Epidemiology of Staphylococcus aureus in neonates on admission to a Chinese neonatal intensive care unit

Molecular Epidemiology Clinical Manifestations, Decolonization Strategies, and Treatment Options of Methicillin-Resistant Staphylococcus aureus Infection in Neonates

Preterm and low-birth-weight neonates are particularly susceptible to methicillin-resistant Staphylococcus aureus (MRSA) colonization, whereas MRSA infection is associated with significant neonatal morbidity and mortality globally. The objective of our study was to examine the current body of knowledge about molecular traits, epidemiology, risk factors, clinical presentation, decolonization techniques, and available treatments for MRSA infection in neonates. MRSA strains that predominate in neonatal units, namely healthcare-associated (HA)-MRSA, differ from community-acquired (CA)-MRSA strains in molecular characteristics, toxin synthesis, including Panton-Valentine leukocidin, and resistance to antibiotics. Colonization with MRSA predisposes neonates to infection. The clinical impact of MRSA infection includes bacteremia, sepsis, pneumonia, endocarditis, osteomyelitis, septic arthritis, skin and soft tissue infections, and toxic shock syndrome. To reduce MRSA transmission, colonization, and infection, customized approaches are required, including continuous surveillance of MRSA epidemiology, new techniques for detecting MRSA resistance, and the application of basic preventive measures. Antimicrobial susceptibility monitoring is essential to identify the best empirical antimicrobial treatments. The growing antibiotic resistance of MRSA remains challenging, and vancomycin is still the best option. Further extensive research and surveillance are warranted to explore the genetic diversity and prevalence of MRSA.

Prevalence and pathogen profiles of bacteremia in neonates hospitalized for clinical Sepsis in Ethiopia: a systematic review and meta-analysis

BACKGROUND

Bacteremia is prevalent in neonates, largely attributed to factors inherent in the neonatal period. However, the prevalence of proven bacteremia in Ethiopian neonates has not been previously synthesized. Accordingly, this systematic review and meta-analysis aimed to analyze the prevalence of bacteremia and pathogen profiles in neonates hospitalized for clinical sepsis in Ethiopia.

METHODS

This systematic review and meta-analysis followed the preferred reporting items for systematic review and meta-analysis (PRISMA) 2020. The literature search was conducted across five databases including PubMed, Google Scholar, Web of Science, Science Direct, and Research for Life spanning from January 2015 to July 2023. The search strategy used MeSH terms and involved screening titles and abstracts, reviewing full-text articles, and including only observational studies published in English within the specified timeframe. Data extraction and quality assessment were performed by three experienced reviewers using a validated data collection tool and the Joanna Briggs Institute quality assessment tool, respectively. The prevalence of neonatal bacteremia was determined through a random effects model, with heterogeneity among studies assessed using the Q statistic and the I2 statistic. Publication bias was evaluated using a funnel plot and Egger's regression test, and STATA version 16.0 was used for all analysis at 95% confidence level.

RESULTS

A meta-analysis of nine studies revealed a bacteremia prevalence of 40.0% (95% CI: 34.0-46.0%). Subgroup analysis indicated variations in prevalence based on regions and study designs, with Oromia at 44.0% (95% CI: 28.0, 61.0%) and Amhara at 39.0% (95% CI: 27.0, 51.0%). Longitudinal studies exhibited a higher prevalence (47.0%, 95% CI: 27.0-68.0%) compared to cross-sectional designs (38.0%, 95% CI: 32.0-44.0%). Gram-negative bacteria were identified as the predominant etiological agents, representing 59.5% (95% CI: 56.8-62.3%) of cases. Among the bacterial species, Staphylococcus aureus emerged as the most prevalent (20.0%, 95% CI: 18.0%, 22.0%), followed by coagulase-negative staphylococci and Klebsiella pneumoniae, each contributing to 17.0% (95% CI: 15.0%, 20.0%) of bacteremia cases.

CONCLUSION

The study revealed a significant high prevalence of bacteremia, with differences noted across regions and study designs. Key pathogens identified were Staphylococcus aureus, Klebsiella pneumoniae and coagulase-negative staphylococci. It is advisable to implement surveillance systems, targeted prevention strategies, diagnostic stewardship, and further research on regional variations and bacterial profiles to effectively enhance the ominous future.

