Comparison of the Staphylococcal Chromosome Cassette (SCC) mec in Methicillin-Resistant Staphylococcus aureus (MRSA) and Non-aureus Staphylococci (MRNAS) from Animals and Humans

Prevalence and types of methicillin-resistant Staphylococcus aureus (MRSA) in meat and meat products from retail outlets and in samples of animal origin collected in farms, slaughterhouses and meat processing facilities. A review

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent cause of nosocomial and community infections, in some cases severe and difficult to treat. In addition, there are strains of MRSA that are specifically associated with food-producing animals. For this reason, in recent years special attention has been paid to the role played by foodstuffs of animal origin in infections by this microorganism. With the aim of gaining knowledge on the prevalence and types of MRSA in meat and meat products, a review was undertaken of work published on this topic since 2001, a total of 259 publications, 185 relating to meat samples from retail outlets and 74 to samples of animal origin collected in farms, slaughterhouses and meat processing facilities. Strains of MRSA were detected in 84.3% reports (156 out of 185) from retail outlets and 86.5% reports (64 out of 74) from farms, slaughterhouses and meat processing facilities, although in most of the research this microorganism was detected in under 20% of samples from retail outlets, and under 10% in those from farms, slaughterhouses and meat processing facilities. The meat and meat products most often contaminated with MRSA were pork and chicken. In addition to the mecA gene, it is crucial to take into consideration the mecB and mecC genes, so as to avoid misidentification of strains as MSSA (methicillin-susceptible Staphylococcus aureus). The great variety of methods used for the determination of MRSA highlights the need to develop a standardized protocol for the study of this microorganism in foods.

Evaluation of Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus respiratory tract superinfections among patients with COVID-19 at a tertiary-care hospital in Tehran, Iran

BACKGROUND

The emergence of healthcare-associated infections (HAIs) or superinfections in COVID-19 patients has resulted in poor prognosis and increased mortality.

METHODS

In a cross-sectional study, 101 respiratory samples were collected from ICU-admitted COVID-19 patients. The HAI rate, demographics, and antibiotic resistance were assessed.

RESULTS

The HAI rate was 83.16% (76.62% bacterial and 6.54% fungal). The prevalence of 3 major HAI-causing organisms included Klebsiella pneumoniae (41.5%), Acinetobacter baumannii (20.8%), and Staphylococcus aureus (4.9%). Mortality and intubation ventilation proportions of 90% (p = 0.027) and 92.2% (p = 0.02) were significant among patients with superinfection, respectively. Multiple logistic regression analysis showed SpO2 pressure (odds ratio 0.842; 95% CI 0.750-0.945; p = 0.004) as a predictive factor in the association between antibiotic usage and mortality. More than 50% of patients received carbapenems. The resistance rates to at least one antibiotic of third-generation cephalosporins, aminoglycosides, quinolones/fluoroquinolones, tetracyclines, and β-lactam inhibitors were 95.2%, 95.2%, 90%, 57.1%, and 100% among A. baumannii isolates and 71.4%, 55%, 69%, 61.9%, and 59.5% among K. pneumoniae isolates, respectively. A proportion of 60% was recorded for methicillin-resistant S. aureus isolates.

CONCLUSION

As a result, antibiotic treatment should be administered following the microbial resistance profile. Contact isolation and infection control measures should be implemented as needed.

Prevalence of Methicillin-ResistantStaphylococcus aureus and Multidrug-Resistant Strains from Patients Attending the Referral Hospitals of Amhara Regional State, Ethiopia

Background

Staphylococcus aureus (S. aureus) causes different types of human infections and can develop resistance to many antibiotics. There is a scarcity of data on the mecA gene and multidrug-resistant (MDR) strain distribution of this organism in developing countries, such as Ethiopia. This study investigated the presence of mecA gene and MDR profile of S. aureus among patients attending referral hospitals of Amhara regional state.

Methods

Of the total of 110 isolates collected from Amhara regional referral hospitals, 70 MDR isolates were further processed for isolation of S. aureus mecA gene. Genomic DNA was isolated using a Sigma-Aldrich genomic DNA isolation kit for Gram-positive bacteria. Amplification of S. aureus mecA gene was performed with the amplicon size of 533 bp. Antimicrobial susceptibility test including methicillin resistance was determined by the Kirby-Bauer disc diffusion method.

Results

The majority of the isolates were recovered from patients aged less than 5 years (51; 36.7%) and the least number of isolates was recorded in age group greater than 60 years (6; 4.3%). Most of the isolates were from blood (61; 43.9%), followed by wounds (45; 32.4%). A high resistance rate was observed in penicillin (81; 73.6%), followed by cotrimoxazole (78; 70.9%), ceftriaxone (76; 69%), erythromycin (66; 60%), and tetracycline (65; 59.1%). Phenotypically, considering cefoxitin as a surrogate marker, 38 (34.5%) of the isolates were methicillin-resistant. The overall MDR isolates were 80 (72.7%). The PCR amplification result of the mecA gene was 14 (20%). Conclusions and Recommendations. High rates of MDR and methicillin-resistantS. aureus were reported. PCR amplification indicated that 20% of MRSA isolates were the mecA gene carriers. Large-scale studies for the detection of MDR strains of S. aureus including MRSA using molecular techniques should be encouraged in the Amhara region.

