The accuracy and diagnostic value of gram staining joint aspirates in suspected joint infections

BACKGROUND

Septic arthritis is a debilitating condition with prolonged treatment and adverse outcomes. A gram stain is often performed from the joint aspirate sample, followed by a definitive culture. In our study, we assessed the accuracy of gram staining for suspected septic arthritis and explored factors associated with positive culture growth and false negatives in the gram stain.

METHODS

We retrospectively reviewed joint aspirates performed from 2015-2021 at a major trauma centre. Aspirates not cultured for septic arthritis were excluded. Data collected included aspirate site, gram stain and culture result delay, patient demographics, orthopaedic/rheumatological history, and comorbidities. Outcomes measured were gram stain sensitivity and specificity. Factors influencing positive cultures and false negative gram stain results were analysed using logistic regression.

RESULTS

Of 408 joint aspirates meeting the criteria, 37 did not undergo initial gram staining. Gram stain sensitivity was 30.4%, specificity was 97.6%. The delay from aspirate to definitive gram stain and culture results was 1.1 and 5.4 days, respectively Logistic regression identified that prosthetic joint(p = 0.007), past joint infections(p = 0.006), arthritis(p < 0.001), hypertension(p = 0.007), diabetes(p = 0.019) were positively associated with positive cultures. Past joint infections(p = 0.004) were positively associated with false negative gram stain results. Patients on antibiotics during the aspirate had a higher risk of false negative gram stain results (OR = 5.538, 95%CI, 2.802-10.948; p < 0.001).

CONCLUSIONS

In conclusion, the initial gram stain has limited sensitivity and caution should be exercised when interpreting negative results. Vigilance is crucial when the highlighted comorbidities or antibiotic use are present, to assess patients with potential joint infections.

The diagnostic utility of microscopic quality assessment of sputum samples in the era of rapid syndromic PCR testing

This prospective study assessed the value of initial microscopy evaluation of sputum samples submitted for rapid syndromic PCR-based testing. Bacterial detections by the BioFire FilmArray Pneumonia Panel plus in 126 high- and 108 low-quality sputum samples, based on initial microscopy evaluation in samples from patients with lower respiratory tract infections were compared. We found that high-quality samples had a higher proportion of bacterial detections compared to low-quality samples (P = 0.013). This included a higher proportion of detections of bacteria deemed clinically relevant by predefined criteria (70% and 55%, P = 0.016), as well as a higher proportion of detections of Haemophilus influenzae (36% and 20%, P = 0.010). High-quality samples also had more detections of bacteria with high semi-quantitative values. The study found no significant difference between high- and low-quality samples in the proportions of samples with a single species of bacteria detected, samples with a bacteria treated by the clinician, samples with detection of a proven etiology of community-acquired pneumonia by predefined criteria, the number of bacterial species detected, or the detection of Streptococcus pneumoniae, Moraxella catarrhalis, or Staphylococcus aureus. The results showed that 40% (95% CI 35%-47%) of the bacterial detections would have been missed if only high-quality samples were analyzed. This included 41% (27%-56%) of detections of S. pneumoniae, 33% (23%-45%) of detections of H. influenzae, 42% (28%-58%) of detections of S. aureus, and 37% (23%-54%) of detections of M. catarrhalis. These findings suggest that all sputum samples submitted for rapid syndromic PCR testing should be analyzed, regardless of initial microscopy quality assessment. (This study has been registered at ClinicalTrials.gov under registration no. NCT04660084.) IMPORTANCE Microscopic quality assessment of sputum samples was originally designed for sputum culture, and its applicability in today's workflow, which includes syndromic PCR testing, may differ. Addressing this crucial gap, our study emphasizes the need to optimize the use and workflow of syndromic PCR panels, like the BioFire FilmArray Pneumonia plus (FAP plus), in microbiology laboratories. These advanced PCR-based tests offer rapid and comprehensive pathogen detection for respiratory infections, yet their full potential remains uncertain. By comparing bacterial detections in high- and low-quality sputum samples, we underscore the importance of including low-quality samples in testing. Our findings reveal a significant proportion of potentially clinically relevant bacterial detections that would have been missed if only high-quality samples were analyzed. These insights support the efficient implementation of syndromic PCR panels, ultimately enhancing patient care and outcomes.

