Methicillin-resistant Staphylococcus aureus carrying the new mecC gene--a meta-analysis

Nanobiotics against antimicrobial resistance: harnessing the power of nanoscale materials and technologies

Given the spasmodic increment in antimicrobial resistance (AMR), world is on the verge of “post-antibiotic era”. It is anticipated that current SARS-CoV2 pandemic would worsen the situation in future, mainly due to the lack of new/next generation of antimicrobials. In this context, nanoscale materials with antimicrobial potential have a great promise to treat deadly pathogens. These functional materials are uniquely positioned to effectively interfere with the bacterial systems and augment biofilm penetration. Most importantly, the core substance, surface chemistry, shape, and size of nanomaterials define their efficacy while avoiding the development of AMR. Here, we review the mechanisms of AMR and emerging applications of nanoscale functional materials as an excellent substitute for conventional antibiotics. We discuss the potential, promises, challenges and prospects of nanobiotics to combat AMR.

Antimicrobial resistance in commensal Staphylococcus aureus from wild ungulates is driven by agricultural land cover and livestock farming

Staphylococcus aureus is a human pathobiont (i.e., a commensal microorganism that is potentially pathogenic under certain conditions), a nosocomial pathogen and a leading cause of morbidity and mortality in humans. S. aureus is also a commensal and pathogen of companion animals and livestock. The dissemination of antimicrobial resistant (AMR) S. aureus, particularly methicillin-resistant (MRSA), has been associated to its ability for establishing new reservoirs, but limited attention has been devoted to the role of the environment. To fill this gap, we aimed to characterize animal carrier status, AMR phenotypes, predominant clonal lineages and their relationship with clinical and food-chain settings, as well as to find predictors of AMR occurrence. Nasal swabs (n = 254) from wild boar (n = 177), red deer (n = 54) and fallow deer (n = 23) hunted in Portugal, during the season 2019/2020, yielded an overall carrier proportion of 35.8%, ranging from 53.7% for red deer and 32.2% for wild boar to 21.7% for fallow deer. MRSA from wild boar and phenotypically linezolid-resistant S. aureus from wild boar and red deer were isolated, indicating that resistance to antimicrobials restricted to clinical practice also occurs in wildlife. The most prevalent genotypes were t11502/ST2678 (29.6%) and t12939/ST2678 (9.4%), previously reported in wild boar from Spain. Clonal lineages reported in humans and livestock, like CC1, CC5 or CC8 (19.1%) and ST425, CC133 or CC398 (23.5%), respectively, were also found. The sequence type ST544, previously restricted to humans, is described in wildlife for the first time. We also identified that land use (agricultural land cover), human driven disturbance (swine abundance) and host-related factors (sex) determine resistance occurrence. These findings suggest that antibiotics used in clinical settings, agriculture and livestock farming, spill over to wildlife, leading to AMR emergence, with potential biological, ecological, and human health effects. This work is one of the most comprehensive surveys in Europe of S. aureus occurrence and determinants among widely distributed wild ungulates.

Comparison of rapid and conventional methods for investigating of mecA presence in Staphylococcus Species

Objectives:

Taking the determination of mecA gene by polymerized chain reaction (PCR) method as a reference in determining methicillin resistance in Staphylococcus species, we aimed at comparing the reliability levels of disk diffusion, latex agglutination test and chromogenic agar use methods.

Methods:

This prospective study was conducted on 228 Staphylococcus strains isolated between January 2020 and December 2020 in Samsun Training and Research Hospital. Disk diffusion, latex agglutination and chromogen agar medium methods were applied along with the polymerized chain reaction (PCR) method.

Results:

The mecA gene was detected in 47 of the isolates (20.6%) by the PCR method, and these isolates were accepted as methicillin-resistant. When the PCR result was taken as a reference, the sensitivity of the disk diffusion method became 100%, and specificity became 45.9%; sensitivity of latex agglutination was determined as 80.9%, and specificity as 70.2%; sensitivity of chromogenic agar as 85.1% and its specificity was found to be 95%. Only in S. aureus isolates, the highest sensitivity and specificity rate (100% and 88%, respectively) belonged to chromogenic agar.

