Epidemiologic and Molecular Characteristics of Staphylococcus aureus Strains Isolated From Hospitalized Pediatric Patients

Investigation of SCCmec Types using the Real Time PCR Method in Cefoxitin-Resistant Staphylococcus aureus Isolates

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen that can cause many community and hospital-acquired infections. This study was conducted to investigate the SCCmec gene types responsible for methicillin resistance in MRSA isolates isolated from hospitalised patients.

MATERIAL AND METHODS

MRSA isolates isolated from samples sent from various clinics to Gaziantep University Hospital Microbiology Laboratory between March 2021-January 2022 were included in the study. Bacteria were identified using by VITEK 2 automated system. Cefoxitin (FOX) resistance was determined by the disc diffusion method according to EUCAST standards. Cefoxitin resistance was confirmed by the Penicillin Binding Protein 2' latex agglutination test. Types of mecA, mecC, coa, nuc, Panton Valentin Leukocidin (PVL), ccrC2, class A mec, SCCmec types in isolates detected as MRSA were investigated by real-time PCR.

RESULTS

In this study, 116 isolates meeting the study criteria were examined. By detecting the nuc and coa genes in all isolates by PCR, the phenotypic identification of S.aureus was confirmed. While the mecA gene was detected in all MRSA isolates, no mecC gene was detected in any isolates. Detected SCCmec types were as follows; SCCmec Type 1 (2.6%), Type II (28.4%), Type III (12.9%), Type IVa (11.2%), Type IVb (3.4%), Type IVc (3.4%), Type IVg (12.1%), Type V (0.9%), Type VII (4.3%), Type VIII (18.1%), Type IX (0.9%), Type XII (1.7%). On the other hand, SCCmec Type VI, X, XI and XIII were not found in any isolate. It was determined that four of the MRSA isolates (3.4%) carried the PVL gene that two (50%) of these were found in SCCmec Type VIII.

CONCLUSION

Monitoring of FOX resistance is an effective and safe method for determination of MRSA isolates. The change in the mec gene causes resistance, which should be monitored regularly with molecular methods. Our study is the first study in Turkey.

Prevalence and antimicrobial susceptibility pattern of methicillin-resistant Staphylococcus aureus (MRSA) at a maternity and children hospital in Saudi Arabia: A cross-sectional study

Background

Methicillin-resistant Staphylococcus aureus (MRSA) pathogens are considered a serious global health threat, leading to increased mortality and antimicrobial resistance. Rates in Saudi Arabia remain high, necessitating continuous surveillance. This study investigates MRSA prevalence and susceptibility at a Saudi maternity and children's hospital.

Method

A cross-sectional study was conducted on pediatric (<18 years) and maternal patients with S. aureus infection from Jan. 2020 to March. 2022. Bacterial strains were obtained from patient's clinical specimens and was identified by standard method. The BD Phoenix™ M50 was used for antibiotic susceptibility tests and MRSA detection. Data were analysed using descriptive and inferential statistics (Chi-square test) with SPSS software.

Results

Out of 152 S. aureus cases, 114/152 (75 %) were pediatric and 38/152 (25 %) were maternal patients. The overall MRSA infection was 69/152 (45.4 %). Among pediatrics, 31/54 (57.4 %) MRSA cases were female; over 30/54 (56 %) were under 1 year old; and most MRSA infections were obtained from skin 29/54 (53.7 %) compared to other sites of infections (p = 0.024). Among maternal cases, 15/38 (39.5 %) were MRSA, primarily from wound infections 14/15 (93.3 %) compared to other sites of infections (p = 0.39). All MRSA isolates were sensitive to vancomycin and linezolid. While 51/60(85 %) were sensitive to Trimethoprim/ sulfamethoxazole.

Conclusion

This investigation found a high prevalence of MRSA among pediatrics and maternal inpatients, indicating a significant burden. All MRSA isolates were susceptible to vancomycin but demonstrated variable sensitivity to other antibiotics. These findings highlight the need for ongoing surveillance, infection control strategies, and research into alternative treatment options to combat this major public health threat.

