Direct molecular versus culture-based assessment of Gram-positive cocci in biopsies of patients with major abscesses and diabetic foot infections

Microbiological profiles in periprosthetic joint infections after total knee arthroplasty: a comparative analysis of diabetic and non-diabetic patients

AIM OF THE STUDY

The purpose of this study is to conduct a comparative analysis of the microbiological profiles in periprosthetic joint infections (PJIs) after total knee arthroplasty (TKA) between diabetic and non-diabetic patients. The study aims to address what are the variations in microbial colonization and infection patterns between diabetic and non-diabetic patients undergoing total knee arthroplasty.

METHODS

A retrospective analysis of 2,569 culture-positive cases of PJIs post-TKA was conducted, comparing outcomes between diabetic (n = 321) and non-diabetic (n = 2,248) patients. Demographic, clinical, and microbiological data were collected and analyzed using descriptive statistics, chi-squared tests, logistic regression, and other statistical tests.

RESULTS

Diabetic patients exhibited distinct microbial colonization patterns, with a higher prevalence of pathogens such as Staphylococcus aureus (p = 0.033), Pseudomonas aeruginosa (p < 0.001), Streptococcus spp. (Streptococcus agalactiae and Streptococcus dysgalactiae; p = 0.010, 0.016 respectively), Candida spp. (p = 0.010), and Corynebacterium spp. (p = 0.024). Additionally, diabetic patients were at increased risk of polymicrobial infections. Comorbidities associated with diabetes, including chronic pulmonary disease, renal insufficiency, and peripheral artery disease, were significantly more prevalent in diabetic patients and further complicated PJI outcomes.

CONCLUSION

This study underscores the importance of tailored perioperative antimicrobial strategies and vigilant infection control measures in diabetic patients undergoing TKA. Understanding the differential microbial profiles and associated comorbidities can inform targeted interventions to mitigate the risk of PJIs and improve outcomes in this high-risk population. Further research is warranted to elucidate the underlying mechanisms and optimize management strategies for diabetic patients undergoing TKA.

Proportion of toxin and non-toxin virulence factors of Staphylococcus aureus isolates from diabetic foot infection: a systematic review and meta-analysis

BACKGROUND

Staphylococcus aureus isolates are the leading cause of diabetic foot infections (DFIs). Identification of specific virulence factors of S. aureus involved in the pathogenesis of DFIs may help control the infection more effectively. Since the most prevalent virulence factor genes are probably related to the DFI pathogenesis, the aim of this study is to evaluate the proportion of virulence factor genes of S. aureus isolates from DFIs.

MATERIALS AND METHODS

We conducted a systematic search of PubMed, Embase, Web of Science, and Scopus to identify all articles reporting the proportion of different types of virulence factors of S. aureus isolates from DFI samples.

RESULTS

Seventeen studies were eligible, in which 1062 S. aureus isolates were obtained from 1948 patients and 2131 DFI samples. Among the toxin virulence factors, hld 100.0% (95% CI: 97.0, 100.0%), hlg 88.0% (95% CI: 58.0, 100.0%), hla 80.0% (95% CI: 31.0, 100.0%), hlgv 79.0% (95% CI: 35.0, 100.0%) and luk-ED 72.0% (95% CI: 42.0, 95.0%) had the highest proportion respectively. Among the genes associated with biofilm formation, both icaA and icaD had the highest proportion 100.0% (95% CI: 95.6, 100.0%).

CONCLUSION

The results of the present study showed that among the toxin virulence factors, hemolysins (hld, hlg, hla, hlgv) and luk-ED and among the non-toxin virulence factors, icaA and icaD have the greatest proportion in S. aureus isolates from DFIs. These prevalent genes may have the potential to evaluate as virulence factors involved in DFI pathogenesis. Finding these probable virulence factor genes can help control diabetic foot infection more effectively via anti-virulence therapy or preparation of multi-epitope vaccines.

Prevalence and Predictors of Pseudomonas aeruginosa among Hospitalized Patients with Diabetic Foot Infections

Background

Diabetic foot infections (DFIs) are commonly associated with antibiotic overuse. Empiric DFI treatment often includes coverage for Pseudomonas aeruginosa (PsA), but the frequency of PsA DFIs is poorly understood. The study objectives were to quantify the prevalence of and determine predictors for PsA DFIs.

Methods

This multicenter, retrospective cohort included hospitalized patients with DFI from 2013 through 2020 who were age ≥18 years; diabetes mellitus diagnosis; and DFI based on International Classification of Diseases, Tenth Revision coding, antibiotic treatment, and DFI culture with organism growth. Osteomyelitis was excluded. Patient characteristics were described and compared; the primary outcome was presence of PsA on DFI culture. Predictors of PsA DFI were identified using multivariable logistic regression.

