The clinical significance of concomitant bacteriuria in patients with Staphylococcus aureus bacteremia. A review and meta-analysis

Risk of infective endocarditis and complicated infection in Staphylococcus aureus bacteremia - a retrospective cohort study on the role of bacteriuria

PURPOSE

S. aureus bacteremia (SAB) is a common and severe infection with high mortality and morbidity. The clinical relevance of the finding of concurrent S. aureus bacteriuria (SABU) is debated. The goal of this study was to analyze whether a concurrent SABU is associated with complicated SAB, infective endocarditis (IE) and mortality.

METHODS

We conducted a retrospective cohort study, reviewing medical charts of all episodes of SAB in patients > 18 years in the region of Skåne, Sweden, between 1st of January and 31st of June 2020. Episodes where a concurrent urine culture was performed were included for analysis. An episode was considered as complicated SAB if there was either attributable mortality, recurrent infection, embolic stroke, or occurrence of a complicated focus of infection.

RESULTS

During the study period, there were 279 episodes of SAB. 154 episodes met the eligibility criteria, of whom 37 (24%) had concurrent SABU. In 78 episodes (51%), the patients had a complicated SAB. There was a significantly lower proportion of complicated SAB for episodes with concurrent SABU (32%), compared to episodes without concurrent SABU (56%), p-value 0.014. Moreover, in the cohort there were 11 episodes (7.1%) of IE and a 30 days mortality rate of 16%, with no difference between the groups with or without SABU.

CONCLUSIONS

There is an association between concurrent SABU and a decreased risk for complicated SAB among patients with SAB. This study found no significant association between SABU and neither IE nor mortality for patients with SAB.

Staphylococcus aureus bacteriuria: implications and management

Background

Staphylococcus aureus is isolated in around 0.2%-4% of positive urinary cultures, more commonly in the contexts of long-term care, urological abnormalities and procedures, male sex, older age and comorbidities. Isolation may represent contamination, colonization, urinary tract infection or bacteraemic seeding from another site, and may be linked to S. aureus bacteraemia. However, there is little guidance on investigation and management of S. aureus bacteriuria. We performed a retrospective analysis of cases in our service, including clinical characteristics, investigations and treatment.

Methods

Data were collected on all urine samples taken from adult patients over a 5-year period from which S. aureus was isolated. Detailed analysis including investigations and management was conducted in those collected over a 1-year period.

Results

From 511 patients, 668 urine cultures positive for S. aureus were identified; 6.5% of cases were positive for MRSA. Of 93 patients who had blood cultures taken, there were 6 cases of S. aureus bacteraemia, 4 of which were associated with urological instrumentation. Of 94 cases analysed in detail, 57% were treated with antibiotics, and 49% had repeat urine cultures. Factors associated with recurrence were urinary catheterization, urological abnormality, diabetes and inpatient status.

Conclusions

Our experience does not support the routine taking of blood cultures or treatment of asymptomatic bacteriuria in well patients with S. aureus bacteriuria in this setting. However, repeat urine culture, and investigation and treatment of higher risk patients, for example, prior to bladder instrumentation, may be warranted. We propose a simple algorithm to guide clinicians.

Purposeful microbiology comment added to urine cultures with Staphylococcus aureus increases orders for follow-up blood cultures

Introduction

Patients with Staphylococcus aureus bacteriuria (SABU) often have underlying invasive disease, including S. aureus bacteremia (SAB). It has been proposed that most patients with SABU should have a blood culture done to rule out SAB. A preliminary audit suggested that our local hospitals had a low rate of follow-up blood culture orders for patients with SABU. In response to this, our microbiology laboratory changed the comment appended to urine cultures with growth of S. aureus to make a more assertive link between SABU and SAB and to recommend follow-up blood cultures.

Aim

We designed a retrospective quasi-experimental study to see if the change in microbiology comment wording had an effect on clinician behaviour. We hypothesized that this simple comment change to make a more assertive link between SABU and SAB would lead to an increase in follow-up blood culture orders.

Methodology

We used microbiology records to identify adult patients with urine cultures positive for Staphylococcus aureus at three acute-care hospitals in Hamilton, Ontario, Canada, for 1 year pre- and post-intervention. We recorded urine and blood culture results, timing, patient demographics, and in-hospital mortality.