Respiratory Bacterial and Fungal Superinfections During the Third Surge of the COVID-19 Pandemic in Iran

Objective: We characterized bacterial and fungal superinfection and evaluated the antimicrobial resistance profile against the most common superinfection-causing pathogens (Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus). Methods: In a cross-sectional study, 192 respiratory samples were collected from patients with and without SARS-COV-2 admitted to a teaching hospital in Tehran. Superinfection proportions and the antibiotic resistance profile were assessed and compared with demographic, comorbidities, and other clinical factors. Results: Superinfection rate was 60% among COVID-19 patients (p = 0.629). Intensive care unit admission (p = 0.017), mortality rate (p ≤ 0.001), and antiviral and corticosteroid therapy (p ≤ 0.001) were significantly more common among patients with severe acute respiratory syndrome coronavirus 2 (SARS-COV-2). The most common superinfections were caused by K. pneumoniae (42.7%, 82/192), A. baumannii (14.6%, 28/192), and S. aureus (13%, 25/192). A. baumannii isolates exhibited greater antibiotic resistance. Forty-four percent (11/25) of S. aureus isolates were cefoxitin resistant and also confirmed as methicillin-resistant S. aureus by PCR. Conclusion: The rise of difficult-to-treat infections with a high burden of antibiotic resistance, coupled with an increase in mortality rate of SARS-COV-2 superinfected individuals, illustrates the impact of the COVID-19 pandemic on antimicrobial resistance. Post-pandemic antimicrobial resistance crisis management requires precise microbiological diagnosis, drug susceptibility testing, and prescription of antimicrobials appropriate for the patient's condition.

Identification of staphylococcal cassette chromosome mec in Staphylococcus aureus and non-aureus staphylococci from dairy cattle in Belgium: Comparison of multiplex PCR and whole genome sequencing

The present study compared multiplex PCR (mPCR) and Whole Genome Sequencing (WGS) using the SCCmecFinder database to identify the Staphylococcal Cassette Chromosome (SCC) mec in five Staphylococcus aureus (SA) and nine non-aureus staphylococci (NAS) isolated from dairy cattle. mPCR identified an SCCmecIV in four SA and one NAS, but could not differentiate between SCCmecII and IV in the fifth SA, that all harbored the mecA gene and were phenotypically resistant to cefoxitin. SCCmecFinder confirmed the presence of an SCCmecIVc(2B) in four SA and of the SCCmecIVa(2B) in the fifth SA and the one NAS. Both methods also detected one untypeable SCCmec in another cefoxitin-resistant NAS harboring the mecA gene and a pseudo SCCmec in one cefoxitin-sensitive NAS harboring one mecC-related gene. No SCCmec elements were identified either in one cefoxitin-sensitive NAS harboring the mecA2 gene, or in five NAS (one resistant and four sensitive to cefoxitin) harboring the mecA1 gene. SCCmecFinder could even not identify the presence of any mecA1 gene in these five NAS, whose presence was nevertheless confirmed by ResFinder. The conclusions of this study are: (i) mPCR and WGS sequencing using SCCmecFinder are complementary methodologies to identify SCCmec; (ii) SCCmecFinder and ResFinder to a lesser extent cannot identify all mec gene allotypes; (iii) a specific classification of the SCCmec in NAS would be epidemiologically helpful; (iv) presence of a mecA gene and a complete SCCmec is linked to cefoxitin resistance, whereas presence of other mec genes and of pseudo or no SCCmec is not.

Comparative Study of the Difference in Behavior of the Accessory Gene Regulator (Agr) in USA300 and USA400 Community-Associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA)

Community-associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA) is notorious as a leading cause of soft tissue infections. Despite several studies on the Agr regulator, the mechanisms of action of Agr on the virulence factors in different strains are still unknown. To reveal the role of Agr in different CA-MRSA, we investigated the LACΔagr mutant and the MW2Δagr mutant by comparing LAC (USA300), MW2 (USA400), and Δagr mutants. The changes of Δagr mutants in sensitivity to oxacillin and several virulence factors such as biofilm formation, pigmentation, motility, and membrane properties were monitored. LACΔagr and MW2Δagr mutants showed different oxacillin sensitivity and biofilm formation compared to the LAC and MW2 strains. Regardless of the strain, the motility was reduced in Δagr mutants. And there was an increase in the long chain fatty acid in phospholipid fatty acid composition of Δagr mutants. Other properties such as biofilm formation, pigmentation, motility, and membrane properties were different in both Δagr mutants. The Agr regulator may have a common role like the control of motility and straindependent roles such as antibiotic resistance, biofilm formation, change of membrane, and pigment production. It does not seem easy to control all MRSA by targeting the Agr regulator only as it showed strain-dependent behaviors.