New quadriplex PCR assay for detection of methicillin and mupirocin resistance and simultaneous discrimination of Staphylococcus aureus from coagulase-negative staphylococci

Molecular epidemiology and clinical characteristics of Staphylococcus aureus bacteremia in Japanese adults

INTRODUCTION

Staphylococcus aureus bacteremia (SAB), especially when caused by methicillin-resistant S. aureus (MRSA), is of considerable clinical importance. In recent years, the proportion of MRSA among S. aureus has decreased, and a relative increase in the proportion of methicillin-susceptible S. aureus (MSSA) has been observed. It is therefore necessary to consider both MRSA and MSSA when assessing the microbiological and clinical significance of SAB.

MATERIALS AND METHODS

We included SAB cases from the Nara Medical University Hospital between January 2015 and February 2017. We performed drug susceptibility testing, toxicity gene analysis, multilocus sequence typing (MLST), and polymerase chain reaction-based open reading frame typing (POT) of stored strains to integrate clinical and bacteriological characteristics.

RESULTS

There were 90 cases during the experimental period (42 MRSA and 48 MSSA), with 30-day mortality rates of 19 % for MRSA and 10.4 % for MSSA. Deaths were more frequently complicated by septic shock and disseminated intravascular coagulation. MLST studies showed that ST8, ST764, ST1, and ST15 were prevalent in the MRSA group, whereas ST5, ST188, and ST12 were prevalent in MSSA. Infective endocarditis cases had a long time from onset to the initiation of effective antimicrobials and were all MSSA. MLST and POT results correlated well, and POT appeared to have better discriminatory power.

CONCLUSIONS

The severity and mortality of SAB, along with the microbiological characteristics of causative isolates, vary by location and time. Continued studies integrating clinical and microbiological investigations are thus needed.

Multi-drug resistant Staphylococcus epidermidis from chronic wounds impair healing in human wound model

Venous leg ulcers (VLUs) represent one of the most prevalent types of chronic wounds characterised by perturbed microbiome and biofilm-forming bacteria. As one of the most abundant skin-commensal, Staphylococcus epidermidis is known as beneficial for the host, however, some strains can form biofilms and hinder wound healing. In this study, S. epidermidis distribution in VLUs and associated resistome were analysed in ulcer tissue from patients. Virulence of S. epidermidis isolates from VLUs were evaluated by whole genome sequencing, antimicrobial susceptibility testing, in vitro biofilm and binding assays, and assessment of biofilm-forming capability and pro-inflammatory potential using human ex vivo wound model. We demonstrated that S. epidermidis isolates from VLUs inhibit re-epithelialization through biofilm-dependent induction of IL-1β, IL-8, and IL-6 which was in accordance with impaired healing outcomes observed in patients. High extracellular matrix binding ability of VLU isolates was associated with antimicrobial resistance and expression levels of the embp and sdrG, responsible for bacterial binding to fibrinogen and fibrin, respectively. Finally, we showed that S. epidermidis from VLUs demonstrate pathogenic features with ability to impair healing which underscores the emergence of treatment-resistant virulent lineages in patients with chronic ulcers.

Comparative Antimicrobial Resistance and Prevalence of Methicillin Resistance in Coagulase-Positive Staphylococci from Conventional and Organic Dairy Farms in South Korea

Bovine mastitis (BM) has caused huge economic and financial losses in the dairy industry worldwide, with Staphylococcus aureus as one of its major pathogens. BM treatment still relies on antibiotics and its extensive use often generates methicillin-resistant S. aureus (MRSA) and mupirocin-resistant S. aureus (MuRSA). This study compared the antimicrobial resistance trend in coagulase-positive Stapholococci (CoPS) isolated from BM milk in conventional and organic dairy farms and checked prevalence of MRSA and MuRSA. A total of 163 presumptive Staphylococci were isolated, wherein 11 out of 74 from 4 conventional farms (CF1, CF2, CF3, CF4) and 17 out of 89 from 3 organic farms (OF1, OF2, OF3) exhibited coagulase activity. Multiplex-PCR amplification confirmed at least one coagulase-positive isolate from CF1, CF2, CF3, CF4, and OF1 as S. aureus, denoted by the presence of the nuc gene. Three isolates from CF2 contained the mecA gene, indicating MRSA prevalence, while the MuRSA gene marker, mupA, was not detected in any of the isolates. Antimicrobial testing showed that conventional farm isolates were more resistant to antibiotics, especially ampicillin and tetracycline. This suggests a risk of developing multidrug resistance in dairy farms if antibiotic use is not properly and strictly monitored and regulated.

Synanthropic rodents and shrews are reservoirs of zoonotic bacterial pathogens and act as sentinels for antimicrobial resistance spillover in the environment: A study from Puducherry, India

Antimicrobial resistance (AMR) is a global public health concern and needs to be monitored for control. In this study, synanthropic rodents trapped from humans and animal habitats in Puducherry, India, were screened as sentinels for bacterial pathogens of public health importance and antimicrobial resistance spillover. From the trapped rodents and shrews (n = 100) pathogens viz., Staphylococcus sp, E. coli and Salmonella sp were isolated from oropharyngeal and rectal swabs on Mannitol salt, Mac Conkey and Xylose lysine deoxycholate media respectively. The AMR genes in these isolates were screened by PCR. A total of 76, S. aureus and 19, Staphylococcus non aureus were isolated. E. coli was isolated in 89 samples and among the Salmonella sp (n = 59), 16, were S. enteritidis and 29, were S. typhimurium. A total of 46 MRSA isolates with mec A (n = 40) and mec C (n = 6) were detected. Also, 36.84% and 5.3% Staphylococcus non aureus isolates were tested to have mec A and mec C genes. AMR genes encoding ESBL [blaTEM in 21, blaSHV in 45 and blaCTX-M in 11] was tested positive in 77 E. coli isolates. Among, Salmonella isolates 44/45 were screened to have AMR genes [tet in 13, sul3 & sul4 in 20 and qnrA in 11]. Antibiotic sensitivity test confirmed the antimicrobial resistance. Isolation of pathogens of public health importance and demonstration of genetic elements conferring antimicrobial resistance in the synanthropic rodents confirms that they act as reservoirs and appropriate sentinels to monitor AMR spillover in the environment.

Whole genome sequencing of methicillin-resistant Staphylococcus aureus clinical isolates from Terengganu, Malaysia, indicates the predominance of the EMRSA-15 (ST22-SCCmec IV) clone

Despite the importance of methicillin-resistant Staphylococcus aureus (MRSA) as a priority nosocomial pathogen, the genome sequences of Malaysian MRSA isolates are currently limited to a small pool of samples. Here, we present the genome sequence analyses of 88 clinical MRSA isolates obtained from the main tertiary hospital in Terengganu, Malaysia in 2016-2020, to obtain in-depth insights into their characteristics. The EMRSA-15 (ST22-SCCmec IV) clone of the clonal complex 22 (CC22) lineage was predominant with a total of 61 (69.3%) isolates. Earlier reports from other Malaysian hospitals indicated the predominance of the ST239 clone, but only two (2.3%) isolates were identified in this study. Two Indian-origin clones, the Bengal Bay clone ST772-SCCmec V (n = 2) and ST672 (n = 10) were also detected, with most of the ST672 isolates obtained in 2020 (n = 7). Two new STs were found, with one isolate each, and were designated ST7879 and ST7883. From the core genome phylogenetic tree, the HSNZ MRSA isolates could be grouped into seven clades. Antimicrobial phenotype-genotype concordance was high (> 95%), indicating the accuracy of WGS in predicting most resistances. Majority of the MRSA isolates were found to harbor more than 10 virulence genes, demonstrating their pathogenic nature.

The potential of nano graphene oxide and chlorhexidine composite membranes for use as a surface layer in functionally graded membranes for periodontal lesions

Membranes have been used for treating periodontal defects and play a crucial role in guided bone regeneration applications. Nano graphene oxide have been exploited in tissue engineering due to its biomechanical properties. Its composite formulations with hydroxyapatite and chitosan with controlled degradation could aid in becoming part of a surface layer in a functionally graded membrane. The aim of the study was to synthesize chitosan and composite formulations of nano graphene oxide, hydroxyapatite and chlorhexidine digluconate using solvent casting technique and to characterize the physiochemical, mechanical, water vapor transmission rate (barrier), degradation and antimicrobial potential of the membranes. Altogether four different membranes were prepared (CH, CCG, 3511 and 3322). Results revealed the chemical interactions of hydroxyapatite, chitosan and nanographene oxide due to inter and intra molecular hydrogen bonding. The tensile strength of 3322 (33.72 ± 6.3 MPa) and 3511 (32.06 ± 5.4 MPa) was higher than CH (27.46 ± 9.6 MPa). CCG showed the lowest water vapor transmission rate (0.23 ± 0.01 g/h.m2) but the highest weight loss at day 14 (76.6 %). 3511 showed a higher drug release after 72 h (55.6 %) Significant biofilm growth inhibition was observed for all membranes. 3511 showed complete inhibition against A. actinomycetemcomitans. Detailed characterization of the synthesized membranes revealed that 3511 composite membrane proved to be a promising candidate for use as a surface layer of membranes for guided bone regeneration of periodontal lesions.

The occurrence and contamination of optrA-positive methicillin-resistant Staphylococcus aureus from duck farms in Guangdong, China

OBJECTIVES

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is an important zoonotic microorganism that increasingly causes public health concern worldwide. The objective of this study was to determine the prevalence and transmission of S. aureus in duck farms and evaluate its antimicrobial resistance and genetic characteristics.

METHODS

The samples associated with ducks, feeders, and the environment were collected on 14 duck farms from four areas in Guangdong, China, from 2020 to 2021. All isolates were subjected to antimicrobial susceptibility testing. A comprehensive epidemiological survey of S. aureus was conducted by S. aureus protein A typing and whole-genome sequencing.