Conclusion:

Chromogenic agar provides more reliable data for S. aureus isolates, and the combined use of all three methods does not significantly increase reliability.

Antibacterial Activity of a Promising Antibacterial Agent: 22-(4-(2-(4-Nitrophenyl-piperazin-1-yl)-acetyl)-piperazin-1-yl)-22-deoxypleuromutilin

A novel pleuromutilin derivative, 22-(4-(2-(4-nitrophenyl-piperazin-1-yl)-acetyl)-piperazin-1-yl)-22-deoxypleuromutilin (NPDM), was synthesized in our laboratory and proved excellent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). In this study, more methods were used to further study its preliminary pharmacological effect. The antibacterial efficacy and toxicity of NPDM were evaluated using tiamulin as the reference drug. The in vitro antibacterial activity study showed that NPDM is a potent bactericidal agent against MRSA that induced time-dependent growth inhibition and a concentration-dependent post-antibiotic effect (PAE). Toxicity determination showed that the cytotoxicity of NPDM was slightly higher than that of tiamulin, but the acute oral toxicity study proved that NPDM was a low-toxic compound. In an in vivo antibacterial effect study, NPDM exhibited a better therapeutic effect than tiamulin against MRSA in a mouse thigh infection model as well as a mouse systemic infection model with neutropenia. The 50% effective dose (ED50) of NPDM in a Galleria mellonella infection model was 50.53 mg/kg. The pharmacokinetic properties of NPDM were also measured, which showed that NPDM was a rapid elimination drug in mice.

Can the Xpert MRSA/SA BC assay be used as an antimicrobial stewardship tool? A prospective assay validation and descriptive impact assessment study in a South African setting

BACKGROUND

Positive blood cultures showing Gram positive cocci in clusters signifies either Staphylococcus aureus or the less-virulent coagulase-negative staphylococci. Rapid identification and methicillin susceptibility determination with the Xpert MRSA/SA BC assay can improve management of S. aureus bloodstream infection and reduce inappropriate antibiotic use.

METHODS

We prospectively evaluated the Xpert MRSA/SA BC assay in comparison with culture, on samples referred to our laboratory in the Western Cape, South Africa. We interviewed attending clinicians upon culture result availability, to assess antibiotic choices and estimate potential impact of the assay.

RESULTS

Of the 231 samples included, there was 100% concordance between the Xpert MRSA/SA BC assay and culture (methicillin-resistant S. aureus 15/15, methicillin-susceptible S. aureus 42/42, coagulase-negative staphylococci 170/170). Time to final result could be reduced by approximately 30 h with the assay. Of the 178 patients with adequate antibiotic history, optimisation of antistaphylococcal therapy could have occurred more than 1 day sooner in 68.9% with S. aureus bloodstream infection (31/45, 95% CI 53.2-81.4%). Six of the 11 patients with methicillin-resistant S. aureus bloodstream infection (54.5%) could have received anti-MRSA cover sooner. Fifty-four days of antibiotic therapy could have been spared, equating to 0.3 days (95% CI, 0.2-0.4) saved per patient, driven by broad-spectrum beta-lactams (32 days, in 18.0% of the cohort).

CONCLUSION

This assay has potential as an antimicrobial stewardship tool; costing and impact on clinical outcome in patients with S. aureus bloodstream infection should be assessed.