Neonatal Colonization With Antibiotic-Resistant Pathogens in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis

Importance

In low- and middle-income countries (LMICs), neonatal bacterial infections are mainly caused by Enterobacterales species and Staphylococcus aureus, which are also the leading causes of mortality directly attributable to antimicrobial resistance. As bacterial colonization often precedes infection, better knowledge of colonization is crucial to prevent antibiotic-resistant neonatal sepsis.

Objective

To synthesize current evidence on the prevalence of and factors associated with colonization with third-generation cephalosporin-resistant Enterobacterales (3GCRE), carbapenem-resistant Enterobacterales (CRE), and methicillin-resistant S aureus (MRSA) during the first 3 months of life in LMICs.

Data Sources

PubMed, Scopus, Web of Science, and the World Health Organization Global Index Medicus were searched for articles published from January 1, 2000, through July 29, 2024.

Study Selection

Included studies were conducted in LMICs and reported prevalence rates or factors associated with colonization with 3GCRE, CRE, or MRSA in neonates and infants up to 3 months of age. Outbreak reports were excluded.

Data Extraction and Synthesis

Data extraction and risk-of-bias assessment using a Joanna Briggs Institute tool were performed by 2 independent reviewers. Pooled prevalence for each pathogen was computed using a random-effects model. Reporting followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline.

Main Outcomes and Measures

Prevalence of and factors associated with 3GCRE, CRE, and MRSA colonization.

Results

Of the 3147 articles identified in the search, 67 studies (51 for 3GCRE and CRE and 16 for MRSA) including 17 152 individuals were eligible. The pooled prevalence of 3GCRE colonization was 30.2% (95% CI, 21.4%-40.7%; τ2 = 1.48; I2 = 95.1%), varying from 18.2% (95% CI, 10.8%-29.1%) in nonhospitalized individuals to 48.2% (95% CI, 36.4%-60.2%) in hospitalized individuals. The prevalence of CRE colonization was 2.6% (95% CI, 0.7%-8.8%; τ2 = 7.79; I2 = 95.6%), while it was 2.7% (95% CI, 1.0%-6.7%; τ2 = 2.58; I2 = 93.5%) for MRSA. Increased risk of colonization with 3GCRE was associated with hospital birth (odds ratio [OR], 1.87; 95% CI, 1.33-2.64), neonatal antibiotic use (OR, 2.96; 95% CI, 1.43-6.11), and prolonged rupture of membranes (OR, 3.86; 95% CI, 2.19-6.84).

Conclusions and Relevance

In this systematic review and meta-analysis of antibiotic-resistant pathogen carriage in individuals aged 0 to 3 months, the pooled prevalence was substantial despite a limited exposure period. Although high heterogeneity between studies limited extrapolation of results, the findings highlight the need for further investigation to identify transmission routes and to design targeted and effective preventive measures.

Epidemiology of Methicillin-resistant Staphylococcus aureus Colonization in Neonates within Neonatal Intensive Care Units: A Systematic Review and Meta-analysis

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) colonization in neonatal intensive care units (NICUs) is a significant global health concern, leading to severe infections, extended hospital stays, and substantial economic burdens on health-care systems. To develop effective infection control strategies, we need to fill existing gaps in our understanding of MRSA epidemiology in neonates. The aim of this systematic review is to provide an extensive analysis of the proportion of MRSA colonizations in NICUs.

Methods

We used a comprehensive search strategy across databases such as Medline, Embase, Global Health, Web of Science, and Global Index Medicus, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Articles were independently reviewed and selected based on a variety of criteria, including the inclusion of neonates tested for MRSA colonization during NICU stay, and the reporting of community-acquired and hospital-acquired MRSA (CA-MRSA and HA-MRSA) incidence levels. Exclusion criteria included studies outside NICUs, those focused on specific MRSA outbreaks or clinical infections, review studies, and those lacking abstracts or full texts. Five authors independently extracted data, which was summarized and checked for quality. Statistical analysis included a random-effects model to compute pooled proportions, stratification by geographical location, evaluation of heterogeneity, and examination of publication bias.

