Molecular basis of resistance to macrolides, lincosamides and streptogramins in Staphylococcus hominis strains isolated from clinical specimens

Harnessing advances in mechanisms, detection, and strategies to combat antimicrobial resistance

Antimicrobial resistance (AMR) is a growing global health crisis, threatening the effectiveness of antibiotics and other antimicrobial agents, leading to increased morbidity, mortality, and economic burdens. This review article provides a comprehensive analysis of AMR, beginning with a timeline of antibiotics discovery and the year of first observed resistance. Main mechanisms of AMR in bacteria, fungi, viruses, and parasites are summarized, and the main mechanisms of bacteria are given in detail. Additionally, we discussed in detail methods for detecting AMR, including phenotypic, genotypic, and advanced methods, which are crucial for identifying and monitoring AMR. In addressing AMR mitigation, we explore innovative interventions such as CRISPR-Cas systems, nanotechnology, antibody therapy, artificial intelligence (AI), and the One Health approach. Moreover, we discussed both finished and ongoing clinical trials for AMR. This review emphasizes the urgent need for global action and highlights promising technologies that could shape the future of AMR surveillance and treatment. By integrating interdisciplinary research and emerging clinical insights, this study aims to guide individuals toward impactful solutions in the battle against AMR.

The prevalence of multidrug resistance in Staphylococcus hominis isolated from clinical materials

The treatment of infections caused by Staphylococcus hominis remains a challenge, mainly due to the increasing resistance of these bacteria to antibiotics. The aim of the study was to determine antibiotic resistance in 62 strains S. hominis isolated from clinical materials, and to identify the molecular basis of resistance to antibiotics. Forty-six strains were both methicillin-resistant and harbored the mecA gene. Twenty-three of these strains had mec complex A and ccr complex AB1. Such a combination of the mec and ccr complexes does not correspond to any cassettes that have been demonstrated so far. However, over 80% of the tested strains were multidrug-resistant, of which as many as 12 were resistant to at least seven antibiotics. More than a half of strains harbored the tetK, acc(6')-Ie aph(2''), and ant(4')-I genes. erm(C) was the most common resistant gene to antibiotics from the MLS group. Two strains had as many as five antibiotic resistance genes from the tested groups (erm(C), msr(A), msr(B), mph(C), lnu(A)). The presence of the vga gene encoding resistance to streptogramins A was detected in one strain. All of strains were sensitive to vancomycin. However, 11 of them had reduced sensitivity to this antibiotic and eight of them were characterized by a heterogeneous resistance profile to this antibiotic. Our results clearly shows increasing threat of S. hominis caused by their multi-resistance. Moreover, these bacteria can constitute a reservoir of resistance genes for more pathogenic bacteria.

Novel natural and economic approach for controlling methicillin-resistant Staphylococcus aureus using apple cider vinegar

Methicillin-resistant Staphylococcus aureus (MRSA) constitutes a significant health concern because it promotes infectious mastitis in dairy animals and poses a hazard risk to humans. Controlling MRSA infections is a growing challenge on a global scale because of the bacteria's toxicity and its capacity to develop multidrug resistance (MDR). Combating against MDR bacteria and the spread of infectious diseases needs natural antibacterial alternatives to minimize the economic losses of mastitis. The average treatment cost in Egypt was highlighted. The antibacterial effect of apple cider vinegar (ACV) against MDR-MRSA isolates was evaluated, also the study aimed at profiling antimicrobial resistance genes in MRSA isolates. The incidence of mastitis in cows was more than in buffaloes, and the average total treatment cost was estimated at 82 million EGP from 2016 to 2021 (around 14 million EGP annually). Of the 22 S. aureus isolates (20 %), of which (59.1 % were from cows and 40.9 % from buffaloes), 19 (86.4 %) were confirmed as MRSA. All MRSA isolates exhibited resistance to clindamycin (94.7 %), then both ampicillin and doxycycline (84.2 %), and ampicillin and sulbactam, erythromycin and Fosfomycin (each, 78.9 %). Vancomycin, ciprofloxacin, and levofloxacin can be used to treat MRSA. The prevalence of MDR was significantly high, with 94.7 % of the cases having multiple antimicrobial resistance (MAR) indices ranging from 0.25 to 0.75. All MRSA isolates tested positive for mecA, 89.5 % for the blaZ gene, 84.2 % for tetM, and 73.4 % for ermB. In vitro, the antibacterial properties of ACV were demonstrated to be superior by our results which demonstrate a zone of inhibition with diameters ranging from 20 to 40 mm detected by Agar well diffusion technique and MIC's (Minimal Inhibitory Concentration) ranging from 2 to 4 μg/ml. Some isolates possess MBC (Minimal Bactericidal Concentration) values at the same MIC. This research proposes the potential of ACV to act as a promising antibacterial alternative against MRSA. This can help minimize the health problem of antibiotic-resistant bacteria and improve the efficiency of dairy farms. Further studies are recommended to determine the proper dosage for field administration.

