Antimicrobial Resistance and Virulence of Methicillin-Resistant Staphylococcus aureus from Human, Chicken and Environmental Samples within Live Bird Markets in Three Nigerian Cities

Ferrous sulfate remodels the properties of sodium alginate-based hydrogel and facilitates the healing of wound infection caused by MRSA

Frequent occurrence of wound infection caused by multiple-resistant bacteria (MRB) has posed a serious challenge to the current healthcare system relying on antibiotics. The development of novel antimicrobial materials with high safety and efficacy to heal wound infection is of great importance in combating this crisis. Herein, we prepared a promising antibacterial hydrogel by cross-linking ferrous ions (Fe2+) with the deprotonated carboxyl anion in sodium alginate (Na-ALG) to cure wound infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Interestingly, ferrous-modified Na-ALG (Fe-ALG) hydrogel demonstrated better properties compared to the traditional Na-ALG-based hydrogels, including injectability, self-healing, appropriate fluidity, high-water retention, potent MRSA-killing efficacy, and excellent biocompatibility. Importantly, the addition of Fe2+ enhances the antibacterial efficacy of the Na-ALG hydrogel, enabling it to effectively eliminate MRSA and accelerate the healing of antibiotic-resistant bacterial-infected wounds in a remarkably short period (10 days). This modification not only facilitates wound closure and fur generation, but also mitigates systemic inflammation, thereby effectively impeding the spread of MRSA to the lungs. Taken together, Fe-ALG hydrogel is a promising therapeutic material for treating wound infections by Staphylococcus aureus, especially by antibiotic-resistant strains like MRSA.

Genetic Characterization of Antibiotic-Resistant Staphylococcus spp. and Mammaliicoccus sciuri from Healthy Humans and Poultry in Nigeria

Staphylococcus spp. poses a significant threat to human and animal health due to their capacity to cause a wide range of infections in both. In this study, resistance genes conferring antibiotic resistance in Staphylococcus spp. and Mammaliicoccus sciuri isolates from humans and poultry in Edo state, Nigeria, were investigated. In April 2017, 61 Staphylococcus spp. isolates were obtained from urine, wounds, nasal and chicken fecal samples. Species identification was carried out by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Antimicrobial susceptibility testing was performed using the Kirby-Bauer method for 16 antibiotics. Whole-genome sequencing was used for characterization of the isolates. The 61 investigated isolates included Staphylococcus aureus, S. arlettae, M. sciuri, S. haemolyticus, and S. epidermidis. A total of 47 isolates (77%) belonged to human samples and 14 (23%) isolates were collected from poultry samples. All were phenotypically resistant to at least three antimicrobial(s). Multiple resistance determinants were detected in the human and poultry isolates analyzed. Phylogenetic analysis revealed close relatedness among the isolates within each species for S. arlettae, M. sciuri, and S. haemolyticus, respectively. This study delivered comprehensive genomic insights into antibiotic-resistant Staphylococcus species and M. sciuri isolates from human and poultry sources in Edo state, Nigeria, from a One Health perspective.

IFP35 aggravates Staphylococcus aureus infection by promoting Nrf2-regulated ferroptosis

INTRODUCTION

Serious Staphylococcus aureus (SA) infection is one of the most life-threatening diseases. Interferon-induced protein 35 (IFP35) is a pleiotropic factor that participates in multiple biological functions, however, its biological role in SA infection is not fully understood. Ferroptosis is a new type of regulated cell death driven by the accretion of free iron and toxic lipid peroxides and plays critical roles in tissue damage. Whether ferroptosis is involved in SA-induced immunopathology and its regulatory mechanisms remain unknown.

OBJECTIVES

We aimed to determine the role and underlying mechanisms of IFP35 in SA-induced lung infections.

METHODS

SA infection models were established using wild-type (WT) and IFP35 knockout (Ifp35-/-) mice or macrophages. Histological analysis was performed to assess lung injury. Quantitative real-time PCR, western blotting, flow cytometry, and confocal microscopy were performed to detect ferroptosis. Co-IP and immunofluorescence were used to elucidate the molecular regulatory mechanisms.

