Direct Gram staining and its various benefits in the diagnosis of bacterial infections

Time evolution of electrical impedance spectra of Staphylococcus aureus and Escherichia coli bacteria

This research work reports the time evolution of the electrical properties of gram-positive and gram-negative bacteria in aqueous suspensions with methyl violet and Lugol; measurements of galvanostatic electrical impedance spectra were made in a frequency range of 10Hz to 100kHz. The magnitude of the impedance as a function of frequency for methicillin-resistant strains, Staphylococcus aureus (gram-positive), and Escherichia coli O157: H7 (gram-negative) in the presence of methyl violet and Lugol, showed that both strains exhibited a progressive decrease in the magnitude of the electrical impedance with an increasing bacterial population; however, the variation in the magnitude rate of the impedance over time is completely different between the gram-positive and gram-negative strains. The results suggest that the time evolution of the electrical impedance spectra can be used to differentiate Staphylococcus aureus from Escherichia coli bacteria.

Rapid and Simple Approaches for Diagnosis of Staphylococcus aureus in Bloodstream Infections

Staphylococcus aureus is an important causative pathogen of bloodstream infections. An amplification assay such as real-time PCR is a sensitive, specific technique to detect S. aureus. However, it needs well-trained personnel, and costs are high. A literature review focusing on rapid and simple methods for diagnosing S. aureus was performed. The following methods were included: (a) Hybrisep in situ hybridization test, (b) T2Dx system, (c) BinaxNow Staphylococcus aureus and PBP2a, (d) Gram staining, (e) PNA FISH and QuickFISH, (f) Accelerate Pheno^TM system, (g) MALDI-TOF MS, (h) BioFire FilmArray, (i) Xpert MRSA/SA. These rapid and simple methods can rapidly identify S. aureus in positive blood cultures or direct blood samples. Furthermore, BioFire FilmArray and Xpert MRSA/SA identify methicillin-resistant S. aureus (MRSA), and the Accelerate Pheno^TM system can also provide antimicrobial susceptibility testing (AST) results. The rapidity and simplicity of results generated by these methods have the potential to improve patient outcomes and aid in the prevention of the emergence and transmission of MRSA.

Succession of the Gut Microbiome in the Tibetan Population of Minjiang River Basin

Tibetans are one of the oldest ethnic groups in China and South Asia. Based on the analysis of 1,059 Tibetans in the Minjiang River basin at an altitude of 500–4,001 m, we found that the dominant phyla of the Tibetan population were Bacteroidota and Firmicutes, and the main genera were Prevotella and Bacteroides, which were mostly in consistent with other nationalities. We further evaluated in total 115 parameters of seven categories, and results showed that altitude was the most important factor affecting the variation in the microbial community. In the process of emigration from high altitudes to the plain, the gut microbial composition of late emigrants was similar to that of plateau aborigines. In addition, regarding immigration from low altitude to high altitude, the microbial community became more similar to that of high altitude population with the increase of immigration time. Changes in these microbes are related to the metabolism, disease incidence and cell functions of the Tibetan population. The results of other two cohorts (AGP and Z208) also showed the impact of altitude on the microbial community. Our study demonstrated that altitude of habitation is an important factor affecting the enterotype of the microflora in the Tibetan population and the study also provided a basis to explore the interaction of impact parameters with gut microbiome for host health and diseases.

The effects of preoperative intestinal dysbacteriosis on postoperative recovery in colorectal cancer surgery: a prospective cohort study

Background

Accumulating evidence suggests a critical role of intestinal dysbacteriosis in surgical site infections and anastomotic leakage after abdominal surgery. However, a direct correlation between pre-existing dysbacteriosis and postoperative infectious complications has not yet been established clinically.

Methods

A total of 353 consecutive patients who underwent colorectal cancer (CRC) surgery were enrolled. Gram-stained faecal smears were tested at admission and the first defecation after surgery. Intestinal dysbacteriosis was graded into three groups: normal or slightly decreased intestinal microflora (grade 1), moderate dysbacteriosis (grade 2), and severe dysbacteriosis (grade 3). Clinical outcomes were postoperative infections and anastomotic leakage within 30 days after surgery.

Results

At the preoperative assessment, 268 (75.9%) patients had normal or slightly decreased intestinal microflora, 58 (16.4%) patients had moderate dysbacteriosis, and 27 (7.6%) patients had severe dysbacteriosis. The patients with preoperative dysbacteriosis had a higher rate of early postoperative diarrhoea (grade 2: OR = 4.53, 95% CI 2.28–9.00, grade 3: OR = 4.52, 95% CI 1.81–11.31), total complications (grade 3 40.7% vs. grade 2 25.9% vs. grade 1 12.7%, P < 0.001), and anastomotic leakage (grade 3 11.1% vs. grade 2 5.2% vs. grade 1 1.5%, P = 0.002). An interaction effect among preoperative dysbacteriosis and early postoperative diarrhoea on total complications was observed in rectal cancer patients (P for interaction = 0.007).