Results

Our systematic review evaluated 62 studies out of an initial 536 records identified. The majority of the selected studies were conducted in high-income countries, primarily in the United States. From these studies, we estimated a cumulative incidence rate of 7.2% for MRSA colonization in NICUs. When the source of MRSA was considered, CA-MRSA incidence was 2.7%, while HA-MRSA incidence was notably higher at 11%. A subgroup analysis showed geographical differences in the cumulative incidence of MRSA colonization in NICUs, with Brazil having the lowest incidence and Taiwan the highest. The proportion of HA-MRSA colonization also varied significantly by country, with South Korea reporting higher incidence rates than the United States. However, the differences in CA-MRSA colonization rates between countries and WHO regions were not statistically significant.

Conclusions

Our systematic review found a cumulative incidence of 7.2% for MRSA colonization in NICUs, with HA-MRSA (11%) being more prevalent than CA-MRSA (2.7%). Regional variations were detected, with Taiwan exhibiting the highest cumulative incidence and South Korea having both the highest CA-MRSA and HA-MRSA. These findings underline the substantial public health impact of MRSA, especially in NICUs, necessitating context-specific prevention and control strategies. Future research should strive to address these regional disparities and aspire to attain a more globally representative understanding of MRSA colonization rates.

Phenotypic bacterial epidemiology and antimicrobial resistance profiles in neonatal sepsis at Jimma medical center, Ethiopia: Insights from prospective study

BACKGROUND

Epidemiological profiles and the rundown crisis of antimicrobial resistance from bacterial isolates in neonatal sepsis compel regular surveillance to enhance data-driven decision-making. Accordingly, this study aimed to assess the phenotypic epidemiology and antimicrobial resistance profiles of bacteria isolated from clinically suspected neonatal sepsis in Ethiopia.

METHODS

A total of 342 neonates suspected of clinical sepsis were randomly included in a prospective observational study conducted at the neonatal intensive care unit (NICU) of Jimma medical center (JMC) from May 2022 to July 2023. Blood samples were collected from each neonate and subjected to a culture test for identification of bacterial isolates and their antibiotic resistance profiles following the standardized guidelines. The laboratory results, along with relevant clinical data, were recorded using WHONET and analyzed using STATA software.

RESULTS

Out of the 342 blood samples that were analyzed, 138 samples (40.4%, 95% CI: 35.1-45.6, P<0.01) exhibited proven bacterial infection. The infection rates were notably higher in males with 85/138 (61.6%, 95% CI: 53.4-69.8, P<0.01) and neonates aged 0-3 days with 81/138 (58.7%, 95% CI: 50.5-66.9, P<0.01). The majority of the infections were attributed to Gram-negative bacteria, accounting for 101/138(73.2%, 95% CI: 65.6-80.7) cases, with 69/101(68.3%, 95% CI: 63.8-72.8) cases involving ESBL-producing strains, while Gram-positive bacteria were responsible for 26.8% (95% CI: 19.3-34.4) of the infections. The predominant isolates included Klebsiella pneumoniae (37.7%, 95% CI: 29.6-45.8), Coagulase-negative Staphylococci (CoNs) (20.3%, 95% CI: 13.6-27.0), and Acinetobacter species (11.6%, 95% CI: 6.0-17.1). Of the total cases, 43/72 (59.7%, 95% CI: 48.4-71.1, P<0.01) resulted in mortality, with 28/72 (38.9%, 95% CI: 27.70-50.1, P<0.03) deaths linked to Extended-Spectrum Beta-Lactamase (ESBL)-producing strains. Klebsiella pneumoniae displayed high resistance rates to trimethoprim-sulfamethoxazole (100%), ceftriaxone (100%), cefotaxime (98.1%), ceftazidime (90.4%), and gentamicin (84.6%). Acinetobacter species showed resistance to ampicillin (100%), cefotaxime (100%), trimethoprim-sulfamethoxazole (75%), ceftazidime (68.8%), chloramphenicol (68.8%), and ceftriaxone (68.8%). Likewise, CoNs displayed resistance to ampicillin (100%), penicillin (100%), cefotaxime (86.0%), gentamicin (57.2%), and oxacillin (32.2%). Multidrug resistance was observed in 88.4% (95% CI: 81.8-93.0) of isolates, with ESBL-producers significantly contributing (49.3%, 95% CI: 45.1-53.5). Furthermore, 23.0% (95% CI: 15.8-31.6) exhibited a prevalent resistance pattern to seven distinct antibiotic classes.