Results

Two hundred ninety-two patients were included. The median age was 61 (interquartile range [IQR], 53–69) years; the majority were men (201 [69%]) and White (163 [56%]). The most commonly isolated organisms were methicillin-susceptible Staphylococcus aureus (35%) and streptococci (32%); 147 (54%) cultures were polymicrobial. Two hundred fifty-seven (88%) patients received empiric antibiotics active against PsA, but only 27 (9%) patients had PsA DFI. Immunocompromised status (adjusted odds ratio [aOR], 4.6 [95% confidence interval {CI}, 1.3–16.7]) and previous outpatient DFI antibiotic treatment failure (aOR, 4.8 [95% CI, 1.9–11.9]) were associated with PsA DFI.

Conclusions

PsA DFI is uncommon, but most patients receive empiric antipseudomonal antibiotics. Empiric broad-spectrum antibiotics are warranted given the frequency of mixed infections, but patient-specific risk factors should be considered before adding antipseudomonal coverage.

Neutralizing Staphylococcus aureus Virulence with AZD6389, a Three mAb Combination, Accelerates Closure of a Diabetic Polymicrobial Wound

Nonhealing diabetic foot ulcers (DFU), a major complication of diabetes, are associated with high morbidity and mortality despite current standard of care. Since Staphylococcus aureus is the most common pathogen isolated from nonhealing and infected DFU, we hypothesized that S. aureus virulence factors would damage tissue, promote immune evasion and alter the microbiome, leading to bacterial persistence and delayed wound healing. In a diabetic mouse polymicrobial wound model with S. aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, we report a rapid bacterial proliferation, prolonged pro-inflammatory response and large necrotic lesions unclosed for up to 40 days. Treatment with AZD6389, a three-monoclonal antibody combination targeting S. aureus alpha toxin, 4 secreted leukotoxins, and fibrinogen binding cell-surface adhesin clumping factor A resulted in full skin re-epithelization 21 days after inoculation. By neutralizing multiple virulence factors, AZD6389 effectively blocked bacterial agglutination and S. aureus-mediated cell killing, abrogated S. aureus-mediated immune evasion and targeted the bacteria for opsonophagocytic killing. Neutralizing S. aureus virulence not only facilitated S. aureus clearance in lesions, but also reduced S. pyogenes and P. aeruginosa numbers, damaging inflammatory mediators and markers for neutrophil extracellular trap formation 14 days post initiation. Collectively, our data suggest that AZD6389 holds promise as an immunotherapeutic approach against DFU complications.

IMPORTANCE Diabetic foot ulcers (DFU) represent a major complication of diabetes and are associated with poor quality of life and increased morbidity and mortality despite standard of care. They have a complex pathogenesis starting with superficial skin lesions, which often progress to deeper tissue structures up to the bone and ultimately require limb amputation. The skin microbiome of diabetic patients has emerged as having an impact on DFU occurrence and chronicity. DFU are mostly polymicrobial, and the Gram-positive bacterium Staphylococcus aureus detected in more than 95% of cases. S. aureus possess a collection of virulence factors which participate in disease progression and may facilitate growth of other pathogens. Here we show in a diabetic mouse wound model that targeting some specific S. aureus virulence factors with a multimechanistic antibody combination accelerated wound closure and promoted full skin re-epithelization. This work opens promising new avenues for the treatment of DFU.

Diabetic Foot Ulcer Infections and Pseudomonas aeruginosa Biofilm Production During the COVID-19 Pandemic

During the different waves of the coronavirus (COVID-19) pandemic, there has been an increased incidence of diabetes mellitus and diabetic foot infections. Among gram-negative bacteria, Pseudomonas aeruginosa is the predominant causative agent for diabetic foot ulcer infections in low-resource countries. P. aeruginosa possesses a variety of virulence factors, including biofilm formation. Biofilm formation is an important benchmark characteristic in the pathophysiology of diabetic foot ulceration. The main objective of the current study was to identify the most commonly isolated organisms and their antibiotic susceptibility patterns in diabetic foot patients during the COVID-19 pandemic. We also determined the genes associated with bacterial persistence and biofilm formation in the predominantly isolated organism. Accordingly, 100 wound swab samples were collected from diabetic foot patients from different hospitals in Alexandria, Egypt. Through phenotypic detection of biofilm formation, 93% (40) of the 43 P. aeruginosa isolates examined were categorized as biofilm producers. Molecular detection of the biofilm-encoding genes among the 43 P. aeruginosa isolates was as follows: algD (100%), pelF (88%) and pslD (49.7%), and this highlights a need for biofilm formation inhibitors to prevent the persistence of bacterial pathogens, and thus achieve better clinical outcomes in diabetic foot ulcer infections.