Alteration of indicator gut microbiota in patients with chronic sinusitis

BACKGROUND

Many factors influence the composition of the sinus microflora. The microbial balance is most disturbed by the use of antibacterial agents. Superinfections caused by more than one pathogen may then occur. Despite treatment, including surgery and long-term antibiotic therapy, many patients with sinusitis do not experience significant relief from their symptoms. It has been hypothesized that an imbalance in the gut microbiota may also be responsible for the chronicity of sinusitis. Our goal was therefore to identify selected gut indicator bacteria that play a role in immunity in patients with chronic sinusitis. In addition, compare the number of selected bacteria in two groups of patients: with chronic sinusitis and with chronic rhinosinusitis (CRS) with concomitant diseases and/or symptoms other than CRS.

RESULTS

Significantly decreased numbers of Bifidobacterium spp. and Faecalibacterium prauznitzi bacteria were observed in patients from the G1 group. The majority of patients from this group (12 out of 13) had a significantly decreased number of Bifidobacterium and Akkermansia muciniphila bacteria, which are involved in the nutrition and regeneration of gut epithelium cells and have anti-inflammatory properties. In group G2 (patients with chronic sinusitis and symptoms of comorbidities) a decreased number of F. prausnitzii, Bifidobacterium spp., A. muciniphila and Lactobacillus spp. bacteria was observed. A small percentage of patients in this group showed overgrowth of yeast-like fungi.

CONCLUSION

Although the more research is needed, possibly the gut microbiota indicator bacteria number analyses might enable to plan personalized prebiotic and probiotic treatment, which could support intestine microbiota and mucosal immunity patients suffering from chronic sinusitis.

Antibiotic resistance and mecA characterization of Staphylococcus hominis from filarial lymphedema patients in the Ahanta West District, Ghana: A cross-sectional study

Background and Aim

Filarial infections affect over 150 million people in the tropics. One of the major forms of filarial pathologies is lymphedema; a condition where the immune response is significantly altered, resulting in changes in the normal flora. Staphylococcus hominis, a human skin commensal, can also be pathogenic in immunocompromised individuals. Therefore, there is the possibility that S. hominis could assume a different behavior in filarial lymphedema patients. To this end, we investigated the levels of antibiotic resistance and extent of mecA gene carriage in S. hominis among individuals presenting with filarial lymphedema in rural Ghana.

Method

We recruited 160 individuals with stages I-VII lymphedema, in a cross-sectional study in the Ahanta West District of the Western Region of Ghana. Swabs from lymphedematous limb ulcers, pus, and cutaneous surfaces were cultured using standard culture-based techniques. The culture isolates were subjected to Matrix-Assisted Laser Desorption/Ionization Time of Flight (MALDI-TOF) mass spectrometry for bacterial identification. Antimicrobial susceptibility testing (AST) was performed using the Kirby-Bauer method. mecA genes were targeted by polymerase chain reaction for strains that were cefoxitin resistant.