CONCLUSION

The prevalence and mortality rates of neonatal sepsis were significantly high at JMC, with a notable surge in antibiotic and multidrug resistance among bacterial strains isolated from infected neonates, specifically ESBL-producers. These resistant strains have a significant impact on infection rates and resistance profiles, highlighting the requisite for enhanced diagnostic and antimicrobial stewardship, stringent infection control, and further molecular characterization of isolates to enhance neonatal survival.

Surveillance on meticillin-sensitive Staphylococcus aureus colonization and infection in a neonatal intensive care unit

BACKGROUND

Meticillin-sensitive Staphylococcus aureus (MSSA) infection is a significant health concern in neonatal intensive care units (NICUs). Bacterial colonization increases the risk of subsequent infection, leading to morbidity and mortality.

AIM

To report the findings of a retrospective cohort study on the surveillance of MSSA colonization and infection in NICU patients.

METHODS

The weekly microbial surveillance results for MSSA colonization in the throat, nose, anus, and groin, as well as invasive and non-invasive MSSA infections, were analysed from November 2020 to June 2022. The MSSA infection and colonization risk were compared after adjustment for confounders by stepwise logistic regression analysis.

FINDINGS

Three hundred and eighty-three neonates were screened; 42.8% (N=164) were MSSA colonized. Significant risk factors for MSSA colonization were length of stay, vaginal delivery and extreme low gestational age <28 weeks (ELGAN) (all P<0.05). The surveillance detected 38 (9.9%) mild MSSA infections and 11 (2.9%) invasive MSSA infections. Neonatal colonization with MSSA is a major risk factor for MSSA infection overall (29.3% in colonized/infected vs 70.7% colonized/not-infected and 0.5% in not-colonized/infected vs 99.5% in not-colonized/not-infected infants) and invasive MSSA infections (6.1% in colonized/infected vs 93.9% in colonized/not-infected and 0.5% in non-colonized/infected vs 99.5% not-colonized/not-infected infants). Also, extreme low birth weight (<1000 g), ELGAN and invasive ventilation were significant risk factors for MSSA infections (all, P<0.05).

CONCLUSIONS

The link between postnatal MSSA colonization and subsequent MSSA infection offers possibilities for prevention. Additional research is needed to explore the association between vaginal birth and the pathogenesis of neonatal MSSA colonization.

ST7 Becomes One of the Most Common Staphylococcus aureus Clones After the COVID-19 Epidemic in the City of Wuhan, China

BACKGROUND

Staphylococcus aureus (S. aureus) was able to rapidly evolve and adapt under the pressure of antibiotics, host immune and environmental change. After Corona Virus Disease 2019 (COVID-19) epidemic in Wuhan, China, a large number of disinfectants were used, which might result in rapid evolution of S. aureus.

METHODS

A total of 619 S. aureus isolates were collected from Zhongnan Hospital, Wuhan University from 2018 to 2021, including group BEFORE (309 strains collected before COVID-19 pandemic) and group AFTER (310 strains collected after COVID-19 pandemic), for comparing the changes of molecular epidemiology. The molecular characteristics of isolates were analyzed by Multi-locus sequence typing (MLST), spa, chromosomal cassette mec (SCCmec) typing, virulence genes were screened by the PCR, antibiotic susceptibility test was carried out by the VITEK system.

RESULTS

Thirty-six sequence types (STs) belonging to 14 clone complexes (CCs) were identified. ST5 was the most prevalent clone in both groups, and ST7, ranking the sixth in group BEFORE, became the second dominant clone in group AFTER (6.5% vs 10.0%), whereas ST239 decreased from the seventh to the fourteenth (5.8% vs 1.9%). ST7 in group AFTER had a higher positive rate of virulence genes, including hlb, fnbB, seb, lukDE, sdrE and the proportion of ST7-t091 MRSA strains increased from 19.1% to 50% compared with group BEFORE. Though no significant difference of MRSA proportion was found between two groups, SCCmec type-III in group AFTER decreased (p<0.01). Though the rate of multidrug-resistance (MDR) decreased, the virulence genes hlb, hlg, fnbB, seb and pvl carrying rates were significantly elevated in MRSA strains of group AFTER.

CONCLUSION

After COVID-19 pandemic, ST7 becomes one of the predominant S. aureus clones in Wuhan and the carrying rate of SCCmec and virulence genes is on the rise. Therefore, it is essential to strengthen the surveillance of ST7 S. aureus clone.