RESULTS

A total of 560 samples were collected. The prevalence rate of MRSA among ducks (8.1%, 11 of 135) was higher compared with that in environmental samples. OptrA-positive ST398-t034 MRSA were first detected from duck farms in China. A total of 79.3% (34 of 46) S. aureus isolates showed multidrug-resistant phenotypes. Notably, some isolates carried multidrug-resistant genes encoding macrolide-lincosamide-streptogramin B, pleuromutilin-pleuromutilin-streptogramin A, and oxazolidinone. Analysis of the virulence genes revealed that the MRSA isolates carried genes encoding gamma-hemolysin, enterotoxin, and leukocidin. ST9-t899 is a primary clonal lineage among duck- and environment-associated MRSA. Single-nucleotide polymorphism analysis showed the potential contamination relationship of optrA-positive ST2308 MRSA isolates carrying the gamma-hemolysin genes and the leukocidin virulence genes between airborne dust and sick ducks.

CONCLUSION

The contamination of MRSA, especially optrA-positive MRSA, between food animals and the environment is a growing public health concern worldwide. Based on One Health principles, continuous surveillance of MRSA is urgently needed.

A multiplex Taqman PCR assay for MRSA detection from whole blood

Methicillin-resistant Staphylococcus aureus (MRSA) causes a wide range of hospital and community-acquired infections worldwide. MRSA is associated with worse clinical outcomes that can lead to multiple organ failure, septic shock, and death, making timely diagnosis of MRSA infections very crucial. In the present work, we develop a method that enables the positive enrichment of bacteria from spiked whole blood using protein coated magnetic beads, followed by their lysis, and detection by a real-time multiplex PCR directly. The assay targeted bacterial 16S rRNA, S. aureus (spa) and methicillin resistance (mecA). In addition, an internal control (lambda phage) was added to determine the assay's true negative. To validate this assay, staphylococcal and non-staphylococcal bacterial strains were used. The three-markers used in this study were detected as expected by monomicrobial and poly-microbial models of the S. aureus and coagulase-negative staphylococci (CoNS). The thermal cycling completed within 30 mins, delivering 100% specificity. The detection LoD of the pre-processing step was ∼ 1 CFU/mL from 2-5mL of whole blood and that of PCR was ∼ 1pg of NA. However, the combined protocol led to a lower detection limit of 100-1000 MRSA CFUs/mL. The main issue with the method developed is in the pre-processing of blood which will be the subject of our future study.

Molecular characteristics of Staphylococcus aureus strains isolated from subclinical mastitis of water buffaloes in Guangdong Province, China

Intramammary infections (IMI) in animals reared for milk production can result in large economic losses and distress to the animals. Staphylococcus aureus is an important causative agent of IMI in dairy cows, but its prevalence in water buffaloes has not been determined. Therefore, the current study was conducted to investigate the prevalence of subclinical mastitis in water buffaloes and the antimicrobial susceptibility, virulence genes and biofilm formation abilities of Staphylococcus aureus isolates recovered from water buffaloes in Guangdong, China. Staphylococcus aureus strains were isolated from milk samples of water buffaloes with subclinical mastitis, and twofold microdilution, PCR and crystal violet staining methods were used to determine antimicrobial susceptibility, distributions of virulence and antimicrobial resistance genes and biofilm formation ability, respectively. Our results indicated that 29.44% of water buffaloes were diagnosed with subclinical mastitis, and the most prevalent pathogens were Escherichia coli (96.17%), coagulase-negative staphylococci (CoNS) (67.60%) and S. aureus (28.57%). Most S. aureus isolates showed resistance to bacitracin, doxycycline, penicillin, florfenicol, and tetracycline but were susceptible to ciprofloxacin, ceftizoxime, cefoquinoxime, and ofloxacin. Moreover, 63.72% of S. aureus isolates were positive for tetM, and the prevalence of msrB, blaZ, mecA, fexA, and tetK ranged from 21.24 to 6.19%. All S. aureus isolates harbored clfB and icaA genes, and the virulence genes hla (93.8%), hld (91.15%), clfA (90.27%), fnbA (86.73%), and hlb (83.19%), and tsst, icaD, sec, see, fnbB, and sea showed a varied prevalence ranging from 3.5 to 65.49%. All S. aureus isolates possessed the ability to form biofilms, and 30.09% of isolates showed strong biofilm formation abilities, while 19.47% of isolates were weak biofilm producers. Our results indicated that subclinical mastitis is prevalent in water buffaloes in Guangdong, China, and S. aureus is prevalent in samples from water buffaloes with subclinical mastitis. Most S. aureus isolates were susceptible to cephalosporins and fluoroquinolones; thus, ceftizoxime and cefoquinoxime can be used to treat subclinical mastitis in water buffaloes.

Whole Genome Sequencing and Molecular Epidemiology of Clinical Isolates of Staphylococcus aureus from Algeria

Staphylococcus aureus is an important pathogen responsible for various healthcare- and community-acquired infections. In this study, whole genome sequencing (WGS) was used to genotype S. aureus clinical isolates from two hospitals in Algeria and to characterize their genetic determinants of antimicrobial resistance. Seventeen S. aureus isolates were included in this study. WGS, single-nucleotide polymorphism (SNP)-based phylogenetic analysis, in silico multilocus sequence typing (MLST), spa and staphylococcal cassette chromosome mec (SCCmec) typing and in silico antimicrobial resistance profiling were performed. Phenotypic antibiotic susceptibility testing was performed using the Vitek 2 system and the disk diffusion method. The isolates were separated into sequence types (STs), with ST80 being predominant; five clonal complexes (CCs); four spa types (t044, t127, t368, t386); and two SCCmec types (IVc and IVa). Whole genome analysis revealed the presence of the resistance genes mecA, blaZ, ermC, fusB, fusC, tetK, aph(3')-IIIa and aad(6) and mutations conferring resistance in the genes parC and fusA. The rate of multidrug resistance (MDR) was 64%. This work provides a high-resolution characterization of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolates and emphasizes the importance of continuous surveillance to monitor the spread of S. aureus in healthcare settings in the country.

Livestock, pets and humans as carriers of methicillin-resistant Staphylococcusaureus and comparative evaluation of two PCR protocols for detection

Staphylococcus aureus are Gram positive bacteria known to acquire antibiotic resistance rapidly and pose a major challenge to clinicians worldwide. Infections by methicillin resistant Staphylococcus aureus (MRSA) are usually associated with increased mortality and prolonging of treatment. Samples (n = 706) from diverse sources (livestock, pets, animal handlers, human hospital) were collected and screened for the presence of MRSA by phenotypic and genotypic methods. The incidence of Staphylococcus aureus was greater in goats (42.00%; 28.20 - 56.80%, confidence interval [CI] 95.00%) followed by cattle (13.50%; 9.20 - 18.80%, CI 95.00%), humans (12.90%; 9.30 - 17.40%, CI 95.00%) and dogs (12.90%; 8.10 - 19.20%, CI 95.00%). Significantly higher incidence of MRSA was observed in dogs (65.00%; 40.80 - 84.60%, CI 95.00%), compared to other hosts namely cattle (48.00%; 26.50 - 64.30%, CI 95.00%), humans (35.00%; 20.20 - 52.50%, CI 95.00%) and goats (10.00%; 1.20 - 30.40%, CI 95.00%). All the S. aureus isolates were further screened for thermostable nuclease (nuc gene) by polymerase chain reaction (PCR). The incidence of nuc gene in cattle, dog, goat and human were found to be 3.30% (1.30 - 6.60%, CI 95.00%), 5.20% (2.30 - 9.90%, CI 95.00%), 28.00% (16.20 - 42.50%, CI 95.00%) and 9.10% (6.00 - 13.00%, CI 95.00%), respectively. Comparative evaluation of two PCR primers (mecA-162 and mecA-310) indicated the former one as more rational choice for detection of MRSA. Overall, the results of our study indicated possible risk of zoonotic transmission of MRSA from canines.

Methicillin-Resistant Staphylococcusaureus Strains Isolated from Burned Patients in a Tunisian Hospital: Molecular Typing, Virulence Genes, and Antimicrobial Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major causes of a variety of infections in hospitals and the community. Their spread poses a serious public health problem worldwide. Nevertheless, in Tunisia and other African countries, very little molecular typing data on MRSA strains is currently available. In our study, a total of 64 MRSA isolates were isolated from clinical samples collected from burned patients hospitalized in the Traumatology and Burns Center of Ben Arous in Tunisia. The identification of the collection was based on conventional methods (phenotypic and molecular characterization). The characterization of the genetic support for methicillin resistance was performed by amplification of the mecA gene by polymerase chain reaction (PCR), which revealed that 78.12% of S. aureus harbors the gene. The resistance of all the collection to different antibiotic families was studied. Indeed, the analysis of strain antibiotic susceptibility confirmed their multi-resistant phenotype, with high resistance to ciprofloxacin, gentamicin, penicillin, erythromycin, and tetracycline. The resistance to the last three antibiotics was conferred by the blaZ gene (73.43%), the erm(C) gene (1.56%), the msr(A) gene (6.25%), and tet(M) gene (7.81%), respectively. The clonal diversity of these strains was studied by molecular typing of the accessory gene regulator (agr) system, characterization of the SCCmec type, and spa-typing. The results revealed the prevalence of agr types II and III groups, the SCCmec type III and II cassettes, and the dominance of spa type t233. The characterization of the eight enterotoxins genes, the Panton-Valentine leukocidin and the toxic shock syndrome toxin, was determined by PCR. The percentage of virulence genes detected was for enterotoxins (55%), tst (71.88%), leukocidin E/D (79.69%), and pvl (1.56%) factors. Furthermore, our results revealed that the majority of the strains harbor IEC complex genes (94%) with different types. Our findings highlighted the emergence of MRSA strains with a wide variety of toxins, leukocidin associated with resistance genes, and specific genetic determinants, which could constitute a risk of their spread in hospitals and the environment and complicate infection treatment.