Results

In all, 112 S. hominis were isolated. The AST results showed resistance to chloramphenicol (87.5%), tetracycline (83.3%), penicillin (79.2%), and trimethoprim/sulphamethoxazole (45.8%). Of the 112 strains of S. hominis, 51 (45.5%) were resistant to cefoxitin, and 37 (72.5%) of the cefoxitin-resistant S. hominis haboured the mecA gene.

Conclusion

This study indicates a heightened level of methicillin-resistant S. hominis isolated among filarial lymphedema patients. As a result, opportunistic infections of S. hominis among the already burdened filarial lymphedema patients in rural Ghana may have reduced treatment success with antibiotics.

Rapid methicillin resistance detection and subspecies discrimination in Staphylococcus hominis clinical isolates by MALDI-TOF MS

PURPOSE

Staphylococcus hominis is a coagulase-negative opportunistic pathogen responsible for implanted medical device infections. Rapid identification and virulence factors detection are crucial for appropriate antimicrobial therapy. We aimed to search protein biomarker peaks for rapid classification of antibiotic resistance and subspecies of S. hominis using MALDI-TOF MS.

METHODS

S. hominis clinical isolates (n = 148) were screened for subspecies differentiation by novobiocin resistance. Biofilm composition and formation were determined by detachment assay and crystal violet staining, respectively. Antibiotic susceptibility was performed by the broth microdilution method. The search for potential biomarkers peaks was enabled by ClinProTools 3.0, flexAnalysis 3.4, and Biotools 3.2 for statistical analysis, peak visualization, and protein/peptide alignment, respectively.

RESULTS

Of 148 isolates, 12.16% were classified as S. hominis subsp. novobiosepticus, 77.77% were biofilm producers, and ˃ 50% were multidrug-resistant. Two potential biomarker peaks, 8975 m/z and 9035 m/z were detected for the discrimination of methicillin resistance with a sensitivity of 96.72%. The following peaks were detected for subspecies differentiation: 2582 m/z, 2823 m/z, and 2619 m/z with 88.89-98.28% of sensitivity.

CONCLUSIONS

We found potential biomarker peaks to predict methicillin resistance and discriminate S. hominis subspecies during routine MALDI-TOF MS identification in a clinical setting to enable better antibiotic treatment.

Comparative Genomic Analysis of a Multidrug-Resistant Staphylococcus hominis ShoR14 Clinical Isolate from Terengganu, Malaysia, Led to the Discovery of Novel Mobile Genetic Elements

Staphylococcus hominis is a coagulase-negative Staphylococcus (CoNS) commensal capable of causing serious systemic infections in humans. The emergence of multidrug-resistant S. hominis strains is of concern but little is known about the characteristics of this organism, particularly from Malaysia. Here, we present the comparative genome analysis of S. hominis ShoR14, a multidrug-resistant, methicillin-resistant blood isolate from Terengganu, Malaysia. Genomic DNA of S. hominis ShoR14 was sequenced on the Illumina platform and assembled using Unicycler v0.4.8. ShoR14 belonged to sequence type (ST) 1 which is the most prevalent ST of the S. hominis subsp. hominis. Comparative genomic analysis with closely related strains in the database with complete genome sequences, led to the discovery of a novel variant of the staphylococcal chromosome cassette mec (SCCmec) type VIII element harboring the mecA methicillin-resistance gene in ShoR14 and its possible carriage of a SCCfus element that encodes the fusidic acid resistance gene (fusC). Up to seven possible ShoR14 plasmid contigs were identified, three of which harbored resistance genes for tetracycline (tetK), chloramphenicol (catA7), macrolides, lincosamides, and streptogramin B (ermC). Additionally, we report the discovery of a novel mercury-resistant transposon, Tn7456, other genomic islands, and prophages which make up the S. hominis mobilome.