RESULTS

We found that IFP35 levels increased in the macrophages and lung tissue of SA-infected mice. IFP35 deficiency protected against SA-induced lung damage in mice. Moreover, ferroptosis occurred and contributed to lung injury after SA infection, which was ameliorated by IFP35 deficiency. Mechanically, IFP35 facilitated the ubiquitination and degradation of nuclear factor E2-related factor 2 (Nrf2), aggravating SA-induced ferroptosis and lung injury.

CONCLUSIONS

Our data demonstrate that IFP35 promotes ferroptosis by facilitating the ubiquitination and degradation of Nrf2 to exacerbate SA infection. Targeting IFP35 may be a promising approach for treating infectious diseases caused by SA.

Genetic Complexity of CC5 Staphylococcus aureus Isolates Associated with Sternal Bursitis in Chickens: Antimicrobial Resistance, Virulence, Plasmids, and Biofilm Formation

Sternal bursitis, a common inflammatory condition in poultry, poses significant challenges to both animal welfare and public health. This study aimed to investigate the prevalence, antimicrobial resistance, and genetic characteristics of Staphylococcus aureus isolates associated with sternal bursitis in chickens. Ninety-eight samples were collected from affected chickens, and 24 S. aureus isolates were identified. Antimicrobial susceptibility testing revealed resistance to multiple agents, with a notable prevalence of aminoglycoside resistance genes. Whole genome sequencing elucidated the genetic diversity and virulence profiles of the isolates, highlighting the predominance of clonal complex 5 (CC5) strains. Additionally, biofilm formation assays demonstrated moderate biofilm production capacity among the isolates. These findings underscore the importance of vigilant monitoring and targeted interventions to mitigate the impact of sternal bursitis in poultry production systems.

Future scope of plant-derived bioactive compounds in the management of methicillin-resistant Staphylococcus aureus: In vitro antimicrobial and antivirulence prospects to combat MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is a foremost human and animal pathogen with public health and veterinary significance causing hospital and community infections and contagious bovine mastitis. Due to its ability to develop multidrug resistance (MDR) and its pathogenicity, MRSA infection control is becoming a global concern. Natural antibacterial options are needed to combat MDR development and infectious dissemination. This study investigated the antimicrobial resistance and virulence genes profiling of MRSA isolates and explored the antivirulence efficacy of trans-cinnamaldehyde, thymol, and carvacrol essential oils (EOs) against multivirulent and MDR-MRSA isolates. Thirty six S. aureus isolates (25%) were retrieved, of which 34 (94.4%) were MRSA. A high prevalence of MDR (66.7%) was monitored and all 53 molecularly verified isolates possessed icaA and cna virulence genes. Moreover, 94.1% of these isolates were multivirulent with 23.5% of them carrying icaA, cna, eta, tst, and sea virulence genes. Our data proved superior in vitro antimicrobial and antivirulence activities of trans-cinnamaldehyde, thymol, and carvacrol. They inhibited the growth of multi-virulent and MDR-MRSA isolates and downregulated the transcription of examined virulence genes. Our study suggests using EOs as prospective antimicrobials with excellent antivirulence activities against MRSA isolates. We provided data regarding the eventual role of phytogenics in prevention and control of MRSA infection.