Bacterial Burden, Not Local Immune Response, Differs Between Acute and Chronic Peri-Prosthetic Joint Infections

Background: Conducting gram stains in peri-prosthetic joint infections (PJI) is known to have poor sensitivity. However, the aims of this study were to use gram stain results of acute and chronic PJI to determine differences with respect to bacterial burden and levels of local innate immunologic response. Patients and Methods: Patients with acute and chronic PJI from January 1, 2016 and December 31, 2020 were identified by use of Current Procedural Terminology codes. Manual review of medical records for infecting organisms and gram stain results for stained bacteria and for local tissue inflammation (amount of polymorphonuclear leukocytes seen on high powered microscopic fields) were recorded. Statistical comparisons between acute (n = 70) and chronic (n = 134) PJI were analyzed with respect to gram stain sensitivity and amount of local tissue inflammation. Results: The ability to identify stained bacteria was statistically significantly higher in the acute cohort (61.4%) than the chronic cohort (9.7%; p < 0.0001). Interestingly, the amount of local inflammation was similar for acute and chronic PJI except in the subgroup analysis with chronic polymicrobial (p = 0.0229) and chronic culture negative (p = 0.0001) PJI. Conclusions: This study shows that both acute and chronic PJI had similar levels of local inflammation seen on gram stains, despite higher bacterial burdens in acute infections. This suggests that innate immune responses, and thus likelihood of infection eradication, is not solely dependent on bacterial burden. These findings should spearhead further research evaluating the different immunologic responses that occur in acute and chronic PJI to improve diagnostics, therapeutics, and infection-free implant survival.

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A Case of Pseudoappendicitis Caused by Campylobacter Enteritis Diagnosed by Gram Staining and Direct Microscopic Investigation of Stool Specimen

Campylobacter infection may progress to a systemic infection through the intestinal tract. In many cases, symptoms are within the self-limiting range and do not require multidisciplinary treatment. In contrast, systemic infections in younger patients may be more severe and require hospitalization. Many differential diagnoses are considered when Campylobacter infection presents with severe abdominal pain, and the initial diagnosis may be difficult. We encountered a patient with Campylobacter infection who presented with acute-onset fever and general malaise. We diagnosed the case in a resource-poor setting by performing Gram staining of stool samples and fecal microscopy. This case suggests that a diagnosis of Campylobacter pseudoappendicitis can be made efficiently by combining various stool tests rather than waiting for culture results.

Predictive Performance of Gram Staining of Catheter Tips for Candida Catheter-Related Bloodstream Infections

We analyzed 2462 episodes of suspected catheter-related bloodstream infection (CRBSI). The sensitivity, specificity, and positive and negative predictive values for detecting Candida CRBSI by gram staining of catheter tips were 66.1%, 99.4%, 84.4%, and 98.4%, respectively. Gram staining may be useful for the early detection of Candida CRBSI.

Value of sputum Gram stain, sputum culture, and bronchoalveolar lavage fluid Gram stain in predicting single bacterial pathogen among children with community-acquired pneumonia

Background

Currently, the microbial etiology of community-acquired pneumonia in children remains challenging. While Gram stain and sputum culture are commonly used to detect bacterial pathogens, it is unclear whether these approaches can predict single pathogen from bronchoalveolar lavage fluid (BALF) culture.

Methods

A retrospective study involving 287 children hospitalized for pneumonia was conducted. Sputum specimens were collected on admission; and BALF specimens were collected within 24 h after admission. Taking BALF culture as the reference standard, the sensitivity and specificity of Sputum Gram stain (SGS), sputum culture, and BALF Gram stain (BGS) were calculated. The agreement between these approaches and BALF culture was compared using kappa statistics.

