LITERATURE UPDATE Mycobacterium tuberculosis stained red using a typical Ziehl-Neelsen method.


three-year period from May 2015 to April 2018 were reviewed, and the Gram stain and final culture results noted. A total of 830 samples were included


from both native and replaced joints. Native joints accounted for a total of 701 cases (84%) of the aspirates, while those obtained from prosthetic joints accounted for 129 (16%). In 74 (9%) cases there was a discrepancy between the Gram stain and culture results. The sensitivity of the Gram stain in this case series was 22% and the specificity of the test was 99.6%. The clinician should have a low


threshold for overlooking a negative Gram stain result and place greater emphases on the clinical findings in conjunction with biochemical markers.


Bronchoalveolar lavage Gram stains for early bacterial identification in pneumonia: should they stay or should they go? Klimko CV, Sanders JM, Monogue ML et al. Crit Care Explor 2021; 3 (8): e0501. doi: 10.1097/CCE.0000000000000501. eCollection 2021 Aug.


The primary endpoint in this study was to determine the sensitivity and specificity of the bronchoalveolar lavage Gram stain in predicting culture results. Secondary endpoints included determining the proportion of Gram stains from bronchoalveolar lavages that accurately identify culture isolates and the duration of antibiotic treatment before bronchoalveolar lavage collection. Two-hundred and five isolates were included. Gram stains for Gram-positive and Gram-negative isolates showed high specificity, 97.3% and 100%, respectively, but lower sensitivity at 61.9% and 54.2%, respectively. The positive predictive value and negative predictive value were 77.2% and 95.7% for Gram-positive isolates and 100% and 84.4% for Gram-


60


negative isolates, respectively. Gram stains correctly identified isolates on the bronchoalveolar lavage culture in 61.9% of Gram-positive organisms and in 54.2% of Gram-negative organisms. Gram stains accurately identified causative organisms in a limited number of patients, making the utility of the Gram stain an uncertain modality for predicting causative respiratory pathogens from bronchoalveolar lavage samples.


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


Karsiyakali N, Yucetas U, Karatas A, Karabay E, Okucu E, Erkan E. World J Urol 2021; 39 (6): 2135–46. doi: 10.1007/ s00345-020-03381-y.


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).


A total of 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 samples from the renal collecting system, while RSC was performed using stone fragments. Patients were divided into two groups: Group 1 (n=119) without postoperative fever (<380


C) and Group 2 (n=22) with postoperative fever (≥380 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.


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 (odds ratio [OR]: 10.6; 95% confidence interval [CI]: 4.07–27.9; P<0.001 and OR: 15.0; 95% CI: 5.4–41.2; P<0.001, respectively). In conclusion, RPUGS is as effective as RSC in predicting fever after PCNL. The authors recommend RPUGS during PCNL to manage post-PCNL infectious complications.


Detection of mycobacteria in paraffin- embedded Ziehl-Neelsen-stained tissues using digital pathology Sua LF, Bolaños JE, Maya J et al. Tuberculosis (Edinb) 2021 Jan; 126: 102025. doi: 10.1016/j.tube.2020.102025.


Early diagnosis of paucibacillary tuberculosis represents a challenge, even with direct tissue examination. Digital pathology allows the analysis of tissues to identify microorganisms. In this study, the authors aim to develop a program to detect and quantify typical and atypical mycobacteria in paraffin-embedded Ziehl- Neelsen-stained tissues.


The building of the Pat-Scan program included pathology, systems engineering, and scientific applications. The iScan Coreo Au scanner was used, and nine variables were adjusted. Ten Ziehl- Neelsen-stained samples were fragmented into 2000 images and analysed to validate the reproducibility of the bacilli images in the tissue, as detected by the software. Pat-Scan included software and a scanner used to detect and quantify bacilli in paraffin-embedded Ziehl-Neelsen- stained tissues. All samples containing mycobacteria were successfully analysed by the scanner, and the bacilli could be detected; these results were validated by expert pathologists by microscopy examination, and the presence of bacilli was confirmed in all cases.


Pat-Scan allowed the identification and quantification of mycobacteria in paraffin- embedded Ziehl-Neelsen-stained tissues, offering a reproducible diagnostic method that reduces the time for diagnosis and does not affect precision. Further validation is needed for application in the clinical setting.


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