Effects of Piper betle Extracts against Biofilm Formation by Methicillin-Resistant Staphylococcus pseudintermedius Isolated from Dogs

Emergence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolated from dogs with cutaneous and wound infections has significantly impacted veterinary medicine. This study aimed to isolate S. pseudintermedius from canine pyoderma and investigate the effects of ethanolic extracts of Piper betle (PB), P. sarmentosum (PS), and P. nigrum (PN) on the bacterial growth and biofilm formation of S. pseudintermedius and MRSP. Of the isolated 152 isolates, 53 were identified as S. pseudintermedius using polymerase chain reaction, and 10 isolates (6.58%) were identified as MRSP based on the presence of mecA. Based on phenotype, 90% of MRSPs were multidrug-resistant. All MRSP had moderate (10%, 1/10) and strong (90%, 9/10) biofilm production ability. PB extracts were the most effective in inhibiting planktonic cells, and the minimum inhibitory concentration at which ≥50% of the isolates were inhibited (MIC₅₀) was 256 µg/mL (256-1024 µg/mL) for S. pseudintermedius isolates and 512 µg/mL (256-1024 µg/mL) for MRSP isolates. The MIC₉₀ for S. pseudintermedius and MRSP was 512 µg/mL. In XTT assay, PB at 4× MIC showed an inhibition rate of 39.66-68.90% and 45.58-59.13% for S. pseudintermedius and MRSP, respectively, in inhibiting biofilm formation. For PB at 8× MIC, the inhibition rates for S. pseudintermedius and MRSP were 50.74-81.66% and 59.57-78.33%, respectively. Further, 18 compounds were identified in PB using gas chromatography-mass spectrometry, and hydroxychavicol (36.02%) was the major constituent. These results indicated that PB could inhibit bacteria growth of and biofilm formation by S. pseudintermedius and MRSP isolated from canine pyoderma in a concentration-dependent manner. Therefore, PB is a potential candidate for the treatment of MRSP infection and biofilm formation in veterinary medicine.

Analysis of antibiotic resistance and genetic profile of conjunctival bacteria flora before and after cataract surgery

PURPOSE

To analyze antibiotic resistance and genetic profile of conjunctival bacteria flora before and after cataract surgery with the focus on coagulase-negative staphylococci (CNS) during cataract surgery and discuss the implications of this colonization as a potential risk of acquiring endophthalmitis.

METHODS

After approval of the institutional review board and informed consent from patients had been obtained, conjunctival swabs for culture from 59 patients undergoing cataract surgery were taken of the fellow eye at baseline (C0) and from the eye to be operated before (T0) and after (T1) irrigation with povine-iodine 5%, and at the end of surgery (T2). Genes responsible for virulence (mecA, ica and atlE) and antibiotic profile were determined; strain clonality of persistent colonizing Staphylococcus epidermidis strains was established by the Multi-locus sequence typing (MLST).

RESULTS

The frequency of CNS was significantly reduced in T1 (13.6%) from 81.4% in T0 and 86.4% in C0. The frequency of mecA, ica and atlE genes was 34.4%, 37.5% and 61.4%, respectively; and methicillin phenotypic resistance was 35.4%. S. epidermidis was the most frequent species isolated in every time point. MLST revealed in 7 patients 100% coincidence of the seven alleles of the S. epidermidis isolated previous to povine-iodine 5% disinfection and at the end of the surgery. CNS isolates from T1 or T2 corresponded to the same species, antibiotic and virulence profile as those isolates from C0 or T0.

CONCLUSION

Povidone-iodine 5% prophylaxis before surgery significantly reduced conjunctival contamination; in those that persisted, the source of contamination was mostly the patient's microbiota confirmed by the MLST system.

A comparative study on antibiotic resistance and virulence properties of Staphylococcus aureus isolated from hospitalized patients and hospital environment

BACKGROUND

We compared the characteristics of clinical Staphylococcus aureus and S. aureus isolated from environmental surfaces in 3 hospitals.

METHODS

Clinical S. aureus isolates were collected from hospitalized patients. Environmental surfaces were sampled from the rooms of patients infected with S. aureus. After identifying rooms with the target organism, 3-5 high-touch surfaces in patient care areas were sampled using swabs before room cleaning by environmental services. S. aureus isolates were subjected to genotyping, antimicrobial susceptibility testing, and virulence determinant screening. The isolates were analyzed for integron content and sequences of variable region amplification products.

RESULTS

There were epidemiologically unrelated 79 clinical and 62 environmental S. aureus isolates. Overall, 11.4% of clinical and 59.7% of environmental isolates were methicillin-resistant. The environmental and clinical S. aureus exhibited very different virulence profiles: 79% of the environmental isolates were negative for virulence genes compared to 2.5% of clinical isolates (P < .001). Environmental isolates were more resistant to antibiotics compared to clinical isolates. Class 1 integrons were only detected in 7 of 62 environmental isolates, of which 3 isolates had integrons with cysteine synthase cassette, 1 had aadA1, and 1 had an unknown cassette.

CONCLUSION

These data indicate the different characteristics between environmental and clinical S. aureus, which may reflect different reservoirs from which the 2 groups acquired the strains.

Development of a Multiplex Polymerase Chain Reaction-Based DNA Lateral Flow Assay as a Point-of-Care Diagnostic for Fast and Simultaneous Detection of MRSA and Vancomycin Resistance in Bacteremia

To reduce high mortality and morbidity rates, timely and proper treatment of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection is required. A multiplex polymerase reaction (mPCR)-based DNA lateral flow assay (MBDLFA) was developed as a point-of-care diagnostic for simultaneous identification of S. aureus, methicillin resistance, and vancomycin resistance directly from blood or blood cultures. A mPCR was developed to detect nuc, mecA, and vanA/B; its sensitivity, specificity, and limit of detection (LOD) were determined. The developed reaction was further modified for use in MBDLFA and its sensitivity for detection of target genes from artificially inoculated blood samples was checked. The optimized mPCR successfully detected nuc, mecA, and vanA/B from genomic DNA of bacterial colonies with LODs of 107, 107, and 105 CFU/mL, respectively. The reaction was sensitive and specific. The optimized mPCR was used in MBDLFA that detected nuc, mecA, and vanA/B with LODs of 107, 108, and 104 CFU/mL, respectively, directly from artificially inoculated blood. The developed MBDLFA can be used as a rapid, cheap point-of-care diagnostic for detecting S. aureus, MRSA, and vancomycin resistance directly from blood and blood cultures in ~2 h with the naked eye. This will reduce morbidity, mortality, and treatment cost in S. aureus bacteremia.

Impacts of Fortifying Nile Tilapia (Oreochromis niloticus) Diet with Different Strains of Microalgae on Its Performance, Fillet Quality and Disease Resistance to Aeromonas hydrophila Considering the Interplay between Antioxidant and Inflammatory Response

The oxidative stress facing fish during intensive production brings about diseases and mortalities that negatively influence their performance. Along with that, the increased awareness of omega-3 polyunsaturated fatty acids (omega-3-PUFAs) health benefits has been triggered the introduction of alternative additives in aqua feed that cause not only modulation in fish immune response but also fortification of their fillet. In this context, the role of microalgae mix (NSS) containing Nannochloropsis oculate and Schizochytrium and Spirulina species, which were enriched with bioactive molecules, especially EPA and DHA, was assessed on Nile tilapia's performance, fillet antioxidant stability, immune response, and disease resistance. Varying levels of NSS (0.75, 1.5, and 3%) were added to Nile tilapia's diet for 12 weeks and then a challenge of fish with virulent Aeromonas hydrophila (A. hydrophila) was carried out. Results showed that groups fed NSS, especially at higher levels, showed an improved WG and FCR, which corresponded with enhanced digestive enzymes' activities. Higher T-AOC was detected in muscle tissues of NSS3.0% fed fish with remarkable reduction in ROS, H2O2, and MDA contents, which came in parallel with upregulation of GSH-Px, CAT, and SOD genes. Notably, the contents of EPA and DHA in fillet were significantly increased with increasing the NSS levels. The mean log10 counts of pathogenic Vibrio and Staphylococcus species were reduced, and conversely, the populations of beneficial Lactobacillus and Bacillus species were increased more eminent after supplementation of NSS3.0% and NSS1.5%. Moreover, regulation of the immune response (lysozyme, IgM, ACH50, NO, and MPO), upregulation of IL-10, TGF-β, and IgM, and downregulation of IL-1β, TNF-α, HSP70,and COX-2 were observed following dietary higher NSS levels. After challenge, reduction in A. hydrophila counts was more prominent, especially in NSS3.0% supplemented group. Taken together, the current study encourages the incorporation of such microalgae mix in Nile tilapia's diet for targeting maximum performance, superior fillet quality, and protection against A. hydrophila.

The Clinical Significance of Staphylococcus aureus Small Colony Variants

A burdensome, atypical phenotype of Staphylococcus aureus (SA) called S aureus small colony variant (SA-SCV) has been identified, which is induced as a result of a combination of environmental stressors, including polymicrobial interactions. The SA-SCVs exhibit altered phenotypes as a result of metabolic dormancy caused by electron transport deficiency, leading to increased biofilm production and alterations to antimicrobial susceptibility. The SA-SCVs typically exhibit altered colony morphology and biochemical reactions compared with wild-type SA, making them difficult to detect via routine diagnostics. The SA-SCVs have been found to contribute to chronic or recurrent infections, including skin and soft-tissue infections, foreign-body associated infection, cystic fibrosis, and sepsis. There is evidence that SA-SCVs contribute to patient morbidity and mortality as a result of diagnostic difficulties and limited treatment options. New detection methods may need to be developed that can be incorporated into routine diagnostics, which would allow for better assessment of specimens and introduce new considerations for treatment.

Bacteriological quality and prevalence of foodborne bacteria in broiler meat sold at live bird markets at Mymensingh City in Bangladesh

OBJECTIVE

This study assessed the bacteriological quality and prevalence of foodborne bacteria in raw broiler meat sold in Mymensingh City.

