Culture-Negative Surgical Site Infections

Subcutaneous Lumbar Spine Index (SLSI) as a Risk Factor for Surgical Site Infection After Lumbar Fusion Surgery: A Retrospective Matched Case-Control Study

STUDY DESIGN

A retrospective matched case-control study.

OBJECTIVE

This study aims to investigate the value of Subcutaneous Lumbar Spine Index (SLSI) as a predictor of early surgical site infection (SSI) after lumbar intervertebral fusion surgery.

METHODS

A retrospective case-control study was performed on patients who underwent transforaminal lumbar interbody fusion (TLIF) from January 1, 2014 to December 31, 2019 in a single institution. Cases were defined as those who developed early SSI according to the US Center for Disease Control and Prevention criteria, and controls were matched from those patients without early SSI using the following matched criteria: gender, age, time of surgery and diabetes. Subcutaneous fat thickness (SFT) and SLSI were measured on preoperative MRI mid-sagittal T2 weighted images.

RESULTS

A total of 3615 patients who underwent TLIF were enrolled in this study. Thirty-three patients were included in early SSI, and sixty-six patients were selected as matched controls. Univariate analysis indicated that fusion levels (P = .007), operation time (P = .022), obesity (P = .013), SFT (P = .002) and SLSI (P = .001) were significantly associated with early SSI. Multiple logistic regression analysis revealed that multilevel fusion levels (P = .021), obesity (P = .035), a large SFT (P = .026) and a high SLSI (P = .012) were independent risk factors. Body mass index (BMI) and SLSI were moderately correlated (r2 = .55). ROC curve demonstrated that SLSI was more sensitive than SFT to predict the early SSI.

CONCLUSION

SLSI is a novel radiological risk factor for early SSI development and is a better indicator than SFT to predict early SSI risk after lumbar intervertebral fusion.

Development of an automated amplicon-based next-generation sequencing pipeline for rapid detection of bacteria and fungi directly from clinical specimens

The timely identification of microbial pathogens is essential to guide targeted antimicrobial therapy and ultimately, successful treatment of an infection. However, the yield of standard microbiology testing (SMT) is directly related to the duration of antecedent antimicrobial therapy as SMT culture methods are dependent on the recovery of viable organisms, the fastidious nature of certain pathogens, and other pre-analytic factors. In the last decade, metagenomic next-generation sequencing (mNGS) has been successfully utilized as a diagnostic tool for various applications within the clinical laboratory. However, mNGS is resource, time, and labor-intensive-requiring extensive laborious preliminary benchwork, followed by complex bioinformatic analysis. We aimed to address these shortcomings by developing a largely Automated targeted Metagenomic next-generation sequencing (tmNGS) PipeLine for rapId inFectIous disEase Diagnosis (AMPLIFIED) to detect bacteria and fungi directly from clinical specimens. Therefore, AMPLIFIED may serve as an adjunctive approach to complement SMT. This tmNGS pipeline requires less than 1 hour of hands-on time before sequencing and less than 2 hours of total processing time, including bioinformatic analysis. We performed tmNGS on 50 clinical specimens with concomitant cultures to assess feasibility and performance in the hospital laboratory. Of the 50 specimens, 34 (68%) were from true clinical infections. Specimens from cases of true infection were more often tmNGS positive compared to those from the non-infected group (82.4% vs 43.8%, respectively, P = 0.0087). Overall, the clinical sensitivity of AMPLIFIED was 54.6% with 85.7% specificity, equating to 70.6% and 75% negative and positive predictive values, respectively. AMPLIFIED represents a rapid supplementary approach to SMT; the typical time from specimen receipt to identification of potential pathogens by AMPLIFIED is roughly 24 hours which is markedly faster than the days, weeks, and months required to recover bacterial, fungal, and mycobacterial pathogens by culture, respectively.