Identification of Bacterial Strains and Development of anmRNA-Based Vaccine to Combat Antibiotic Resistance in Staphylococcus aureus via In Vitro and In Silico Approaches

The emergence of antibiotic-resistant microorganisms is a significant concern in global health. Antibiotic resistance is attributed to various virulent factors and genetic elements. This study investigated the virulence factors of Staphylococcus aureus to create an mRNA-based vaccine that could help prevent antibiotic resistance. Distinct strains of the bacteria were selected for molecular identification of virulence genes, such as spa, fmhA, lukD, and hla-D, which were performed utilizing PCR techniques. DNA extraction from samples of Staphylococcus aureus was conducted using the Cetyl Trimethyl Ammonium Bromide (CTAB) method, which was confirmed and visualized using a gel doc; 16S rRNA was utilized to identify the bacterial strains, and primers of spa, lukD, fmhA, and hla-D genes were employed to identify the specific genes. Sequencing was carried out at Applied Bioscience International (ABI) in Malaysia. Phylogenetic analysis and alignment of the strains were subsequently constructed. We also performed an in silico analysis of the spa, fmhA, lukD, and hla-D genes to generate an antigen-specific vaccine. The virulence genes were translated into proteins, and a chimera was created using various linkers. The mRNA vaccine candidate was produced utilizing 18 epitopes, linkers, and an adjuvant, known as RpfE, to target the immune system. Testing determined that this design covered 90% of the population conservancy. An in silico immunological vaccine simulation was conducted to verify the hypothesis, including validating and predicting secondary and tertiary structures and molecular dynamics simulations to evaluate the vaccine’s long-term viability. This vaccine design may be further evaluated through in vivo and in vitro testing to assess its efficacy.

Prevalence and genetic characteristics of fosB-positive Staphylococcus aureus in duck farms in Guangdong, China in 2020

OBJECTIVES

To investigate the epidemiology of fosB-positive Staphylococcus aureus in waterfowl farms in the Pearl River tributaries in Guangdong Province, China in 2020.

METHODS

A total of 63 S. aureus were recovered from 315 samples collected from six duck farms and one goose farm. PFGE, WGS and analysis were performed on 19 fosB-positive S. aureus.

RESULTS

The fosfomycin resistance rate of the strains was as high as 52.4% (33/63), and 30.1% (19/63) of the strains carried fosB. Resistance gene prediction results showed that duck farm environment-derived strains contained the oxazolidinone drug resistance gene optrA. All fosB-positive S. aureus were MRSA and most of them were MDR, mainly ST9-t899 and ST164-t899. PFGE showed that fosB-positive S. aureus from humans and ducks could be clustered into the same clade. In addition, core-genome SNP analysis showed that clonal transmission of S. aureus occurred between humans and water. Pan-genome analysis showed that S. aureus had an open pangenome. The fosB gene was located on 2610-2615 bp plasmids, which all contained a broad host-range plasmid replication protein family 13. Small plasmids carrying the fosB gene could be found in different multilocus STs of S. aureus.

CONCLUSIONS

This study indicated that duck farms in Guangdong, China could be an important reservoir of fosB-positive S. aureus. The spread of drug-resistant bacteria in waterfowl farms requires further monitoring.

Human Colonization with Antibiotic-Resistant Bacteria from Nonoccupational Exposure to Domesticated Animals in Low- and Middle-Income Countries: A Critical Review

Data on community-acquired antibiotic-resistant bacterial infections are particularly sparse in low- and middle-income countries (LMICs). Limited surveillance and oversight of antibiotic use in food-producing animals, inadequate access to safe drinking water, and insufficient sanitation and hygiene infrastructure in LMICs could exacerbate the risk of zoonotic antibiotic resistance transmission. This critical review compiles evidence of zoonotic exchange of antibiotic-resistant bacteria (ARB) or antibiotic resistance genes (ARGs) within households and backyard farms in LMICs, as well as assesses transmission mechanisms, risk factors, and environmental transmission pathways. Overall, substantial evidence exists for exchange of antibiotic resistance between domesticated animals and in-contact humans. Whole bacteria transmission and horizontal gene transfer between humans and animals were demonstrated within and between households and backyard farms. Further, we identified water, soil, and animal food products as environmental transmission pathways for exchange of ARB and ARGs between animals and humans, although directionality of transmission is poorly understood. Herein we propose study designs, methods, and topical considerations for priority incorporation into future One Health research to inform effective interventions and policies to disrupt zoonotic antibiotic resistance exchange in low-income communities.

