Plasmid-borne macrolide resistance in Micrococcus luteus

Microbial richness and air chemistry in aerosols above the PBL confirm 2,000-km long-distance transport of potential human pathogens

The existence of viable human pathogens in bioaerosols which can cause infection or affect human health has been the subject of little research. In this study, data provided by 10 tropospheric aircraft surveys over Japan in 2014 confirm the existence of a vast diversity of microbial species up to 3,000 m height, which can be dispersed above the planetary boundary layer over distances of up to 2,000 km, thanks to strong winds from an area covered with massive cereal croplands in Northeast (NE) Asia. Microbes attached to aerosols reveal the presence of diverse bacterial and fungal taxa, including potential human pathogens, originating from sewage, pesticides, or fertilizers. Over 266 different fungal and 305 bacterial genera appeared in the 10 aircraft transects. Actinobacteria, Bacillota, Proteobacteria, and Bacteroidetes phyla dominated the bacteria composition and, for fungi, Ascomycota prevailed over Basidiomycota. Among the pathogenic species identified, human pathogens include bacteria such as Escherichia coli, Serratia marcescens, Prevotella melaninogenica, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus saprophyticus, Cutibacterium acnes, Clostridium difficile, Clostridium botulinum, Stenotrophomonas maltophilia, Shigella sonnei, Haemophillus parainfluenzae and Acinetobacter baumannii and health-relevant fungi such as Malassezia restricta, Malassezia globosa, Candida parapsilosis and Candida zeylanoides, Sarocladium kiliense, Cladosporium halotolerans, and Cladosporium herbarum. Diversity estimates were similar at heights and surface when entrainment of air from high altitudes occurred. Natural antimicrobial-resistant bacteria (ARB) cultured from air samples were found indicating long-distance spread of ARB and microbial viability. This would represent a novel way to disperse both viable human pathogens and resistance genes among distant geographical regions.

Antimicrobial Effects of Tetraspanin CD9 Peptide against Microbiota Causing Armpit Malodour

Synthetic peptides, including tetraspanin CD9 peptides, are increasingly coming into focus as new treatment strategies against various organisms, including bacteria, that cause underarm odour. The use of deodorants and antiperspirants is associated with side effects. Therefore, it is critical to find an alternative therapeutic approach to combat underarm odour. The aim of this study is to investigate the antibacterial effect of tetraspanin CD9 peptides against the skin microbiota that cause malodour in the underarms. The antimicrobial activity of CD9 peptides against Micrococcus luteus (M. luteus), Bacillus subtilis (B. subtilis), Staphylococcus epidermidis (S. epidermidis), and Corynebacterium xerosis (C. xerosis) was investigated by the disc diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution assays using CD9 peptide concentrations ranging from 1 mg/mL to 0.0078 mg/mL. In addition, the anti-biofilm activity of the CD9 peptides was determined. The CD9 peptides showed different antibacterial activity with an inhibition zone of 7.67, 9.67, 7.00, and 6.00 mm for S. epidermidis, M. luteus, C. xerosis, and B. subtilis, respectively. All bacteria had the same MBC value of 1 mg/mL. A high MIC of CD9 peptides was observed for S. epidermidis and M. luteus at 0.5 mg/mL. The MIC values of B. subtilis and C. xerosis were 0.125 mg/mL and 0.25 mg/mL, respectively. CD9 peptides significantly inhibited biofilm development of S. epidermidis, B. subtilis, and C. xerosis isolates. The CD9 tetraspanin peptide has excellent antibacterial activity against bacteria that cause underarm odour. Therefore, the CD9 tetraspanin peptide is a promising alternative to deodorants and antiperspirants to combat commensal bacteria of the skin that cause underarm odour.

Clinical Characteristics of Patients with Micrococcus luteus Bloodstream Infection in a Chinese Tertiary-Care Hospital

