Staphylococcus aureus: a continuously evolving and formidable pathogen in the neonatal intensive care unit

Treatment of persistent methicillin-susceptible Staphylococcus aureus bacteremia and presumed osteomyelitis with oxacillin and ertapenem in a premature neonate

Neonatal sepsis remains a high cause of morbidity and mortality in preterm neonates. Methicillin-susceptible Staphylococcus aureus (MSSA) can cause persistent bloodstream infections and invasive disease in neonates. We report the first published case of persistent MSSA bacteremia in a preterm neonate successfully treated with oxacillin and ertapenem combination therapy.

Molecular epidemiology of methicillin-sensitive Staphylococcus aureus in the neonatal intensive care unit

BACKGROUND

Staphylococcus aureus-both meticillin-resistant S. aureus (MRSA) and meticillin-sensitive S. aureus (MSSA)-is a major cause of neonatal infections. Infection control measures have not lowered the incidence of MSSA infections to the same degree as that of MRSA infections.

AIM

To investigate the transmission pathway of MSSA in neonatal intensive care unit (NICU) using genetic analysis.

METHODS

We swab-tested neonatal patients, their parents, and healthcare workers (HCW) in the NICU at our hospital at the time of hospitalisation and then every month thereafter from 1^st October 2018 to 31^st March 2019. We performed whole-genome sequencing (WGS) to test for MSSA strains. Multilocus sequence typing (MLST) and single nucleotide polymorphism (SNP) analysis were used to identify strains and understand their relatedness.

FINDINGS

There were 16 MSSA-positive patients. Four MSSA-positive patients shared strains from the same phylogenetic groups as those of HCW. One presented the same strain as the parent. MSSA-positive twin neonates shared the same strain. Ten had sporadic strains; 32 of the ninety-seven tested healthcare workers were MSSA positive.

CONCLUSION

The findings of this study suggest that the route of transmission of MSSA in NICU may be through MSSA in the hospital environment in addition to horizontal transmission via healthcare workers. Along with hand hygiene with alcohol, thorough environmental maintenance and parental education are important for infection control in NICUs targeting MSSA.

Clearance of Persistent Staphylococcus aureus Bacteremia in a Preterm Neonate With the Use of Combination Cefazolin and Ertapenem

Late-onset sepsis caused by Staphylococcus aureus is a serious and relatively common complication encountered by preterm neonates in NICUs. Typical treatment regimens for invasive methicillin-sensitive Staphylococcus aureus (MSSA) include semisynthetic beta lactam antibiotics, such as nafcillin. This report describes the first use of a combination of cefazolin and ertapenem to successfully treat persistent MSSA bacteremia in a preterm neonate who failed traditional first-line therapy.

Aetiology of invasive bacterial infection and antimicrobial resistance in neonates in sub-Saharan Africa: a systematic review and meta-analysis in line with the STROBE-NI reporting guidelines

BACKGROUND

Aetiological data for neonatal infections are essential to inform policies and programme strategies, but such data are scarce from sub-Saharan Africa. We therefore completed a systematic review and meta-analysis of available data from the African continent since 1980, with a focus on regional differences in aetiology and antimicrobial resistance (AMR) in the past decade (2008-18).

METHODS

We included data for microbiologically confirmed invasive bacterial infection including meningitis and AMR among neonates in sub-Saharan Africa and assessed the quality of scientific reporting according to Strengthening the Reporting of Observational Studies in Epidemiology for Newborn Infection (STROBE-NI) checklist. We calculated pooled proportions for reported bacterial isolates and AMR.

FINDINGS

We included 151 studies comprising data from 84 534 neonates from 26 countries, almost all of which were hospital-based. Of the 82 studies published between 2008 and 2018, insufficient details were reported regarding most STROBE-NI items. Regarding culture positive bacteraemia or sepsis, Staphylococcus aureus, Klebsiella spp, and Escherichia coli accounted for 25% (95% CI 21-29), 21% (16-27), and 10% (8-10) respectively. For meningitis, the predominant identified causes were group B streptococcus 25% (16-33), Streptococcus pneumoniae 17% (9-6), and S aureus 12% (3-25). Resistance to WHO recommended β-lactams was reported in 614 (68%) of 904 cases and resistance to aminoglycosides in 317 (27%) of 1176 cases.

