Accuracy Of Gram Stain Research Articles

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

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. 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. 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). 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.

Gram Staining: A Brief Review

The Gram staining is one of the oldest and most important staining techniques used in microbiology first introduced in 1882 by Hans Christian Gram. The staining is the most crucial staining in microbiology and is the first step in differentiating bacteria. The gram-positive bacteria have thick cell wall because of thick layers of peptidoglycan, thus stain purple whereas gram-negative bacteria have thin layers of peptidoglycan and stains red/pink. Decolonization is most important step in gram staining as using decolorizing agent for long time can wash out all the stains from both types of bacteria Gram staining has been there used for over a century, now there have been several advancements in recent years to improve efficiency as well as accuracy of gram staining. Overall, these advancements in Gram staining have improved its efficiency, accuracy, and speed, making it a valuable tool in clinical microbiology and research laboratories. These advancements have enhanced our ability to identify and characterize bacteria, leading to better diagnosis and treatment of bacterial infections. Keywords: Gram staining, staining techniques.

1151 The Accuracy and Diagnostic Value of Gram Staining from Joint Aspirates in Suspected Joint Infection

Abstract Aim Septic arthritis is a debilitating pathology. Joint aspirate gram stain is often performed followed by definitive culture. We review the accuracy of gram staining for suspected septic arthritis, and investigate factors associated with aspirate cultures positive for bacterial growth. Method We reviewed all theatre performed joint aspirates at a Major Trauma Centre from 2015-2021 for suspected septic arthritis. Information collected included aspirate-site, gram stain and culture results delay, patient demographics, orthopaedic/rheumatological history of affected joint, and various comorbidities. Outcomes included sensitivity and specificity of the gram stain. Factors that predisposed patients to positive cultures and false-negative gram stains results were calculated via multivariate binary logistic regression. Results A total of 408 joint aspirates were included, of which 37 did not receive initial gram staining. Gram staining and culture results’ delay were on average 1.1 and 5.4 days respectively. Logistic regression revealed that prosthetic joint (p = 0.007), past joint infections (p = 0.006), arthritis (p&amp;lt;0.001), hypertension (p = 0.007), currently smoking (p = 0.019) were positively associated with positive cultures, and past joint infections (p = 0.004) were significantly positively associated with false negative gram stain results. Patients on antibiotics at time of aspirate were at higher risk of false-negative gram stain results (OR = 5.538, 95% CI [2.802-10.948], p&amp;lt;0.001). Conclusions Whilst the initial gram stain is fast, it has poor sensitivity. We recommend caution when lending any weight to a negative result. Moreover, if the comorbidities highlighted are present or the patient is on antibiotics at time of aspirate, hyper-vigilance should be exercised to risk stratifying patients with any clinical hallmarks of joint infection.

Prevalence of Bacterial Vaginosis in Preterm Labour and Its Fetal and Maternal Outcome

Introduction: Preterm births accounts for about 11.1 % of births worldwide. Infection accounts for 20% – 40% of these cases and Bacterial vaginosis has been found in 15 % of preterm labor group.&#x0D; Objective: To find the prevalence of Bacterial vaginosis among the cases who presented with preterm labour and to determine its maternal and neonatal outcome.&#x0D; Methodology: A prospective cross- sectional analytical study on 100 preterm labour cases conducted over a year in the obstetric ward in Manipal Teaching Hospital. Three high vaginal swabs from posterior fornix were taken and tested in Microbiology laboratory. The maternal and neonatal outcome of women with preterm labour due to bacterial vaginosis were noted. The data were analyzed using SPSS 21. Chi2 test was used for comparing maternal and neonatal complications positive or negative with Bacterial Vaginosis.&#x0D; Results: In the study period, 584 women had preterm deliveries. The total deliveries during that period was 2,531. The prevalence of Bacterial vaginosis in PTB was found to be 17 %.The accuracy of Gram stain was found to be 90% (sensitivity-57%, specificity-92%, PPV-36%, NPV-96%). The accuracy of wet mount was 90 % (sensitivity-42.85%, specificity-93.5%, PPV-33.3%, NPV95.6%). There were increased cases of chorioamnionitis among women who were BV positive (p-value=0.02). Newborn born to women with BV positive had increased chance of poor Apgar score at 5 minutes (p-value &lt;0.05).&#x0D; Conclusion: Maternal and neonatal complications were more common in women with preterm labour associated with Bacterial Vaginosis. Gram stain and wet mount are fairly accurate and can be used as an adjunct to culture for the diagnosis of Bacterial Vaginosis.

Accuracy of tracheal aspirate gram stain in predicting Staphylococcus aureus infection in ventilator-associated pneumonia

BackgroundThe Gram stain can be used to direct initial empiric antimicrobial therapy when complete culture is not available. This rapid test could prevent the initiation of inappropriate therapy and adverse outcomes. However, several studies have attempted to determine the value of the Gram stain in the diagnosis and therapy of bacterial infection in different populations of patients with ventilator-associated pneumonia (VAP) with conflicting results. The objective of this study is to evaluate the accuracy of the Gram stain in predicting the existence of Staphylococcus aureus infections from cultures of patients suspected of having VAP.MethodsThis prospective single-center open cohort study enrolled 399 patients from December 2005 to December 2010. Patients suspected of having VAP by ATS IDSA criteria were included. Respiratory secretion samples were collected by tracheal aspirate (TA) for standard bacterioscopic analysis by Gram stain and culture.ResultsRespiratory secretion samples collected by tracheal aspirates of 392 patients were analyzed by Gram stain and culture. When Gram-positive cocci were arranged in clusters, the sensitivity was 68.4%, specificity 97.8%, positive predictive value 88.1% and negative predictive value 92.8% for predicting the presence of Staphylococcus aureus in culture (p < 0.001).ConclusionsA tracheal aspirate Gram stain can be used to rule out the presence of Staphylococcus aureus in patients with a clinical diagnosis of VAP with a 92.8% Negative Predictive Value. Therefore, 7.2% of patients with Staphylococcus aureus would not be protected by an empiric treatment that limits antimicrobial coverage to Staphylococcus aureus only when Gram positive cocci in clusters are identified.

