Small RNA-mediated regulation of the tet(M) resistance gene expression in Enterococcus faecium

Old Folks, Bad Boon: Antimicrobial Resistance in the Infant Gut Microbiome

The development of the intestinal microbiome in the neonate starts, mainly, at birth, when the infant receives its founding microbial inoculum from the mother. This microbiome contains genes conferring resistance to antibiotics since these are found in some of the microorganisms present in the intestine. Similarly to microbiota composition, the possession of antibiotic resistance genes is affected by different perinatal factors. Moreover, antibiotics are the most used drugs in early life, and the use of antibiotics in pediatrics covers a wide variety of possibilities and treatment options. The disruption in the early microbiota caused by antibiotics may be of great relevance, not just because it may limit colonization by beneficial microorganisms and increase that of potential pathogens, but also because it may increase the levels of antibiotic resistance genes. The increase in antibiotic-resistant microorganisms is one of the major public health threats that humanity has to face and, therefore, understanding the factors that determine the development of the resistome in early life is of relevance. Recent advancements in sequencing technologies have enabled the study of the microbiota and the resistome at unprecedent levels. These aspects are discussed in this review as well as some potential interventions aimed at reducing the possession of resistance genes.

Tetracycline Resistance Genes in the Traditional Swedish Sour Herring surströmming as Revealed Using qPCR

Antibiotic resistance (AR) represents a global concern for human health. To the best of the authors' knowledge, no study addressing AR in surströmming, a traditional Swedish fermented herring, has been performed to date. The aim of the present research was to study the prevalence of tet(O), tet(S), tet(W), tet(K), and tet(M) genes encoding for resistance to tetracycline using quantitative PCR (qPCR) applied to ready-to-eat surströmming samples collected from three producers located in Sweden. The tet(M) gene was found in all the analyzed samples, and it was also the most abundant among the tested tet genes; moreover, tet(O) was the least frequently detected gene. As a general trend, all the analyzed samples showed a high occurrence of the target genes, with slight variations among the producers. A principal component analysis did not reveal any separation among the samples or producers. All the collected data allowed for a drawing of a first picture of the occurrence of tetracycline resistance genes in ready-to-eat surströmming samples. Since no differences among the samples manufactured by the different producers were observed, it is likely that the detected genes were homogeneously spread among the microbial species shared by the herrings used as raw materials. Moreover, it can be hypothesized that the presence of the detected genes was also the result of a selective pressure of the natural marine environment on the herrings' gut microbiota and, hence, on the pro-technological microorganisms responsible for the fermentation of surströmming. However, the contribution of the manufacturers to the contamination of the processed herrings cannot be excluded.

Antimicrobial susceptibilities and mechanisms of resistance of commensal and invasive Mycoplasma salivarium isolates

Mycoplasma salivarium, an oral commensal organism, can cause severe invasive infections in immunocompromised individuals. Currently there is no treatment guidance for such infections. We performed antimicrobial susceptibility tests on 39 commensal and invasive M. salivarium isolates and investigated the mechanisms of antimicrobial resistance. Clindamycin was the most active agent [minimum inhibition concentration (MIC) range: 0.004–128 mg/L, MIC₅₀ = 0.031 mg/L, MIC₉₀ = 0.125 mg/ml], followed by tetracycline and levofloxacin. All isolates were resistant to erythromycin (MIC ≥4 mg/L) due to the presence of 2057A (Escherichia coli numbering) in 23S rRNA. Three isolates with elevated clindamycin MICs (≥8 mg/L) harbored A2058T/G mutations in 23S rRNA gene; four sequential isolates from one patient developed C2611T and A2059G mutations accompanying the increase of clindamycin MICs. Five isolates with elevated tetracycline MICs (≥4 mg/L) had mutations in 16S rRNA gene (A965G/T, G966T, or A967C/T) and one of them harbored TetM. Nine isolates with elevated levofloxacin MICs (≥4 mg/L) had one or more mutations in gyrA, gyrB, parC, or parE. Susceptibility breakpoints for clindamycin, tetracycline and levofloxacin were suggested to be ≤0.125, ≤2, and ≤2 mg/L, respectively. Antimicrobial resistance to any of the three agents (clindamycin, tetracycline, or levofloxacin) was documented in 12 (34.3%) non-duplicate isolates, of which 10 were invasive. Levofloxacin resistance was most frequent (25.7%). Multi-drug resistance was also observed (14.3%). This study demonstrates the frequent occurrence of antimicrobial resistance in M. salivarium, emphasizing the need for culture and susceptibility testing to guide antimicrobial therapy.