MATERIALS AND METHODS

Thigh and breast meat samples (n = 80) from broiler chickens were randomly collected from four live bird markets (LBM) in Mymensingh city for bacteriological analysis. To determine the bacteriological quality, a 10-fold serial dilution of the thigh and breast homogenate was made. Then, total viable count (TVC), total coliform count (TCC), Staphylococci, and Salmonella spp. counts were determined using plate count agar, MacConkey agar, Mannitol salt agar, and Salmonella-Shigella agar. Gram stain, biochemical testing, PCR assays, and cultural properties were used to identify the bacterial isolates.

RESULTS

The TVC in the broiler meat sample ranged between log10 8.30 ± 0.54 colony forming unit (CFU)/gm and log10 9.04 ± 0.26 CFU/gm. TCC was found between log10 5.53 ± 0.38 CFU/gm and log10 6.66 ± 0.80 CFU/gm. The mean Staphylococcal count was recorded between log10 4.64 ± 0.61 CFU/gm and log10 6.42 ± 0.53 CFU/gm, and the total Salmonella count ranged between log10 4.75 ± 0.08 CFU/gm and log10 5.69 ± 0.58 CFU/gm. The prevalence of Escherichia coli was the highest (43.2%), followed by Staphylococcus aureus (36.8%) and Salmonella spp. (20%), respectively.

CONCLUSIONS

Data from this study indicated that the TVC and TCC of raw broiler meat sold at LBM exceed the permissible limits and are contaminated with foodborne bacteria, which might cause public health hazards.

Comparison between Some Phenotypic and Genotypic Methods for Assessment of Antimicrobial Resistance Trend of Bovine Mastitis Staphylococcus aureus Isolates from Bulgaria

Simple Summary

The aim of the study was to assess the resistance of bovine mastitis Staphylococcus aureus isolates to antimicrobials by comparison of laboratory methods and statistical analysis. For this, 546 mastitis milk samples at 14 farms from 9 districts in Bulgaria were examined. A total of 92 Staphylococcus aureus strains were isolated and identified. The results showed high resistance to sulfadimethoxine (87%), followed by resistance to penicillin (33.7%), erythromycin (13%), streptomycin (8.7%), tetracycline (6.5%) and gentamicin (1.1%). The comparison of the methods demonstrated more than 90% agreement for 9 tested antimicrobial drugs, hence proving reliability of results from monitoring of resistance. Considering the detected discrepancies for some of isolates, an integral evaluation through standard and modern molecular methods for Staphylococcus aureus is recommended. The results from this study add to the microbiology laboratory experience and strategies for mastitis prevention and control programmes.

Abstract

The aim of this study was to assess the resistance of bovine mastitis S. aureus isolates from farms in Bulgaria to different classes of chemotherapeutic drugs by comparison of some phenotypic and genotypic methods by means of Cohen’s kappa statistics. The study comprised 546 milk samples from subclinical and clinical mastitis at 14 farms from 9 districts in the country. A total of 92 Staphylococcus aureus strains were isolated from tested samples and identified by nuc PCR. The results demonstrated high levels of resistance to sulfadimethoxine (87%), followed by resistance to penicillin (33.7%), erythromycin (13%), streptomycin (8.7%), tetracycline (6.5%) and gentamicin (1.1%). The comparison of both phenotypic tests with respect to 9 antimicrobials revealed strong agreement with kappa coefficient 0.836. An almost complete agreement was evidenced between phenotypic resistance to penicillin and blaZ gene presence, to methicillin with mecA gene, to tetracycline with tet genes, but the agreement between erythromycin resistance and erm genes presence was moderate. This study was the first to demonstrate discrepancy between the behaviour to cefoxitin in the disk diffusion test and oxacillin in the MIC test for an isolate shown to carry the mecA gene in the subsequent genetic analysis. Considering the detected discrepancies for some of isolates, an integral evaluation through phenotypic and molecular methods for monitoring of antimicrobial resistance of Staphylococcus aureus is recommended.

Rapid detection of methicillin-resistant Staphylococcus aureus in positive blood-cultures by recombinase polymerase amplification combined with lateral flow strip

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is an important bacterium that causes community and healthcare-related infections throughout the world. However, the current conventional detection methods are time-consuming. We therefore developed and evaluated a recombinase polymerase amplification-lateral flow strip (RPA-LF) approach for detection of MRSA in positive blood-culture samples. Sixty positive blood-cultures from a hospital were tested directly without DNA extraction and purification before the amplification reaction. RPA primers and probes were designed for nuc (encoding thermonuclease) and mecA (encoding penicillin-binding protein 2a) genes to diagnose S. aureus and its methicillin-resistance status. The RPA reaction occurred under isothermal conditions (45°C) within 20 min and a result was provided by the LF strip in a further 5 min at room temperature. The evaluation of RPA-LF using blood-culture samples showed 93.3% (14/15) sensitivity for identifying S. aureus, and no cross-amplification was seen [100% (45/45) specificity]. For detection of methicillin resistance, the RPA-LF test provided 100% (16/16) sensitivity and 97.7% (43/44) specificity. The RPA-LF is rapid, highly sensitive, robust and easy to use. It can be used for direct detection of MRSA with no requirement for special equipment.

Prevalence, Antimicrobial Resistance, and Molecular Characterization of Campylobacter Isolated from Broilers and Broiler Meat Raised without Antibiotics

Campylobacter is one of the main bacterial pathogens that cause campylobacteriosis in the United States. Poultry is considered a major reservoir for the transmission of Campylobacter to humans. This study aimed to determine the prevalence and molecular characteristics of Campylobacter in the no-antibiotics-ever (NAE) broilers. A total of 414 samples were collected, among which 160 retail chicken samples were purchased from grocery stores and 254 samples were collected from broiler farms located in Mississippi State. The overall prevalence of Campylobacter was 25.4%, and a significantly higher prevalence was observed in retail chicken than in the farm samples (36.3% versus 18.5%; P < 0.0001), respectively. The prevalence of Campylobacter was not different (P = 0.263) between conventional retail (40.0%) and NAE (31.4%) retail chicken. Campylobacter jejuni was the predominant species among the positive isolates, accounting for 78.1%. Among the 82 C. jejuni isolates, 52.4% of the isolates carried the gyrA gene followed by the tet(O) gene (14.6%), whereas toxin-producing genes cdtA, cdtB, and cdtC were carried by 43.9%, 46.3%, and 43.9%, respectively. However, none of these virulence genes were detected in C. jejuni isolated from litter samples. Among tested C. jejuni, 13.6% of the isolates were multidrug resistant. The highest resistance was observed against nalidixic acid (49.2%), followed by tetracycline (23.7%). Our study suggests that the prevalence of Campylobacter was higher in retail meat samples than in environmental samples obtained from farms, and there was no difference in Campylobacter prevalence among conventional and NAE retail chicken. IMPORTANCE The FDA antibiotic withdrawal policy has led to a shift in the production system, from conventional antibiotics fed birds to no antibiotics ever (NAE) raised birds. However, the impact of this shift to NAE on the prevalence and characteristics of Campylobacter has not been studied on the farm or in retail chicken meats. The objective of this study was to determine the current prevalence of Campylobacter and the distribution of their antimicrobial resistance and virulence genes in NAE-raised broilers. The findings of this study will help the industry to take necessary action to develop effective mitigation strategies for reducing Campylobacter contamination in NAE broilers.

Sink survey to investigate multidrug resistance pattern of common foodborne bacteria from wholesale chicken markets in Dhaka city of Bangladesh

Antimicrobial resistance (AMR) among foodborne bacteria is a well-known public health problem. A sink survey was conducted to determine the AMR pattern of common foodborne bacteria in cloacal swab of broiler chickens and sewage samples from five wholesale chicken markets of Dhaka city in Bangladesh. Bacteria were identified by culture-based and molecular methods, and subjected to antimicrobial susceptibility testing. Resistance genes were identified by multiplex PCR and sequencing. Multidrug resistance (MDR) was observed in 93.2% of E. coli, 100% of Salmonella spp., and 97.2% of S. aureus from cloacal swab samples. For sewage samples, 80% of E. coli, and 100% of Salmonella and S. aureus showed MDR. Noteworthy, 8.3% of S. aureus from cloacal swab samples showed possible extensively drug resistance. Antimicrobial resistance genes (beta-lactamase-blaTEM, blaSHV; quinolone resistance gene-qnrS) were detected in a number of E. coli and Salmonella isolates from cloacal swab and sewage samples. The methicillin resistance gene (mecA) was detected in 47.2% and 25% S. aureus from cloacal swab and sewage samples, respectively. The findings envisage the potential public health risk and environmental health hazard through spillover of common foodborne MDR bacteria.

Antimicrobial Susceptibility Profiles and Molecular Characterisation of Staphylococcus aureus from Pigs and Workers at Farms and Abattoirs in Zambia

Pigs have been shown to be a reservoir for recently emerging livestock-associated Staphylococcus aureus (LA-SA), including methicillin resistant strains in many countries worldwide. However, there is sparse information about LA-SA strains circulating in Zambia. This study investigated the prevalence, phenotypic and genotypic characteristics of S. aureus from pigs and workers at farms and abattoirs handling pigs in Lusaka Province of Zambia. A total of 492 nasal pig swabs, 53 hand and 53 nasal human swabs were collected from farms and abattoirs in selected districts. Standard microbiological methods were used to isolate and determine antimicrobial susceptibility patterns of S. aureus. Polymerase Chain Reaction was used to confirm the species identity and detect antimicrobial resistance and virulence genes of isolates, whereas genetic diversity was evaluated using spa typing. Overall prevalence of S. aureus was 33.1%, 37.8% for pigs and 11.8% for humans. The isolates were resistant to several antibiotics with resistance ranging from 18% to 98% but were all susceptible to vancomycin. Typical LA-SA spa types were detected. The presence of plasmid mediated resistance genes such as tetM (12.8%), other resistance determinants and immune evasion cluster genes among the isolates is of great public health concern. Thus, continuous surveillance of S. aureus using a “One health” approach is warranted to monitor S.aureus infections and spread of antimicrobial resistance.