INTERPRETATION

Hospital-acquired neonatal infections and AMR are a major burden in Africa. More population-based neonatal infection studies and improved routine surveillance are needed to improve clinical care, plan health systems approaches, and address AMR. Future studies should be reported according to standardised reporting guidelines, such as STROBE-NI, to aid comparability and reduce research waste.

FUNDING

Uduak Okomo was supported by a Medical Research Council PhD Studentship.

Diagnosis and management of Panton-Valentine leukocidin toxin associated Staphylococcus aureus infection: an update

The incidence of invasive Staphylococcus aureus (SA) infection has increased in the past decade and is associated with poor outcomes and high mortality rates. Of all the virulence factors, Panton-Valentine Leukocidin (PVL) has received the greatest attention. PVL producing SA strains are more likely to produce severe skin and soft tissue infections (SSTIs) and necrotizing pneumonia. This review focuses on the current evidence on PVL-SA virulence, epidemiology, clinical disease and treatment with relevance to healthcare in India.

Active Surveillance Cultures and Targeted Decolonization Are Associated with Reduced Methicillin-Susceptible Staphylococcus aureus Infections in VLBW Infants

BACKGROUND

Methicillin-susceptible Staphylococcus aureus (MSSA) is a major contributor to infectious episodes of very low birth weight infants (VLBWI), resulting in significant morbidity and mortality.

OBJECTIVE

To examine the efficacy and safety of surveillance cultures and the decolonization of MSSA-colonized VLBWI.

METHODS

VLBWI admitted to our neonatal wards in 2011-2016 were retrospectively analyzed. Rates of MSSA-attributable infections were compared before and after the implementation of active surveillance cultures and the decolonization of MSSA-colonized patients. The mupirocin susceptibility of isolated MSSA strains was routinely tested.

RESULTS

A total of 1,056 VLBWI were included in the study, 552 in the pre-intervention period and 504 in the post-intervention period. The implementation of surveillance cultures and decolonization of colonized patients resulted in a 50% reduction of incidence rates per 1,000 patient-days of MSSA-attributable infections (1.63 [95% CI 1.12-2.31] vs. 0.83 [95% CI 0.47-1.35], p = 0.024). No adverse effects were observed from application of the decolonization protocol with mupirocin and octenidin. No mupirocin-resistant MSSA strains were detected during the study period.

CONCLUSION

Implementation of an active surveillance and decolonization protocol resulted in a reduction of MSSA-attributable infections in VLBWI.

A Mouse Model of Multi-Drug Resistant Staphylococcus aureus-induced Ocular Disease

Staphylococcus aureus infection of the cornea is a significant threat to vision. The percentage of bacterial isolates resistant to antibiotics is increasing as is the percentage of infections caused by methicillin resistant isolates. There is a critical need for additional therapeutic approaches and their development will require the use of animal models to test efficacy. Two mouse models of S. aureus keratitis have been described but only quantified stromal keratitis (corneal clouding and perforation). We have extended these models using the methicillin resistant S. aureus USA300 LAC strain and show that eyelid inflammation and swelling (blepharitis) and corneal neovascularization can be quantified. This expanded model should prove useful in assessing additional effects of antibacterial therapies and additional pathological mechanisms involved in bacterial ocular infection.

A Snapshot on MRSA Epidemiology in a Neonatal Intensive Care Unit Network, Palermo, Italy

Objectives: We performed a 1-year prospective surveillance study on MRSA colonization within the five NICUs of the metropolitan area of Palermo, Italy. The purpose of the study was to assess epidemiology of MRSA in NICU from a network perspective.