Few pieces of research have focused on Micrococcus luteus bloodstream infection (BSI) because of its low incidence; hence data is needed to illustrate this uncommon infection. This study aimed to explore the clinical characteristics of patients with M. luteus BSI. From January 2010 to December 2019, inpatients that met the criteria for M. luteus BSI were included in this study. Data was collected by reviewing electronic records. Ninety-seven patients were enrolled in this study. Sixty-three percent of the patients have a higher neutrophil percentage (NEUT%). The average blood C-reactive protein (CRP) concentration was 5.5 ± 6.4 mg/dl. 48.5% of the patients had malignancy, and 40.2% underwent invasive surgeries. Linezolid was found to have the largest average diameter of the inhibition zone (36 mm), while erythromycin was found to have the smallest average zone diameter (15 mm). However, some M. luteus strains had a potentially broad antimicrobial resistance spectrum. Cephalosporins (59.2%) and quinolones (21.4%) were the most commonly used antibiotics for empirical therapies. In conclusion, M. luteus BSI mainly happens in immunocompromised patients or those with former invasive surgeries or indwelling catheters. M. luteus strains are less responsive to erythromycin. Cephalosporins and quinolones are effective empirical antibiotics for M. luteus BSI; however, vancomycin and teicoplanin should be considered for potentially broadly drug-resistant M. luteus strains.

Synergistic In Vitro Antimicrobial Activity of Pomegranate Rind Extract and Zinc (II) against Micrococcus luteus under Planktonic and Biofilm Conditions

Infectious diseases caused by microbial biofilms are a major clinical problem, and new antimicrobial agents that can inhibit biofilm formation and eradicate pre-formed biofilms are urgently needed. Pomegranate extracts are a well-established folkloric medicine and have been used in the treatment of infectious diseases since ancient times, whilst the addition of metal ions, including zinc (II), has enhanced the antimicrobial activity of pomegranate. Micrococcus luteus is generally a non-pathogenic skin commensal bacterium, although it can act as an opportunistic pathogen and cause serious infections, particularly involving catheterization and comorbidities. The aims of this study were to evaluate the holistic activity of pomegranate rind extract (PRE), Zn (II), and PRE/Zn (II) individually and in combination against M. luteus under both planktonic and biofilm conditions. Antimicrobial activity was detected in vitro using the broth dilution method, and synergistic activity was determined using checkerboard and time-kill assays. Effects on biofilm formation and eradication were determined by crystal violet and BacLight^TM Live/Dead staining. PRE and Zn (II) exerted antimicrobial activity against M. luteus under both planktonic and biofilm conditions. After 4 h, potent synergistic bactericidal activity was also found when PRE and Zn (II) were co-administered under planktonic conditions (log reductions: PRE 1.83 ± 0.24, Zn (II) 3.4 ± 0.08, and PRE/Zn (II) 6.88 ± 1.02; p < 0.0001). In addition, greater heterogeneity was induced in the structure of M. luteus biofilm using the PRE/Zn (II) combination compared to when PRE and Zn (II) were applied individually. The activity of PRE and the PRE/Zn (II) combination could offer a novel antimicrobial therapy for the treatment of disease-associated infections caused by M. luteus and potentially other bacteria.

Antibiotic resistance genes in the Actinobacteria phylum

The Actinobacteria phylum is one of the oldest bacterial phyla that have a significant role in medicine and biotechnology. There are a lot of genera in this phylum that are causing various types of infections in humans, animals, and plants. As well as antimicrobial agents that are used in medicine for infections treatment or prevention of infections, they have been discovered of various genera in this phylum. To date, resistance to antibiotics is rising in different regions of the world and this is a global health threat. The main purpose of this review is the molecular evolution of antibiotic resistance in the Actinobacteria phylum.

Toxicity of indoxyl derivative accumulation in bacteria and its use as a new counterselection principle

In this work we describe the conditional toxic effect of the expression of enzymes that cleave 5-bromo-4-chloro-3-indolyl (BCI) substrates and its use as a new counterselection principle useful for the generation of clean and unmarked mutations in the genomes of bacteria. The application of this principle was demonstrated in the thermophile Thermus thermophilus HB27 and in a mesophile for which currently no counterselection markers are available, Micrococcus luteus ATCC 27141. For T. thermophilus, the indigogenic substrate BCI-β-glucoside was used in combination with the T. thermophilus β-glucosidase gene (bgl). For M. luteus, a combination of BCI-β-galactoside and the E. coli lacZ gene was implemented. We observed a strong growth-inhibiting effect when the strains were grown on agar plates containing the appropriate BCI substrates, the inhibition being proportional to the substrate concentration and the level of bgl/lacZ expression. The growth inhibition apparently depends on intracellular BCI substrate cleavage and accumulation of toxic indoxyl precipitates. The bgl and lacZ genes were used as counterselection markers for the rapid generation of scar-less chromosomal deletions in T. thermophilus HB27 (both in a Δbgl and in a wild type background) and in M. luteus ATCC 27141. In addition to Thermus and Micrococcus, sensitivity to BCI substrate cleavage was observed for other Gram-negative and Gram-positive species belonging to various bacterial phyla, including representatives of the genera Staphylococcus, Bacillus, Corynebacterium, Rhodococcus, Paracoccus and Xanthomonas. Thus, the toxicity of indoxyl derivative accumulation upon BCI substrate cleavage can be used for selection purposes in a broad range of microorganisms.