Importance of Microbiome of Fecal Samples Obtained from Adolescents with Different Weight Conditions on Resistance Gene Transfer

Antimicrobial resistance (AMR) is a relevant public health problem worldwide, and microbiome bacteria may contribute to the horizontal gene transfer associated with antimicrobial resistance. The microbiome of fecal samples from Mexican adolescents were analyzed and correlated with eating habits, and the presence of AMR genes on bacteria in the microbiome was evaluated. Fecal samples from adolescents were collected and processed to extract genomic DNA. An Illumina HiSeq 1500 system was used to determine resistance genes and the microbiome of adolescents through the amplification of gene resistance and the V3–V4 regions of RNA, respectively. Analysis of the microbiome from fecal samples taken from 18 obese, overweight, and normal-weight adolescents revealed that the Firmicutes was the most frequent phylum, followed by Bacteroidetes, Actinobacteria, Proteobacteria and Verrucomicrobia. The following species were detected as the most frequent in the samples: F. prausnitzii, P. cori, B. adolescentis, E. coli and A. muciniphila. The presence of Bacteroides, Prevotella and Ruminococcus was used to establish the enterotype; enterotype 1 was more common in women and enterotype 2 was more common in men. Twenty-nine AMR genes were found for β-lactamases, fluoroquinolones, aminoglycosides, macrolide, lincosamides, streptogramin (MLS), tetracyclines and sulfonamides. The presence of microorganisms in fecal samples that harbor AMR genes that work against antimicrobials frequently used for the treatment of microbial infections such as b-lactams, macrolides, aminoglycosides, MLS, and tetracyclines is of great concern, as these organisms may be an important reservoir for horizontal AMR gene transfer.

Identifying gram-positive cocci in dermatoscopes and smartphone adapters using MALDI-TOF MS: a cross-sectional study

Background

The increasingly frequent use of dermoscopy makes us think about the possibility of transfer of microorganisms, through the dermatoscope, between doctor and patients.

Objectives

To identify the most frequent gram-positive cocci in dermatoscopes and smartphone adapters, as well as the resistance profile, and to evaluate the factors associated with a higher risk of bacterial contamination of the dermatoscopes.

Methods

A cross-sectional study was carried out with 118 dermatologists from Porto Alegre/Brazil between September 2017 and July 2018. Gram-positive cocci were identified by MALDI-TOF MS and habits of use of the dermatoscope were evaluated through an anonymous questionnaire.

Results

Of the dermatoscopes analysed, 46.6% had growth of gram-positive cocci on the lens and 37.3% on the on/off button. The microorganisms most frequently found were S. epidermidis, S. hominis and S. warneri. Attending a hospital, using the dermatoscope at the hospital, with inpatients and in the intensive care unit were significantly associated with colonisation by gram-positive cocci. The highest resistance rates were observed for penicillin, erythromycin and sulfamethoxazole-trimethoprim.

Study limitations

The non-search of gram-negative bacilli, fungi and viruses. Moreover, the small number of adapters did not make it possible to better define if the frequency differences were statistically significant.

Conclusion

Coagulase-negative staphylococci were frequently identified. S. aureus was detected only on the lens.

Differences in distribution of MLS antibiotics resistance genes in clinical isolates of staphylococci belonging to species: S. epidermidis, S. hominis, S. haemolyticus, S. simulans and S. warneri

Background

Macrolides and lincosamides are two leading types of antibiotics commonly used in therapies. The study examines the differences in resistance to these antibiotics and their molecular bases in S. epidermidis as well as in rarely isolated species of coagulase-negative staphylococci such as S. hominis, S. haemolyticus, S. warneri and S. simulans. The isolates were tested for the presence of the erm(A), erm(B), erm(C), lnu(A), msr(A), msr(B), mph(C), ere(A) and ere(B) genes. Phenotypic resistance to methicillin and mecA presence were also determined.

