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

The NLRP3 Inflammasome Is Dispensable in Methicillin-Resistant Staphylococcus aureus Urinary Tract Infection

The NLRP3 inflammasome is a cytoplasmic complex that senses molecular patterns from pathogens or damaged cells to trigger an innate immune defense response marked by the production of proinflammatory cytokines IL-1β and IL-18 and an inflammatory death called pyroptosis. The NLRP3 inflammasome is activated in the urinary tract by a variety of infectious and non-infectious insults. In this study, we investigated the role of the NLRP3 inflammasome by comparing the pathophysiology of methicillin-resistant Staphylococcus aureus (MRSA) ascending UTI in wild-type (WT) and Nlrp3-/- mice. The difference in the bacterial burden detected in the urinary tracts of MRSA-infected WT and Nlrp3-/- was not statistically significant at 6, 24, and 72 h post-infection (hpi). The levels of pro-inflammatory cytokines and chemokines as well as the numbers of granulocytes recruited to bladder and kidney tissues at 24 hpi were also similar between Nlrp3-/- and WT mice. The histopathological analysis of MRSA-infected bladder and kidney sections from Nlrp3-/- and WT mice showed similar inflammation. Overall, these results suggest that MRSA-induced urinary NLRP3 activity does not play a role in the pathophysiology of the ascending UTI.

Staphylococcus aureus Orbital Abscess With Impending Compressive Optic Neuropathy in an Immunocompetent Individual With Subclinical Bacteriuria: A Case Report

This is a case of an orbital abscess evidenced radiologically in a 41-year-old female with no comorbidities. She was healthy and had no history of trauma or infection of the adjacent structures. She denied having symptoms of upper or lower respiratory and urinary tract infections. The decision for surgical drainage was made following a slow response to antimicrobial agents after 24 hours, a progressive painful erythematous eyelid swelling, and further deterioration of vision. Her clinical condition and visual acuity improved following cutaneous incision and drainage. Culture and sensitivity results for urine and orbital abscess were positive for Staphylococcus (S.) aureus. The patient regained full visual recovery without any sequelae. In conclusion, an orbital abscess is a blinding and life-threatening condition that rarely occurs in immunocompetent individuals and uncommonly arises from distant sources. A high index of suspicion, early institution of appropriate diagnostic imaging, and aggressive medical and surgical treatment are necessary for a favorable visual outcome in orbital abscess cases.

Defining the Roles of Pyruvate Oxidation, TCA Cycle, and Mannitol Metabolism in Methicillin-Resistant Staphylococcus aureus Catheter-Associated Urinary Tract Infection

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of complicated urinary tract infection (UTI) associated with the use of indwelling urinary catheters. Previous reports have revealed host and pathogen effectors critical for MRSA uropathogenesis. Here, we sought to determine the significance of specific metabolic pathways during MRSA UTI. First, we identified four mutants from the Nebraska transposon mutant library in the MRSA JE2 background that grew normally in rich medium but displayed significantly reduced growth in pooled human urine (HU). This prompted us to transduce the uropathogenic MRSA 1369 strain with the transposon mutants in sucD and fumC (tricarboxylic acid [TCA] cycle), mtlD (mannitol metabolism), and lpdA (pyruvate oxidation). Notably, sucD, fumC, and mtlD were also significantly upregulated in the MRSA 1369 strain upon exposure to HU. Compared to the WT, the MRSA 1369 lpdA mutant was significantly defective for (i) growth in HU, and (ii) colonization of the urinary tract and dissemination to the kidneys and the spleen in the mouse model of catheter-associated UTI (CAUTI), which may be attributed to its increased membrane hydrophobicity and higher susceptibility to killing by human blood. In contrast to their counterparts in the JE2 background, the sucD, fumC, and mtlD mutants in the MRSA 1369 background grew normally in HU; however, they displayed significant fitness defects in the CAUTI mouse model. Overall, identification of novel metabolic pathways important for the urinary fitness and survival of MRSA can be used for the development of novel therapeutics. IMPORTANCE While Staphylococcus aureus has historically not been considered a uropathogen, S. aureus urinary tract infection (UTI) is clinically significant in certain patient populations, including those with chronic indwelling urinary catheters. Moreover, most S. aureus strains causing catheter-associated UTI (CAUTI) are methicillin-resistant S. aureus (MRSA). MRSA is difficult to treat due to limited treatment options and the potential to deteriorate into life-threatening bacteremia, urosepsis, and shock. In this study, we found that pathways involved in pyruvate oxidation, TCA cycle, and mannitol metabolism are important for MRSA fitness and survival in the urinary tract. Improved understanding of the metabolic needs of MRSA in the urinary tract may help us develop novel inhibitors of MRSA metabolism that can be used to treat MRSA-CAUTI more effectively.

