Staphylococcus aureus and its Effects on the Prognosis of Bronchiectasis

Development of dual polymerase spiral reaction for detection of Listeria monocytogenes and Staphylococcus aureus simultaneously

Listeria monocytogenes and Staphylococcus aureus are prevalent foodborne pathogens responsible for poisoning humans with food. The present study was devoted to the establishment of a method based on dual polymerase spiral reaction (dual-PSR) and melting curve analysis for concurrent identification L. monocytogenes and S. aureus. Specifically, the primer pairs were aimed at the conserved hlyA gene of L. monocytogenes and that of S. aureus (nuc). These reactions were carried out isothermally at 65 °C for 45 min within the same reaction vessel, and the amplified products were analyzed in a melting curve. Different average temperatures of melting allow the discrimination in the dual-PSR assay between the two target bacteria. The limits of simultaneous determination of L. monocytogenes and S. aureus in artificially contaminated fresh-cut fruit samples were 1 × 10-4 ng of genomic DNA and 1 × 102 CFU/g, respectively. This method is characterized by its expeditious nature and simultaneous detection capability, and it promises to be a valuable technology for the monitoring of pathogenic microorganisms around health and quality control of foodstuffs within that industry.

Kanamycin promotes biofilm viability of MRSA strains showing extremely high resistance to kanamycin

Staphylococcus aureus is widely distributed in environment and can cause various human infection and food poisoning cases. Also, this pathogen is a typical biofilm former, which further complicates its pathogenicity. Antibiotics have been widely used to eliminate pathogenic bacteria, but their indiscriminate use has also led to the widespread emergence of drug-resistant bacteria, such as Methicillin-Resistant Staphylococcus aureus (MRSA). In this study, the effect of antibiotics on biofilm formation of MRSA strains 875 and 184 was explored. Firstly, MRSA 875 belongs to SCCmec type IV, ST239, carrying the atl, icaA, icaD, icaBC, and aap genes, and MRSA 184 belongs to SCCmec type II, ST5, carrying the atl, icaD, icaBC, aap, and agr genes. Then, a total of 8 antibiotics have been selected, including kanamycin, gentamycin, cipprofloxacin, erythromycin, meropenem, penicillin G, tetracycline, vancomycin. Minimum inhibitory concentrations (MICs) of each antibiotic were determined, and MIC of MRSA 875 and 184 to kanamycin/gentamicin are 2048/64 μg/mL and 2048/4 μg/mL, respectively. A total of 10 concentrations, ranging from 1/128 to 4 MIC with 2-fold, were used to study biofilm formation. Biofilm biomass and viability were determined during different phases, including initial adhesion (8 h), proliferation (16 h), accumulation (24 h) and maturation (48 h). Importantly, kanamycin at specific concentrations showed significant promotion of biofilm biomass and biofilm viability, with none of such observation acquired from other antibiotics. This study provides scientific basis and new research ideas for the quality control technology of microorganisms and safety prevention of MRSA.

Impact of bacterial co-isolation on treatment initiation and long-term prognosis of patients with nontuberculous mycobacterial pulmonary disease: analysis of a prospective cohort study

BACKGROUND

Nontuberculous mycobacterial pulmonary disease (NTM-PD), a chronic respiratory condition, presents a growing challenge globally. Uncertainties exist regarding the impact of concurrent bacterial co-isolation on treatment initiation and long-term prognosis.

METHODS

This study analysed data from participants enrolled in an ongoing prospective observational cohort study on NTM-PD (NCT01616745) between 1 July 2011, and 31 December 2022, who provided sputum samples for bacterial culture at enrolment. Identification of potential pathogenic microorganisms (PPMs) was defined as a positive bacterial culture. Clinical characteristics were compared between NTM-PD patients with Pseudomonas, non-pseudomonal PPMs, and those without PPM co-isolation. Cox proportional hazard regression models were employed to assess the association of bacterial co-isolation with rates of NTM-PD treatment initiation and all-cause mortality.

RESULTS

Overall, 453 patients (median age, 62 years; 30% male) were included in the analysis. PPMs were co-isolated in 77 patients (17%), including 13 with Pseudomonas species. Co-isolation of Pseudomonas was associated with a significantly higher erythrocyte sedimentation rate (P = 0.02) and St. George's Respiratory Questionnaire score (P = 0.01). Non-pseudomonal PPM co-isolation was significantly associated with a higher likelihood of NTM-PD treatment initiation (adjusted hazards ratio [aHR], 1.56, 95% confidence interval [CI], 1.03-2.36, P = 0.036), whereas co-isolation of Pseudomonas was independently correlated with increased all-cause mortality (aHR, 3.25, 95% CI, 1.08-9.84, P = 0.037).

CONCLUSIONS

Our findings emphasize the importance of microbial surveillance, as bacterial co-isolation affects treatment initiation and prognosis in patients with NTM-PD.

