Predictors of community-associated Staphylococcus aureus, methicillin-resistant and methicillin-susceptible Staphylococcus aureus skin and soft tissue infections in primary-care settings

Diverse Role of blaCTX-M and Porins in Mediating Ertapenem Resistance among Carbapenem-Resistant Enterobacterales

Among carbapenem-resistant Enterobacterales (CRE) are diverse mechanisms, including those that are resistant to meropenem but susceptible to ertapenem, adding further complexity to the clinical landscape. This study investigates the emergence of ertapenem-resistant, meropenem-susceptible (ErMs) Escherichia coli and Klebsiella pneumoniae CRE across five hospitals in San Antonio, Texas, USA, from 2012 to 2018. The majority of the CRE isolates were non-carbapenemase producers (NCP; 54%; 41/76); 56% of all NCP isolates had an ErMs phenotype. Among ErMs strains, E. coli comprised the majority (72%). ErMs strains carrying blaCTX-M had, on average, 9-fold higher copies of blaCTX-M than CP-ErMs strains as well as approximately 4-fold more copies than blaCTX-M-positive but ertapenem- and meropenem-susceptible (EsMs) strains (3.7 vs. 0.9, p < 0.001). Notably, carbapenem hydrolysis was observed to be mediated by strains harboring blaCTX-M with and without a carbapenemase(s). ErMs also carried more mobile genetic elements, particularly IS26 composite transposons, than EsMs (37 vs. 0.2, p < 0.0001). MGE- ISVsa5 was uniquely more abundant in ErMs than either EsMs or ErMr strains, with over 30 more average ISVsa5 counts than both phenotype groups (p < 0.0001). Immunoblot analysis demonstrated the absence of OmpC expression in NCP-ErMs E. coli, with 92% of strains lacking full contig coverage of ompC. Overall, our findings characterize both collaborative and independent efforts between blaCTX-M and OmpC in ErMs strains, indicating the need to reappraise the term "non-carbapenemase (NCP)", particularly for strains highly expressing blaCTX-M. To improve outcomes for CRE-infected patients, future efforts should focus on mechanisms underlying the emerging ErMs subphenotype of CRE strains to develop technologies for its rapid detection and provide targeted therapeutic strategies.

Estimating the Burden of Clinically Significant Staphylococcus aureus Infections and Predictors for Hospitalization for Skin and Soft Tissue Infections, Fulton County, Georgia, 2017

Background

Incidence estimates of Staphylococcus aureus infections rarely include the full spectrum of clinically relevant disease from both community and healthcare settings.

Methods

We conducted a prospective study capturing all S aureus infections in Fulton County, Georgia, during 2017. Medical records of patients with any incident infection (clinical cultures growing S aureus from any site, without prior positive culture in previous 14 days) were reviewed. Estimates of disease incidence were calculated using age-, race-, and sex-specific population denominators accounting for weighted sampling methods. Multivariable logistic regression models were used to identify risk factors for hospitalization among patients with skin and soft tissue infections (SSTIs).

Results

The overall incidence of clinically relevant S aureus infection was 405.7 cases per 100 000 people (standard error [SE], 5.62 [range, 400.1-411.3]). Overall incidence for those of Black race was 500.84 cases per 100 000 people (SE, 14.55), whereas White patients had overall incidence of 363.67 cases per 100 000 people (SE, 13.8). SSTIs were the most common infection (2351; 225.8 cases per 100 000 people [SE, 7.1]), and 30% required hospitalization. Among SSTIs, after adjusting for invasive disease, cellulitis, diabetes, and demographics, independent predictors of hospitalization included methicillin-resistant S aureus (adjusted odds ratio [aOR], 1.6 [95% confidence interval {CI}, 1.0-2.7]) and homelessness (aOR, 4.9 [95% CI, 1.1-22]).

Conclusions

The burden of clinically relevant S aureus infections is high, particularly among the Black population, and risks for hospitalization among SSTIs include isolate factors and factors related to patients' vulnerability.

Etiology, clinical features, management, and outcomes of skin and soft tissue infections in hospitalized children: A 10-year review

PURPOSE

This study aimed to describe the etiology, clinical features, hospital course, and outcomes of hospitalized children with skin and soft tissue infections (SSTIs) and to test if clinical and laboratory variables at admission could differentiate between community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) and community-acquired methicillin-sensitive S. aureus (CA-MSSA).

METHODS

We reviewed the clinical, laboratory, treatment, and outcome data for children hospitalized with SSTIs, aged 0-18 years at MacKay Children's Hospital between 2010 and 2019. Multivariable logistic regression was used to identify independent predictors of CA-MRSA and CA-MSSA SSTIs.

RESULTS

A total of 1631 patients were enrolled. Erysipelas/cellulitis (73.8%) was the most common pediatric SSTI type, followed by acute lymphadenitis (13.6%) and abscess/furuncle/carbuncle (8.6%). Among the 639 culture-positive isolates (purulent SSTIs), 142 (22.2%) were CA-MSSA and 363 (56.8%) were CA-MRSA. The age group 0-1 month (OR, 6.52; 95% CI 1.09-38.92; P = 0.04) and local lymph node reaction (OR, 2.47; 95% CI 1.004-6.08; P = 0.049) were independent factors for differentiating children with CA-MSSA from those with CA-MRSA SSTIs. MRSA isolates in our cohort were highly susceptible to glycopeptides (100%), linezolid (100%), daptomycin (100%), and sulfamethoxazole/trimethoprim (98.6%) but were significantly less susceptible to clindamycin compared with MSSA (34.2% vs. 78.2%, P < 0.001).