Results

A total of 243 adult patients with urine cultures with S. aureus were identified for inclusion. The primary outcome was met, as there was a significant increase in blood culture orders between the pre-intervention and post-intervention groups (66.9 % vs 80.4 %). This difference was mainly driven by an increase for emergency department and urgent care patients (30.6 % vs 63.6 %). The inpatient group had a high baseline rate of blood culture orders that did not change significantly (80.0 % vs 84.7 %). There was no significant change in detection of SAB (23.5 % vs 32.7 %) or inpatient mortality (18.0 % vs 24.7 %).

Conclusion

Our study shows that a simple, purposeful comment appended to urine cultures with S. aureus leads to a significant increase in follow-up blood culture orders.

A Narrative Review on the Role of Staphylococcus aureus Bacteriuria in S. aureus Bacteremia

Staphylococcus aureus bacteriuria (SABU) can occur in patients with S. aureus bacteremia (SAB). However, little is known on the (molecular) pathomechanisms of the renal passage of S. aureus. This review discusses the epidemiology and pathogenesis of SABU in patients with SAB and identifies knowledge gaps. The literature search was restricted to the English language. The prevalence of SABU in patients with SAB is 7.8%-39% depending on the study design. The main risk factor for SABU is urinary tract catheterization. SABU in SAB patients is associated with increased mortality. Given present evidence, hematogenous seeding-as seen in animal models-and the development of micro-abscesses best describe the translocation of S. aureus from blood to urine. Virulence factors that might be involved are adhesion factors, sortase A, and coagulase, among others. Other potential routes of bacterial translocation (eg, transcytosis, paracytosis, translocation via "Trojan horses") were identified as knowledge gaps.

Characteristics and Outcomes of Staphylococcus aureus Bloodstream Infection Originating From the Urinary Tract: A Multicenter Cohort Study

Background

Staphylococcus aureus bloodstream infection (SABSI) arising from a urinary tract source (UTS) is poorly understood.

Methods

We conducted a retrospective analysis in 3 major teaching hospitals in Spain of prospectively collected data of hospitalized patients with SABSI. SABSI-UTS was diagnosed in patients with urinary tract symptoms and/or signs, no evidence of an extra-urinary source of infection, and a urinary S. aureus count of ≥10⁵ cfu/mL. Susceptibility of S. aureus strains and patient mortality were compared between SABSI from UTS (SABSI-UTS) and other sources (SABSI-other).

Results

Of 4181 episodes of SABSI, we identified 132 (3.16%) cases of SABSI-UTS that occurred predominantly in patients who were male, had high Charlson comorbidity scores, were dependent for daily life activities, and who had undergone urinary catheterization and/or urinary manipulation before the infection. SABSI-UTS was more often caused by MRSA strains compared with SABSI-other (40.9% vs 17.5%; P < .001). Patients with SABSI-UTS caused by MRSA more often received inadequate empirical treatment compared with those caused by susceptible strains (59.7% vs 23.1%; P < .001). The 30-day case fatality rate was lower in patients with SABSI-UTS than in those with SABSI-other (14.4% vs 23.8%; P = .02). Factors independently associated with mortality were dependence for daily activities (aOR, 3.877; 95% CI, 1.08–13.8; P = .037) and persistent bacteremia (aOR, 7.88; 95% CI, 1.57–39.46; P = .012).

Conclusions

SABSI-UTS occurs predominantly in patients with severe underlying conditions and in those who have undergone urinary tract manipulation. Moreover, it is frequently due to MRSA strains and causes significant mortality.

Indwelling catheterization, renal stones, and hydronephrosis are risk factors for symptomatic Staphylococcus aureus-related urinary tract infection

PURPOSE

Staphylococcus aureus is a relatively uncommon causative agent of urinary tract infection (UTI). However, the clinical features of S. aureus-related UTI are unclear. Thus, we aimed to clarify how patients with S. aureus bacteriuria develop UTI and determine the features and clinical risk factors of symptomatic S. aureus-related UTI.

METHODS

We performed a retrospective study of patients at the Hiroshima University Hospital for whom S. aureus had been isolated from urine culture from January 2010 to December 2017. The characteristics (age, sex, body mass index, indwelling catheterization, renal stones, hydronephrosis, anticancer drug use, diabetes mellitus, steroid use, serum albumin, antibiotic use in the past 1 month, estimated glomerular filtration rate, benign prostate hyperplasia, and neurogenic bladder) of patients with UTI and those without UTI were compared, and the risk factors for S. aureus-related UTI were identified by multiple logistic regression model.