Implementation of an asymptomatic bacteriuria assessment protocol for patients discharged from the emergency department

Objective

We evaluated the impact of an asymptomatic bacteriuria (ASB) assessment protocol on the number of antibiotics prescribed for ASB after discharge from the emergency department (ED).

Design

Single-center, before-and-after, retrospective cohort study.

Setting

The study was conducted at a large community health system in North Carolina.

Patients

Eligible patients were discharged from an ED without an antibiotic prescription and had a positive urine culture result after discharge from May through July 2021 (preimplementation group) and October through December 2021 (postimplementation group).

Methods

Patient records were reviewed to determine the number of antibiotic prescriptions for ASB on follow-up call before and after implementation of an ASB assessment protocol. Secondary outcomes included 30-day admissions, 30-day ED visits, 30-day UTI-related encounters, and projected antibiotic days of therapy.

Results

The study included 263 patients: 147 in the preimplementation group and 116 in the postimplementation group). There were significantly fewer antibiotic prescriptions for ASB in the postimplementation group (50% vs 87%; P < .0001). There were no differences in the incidence of 30-day admissions (7% vs 8%; P = .9761), 30-day ED visits (14% vs 16%; P = .7805), or 30-day UTI-related encounters (0% vs 0%, NA).

Conclusions

Implementation of an ASB assessment protocol for patients discharged from the ED significantly reduced the number of antibiotic prescriptions for ASB on follow-up call without an increase in 30-day admissions, ED visits, or UTI-related encounters.

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.

Transiently silent acquired antimicrobial resistance: an emerging challenge in susceptibility testing

Acquisition and expression of antimicrobial resistance (AMR) mechanisms in bacteria are often associated with a fitness cost. Thus, evolutionary adaptation and fitness cost compensation may support the advance of subpopulations with a silent resistance phenotype when the antibiotic selection pressure is absent. However, reports are emerging on the transient nature of silent acquired AMR, describing genetic alterations that can change the expression of these determinants to a clinically relevant level of resistance, and the association with breakthrough infections causing treatment failures. This phenomenon of transiently silent acquired AMR (tsaAMR) is likely to increase, considering the overall expansion of acquired AMR in bacterial pathogens. Moreover, the augmented use of genotypic methods in combination with conventional phenotypic antimicrobial susceptibility testing (AST) will increasingly enable the detection of genotype and phenotype discrepancy. This review defines tsaAMR as acquired antimicrobial resistance genes with a corresponding phenotype within the wild-type distribution or below the clinical breakpoint for susceptibility for which genetic alterations can mediate expression to a clinically relevant level of resistance. References to in vivo resistance development and therapeutic failures caused by selected resistant subpopulations of tsaAMR in Gram-positive and Gram-negative pathogens are given. We also describe the underlying molecular mechanisms, including alterations in the expression, reading frame or copy number of AMR determinants, and discuss the clinical relevance concerning challenges for conventional AST.

A retrospective analysis of blood culture-negative endocarditis at a tertiary care centre in Switzerland

AIMS OF THE STUDY

Numerous studies from different countries have contributed to an improved understanding of blood culture-negative infective endocarditis. However, little is known about its epidemiology and microbiology in Switzerland. We aimed to assess the epidemiology and microbiology of blood culture-negative endocarditis at the University Hospital Zurich, Switzerland.

METHODS

We screened all patients hospitalised between 1997 and 2020 with possible or definite endocarditis at our institution. Thereof, we identified all cases with blood culture-negative endocarditis and retrospectively retrieved patient characteristics, microbiological, histopathological, radiographic and surgical data from medical records.