IMPORTANCE

To our knowledge, this represents the first application of an automated sequencing and bioinformatics pipeline in an exclusively pediatric population. Next-generation sequencing is time-consuming, labor-intensive, and requires experienced personnel; perhaps contributing to hesitancy among clinical laboratories to adopt such a test. Here, we report a strong case for use by removing these barriers through near-total automation of our sequencing pipeline.

Mapping prognostic factors for globe survival in panophthalmitis using logistic regression and Cox proportional hazard models: A retrospective study

Purpose

The aim of this study was to report the outcomes of panophthalmitis and to identify factors significantly affecting globe survival in the disease.

Methods

This was a retrospective study on patients with panophthalmitis in a tertiary hospital between January 1, 2017, and December 31, 2019. The demographics, treatment details, culture results, and final outcomes were recorded. Logistic regression and Cox proportional hazards (CPH) were calculated to identify variables associated with globe loss. A P < 0.05 was considered significant.

Results

Eighty-five eyes of 85 patients (31 culture positive) were eligible for review. The mean age of the participants was 55.21 ± 20.17 years with a male-to-female ratio of 2.04:1. Corneal ulcer (38.82%; n = 33) and open globe injuries (OGIs) (38.82%; n = 33) were the most common etiologies. Pseudomonas aeruginosa (n = 10; 11.76%) was the most common isolate. The mean duration of hospital stay was 7.58 ± 2.32 days. Overall, 44 (51.76%) globes could be salvaged. The need for evisceration (P = 0.901) and hospital stays (P = 0.095) were similar for culture-positive and -negative cohorts. The unadjusted logistic regression and CPH models showed that culture sterility did not affect globe survival [OR = 1.210 (0.501-2.950), P = 0.668; HR = 1.176 (0.617-2.243), P = 0.623]. The adjusted logistic regression and the CPH models showed that corneal ulcers [OR = 10.900 (2.460-48.200), P = 0.002; HR = 5.393 (1.603-18.140), P = 0.006] and OGI [OR = 7.360 (1.650-32.700), P = 0.009; HR = 4.548 (1.321-15.660), P = 0.016] were significantly associated with globe loss.

Conclusion

Corneal ulcer or OGI as the primary etiology is detrimental to globe survival in panophthalmitis.

Diagnosis and Treatment of Culture-Negative Periprosthetic Joint Infection

Identification of the causative organism(s) in periprosthetic joint infection (PJI) is a challenging task. The shortcomings of traditional cultures have been emphasized in recent literature, culminating in a clinical entity known as "culture-negative PJI." Amidst the growing burden of biofilm infections that are inherently difficult to culture, the field of clinical microbiology has seen a paradigm shift from culture-based to molecular-based methods. These novel techniques hold much promise in the demystification of culture-negative PJI and revolutionization of the microbiology laboratory. This article outlines the clinical implications of culture-negative PJI, common causes of this diagnostic conundrum, established strategies to improve culture yield, and newer molecular techniques to detect infectious organisms.

Surgical site infections by atypical mycobacteria: prevalence and species characterization using MALDI-TOF and molecular LCD chip array

BACKGROUND

Surgical site infection (SSI) is a post-operative complication of high concern with adverse impact on patient prognosis and public health systems. Recently, SSI pathogens have experienced a change in microbial profile with increasing reports of non-tuberculous mycobacteria (NTM) as important pathogens.

AIM

of the study The study aimed to detect the prevalence of NTM among cases with SSIs and describe their species using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) and PCR-based microarray.

METHODS

The study was conducted with 192 pus samples collected from patients with SSI. Mycobacterial investigations were done in the form of Ziehl-Neelsen (ZN) smears for acid-fast bacilli, automated mycobacterial culture to isolate mycobacteria, followed by immunochromatography test to predict NTM. NTM-positive cultures were tested by MALDI -TOF MS and PCR-based microarray to reach species-level identification.