Results

For SGS, the specificity was 23%. The overall sensitivity was 70%, including 87% for Gram-positive (G+) cocci, 56% for Gram-negative (G-) cocci, and 50% for G-bacilli. For sputum culture, the specificity was 70%. The overall sensitivity was 64%, including 71% for Streptococcus pneumoniae, 71% for Moraxella catarrhalis, and 64% for Haemophilus influenzae. For BGS, the specificity was 71%. The overall sensitivity was 60%, including 77% for G+cocci, 38% for G-cocci, and 44% for G-bacilli. While SGS had poor agreement with BALF culture, both sputum culture and BGS had moderate agreement with BALF culture.

Conclusions

Both sputum culture and BGS are helpful in predicting single bacterial pathogen from BALF culture among children with community-acquired pneumonia. Sputum cultures and BGS can provide early clues for BALF pathogen when BALF culture results are pending or bronchoscopy is not performed.

Utility of Drain Fluid Culture and Gram Stain in Early Intervention for Occult Anastomotic Leakage in Colorectal Cancer

BACKGROUND/AIM

Although occult leakage after colorectal surgery does not usually cause critical illness, it can cause long-term complications that decrease the quality of life of patients. There is currently no established diagnostic, treatment, or follow-up method for occult leakage. We assessed the risk factors of occult leakage and examined the efficacy of drain fluid culture and Gram staining for its early detection and appropriate treatment intervention.

PATIENTS AND METHODS

Data from 243 consecutive colorectal cancer patients who underwent resection with reconstruction by the double stapling technique between 2016 and 2020 were reviewed.

RESULTS

Sixteen (6.6%) patients had postoperative occult leakage. Multivariate analysis revealed that preoperative treatment was significantly associated with occult leakage (odds ratio=12.423; 95% confidence interval=4.095 to 17.680; p<0.001). Among the 16 patients, 1 experienced stenosis, and none experienced a fistula or chronic sinus. Drain fluid samples of 34 patients (14.0%) were Gram stainpositive, and those of 76 patients (31.3%) were culturepositive. The positive and negative predictive values of drain fluid culture were 18.4% and 98.7%, respectively, and those of Gram staining were 38.2% and 98.6%, respectively, for occult leakage. Among cases with occult leakage, more than two bacterial species were detected in 71.5% of the cultures. Antibiograms indicated that the three major species tended to be resistant to cephem antibiotics, which are used for prophylaxis, but susceptible to carbapenem antibiotics, which are used for empiric therapy.

CONCLUSION

Drain fluid culture and Gram staining may enable early detection and appropriate treatment intervention for occult leakage.

Case Report: Metagenomics Next-Generation Sequencing Can Help Define the Best Therapeutic Strategy for Brain Abscesses Caused by Oral Pathogens

Brain abscesses are associated with an increased long-term risk of new seizures and increased mortality within several years after infection. Common microorganisms that cause brain abscesses include bacteria, fungi, and mycoplasma. We report a 75-year-old man with a brain abscess caused by Prevotella denticola, an oral pathogen. Based on the clinical condition, we suspected that the patient had a blood-borne brain abscess, and he received antibiotics and systemic supportive treatment. The patient developed shock for the second time after negative Gram-staining results. Metagenomics next-generation sequencing showed one strain from the oral microbiome, confirming our hypothesis, and targeted antibiotic treatment was administered quickly. Thus, we report a case in which genomic analysis was the critical factor in determining the best antimicrobial therapy for administration.

Diagnostic performance of the Sputum Gram Stain in predicting sputum culture results for critically ill pediatric patients with pneumonia

BACKGROUND

The sputum Gram stain is an inexpensive, rapid, and convenient laboratory method that predicts the bacterial pathogens in patients with pneumonia. This study aimed to evaluate the diagnostic performance of this method in predicting sputum culture results for critically ill pediatric patients.