Extrachromosomal genetic elements in Micrococcus

Micrococci are Gram-positive G + C-rich, nonmotile, nonspore-forming actinomycetous bacteria. Micrococcus comprises ten members, with Micrococcus luteus being the type species. Representatives of the genus play important roles in the biodegradation of xenobiotics, bioremediation processes, production of biotechnologically important enzymes or bioactive compounds, as test strains in biological assays for lysozyme and antibiotics, and as infective agents in immunocompromised humans. The first description of plasmids dates back approximately 28 years, when several extrachromosomal elements ranging in size from 1.5 to 30.2 kb were found in Micrococcus luteus. Up to the present, a number of circular plasmids conferring antibiotic resistance, the ability to degrade aromatic compounds, and osmotolerance are known, as well as cryptic elements with unidentified functions. Here, we review the Micrococcus extrachromosomal traits reported thus far including phages and the only quite recently described large linear extrachromosomal genetic elements, termed linear plasmids, which range in size from 75 kb (pJD12) to 110 kb (pLMA1) and which confer putative advantageous capabilities, such as antibiotic or heavy metal resistances (inferred from sequence analyses and curing experiments). The role of the extrachromosomal elements for the frequently proven ecological and biotechnological versatility of the genus will be addressed as well as their potential for the development and use as genetic tools.

Antibiotic multiresistance plasmid pRSB101 isolated from a wastewater treatment plant is related to plasmids residing in phytopathogenic bacteria and carries eight different resistance determinants including a multidrug transport system

Ten different antibiotic resistance plasmids conferring high-level erythromycin resistance were isolated from an activated sludge bacterial community of a wastewater treatment plant by applying a transformation-based approach. One of these plasmids, designated pRSB101, mediates resistance to tetracycline, erythromycin, roxythromycin, sulfonamides, cephalosporins, spectinomycin, streptomycin, trimethoprim, nalidixic acid and low concentrations of norfloxacin. Plasmid pRSB101 was completely sequenced and annotated. Its size is 47 829 bp. Conserved synteny exists between the pRSB101 replication/partition (rep/par) module and the pXAC33-replicon from the phytopathogen Xanthomonas axonopodis pv. citri. The second pRSB101 backbone module encodes a three-Mob-protein type mobilization (mob) system with homology to that of IncQ-like plasmids. Plasmid pRSB101 is mobilizable with the help of the IncP-1alpha plasmid RP4 providing transfer functions in trans. A 20 kb resistance region on pRSB101 is located within an integron-containing Tn402-like transposon. The variable region of the class 1 integron carries the genes dhfr1 for a dihydrofolate reductase, aadA2 for a spectinomycin/streptomycin adenylyltransferase and bla(TLA-2) for a so far unknown Ambler class A extended spectrum beta-lactamase. The integron-specific 3'-segment (qacEDelta1-sul1-orf5Delta) is connected to a macrolide resistance operon consisting of the genes mph(A) (macrolide 2'-phosphotransferase I), mrx (hydrophobic protein of unknown function) and mphR(A) (regulatory protein). Finally, a putative mobile element with the tetracycline resistance genes tetA (tetracycline efflux pump) and tetR was identified upstream of the Tn402-specific transposase gene tniA. The second 'genetic load' region on pRSB101 harbours four distinct mobile genetic elements, another integron belonging to a new class and footprints of two more transposable elements. A tripartite multidrug (MDR) transporter consisting of an ATP-binding-cassette (ABC)-type ATPase and permease, and an efflux membrane fusion protein (MFP) of the RND-family is encoded between the replication/partition and the mobilization module. Homologues of the macrolide resistance genes mph(A), mrx and mphR(A) were detected on eight other erythromycin resistance-plasmids isolated from activated sludge bacteria. Plasmid pRSB101-like repA amplicons were also obtained from plasmid-DNA preparations of the final effluents of the wastewater treatment plant indicating that pRSB101-like plasmids are released with the final effluents into the environment.