Results

The MLS_B resistance mechanism was phenotypically found in isolates of species included in the study. The most prevalent MLS_B resistance mechanism was observed in S. hominis, S. haemolyticus and S. epidermidis isolates mainly of the MLS_B resistance constitutive type. Macrolide, lincosamide and streptogramin B resistance genes were rarely detected in isolates individually. The erm(B), ere(A) and ere(B) genes were not found in any of the strains. The erm(A) gene was determined only in four strains of S. epidermidis and S. hominis while lnu(A) was seen in eight strains (mainly in S. hominis). The erm(C) gene was present in most of S. epidermidis strains and predominant in S. hominis and S. simulans isolates. The examined species clearly differed between one another in the repertoire of accumulated genes.

Conclusions

The presence of genes encoding the MLS_B resistance among CoNS strains demonstrates these genes’ widespread prevalence and accumulation in opportunistic pathogens that might become gene reservoir for bacteria with superior pathogenic potential.

Antibiotic resistance profiles of coagulase-positive and coagulase-negative staphylococci from pit latrine fecal sludge in a peri-urban South African community

The aim of this study was to assess pit latrine samples from a peri-urban community in KwaZulu-Natal (South Africa) for the presence of multidrug-resistant (MDR) Staphylococcus spp. Standard procedures were used to isolate Staphylococcus spp. from pit latrine fecal sludge samples, with confirmation at genus level by polymerase chain reaction (PCR). Sixty-eight randomly selected pit latrine Staphylococcus spp. isolates were further characterized by using established disk diffusion procedures. An average Staphylococcus spp. count of 2.1 × 105 CFU per g fecal material was established using two randomly selected pit latrine samples. Of the 68-selected Staphylococcus spp. pit latrine isolates, 49% were identified as coagulase positive, 51% as coagulase negative and 65% (12 coagulase positive, 32 coagulase negative isolates) were categorized as MDR. The majority (66/68) of Staphylococcus spp. isolates displayed resistance to fusidic acid while only 5/68 isolates displayed resistance to chloramphenicol. The pit latrine samples analyzed in this study are a source of MDR Staphylococcus spp., highlighting the need for proper hygiene and sanitation regimes in rural communities using these facilities.

Small mammals as sentinels of antimicrobial-resistant staphylococci

A total of 39 coagulase-negative staphylococci and seven Staphylococcus aureus strains were isolated from small mammal feces, i.e., the striped field mouse (Apodemus agrarius) and the yellow-necked mouse (A. flavicollis) in two sampling areas, deciduous forest and karst plains. MALDI-TOF analysis revealed five species of coagulase-negative staphylococci: S. sciuri, S. hominis, S. warneri, S. haemolyticus, and S. xylosus. All strains were susceptible to tetracycline, linezolid, vancomycin, and teicoplanin. Three MRSA strains with the mecA gene were detected. The beta-lactamase gene blaZ was detected in ampicillin-resistant staphylococci and in the high-level resistant strains (oxacillin over 2 mg/L) mecA gene. The mecC gene was not detected by PCR. Erythromycin-resistant staphylococci harbored the ermC gene and/or the efflux gene msrA. There were no detectable dfr genes in trimethoprim-resistant staphylococci and the rifampicin-resistant strains were without mutation in the rpoB gene. In summary, wild small mammals may serve as sentinels of mecA-positive S. aureus with erythromycin resistance genes ermC and efflux msrA. Small mammals appear to be useful indicators of antibiotic resistance.

Multifactorial mechanisms of the pathogenesis of methicillin-resistant Staphylococcus hominis isolated from bloodstream infections

Staphylococcus hominis is a species of the coagulase-negative staphylococci. It has been designated as a potential pathogen but so far the pathogenic mechanisms of this bacterium have not been determined. We studied 30 clinical isolates of methicillin-resistant S. hominis, which were previously examined for biofilm forming properties. The results of this study revealed that all these S. hominis strains had the ability to adhere to HeLa cells. Over 40% of the S. hominis strains invaded epithelial cells. The invasion index ranged from 0 to 41.5%. All isolates exhibited the cytotoxic activity of extracellular factors, which caused the destruction of epithelial cells. More than 90% of these methicillin-resistant strains contained at least one aminoglycosides resistance gene. The ant(4′)-I gene was found in 63% of the isolates, aac(6′)/aph(2″) in 20% and aph(3′)-IIIa in 47%. Two strains were assigned to SCCmec type VIII and three to SCCmec type III. The remaining isolates (83%) harboured a non-typeable SCCmec type. The mec complex A was predominant in this species. The results indicate that the pathogenicity of S. hominis may be multifactorial, involving adhesion, invasion and the activity of extracellular toxins, which cause damage to the host epithelium.