Methods: Transfer of patients between NICUs during 2014 was traced based on the annual hospital discharge records. In the period February 2014–January 2015, in the NICU B, at the University teaching hospital, nasal swabs from all infants were collected weekly, whereas in the other four NICUs (A, C, D, E) at 4 week-intervals of time. MRSA isolates were submitted to antibiotic susceptibility testing, SCCmec typing, PCR to detect lukS-PV and lukF-PV (lukS/F-PV) genes and the gene encoding the toxic shock syndrome toxin (TSST-1), multilocus variable number tandem repeat fingerprinting (MLVF), and multilocus sequence typing (MLST).

Results: In the period under study, 587 nasal swabs were obtained from NICU B, whereas 218, 180, 157, and 95 from NICUs A, C, D, and E, respectively. Two groups of NICUs at high prevalence and low prevalence of MRSA colonization were recognized. Overall, 113 isolates of MRSA were identified from 102 infants. Six MLVF types (A–F) were detected, with type C being subdivided into five subtypes. Five sequence types (STs) were found with ST22-IVa being the most frequent type in all NICUs. All the MRSA molecular subtypes, except for ST1-IVa, were identified in NICU B.

Conclusions: Our findings support the need to approach surveillance and infection control in NICU in a network perspective, prioritizing referral healthcare facilities.

A realist analysis of hospital patient safety in Wales: applied learning for alternative contexts from a multisite case study

Background

Hospital patient safety is a major social problem. In the UK, policy responses focus on the introduction of improvement programmes that seek to implement evidence-based clinical practices using the Model for Improvement, Plan-Do-Study-Act cycle. Empirical evidence that the outcomes of such programmes vary across hospitals demonstrates that the context of their implementation matters. However, the relationships between features of context and the implementation of safety programmes are both undertheorised and poorly understood in empirical terms.

Objectives

This study is designed to address gaps in conceptual, methodological and empirical knowledge about the influence of context on the local implementation of patient safety programmes.

Design

We used concepts from critical realism and institutional analysis to conduct a qualitative comparative-intensive case study involving 21 hospitals across all seven Welsh health boards. We focused on the local implementation of three focal interventions from the 1000 Lives+patient safety programme: Improving Leadership for Quality Improvement, Reducing Surgical Complications and Reducing Health-care Associated Infection. Our main sources of data were 160 semistructured interviews, observation and 1700 health policy and organisational documents. These data were analysed using the realist approaches of abstraction, abduction and retroduction.

Setting

Welsh Government and NHS Wales.

Participants

Interviews were conducted with 160 participants including government policy leads, health managers and professionals, partner agencies with strategic oversight of patient safety, advocacy groups and academics with expertise in patient safety.

Main outcome measures

Identification of the contextual factors pertinent to the local implementation of the 1000 Lives+patient safety programme in Welsh NHS hospitals.

Results

An innovative conceptual framework harnessing realist social theory and institutional theory was produced to address challenges identified within previous applications of realist inquiry in patient safety research. This involved the development and use of an explanatory intervention–context–mechanism–agency–outcome (I-CMAO) configuration to illustrate the processes behind implementation of a change programme. Our findings, illustrated by multiple nested I-CMAO configurations, show how local implementation of patient safety interventions are impacted and modified by particular aspects of context: specifically, isomorphism, by which an intervention becomes adapted to the environment in which it is implemented; institutional logics, the beliefs and values underpinning the intervention and its source, and their perceived legitimacy among different groups of health-care professionals; and the relational structure and power dynamics of the functional group, that is, those tasked with implementing the initiative. This dynamic interplay shapes and guides actions leading to the normalisation or the rejection of the patient safety programme.

Conclusions

Heightened awareness of the influence of context on the local implementation of patient safety programmes is required to inform the design of such interventions and to ensure their effective implementation and operationalisation in the day-to-day practice of health-care teams. Future work is required to elaborate our conceptual model and findings in similar settings where different interventions are introduced, and in different settings where similar innovations are implemented.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.