Prevalence of Livestock-Associated MRSA ST398 in a Swine Slaughterhouse in Guangzhou, China

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is an important zoonotic microorganism that is increasingly causing public health concern worldwide. The objective of this study was to determine the transmission and occurrence of MRSA in a slaughterhouse environment and evaluate its antimicrobial resistance and genetic characterization. In this study, we conducted a comprehensive epidemiological survey of S. aureus by spa typing and whole-genome sequencing (WGS) of samples obtained from the pork production chain, the environment, and community residents. To clarify the evolutionary relationships of MRSA sequence type (ST) 398 in this study and global isolates, 197 published whole-genome sequences data of MRSA ST398 strains were downloaded from the GenBank database and included in the phylogenetic analysis. A total of 585 porcine samples (snout and carcass swabs), 78 human nasal samples, and 136 environmental samples were collected. The MRSA isolates were detected at higher frequencies in samples from swine (15.0%) than carcasses (10.0%), slaughterhouse workers (8.0%), community residents (0%), and environment samples (5.9%). The spa typing results showed that t571 accounted for a higher proportion than other spa types. Closely related isolates from the samples of swine, slaughterhouse workers, carcasses, carrier vehicle, and surrounding fishpond water indicate that MRSA ST398 strains may spread among swine, humans, and the environment. MRSA ST398-t571 isolates were genetically different from global strains, except for two Korean isolates, which showed genetic closeness with it. In addition, a MRSA ST398 isolate recovered from an infected patient in Europe differed by only 31 SNPs from the airborne dust-associated strain isolated in this study, thereby suggesting potential transmission among different countries. Antimicrobial susceptibility testing results demonstrated that 99.0% (96/97) of MRSA and 95.1% (231/243) of methicillin-sensitive S. aureus (MSSA) showed multidrug-resistant (MDR) phenotypes. According to WGS analysis, the poxtA-carrying segment (IS431mec-optrA-IS1216-fexB-IS431mec) was reported in MRSA ST398 isolates for the first time. The coexistence of cfr and optrA in a plasmid was first detected in MRSA ST398. The potential transmission of MRSA among humans, animals, and the environment is a cause for concern. The emergence and transmission of LA-MRSA ST398 with high levels of resistance profiles highlight the urgent need for LA-MRSA surveillance.

Staphylococcus aureus and Methicillin-Resistant Coagulase-Negative Staphylococci in Nostrils and Buccal Mucosa of Healthy Camels Used for Recreational Purposes

Several different species of animals host staphylococci as normal microbiota. These animals can be a source of staphylococci zoonotic infections. People with routine or occupational exposure to infected/colonized animals are at risk of a potential transmission. Therefore, we aimed to investigate the presence of S. aureus and other staphylococci in camels used for recreational purposes as well as their antimicrobial resistance, virulence factors and genetic lineages. A total of 172 samples were collected from 86 healthy camels (nose and mouth) from different farms located in the Canary Islands, Spain. Antimicrobial susceptibility testing was performed against 14 antimicrobial agents. The presence of virulence genes was studied by PCR. Multilocus sequence typing, spa typing and agr typing were performed in all S. aureus isolates. From the 86 camels tested, 42 staphylococci were isolated, of which there were 11 S. aureus, 13 S. lentus, 12 S. sciuri, 3 S. xylosus, S. epidermidis, S. hominis and S. chromogenes. Staphylococci isolates were resistant to penicillin, ciprofloxacin, clindamycin and fusidic acid. All S. aureus isolates harbored the hla, hlb and hld virulence genes. S. aureus isolates were ascribed to three sequence types (STs) and three spa types. All S. aureus isolates belonged to agr type III. Camels from Gran Canaria used in recreational purposes have a moderate prevalence of S. aureus and other coagulase-negative staphylococci. Nevertheless, S. aureus isolates are susceptible to almost all antibiotics tested.

Epidemiology and molecular characterization of Staphylococcus aureus causing bovine mastitis in water buffaloes from the Hazara division of Khyber Pakhtunkhwa, Pakistan

Buffalo represent a major source of milk in Pakistan. However, production is impacted by the disease bovine mastitis. Mastitis causes significant economic losses, with Staphylococcus aureus (S. aureus) being one of its major causative agents. While much work has been done understanding the epidemiology of bovine mastitis in Pakistan, detailed molecular characterization of the associated S. aureus is unavailable. In the current study both the epidemiological and molecular characterization of S. aureus from bovine mastitis in the Hazara division of Pakistan are examined. S. aureus was isolated from 18.41% of the animals, and left quarters more prone to infection (69.6%) than right quarters (30.4%). Sub-clinical mastitis (75.31%) was more prevalent than clinical mastitis (24.69%), with infections evenly distributed amongst the eight districts. Molecular characterization revealed that only 19.6% of the isolates were methicillin-resistant, and four strains types identified, including ST9-t7867-MSSA, ST9-MSSA, ST101-t2078-MSSA, and ST22-t8934-MRSA-IVa. Antiseptic resistance genes were not detected in the isolates, and low levels of antibiotic resistance were also noted, however the methicillin-resistant strains had higher overall antibiotic resistance. This study represents the most complete molecular typing data for S. aureus causing bovine mastitis in the Hazara district of Pakistan, and the country as a whole.

Antimicrobial Resistance and Clonal Lineages of Staphylococcus aureus from Cattle, Their Handlers, and Their Surroundings: A Cross-Sectional Study from the One Health Perspective

Staphylococcus aureus have been progressively identified in farm animals and in humans with direct contact with these animals showing that S. aureus may be a major zoonotic pathogen. Therefore, we aimed to isolate S. aureus from cows, their handlers, and their immediate surroundings, and to investigate the antimicrobial resistance and genetic lineages of the isolates. Mouth and nose swabs of 244 healthy cows (195 Maronesa, 11 Holstein-Friesians, and 28 crossbreeds), 82 farm workers, 53 water and 63 soil samples were collected. Identification of species was carried out by MALDI-TOF MS Biotyper. The presence of antimicrobial resistance genes and virulence factors was assessed based on gene search by PCR. All isolates were typed by multilocus sequence typing and spa-typing. From 442 samples, 33 (13.9%), 24 (29.3%), 1 (2%), and 1 (2%) S. aureus were recovered from cows, farm workers, water, and soil samples, respectively. Most of the isolates showed resistance only to penicillin. S. aureus isolates were ascribed to 17 sequence types (STs) and 26 spa-types. Some clonal lineages were common to both cows and farm workers such as ST30-t9413, ST72-t148, and ST45-t350. Through a One Health approach, this study revealed that there is a great diversity of clonal lineages of S. aureus in cows and their handlers. Furthermore, some S. aureus lineages are common to cows and handlers, which may suggest a possible transmission.

Multidrug-Resistant Methicillin-Resistant Coagulase-Negative Staphylococci in Healthy Poultry Slaughtered for Human Consumption

Coagulase-negative staphylococci are commensals that are known to be prevalent in most environments, and they are also an important reservoir of antimicrobial-resistant genes. Staphylococcal infections in animal husbandry are a high economic burden. Thus, we aimed to determine the prevalence and species diversity of methicillin-resistant coagulase-negative staphylococci (MRCoNS) in poultry slaughtered for human consumption and to study the antimicrobial resistance of the isolates. Swab samples were recovered from 220 commercial chickens, homebred chickens and quails. Species identification was performed using MALDI-TOF. Antimicrobial susceptibility testing was performed by the disc diffusion method against 14 antimicrobials. The presence of antimicrobial-resistant genes was investigated by polymerase chain reaction. Totals of 11 (19.6%), 13 (20.3%), and 51 (51%) MRCoNS were isolated from commercial chickens, homebred chickens and quails, respectively. S. lentus was isolated from all homebred chickens, whereas 11 S. lentus and 2 S. urealyticus were isolated from commercial chickens. As for quails, the most prevalent MRCoNS were S. urealyticus. Almost all isolates had a multidrug-resistant profile and carried the mecA gene. Most isolates showed resistance to erythromycin, clindamycin, penicillin, tetracycline, ciprofloxacin and fusidic acid and harbored the ermA, ermB, ermC, mphC tetK, tetL, tetM and tetO genes. This study showed a frequent occurrence of multidrug resistance in MRCoNS isolated from healthy poultry in Portugal.

The Prevalence and Molecular Biology of Staphylococcus aureus Isolated from Healthy and Diseased Equine Eyes in Egypt

This work aimed to characterize S. aureus isolates from the eyes of healthy and clinically affected equines in the Kafrelsheikh Governorate, Egypt. A total of 110 animals were examined for the presence of S. aureus, which was isolated from 33 animals with ophthalmic lesions and 77 healthy animals. We also investigated the antimicrobial resistance profile, oxacillin resistance mechanism, and the major virulence factors implicated in many studies of the ocular pathology of pathogenic S. aureus. The association between S. aureus eye infections and potential risk factors was also investigated. The frequency of S. aureus isolates from clinically affected equine eyes was significantly higher than in clinically healthy equids. A significant association was found between the frequency of S. aureus isolation from clinically affected equine eyes and risk factors including age and season but not with sex or breed factors. Antimicrobial resistance to common antibiotics used to treat equine eyes was also tested. Overall, the isolates showed the highest sensitivity to sulfamethoxazole (100%) and the highest resistance to cephalosporin (90.67%) and oxacillin (90.48%). PCR was used to demonstrate that mecA was present in 100% of oxacillin- and β-lactam-resistant S. aureus strains. The virulence factor genes Spa (x region), nuc, and hlg were identified in 62.5%, 100%, and 56%, of isolates, respectively, from clinically affected equines eyes. The severity of the eye lesions increased in the presence of γ-toxin-positive S. aureus. The phylogenetic tree of the Spa (x region) gene indicated a relationship with human reference strains isolated from Egypt as well as isolates from equines in Iran and Japan. This study provides insight into the prevalence, potential risk factors, clinical pictures, zoonotic potential, antimicrobial resistance, and β-lactam resistance mechanism of S. aureus strains that cause eye infection in equines from Egypt.