RESULTS

Among 861 patients screened, 66 (7.7%) cases of blood culture-negative endocarditis were identified. Thereof, 31 cases could be microbiologically documented or not documented (n = 30), and in five cases a non-infectious aetiology was confirmed. Endocarditis predominantly affected men (77%) and the left heart (79%); predisposing factors were prosthetic valves (42%), congenital heart disease (35%) and prior endocarditis (14%). The most common reasons for negative blood cultures were antibiotic treatment prior to blood culture sampling (35%), fastidious and slow growing microorganisms (30%) and definite non-infective endocarditis (8%). Coxiella burnetii and Bartonella spp. were the most common fastidious bacteria identified. In addition to serology, identification of causative microorganisms was possible by microbiological and/or histopathological analysis of tissue samples, of which polymerase chain reaction testing (PCR) of the 16S ribosomal RNA proved to be most successful.

CONCLUSIONS

The present study provides a detailed analysis of blood culture-negative endocarditis over a time span of more than 20 years in Zurich, Switzerland. Antibiotic treatment prior to blood collection, and fastidious and slow growing organisms were identified as main reasons for sterile blood cultures. Typical culture-negative bacteria were mainly found by PCR and/or culture of tissue samples.

Staphylococcus aureus adhesion to the host

Staphylococcus aureus is a pathobiont capable of colonizing and infecting most tissues within the human body, resulting in a multitude of different clinical outcomes. Adhesion of S. aureus to the host is crucial for both host colonization and the establishment of infections. Underlying the pathogen's success is a complex and diverse arsenal of adhesins. In this review, we discuss the different classes of adhesins, including a consideration of the various adhesion sites throughout the body and the clinical outcomes of each infection type. The development of therapeutics targeting the S. aureus host-pathogen interaction is a relatively understudied area. Due to the increasing global threat of antimicrobial resistance, it is crucial that innovative and alternative approaches are considered. Neutralizing virulence factors, through the development of antivirulence agents, could reduce bacterial pathogenicity and the ever-increasing burden of S. aureus infections. This review provides insight into potentially efficacious adhesion-associated targets for the development of novel decolonizing and antivirulence strategies.

Urinary tract infection in a human male patient with Staphylococcus pseudintermedius transmission from the family dog

Staphylococcus pseudintermedius is increasingly recognized as a human pathogen. We report the first case of an urinary tract infection in a male patient with this organism.

Trends in Incidence and Outcomes of Hospitalizations for Urinary Tract Infection among Older People in Spain (2001-2018)

(1) Background: To assess time trends in the incidence and in-hospital outcomes of urinary tract infection (UTI) in older people (≥65 years) in Spain (2001–2018) according to sex and to identify the factors independently associated with in-hospital mortality (IHM). (2) Methods: Using the Spanish National Hospital Database, we analyzed comorbidity, procedures, diagnosis, isolated microorganisms, and outcomes. (3) Results: We included 583,693 admissions (56.76% women). In both sexes, the incidence increased with age over time (p < 0.001). In men and women, the highest IHM was found among the oldest patients (>84 years) with values of 9.16% and 8.6%, respectively. The prevalence of bacteremia increased from 4.61% to 4.98% from 2001 to 2018 (p < 0.001) and sepsis decreased from 3.16% to 1.69% (p < 0.001). The risk of dying increased with age (>84 years) (OR 3.63; 95% CI 3.5–3.78) and with almost all comorbidities. Urinary catheter was a risk factor for women (OR 1.1; 95% CI 1.02–1.18) and protective for men (OR 0.71; 95% CI 0.66–0.76). Isolation of Staphylococcus aureus increased the risk of IHM by 40% among men (OR 1.4; 95% CI 1.28–1.53). After adjusting for confounders, IHM decreased over time. (4) Conclusions: The incidence of UTIs was higher in older patients and increased over time; however, IHM decreased during the same period. Female sex, age, comorbidities, sepsis, and a Staphylococcus aureus isolation increased risk of IHM.

Occurrence and Phenotypic Characterization of Multidrug-Resistant Bacterial Pathogens Isolated from Patients in a Public Hospital in Mogadishu, Somalia

Purpose

This study reports a cross-sectional investigation to determine the antimicrobial resistance pattern of the common bacterial contaminants isolated from hospitalized patients in Mogadishu, Somalia.

Materials and Methods

A total of 328 clinical samples comprising urine, blood, vaginal swab, pus aspirates, and stool were collected from a public hospital located in Mogadishu the capital city of Somalia between October 2019 to March 2020. The isolation and biochemical characterization of the bacterial isolates were performed using the conventional culture and biochemical assay tests. Similarly, antimicrobial susceptibility was determined using the Kirby–Bauer disk diffusion.