Prevalence of antibiotic-resistant bacteria amongst dogs in Africa: A meta-analysis review

Antimicrobial resistance (AMR) is a global public health threat for both human and veterinary medicine. Increasing evidence suggests that animals are important sources of AMR to humans; however, most of these studies focus on production animals. In order to determine the pattern of AMR in pets, mainly in dogs in Africa, a meta-analysis was performed with AMR studies conducted in African countries and published between January 2000 and January 2021 in four databases: Medline (PubMed), Scopus, Cab abstract and Google Scholar. Seven bacterial strains, namely Staphylococcus aureus, Escherichia coli, Salmonella spp., Pseudomonas aeruginosa, Streptococcus pyogenes, coagulase-negative Staphylococcus (SNC) and Staphylococcus pseudintermedius were included in this study. A total of 18 out of 234 indexed articles met the study criteria. The results revealed that multiple bacteria were resistant to various commonly used antibiotics including enrofloxacin, ciprofloxacin, gentamicin, amoxicillin, clavulanic acid, cotrimoxazole, streptomycin, tetracycline and chloramphenicol. Concerning multidrug resistance, E. coli strains came first with the highest prevalence of 98%, followed by P. aeroginosa (92%) and Salmonella spp. (53%). In contrast, the overall prevalence of multidrug resistance was low for S. aureus (18%) and S. pseudintermedius (25%). It is therefore urgent to find, as soon as possible, alternatives to replace these antibiotics, which have become ineffective in controlling these bacteria in dogs in Africa. Moreover, further metagenomic studies are needed to describe the full resistome and mobilome in dogs regardless of the bacteria.

A 6-Year Update on the Diversity of Methicillin-Resistant Staphylococcus aureus Clones in Africa: A Systematic Review

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital-associated (HA) and community-associated (CA) infections globally. The multi-drug resistant nature of this pathogen and its capacity to cause outbreaks in hospital and community settings highlight the need for effective interventions, including its surveillance for prevention and control. This study provides an update on the clonal distribution of MRSA in Africa.

Methods

A systematic review was conducted by screening for eligible English, French, and Arabic articles from November 2014 to December 2020, using six electronic databases (PubMed, EBSCOhost, Web of Science, Scopus, African Journals Online, and Google Scholar). Data were retrieved and analyzed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines (registered at PROSPERO: CRD42021277238). Genotyping data was based primarily on multilocus sequence types (STs) and Staphylococcal Cassette Chromosome mec (SCCmec) types. We utilized the Phyloviz algorithm in the cluster analysis and categorization of the MRSA STs into various clonal complexes (CCs).

Results

We identified 65 studies and 26 publications from 16 of 54 (30%) African countries that provided sufficient genotyping data. MRSA with diverse staphylococcal protein A (spa) and SCCmec types in CC5 and CC8 were reported across the continent. The ST5-IV [2B] and ST8-IV [2B] were dominant clones in Angola and the Democratic Republic of Congo (DRC), respectively. Also, ST88-IV [2B] was widely distributed across the continent, particularly in three Portuguese-speaking countries (Angola, Cape Verde, and São Tomé and Príncipe). The ST80-IV [2B] was described in Algeria and Egypt, while the HA-ST239/ST241-III [3A] was only identified in Egypt, Ghana, Kenya, and South Africa. ST152-MRSA was documented in the DRC, Kenya, Nigeria, and South Africa. Panton-Valentine leukocidin (PVL)-positive MRSA was observed in several CCs across the continent. The median prevalence of PVL-positive MRSA was 33% (ranged from 0 to 77%; n = 15).

Conclusion

We observed an increase in the distribution of ST1, ST22, and ST152, but a decline of ST239/241 in Africa. Data on MRSA clones in Africa is still limited. There is a need to strengthen genomic surveillance capacity based on a "One-Health" strategy to prevent and control MRSA in Africa.