Human mecC-Carrying MRSA: Clinical Implications and Risk Factors

A new methicillin resistance gene, named mecC, was first described in 2011 in both humans and animals. Since then, this gene has been detected in different production and free-living animals and as an agent causing infections in some humans. The possible impact that these isolates can have in clinical settings remains unknown. The current available information about mecC-carrying methicillin resistant S. aureus (MRSA) isolates obtained from human samples was analyzed in order to establish its possible clinical implications as well as to determine the infection types associated with this resistance mechanism, the characteristics of these mecC-carrying isolates, their possible relation with animals and the presence of other risk factors. Until now, most human mecC-MRSA infections have been reported in Europe and mecC-MRSA isolates have been identified belonging to a small number of clonal complexes. Although the prevalence of mecC-MRSA human infections is very low and isolates usually contain few resistance (except for beta-lactams) and virulence genes, first isolates harboring important virulence genes or that are resistant to non-beta lactams have already been described. Moreover, severe and even fatal human infection cases have been detected. mecC-carrying MRSA should be taken into consideration in hospital, veterinary and food safety laboratories and in prevention strategies in order to avoid possible emerging health problems.

Phenotype and Genotype Characteristics of Staphylococcus aureus Resistant to Methicillin/Oxacillin Carrying Gene mecC in the Czech Republic from 2002 to 2017

The aim of this study was to detect and characterize isolates of methicillin-/oxacillin-resistant Staphylococcus aureus (MRSA) carrying gene mecC (MRSA/mecC) and occurring in the Czech Republic within the period from 2002 to 2017. Altogether, 18 from 3,472 isolates of MRSA were mecC positive (0.52%). The first detection of MRSA/mecC in the Czech Republic is dated to 2004. MRSA/mecC isolates were susceptible to almost all tested antibiotics with few exceptions. Resistances to erythromycin (n = 2), clindamycin (n = 1), trimethoprim-sulfamethoxazole (n = 1), and rifampicin (n = 1) were found in the collection. Multilocus sequence typing and spa typing revealed a genetic heterogeneity of MRSA/mecC strains: three CCs (130, 425, and 2361), five STs (1245, 130, 2361, 425, and a new ST5480), and eight spa types (t843, t978, t1048, t1535, t1736, t6104, t8842, and t17153), which were detected in the study, with the highest prevalence of CC130/t843 lineage (n = 8, 44%). Except for two strains, none from 18 examined isolates harbored genes encoding any of S. aureus toxins: enterotoxins a-u, exfoliative toxins A, B, and D, toxic shock syndrome toxin-1, and the Panton-Valentine leukocidin.

Using genomics to understand meticillin- and vancomycin-resistant Staphylococcus aureus infections

Resistance to meticillin and vancomycin in Staphylococcus aureus significantly complicates the management of severe infections like bacteraemia, endocarditis or osteomyelitis. Here, we review the molecular mechanisms and genomic epidemiology of resistance to these agents, with a focus on how genomics has provided insights into the emergence and evolution of major meticillin-resistant S. aureus clones. We also provide insights on the use of bacterial whole-genome sequencing to inform management of S. aureus infections and for control of transmission at the hospital and in the community.

Genotyping and antimicrobial resistance of Staphylococcus aureus isolates from dairy ruminants: differences in the distribution of clonal types between cattle and small ruminants

Staphylococcus aureus is part of the normal flora of animals, and represents one of the leading causes of contagious mastitis in dairy herds worldwide. Sixty-seven epidemiologically unrelated S. aureus isolates from nasal and mastitis milk samples of dairy-producing animals (32 cows, 25 sheep, and 10 goats) were characterized by antimicrobial susceptibility testing and spa typing followed by multilocus sequence typing (MLST) on representative isolates and SCCmec-typing on methicillin-resistant S. aureus (MRSA) isolates. The highest resistance was observed to penicillin (64.2%, 43/67), followed by tetracycline (23.9%, 16/67), erythromycin (22.4%, 15/67), and streptomycin (17.9%, 12/67). In general, 18 spa types (including newly identified t16958) and 13 sequence types (STs) belonging to 8 clonal complexes (CCs) were detected. The cow-associated isolates were mainly assigned to CC5 (n = 18, related to t267-ST97, t521-ST352, t527-ST97, t304-ST6, and t084-ST15), followed by CC398 (n = 6, t937-ST291), CC45 (n = 3, t230-ST45), CC88 (n = 2, t2526-ST88), CC22 (n = 2, t3680-ST22), and CC522 (n = 1, t3576-ST522). Small ruminant isolates were mostly clustered into CC522 (n = 29, related to t3576, t1534, t16958, t7308, t7311, t7305 [ST522], t1534-ST2057, and t5428-ST2079). Two isolates from cows with mastitis were found to be MRSA, exhibited a composite profile of t937-ST291-SCCmecIV. No isolates carried the PVL and mecC genes. A significant difference in clonal types of S. aureus isolates from cows in comparison with those from small ruminants was found. This study demonstrated the circulation of diverse clones of S. aureus among dairy animals in Iran, with a different clonal composition between cows and small ruminants. The current study also reports MRSA-related mastitis in dairy cows, emphasizing the need for comprehensive surveillance.