Prevalence of Genotypes That Determine Resistance of Staphylococci to Macrolides and Lincosamides in Serbia

Macrolides, lincosamides, and streptogramins (MLS) resistance genes are responsible for resistance to these antibiotics in Staphylococcus infections. The purpose of the study was to analyze the distribution of the MLS resistance genes in community- and hospital-acquired Staphylococcus isolates. The MLS resistance phenotypes [constitutive resistance to macrolide–lincosamide–streptogramin B (cMLSb), inducible resistance to macrolide–lincosamide–streptogramin B (iMLSb), resistance to macrolide/macrolide–streptogramin B (M/MSb), and resistance to lincosamide–streptogramin A/streptogramin B (LSa/b)] were determined by double-disc diffusion method. The presence of the MLS resistance genes (ermA, ermB, ermC, msrA/B, lnuA, lnuB, and lsaA) were determined by end-point polymerase chain reaction in 179 isolates of staphylococci collected during 1-year period at the Center for Microbiology of Public Health Institute in Vranje. The most frequent MLS phenotype among staphylococcal isolates, both community-acquired and hospital-acquired, was iMLSb (33.4%). The second most frequent was M/MSb (17.6%) with statistically significantly higher number of hospital-acquired staphylococcal isolates (p < 0.05). MLS resistance was mostly determined by the presence of msrA/B (35.0%) and ermC (20.8%) genes. Examined phenotypes were mostly determined by the presence of one gene, especially by msrA/B (26.3%) and ermC (14.5%), but 15.6% was determined by a combination of two or more genes. M/MSb phenotype was the most frequently encoded by msrA/B (95.6%) gene, LSa/b phenotype by lnuA (56.3%) gene, and iMLSb phenotype by ermC (29.4%) and ermA (25.5%) genes. Although cMLSb phenotype was mostly determined by the presence of ermC (28.9%), combinations of two or more genes have been present too. This pattern was particularly recorded in methicillin-resistant Staphylococcus aureus (MRSA) (58.3%) and methicillin-resistant coagulase-negative staphylococci (MRCNS) (90.9%) isolates with cMLSB phenotype. The msrA/B gene and M/MSb phenotype were statistically significantly higher in hospital-acquired than community-acquired staphylococci strains (p < 0.05). There are no statistically significant differences between staphylococci harboring the rest of MLS resistance genes acquired in community and hospital settings (p > 0.05). The prevalence of iMLSb phenotypes may change over time, so it is necessary to perform periodic survey of MLS resistance phenotypes, particularly where the D-test is not performed routinely.

Identification of Emerging Human Mastitis Pathogens by MALDI-TOF and Assessment of Their Antibiotic Resistance Patterns

