Methicillin-resistant Staphylococcus aureus in cystic fibrosis patients: do we need to care? A cohort study

Association between early chronic methicillin-susceptible Staphylococcus aureus colonization and lung function in children with cystic fibrosis

BACKGROUND

Our aim was to determine whether early chronic methicillin-susceptible Staphylococcus aureus (MSSA) colonization in children with cystic fibrosis (CF) is associated at 8 years of age with poorer lung function, poorer nutritional status, and increased exacerbation frequency.

METHODS

In this retrospective cohort study, a total of 52 children with chronic MSSA colonization were included. Of them, 26 were chronically colonized with MSSA before the age of 4 years (early onset), and 26 were chronically colonized from 4 years to 6 years of age (late-onset). At the age of 8 years, lung function, body mass index (BMI) as an indicator of nutritional status and frequency of pulmonary exacerbations were compared between two groups.

RESULTS

At 8 years of age, BMI was similar between the early-onset and late-onset groups (15.0 [min-max: 12.9-26.8] vs. 15.7 (min-max: 13.0-24.9), p = 0.327]. Percentage of forced expiratory volume in 1 s (FEV1) and forced expiratory flow between 25% and 75% of vital capacity (FEF25-75) in 8-year-old children were significantly lower in the early onset group compared to the late-onset group (98 [min-max: 44-139] vs. 106.5 [min-max: 82-131], p = 0.047; 84.9 ± 25.5 vs. -102.3 ± 26.3, respectively; p = 0.019], although the percentage of forced vital capacity did not differ significantly between two groups (93.5 [min-max: 45-131] vs. 103 [min-max: 84-119], respectively; p = 0.092). Exacerbation frequency between the ages of 6 and 8 years in the early onset group was higher compared to the late-onset group according to the Poisson regression model [1 (min-max:0-10) vs 0 (min-max:0-4), respectively; p = 0.044].

CONCLUSIONS

Early chronic MSSA colonization is associated with poorer lung function and frequent exacerbations in children with CF. However, further studies are needed to reveal the cause-and-effect relationship between early chronic MSSA colonization and pulmonary outcome.

The History of Methicillin-Resistant Staphylococcus aureus in Brazil

Since the emergence of MRSA in the 1960s, a gradual increase in infections by resistant bacteria has been observed. Clinical manifestations may vary from brand to critical condition due to host risk factors, as well as pathogen virulence and resistance. The high adaptability and pathogenic profile of MRSA clones contributed to its spread in hospital and community settings. In Brazil, the first MRSA isolates were reported in the late 1980s, and since then different genetic profiles, such as the Brazilian epidemic clone (BEC) and other clones considered a pandemic, became endemic in the Brazilian population. Additionally, Brazil's MRSA clones were shown to be able to transfer genes involved in multidrug resistance and enhanced pathogenic properties. These events contributed to the rise of highly resistant and pathogenic MRSA. In this review, we present the main events which compose the history of MRSA in Brazil, including numbers and locations of isolation, as well as types of staphylococcal cassette chromosome mec (SCCmec) found in the Brazilian territory.

Molecular characterisation of methicillin-resistant Staphylococcus aureus from chronically colonised cystic fibrosis paediatric patients in Brazil

Persistent methicillin-resistant Staphylococcus aureus (MRSA) infection in cystic fibrosis (CF) patients has been associated with a more rapid decline in lung function, increased hospitalisation and mortality. The aim of this study was to evaluate the clonal relationships among 116 MRSA isolates from 12 chronically colonised CF pediatric patients over a 6-year period in a Rio de Janeiro CF specialist centre. Isolates were characterised by antimicrobial resistance, SCCmec type, presence of Panton-Valentine Leukocidin (PVL) genes and grouped according to DNA macrorestriction profile by pulsed-field gel electrophoresis (PFGE) and spa gene type. High resistance rates were detected for erythromycin (78%) and ciprofloxacin (50%) and SCCmec IV was the most common type (72.4%). Only 8.6% of isolates were PVL positive. High genetic diversity was evident by PFGE (39 pulsotypes) and of nine that were identified spa types, t002 (53.1%) and t539 (14.8%) were the most prevalent. We conclude that the observed homogeneity of spa types within patients over the study period demonstrates the persistence of such strain lineages throughout the course of chronic lung infection.

Staphylococcus aureus in cystic fibrosis: pivotal role or bit part actor?

PURPOSE OF REVIEW

The cystic fibrosis (CF) lung has long been appreciated as a competitive niche for complex interactions between bacterial species. The individual relationships between effects on the host, and thereafter clinical outcomes, has been poorly understood. We aim to describe the role of Staphyloccus aureus, one of the most commonly encountered bacteria cultured from the respiratory tracts of people with CF, and it's complex interplay with other organisms, with particular attention to Pseudomonas aeruginosa.

RECENT FINDINGS

We describe the challenges posed in understanding the role that S. aureus plays in the CF lung, including the difficulties in interpreting culture results depending upon sampling technique, relationships with P. aeruginosa and the rest of the microbiome, as well as discussing the relative merits and potential harms of antibiotic prophylaxis. Finally, we describe the particular challenge of methicillin-resistant S. aureus.

SUMMARY

We describe research underway that will address the long-held contentious issues of antibiotic prophylaxis. We also describe the emerging research interest in determining whether, at differences phases in the evolution of CF airways infection, S. aureus infection can have both harmful and protective effects for the host.

High-resolution computed tomography findings in young infants with cystic fibrosis detected by newborn screening

OBJECTIVE

High-resolution computed tomography (HRCT) allows the early detection of pathological changes in the lung structure, and reproducible scoring systems can be used to quantify chest computed tomography (CT) findings in patients with cystic fibrosis (CF). The aim of the study was to describe early HRCT findings according to a validated scoring system in infants with CF diagnosed by newborn screening (NBS).

METHODS

This cross-sectional study included infants with CF diagnosed by NBS who were born between January 2013 and January 2017 and who underwent HRCT scanning within the first year after diagnosis when they were clinically stable. The CT scans were evaluated using the modified Bhalla score.

RESULTS

Thirty-two subjects underwent HRCT scanning. The mean total-modified Bhalla score was 3.6±2.1, and 93.8% of the scans were abnormal. Pseudomonas aeruginosa airway colonization was associated with increased modified Bhalla score values. Bronchial wall thickening was the most common feature (90.6%), followed by bronchial collapse/consolidation (59.4%), mosaic attenuation/perfusion (50%), bronchiectasis (37.5%) and mucus plugging (15.6%). Bronchial wall thickening was diffuse in most of the patients.

CONCLUSION

A substantial proportion of infants diagnosed with CF after detection by NBS already showed evidence of lung disease. P. aeruginosa colonization was associated with increased Bhalla scores, highlighting the importance of this CF pathogen in early structural lung disease. The presence of bronchial wall thickening at such a young age may reflect the presence of airway inflammatory processes. The detection and quantification of structural abnormalities with the modified Bhalla score may aid in the identification of lung disease before it is clinically apparent.