Current molecular approach for diagnosis of MRSA: a meta-narrative review

Introduction:

Detection and diagnosis of methicillin-resistant Staphylococcus aureus (MRSA) are important in ensuring a correct and effective treatment, further reducing its spread. A wide range of molecular approaches has been used for the diagnosis of antimicrobial resistance (AMR) in MRSA. This review aims to study and appraise widely used molecular diagnostic methods for detecting MRSA.

Methods:

This meta-narrative review was performed by searching PubMed using the following search terms: (molecular diagnosis) AND (antimicrobial resistance) AND (methicillin-resistant Staphylococcus aureus). Studies using molecular diagnostic techniques for the detection of MRSA were included, while non-English language, duplicates and non-article studies were excluded. After reviewing the libraries and a further manual search, 20 studies were included in this article. RAMESES publication standard for narrative reviews was used for this synthesis.

Results:

A total of 20 full papers were reviewed and appraised in this synthesis, consisting of PCR technique (n = 7), deoxyribonucleic acid (DNA) Microarray (n = 1), DNA sequencing (n = 2), Xpert MRSA/SA BC assay (n = 2), matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) (n = 2), MLST (n = 4), SCCmec typing (n = 1) and GENECUBE (n = 1).

Discussion:

Different diagnostic methods used to diagnose MRSA have been studied in this review. This study concludes that PCR has been extensively used due to its higher sensitivity and cost-effectiveness in the past five years

Genomic and Epidemiological Features of Two Dominant Methicillin-Susceptible Staphylococcus aureus Clones from a Neonatal Intensive Care Unit Surveillance Effort

Methicillin-susceptible Staphylococcus aureus (MSSA) is a more prevalent neonatal intensive care unit (NICU) pathogen than methicillin-resistant S. aureus (MRSA). However, the introduction and spread of MSSA, the role of systematic decolonization, and optimal infection prevention and control strategies remain incompletely understood. We previously screened infants hospitalized in a university-affiliated level III to IV NICU twice monthly over 18 months for S. aureus colonization and identified several prevalent staphylococcal protein A (spa) types. Here, we performed whole-genome sequencing (WGS) and phylogenetic comparisons of 140 isolates from predominant spa types t279, t1451, and t571 to examine possible transmission routes and identify genomic and epidemiologic features associated with the spread of dominant clones. We identified two major MSSA clones: sequence type 398 (ST398), common in the local community, and ST1898, not previously encountered in the region. ST398 NICU isolates formed distinct clusters with closely related community isolates from previously published data sets, suggesting multiple sources of acquisition, such as family members or staff, including residents of the local community. In contrast, ST1898 isolates were nearly identical, pointing to clonal expansion within the NICU. Almost all ST1898 isolates harbored plasmids encoding mupirocin resistance (mupA), suggesting an association between the proliferation of this clone and decolonization efforts with mupirocin. Comparative genomics indicated genotype-specific pathways of introduction and spread of MSSA via community-associated (ST398) or health care-associated (ST1898) sources and the potential role of mupirocin resistance in dissemination of ST1898. Future surveillance efforts could benefit from routine genotyping to inform clone-specific infection prevention strategies. IMPORTANCE Methicillin-susceptible Staphylococcus aureus (MSSA) is a significant pathogen in neonates. However, surveillance efforts in neonatal intensive care units (NICUs) have focused primarily on methicillin-resistant S. aureus (MRSA), limiting our understanding of colonizing and infectious MSSA clones which are prevalent in the NICU. Here, we identify two dominant colonizing MSSA clones during an 18-month surveillance effort in a level III to IV NICU, ST398 and ST1898. Using genomic surveillance and phylogenetic analysis, coupled with epidemiological investigation, we found that these two sequence types had distinct modes of spread, namely the suggested exchange with community reservoirs for ST398 and the contribution of antibiotic resistance to dissemination of ST1898 in the health care setting. This study highlights the additional benefits of whole-genome surveillance for colonizing pathogens, beyond routine species identification and genotyping, to inform targeted infection prevention strategies.

