgNPs. An 88% survival of infected fish was obtained when treated with AgNPs, in contrast to 100% mortality of fish that were not treated. No damage to internal or external organs was observed in fish exposed to AgNPs. We conclude that AgNPs exert an antimicrobial effect against V. fluvialis, and thus represent a new alternative to control diseases caused by this microorganism in P. scalare culture.
Healthy carriers of Staphylococcus aureus strains have an important role in the dissemination of this bacterium. To investigate the presence of S. aureus in the throat and anterior nares, samples ...from 1,243 healthy volunteers in a Mexican community were examined. The percentage of healthy carriers was 59.8%. Results showed that colonization of the throat occurred more frequently than that of the nares (46.5% versus 37.1%, P < 0.0001). Of the S. aureus carriers, 22.2% were exclusive nasal carriers and 38% were exclusive throat carriers. A total of 1,039 strains were isolated; 12.6% were shown to be methicillin-resistant S. aureus (MRSA). Of MRSA strains, 32.1% were isolated from exclusive throat carriers. Most of the strains isolated from the anterior nares and throat of the same carriers were the same or related; however, some were different. Pulsed-field gel electrophoresis (PFGE) pattern analysis of the MRSA strains isolated from the exclusive nasal carriers or exclusive throat carriers showed that they belong to different clusters. A 6-year prospective study was performed to investigate the persistence of S. aureus in the throat. Results showed that 13% of subjects were persistent carriers. Most of them were colonized with the same clone of S. aureus throughout the time of the study, and just three had different clones. Antimicrobial susceptibility testing showed that 91.1% of the strains were penicillin resistant. The presence of mecA and nucA genes (in order to confirm methicillin resistance) and of thermostable nuclease of S. aureus was examined. This study showed that some strains of S. aureus regularly colonized the throats of healthy people and could persist for years.
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