RESULTS

A total of 286 patients with S. aureus bacteriuria were analyzed; 33 patients developed UTI. The causative pathogens were methicillin-sensitive S. aureus and methicillin-resistant S. aureus (MRSA) in 14 and 19 patients, respectively, who developed UTI. This study demonstrated that indwelling catheterization, hydronephrosis, and renal stones are significantly associated with S. aureus-related UTI (p = 0.01, odds ratio = 3.1; and p < 0.01, odds ratio = 7.0; and p = 0.02, odds ratio = 1.2; respectively) and hypoalbuminemia in MRSA-related UTI (p < 0.01).

CONCLUSION

Paying attention to risk factors, specifically indwelling catheterization, renal stones, and hydronephrosis, will be an effective strategy for prevention of S. aureus-related UTI with persistent staphylococcal bacteriuria.

Staphylococcus Aureus Bacteriuria as a Predictor of In-Hospital Mortality in Patients with Staphylococcus Aureus Bacteremia. Results of a Retrospective Cohort Study

Staphylococcus aureus bloodstream infection (SA-BSI) is an infection with increasing morbidity and mortality. Concomitant Staphylococcus aureus bacteriuria (SABU) frequently occurs in patients with SA-BSI. It is considered as either a sign of exacerbation of SA-BSI or a primary source in terms of urosepsis. The clinical implications are still under investigation. In this study, we investigated the role of SABU in patients with SA-BSI and its effect on the patients' mortality. We performed a retrospective cohort study that included all patients in our university hospital (Charité Universitätsmedizin Berlin) between 1 January 2014 and 31 March 2017. We included all patients with positive blood cultures for Staphylococcus aureus who had a urine culture 48 h before or after the first positive blood culture. We identified cases while using the microbiology database and collected additional demographic and clinical parameters, retrospectively, from patient files and charts. We conducted univariate analyses and multivariable Cox regression analysis to evaluate the risk factors for in-hospital mortality. 202 patients met the eligibility criteria. Overall, 55 patients (27.5%) died during their hospital stay. Cox regression showed SABU (OR 2.3), Pitt Bacteremia Score (OR 1.2), as well as moderate to severe liver disease (OR 2.1) to be independent risk factors for in-hospital mortality. Our data indicates that SABU in patients with concurrent SA-BSI is a prognostic marker for in-hospital death. Further studies are needed for evaluating implications for therapeutic optimization.

Community-acquired Staphylococcus aureus bacteriuria: a warning microbiological marker for infective endocarditis?

Background

Urinary tract infection (UTI) is frequently diagnosed in the Emergency Department (ED). Staphylococcus aureus (SA) is an uncommon isolate in urine cultures (0.5–6% of positive urine cultures), except in patients with risk factors for urinary tract colonization. In the absence of risk factors, community-acquired SA bacteriuria may be related to deep-seated SA infection including infective endocarditis. We hypothesized that SA bacteriuria could be a warning microbiological marker of unsuspected infective endocarditis in the ED.

Methods

This is a retrospective chart review of consecutive adult patients between December 2005 and February 2018. All patients admitted in the ED with both SA bacteriuria (10⁴ CFU/ml SA isolated from a single urine sample) and SA bacteremia, without risk factors for UT colonization (i.e., < 1 month UT surgery, UT catheterization) were analyzed. Diagnosis of infective endocarditis was based on the Duke criteria.

Results

During the study period, 27 patients (18 men; median age: 61 [IQR: 52–73] years) were diagnosed with community-acquired SA bacteriuria and had subsequently documented bacteremia and SA infective endocarditis. Only 5 patients (18%) had symptoms related to UT infection. Median delay between ED admission and SA bacteriuria identification was significantly shorter than that between ED admission and the diagnosis of infective endocarditis (1.4 ± 0.8 vs. 4.3 ± 4.2 days: p = 0.01). Mitral and aortic valves were most frequently involved by infective endocarditis (93%). Mortality on day 60 reached 56%.

Conclusions

This study suggests that community-acquired SA bacteriuria should warn the emergency physician about a potentially associated left-sided infective endocarditis in ED patients without risk factors for UT colonization.