Attenuating the virulence of the resistant superbug Staphylococcus aureus bacteria isolated from neonatal sepsis by ascorbic acid, dexamethasone, and sodium bicarbonate

Background

Infections affecting neonates caused by Staphylococcus aureus are widespread in healthcare facilities; hence, novel strategies are needed to fight this pathogen. In this study, we aimed to investigate the effectiveness of the FDA-approved medications ascorbic acid, dexamethasone, and sodium bicarbonate to reduce the virulence of the resistant Staphylococcus aureus bacteria that causes neonatal sepsis and seek out suitable alternatives to the problem of multi-drug resistance.

Methods

Tested drugs were assessed phenotypically and genotypically for their effects on virulence factors and virulence-encoding genes in Staphylococcus aureus. Furthermore, drugs were tested in vivo for their ability to reduce Staphylococcus aureus pathogenesis.

Results

Sub-inhibitory concentrations (1/8 MIC) of ascorbic acid, dexamethasone, and sodium bicarbonate reduced the production of Staphylococcus aureus virulence factors, including biofilm formation, staphyloxanthin, proteases, and hemolysin production, as well as resistance to oxidative stress. At the molecular level, qRT-PCR was used to assess the relative expression levels of crtM, sigB, sarA, agrA, hla, fnbA, and icaA genes regulating virulence factors production and showed a significant reduction in the relative expression levels of all the tested genes.

Conclusions

The current findings reveal that ascorbic acid, dexamethasone, and sodium bicarbonate have strong anti-virulence effects against Staphylococcus aureus. Thus, suggesting that they might be used as adjuvants to treat infections caused by Staphylococcus aureus in combination with conventional antimicrobials or as alternative therapies.

Thymol Disrupts Cell Homeostasis and Inhibits the Growth of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a typical kind of symbiotic bacteria, which can cause human pneumonia, food poisoning, and other health problems. Nowadays, the corresponding prevention and treatment have been a hot issue of general concern in related research areas. However, the mechanism of action against S. aureus is not well understood. In order to tackle such problem, we used broth microdilution to discuss the antibacterial effect of 5-methyl-2-isopropylphenol and determine inhibitory concentration. In addition, membrane potential and lipid peroxidation levels were also measured under experimental conditions. The experimental results suggested that 300 μg/mL thymol might cause cell membrane damage and decrease of NADPH concentration and increase of NADP⁺ and lipid peroxidation level. In such condition, thymol has the potential to result in membrane rupture and disruption of cellular homeostasis. Furthermore, we also found that NOX₂ is involved in maintaining the balance of NADPH/NADP⁺ in cells. Finally, our work confirms that NOX₂ is a potential downstream target for thymol in the cell. Such target can provide specific guidance and recommendations for its application in antifungal activity. Meanwhile, our study also provides a new inspiration for the molecular mechanism of thymol's bacteriostatic action.

Methicillin-resistant Staphylococcus aureus transmission and hospital-acquired bacteremia in a neonatal intensive care unit in Greece

BACKGROUND

Staphylococcus aureus is a common pathogen causing hospital acquired infections (HAIs) in neonates. In this study, the epidemiology of methicillin-resistant S. aureus (MRSA) colonization and infections in a 30-bed, level III university-affiliated neonatal intensive care unit (NICU) located in a children's hospital was retrospectively investigated for the period 2014-2018.

METHODS

Genes encoding Panton-Valentine Leukocidin (lukS/lukF-PV, PVL), toxic shock syndrome toxin (tst), exfoliative toxins (eta, etb), and the resistance genes mecA, mecC and fusB, were defined in 46 representative strains by PCRs. Relatedness of strains was assessed by MLST.

RESULTS

Of 1538 neonates, 77 (5%) had a positive culture for MRSA (23/77 were NICU-acquired and 54/77 imported cases). Four MRSA bacteremias occurred. Most isolates were multi-resistant. One major clone was identified, ST225, among 40 tested neonatal strains (23/40, 58%). Of these, 14/23 were imported from the same maternity hospital (MH). Another clone, ST217, was predominant (4/6) among health care workers (HCWs), found colonized. Four isolates classified as ST80 were PVL-positive. Additional four strains carried tst (10%), belonging to ST30 and ST225 (two strains each), and two etb. The implicated MH was notified for the problem, decolonization treatment was successfully performed in HCWs and neonates. Strengthening of infection control measures with emphasis on hand hygiene was applied.