Molecular typing of toxic shock syndrome toxin-1- and Enterotoxin A-producing methicillin-sensitive Staphylococcus aureus isolates from an outbreak in a neonatal intensive care unit

Outbreaks of Staphylococcus aureus are common in neonatal intensive care units (NICUs). Usually they are documented for methicillin-resistant strains, while reports involving methicillin-susceptible S. aureus (MSSA) strains are rare. In this study we report the epidemiological and molecular investigation of an MSSA outbreak in a NICU among preterm neonates. Infection control measures and interventions were commissioned by the Local Public Health Authority and supported by the Robert Koch Institute. To support epidemiological investigations molecular typing was done by spa-typing and Multilocus sequence typing; the relatedness of collected isolates was further elucidated by DNA SmaI-macrorestriction, microarray analysis and bacterial whole genome sequencing. A total of 213 neonates, 123 healthcare workers and 205 neonate parents were analyzed in the period November 2011 to November 2012. The outbreak strain was characterized as a MSSA spa-type t021, able to produce toxic shock syndrome toxin-1 and Enterotoxin A. We identified seventeen neonates (of which two died from toxic shock syndrome), four healthcare workers and three parents putatively involved in the outbreak. Whole-genome sequencing permitted to exclude unrelated cases from the outbreak and to discuss the role of healthcare workers as a reservoir of S. aureus on the NICU. Genome comparisons also indicated the presence of the respective clone on the ward months before the first colonized/infected neonates were detected.

Clinical and Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in a Neonatal Intensive Care Unit in the Decade following Implementation of an Active Detection and Isolation Program

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent source of infection in the neonatal intensive care unit (NICU), often associated with significant morbidity. Active detection and isolation (ADI) programs aim to reduce transmission. We describe a comprehensive analysis of the clinical and molecular epidemiology of MRSA in an NICU between 2003 and 2013, in the decade following the implementation of an MRSA ADI program. Molecular analyses included strain typing by pulsed-field gel electrophoresis, mec and accessory gene regulator group genotyping by multiplex PCR, and identification of toxin and potential virulence factor genes via PCR-based assays. Of 8,387 neonates, 115 (1.4%) had MRSA colonization and/or infection. The MRSA colonization rate declined significantly during the study period from 2.2 to 0.5/1,000 patient days (linear time, P = 0.0003; quadratic time, P = 0.006). There were 19 cases of MRSA infection (16.5%). Few epidemiologic or clinical differences were identified between MRSA-colonized and MRSA-infected infants. Thirty-one different strains of MRSA were identified with a shift from hospital-associated to combined hospital- and community-associated strains over time. Panton-Valentine leukocidin-positive USA300 strains caused 5 of the last 11 infections. Staphylococcal cassette chromosome mec (SCCmec) types II and IVa and agr groups 1 and 2 were most predominant. One isolate possessed the gene for toxic shock syndrome toxin; none had genes for exfoliative toxin A or B. These results highlight recent trends in MRSA colonization and infection and the corresponding changes in molecular epidemiology. Continued vigilance for this invasive pathogen remains critical, and specific attention to the unique host, the neonate, and the distinct environment, the NICU, is imperative.

Neonatal infections due to multi-resistant strains: Epidemiology, current treatment, emerging therapeutic approaches and prevention

Severe infections represent the main cause of neonatal mortality accounting for more than one million neonatal deaths worldwide every year. Antibiotics are the most commonly prescribed medications in neonatal intensive care units. The benefits of antibiotic therapy when indicated are clearly enormous, but the continued and widespread use of antibiotics has generated over the years a strong selective pressure on microorganisms, favoring the emergence of resistant strains. Health agencies worldwide are galvanizing attention toward antibiotic resistance in gram-positive and gram-negative bacteria. Infections in neonatal units due to multidrug and extensively multidrug resistant bacteria are rising and are already seriously challenging antibiotic treatment options. While there is a growing choice of agents against multi-resistant gram-positive bacteria, new options for multi-resistant gram-negative bacteria in the clinical practice have decreased significantly in the last 20 years making the treatment of infections caused by multidrug-resistant pathogens challenging mostly in neonates. Treatment options are currently limited and will be some years before any new treatment for neonates become available for clinical use, if ever. The aim of the review is to highlight the current knowledge on antibiotic resistance in the neonatal population, the possible therapeutic choices, and the prevention strategies to adopt in order to reduce the emergency and spread of resistant strains.