METHODS

From June 2008 to June 2018, patients with pneumonia with an endotracheal or a tracheostomy tube in place in the Pediatric Intensive Care Unit at Changhua Christian Hospital were enrolled retrospectively. Sputum was collected from each patient via the artificial airway for Gram stain and culture evaluations of bacterial pathogens. Mixed culture results were excluded. A successful prediction was defined as a match of the sputum Gram stain and culture results.

RESULTS

A total of 622 records were reviewed, of which 542 were analyzed. Haemophilus influenzae, Pseudomonas aeruginosa, and Streptococcus pneumoniae were the three most common pathogens found. The overall prediction success rate of the sputum Gram stain was 59.23%. The sensitivity of the method in predicting gram-negative bacilli (GNB), gram-negative cocci (GNC), and gram-positive cocci (GPC) was 0.45, 0.67, and 0.61, respectively. Its specificity in predicting GNB, GNC, and GPC was 0.87, 0.98, and 0.87, respectively. Its positive likelihood ratio in predicting GNB, GNC, and GPC was 3.46, 33.50, and 4.69, respectively. The highest prediction success rate among all pathogens was for GNC.

CONCLUSION

The sputum Gram stain had high specificity and relatively low sensitivity in predicting the bacterial pathogens in critically ill pediatric patients. Its high specificity in predicting sputum culture results means that clinicians can confidently use sputum Gram stain results to guide their antibiotic choice for treatment.

Comparison of Anti-Microbial Effects of Low-Level Laser Irradiation and Microwave Diathermy on Gram-Positive and Gram-Negative Bacteria in an In Vitro Model

Background and Objectives: The aim of this study was to compare the effects of low-level laser therapy and continuous microwave diathermy on the growth of Gram-negative and Gram-positive bacteria and to establish their efficacy as an alternative therapeutic modality.

MATERIALS AND METHODS

Laser fluence of 13 Joules (J)/cm², 18 J/cm² and 30 J/cm² were used against several bacterial strains. Microwave dosages of 25, 50 and 100 watts (W) were used, respectively.

RESULTS

A significant difference between the three groups was observed using repeated analysis of variance (RANOVA) (F value: 0.74, and p value: 0.001). The Greenhouse-Geisser correction (GG) revealed significant results for laser irradiation alone. However, effect size calculation showed effects with microwave diathermy as well as laser fluence.

CONCLUSIONS

Low-level laser therapy appears to be an effective modality of treatment when compared with continuous microwave diathermy on the Gram-negative and the Gram-positive bacterial strains tested. Microwave diathermy revealed large and medium effects on the bacterial cell counts with dominant effects on Gram-negative strains.

Utility of point-of-care Gram stain by physicians for urinary tract infection in children ≤36 months

Urinary tract infection (UTI) in children requires early diagnosis and treatment to prevent repeated UTI and renal scarring. This study aimed to evaluate the usefulness of the point-of-care Gram stain by physicians for suspected UTI in children at Okinawa Chubu Hospital as a rapid diagnostic test.A single-center, retrospective study was undertaken between January 2011 and December 2015. Patients aged 36 months or younger who were reviewed had suspected UTI in the emergency room or outpatient clinic. Urine culture, urinalysis, and point-of-care Gram stain were performed on a single specimen. Patients with structural or functional urological defects requiring routine catheterization were excluded. We compared the diagnostic performance among the rapid diagnostic tests (i.e., pyuria, point-of-care Gram stain, or both). Kappa statistics were used to evaluate the agreement between the results of point-of-care Gram stain and morphotypes of urine culture with the 95% CI (bias corrected bootstrap interval). We also analyzed which antibiotics were more susceptible to the bacteria of urine culture results, selected by the results of point-of-care Gram stain or empirical treatment based on the Japanese guidelines by McNemar test.Of 1594 patients reviewed in the study, 1546 were eligible according to our inclusion criteria. Using urine culture as the gold standard for UTI, the sensitivity and specificity of pyuria were 73.2% and 95.1%, whereas those of the point-of-care Gram stain were 81.4% and 98.2%, respectively. The concordance rate between the morphotypes of bacteria detected by point-of-care Gram stain and those of urine culture was 0.784 (kappa coefficient) (95% CI 0.736-0.831). Furthermore, the proportion of "susceptible" in the minimum inhibitory concentration of pathogen-targeted treatment based on the point-of-care Gram stain was higher than that of empirical therapy (exact McNemar significance probability: .0001).Our analysis suggests that the point-of-care Gram stain is a useful rapid diagnostic tool for suspected UTI in young children. Pathogen-targeted treatment based on the point-of-care Gram stain would lead to better antibiotic selection compared with empirical therapy.