Biology and management of methicillin resistant Staphylococcus aureus in cystic fibrosis

Staphylococcus aureus is one of the earliest bacteria isolated from the respiratory tract in people with cystic fibrosis (CF). Its methicillin resistant form, MRSA, has gained attention due to the rapid increase in the last decades and worse outcomes with chronic infection. In the United States, prevalence of MRSA in CF is around 27%, but is much lower (3-18%) in most other countries. Methicillin is typically genetically encoded by the mecA gene, which encodes for an alternative penicillin binding protein (PRBa). This PRBa has low affinity to β-lactams, thereby enabling growth of S. aureus in the presence of penicillinase resistant penicillins and most other β-lactams. Non-mecA positive strains of MRSA, so-called borderline resistant (BORSA) have also been described. In addition to production of toxins, the virulence of S. aureus is conferred by its adaptability allowing persistence in face of antibiotic therapies and host defense. These adaptive growth mechanisms include small colony variants, biofilms, and growth under anaerobic conditions. Several reports have described successful eradication of MRSA, yet only two randomized trials of eradication during early infection have been conducted. A list of MRSA specific antibiotics with dosing relevant to CF patients is presented here. Many of these require special dosing in people with CF. Novel antibiotics are in trials for skin and soft tissue infections and it is unclear if and when those might be available for lung infections. Thus the best strategies for MRSA would be primary prevention.

Intestinal carriage of multidrug-resistant bacteria among healthcare professionals in Germany

Healthcare professionals (HCP) might be at increased risk of acquisition of multidrug-resistant bacteria (MDRB), i.e., methillicin-resistant Staphy l oc occus aureus (MRSA), vancomycin-resistant enterococci (VRE), and multidrug-resistant gram-negative bacteria (MDRGN) and could be an unidentified source of MDRB transmission. The aim of this study was to determine the prevalence as well as risk factors of MDRB colonization among HCP. HCP (n=107) taking part in an antibiotic stewardship program, were voluntarily recruited to perform a rectal swab and to fill in a questionnaire to identify risk factors of MDRB carriage, i.e. being physician, gender, travel abroad within the previous 12 months, vegetarianism, regular consumption of raw meat, contact to domestic animals, household members with contact to livestock, work or fellowship abroad, as well as medical treatment abroad and antibiotic therapy within the previous 12 months. Selective solid media were used to determine the colonization rate with MRSA, VRE and MDRGN. MDRGN were further characterized by molecular analysis of underlying β-lactamases. None of the participants had an intestinal colonization with MRSA or VRE. 3.7% of the participants were colonized with extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, predominantly bla _CTX-M type. Neither additional flouroquinolone resistance nor carbapenem resistance was detected in any of these isolates. No risk factors were identified to have a significant impact of MDRB carriage among HCP. A colonization rate of 3.7% with ESBL-producing Enterobacteriaceae is of interest, but comparing it to previously published data with similar colonization rates in the healthy population in the same geographic area, it is probably less an occupational risk.