RESULTS

Mycobacterial growth was found in 11/192 samples (5.7%) and identified as 4 NTM and 7 M. tuberculosis isolates with prevalence of 2.1% and 3.64%, respectively. The NTM species were described by MALDI-TOF as M. abscessus, M. porcinum, M. bacteremicum, and M. gordonae. Microarray agreed with MALDI-TOF in identifying one isolate (M. abscessus), while two isolates were classified as belonging to broad groups and one isolate failed to be identified.

CONCLUSIONS

The prevalence of NTM among SSI was found to be low, yet have to be considered in the diagnosis of mycobacteria. Employing advanced technologies in diagnosis is recommended to guide for appropriate treatment.

Early onset of deep sternal wound infection after cardiac surgery is associated with decreased survival: A propensity weighted analysis

OBJECTIVES

To compare outcomes after the development of early (≤30 days) versus delayed (>30 days) deep sternal wound infection (DSWI) after cardiac surgery.

METHODS

Between 2005 and 2016, 64 patients were treated surgically for DSWI following cardiac surgery. Thirty-three developed early DSWI, while 31 developed late DSWI. The mean follow-up was 34.1 ± 32.3 months.

RESULTS

Survival for the entire cohort at 1, 3, and 5 years was 93.9%, 85.1%, and 80.8%, respectively. DSWI diagnosed early and attempted medical management was strongly associated with overall mortality (hazard ratio [HR], 25.0 and 9.9; 95% confidence intervals [CIs], 1.18-52.8 and 1.28-76.5; p-value .04 and .04, respectively). Survival was 88.1%, 77.0%, 70.6% and 100%, 94.0% and 94.0% at 1, 3, and 5 years in the early and late DSWI groups, respectively (log-rank = 0.074). Those diagnosed early were more likely to have a positive wound culture (odds ratio [OR], 0.06; 95% CI, 0.01-0.69; p = .024) and diagnosed late were more likely to be female (OR, 8.75; 95% CI, 2.0-38.4; p = .004) and require an urgent DSWI procedure (OR, 9.25; 95% CI, 1.86-45.9; p = .007). Both early diagnosis of DSWI and initial attempted medial management were strongly associated with mortality (HR, 7.48; 95% CI, 1.38-40.4; p = .019 and HR, 7.76; 95% CI, 1.67-35.9; p = .009, respectively).

CONCLUSIONS

Early aggressive surgical therapy for DSWI after cardiac surgery results in excellent outcomes. Those diagnosed with DSWI early and who have failed initial medical management have increased mortality.

Microbiology of Implant-Based Breast Reconstruction Infections: A Systematic Review

BACKGROUND

Postsurgical complications have been an increasing concern for hospitals, particularly in light of payment reform. The costs to the health care system are increasing in light of Medicare penalties for readmissions for certain conditions. Surgical site infection following implant-based breast reconstruction (IBR) remains challenging. The rates of positive cultures and isolated microorganisms in IBR are unknown. This systematic review summarizes the reported microorganisms and positive culture rates in the existing literature.

METHODS

A systematic review was performed using the guidelines outlined in Preferred Reporting Items for Systematic Reviews and Meta-analyses. Articles were included if breast implant infection rates and culture results were reported. Further subgroup analysis of culture positive infections was performed.

RESULTS

A total of 25 studies were included, encompassing 25,177 IBR. Implant infections were reported in 1356 reconstructions (5.4%). Cultures were positive in 74.5% of infections. Gram-positive bacteria were the most common (68.6%), of which Staphylococcus species (51%) was the most isolated pathogen, followed by Pseudomonas. A subgroup analysis showed that early infections (63% vs 88%), radiotherapy (82% vs 93%), and acellular dermal matrix use (90% vs 100%) were associated with lower positive culture rates than their respective counterparts. Patients who received chemotherapy had higher positive culture results (94% vs 83%). Isolated microorganisms also varied among the subgroups.