Gram-stain-based antimicrobial selection reduces cost and overuse compared with Japanese guidelines

BACKGROUND

The Gram stain has been used as an essential tool for antimicrobial stewardship in our hospital since the 1970s. The objective of this study was to clarify the difference in the targeted therapies selected based on the Gram stain and simulated empirical therapies based on the antimicrobial guidelines used in Japan.

METHODS

A referral-hospital-based prospective descriptive study was undertaken between May 2013 and April 2014 in Okinawa, Japan. All enrolled patients were adults who had been admitted to the Division of Infectious Diseases through the emergency room with suspected bacterial infection at one of three sites: respiratory system, urinary tract, or skin and soft tissues. The study outcomes were the types and effectiveness of the antibiotics initially selected, and their total costs.

RESULTS

Two hundred eight patients were enrolled in the study. The median age was 80 years. A significantly narrower spectrum of antibiotics was selected based on the Gram stain than was selected based on the Japanese guidelines. The treatments based on the Gram stain and on the guidelines were estimated to be equally highly effective. The total cost of antimicrobials after Gram-stain testing was less than half the cost after the guidelines were followed.

CONCLUSIONS

Compared with the Japanese guidelines, the Gram stain dramatically reduced the overuse of broad-spectrum antimicrobials without affecting the effectiveness of the treatment. Drug costs were reduced by half when the Gram stain was used. The Gram stain should be included in all antimicrobial stewardship programs.

Evaluation of detection methods for Campylobacter infections among under-fives in Mwanza City, Tanzania

Introduction

Campylobacter species are recognized as a major cause of acute gastroenteritis in humans throughout the world. The diagnosis is mainly based on stool culture. This study was done to evaluate the effectiveness of staining methods (Gram stain using 0.3% carbol fuchsin as counter stain and 1% carbol fuchsin direct stain) versus culture as the gold standard.

Methods

A total of 300 children attending Bugando Medical Centre (BMC) and the Sekou Toure regional hospital with acute watery diarrhea were enrolled. Two sets of slides were prepared stained with 1% carbol fuchsin for 30 seconds first set, and the second set stained with Gram's stain using 0.3% carbol fuchsin as counter stain for five minutes. Concurrently, stool samples were inoculated on Preston Agar selective.

Results

Of 300 stool specimens, 14(4.7%) showed positive culture after 48 hours of incubation and 28 (9.3%) shows typical morphology of Campylobacter species by both Gram stain and direct stain. The sensitivity of the Gram stain using 0.3% carbol fuchsin as counter stain and 1% carbol fuchsin simple stain versus culture as gold standard was 64.3%, with a specificity of 93.4%. The positive predictive value and negative predictive value were 32.1% and 98.2% respectively.

Conclusion

The detection of Campylobacter by 1% carbol fuchsin is simple, inexpensive, and fast, with both a high sensitivity and specificity. Laboratories in settings with high prevalence of campylobacteriosis and/or limited resources can employ 1% carbol fuchsin direct stain in detecting campylobacter infections.