Conclusions

An imbalance of the intestinal microbiome exists in a considerable proportion of CRC patients before surgery. Preoperative dysbacteriosis is associated with higher rates of early postoperative diarrhoea, which further correlates with infectious complications and anastomotic leakage. However, the contribution of preoperative dysbacteriosis to the occurrence of anastomotic leakage needs to be clarified in further studies.

Trial registration ChiCTR, ChiCTR1800018755. Registered 8 October 2018—Retrospectively registered, http://www.chictr.org.cn/ChiCTR1800018755.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-02035-6.

Effectiveness of expiratory technique and induced sputum in obtaining good quality sputum from patients acutely hospitalized with suspected lower respiratory tract infection: a statistical analysis plan for a randomized controlled trial

Background

Targeted antimicrobial treatment is essential to avoid unnecessary use of broad-spectrum antibiotics and antimicrobial resistance. Targeted treatment relies on a precise microbiological diagnosis — in pneumonia, this poses a challenge as the usefulness of Gram stains and cultures is highly dependent on the quality of the sputum sample.

This study aims to examine adverse effects and quality of sputum samples obtained by expiratory techniques (forced expiratory technique and sputum induction) compared with tracheal suction. The hypothesis is that expiratory techniques are non-inferior to tracheal suction in obtaining samples from the lower respiratory tract. This statistical analysis plan (SAP) describes the study design, method, and data analysis of the trial to increase transparency, avoid reporting bias or data-driven analysis and increase the study’s reproducibility.

Method

The design is a pragmatic, non-inferiority, parallel-arm randomized controlled trial including 280 patients admitted with suspected lower respiratory infection to two emergency departments. Patients are randomized to a usual care group, where sputum samples are collected by tracheal suction or to an intervention group where sputum samples are collected by forced expiratory technique and sputum induction. The statistical analysis will follow an intention-to-treat protocol. This SAP is developed and submitted before the end of recruitment, database closure, and statistical analyses.

Discussion

The results of this study will provide valuable knowledge to clinical practice by comparing adverse effects and sputum sample quality associated with different sample methods.

Trial registration

Clinicaltrials.gov, NCT04595526. Submitted on October 19, 2020

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05639-1.

Leukocyte Esterase and Glucose Reagent Test Can Rule in and Rule out Septic Arthritis

BACKGROUND/AIM

Septic arthritis (SA) requires rapid diagnosis and therapy to avoid joint damage. This study evaluated the diagnostic accuracy of leukocyte esterase (LE) and glucose (GLC) strip tests for diagnosing SA.

PATIENTS AND METHODS

Synovial fluids from 455 patients with atraumatic joint effusions were assessed prospectively over a 5-year period with LE and glucose strip tests. Results were compared to modified Newman criteria for diagnosing joint infections. Synovial fluid cultures, crystal, blood and synovial cell analyses were also performed.

RESULTS

Forty-one patients had SA and 252 non-SA. A positive LE reading combined with negative glucose reading could detect SA with 100% specificity, 85% sensitivity, 100% positive predictive value (PPV) and 98% negative predictive value (NPV). Positive synovial LE reading alone detected SA with 82% specificity, 95% sensitivity, 47% PPV, and 99% NPV.

CONCLUSION

Combined LE and glucose strip tests represent a low-cost tool for rapidly diagnosing or ruling out SA.

Scanning Electron Microscope: A New Potential Tool to Replace Gram Staining for Microbe Identification in Blood Cultures

Blood culture is currently the most commonly used method for diagnosing sepsis and bloodstream infections. However, the long turn-around-time to achieve microbe identification remains a major concern for clinical microbiology laboratories. Gram staining for preliminary identification remains the gold standard. We developed a new rapid strategy using a tabletop scanning electron microscope (SEM) and compared its performance with Gram staining for the detection of micro-organisms and preliminary identification directly from blood cultures. We first optimised the sample preparation for twelve samples simultaneously, saving time on imaging. In this work, SEM proved its ability to identify bacteria and yeasts in morphotypes up to the genus level in some cases. We blindly tested 1075 blood cultures and compared our results to the Gram staining preliminary identification, with MALDI-TOF/MS as a reference. This method presents major advantages such as a fast microbe identification, within an hour of the blood culture being detected positive, low preparation costs, and data traceability. This SEM identification strategy can be developed into an automated assay from the sample preparation, micrograph acquisition, and identification process. This strategy could revolutionise urgent microbiological diagnosis of infectious diseases.

Renal pelvis urine Gram stain as a traditional, but new marker in predicting postoperative fever and stone culture positivity in percutaneous nephrolithotomy: an observational, prospective, non-randomized cohort study

PURPOSE

The aim of this study was to evaluate the diagnostic value of renal pelvis urine Gram staining (RPUGS) in predicting postoperative fever and renal stone culture (RSC) positivity in percutaneous nephrolithotomy (PCNL).

METHODS

Totally 141 consecutive patients undergoing PCNL for renal stone were included between January 2018 and December 2019. The RPUGS and renal pelvis urine culture (RPUC) were performed using urine sample from renal collecting system, while RSC was performed using stone fragments. Patients were divided into two groups as Group 1 (n = 119) without postoperative fever (< 38 °C) and Group 2 (n = 22) with postoperative fever (≥ 38 °C). Stone culture and Gram staining models were created for predicting postoperative fever using constant covariates of the presence of residual stone, hydronephrosis, and stone burden.