CONCLUSIONS

This systematic review outlines reported microorganisms in IBR. Staphylococcus species and Pseudomonas were the most frequently reported microorganism. Negative cultures were reported in up to 25.5% of infections. Patients with early infections, radiotherapy, and acellular dermal matrix demonstrated higher negative culture rates. This review can help guide the use of empirical antimicrobial therapy in IBR.

Identification of population of bacteria from culture negative surgical site infection patients using molecular tool

BACKGROUND

Managing surgical site infections, with negative culture report in routine diagnosis is a common dilemma in microbiology accounting more than 30% worldwide. The present study attempted to identify the presence of bacterial spp. if any in wound aspirates/swabs of culture negative surgical site infections of hospitalised patients using molecular tools.

METHODS

Ninety-seven patients with post-operative SSI whose wound swabs/aspirate were negative in the conventional aerobic culture after 72 h of incubation were analysed by 16S rRNA gene specific broad range PCR. The amplified DNA fragments were sequenced by Sanger DNA sequencing method and homology of the sequence were matched using NCBI BLAST (NCBI, USA) RESULTS: Of the 97 patients, 16S rRNA based broad range PCR assay could identify the presence of bacterial pathogen in 53(54.63%) cases, of which 29 isolates were supposed to be of viable but non-culturable bacteria (VBNC), 07 were of obligatory anaerobes and 13 were of unculturable bacteria, 04 were with poly bacterial infections.

CONCLUSIONS

Our study highlights the usefulness of PCR assay in detecting the presence of any VBNC, anaerobes and unculturable bacteria in SSI patients regardless of how well the bacteria may or may not grow in culture. Measures should be taken to use anaerobic culture system and PCR diagnosis along with conventional culture to detect the VBNC and unculturable bacteria where Gram stain is positive for better patient care.

Surgical Site Infection Caused by Mycobacterium Septicum Following Blepharoplasty

BACKGROUND

M fortuitum and M chelonae are commonly reported in surgical site infections caused by nontuberculous mycobacterium, but M septicum is rarely known. Herein, the authors report the first case of surgical site infection caused by M septicum in an immunocompetent patient after blepharoplasty.

METHODS

A 37-year-old woman had persisting bilateral masses on the upper eyelids at 3 months after a blepharoplasty. The excision and revision were performed in a local clinic with the administration of the empirical antibiotic (clarithromycin) for 2 months, but the masses recurred. The patient was referred to the authors' hospital after the steroid was injected. As the right eyelid skin was very thin with the pus pocket, curettage was performed, while the mass on the left eyelid was completely excised. A bacterial, Acid Fast Bacilli culture with antibiotic susceptibility testing, and a DNA-polymerase chain reaction test were performed.

RESULTS

The polymerase chain reaction test identified M septicum. The antibiotic treatment was delayed to identify the susceptibility to antibiotics, but the Acid Fast Bacilli culture result showed no growth. In the meantime, the mass on the right eyelid recurred. Levofloxacin and clarithromycin were administered for 6 months in consultation with the Division of Infectious Diseases. Then the mass was excised. There was no recurrence after 1 year of follow-up.

CONCLUSION

There are a few reports of M septicum catheter-related infection and pulmonary disease, but surgical site infection has not been reported. When a localized mass on a surgical site is found, surgeons should consider M septicum infection and find out the pathogen with its antibiotics susceptibility.

A Randomized Control Trial Comparing Transparent Film Dressings and Conventional Occlusive Dressings for Elective Surgical Procedures

BACKGROUND:

Surgical site infection is one of the major health-care-associated problems causing substantial morbidity and mortality and constituting a financial burden on hospitals as well. The wound management is one of the crucial evidence-based strategies in the reduction of surgical site infection rates

AIM:

To study the impact of standardisation of transparent semipermeable dressing procedure on the rate of surgical site infection in comparison with conventional dressing in clean and clean-contaminated surgeries.