Comparison of Methods for Detecting Methicillin-Resistant Coagulase-Negative Staphylococci in Device-Associated Infections

Background:

Coagulase-negative Staphylococci (CoNS) is one of the major causes of infections in hospitals. Methicillin resistance has greatly increased in different CoNS species in previous years. Here, we evaluated the performance of four phenotypic tests for detecting mecA-mediated methicillin resistance rate in CoNS isolated from different device-associated infections in Tanta University Hospitals, Egypt.

Methodology:

One hundred and fifteen CoNS isolates were examined for mecA-mediated methicillin resistance using polymerase chain reaction (PCR) as the standard gold test. Susceptibility to methicillin was investigated using VITEK 2 assay, oxacillin broth microdilution, and cefoxitin disc diffusion tests.

Results:

Of all isolates, 98.3% were mecA-positive. The sensitivities of the different methods examined were as follows: 100% for the VITEK cefoxitin test, 97.4% for the VITEK oxacillin test, 93.8% for the oxacillin broth microdilution, and 82.3% for the cefoxitin disc diffusion test. The test specificity could not be accurately determined because of the small number of mecA-negative isolates (n = 2).

Conclusion:

The rate of methicillin resistance reached 98.3% among CoNS isolates. Our results demonstrate that the VITEK 2 assay is rapid and has high sensitivity compared to other phenotypic methods for detecting methicillin resistance among different species of CoNS. Therefore, we recommend the dual measurement of both cefoxitin and oxacillin susceptibilities using the VITEK 2 assay for best results.

Distribution and Clonal Diversity of Staphylococcus aureus and Other Staphylococci in Surface Waters: Detection of ST425-t742 and ST130-t843 mecC-Positive MRSA Strains

Natural aquatic environments represent one of the most important vehicles of bacterial dissemination. Therefore, we aimed to isolate staphylococci from surface waters and to investigate the presence of antimicrobial resistance genes and virulence factors as well as the genetic lineages of all Staphylococcus aureus isolates. Staphylococci were recovered from water samples collected from 78 surface waters, including rivers, streams, irrigation ditches, dams, lakes, and fountains. The presence of antimicrobial resistance genes and virulence factors was investigated by PCR. Multilocus sequence typing and spa-typing were performed in all S. aureus isolates. From the 78 water samples, 33 S. aureus, one S. pseudintermedius, and 51 coagulase-negative staphylococci (CoNS) were identified. Among the S. aureus isolates, four MRSA were identified, and all harbored the mecC gene. Fourteen S. aureus were susceptible to all antimicrobials tested and the remaining showed resistance to penicillin, erythromycin and/or tetracycline encoded by the blaZ, ermT, msr(A/B), tetL, and vgaA genes. Regarding the clonal lineages, one mecC-MRSA isolate belonged to spa-type t843 and sequence type (ST) 130 and the other three to t742 and ST425. The remaining S. aureus were ascribed 14 spa-types and 17 sequence types. Eleven species of CoNS were isolated: S. sciuri, S. lentus, S. xylosus, S. epidermidis, S. cohnii spp. urealyticus, S. vitulinus, S. caprae, S. carnosus spp. Carnosus, S. equorum, S. simulans, and S. succinus. Thirteen CoNS isolates had a multidrug resistance profile and carried the following genes: mecA, msr(A/B), mph(C), aph(3′)-IIIa, aac(6′)-Ie–aph(2′’)-Ia, dfrA, fusB, cat_pC221, and tetK. A high diversity of staphylococci was isolated from surface waters including mecCMRSA strains and isolates presenting multidrug-resistance profiles. Studies on the prevalence of antibiotic-resistant staphylococci in surface waters are still very scarce but extremely important to estimate the contribution of the aquatic environment in the spread of these bacteria.

The evaluation of five commercial bacteriophage cocktails against methicillin-resistant Staphylococcus aureus isolated from nasal swab samples

Infections due to methicillin-resistant Staphylococcus aureus (MRSA) are a growing concern for public health resulting in increase in morbidity, length of hospital stay, and cost of treatment. MRSA nasal swab screening may give clinicians additional information for decision of empiric antimicrobial agents. While increasing antibiotic resistance leads to new treatment approaches, bacteriophages are one of the most promising methods for these alternatives. It was aimed to determine the effectiveness of bacteriophages against MRSA isolates. Nasal swab samples were collected from outpatients without any evidence of infection who applied to Hatay, Mersin and Gaziantep family and immigration health centers. A series (35) were isolated from Turkish patients, and G series (64) were isolated from Syrian immigrants. Methicillin resistance was determined phenotypically and genotypically. Also, antibiotic susceptibilities of all isolates were determined against erythromycin, clindamycin, gentamicin, linezolid, rifampicin, and mupirocin. The total antimicrobial resistance rates of isolates were found to be 11%, 28%, 8%, 5%, 16%, 19%, and 29% respectively. The high susceptibility rate against ciprofloxacin (88.8%) was remarkable. The overall susceptibility of MRSA strains to ENKO, INTESTI, PYO, SES, and staphylococcal bacteriophages was 67.7%, 55.5%, 53.5%, 61.6% and 44.4%, respectively. The antibiotic susceptibility rates (except erythromycin) and efficacy of bacteriophages were higher in group A. Considering that high efficacy rates were not achieved in the study and the sensitivity rates of Turkish isolates to all phages were found to be higher than those of Syrian isolates, searching for phages in the geographic regions where the pathogen is common may be helpful to obtain suitable phages for treatment.

Microbial colonization and resistome dynamics in food processing environments of a newly opened pork cutting industry during 1.5 years of activity

BACKGROUND

The microorganisms that inhabit food processing environments (FPE) can strongly influence the associated food quality and safety. In particular, the possibility that FPE may act as a reservoir of antibiotic-resistant microorganisms, and a hotspot for the transmission of antibiotic resistance genes (ARGs) is a concern in meat processing plants. Here, we monitor microbial succession and resistome dynamics relating to FPE through a detailed analysis of a newly opened pork cutting plant over 1.5 years of activity.

RESULTS

We identified a relatively restricted principal microbiota dominated by Pseudomonas during the first 2 months, while a higher taxonomic diversity, an increased representation of other taxa (e.g., Acinetobacter, Psychrobacter), and a certain degree of microbiome specialization on different surfaces was recorded later on. An increase in total abundance, alpha diversity, and β-dispersion of ARGs, which were predominantly assigned to Acinetobacter and associated with resistance to certain antimicrobials frequently used on pig farms of the region, was detected over time. Moreover, a sharp increase in the occurrence of extended-spectrum β-lactamase-producing Enterobacteriaceae and vancomycin-resistant Enterococcaceae was observed when cutting activities started. ARGs associated with resistance to β-lactams, tetracyclines, aminoglycosides, and sulphonamides frequently co-occurred, and mobile genetic elements (i.e., plasmids, integrons) and lateral gene transfer events were mainly detected at the later sampling times in drains.

CONCLUSIONS

The observations made suggest that pig carcasses were a source of resistant bacteria that then colonized FPE and that drains, together with some food-contact surfaces, such as equipment and table surfaces, represented a reservoir for the spread of ARGs in the meat processing facility. Video Abstract.

Comparative study of Staphylococcus aureus from burn patients and healthcare workers in a burn center, Yazd, Iran

Healthcare workers (HCWs) are proposed as the potential source of transmission of Staphylococcus aureus to hospitalized patients, especially in burn units. This study aimed to investigate S. aureus from burn wound infections and those from the nose of HCWs in terms of antibiotic resistance, the presence of Panton-Valentine leucocidin-encoding gene (pvl) and the arginine catabolic mobile element (ACME), and the ability for biofilm formation. Also, the genetic diversity of isolates was assessed using staphylococcal protein A (spa) typing and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, regarding the studied factors, significant differences were found neither between isolates from patients and HCWs nor between methicillin-resistant and methicillin-susceptible isolates (except for multidrug resistance which was significantly higher in MRSA). The most frequent SCCmec types were type I and III. ACME-arcA was only detected in isolates from patients and similarly the presence of ACME-opp3 was the most prevalent in this group. The presence of common clonal complexes among patient isolates and more importantly between isolates from patients and HCWs is warning. The high prevalence of virulence factors, both in MRSA and MSSA, emphasizes the importance of MSSA in burn centers. Finding no significant difference in the presence of virulence-associated factors between isolates from patients and HCWs demonstrates the need to take HCWs into account as important reservoirs.

Frequency, Distribution, and Antimicrobial Resistance of Coagulase-Negative Staphylococci Isolated from Clinical Samples in Dogs and Cats

This study aimed to investigate the frequency, distribution, and antimicrobial resistance of coagulase-negative staphylococci (CoNS) obtained from clinical samples from dogs and cats and to classify any methicillin-resistant CoNS (MRCoNS). The samples were collected in 2017-2018, and species identification and antimicrobial susceptibility testing were routinely performed using the Vitek2 system. Among 1,056 staphylococci, 185 CoNS (17.5%) were obtained and included 18 species from dogs (n = 116) and 14 species from cats (n = 69). The predominant species were Staphylococcus chromogenes (31.4%), Staphylococcus hominis ssp. hominis (16.2%), Staphylococcus warneri (10.8%), and Staphylococcus epidermidis (8.1%). The primary isolation sites were the skin and urinary tract. High levels of resistance to β-lactams (65.4%), tetracycline (44.3%), clindamycin (36.8%), and erythromycin (30.8%) were observed. Twenty-five MRCoNS (13.4%), mainly Staphylococcus haemolyticus (n = 8), S. epidermidis (n = 6), and S. hominis ssp. hominis (n = 5), were identified. SCCmec type V (n = 8) was the most common type, followed by SCCmec type IV (n = 6) and SCCmec type III (n = 2), whereas nontypable SCCmec were classified into nine MRCoNS. Some CoNS have been recorded in humans, and these might be transferred to and cause subsequent infections in humans. Moreover, the diversity of SCCmec types and resistant strains suggested that they may serve as a reservoir of resistance genes among staphylococci.