Multiplex polymerase spiral reaction for simultaneous detection of Salmonella typhimurium and Staphylococcus aureus

Salmonella typhimurium (S. typhimurium) and Staphylococcus aureus (S. aureus) are common food-borne pahogens that cause food poisoning in humans. In this study, we developed a method for the simultaneous determination of S. typhimurium and S. aureus based on multiplex polymerase spiral reaction (m-PSR) and melting curve analysis. Two pairs of primers were designed specifically to target the conserved invA gene of S. typhimurium and nuc gene of S. aureus, and the nucleic acid amplification reaction was achieved under isothermal conditions in the same reaction tube for 40 min at 61 °C, melting curve analysis of the amplification product was carried out. The distinct mean melting temperature allowed simultaneous differentiation of the two target bacteria in the m-PSR assay. The limit of detection of S. typhimurium and S. aureus that could be detected simultaneously was 4.1 × 10^-4 ng genomic DNA and 2 × 10¹ CFU/mL pure bacterial culture. Based on this method, analysis of artificially contaminated samples showed excellent sensitivity and specificity consistent with those of pure bacterial cultures. This method is rapid, simultaneous and promises to be a useful tool for the detection of food-borne pathogens in the food industry.

Impact of Chronic Bronchial Infection by Staphylococcus aureus on Bronchiectasis

The objective of the study was to analyze the factors associated with chronic bronchial infection (CBI) due to methicillin-susceptible Staphylococcus aureus (SA) and assess the clinical impact on severity, exacerbations, hospitalizations, and loss of lung function compared to patients with no isolation of PPMs in a large longitudinal series of patients from the Spanish bronchiectasis registry (RIBRON). Material and methods: A prospective, longitudinal, multicenter study was conducted with patients included in the RIBRON registry between January 2015 and October 2020. The inclusion criteria were an age of 18 years or older and an initial diagnosis of bronchiectasis. Patients recorded in the registry had a situation of clinical stability in the absence of an exacerbation in the four weeks before their inclusion. All patients were encouraged to provide a sputum sample at each visit for microbiological culture. Annual pulmonary function tests were performed according to the national spirometry guidelines. Results: A total of 426 patients were ultimately included in the study: 77 patients (18%) with CBI due to SA and 349 (82%) who did not present any isolation of PPMs in sputum. The mean age was 66.9 years (16.2), and patients 297 (69.7%) were female, with an average BMI of 25.1 (4.7) kg/m2 and an average Charlson index of 1.74 (1.33). The mean baseline value of FEV1 2 L was 0.76, with a mean FEV1% of 78.8% (23.1). One hundred and seventy-two patients (40.4%) had airflow obstruction with FEV1/FVC < 0.7. The mean predictive FACED score was 1.62 (1.41), with a mean value of 2.62 (2.07) for the EFACED score and 7.3 (4.5) for the BSI score. Patients with CBI caused by SA were younger (p < 0.0001), and they had a lower BMI (p = 0.024) and more exacerbations in the previous year (p = 0.019), as well as in the first, second, and third years of follow-up (p = 0.020, p = 0.001, and p = 0.018, respectively). As regards lung function, patients with CBI due to SA had lower levels of FEV1% at the time of inclusion in the registry (p = 0.021), and they presented more frequently with bronchial obstruction (p = 0.042). A lower age (OR: 0.97; 95% CI: 0.94−0.99; p < 0.001), lower FEV1 value% (OR: 0.98; 95% CI: 0.97−0.99; p = 0.035), higher number of affected lobes (OR: 1.53; 95% CI: 1.2−1.95; p < 0.001), and the presence of two or more exacerbations in the previous year (OR: 2.33; 95% CI: 1.15−4.69; p = 0.018) were observed as independent factors associated with CBI due to SA. The reduction in FEv1% in all patients included in the study was −0.31%/year (95% CI: −0.7; −0.07) (p = 0.110). When the reduction in FEv1% is analyzed in the group of patients with CBI due to SA and the group without pathogens, we observed that the reduction in FEV1% was −1.19% (95% CI: −2.09, −0.69) (p < 0.001) in the first group and −0.02% (95% CI: −0.07, −0.01) (p = 0.918) in the second group. According to a linear regression model (mixed effects) applied to determine which factors were associated with a more pronounced reduction in FEv1% in the overall group (including those with CBI due to SA and those with no PPM isolation), age (p = 0.0019), use of inhaled corticosteroids (p = 0.004), presence of CBI due to SA (p = 0.007), female gender (p < 0.001), and the initial value of FEV1 (p < 0.001) were significantly related. Conclusions: Patients with non-CF bronchiectasis with CBI due to SA were younger, with lower FEV1% values, more significant extension of bronchiectasis, and a higher number of exacerbations of mild to moderate symptoms than those with no PPM isolation in respiratory secretions. The reduction in FEV1% was −1.19% (95% CI: −2.09, −0.69) (p < 0.001) in patients with CBI caused by SA.