METHODS:

The study included 100 patients who were admitted to surgical wards in Cairo university hospitals, for clean and clean-contaminated operations, in the period from February 2017 to August 2017. Immunocompromised and uncontrolled diabetic patients were excluded. Patients were randomly allocated into two groups; in the first group, patients wounds were covered using transparent semipermeable dressing, while the second group patients’ wounds were covered using conventional occlusive gauze dressing. Patients were followed up for criteria of infection every other day during the first week then at two weeks, three weeks and four weeks.

RESULTS:

In clean and clean-contaminated operations, the transparent dressing group showed a significantly lesser rate of surgical site infection at (2%), compared with the conventional occlusive gauze dressing group with a surgical site infection rate of (14%) (p-value of 0.02).

CONCLUSION:

The transparent semipermeable dressing is effective in reducing surgical site infection rate in clean and clean-contaminated operations.

Current Methods for Molecular Epidemiology Studies of Implant Infections

Over the last few decades, the number of surgical procedures involving prosthetic materials has greatly multiplied, along with the rising medical and economic impact of implant-associated infections. The need to appropriately counteract and deal with this phenomenon has led to growing efforts to elucidate the etiology, pathogenesis and epidemiology of these types of infections, characterized by opportunistic pathogens. Molecular epidemiology studies have progressively emerged as a leading multitask tool to identify and fingerprint bacterial strains, unveil the complex clonal nature of important pathogens, detect outbreak events, track the origin of the infections, assess the clinical significance of individual strain types, survey their distribution, recognize associations of strain types with specific virulence determinants and/or pathological conditions, assess the role played by the specific components of the virulon, and reveal the phylogeny and the mechanisms through which new strain types have emerged. Despite the many advances that have been made thanks to these flourishing new approaches to molecular epidemiology, a number of critical aspects remain challenging. In this paper, we briefly discuss the current limitations and possible developments of molecular epidemiology methods in the investigation and surveillance of implant infections.

Atypical Wound Pathogens

BACKGROUND

Atypical wound pathogens may be so described because they are uncommon pathogens of soft tissue among human beings, or because they may be fastidious and difficult to recover/isolate in the laboratory.

METHODS

A review of pertinent English-language literature was performed.

RESULTS

These wound pathogens are a diverse lot, including aerobic and anaerobic gram-positive and gram-negative bacilli, non-tuberculous mycobacteria, and bacteria that cannot be characterized conventionally because they lack a cell wall (the Mycoplasmataceae). They are diverse with respect to their virulence, but many are opportunistic pathogens.

CONCLUSIONS

Among these atypical pathogens, clinical reports are most common of wound infections caused by Mycoplasma/Ureaplasma (sometimes as co-infecting agents), and the so-called rapidly growing non-tuberculous mycobacteria (Runyon Type IV; e.g., M. chelonae).

Infection after fracture osteosynthesis - Part I

Bone and surgical site infections after osteosynthesis are notoriously difficult to manage and pose a tremendous burden in fracture management. In this article, we use the term osteosynthesis-associated infection (OAI) to refer to this clinical entity. While relatively few surgically treated fractures become infected, it is challenging to perform a rapid diagnosis. Optimal management strategies are complex and highly customized to each scenario and take into consideration the status of fracture union, the presence of hardware and the degree of mechanical stability. At present, a high level of relevant evidence is unavailable; most findings presented in the literature are based on laboratory work and non-randomized clinical studies. We present this overview of OAI in two parts: an examination of recent literature concerning OAI pathogenesis, diagnosis and classification and a review of treatment options.

Resistance Pattern of Antibiotics in Patient Underwent Open Heart Surgery With Nosocomial Infection in North of Iran

Background:

Patients who undergo cardiac surgery appear to be at increased risk for the development of Nosocomial infections (NIs). The development of antibiotic-resistant infections has been associated with significantly greater hospital mortality rates compared to similar infections caused by antibiotic-sensitive pathogens.