Different evolution of S. aureus methicillin-resistant and methicillin-susceptible infections, Argentina

Staphylococcus aureus-(SA) is widespread among healthcare-associated-(HA) and the community-associated-(CA) infections. However, the contributions of MRSA and MSSA to the SA overall burden remain unclear. In a nationally-representative-survey conducted in Argentina, 668 SA clinical isolates from 61 hospitals were examined in a prospective, cross-sectional, multicenter study in April 2015. The study aimed to analyze MRSA molecular epidemiology, estimate overall SA infection incidence (MSSA, MRSA, and genotypes) in community-onset (CO: HACO, Healthcare-Associated-CO and CACO, Community-Associated-CO) and healthcare-onset (HO: HAHO, Healthcare-associated-HO) infections, stratified by age groups. Additionally temporal evolution was estimated by comparing this study's (2015) incidence values with a previous study (2009) in the same region. Erythromycin-resistant-MSSA and all MRSA strains were genetically typed. The SA total-infections (TI) overall-incidence was 49.1/100,000 monthly-visits, 25.1 and 24.0 for MRSA and MSSA respectively (P = 0.5889), in April 2015. In adults with invasive-infections (INVI), MSSA was 15.7 and MRSA was 11.8 (P = 0.0288), 1.3-fold higher. HA SA infections, both MSSA and MRSA, surpassed CA infections by over threefold. During 2009-2015, there was a significant 23.4 % increase in the SA infections overall-incidence, mainly driven by MSSA, notably a 54.2 % increase in INVI among adults, while MRSA infection rates remained stable. The MSSA rise was accompanied by increased antimicrobial resistance, particularly to erythromycin, linked to MSSA-CC398-t1451-ermT + -IEC+-pvl- emergence. The SA-infections rise was primarily attributed to community-onset-infections (37.3 % and 62.4 % increase for TI and INVI, respectively), particularly HACO-MSSA and HACO-MRSA in adults, as well as CACO-MSSA. The main CA-MRSA-PFGE-typeN-ST30-SCCmecIVc-PVL+/- clone along with other clones (USA300-ST8-IV-LV-PVL+/-, PFGE-typeDD-ST97-IV- PVL-) added to rather than replaced CA-MRSA-PFGE-typeI-ST5-SCCmecIVa-PVL+/- clone in HA invasive-infections. They also displaced clone HA-MRSA-PFGE-typeA-ST5-SCCmecI, mainly in HAHO infections. The overall-burden of SA infections is rising in Argentina, driven primarily by community-onset MSSA, particularly in adults, linked to increased erythromycin-resistance and MSSA-CC398-t1451-ermT + -IEC+-pvl- emergence. Novel knowledge and transmission-control strategies are required for MSSA.

Retrospective Study on Staphylococcus aureus Resistance Profile and Antibiotic Use in a Pediatric Population

The growing phenomenon of antibiotic resistance and the presence of limited data concerning the pediatric area prompted us to focus on Staphylococcus aureus infection in this study, its antibiotic resistance profile, and the therapeutic management of affected children. We conducted a retrospective study by collecting clinical data on infants and children with antibiogram-associated S. aureus infection. We enrolled 1210 patients with a mean age of 0.9 years. We analyzed the resistance patterns and found 61.5% resistance to oxacillin, 58.4% resistance to cephalosporins, 41.6% resistance to aminoglycosides, and 38.3% resistance to fluoroquinolones. Importantly, we found no resistance to glycopeptides, a key antibiotic for MRSA infections whose resistance is increasing worldwide. We also found that the main risk factors associated with antibiotic resistance are being aged between 0 and 28 days, the presence of devices, and comorbidities. Antibiotic resistance is a growing concern; knowing the resistance profiles makes it possible to better target the therapy; however, it is important to use antibiotics according to the principles of antibiotic stewardship to limit their spread.

Activity of Tedizolid and Comparator Agents Against Gram-positive Isolates Causing Skin and Skin Structure Infections in Pediatric Patients in United States Hospitals (2015-2019)

BACKGROUND

Tedizolid was approved by the United States Food and Drug Administration to treat acute bacterial skin and skin structure infections in adults in 2014, and in 2020, United States Food and Drug Administration expanded the approval of tedizolid to treat pediatric patients 12 years of age and older. This study assessed the activity of tedizolid and comparator agents against clinical surveillance isolates collected from pediatric patients with skin and skin structure infection in the United States.

METHODS

A total of 2747 gram-positive organisms (1 per patient) were collected in 2015 to 2019 from pediatric (≤17 years old) patients with skin and skin structure infections. The isolates were collected from 33 US medical centers and susceptibility tested against tedizolid and comparators by reference broth microdilution methods. Susceptibility results for main pathogens were stratified by patient age: ≤1 years old (851 isolates), 2 to 5 years old (623), 6 to 12 years old (754) and 13 to 17 years old (519).