Multi-Drug Resistant Escherichia coli, Biosecurity and Anti-Microbial Use in Live Bird Markets, Abeokuta, Nigeria

Live bird markets (LBM) remain a critical link from farm to fork in the poultry value chain, which oftentimes promotes indiscriminate antimicrobial use (AMU) and resistance (AMR). In this study, we assessed biosecurity practices, AMU, and associated these with multidrug resistant (MDR) E. coli in LBMs in Abeokuta, Ogun State. A cross-sectional survey among live bird sellers (LBS) in eight LBMs was conducted using a semi-structured questionnaire. Also, cloacal samples (n = 200) were randomly collected and pooled for bacteriological detection of MDR E. coli in live chickens of consenting LBS. Susceptibility to 14 antimicrobials belonging to 6 different classes was determined using the disk diffusion method. Biosecurity level and AMU were generally low. LBS less than 46 years were 6.8- fold more likely to fall within the poor biosecurity level (Crudes odds ratio = 6.8; 95% CI; 1.20-38.56; p = 0.03) than others. An informal or primary school education increased the odds of having a poor practice of AMU by 15.1 folds (Crudes odds ratio = 15.1; 95% CI; 2.73-84.18; p = 0.002) than those with secondary or tertiary. The prevalence of E. coli and MDR E. coli at the LBM level were 80% and 56.3%, respectively. Extremely high resistance rates were observed for ceftazidime (96.9%) and imipenem (90.6%). The odds of MDR E. coli increased eight-fold in poultry kept by LBS who use AMs as prophylaxis. This current data could be useful for the development of targeted behavioral risk communication and mitigation strategies for AMR to impede the potential horizontal transfer of AMR genes to humans through animal-sourced food.

Prevalence, antibiotic resistance, and enterotoxin production of Staphylococcus aureus isolated from retail raw beef, sheep, and lamb meat in Turkey

The main objective of this study was to isolate and identify Staphylococcus aureus from retail raw red meat samples and evaluate their enterotoxin gene and antibiotic resistance profiles. A total of 452 retail raw meat samples, including beef (n = 200), sheep (n = 125), and lamb (n = 127) randomly purchased from various supermarkets and butchers in Ankara between July 2019 and November 2020, were tested for the prevalence of S. aureus. The S. aureus strain was identified using morphological and molecular (16S rRNA and nuc gene) methods. Moreover, nine Staphylococcal enterotoxin (SE) genes were screened using polymerase chain reaction. Antibiotic resistance of S. aureus was determined using the phenotypic disc diffusion method. The overall prevalence of S. aureus among screened samples was 21.23%. Additionally, 65.62% of S. aureus strains contained SE gene regions. The predominant SEs in the S. aureus strains were sea (50.79%), followed by sed (25.39%) and seb (23.80%). However, sec, see, seg, seh, sei, and sej genes were never detected. A substantial proportion (40-100%) of the isolates were found resistant to kanamycin, telithromycin, penicillin G, streptomycin, erythromycin, cloxacillin, ampicillin, pristinamycin, nalidixic acid, azithromycin, and ciprofloxacin. Multi-drug resistance (MDR) was observed in 96.87% of the S. aureus strains. These results show a low prevalence of S. aureus in raw red meat samples in Turkey. However, a high rate of SEA raises serious health concerns. Due to the high levels of MDR observed in this study, there is a need to strictly control antibiotic use in animals in Turkey.