Lactational mastitis constitutes one of the main causes of undesired weaning, depriving the mother–infant pair from the benefits of breastfeeding; therefore, this condition should be considered a relevant public health issue. The role of specific microorganisms remains unclear since human milk cultures and antibiotic susceptibility testing (AST) are not routinely performed, despite the fact that this would be key to ensure an early and effective diagnosis and treatment. The objective of this study was to describe the culturable microbial diversity in 647 milk samples from breastfeeding women with clinical symptoms of mastitis by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF) VITEK MS technology and to analyze the antimicrobial susceptibility profiles of a collection of isolates from these samples by the VITEK 2 AST system. Staphylococcus epidermidis was the most common species isolated from mastitis samples (87.6%), while Staphylococcus aureus was detected in 22.1%. Streptococci constituted the second (68.6%) most prevalent bacterial group, with Streptococcus mitis/oralis, Streptococcus salivarius, and Streptococcus parasanguinis detected with frequencies of 40.8, 36.8, and 14.4%, respectively. The antibiotic susceptibility profiles of 642 staphylococcal isolates indicated a remarkable resistance to benzylpenicillin (88.3%) and erythromycin (67.3%) with differences between species. A high percentage of Staphylococcus isolates were resistant to at least one antibiotic (Staphylococcus hominis, 100%; S. epidermidis, 98.2%; S. aureus, 92.9%; Staphylococcus lugdunensis, 90.5%) and the percentage of multidrug-resistance (MDR) isolates was noticeable (S. hominis, 81%; S. epidermidis, 64.4%; S. aureus, 11.5%; S. lugdunensis, 10.5%). In relation to streptococcal isolates (n = 524), AST revealed high or moderate percentages of resistance to erythromycin (68.7%), benzylpenicillin (63.7%), ampicillin (51.5%), and tetracycline (30.8%). Antibiotic resistance to at least one antibiotic was detected in 97.6% of S. parasanguinis, 92.6% of S. salivarius, 83.3% of S. mitis/oralis, and 72.4% of Streptococcus vestibularis isolates. A significant number of MDR streptococcal isolates was also found (S. parasanguinis, 51.2%; S. salivarius, 39.3%; S. mitis/oralis, 34.6%; and S. vestibularis, 19%). The results highlight the important role of coagulase-negative staphylococci and streptococci as human mastitis-causing agents. Moreover, the high rates of antimicrobial resistance among these microorganisms must be contemplated as an issue of clinical relevance in relation to treatment options.

Metabolic activity, urease production, antibiotic resistance and virulence in dual species biofilms of Staphylococcus epidermidis and Staphylococcus aureus

In this paper, the metabolic activity in single and dual species biofilms of Staphylococcus epidermidis and Staphylococcus aureus isolates was investigated. Our results demonstrated that there was less metabolic activity in dual species biofilms compared to S. aureus biofilms. However, this was not observed if S. aureus and S. epidermidis were obtained from the same sample. The largest effect on metabolic activity was observed in biofilms of S. aureus Mu50 and S. epidermidis ET-024. A transcriptomic analysis of these dual species biofilms showed that urease genes and genes encoding proteins involved in metabolism were downregulated in comparison to monospecies biofilms. These results were subsequently confirmed by phenotypic assays. As metabolic activity is related to acid production, the pH in dual species biofilms was slightly higher compared to S. aureus Mu50 biofilms. Our results showed that S. epidermidis ET-024 in dual species biofilms inhibits metabolic activity of S. aureus Mu50, leading to less acid production. As a consequence, less urease activity is required to compensate for low pH. Importantly, this effect was biofilm-specific. Also S. aureus Mu50 genes encoding virulence-associated proteins (Spa, SplF and Dps) were upregulated in dual species biofilms compared to monospecies biofilms and using Caenorhabditis elegans infection assays, we demonstrated that more nematodes survived when co-infected with S. epidermidis ET-024 and S. aureus mutants lacking functional spa, splF or dps genes, compared to nematodes infected with S. epidermidis ET-024 and wild- type S. aureus. Finally, S. epidermidis ET-024 genes encoding resistance to oxacillin, erythromycin and tobramycin were upregulated in dual species biofilms and increased resistance was subsequently confirmed. Our data indicate that both species in dual species biofilms of S. epidermidis and S. aureus influence each other’s behavior, but additional studies are required necessary to elucidate the exact mechanism(s) involved.

Draft Genome Sequence of Staphylococcus hominis BHG17 Isolated from Wild Bar-Headed Goose (Anser indicus) Feces

Staphylococcus hominis belongs to a group of coagulase-negative staphylococci and is an opportunistic pathogen, usually found on the skin and mucous membranes. Studies involving S. hominis isolated from wild birds are scarce. Here, we report a 2.365-Mb draft genome sequence of S. hominis BHG17, isolated from the feces of a bar-headed goose.

