Association between microbial characteristics and poor outcomes among patients with methicillin-resistant Staphylococcus aureus pneumonia: a retrospective cohort study

Clinical characteristics and risk factors for mortality in patients with community-acquired staphylococcal pneumonia

Staphylococcus aureus (S. aureus) is increasing in prevalence as a causative pathogen of community-acquired pneumonia (CAP). However, reports on the clinical features and mortality risk factors for S. aureus CAP are limited. We therefore aimed to identify the clinical characteristics and risk factors for mortality in these patients. We performed a post hoc and multivariate analysis of a multicenter prospective observational study that included adult hospitalized patients with S. aureus CAP. To elucidate the features of S. aureus CAP, we comparatively analyzed pneumococcal CAP (PCAP). We analyzed 196 patients with S. aureus CAP and 198 patients with PCAP. S. aureus CAP had a 30-day mortality of 16% (31/196) and a higher frequency of factors such as advanced age, comorbidities, poor functional ability, altered mental status, hypoalbuminemia, hyponatremia/hypernatremia, acidemia, and hypoxemia. In the multivariate analysis, the significant risk factors for mortality in S. aureus CAP were PaO₂/FiO₂ ≤250 [adjusted odds ratio (AOR), 3.29; 95% confidence interval (CI), 1.20-9.04] and albumin <3.0 g/dL (AOR, 2.41; 95% CI, 1.01-5.83). Non-ambulatory status tended to increase the risk (AOR, 2.40; 95% CI, 0.93-6.17). Methicillin resistance was not associated with mortality. In PCAP, hypoalbuminemia and non-ambulatory status affected mortality but hypoxemia did not. In conclusion, patients with S. aureus CAP have distinct clinical features, and their mortality risk factors can include hypoxemia and hypoalbuminemia. Physicians should recognize that the factors influencing mortality might differ somewhat among causative pathogens, and appropriate management should be performed after obtaining information on the causative pathogen.

Dysfunctional accessory gene regulator (agr) as a prognostic factor in invasive Staphylococcus aureus infection: a systematic review and meta-analysis

The accessory gene regulator (agr) locus of Staphylococcus aureus is a quorum-sensing virulence regulator. Although there are many studies concerning the effect of dysfunctional agr on the outcomes of S. aureus infection, there is no systematic review to date. We systematically searched for clinical studies reporting outcomes of invasive S. aureus infections and the proportion of dysfunctional agr among their causative strains, and we performed a meta-analysis to obtain estimates of the odds of outcomes of invasive S. aureus infection with dysfunctional versus functional agr. Of 289 articles identified by our research strategy, 20 studies were meta-analysed for crude analysis of the impact of dysfunctional agr on outcomes of invasive S. aureus infection. Dysfunctional agr was generally associated with unfavourable outcomes (OR 1.32, 95% CI 1.05–1.66), and the impact of dysfunctional agr on outcome was more prominent in invasive methicillin-resistant S. aureus (MRSA) infections (OR 1.54, CI 1.20–1.97). Nine studies were meta-analysed for the impact of dysfunctional agr on the 30-day mortality of invasive S. aureus infection. Invasive MRSA infection with dysfunctional agr exhibited higher 30-day mortality (OR 1.40, CI 1.03–1.90) than that with functional agr. On the other hand, invasive MSSA infection with dysfunctional agr exhibited lower 30-day mortality (OR 0.51, CI 0.27–0.95). In the post hoc subgroup analysis by the site of MRSA infection, dysfunctional agr was associated with higher 30-day mortality in MRSA pneumonia (OR 2.48, CI 1.17–5.25). The effect of dysfunctional agr on the outcome of invasive S. aureus infection may vary depending on various conditions, such as oxacillin susceptibility and the site of infection. Dysfunctional agr was generally associated with unfavourable clinical outcomes and its effect was prominent in MRSA and pneumonia. Dysfunctional agr may be applicable for outcome prediction in cases of invasive MRSA infection with hardly eradicable foci such as pneumonia.

Prevalence, clinical expression, invasiveness and outcome of Staphylococcus aureus containing Panton-Valentine leukocidin in children treated in a university hospital of Lithuania