Phenotypic detection, antimicrobial susceptibility and virulence profile of staphylococci in the pig production setting, Makurdi, Nigeria

Livestock, particularly pigs, have increasingly been recognized as important reservoirs for zoonotic transmission of pathogenic bacteria, including staphylococci. Livestock production systems in developing countries of sub-Saharan Africa, including Nigeria, are characterized by high misuse/abuse of antimicrobials and a close association between humans and these animals, which promotes the emergence and transmission of resistant and potentially virulent bacteria. In the present study, we investigated the occurrence and characteristics (species distribution, virulence and resistance profile) of staphylococci from smallholder backyard pig farms, slaughter slabs and pig handlers in Makurdi, Nigeria. A total of 330 nasal swabs originating from 300 pigs and 30 in-contact humans were collected and processed. One hundred and thirteen samples [34.2 %; 95 % confidence interval (CI): 29.1–39.6] comprising 103 (34.3 %; 95 % CI: 29.0–40.0) and 10 (33.3 %; 95 % CI: 17.3–52.8 %) samples from pigs and humans, respectively, were positive for staphylococci, yielding 120 isolates (pigs n=110, humans n=10). The 120 isolates were distributed into 15 species with Staphylococcus aureus (n=25) followed by Staphylococcus cohnii (n=19) and Staphylococcus sciuri (n=14) occurring more frequently. All isolates were resistant to β-lactam (100 %) antibiotics. Resistance to some critical antimicrobials, including linezolid (22 %), vancomycin (19.2 %), gentamicin (7.5%) and the fluoroquinolones ciprofloxacin (75.8 %) and enrofloxacin (66.7 %), was also observed. Majority (99.2 %) of the isolates displayed a multidrug resistance phenotype with the AMP-C-CIP-E-ENR-FOX-OX-P-S-SXT-TE phenotype being predominant. Overall, 70 % of the isolates expressed the methicillin resistance phenotype, out of which 20 % (n=17) were MRSA. Resistance to serum bactericidal activity and biofilm production were respectively observed in 45 (100 %) and 5 (11.3 %) of the coagulase-positive staphylococci. Our findings demonstrated the occurrence of a high diversity of staphylococci expressing multidrug resistance and potentially virulent phenotypes among healthy swine and pig handlers in small-scale backyard farms in North-Central Nigeria. These findings underscore the potential role of pig production settings in the emergence and dissemination of potentially virulent staphylococci and the importance of the development of antimicrobial resistance monitoring systems/implementation of control measures in developing countries. Proper hygienic practices and control of indiscriminate use and misuse of antibiotics are recommended.

Biosecurity and Antimicrobial Use Practices in Live Bird Markets within Abeokuta Metropolis, Southwest, Nigeria: A Preliminary Survey

The development of an antimicrobial stewardship plan (AMSP) for live bird sellers (LBS) requires an understanding of the current biosecurity status, antimicrobial use (AMU) and the practices involved in live bird selling (e.g., drivers, sellers, etc.) which is a direct source of poultry meat for human consumption. Seven Live Bird Markets (LBMs) within Abeokuta, Ogun State were surveyed using a semi-structured questionnaire. Data on LBMs characteristics, LBS demographics, biosecurity, and AMU practices, awareness on Antimicrobial Resistance (AMR), as well as preferred channels of information on antimicrobial stewardship were gathered. A total of 40 consenting LBS with 82.5% female and 17.5% male participants were included in the study. The participants’ mean age was 45.3 years (SD±11.9, range: 23-70 years). Laying hens, broilers, and cockerels were the main poultry types sold by LBS. Antimicrobials (AMs) were used for growth promotion (57.5%), therapeutic (40.0%), and prophylactic (2.5%) purposes. Tetracycline, metronidazole, and chloramphenicol were the most frequently used AMs. The majority of the participants (90.0%) have treated birds based on their empirical experience, with little or no inputs from veterinarians. Biosecurity and AMU practices were generally low (54.0% and 34.0%, respectively). The contact with veterinarians was associated with satisfactory biosecurity practices (p=0.049). No significant factors were found to be linked with AMU. This study has provided recent evidence-based data on practices in poultry management among LBS in Abeokuta, Ogun state. The findings would be useful for policy decisions and the development of AMSP on prudent AMU among LBS.