RESULTS

A significantly higher number of patients in Group 2 had RPUGS, RSC, and RPUC positivity (p < 0.001, for each). The sensitivity, specificity, positive predictive value, and negative predictive value of RPUGS in predicting postoperative fever were 72.7%, 89.9%, 57.1%, and 94.7%, respectively. It was observed that both models had similar predictive values and diagnostic performances. Although RSC and RPUGS had a similar diagnostic value in predicting postoperative fever in univariable analysis, both were found to be independent predictors in multivariable analysis (OR: 10.6, 95% CI 4.07-27.9, p < 0.001 and OR: 15.0, 95% CI 5.4-41.2, p < 0.001, respectively).

CONCLUSIONS

In conclusion, RPUGS is as effective as RSC in predicting fever after PCNL. We recommend RPUGS during PCNL to manage post-PCNL infectious complications.

Development of a standardized Gram stain procedure for bacteria and inflammatory cells using an automated staining instrument

Gram stain is a subjective and poorly controlled test, and the resultant errors often perplex laboratory scientists. To reduce errors and make Gram stain a precisely controllable and meritorious test, a standardized Gram stain procedure for bacteria and inflammatory cells was developed using an automated staining instrument in this study. Freshly expectorated sputum specimens, used as the optimized targets, were smeared on slides by laboratory technicians, defining each slide loaded with uniform matrix and monolayer cell. And then, the staining and decolorizing time, as well as the stain and decolorant volume, were optimized as 15, 105, 1, and 25 s and 1.1, 1.4, 0.3, and 0.7 ml, respectively. Culture‐positive blood specimens and original purulent fluids were used for confirming the developed standardized Gram stain procedure. Distinct tinctures of bacteria and inflammatory cells adhered to slide uniformly in a monolayer were observed, and the obtained staining results of these samples were highly consistent with their cultured results. Furthermore, according to the staining results under different staining conditions, an updated molecular mechanism of Gram stain for bacteria and the probable staining mechanism for inflammatory cells were also proposed in this study.

Comparison of acridine orange fluorescent microscopy and gram stain light microscopy for the rapid detection of bacteria in cerebrospinal fluid

OBJECTIVE

Bacterial meningitis is a life threatening condition that requires prompt recognition and treatment. Currently, Gram stain is widely used for the microscopic detection of bacterial pathogens in cerebrospinal fluid (CSF). In Nepal, fluorescent microscopes have been installed in laboratories as a part of the National tuberculosis control program. However, information on the utility of the acridine orange (AO) stain for the direct detection of bacteria in CSF samples in Nepal is not available. Therefore, this study aims to compare Gram stain and AO stain for the rapid detection of bacterial pathogens in CSF of clinically suspected meningitis cases in Kathmandu, Nepal.

RESULTS

Bacterial pathogens were detected in 9.30% (36/387) by either of the three tests, 9.04% (35/387) by AO stain, 8.27% (32/387) by culture and 6.46% (25/387) by Gram's stain. Considering culture as a gold standard, the sensitivity of AO stain was higher than Gram stain. The specificity of AO stain was 98.87%. Detection and differentiation of the bacteria was much clear in AO staining than Gram staining. AO is a better alternative to Gram stain in the rapid detection of bacterial pathogens in CSF in the setting where fluorescent microscope is available.

A 5-Year Evaluation of the Implementation of Triple Diagnostics for Early Detection of Severe Necrotizing Soft Tissue Disease: A Single-Center Cohort Study

BACKGROUND

The standardized approach with triple diagnostics (surgical exploration with visual inspection, microbiological and histological examination) has been proposed as the golden standard for early diagnosis of severe necrotizing soft tissue disease (SNSTD, or necrotizing fasciitis) in ambivalent cases. This study's primary aim was to evaluate the protocolized approach after implementation for diagnosing (early) SNSTD and relate this to clinical outcome.

METHODS

A cohort study analyzing a 5-year period was performed. All patients undergoing surgical exploration (with triple diagnostics) for suspected SNSTD since implementation were prospectively identified. Demographics, laboratory results and clinical outcomes were collected and analyzed.

RESULT

Thirty-six patients underwent surgical exploration with eight (22%) negative explorations. The overall 30-day mortality rate was 25%, with an early, SNSTD-related mortality rate of 11% (n = 3). Of these, one patient (4%) underwent primary amputation, but died during surgery. No significant differences between baseline characteristics were found between patients diagnosed with SNSTD in early/indistinctive or late/obvious stage. Patient diagnosed at an early stage had a significantly shorter ICU stay (2 vs. 6 days, p = 0.031). Mortality did not differ between groups; patients who died were all ASA IV patients.

CONCLUSION

Diagnosing SNSTD using the approach with triple diagnostics resulted in a low mortality rate and only a single amputation in a pre-terminal patient in the first 5 years after implementation. All deceased patients had multiple preexisting comorbidities consisting of severe systemic diseases, such as end-stage heart failure. Early detection proved to facilitate faster recovery with shorter ICU stay.