Background: There is a high prevalence of Staphylococcus aureus virulence factor Panton-Valentine leukocidin (PVL) in North-East parts of Europe. The aim was to evaluate data regarding the PVL occurrences in Lithuania, determine the relationship with Methicillin resistant Staphylococcus aureus (MRSA), association with demographic and clinical conditions, invasiveness and severity of the disease in children treated in hospital Kauno klinikos (KK).Methods: We performed a prospective case-cohort single-center study on paediatric patients hospitalized from 2012 to 2015 to KK. We compared characteristics in PVL positive [SA-PVL(+)] and PVL negative [SA-PVL(-)] groups among non-invasive and invasive infections. Logistic regression was performed to detect PVL predicting factors and Cox regression was presented to define factors associated with admission to intensive care unit (ICU).Results: PVL was detected in 51.5%, MRSA in 7.0% and MRSA-PVL(+) in 4.8% of cases. In general, PVL was associated with older age comparing with SA-PVL(-) (median 8.5 vs. 4.0 years, p < .001). Skin and soft tissue infections were presented in 87.9% of all SA-PVL(+) cases. Invasive infections (44.7% vs. 12.1%, p < .001) and co-morbidities (20.5% vs. 2.9%, p < .001) were associated with SA-PVL(-) infections compared to SA-PVL(+), but ICU admission number was higher in invasive SA-PVL(+) cases comparing to invasive SA-PVL(-) cases (41.2% vs. 10.2%, p = .007).Conclusions: There was a high prevalence of pvl gene in patients treated in KK. SA-PVL(+) infections were associated with SSTI and were not common in invasive infections, but the invasive infections caused by SA-PVL(+) were related to severe disease progression and admission to ICU.

The association between pathogen factors and clinical outcomes in patients with Staphylococcus aureus bacteraemia in a tertiary hospital, Cape Town

BACKGROUND

Staphylococcus aureus is a serious pathogen, able to cause life-threatening infections such as bacteraemia. The association between S. aureus microbial characteristics and clinical outcomes is under-investigated in African settings. This study aimed to determine the molecular epidemiology and virulence characteristics of S. aureus isolates from bacteraemic patients at Tygerberg Hospital, South Africa, and to investigate the associations between pathogen characteristics and clinical outcomes.

METHODS

This study included 199 S. aureus isolates collected from blood cultures between February 2015 and March 2017. Methicillin resistance was determined using disc diffusion and all resistant isolates were further characterized by staphylococcal cassette chromosome mec (SCCmec) typing. Genotyping was done using spa and agr typing, and agr functionality was assessed using the phenotypic δ-haemolysin assay. Logistic regression models were performed to describe the associations between strain characteristics and the clinical outcomes methicillin resistance, in-hospital mortality, and length of stay (LOS).

RESULTS

Of the 199 S. aureus isolates collected, 27% were MRSA, and the overall crude in-hospital mortality rate was 29%. Seventy-three different spa types were identified, including seven new types. Agr I was the most common type, in 99 (49.7%) isolates, followed by agr II, III, and IV in 57 (28.6%), 37 (18.6%), and six (3%) isolates, respectively. Agr dysfunctionality was observed in 25 (13%) isolates, mostly belonging to spa-clonal complex (CC) 012. Methicillin resistance was significantly associated with hospital-acquired infection (odds ratio (OR) 4.77, 95% confidence interval (CI) 2.09-10.87). A significant increase in mortality was observed with increasing age (OR 7.48, 95% CI 2.82-19.8) and having a hospital-acquired infection (OR 2.26, 95% CI 1.12-4.55). S. aureus strains with a functional agr system showed an association with longer duration of stay (OR 1.66, 95% CI 0.93-2.99).

CONCLUSIONS

We report the lowest MRSA prevalence at Tygerberg Hospital for the past 10 years, and agr dysfunctionality was shown to be driven by a certain genotype, spa-CC012. Despite the limited available clinical data, the study provided insights into associations between S. aureus epidemiology and agr-related virulence characteristics, and clinical outcomes.

Virulence Factor Targeting of the Bacterial Pathogen Staphylococcus aureus for Vaccine and Therapeutics

BACKGROUND

Staphylococcus aureus is a major bacterial pathogen capable of causing a range of infections in humans from gastrointestinal disease, skin and soft tissue infections, to severe outcomes such as sepsis. Staphylococcal infections in humans can be frequent and recurring, with treatments becoming less effective due to the growing persistence of antibiotic resistant S. aureus strains. Due to the prevalence of antibiotic resistance, and the current limitations on antibiotic development, an active and highly promising avenue of research has been to develop strategies to specifically inhibit the activity of virulence factors produced S. aureus as an alternative means to treat disease.

OBJECTIVE

In this review we specifically highlight several major virulence factors produced by S. aureus for which recent advances in antivirulence approaches may hold promise as an alternative means to treating diseases caused by this pathogen. Strategies to inhibit virulence factors can range from small molecule inhibitors, to antibodies, to mutant and toxoid forms of the virulence proteins.

CONCLUSION

The major prevalence of antibiotic resistant strains of S. aureus combined with the lack of new antibiotic discoveries highlight the need for vigorous research into alternative strategies to combat diseases caused by this highly successful pathogen. Current efforts to develop specific antivirulence strategies, vaccine approaches, and alternative therapies for treating severe disease caused by S. aureus have the potential to stem the tide against the limitations that we face in the post-antibiotic era.

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.