Lincosamides: Chemical structure, biosynthesis, mechanism of action, resistance, and applications

Lincomycin and its derivatives are antibiotics exhibiting biological activity against bacteria, especially Gram-positive ones, and also protozoans. Lincomycin and its semi-synthetic chlorinated derivative clindamycin are widely used in clinical practice. Both antibiotics are bacteriostatic, inhibiting protein synthesis in sensitive bacteria; however, at higher concentrations, they may be bactericidal. Clindamycin is usually much more active than lincomycin in the treatment of bacterial infections, in particular those caused by anaerobic species; it can also be used for the treatment of important protozoal diseases, e.g. malaria, most effectively in combination with other antibiotic or non-antibiotic antimicrobials (primaquine, fosfidomycin, benzoyl peroxide). Chemical structures of lincosamide antibiotics and the biosynthesis of lincomycin and its genetic control have been summarized and described. Resistance to lincomycin and clindamycin may be caused by methylation of 23S ribosomal RNA, modification of the antibiotics by specific enzymes or active efflux from the bacterial cell.

Resistance to Macrolide Antibiotics in Public Health Pathogens

Macrolide resistance mechanisms can be target-based with a change in a 23S ribosomal RNA (rRNA) residue or a mutation in ribosomal protein L4 or L22 affecting the ribosome's interaction with the antibiotic. Alternatively, mono- or dimethylation of A2058 in domain V of the 23S rRNA by an acquired rRNA methyltransferase, the product of an erm (erythromycin ribosome methylation) gene, can interfere with antibiotic binding. Acquired genes encoding efflux pumps, most predominantly mef(A) + msr(D) in pneumococci/streptococci and msr(A/B) in staphylococci, also mediate resistance. Drug-inactivating mechanisms include phosphorylation of the 2'-hydroxyl of the amino sugar found at position C5 by phosphotransferases and hydrolysis of the macrocyclic lactone by esterases. These acquired genes are regulated by either translation or transcription attenuation, largely because cells are less fit when these genes, especially the rRNA methyltransferases, are highly induced or constitutively expressed. The induction of gene expression is cleverly tied to the mechanism of action of macrolides, relying on antibiotic-bound ribosomes stalled at specific sequences of nascent polypeptides to promote transcription or translation of downstream sequences.

The prevalence of genotypes that determine resistance to macrolides, lincosamides, and streptogramins B compared with spiramycin susceptibility among erythromycin-resistant Staphylococcus epidermidis

Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, can be regarded as potential reservoirs of resistance genes for pathogenic strains, e.g., Staphylococcus aureus. The aim of this study was to assess the prevalence of different resistance phenotypes to macrolide, lincosamide, and streptogramins B (MLSB) antibiotics among erythromycin-resistant S. epidermidis, together with the evaluation of genes promoting the following different types of MLSB resistance:ermA, ermB, ermC,msrA, mphC, and linA/A’. Susceptibility to spiramycin was also examined. Among 75 erythromycin-resistantS. epidermidis isolates, the most frequent phenotypes were macrolides and streptogramins B (MSB) and constitutive MLSB (cMLSB). Moreover, all strains with the cMLSB phenotype and the majority of inducible MLSB (iMLSB) isolates were resistant to spiramycin, whereas strains with the MSB phenotype were sensitive to this antibiotic. The D-shape zone of inhibition around the clindamycin disc near the spiramycin disc was found for some spiramycin-resistant strains with the iMLSB phenotype, suggesting an induction of resistance to clindamycin by this 16-membered macrolide. The most frequently isolated gene was ermC, irrespective of the MLSB resistance phenotype, whereas the most often noted gene combination wasermC, mphC, linA/A’. The results obtained showed that the genes responsible for different mechanisms of MLSB resistance in S. epidermidis generally coexist, often without the phenotypic expression of each of them.