Antimicrobial Susceptibility Testing and Phenotypic Detection of MRSA Isolated from Diabetic Foot Infection

Background

Diabetic foot infection (DFI) is a common and costly complication of diabetes that may be caused by various bacteria with multi-resistant genes. The aim of this study is to evaluate the efficacy of phenotypic methods for identification of methicillin-resistant Staphylococcus aureus (MRSA) with genotypic detection of MRSA-related genes.

Methods

In this cross-sectional study, swab samples were collected from patients with DFI from hospitals in Sulaimani/Iraq in April–July 2019. All the samples were processed for microbiological assessment and further MRSA phenotypic and genotypic testing.

Results

A total of 46 swab samples were collected from diabetic foot ulcers of 29 males and 17 females. Most samples (93.5%) showed positive growth, with higher proportions of monomicrobial (23; 53.5%) than mixed-bacterial infections (20; 46.5%) and S. aureus as the predominant pathogen. Conventional methods of MRSA detection, such as cefoxitin disc diffusion, can predict methicillin resistance in 45.8% of the cases. Real-time/conventional PCR showed that 41.6% of Staphylococcus aureus were positive for the mecA gene, while none of the isolates was positive for PVL.

Conclusion

Staphylococcus aureus was the predominant pathogen in DFI. Although cefoxitin and oxacillin disc diffusion methods can help in the prediction of MRSA, real-time PCR is a reliable method for MRSA detection and confirmation.

Microbial spectrum, antibiotic susceptibility profile, and biofilm formation of diabetic foot infections (2014-18): a retrospective multicenter analysis

This study identifies the risk factors, microbiological properties, antimicrobial susceptibility patterns, mortality, and clinical complications associated with organisms causing diabetic foot infections (DFIs) with or without antibiotic treatment using data from a retrospective multicenter surveillance. Specimens collected from different hospitals were cultured and the extended-spectrum β-lactamase (ESBL) excretion was estimated. The antibacterial susceptibility pattern and biofilm formation were completed along with the recommended standard methods. Overall, 792 diabetic foot patients (DFPs) were enrolled and a total of 1803 causative organisms were isolated. Polymicrobial infection was identified in 48.5% of the patients. The isolated Gram-positive pathogens (46.7%) were higher than Gram-negative (38.6%) or anaerobes (7.9%). The predominant pathogens were S. aureus (22.2%), methicillin-resistant S. aureus (7.7%), Enterococcus spp. (12.8%), Pseudomonas aeruginosa (9.4%), E. coli (7.9%), Klebsiella spp. (7.5%), Proteus mirabilis (8.9%), coagulase negative staphylococci (CoNS) (6.6%), anaerobic organisms (5.9%), and fungi (2.3%). Vancomycin and clindamycin exhibited no activity against Gram-positive bacteria. However, meropenem and imipenem displayed high activity against the Gram-negative isolates. Out of the 765 tested strains, 251 showed moderate (15.8%) to high (34%) level biofilm-producing phenotype. DFIs were widespread among the diabetic patients with different microbial etiology and the major organisms were aerobic organisms. Our findings may provide an insight into the development of appropriate therapeutic strategies for the management of DFIs.

Bacterial isolation and antibiotic susceptibility from diabetic foot ulcers in Kenya using microbiological tests and comparison with RT-PCR in detection of S. aureus and MRSA

OBJECTIVES

Diabetic foot ulcers (DFUs) often lead to hospital admissions, amputations and deaths; however, there is no up-to-date information on microbial isolates from DFUs and no mention of utilization of molecular techniques in Sub-Saharan Africa. We conducted a cross-sectional study among 83 adult patients at a tertiary hospital in Kenya over 12 months. The study aimed to isolate, identify bacteria, their antibiotic susceptibility patterns in active DFUs, and to compare standard microbiological methods versus a real-time PCR commercial kit in the detection of Staphylococcus aureus DNA and methicillin-resistant S. aureus (MRSA) DNA.

RESULTS

Eighty swabs (94%) were culture-positive; 29% were Gram-positive and 65% were Gram-negative. The main organisms isolated were S. aureus (16%), Escherichia coli (15%), Proteus mirabilis (11%), Klebsiella pneumoniae (7%) and Pseudomonas aeruginosa (7%). The bacterial isolates showed resistance to commonly used antibiotics such as ampicillin, amoxicillin, cefepime, ceftazidime, cefuroxime, clindamycin, erythromycin, piperacillin-tazobactam, tetracycline and trimethoprim-sulphamethoxazole (TMPSMX). Thirty-one percent of the S. aureus isolated and 40% of the Gram-negatives were multi-drug resistant organisms (MDROs). There was a high prevalence of nosocomial bacteria. MRSA were not identified using culture methods but were identified using PCR. PCR was more sensitive but less specific than culture-based methods to identify S. aureus.