Bloodstream infections and antimicrobial resistance patterns in a South African neonatal intensive care unit

BACKGROUND

Bloodstream infections remain a leading cause of morbidity and mortality in neonatal intensive care units (NICU) worldwide. Commonly isolated NICU pathogens are increasingly resistant to standard antimicrobial treatment regimes.

OBJECTIVES

The primary aim of this study was to determine the burden of bloodstream infections (BSI) in an NICU in a low-to-middle-income country and to describe the spectrum of pathogens isolated together with their drug susceptibility patterns.

METHODS

This retrospective, descriptive study included NICU patients admitted to the Tygerberg Children's Hospital, Cape Town, between 1 January and 31 December 2008. All blood culture samples submitted to the reference laboratory were extracted and clinical data on patients were obtained by hospital record review.

RESULTS

There were 78 culture-confirmed episodes of BSI in 54/503 (11%) patients admitted; median gestational age was 31 weeks (IQR 29-37) and birth weight 1370 g (IQR 1040-2320). Common isolates included coagulase-negative Staphylococcus (22/78, 28%), Klebsiella spp. (17/78, 22%), Acinetobacter spp. (14/78, 18%), Candida spp. (9/78, 11·5%) and methicillin-resistant Staphylococcus aureus (5/78, 6%). There was a predominance of gram-negative organisms (38/78, 48·7%). All Staphylococcus aureus isolates were methicillin-resistant and 59% of Klebsiella pneumoniae isolates were extended spectrum β-lactamase (ESBL) producers. Acinetobacter baumanii isolates showed low susceptibility to the aminoglycosides, carbapenems and cephalosporins. Of 54 infants admitted to the NICU with BSI, 25 (46%) died; 9/25 deaths (36%) were attributable solely to infection.

CONCLUSION

Compared with overall mortality in the NICU, that attributable solely or partly to BSI was high. Many bacterial BSI isolates were resistant to current empiric antibiotic regimens. Regular microbiological and clinical surveillance of BSI in NICUs is required to inform appropriate antibiotic protocols and monitor the impact of infection prevention strategies.

Community-acquired methicillin-resistant Staphylococcus aureus: the new face of an old foe?

The burden of infections caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is increasing among different patient populations globally. As CA-MRSA has become established in healthcare facilities, the range of infections caused by them has also increased. Molecular characterization of CA-MRSA isolates obtained from different centers has revealed significant diversity in their genetic backgrounds. Although many CA-MRSA strains are still susceptible to non-β-lactam antibiotics, multiresistance to non-β-lactam agents has emerged in some clones, posing substantial problems for empirical and directed therapy of infections caused by these strains. Some CA-MRSA clones have acquired the capacity to spread locally and internationally. CA-MRSA belonging to ST80-MRSA-IV and ST30-MRSA-IV appear to be the dominant clones in the countries of the Gulf Cooperation Council (GCC). The emergence of pandemic CA-MRSA clones not only limits therapeutic options but also presents significant challenges for infection control. Continued monitoring of global epidemiology and emerging drug resistance data is critical for the effective management of these infections.

Methicillin-resistant Staphylococcus aureus in the neonatal intensive care unit

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent source of infections affecting premature and critically ill infants in neonatal intensive care units (NICUs). Neonates are particularly vulnerable to colonization and infection with MRSA, and many studies have attempted to identify risk factors that predispose certain infants to its acquisition to discover potential areas for clinical intervention. In addition, epidemiologic assessment of transmission patterns and molecular analysis of changes in the characteristics of MRSA strains over time have helped clarify additional factors affecting MRSA infections in the NICU. Numerous strategies for prevention and eradication have been used with variable rates of success. Despite these interventions, MRSA remains a significant source of morbidity in the NICU population.

Outbreak of skin and soft tissue infections in a hospital newborn nursery in Italy due to community-acquired meticillin-resistant Staphylococcus aureus USA300 clone

BACKGROUND

Community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) is responsible for severe infections in previously healthy people acquired in the community in different areas of the world.

AIM

To report an outbreak of CA-MRSA in a hospital newborn nursery in northern Italy in September-October 2010, its investigation and control measures.