The accuracy of Gram stain of respiratory specimens in excluding Staphylococcus aureus in ventilator-associated pneumonia

ObjectiveTo evaluate the Gram stain of deep tracheal aspirate as a tool to direct empiric antibiotic therapy, and more specifically as a tool to exclude the need for empiric antibiotic coverage against Staphylococcus aureus in ventilator-associated pneumonia (VAP). DesignA prospective, single-center, observational, cohort study. SettingAll wards at a community hospital. PatientsAdult patients requiring mechanical ventilation, identified as having VAP in a 54-month prospective surveillance database. InterventionsSampling of lower airway secretions by deep endotracheal aspiration was taken from each patient who developed VAP. Samples were sent immediately for Gram stain and qualitative bacterial cultures. Demographic and relevant clinical data were collected; Gram stain, culture, and antibiotic susceptibility results were documented; and outcome was followed prospectively. Measurements and Main ResultsThe analysis included 114 consecutive patients with 115 episodes of VAP from June 2007 to January 2012. Sensitivity of Gram stain compared with culture was 90.47% for gram-positive cocci, 69.6% for gram-negative rods, and 50% for sterile cultures. Specificity was 82.5%, 77.8%, and 79%, respectively. Negative predictive value was high for gram-positive cocci (97%) and sterile cultures (96%) but low for gram-negative rods (20%). Acinetobacter baumanii (45%) and Pseudomonas aeruginosa (38 %) were the prevailing isolates. S aureus was found in 18.3% of the patients. Most isolates were multiresistant. ConclusionsAbsence of gram-positive bacteria on Gram stain had a high negative predictive value. These data can be used to narrow the initial empiric antibiotic regimen and to avoid unnecessary exposure of patients to vancomycin and other antistaphyloccocal agents.

Errors in Interpretation of Gram Stain in The First Notification from Positive BACTEC Blood Cultures in Clinical Microbiology Laboratory of Dr. Kariadi Hospital

Background: Blood cultures in conjunction with the initial Gram stain of positive cultures have often been considered the “gold standard” for the diagnosis of bacteremia. When blood cultures turn positive, the attending physicians are usually notified immediately about Gram stain findings. However, information on the accuracy of Gram staining is very limited. We examined the error of preliminary blood culture reports provided by a local laboratory in an observational study.Design and Method: This was an observational study with a cross sectional approach. In this study, 369 blood cultures were examined. The positive blood cultures (135 samples) were then examined by Gram stain. Blood cultures handled on Bactec 9050, while the Gram stain was done in standard procedure Gram. Interpretation errors of Gram stain were confirmed by cultures result.Result: During one month (April 2011) we examined 369 blood cultures which 135 are positive (36.5%). Positive blood cultures were misread for 6 (4.4%) of 135 patients, they were two read as gram positive cocci had gram negative organisms by culture which were Acinetobacter baumannii, one read as gram positive bacilli had gram negative bacilli by culture which was Klebsiella pneumoniae. One isolate read as gram negative bacilli had gram positive bacilli which was Bacillus species, while two sample read as gram negative bacilli only had polymicrobial by culture, of these one isolate grew to be Enterobacter aerogenes and Staphylococcus aureus and the other were Escherichia coli and Acinetobacter spp.Conclusion: The overall 4.4% error rate of misinterpreted Gram stains from positive blood culture bottles is relatively high, so laboratory professionals and clinical microbiologist must be aware of the potential types of error that occur (Sains Medika, 4(1):23-29).

First Notification of Positive Blood Cultures and the High Accuracy of the Gram Stain Report

When blood cultures turn positive, the attending physicians are usually notified immediately about Gram stain findings. However, information on the accuracy of Gram staining is very limited. We examined the accuracy of preliminary blood culture reports provided by a regional laboratory in an observational study including the years 1996, 2000 to 2001, and 2003. We used data from computer files and technicians' laboratory notes. The study was restricted to cultures with one morphological type. Using cultural identification as a reference, we estimated the sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) for the following defined morphological groups: gram-positive cocci in clusters, gram-positive cocci in chains or diplococci, gram-positive rods, gram-negative cocci, gram-negative rods, and yeasts. We further evaluated the Gram stain and wet mount findings for the most frequent bacterial species/groups. We obtained 5,893 positive blood cultures and the following results for the defined groups: sensitivity, range of 91.3 to 99.7%; specificity, 98.9 to 100%; PPV, 94.6 to 100%; and NPV, 99.0 to 100%. The sensitivity for the most frequent species was in the range 91.3 to 100%, with nonhemolytic streptococci having the lowest value (sensitivity, 91.3%; 95% confidence interval, 86.2 to 94.9%). Wet mount reports were less accurate (sensitivity of 30 to 70% for species with peritrichous motility), and Enterobacteriaceae (notably Salmonella spp.) accounted for 25% of the reports stating polar motility. In conclusion, we demonstrated a high accuracy of Gram stain reports, whereas wet mount microscopy was generally less accurate.