CONCLUSION

S. aureus is the leading pathogen of culture-proven SSTIs in hospitalized children with MRSA accounting for more than half. Determining the optimal empirical antibiotics in CA-SSTIs may rely on the patient's age, disease severity, and local epidemiologic data.

Is community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) an emerging pathogen among children in Brazil?

Background

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is spreading worldwide, but little is known about the epidemiology of this pathogen in Brazil.

Objective

To evaluate clinical and microbiological features of children with S. aureus infections admitted to a university hospital.

Methods

This was a cross-sectional study evaluating the potential risk factors for CA-MRSA, and a retrospective cohort evaluating in-hospital clinical outcomes. To include patients with both community and hospital-associated infections, we screened the results of the microbiological laboratory tests from January 1, 2012, to December 31, 2016. According to the phenotype, we classified the isolates in Methicillin-Susceptible S. aureus (MSSA), Hospital-Associated Methicillin-Resistant S. aureus (HA-MRSA), and CA-MRSA. Clinical data were collected from the patients’ medical records.

Results

We identified 279 cases of S. aureus infections (MSSA = 163, CA-MRSA = 69, HA-MRSA = 41). Overall, the incidence density of CA-MRSA and MSSA infections increased while the HA-MRSA incidence density decreased over the study period. CA-MRSA infected patients were more likely to present with skin and soft tissue infections (OR: 2.83, 95%CI: 1.54–5.33, p < 0.001) and osteomyelitis (OR: 4.76; 95%CI: 1.16–22.71, p = 0.014) when compared to MSSA and HA-MRSA infections. Unadjusted case fatality rates were similar between MSSA-infected patients (3.14%, 5/159) and CA-MRSA infected patients (3.80%, 3/79, p = 0.792), while HA-MRSA infected patients were more likely to die in the hospital (12.20%, 5/41, p = 0.013).

Conclusions

CA-MRSA is an emergent pediatric pathogen in Brazil. Our results highlight the relevance of choosing an appropriate initial antimicrobial drug for treating children with severe S. aureus infections.

Emerging multidrug resistance in community-associated Staphylococcus aureus involved in skin and soft tissue infections and nasal colonization

Background

Staphylococcus aureus is a major pathogen causing significant morbidity and mortality worldwide. The emergence of MDR S. aureus strains in the community setting has major implications in disease management. However, data regarding the occurrence and patterns of MDR community-associated S. aureus sub-clones is limited.

Objectives

To use whole-genome sequences to describe the diversity and distribution of resistance mechanisms among community-associated S. aureus isolates.

Methods

S. aureus isolates from skin and soft tissue infections (SSTIs) and nasal colonization were collected from patients within 10 primary care clinics from 2007 to 2015. The Illumina Miseq platform was used to determine the genome sequences for 144 S. aureus isolates. Phylogenetic and bioinformatics analyses were performed using in silico tools. The resistome was assembled and compared with the phenotypically derived antibiogram.

Results

Approximately one-third of S. aureus isolates in the South Texas primary care setting were MDR. A higher proportion of SSTI isolates were MDR in comparison with nasal colonization isolates. Individuals with MDR S. aureus SSTIs were more likely to be African American and obese. Furthermore, S. aureus populations are able to acquire and lose antimicrobial resistance genes. USA300 strains were differentiated by a stable chromosomal mutation in gyrA conferring quinolone resistance. The resistomes were highly predictive of antimicrobial resistance phenotypes.

Conclusions

These findings highlight the high prevalence and epidemiological factors associated with MDR S. aureus strains in the community setting and demonstrate the utility of next-generation sequencing to potentially quicken antimicrobial resistance detection and surveillance for targeted interventions.

Control of healthcare- and community-associated MRSA: recent progress and persisting challenges

BACKGROUND

Healthcare adapted meticillin-resistant Staphylococcus aureus (MRSA) has spread to hospitals around the world over 50 years. More recently, other strains of MRSA have emerged with the ability to spread in the community and infect otherwise healthy individuals. Morbidity and mortality associated with MRSA remains high and its control in both the healthcare and community setting has proven challenging.

SOURCES OF DATA

Pubmed (Medline).

AREAS OF AGREEMENT

The use of targeted screening and decolonization, hand hygiene and antimicrobial stewardship is supported by the most robust studies, though many studies have implemented bundles for effective healthcare-associated (HA)-MRSA control.

AREAS OF CONTENTION

Universal screening, universal decolonization and contact precautions for HA-MRSA control are supported by less evidence. Some interventions may not be cost-effective. Contact precautions may be associated with potential for patient harm. Evidence for effective control community acquired (CA)-MRSA is largely lacking.

GROWING POINTS

Programmes that focus on implementing bundles of interventions aimed at targeting HA-MRSA are more likely to be effective, with an emphasis on hand hygiene as a key component. Control of CA-MRSA is likely to be more difficult to achieve and relies on prevalence, risk factors and community healthcare interactions on a broader scale.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further research in the area of CA-MRSA in particular is required. Antimicrobial stewardship for both CA and HA-MRSA is promising, as is the role of whole genome sequencing in characterizing transmission. However, further work is required to assess their long-term roles in controlling MRSA. With many institutions applying widespread use of chlorhexidine washes, monitoring for chlorhexidine resistance is paramount to sustaining efforts at controlling MRSA.