Prevalence and Characteristics of Multidrug-Resistant Livestock-Associated Methicillin-Resistant Staphylococcus aureus (LA-MRSA) CC398 Isolated from Quails (Coturnix Coturnix Japonica) Slaughtered for Human Consumption

Simple Summary

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in both humans and animals worldwide. MRSA associated with livestock is a zoonotic pathogen that has been reported in several animals and, although its infections in humans are rare, this strain is recognized as an occupational hazard for people working in direct contact with livestock. Thus, we aimed to isolate MRSA from quails and to characterize their antimicrobial resistance and genetic lineages. One hundred swab samples were recovered from quails at the slaughterhouse. To investigate the prevalence and antimicrobial resistance of MRSA in poultry, we conducted this study on 100 quails slaughtered for human consumption. The antimicrobial resistance was investigated in all isolates as well as virulence genes and genetic lineages. Twenty-nine MRSA were isolated. The results showed that all MRSA isolates had resistance to multiple antibiotics. All strains were classified as livestock-associated. Most strains belonged to a well-known livestock-associated lineage: CC398.

Abstract

Livestock-associated MRSA (LA-MRSA) is a zoonotic pathogen that has been reported in several animals, and it is often associated with clonal complex (CC) 398. We aimed to isolate MRSA from quails and to characterize their antimicrobial resistance and genetic lineages. One hundred swab samples were recovered from quails at the slaughterhouse. The swabs were inoculated onto CHROMagar™ MRSA agar plates for MRSA isolation. The presence of antimicrobial-resistant genes and virulence factors was investigated by PCR. All strains were typed by MLST, SCCmec-, spa- and agr-typing. From the 100 samples, 29 MRSA were isolated. All strains were resistant to penicillin, cefoxitin, ciprofloxacin, erythromycin and clindamycin and carried the blaZ, mecA, ermB and ermC genes. All strains, except one, showed resistance to tetracycline and harbored the tetM, tetK and tetL genes in different combinations. Twenty strains belonged to ST398 and SCCmec type V, and nine strains belonged to the new ST6831. Twenty-eight out of twenty-nine strains were ascribed to t011 and one to t108. As far as we know, this is the first report of MRSA from quails slaughtered for human consumption. Most strains belonged to ST398-t011, which is the most common LA-MRSA clone found in livestock in Europe.

Antibiotic susceptibility of human-associated Staphylococcus aureus and its relation to agr typing, virulence genes, and biofilm formation

BACKGROUND AND OBJECTIVE

Carriage of virulence factors confers some evolutionary benefit to bacteria, which favors the resistant strains. We aimed to analyze whether antibiotic susceptibility of Staphylococcus aureus strains is affected by agr typing, biofilm formation ability, and virulence profiles.

METHODS

A total of 123 S. aureus clinical isolates were subjected to antimicrobial susceptibility testing by disk diffusion method, biofilm formation by microtiter plate method, as well as polymerase chain reaction screening to identify virulence genes and the accessory gene regulator (agr) types I-IV. A P value < 0.05 was considered significant.

RESULTS

The most prevalent virulence gene was staphyloxanthin crtN, followed by hemolysin genes, capsular cap8H, toxic shock toxin tst, and enterotoxin sea, respectively. Resistant isolates were more commonly found in the agr-negative group than in the agr-positive group. Isolates of agr type III were more virulent than agr I isolates. Strong biofilm producers showed more antibiotic susceptibility and carried more virulence genes than non-strong biofilm producers. Associations were found between the presence of virulence genes and susceptibility to antibiotics. Carriage of the virulence genes and agr was higher in the inpatients; while, resistance and strong biofilms were more prevalent in the outpatients.

CONCLUSION

These findings indicated the presence of several virulence factors, biofilm production capacity, agr types and resistance to antibiotics in clinical S. aureus isolates. Considering the importance of S. aureus for human medicine, an understanding of virulence and resistance relationships would help to reduce the impact of S. aureus infections.

Antibiotic resistance patterns of Staphylococcus spp. isolated from fast foods sold in different restaurants of Mymensingh, Bangladesh

OBJECTIVE

Fast foods are often responsible for staphylococcal foodborne illness. The present study was carried out to isolate Staphylococcus spp. from various fast foods sold in Mymensingh and to determine their antibiogram.

MATERIALS AND METHODS

Overall, 60 samples of fast foods sold in different restaurants were screened by culture, biochemical tests, and polymerase chain reaction (PCR) to isolate and identify Staphylococcus spp., followed by employing of disk diffusion method to determine their antibiotic resistance patterns.

RESULTS

Among these 60 samples, 8 [13.33%, 95% confidence interval (CI): 6.91%-24.17%] were positive for Staphylococcus spp. by cultural and biochemical properties. By PCR, four (6.67%, 95% CI: 2.62%-15.93%) isolates were confirmed as Staphylococcus aureus by targeting nuc gene. Additionally, all the S. aureus isolates were coagulase-positive. By antibiogram profiles, all the Staphylococcus isolates exhibited resistance to azithromycin and erythromycin (95% CI: 67.56%-100.00%), and frequently resistance to cefixime (75%, 95% CI: 40.93%-95.56%), ampicillin (50%, 95% CI: 21.52%-78.48%), and amoxicillin (37.5%, 95% CI: 13.68%-69.43%); moderate to lower resistance was found against cefotaxime, gentamicin, and doxycycline. In addition, all the isolates were sensitive to ciprofloxacin and chloramphenicol. Interestingly, 75% (6/8; 95% CI: 40.93%-95.56%) isolates were multidrug-resistant (MDR) in nature. Furthermore, the indices of multiple antibiotic resistance (MAR) were ranged from 0.2 to 0.6.

CONCLUSION

This study revealed that fast foods sold in restaurants were contaminated with MDR and MAR Staphylococcus isolates, having potential public health significance.

Antimicrobial Resistance and Genetic Lineages of Staphylococcus aureus from Wild Rodents: First Report of mecC-Positive Methicillin-Resistant S. aureus (MRSA) in Portugal

The frequent carriage of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), by wild animals along with its zoonotic potential poses a public health problem. Furthermore, the repeated detection of the mecA gene homologue, mecC, in wildlife raises the question whether these animals may be a reservoir for mecC-MRSA. Thus, we aimed to isolate S. aureus and MRSA from wild rodents living in port areas and to characterize their antimicrobial resistance and genetic lineages. Mouth and rectal swab samples were recovered from 204 wild rodents. The samples were incubated in BHI broth with 6.5% of NaCl and after 24 h at 37 °C the inoculum was seeded onto Baird-Parker agar, Mannitol Salt agar and ORSAB (supplemented with 2 mg/L of oxacillin) plates. Species identification was confirmed by MALDI-TOF MS. The antimicrobial susceptibility testing was performed by the Kirby-Bauer disc diffusion method against 14 antibiotics. The presence of virulence and resistance genes was performed by PCR. The immune evasion cluster (IEC) system was investigated in all S. aureus. All isolates were characterized by MLST, spa- and agr typing. From 204 samples, 38 S. aureus were isolated of which six MRSA were detected. Among the six MRSA isolates, three harbored the mecC gene and the other three, the mecA gene. All mecC-MRSA isolates were ascribed to sequence type (ST) 1945 (which belongs to CC130) and spa-type t1535 whereas the mecA isolates belonged to ST22 and ST36 and spa-types t747 and t018. Twenty-five S. aureus were susceptible to all antibiotics tested. S. aureus isolates were ascribed to 11 MLST and 12 spa-types. S. aureus presents a great diversity of genetic lineages in wild rodents. This is the first report of mecC-MRSA in Portugal.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Hospitalized Patients in Eastern Heilongjiang Province, China

Background

Recently, owing to antibiotic resistance, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) colonization among intensive care unit (ICU) patients has increased rapidly. So far, there are few studies on active screening of MRSA. The purpose of the current study was to verify the effectiveness of active screening and analyze the molecular epidemiological characteristics of MRSA in the region.

Methods

We collected 30 samples of the MRSA strains from a tertiary hospital in the Eastern Heilongjiang Province. Among them, 7 were retrieved through nasal vestibular swabs at the emergency ICU and 23 were obtained from clinical specimens. Additionally, relevant patient medical information was examined retrospectively and molecular epidemiology and risk factor analysis for MRSA were performed.

Results

Molecular epidemiology studies revealed that all strains of bacteria carried the mecA resistance gene. The Panton Valentine leukocidin (PVL), for instance, was detected at a rate of 13.33% (4/30). The Staphylococcus aureus protein A (spa) types, found amongst our samples, were mainly t324, t437, t034, etc., and we discovered a new spa type t19702. We also revealed 3 types of SCCmec, namely, SCCmec type II, SCCmec type IVa, and SCCmec type V, with the most prevalent clonotypes being ST72 and ST59. In addition, we also found 7 new ST types, namely, ST6567, ST6568, ST6569, ST6570, ST6571, ST6572, and ST6573. Using risk factor analysis, we also demonstrated that long, invasive procedures used in the ICU, such as tracheal intubation and ventilator usage, along with patients with cerebral infarction and other embolism are more susceptible to developing MRSA colonization and further infections.

Conclusion

We recommend the infection control department within hospitals to actively screen for MRSA and perform risk factor analysis in order to establish accurate preventive measures for controlling MRSA spread.

Prevalence and Multidrug Resistance Pattern of Methicillin Resistant S. aureus Isolated from Frozen Chicken Meat in Bangladesh

Infections by methicillin-resistant Staphylococcus aureus (MRSA) are continuously expanding within the community. Chicken meat is usually contaminated by MRSA, and this contaminated chicken meat is an important source of foodborne infections in humans. In this study, a cross-sectional supershop survey was conducted to determine the prevalence and antimicrobial resistance pattern of MRSA in 113 domestic frozen chicken meat samples purchased from nine branded supershops available in five divisional megacities of Bangladesh. The study also focused on the determination of methicillin resistance gene in MRSA isolates. S. aureus was identified by standard culture-based and molecular methods, and subjected to antimicrobial susceptibility testing. MRSA was screened by cefoxitin disk diffusion test. Methicillin resistance gene was identified by PCR. Of samples, 54.9% were positive for S. aureus, and, of these, 37.1% isolates were identified as MRSA. All the isolates were multidrug resistant (MDR): 52.2% were resistant to 6–8 antimicrobial classes, and 47.8% isolates to 9–12 classes. Three (3.2%) isolates of S. aureus were possible extensively drug resistant. The highest rates of resistance were observed against cefoxitin (100%), followed by nalidixic acid, ampicillin and oxacillin (97.7%), colistin (91.3%), amoxicillin-clavulanic acid and amoxicillin (87%), penicillin-G and cloxacillin (82.6%), oxytetracycline (78.3%), and cefixime (73.9%). Screening of methicillin resistance gene revealed that 43.5% isolates of MRSA were positive for mecA gene. The high prevalence of MDR MRSA in frozen chicken meat samples in this study emphasizes the need for better sanitary education of food handlers in hygienic practices focusing on their potential role as reservoirs and spreaders of MRSA.