Objectives:

The purpose of this study is survey of Nis and antibiotic resistance patterns of causative bacteria among patients who underwent open heart surgery in the north of Iran during a 2-year period between September 2012 and September 2014.

Methods:

In this cross-sectional study we evaluated 187 patients that underwent open heart surgery with NIs. Demographic feature, clinical characteristics and risk factors of each infection were recorded. The antibiotic susceptibility test was performed using the Minimum inhibitory concentration (MIC) method according to the standard protocol of Clinical & Laboratory Standards Institute (CLSI). Detection of Extended-spectrum beta-lactamase (ESBL) producing bacteria was performed by the double-disk synergy (DDS) test; also Methicillin-resistant Staphylococcus (MRSA) strains were identified by MRSA Screen Agar. The collected data were analyzed using the SPSS software (ver. 16) and, descriptive statistics were used.

Results:

Out Of total of 2253 hospitalized patients who underwent open heart surgery, 187(5.05%) patients had NIs. 51.9% of the patients were female. The rates of surgical site infection (SSI), respiratory tract infection, endocarditis, Urinary tract infection (UTI), blood Infection and mediastinitis were 27.80, 25.66%, 17.64, 17.11% 8.55% and 3.20% respectively. E.coli and S.aureus were the most causative agents of NIs. The rate of ESBL-producing bacteria was 14.28- 71.42% among enterobacteriaceae and the rate of MRSA was 54.2% among S.aureus strains. All isolated Acinetobacter.spp were Multi-drug resistance (MDR).

Conclusions:

We showed that the rate of NIs among these high-risk patients was in the average level. But the emergence of MRSA and ESBL bacteria is increasing in our region.

Bacterial biofilms on implanted suture material are a cause of surgical site infection

BACKGROUND

Surgical site infection (SSI) has been estimated to occur in up to 5% of all procedures, accounting for up to 0.5% of all hospital costs. Bacterial biofilms residing on implanted foreign bodies have been implicated as contributing or causative factors in a wide variety of infectious scenarios, but little consideration has been given to the potential for implanted, submerged suture material to act as a host for biofilm and thus serve as a nidus of infection.

METHODS

We report a series of 15 patients who underwent open Roux-en-Y gastric bypass (with musculofascial closure with permanent, multifilament sutures) who developed longstanding and refractory SSIs in the abdominal wall. Explanted suture material at subsequent exploration was examined for biofilm with confocal laser-scanning microscopy (CLSM) and fluorescence in situ hybridization (FISH).

RESULTS

All 15 patients at re-exploration were found to have gross evidence of a "slimy" matrix or dense reactive granulation tissue localized to the implanted sutures. Confocal laser-scanning microscopy revealed abundant biofilm present on all sutures examined; FISH was able to identify the presence of specific pathogens in the biofilm. Complete removal of the foreign bodies (and attendant biofilms) resulted in all cases in cure of the SSI.

CONCLUSION

Bacterial biofilms on implanted suture material can manifest as persistent surgical site infections that require complete removal of the underlying foreign body substrata for resolution.

Chronic surgical site infection due to suture-associated polymicrobial biofilm

BACKGROUND

Surgical site infection (SSI) is a common surgical complication; culture-negative SSI presents a particular problem in management.

METHODS

Examination of explanted foreign bodies (sutures) using confocal laser scanning microscopy (CLSM) and fluorescent in situ hybridization (FISH) after surgical exploration of a chronic culture-negative SSI.

RESULTS

Confocal microscopy (CM) demonstrated bacilli and cocci attached to the surface of the explanted sutures in a mixed biofilm. Fluorescent in situ hybridization confirmed that Staphylococci were components of the mixed biofilm. Removal of the foreign bodies (sutures) resolved the chronic infection.

CONCLUSION

Chronic SSI can arise from underlying bacterial biofilms, which can invest implanted foreign bodies and associated soft tissue surfaces.