METHODS

The epidemiology of the outbreak is reported. The investigation included screening neonates, parents and staff for MRSA carriage. Molecular strain typing was performed on MRSA isolates.

FINDINGS

The outbreak affected nine neonates with three severe infections. In addition, four mothers had postpartum mastitis, and three mothers and one father had skin infection. The outbreak strain belonged to the USA300 CA-MRSA clone. Asymptomatic carriage of the outbreak strain was found among neonates, parents and hospital staff. The implementation of appropriate infection control measures in the hospital terminated the outbreak.

CONCLUSIONS

To our knowledge, this is the first report of a hospital outbreak caused by the USA300 CA-MRSA clone in Europe. It is important to reinforce infection control measures, particularly in high-risk groups, such as neonates, to prevent USA300 from becoming endemic in European hospitals.

Impact of pasteurization on the antibacterial properties of human milk

Growing evidence favours the use of human milk for the feeding of preterm newborns based on its many beneficial effects. Despite the many benefits, human milk has been associated as a possible vehicle of transmission for a number of infections. Although pasteurization of human milk can diminish the risk of neonatal infection, it also significantly reduces the concentrations of immunological components in human milk due to thermal damage. In order to evaluate the impact of pasteurization on the antibacterial properties of human milk, we aimed to compare the capacity of raw and pasteurized human milk to inhibit bacterial proliferation. Therefore, a single milk sample was collected from ten healthy lactating mothers. Each sample was divided into two aliquots; one aliquot was pasteurized, while the other was kept raw. Both aliquots were inoculated either with Escherichia coli or Staphylococcus aureus and incubated at 37 °C during 8 h. Viable colony counts from the inoculated samples were performed at regular time points to compare the bacterial growth in both forms of breast milk. Relative to the tryptic soy broth control sample, both raw and pasteurized milk samples exhibited an inhibitory effect on the growth of E. coli and S. aureus. Compared with the raw portion, growth inhibition was significantly lower in the pasteurized milk at every time point beyond T0 (after 2, 4 and 8 h of incubation) (p = 0.0003 for E. coli and p < 0.0001 for S. aureus).

CONCLUSION

Our study shows that pasteurization adversely affects the antibacterial properties of human milk.

Epidemic spread of ST1-MRSA-IVa in a neonatal intensive care unit, Italy

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has recently emerged as an important pathogen in neonatal intensive care units (NICUs). The purposes of this study were to characterize methicillin-resistant isolates from an outbreak in a NICU, to examine the genetic traits and clonality of CA-MRSA, and to review the characteristics and outcomes of the neonatal cases and investigate the routes of entry and transmission of the MRSA outbreak strain in the NICU under study.

METHODS

The study NICU practiced an active surveillance program for multidrug-resistant organisms, including weekly cultures for detection of MRSA from nasal swabs among all the admitted neonates. All first isolates from surveillance cultures and all clinical isolates were submitted for susceptibility testing and genotyping. Data from each infant's medical records were prospectively included in a database, and the clinical features and outcomes of the colonized/infected infants were assessed.

RESULTS

A total of 14 infants were colonized or infected by a strain of ST1-MRSA-IVa between April and August 2011. The CA-MRSA strain appeared to have been introduced to the NICU by an infected infant transferred from another hospital. The outbreak was successfully contained by multifaceted infection control interventions.

CONCLUSIONS

The results of this study confirm that NICU is a healthcare setting with a critical permeability to CA-MRSA. Active surveillance including molecular typing can help to detect and monitor the spread of antimicrobial drug-resistant organisms, and thus trigger timely control interventions.

Successful treatment of meticillin-resistant Staphylococcus aureus bacteraemia in a neonate using daptomycin

Daptomycin is licensed for the management of Staphylococcus aureus infections in adults, including those caused by meticillin-resistant S. aureus (MRSA). Few data exist on paediatric use or dose guidance in neonates. We report the case of a neonate with MRSA bacteraemia successfully managed with daptomycin. Dose requirements were substantially higher than those recommended for adults.