Results

A total of 275 pathogenic bacteria that include Staphylococcus aureus, Escherichia coli, Pseudomonas aeroginosa, Proteus vulgare, Klebsiella pneumonia, and Salmonella spp. were detected with an overall detection rate of 78.4% (257/328). Among the bacterial pathogens isolated from clinical specimens, 152 (46.3%) were Staphylococcus aureus, 60 (18.3%) were E. coli, 10 (3.1%) Proteus vulgaris, 6 (1.8%) Klebsiella pneumonia, and 1 (0.3%) isolate was found to be Salmonella sp. The antimicrobial susceptibility assay revealed variable resistance pattern with clindamycin (40%), ampicillin (27%), vancomycin (26%), levofloxacin (23%), amoxicillin (20%), ciprofloxacin (18%) and nitrofurantoin (12%) showing the highest rate of resistance. Moreover, evaluation of multidrug resistance showed that Staphylococcus aureus had the highest multidrug resistance rate, with 19 isolates showing resistance to more than two drugs, followed by E. coli with three isolates. In contrast, each of Proteus vulgare, Salmonella sp. and Klebsiella pneumonia had one isolate each that exhibited multidrug resistance characteristics.

Conclusion

The findings of this study showed the occurrence of a number antimicrobial-resistant bacterial pathogens whose prevalence varies with age and sex. Therefore, there is a need for comprehensive antimicrobial profiling of bacterial isolates during the management of patients in the hospital.

Antimicrobial activity of medicinal plants used for urinary tract infections in pastoralist community in Ethiopia

BACKGROUND

Medicinal plants have wide medicament application used to prevent and management of many ailments. These plants are used for primary health care in pastoralist communities who are deprived of modern medical care. They possess extensive therapeutics bioactive coupled with varied chemical structures. However, scientific validation of efficacy and safety of plants used to treat the urinary tract infections haven't been fully exploited. The aim of this study was to evaluate antimicrobial activity and screening phytochemicals of medicinal plants used to treat urinary tract infections.

METHODS

In-vitro experimental study was carried out to evaluate the antimicrobial effect and screening phytochemical of Rumex abyssinicus, Cucumis pustulatus, Discopodium penninervium, Lippia adoensis, Euphorbia depauperata, and Cirsium englerianum. Against drug resistance microbes. 80% methanol was used for extraction of the plant parts. The susceptibility tests were investigated using disc diffusion and broth micro-dilution methods.

RESULTS

The majority of tested extracts showed antimicrobial activity on two or more drug-resistant bacteria with MIC value (1.0-128.0 μg/ml) and 9-27 mm inhibition zone in diameter. Extracts obtained from C.englerianum and E. depauperate showed more potent antibacterial activity on MRSA and Enterococcus faecalis with IZ 25 and 27 mm respectively. E. coli and K. pneumoniae were inhibited by those extracts with IZ ranging 9-25 mm and 11-27 mm respectively. E.faecalis and K. pneumoniae were more susceptible bacteria to the respective extracts. R. abyssinicus showed promising antifungal effect with had 21 mm IZ and MIC range 16-32 μg/ml on C.albicans. Alkaloids, flavonoids, phenolic and terpenoid were common phytochemical characterized in majority of screened plants.

CONCLUSION

Tested extracts exhibited significant antibacterial and antifungal activity. Hence, further structural elucidation of bioactive that inhibited the growth of microbes aforementioned plants may be used as precursors for the synthesis of new antibiotics in the future.

Time Trends in Spain from 2001 to 2018 in the Incidence and Outcomes of Hospitalization for Urinary Tract Infections in Patients with Type 2 Diabetes Mellitus

We aim to examine the incidences, clinical characteristics, and in-hospital outcomes of type 2 diabetes (T2DM) patients hospitalized with urinary tract infections (UTIs) in Spain and to identify the factors associated with in-hospital mortality (IHM). A retrospective observational study was carried out with a sample that included all adult patients who were hospitalized for UTIs between 2001 and 2018 and collected in the Spanish National Health System Hospital Discharge Database. We identified 850,276 patients with UTIs (25.49% with T2DM). The incidence of UTIs increased in patients with and without diabetes from 290.76 and 74.79 cases per 100,000 inhabitants in the period from year 2001 to year 2003 to 568.45 and 144.0 in the period from 2016 to 2018, respectively (p < 0.001). Adjusted incidence of UTIs was higher in T2DM patients (incidence rate ratio (IRR) 4.36; 95% CI 4.35–4.39). The multivariable analysis showed a significant reduction in the IHM over time for men and women with T2DM. In T2DM, patients’ higher IHM was associated with older age, comorbidities, and Staphylococcus aureus isolation. Women with T2DM had a higher risk of dying than men. The risk of IHM with an episode of UTIs was independent of the presence of T2DM (odds ratio (OR) 0.97; 95% CI 0.91–1.01). We conclude that the incidence of UTIs was over four times higher in T2DM than nondiabetic patients and has increased over time.