Multiresistance and virulence factors of Staphylococcus aureus isolated from pigs

ABSTRACT The emergence of livestock-associated methicillin-resistant Staphylococcus aureus strains (LA-MRSA) and the potential role of pigs in the evolution of these strains has led to increased interest in research of these microorganisms. However, this has contributed to a lack of research in the isolation and characterization of methicillin-susceptible S. aureus strains (MSSA). In this study, the prevalence of S. aureus in pigs in the nursery and finishing stages were analyzed. The susceptibility profiles to antibiotics, tolerance to heavy metals, and biofilm production of the isolates were evaluated using phenotypic and genotypic techniques. A total of 1,250 colonies suggestive of Staphylococcus spp. were isolated from 128 pigs, of which 63.6% (n = 795) belonged to this microbial genus. Sixty-seven colonies isolated from 34 animals (26.5%) were confirmed as S. aureus (8.4%). No strains resistant to copper, zinc, or methicillin were detected; however, all strains presented a resistance profile to at least three different classes of antimicrobials and 21 produced biofilms. These data are of concern, as they indicate the need for increased surveillance in the use of antimicrobials as well as reinforce the importance of studies on MSSA strains.

Multidrug resistant staphylococci isolated from pigs with exudative epidermitis in North eastern Region of India

Exudative epidermatitis or greasy pig disease (GPD) is a contagious disease of pig and endemic worldwide caused by toxigenic strains under genus Staphylococcus. The present study reported an outbreak of GPD in Champhai district of Mizoram adjoining to the southern border of Myanmar. A total of 60 samples were collected from 22 clinically affected animals and processed for isolation and identification of Staphylococcus spp. All the isolates were subjected to antimicrobial sensitivity assay, biofilm production assay and detection of virulence genes, biofilm genes and mec genes followed by cloning and sequencing for phylogenetic analysis. A total of 44 staphylococci belonged to four species (S. sciuri, S. aureus,S. lentus, and S. hyicus) were isolated. Majority of the isolates were multidrug resistant with maximum resistance against ampicillin, penicillin including vancomycin. None of the S. hyicus isolates was methicillin resistant (MRSH) but 66·67% isolates were MRSA. By PCR, mecA gene was detected in S. aureus (n = 2), S. sciuri (n = 4) and S. lentus (n = 3). Biofilm associated gene icaD was detected in S. aureus (n = 3), S. sciuri (n = 5), S. hyicus (n = 4) and S. lentus (n = 6). The exfoliative toxin genes (ehxB, shetA and tsst1) were detected in S. hyicus (n = 3) and S. aureus (n = 1) isolates. All the isolates were closely related with the isolates from pigs of China, Germany, Japan and USA. The pathogens might be transmitted through illegal migration of pigs from Myanmar to India.

Livestock-Associated and Non-Livestock-Associated Staphylococcus aureus Carriage in Humans is Associated with Pig Exposure in a Dose-Response Manner

Background

The distinction between livestock-associated and human-associated methicillin-resistant Staphylococcus aureus (MRSA) has become more and more blurred. This study aimed to reveal the transmission risk of livestock-associated and non-livestock-associated S. aureus (including MRSA and multidrug-resistant S. aureus [MDRSA]) by occupational pig exposure.

Methods

A total of 591 pig-exposed workers and 1178 non-exposed workers were enrolled in this study. All nasal S. aureus isolates were tested for antibiotic susceptibility and molecular characteristics. Logistic regression models were used to examine the dose–response relationships between occupational pig exposure and S. aureus carriage.

Results

Pig-exposed workers had significantly higher carriage rates of MRSA (OR=6.29, 95% CI: 3.38~11.68) and MDRSA (OR=3.17, 95% CI: 2.03~4.96) than non-exposed workers. Notably, we found dose–response relationships between occupational pig exposure and MRSA or MDRSA carriage. Using genotypic and phenotypic markers for differentiating livestock-associated and non-livestock-associated S. aureus, we also revealed dose–response relationships occupational pig exposure and livestock-associated or non-livestock-associated S. aureus carriage.

Conclusion

Our findings provide sufficient epidemiological evidence for revealing the high transmission risk of livestock-associated S. aureus and the low transmission risk of non-livestock-associated S. aureus by occupational pig exposure.

Phenotypic and Molecular Characteristics of Community-Associated Staphylococcus aureus Infection in Neonates

Background

Staphylococcus aureus is an important human pathogen causing a wide variety of diseases ranging from mild skin infections to life-threatening bacteremia. This study aimed to provide insight into the phenotype-genotype characteristics of S. aureus isolated from neonates.

Methods

A hospital-based retrospective study was conducted to recruit neonatal patients with community-associated S. aureus infection. All 92 S. aureus clinical isolates were tested for antimicrobial susceptibility, resistance genes, virulence genes, and multilocus sequence typing.

Results

A total of 92 S. aureus isolates were included in this study, including 29 (31.5%) MRSA isolates. Most S. aureus isolates were susceptible to gentamicin, and most methicillin-resistant S. aureus (MRSA) isolates were susceptible to vancomycin and linezolid. The predominant S. aureus genotypes were CC188 (ST188), CC59 (ST338), CC5 (ST5), CC88 (ST8), and CC6 (ST6), with CC59 (ST338) as the most prevalent MRSA. We observed a significantly corresponding relationship between clonal complexes and resistance patterns (such as CC45/CC59/CC121/CC630 associated with multidrug resistance) or the number of virulence genes (such as CC1/CC5/CC45/CC59/CC88 associated with harboring 5-7 virulence genes, and CC22/CC25/CC121 associated with carrying 8-13 genes). Moreover, both univariate and multivariate analyses indicated that invasive S. aureus isolates were significantly associated with resistance to several classes of antibiotics and carrying specific virulence factors.

Conclusion

Our findings provide insight into phenotype-genotype characteristics for S. aureus isolates so as to provide new ideas for differentiating potential genetic backgrounds and monitoring new epidemiologic trends.

Pet birds as potential reservoirs of virulent and antibiotic resistant zoonotic bacteria

Bacterial pathogens carried by pet birds are considered a risk for birds, workers, and pet owners. This study investigated the potential of pet birds as reservoirs for virulent multidrug-resistant (MDR) zoonotic bacteria and assessed the genetic relatedness and diversity of bacterial isolates from pet birds and human contacts. Cloacal and tracheal swabs from 125 pet birds and 70 hand swabs from human contacts were collected. The results revealed that the pet birds were reservoirs for Escherichia coli, Klebsiella pneumoniae (17.6 %, each), and Staphylococcus aureus (15.2 %). These isolates were also identified in their human contacts, at percentages of 14.3 %, 12.9 %, and 24.3 %, respectively. Virulence associated genes were identified from E. coli (stx2, stx2f, eaeA, and hlyA), K. pneumoniae (fimH, TraT, and magA), and S. aureus (PVL, hly, sea, sed genes) isolates. Multidrug-resistant E. coli, K. pneumoniae, and S. aureus were highly prevalent (81.3 %, 90.3 %, and 61.1 %, respectively). The genetic relationship between the E. coli and K. pneumoniae isolates from the pet birds and human contacts were determined by ERIC-PCR, while, RAPD-PCR was used for the S. aureus isolates. ERIC-PCR was found to have the highest discriminatory power. The clustering of the isolates from the pet birds and human contacts indicated potential transmission between the birds and workers. In conclusion, pet birds could act as potential reservoirs for zoonotic bacterial pathogens; thus, posing a risk to their human contacts.

Methicillin-resistant Staphylococcus aureus (MRSA) associated with mastitis among water buffaloes in the Philippines

Methicillin-resistant Staphylococcus aureus (MRSA) from dairy animals could pose a public health concern in the population. The study was designed to determine the prevalence of S. aureus and MRSA associated with mastitis among water buffaloes in the central part of Luzon island, the Philippines, and to investigate its associated factors. Three hundred and eighty-four water buffaloes were examined for mastitis using California mastitis test (CMT). Composite milk samples (n = 93) were collected from buffaloes showing positive reaction with CMT. S. aureus was identified from milk samples using biochemical tests. Cefoxitin disk diffusion assay and PCR detecting mecA gene were performed to identify MRSA isolates. Disk diffusion assay was used to investigate the antimicrobial resistance against 9 antibiotics. The prevalence of S. aureus was 41.94% (39/93). MRSA isolates resistant to cefoxitin were at 25.81% (24/93) but only 37.5% (9/24) harbored the mecA gene. All 24 MRSA isolates were resistant to penicillin while the majority were susceptible to clindamycin, trimethoprim-sulfamethoxazole, gentamycin, tetracycline, rifampicin, ciprofloxacin and chloramphenicol with intermediate susceptibility to erythromycin. Furthermore, 37.5% of the isolates were found resistant to two or more antibiotics. Animal-level factor associated with MRSA infection was the history of mastitis (OR = 3.18, CI = 1.03-9.79, p = 0.040). Herd-level factors associated with the detection of MRSA in milk included herd size (OR = 4.24, CI = 1.05-17.07, p = 0.042) and the presence of other animals (OR = 0.15, CI = 0.04-0.58, p = 0.006). High prevalence of intramammary infection with S. aureus and MRSA in dairy buffaloes was observed in the region. This finding raises the concern of preventing zoonotic spread of MRSA.