Association of soft tissue infection in the extremity with glucose and lipid metabolism and inflammatory factors

Association of soft tissue infection in the extremity with glucose and lipid metabolism as well as inflammatory factors was investigated. One hundred and twenty-six patients with diabetes mellitus (DM) complicated with soft tissue infection in the lower extremity admitted and treated in Dongying People's Hospital from March 2016 to February 2017 were selected and divided into mild (n=46), moderate (n=43) and severe group (n=37) according to the severity of the soft tissue infection in the lower extremity. The glucose and lipid metabolism, inflammatory factors and influencing factors were compared among different groups of patients before treatment, and the changes in glucose and lipid metabolism as well as inflammatory factors were observed after treatment. Before treatment, the levels of free fatty acid (FFA), fasting plasma glucose (FPG), fasting insulin (FINS), vascular cell adhesion molecule-1 (VCAM-1), C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in mild group were remarkably lower than those in moderate and severe groups, while the serum adiponectin (APN) level was obviously higher (P<0.05). Logistic regression analysis indicated that FFA, FPG, FINS, APN, VCAM-1, CRP, TNF-α and IL-6 were risk factors influencing soft tissue infection in the extremity (P<0.05). After treatment, among the 126 patients, the levels of FFA, FPG, FINS, VCAM-1, CRP, TNF-α and IL-6 were decreased markedly, while the APN level was increased evidently (P<0.05). Compared with patients innon-toe/extremity amputation group, patients in toe/extremity amputation group had elevated levels of FFA, FPG, FINS, VCAM-1, CRP, TNF-α and IL-6 as well as declined APN level (P<0.05). Glucose and lipid metabolism and inflammatory factors are closely related to soft tissue infection in the extremity.

Bacterial distribution, changes of drug susceptibility and clinical characteristics in patients with diabetic foot infection

The present study aimed to investigate the bacterial distribution, changes in drug susceptibility and clinical characteristics in patients with diabetic foot infection (DFI). A retrospective analysis of 216 patients with DFI treated at Xinxiang Central Hospital between 2013 and 2016 was carried out to analyze the bacterial distribution, changes of susceptibility and clinical characteristics. A total of 262 pathogenic strains were isolated from 216 patients with DFI. Among them, 43.13% exhibited Gram-positive (G⁺) bacteria, 45.04% exhibited Gram-negative (G^-) bacteria and 11.83% was other. Between 2013 and 2016, the susceptibility of pathogenic bacteria to common antibacterial drugs showed a declining trend year by year. G⁺ bacteria had high susceptibility to vancomycin and acetazolamide; while G^- bacteria showed high susceptibility to dibekacin, panipenem and biapenem. The main clinical symptoms of the 216 patients included edema (98.61%), purulent secretions (62.96%) and lower extremity sepsis (58.80%). The top three complications of the 216 cases were lower extremity vascular disease (58.80%), peripheral neuropathy (39.81%) and kidney disease (26.39%). Logistic regression analysis showed that age [odds ratio (OR), 2.708; P=0.005], previous use of antibacterial drugs (OR, 3.816; P=0.007) and application of the third generation cephalosporins (OR, 3.014; P=0.008) were the independent risk factors of drug resistance in patients with DFI (P<0.05). There were numerous types of pathogens in patients with DFI, and all of them had certain drug resistance. The drug susceptibility was decreasing year by year. The pathogens and drug resistance in patients with DFI should be monitored to reduce the incidence of related complications and improve the prognosis of patients.

Staphylococcus aureus Toxins and Diabetic Foot Ulcers: Role in Pathogenesis and Interest in Diagnosis

Infection of foot ulcers is a common, often severe and costly complication in diabetes. Diabetic foot infections (DFI) are mainly polymicrobial, and Staphylococcus aureus is the most frequent pathogen isolated. The numerous virulence factors and toxins produced by S. aureus during an infection are well characterized. However, some particular features could be observed in DFI. The aim of this review is to describe the role of S. aureus in DFI and the implication of its toxins in the establishment of the infection. Studies on this issue have helped to distinguish two S. aureus populations in DFI: toxinogenic S. aureus strains (harboring exfoliatin-, EDIN-, PVL- or TSST-encoding genes) and non-toxinogenic strains. Toxinogenic strains are often present in infections with a more severe grade and systemic impact, whereas non-toxinogenic strains seem to remain localized in deep structures and bone involving diabetic foot osteomyelitis. Testing the virulence profile of bacteria seems to be a promising way to predict the behavior of S. aureus in the chronic wounds.

Bacteroides fragilis in biopsies of patients with major abscesses and diabetic foot infections: direct molecular versus culture-based detection

Direct determination by pathogen-specific real-time PCR assay for Bacteroides fragilis was compared to culture in major abscess and diabetic foot infection biopsy samples. Real-time PCR resulted in an increased detection rate of 12% for B. fragilis and could improve the detection of B. fragilis in clinical samples.