A magnetic Gram stain for bacterial detection

Magnetizing: Bacteria are often classified into gram-positive and gram-negative strains by staining with crystal violet (CV). The described bioorthogonal modification of CV with trans-cyclooctene (TCO) can be used to render gram-positive bacteria magnetic with tetrazine-functionalized magnetic nanoparticles (MNP-Tz). This method allows class-specific automated magnetic detection and magnetic separation.

Luna stain, an improved selective stain for detection of microsporidian spores in histologic sections

Microsporidia in histologic sections are most often diagnosed by observing spores in host tissues. Spores are easy to identify if they occur in large aggregates or xenomas when sections are stained with hematoxylin and eosin (H&E). However, individual spores are not frequently detected in host tissues with conventional H&E staining, particularly if spores are scattered within the tissues, areas of inflammation, or small spores in nuclei (i.e. Nucleospora salmonis). Hence, a variety of selective stains that enhance visualization of spores is recommended. We discovered that the Luna stain, used to highlight eosinophils, red blood cells, and chitin in arthropods and other invertebrates, also stains spores of Pseudoloma neurophilia. We compared this stain to the Gram, Fite's acid fast, Giemsa, and H&E stains on 8 aquatic microsporidian organisms that were readily available in our 2 laboratories: Loma salmonae, Glugea anomala, Pseudoloma neurophilia, Pleistophora hyphessobryconis, Pleistophora vermiformis, Glugea sp., Steinhausia mytilovum, and an unidentified microsporidian from UK mitten crabs Eriocheir sinensis. Based on tinctorial properties and background staining, the Luna stain performed better for detection of 6 of the 8 microsporidia. Gram stain was superior for the 2 microsporidia from invertebrates: S. mytilovum and the unidentified microsporidian from E. sinensis.

Patterns of Gram-stained fecal flora as a quick diagnostic marker in patients with severe SIRS

BACKGROUND

The gut is an important target organ of injury during critically ill conditions. Although Gram staining is a common and quick method for identifying bacteria, its clinical application has not been fully evaluated in critically ill conditions.

AIMS

This study's aims were to identify patterns of Gram-stained fecal flora and compare them to cultured bacterial counts and to investigate the association between the patterns and septic complications in patients with severe systemic inflammatory response syndrome (SIRS).

METHODS

Fifty-two patients with SIRS were included whose Gram-stained fecal flora was classified into three patterns. In a diverse pattern, large numbers of multiple kinds of bacteria completely covered the field. In a single pattern, one specific kind of bacteria or fungi predominantly covered the field. In a depleted pattern, most bacteria were diminished in the field.

RESULTS

In the analysis of fecal flora, the numbers of total obligate anaerobes in the depleted pattern was significantly lower than those in the diverse pattern and single pattern (p < 0.05). The concentrations of total organic acids, acetic acid, and propionic acid in the depleted pattern were significantly lower than those in diverse pattern and single pattern (p < 0.05). Mortality due to multiple organ dysfunction syndrome for the single pattern (52%) and the depleted pattern (64%) was significantly higher than that for the diverse pattern (6%) (p < 0.05).

CONCLUSIONS

Gram-stained fecal flora can be classified into three patterns and are associated with both cultured bacterial counts and clinical information. Gram-stained fecal bacteria can be used as a quick bedside diagnostic marker for severe SIRS patients.

Bacterial Infections: Overview

Bacterial infections have a large impact on public health. Disease can occur at any body site and can be caused by the organism itself or by the body's response to its presence. Bacteria are transmitted to humans through air, water, food, or living vectors. The principal modes of transmission of bacterial infection are contact, airborne, droplet, vectors, and vehicular. Preventive measures have a dramatic impact on morbidity and mortality. Such measures include water treatment, immunization of animals and humans, personal hygiene measures, and safer sex practices. Bacterial resistance to antibiotics is a growing concern mandating their prudent use.