CONCLUSIONS

Uncovering reservoirs for on-going MRSA transmission in NICUs has proved challenging. Well known nosocomial MRSA clones are being constantly introduced and transmitted via MHs and HCWs. Effective infection prevention and control requires constant vigilance.

Surveillance for Colonization, Transmission, and Infection With Methicillin-Susceptible Staphylococcus aureus in a Neonatal Intensive Care Unit

IMPORTANCE

Staphylococcus aureus is one of the leading causes of infections in neonatal intensive care units (NICUs). Most studies in this patient group focus on methicillin-resistant S aureus or the outbreak setting, whereas data for methicillin-susceptible S aureus are limited.

OBJECTIVES

To identify risk factors for S aureus colonization and infections in hospitalized newborns and to investigate S aureus transmission and its dynamics in a nonoutbreak setting.

DESIGN, SETTING, AND PARTICIPANTS

This monocentric cohort study in a tertiary NICU in Heidelberg, Germany, enrolled all hospitalized neonates (n = 590) with at least 1 nasal screening swab positive for S aureus. Data were collected from January 1, 2018, to December 31, 2019.

EXPOSURES

Weekly screening for S aureus colonization was performed for all newborns until discharge.

MAIN OUTCOMES AND MEASURES

The primary end point was any S aureus infection until hospital discharge. Transmission of S aureus and performance of routine typing to detect transmissions were defined as the secondary outcomes of the study.

RESULTS

In total, 590 newborns were enrolled (276 [46.8%] female and 314 [53.2%] male; 220 [37.3%] with birthweight <1500 g; 477 [80.8%] preterm; 449 [76.1%] singletons; 419 [71.5%] delivered via cesarean section). The median length of stay was 26 (range, 10-62) days. Overall, 135 infants (22.9%) were colonized by S aureus at some time during their hospital stay. The median time to first detection was 17 (interquartile range, 11-37) days. The overall incidence of S aureus infection was 1.7% (10 of 590). Low birth weight (<1500 g [odds ratio, 9.3; 95% CI, 5.9-14.6; P < .001]) and longer hospital stay (odds ratio, 2.3; 95% CI, 1.9-2.7; P < .001) were associated with colonization. Nasal carriage was significantly associated with S aureus infection (odds ratio, 8.2; 95% CI, 2.1-32.3; P = .002). A total of 123 of 135 colonization isolates were sequenced. All recoverable infection isolates (4 of 7) of newborns with colonization were genetically identical to the colonizing isolate. Whole-genome sequencing indicated 23 potential transmission clusters.

CONCLUSIONS AND RELEVANCE

The findings of this cohort study suggest that nasal colonization is a relevant risk factor for S aureus infection in a nonoutbreak NICU setting. In colonized newborns, infection and colonization isolates were genetically identical, suggesting that eradication of colonization may be a useful measure to prevent infection. Further investigations are necessary to validate and assess the generalizability of our findings.

Perinatal Gram-Positive Bacteria Exposure Elicits Distinct Cytokine Responses In Vitro

During pregnancy, infections caused by the gram-positive bacteria Enterococcus faecalis (E. faecalis), Streptococcus agalacticae (S. agalacticae), and Staphylococcus aureus (S. aureus) are major reasons for preterm labor, neonatal prematurity, meningitis, or sepsis. Here, we propose cytokine responses to bacterial infections by the immature perinatal immune system as central players in the pathogenesis of preterm birth and neonatal sepsis. We aimed to close the gap in knowledge about such cytokine responses by stimulating freshly isolated umbilical blood mononuclear cells (UBMC) with lysates of E. faecalis, S. agalacticae, and S. aureus collected from pregnant women in preterm labor. Bacterial lysates and, principally, S. aureus and S. agalacticae distinctly triggered most of the eleven inflammatory, anti-inflammatory, TH1/TH2 cytokines, and chemokines quantified in UBMC culture media. Chemokines depicted the most robust induction. Among them, MIP-1β was further enhanced in UBMC from female compered to male newborn infants. Due to its stability and high levels, we investigated the diagnostic value of IL-8. IL-8 was critically upregulated in cord blood of preterm neonates suffering from infections compared to gestational age-matched controls. Our results provide novel clues about perinatal immunity, underscoring a potential value of IL-8 for the timely detection of infections and suggesting that MIP-1β constitutes an early determinant of sex-specific immunity, which may contribute, e.g., to male's vulnerability to preterm birth.

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.