RESULTS

Staphylococcus aureus (n = 2163) was the main pathogen recovered from all age groups, followed by β-hemolytic streptococci (n = 460). Tedizolid inhibited all S. aureus , including methicillin-resistant S. aureus (MRSA) isolates (41.0%), regardless of the age group. MRSA rates varied by age group; MRSA was highest among ≤1 years old (45.0%) and lowest in the 13 to 17 years old (32.7%) groups. Linezolid, daptomycin and vancomycin also displayed susceptibility rates of 100% against S. aureus isolates. Clindamycin (81.3%-98.5%), tetracycline (91.6%-97.1%) and trimethoprim-sulfamethoxazole (97.0%-100%) susceptibility rates varied among age groups and methicillin resistance profiles. Overall, tedizolid, linezolid, daptomycin and vancomycin inhibited all gram-positive pathogens in this collection.

CONCLUSIONS

Tedizolid was very active against a large collection of gram-positive pathogens causing skin and skin structure infection in pediatric patients, including MRSA isolates.

Epidemiology and antimicrobial susceptibility of Staphylococcus aureus in children in a tertiary care pediatric hospital in Milan, Italy, 2017-2021

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent worldwide and can cause severe diseases. MRSA is associated with other antibiotic resistance. COVID-19 pandemic increased antimicrobial resistance in adult patients. Only a few data report the antimicrobial susceptibility of S. aureus in the Italian pediatric population, before and during the COVID-19 pandemic.

Methods

We included all the S. aureus positive samples with an available antibiogram isolated from pediatric patients (< 18 years old) in a tertiary care hospital in Milan, Italy, from January 2017 to December 2021. We collected data on demographics, antimicrobial susceptibility, and clinical history. We compared methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA strains. We calculated the frequency of isolation by year. The incidence of isolates during 2020 was compared with the average year isolation frequency using the univariate Poisson test. We compared the proportion of MRSA isolates during 2020 to the average proportion of other years with the Chi-squared test.

Results

Our dataset included a total of 255 S. aureus isolated from 226 patients, 120 (53%) males, and 106 (47%) females, with a median age of 3.4 years (IQR 0.8 – 10.5). The mean isolation frequency per year was 51. We observed a significant decrease of isolations during 2020 (p = 0.02), but after adjusting for the total number of hospitalization per year there was no evidence that the incidence changed. Seventy-six (30%) S. aureus were MRSA. Twenty (26%) MRSA vs 23 (13%) MSSA (p = 0.02) were hospital-acquired. MRSA strains showed higher resistance to cotrimoxazole, clindamycin, macrolides, levofloxacin, gentamicin, and tetracyclin than MSSA strains. None of MRSA were resistant to linezolid and vancomycin, one was resistant to daptomycin. The proportion of MRSA did not change during the COVID-19 pandemic. The overall clindamycin resistance was high (17%). Recent antibiotic therapy was related to MRSA infection.

Conclusion

The proportion of MRSA did not change during the COVID-19 pandemic and remained high. Clindamycin should not be used as an empirical MRSA treatment due to its high resistance.

Molecular characteristics of Staphylococcus aureus strains isolated from nasal samples of sixth year medical students during their pediatric services practices

Background

Methicillin-resistant Staphylococcus aureus (MRSA) strains are prevalent in healthcare services. Medical students are at risk for MRSA carriage, subsequent infection and potential transmission of nosocomial infection.Few studies have examined MRSA carriage among medical students.

Methods

In this prospective cohort study, between July 2016 and June 2017, two nasal swab samples were taken per student 4 weeks apart during their pediatric internship. MRSA typing was performed by staphylococcal cassette chromosome mec (SCCmec) types, Panton Valentine leukocidin (PVL) encoding genes.

Results

A total of 239 sixth year medical students, 164 (68.6%) male (M/F:2.1),with median age 25 years (min–max; 23–65 years) were included in this prospective cohort study. Among 239 students, 17 students (7.1%) were found to be colonized with methicillin-sensitive S. aureus (MSSA) at the beginning of pediatric internship. After 4 weeks, at the end of pediatric internship totally 52 students were found to be S. aureus colonized (21.8%). Three of 52 S. aureus isolates were MRSA (1.3%) and the rest was MSSA (20.5%), all were PVL gen negative. Two of three MRSA isolates were characterized as SCCmec type IV, one isolate was untypeable SCCmec. Nasal carriage of S. aureus increased from 7.1% to 21.5% (p < 0.001). Nasal S. aures colonization ratio was higher in students working in pediatric infectious disease service (p = 0.046). Smoking was found to be associated with a 2.37-fold [95% CI (1.12–5.00); p = 0.023] and number of patients in pediatric services was 2.66-fold [95% CI (1.13–6.27); p = 0.024] increase the risk of nasal S. aureus colonization. Gender was not found to increase risk of MRSA carriage.

Conclusion

MSSA nasal carriage increased at the end of pediatric internship and significantly high in students working in pediatric infectious diseases services. Smoking and high number of patients in pediatric services significantly increase S.aureus colonization.