Prevalence, antimicrobial susceptibility, and molecular characterization of Staphylococcus aureus isolated from dairy herds in northern China

Staphylococcus aureus is one of the main pathogens involved in dairy cow mastitis. Monitoring of antibiotic use would prove useful to assess the risk of Staph. aureus in raw milk. The objective of this work was to investigate the prevalence of Staph. aureus strais isolated from raw milk in northern China, and to characterize antimicrobial susceptibility of these strains and their key virulence genes. In total, 195 raw milk samples were collected from 195 dairy farms located in 4 cities of northern China from May to September 2015. Out of 195 samples, 54 (27.7%) were positive for Staph. aureus. Among these 54 samples, 54 strains of Staph. aureus were isolated, and 16 strains were identified as methicillin-resistant Staph. aureus. The strains exhibited high percentages of resistance to penicillin G (85.2%), ampicillin (79.6%), and erythromycin (46.3%). Moreover, 72% of the strains showed resistance to more than one antimicrobial agent. Overall, 63% of penicillin-resistant strains possessed the blaZ gene, and 60% of the erythromycin-resistant strains possessed erm(A), erm(B), erm(C), msr(A), or msr(B) genes with 8 different gene patterns. All isolates resistant to gentamicin, kanamycin, and oxacillin carried the aac6'-aph2", ant(4')-Ia, and mecA genes, respectively. Two tet(M)-positive isolates carried specific genes of the Tn916-Tn1545 transposon. The most predominant virulence genes were sec, sea, and pvl, which encode staphylococcal enterotoxins (sec and sea) and Panton-Valentine leukocidin, respectively. Thirty-two isolates (59.2%) harbored one or more virulence genes. The majority of Staph. aureus strains were multidrug resistant and carried multiple virulence genes, which may pose a risk to public health. Our data indicated that antimicrobial resistance of Staph. aureus was prevalent in dairy herds in northern China, and that antibiotics, especially penicillin G and ampicillin, to treat mastitis caused by Staph. aureus should be used with caution in northern China.

Genomic surveillance reveals low prevalence of livestock-associated methicillin-resistant Staphylococcus aureus in the East of England

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is an emerging problem in many parts of the world. LA-MRSA has been isolated previously from animals and humans in the United Kingdom (UK), but the prevalence is unknown. The aim of this study was to determine the prevalence and to describe the molecular epidemiology of LA-MRSA isolated in the East of England (broadly Cambridge and the surrounding area). We accessed whole genome sequence data for 2,283 MRSA isolates from 1,465 people identified during a 12-month prospective study between 2012 and 2013 conducted in the East of England, United Kingdom. This laboratory serves four hospitals and 75 general practices. We screened the collection for multilocus sequence types (STs) and for host specific resistance and virulence factors previously associated with LA-MRSA. We identified 13 putative LA-MRSA isolates from 12 individuals, giving an estimated prevalence of 0.82% (95% CI 0.47% to 1.43%). Twelve isolates were mecC-MRSA (ten CC130, one ST425 and one ST1943) and single isolate was ST398. Our data demonstrate a low burden of LA-MRSA in the East of England, but the detection of mecC-MRSA and ST398 indicates the need for vigilance. Genomic surveillance provides a mechanism to detect and track the emergence and spread of MRSA clones of human importance.

Short communication: Characterization of methicillin-resistant Staphylococcus aureus isolated from raw milk fresh cheese in Colombia

The aim of this study was the characterization of a collection of 8 methicillin-resistant Staphylococcus aureus (MRSA) isolates, obtained from samples of fresh cheese (Doble Crema) produced from raw cow milk in small dairies in Colombia. All the isolates harbored the mecA and Panton-Valentine leukocidin (PVL) genes, presented with SCCmec type IV, and belonged to multilocus sequence type 8 and spa type 024. Seven isolates presented 3 closely related pulsed-field gel electrophoresis profiles. Three of them carried the staphylococcal enterotoxin B gene. The isolates were resistant to cefoxitin, oxacillin, penicillin, and ampicillin and susceptible to all non-β-lactams antibiotics tested, with minimum inhibitory concentration values for oxacillin of 4 to 8mg/L. The isolates belonged to the community-acquired MRSA group, suggesting a human source of contamination. The risk of human infection by MRSA via contaminated foods is considered low, but contaminated food commodities can contribute to the worldwide dissemination of clones of community-acquired MRSA.