Genomic analysis of Staphylococcus aureus from the West African Dwarf (WAD) goat in Nigeria

Background

Staphylococcus aureus can colonize various host species, and human-animal interaction is a significant factor for cross-species transmission. However, data on S. aureus colonization in animals, particularly on ruminants in close contact with humans, is limited. The West African Dwarf (WAD) goat is among the earliest domesticated ruminant associated with rural dwellers and small-holder farmers in sub-Saharan Africa. This study aimed to investigate the population structure, antibiotic resistance, and virulence gene determinants of S. aureus from the WAD goat in Nigeria.

Methods

Nasal samples were obtained from the WAD goat in five markets in Osun State, South-West Nigeria. S. aureus was characterized by antibiotic susceptibility testing, detection of virulence determinants, spa typing, and multilocus sequence typing (MLST). Representative isolates were selected for whole-genome sequencing, biofilm, and cytotoxicity assay.

Results

Of the 726 nasal samples obtained from the WAD goat, 90 S. aureus (12.4%) were recovered. Overall, 86 isolates were methicillin-susceptible, and four were mecA-positive (i.e., methicillin-resistant S. aureus [MRSA]). A diverse S. aureus clonal population was observed (20 sequence types [STs] and 37 spa types), while 35% (13/37) and 40% (8/20) were new spa types and STs, respectively. Eleven MLST clonal complexes (CC) were identified (CC1, CC5, CC8, CC15, CC30, CC45, CC97, CC121, CC133, CC152, CC522). The MRSA isolates were designated as t127-ST852-CC1-SCCmec type VII, t4690-ST152-CC152-SCCmec type Vc, and t8821-ST152-CC152-SCCmec type Vc. Phylogenetic analysis revealed that 60% (54/90) of all isolates were associated with ruminant lineages (i.e., CC133, CC522). Panton-Valentine Leukocidin (PVL)-positive S. aureus was identified in CC1, CC30, CC121, and CC152. For the CC522 isolates, we illustrate their pathogenic potential by the detection of the toxic shock syndrome gene and hemolysins, as well as their strong cytotoxicity and ability to form biofilms.

Conclusions

This is the first detailed investigation on the genomic content of S. aureus from the WAD goat in Nigeria. The S. aureus population of the WAD goat consists mainly of ruminant-associated lineages (e.g., CC133, CC522), interspersed with human-associated clones, including PVL-positive MRSA CC1 and CC152.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-021-00987-8.

"Barcode" cell sensor microfluidic system: Rapid and sample-to-answer antimicrobial susceptibility testing applicable in resource-limited conditions

Many rapid antimicrobial susceptibility testing (AST) methods have been proposed to contain clinical antimicrobial resistance (AMR) and preserve the effectiveness of remaining antimicrobials. However, far fewer methods have been proposed to test AMR in resource-limited conditions, such as for frequent safety screenings of water/food/public facilities, urgent surveys of massive samples during a pandemic, or AMR tests in low-income countries. Rapid AST methods realized thus far have a variety of drawbacks when used for such surveys, e.g., high cost and the requirement of expensive instruments such as microscopy. A more reasonable strategy would be to screen samples via onsite testing first, and then send any sample suspected to contain AMR bacteria for advanced testing. Accordingly, a cost-efficient AST is demanded, which can rapidly process a large number of samples without using expensive equipment. To this end, current work demonstrates a novel "barcode" cell sensor based on an adaptive linear filter array as a fully automatic and microscope-free method for counting very small volumes of cells (~1.00 × 10⁴ cells without pre-incubation), wherein suspended cells concentrate into microbars with length proportional to the number of cells. We combined this sensor with an on-chip culture approach we had demonstrated for rapid and automated drug exposure and realized a low-cost and resource-independent platform for portable AST, from which results can be obtained simply through a cell phone. This method has a much shorter turnaround time (2-3 h) than that of standard methods (16-24 h). Thanks to its microscopy-free analysis, affordability, portability, high throughput, and user-friendliness, our "barcode" AST system has the potential to fulfill the various demands of AST when advanced facilities are not available, making it a promising new tool in the fight against AMR.