The Impact of COPD in Trends of Urinary Tract Infection Hospitalizations in Spain, 2001-2018: A Population-Based Study Using Administrative Data

(1) Background: To examine trends in incidence and outcomes of urinary tract infections (UTIs) among men and women with or without chronic obstructive pulmonary disease (COPD), and to identify the predictors for in-hospital mortality (IHM). (2) Methods: We included patients (aged ≥40 years) who were hospitalized with UTIs between 2001 and 2018. Data were collected from the Spanish National Hospital Discharge Database. (3) Results: We identified 748,458 UTI hospitalizations, 6.53% with COPD. The UTIs incidence increased over time. It was 1.55 times higher among men COPD patients than among non-COPD men (incidence rate ratio (IRR) 1.55; 95% CI 1.53-1.56). The opposite happened in women with COPD compared to non-COPD women (IRR 0.30; 95% CI 0.28-0.32). IHM was higher in men with COPD than non-COPD men (5.58% vs. 4.47%; p < 0.001) and the same happened in women (5.62% vs. 4.92%; p < 0.001). The risk of dying increased with age and comorbidity, but the urinary catheter was a protective factor among men (OR 0.75; 95% CI 0.64-0.89). Multivariable analysis showed a significant reduction in the IHM over time for men and women with COPD. Suffering from COPD only increased the risk of IHM among men (OR 1.07; 95% CI 1.01-1.13). (4) Conclusions: The incidence of UTIs increased over time. Suffering COPD increased the risk of IHM among men, but not among women.

A diagnostic algorithm for detection of urinary tract infections in hospitalized patients with bacteriuria: The "Triple F" approach supported by Procalcitonin and paired blood and urine cultures

For acute medicine physicians, distinguishing between asymptomatic bacteriuria (ABU) and clinically relevant urinary tract infections (UTI) is challenging, resulting in overtreatment of ABU and under-recognition of urinary-source bacteraemia without genitourinary symptoms (USB). We conducted a retrospective analysis of ED encounters in a university hospital between October 2013 and September 2018 who met the following inclusion criteria: Suspected UTI with simultaneous collection of paired urinary cultures and blood cultures (PUB) and determination of Procalcitonin (PCT). We sought to develop a simple algorithm based on clinical signs and PCT for the management of suspected UTI. Individual patient presentations were retrospectively evaluated by a clinical "triple F" algorithm (F1 ="fever", F2 ="failure", F3 ="focus") supported by PCT and PUB. We identified 183 ED patients meeting the inclusion criteria. We introduced the term UTI with systemic involvement (SUTI) with three degrees of diagnostic certainty: bacteremic UTI (24.0%; 44/183), probable SUTI (14.2%; 26/183) and possible SUTI (27.9%; 51/183). In bacteremic UTI, half of patients (54.5%; 24/44) presented without genitourinary symptoms. Discordant bacteraemia was diagnosed in 16 patients (24.6% of all bacteremic patients). An alternative focus was identified in 67 patients, five patients presented with S. aureus bacteremia. 62 patients were diagnosed with possible UTI (n = 20) or ABU (n = 42). Using the proposed "triple F" algorithm, dichotomised PCT of < 0.25 pg/ml had a negative predictive value of 88.7% and 96.2% for bacteraemia und accordant bacteraemia respectively. The application of the algorithm to our cohort could have resulted in 33.3% reduction of BCs. Using the diagnostic categories "possible" or "probable" SUTI as a trigger for initiation of antimicrobial treatment would have reduced or streamlined antimicrobial use in 30.6% and 58.5% of cases, respectively. In conclusion, the "3F" algorithm supported by PCT and PUB is a promising diagnostic and antimicrobial stewardship tool.