Results Of Semiquantitative Cultures Research Articles

Cutibacterium subtype distribution on the skin of primary and revision shoulder arthroplasty patients

The skin of healthy shoulders is known to harbor multiple different subtypes of Cutibacterium (formerly Propionibacterium) acnesat the same time. C acnes can often be isolated from deep tissue and explant samples obtained during revision of a failed shoulder arthroplasty, presumably because the shoulder was inoculated with organisms from the patient's skin at the time of the index arthroplasty. It is possible that specific subtypes or distributions of subtypes may be associated with an increased pathogenic potential and that the skin of patients undergoing revision arthroplasty contains different distributions of the subtypes than in patients undergoing primary arthroplasty. We analyzed the subtype distribution of Cutibacterium from the skin of shoulders undergoing revision arthroplasty vs. primary arthroplasty. Preoperative skin swabs were collected from 25 patients who underwent primary shoulder arthroplasty and 27 patients who underwent revision shoulder arthroplasty. The results of semiquantitative cultures of the skin and deep tissues were reported as specimen Cutibacteriumvalues, and scores from all deep tissue samples were added to report the total shoulder Cutibacteriumscore. Single-locus sequence typing (SLST) of Cacnes from the skin swabs was used to determine the subtype distribution for each patient. The percentage of each subtype for each patient was averaged in patients undergoing revision arthroplasty and then compared with that in patients undergoing primary arthroplasty. The C acnes subtype distribution on the skin of revision arthroplasty patients was different from that of primary shoulder arthroplasty patients, with a significantly higher percentageof SLST subtype A (36.9% vs. 16.0%, P = .0018). The distribution of SLST subtypes was similar between revision arthroplasty patients with strongly positive culture findings vs. those with weakly positive or negative culture findings. Significant differences in the skin Cutibacterium subtype distributions were found between shoulders undergoing revision shoulder arthroplasty and those undergoing primary shoulder arthroplasty. Future studies are needed to determine whether certain Cutibacterium subtype distributions are associated with an increased risk of arthroplasty revision.

Procalcitonin-guided antibiotic discontinuation in ventilator-associated pneumonia: a prospective observational study.

Background: Procalcitonin (PCT), an important biomarker, can be used for the guidance of antibiotic therapy in respiratory infection. However, it has been a problem that some patients might need antibiotic therapy restart because of infection recurrence after antibiotic discontinuation. To date, there are very few literature on the study of risk factors accounting for infection recurrence. Purpose of this clinical study: 1) To study on antibiotic discontinuation in ventilator-associated pneumonia (VAP) under the guidance of PCT; 2) To evaluate the possible risk factors leading to infection recurrence and antibiotic reuse.Methods: Antibiotic discontinuation was performed when patients met the following criteria: (i) serum PCT<0.5 μg/L, (ii) temperature<38.5℃ and (iii) leukocyte count<15×109/L. Next, the patients were divided into infection recurrence group (infection recurring within 7 days after antibiotic discontinuation) or infection controlled group (no infection recurring after antibiotic discontinuation). Possible risk factors accounting for infection recurrence were evaluated using logistic regression analysis.Results: Of the eligible 51 patients with VAP, 20 patients suffered infection recurrence. Clinical pulmonary infection score (CPIS) and characteristics of tracheal secretions were the independent risk factors (P=0.045 and P=0.041, respectively), accounting for infection recurrence. Simplified CPIS≥5 served a certain predictive value for infection recurrence in VAP when physicians considered antibiotic discontinuation (The area under the receiver operating characteristic curve 0.781, specificity 90.3%, sensitivity 55.0%, positive predictive value 78.6% and negative predictive value 75.7%). At the time of antibiotic discontinuation, differences between the two groups were not statistically significant in the proportion of patients with a tracheotomy and in the culture results of endotracheal aspirates (including semi-quantitative results and whether pathogens were multidrug-resistant [MDR] strains).Conclusion: Simplified CPIS and characteristics of tracheal secretions can be used to predict infection recurrence following PCT-guided antibiotic discontinuation in VAP. These findings are important because physicians may not need to put too much care on semi-quantitative culture results of endotracheal aspirates and whether pathogens are MDRstrains.Trial registration: The registration number of this clinical trial is: ChiCTR-OPC-17011228 (Trial registry name: Chinese Clinical Trial Registry; URL: http://www.chictr.org.cn).

Detection and identification of bacterial pathogens directly from sputum samples by pyrosequencing.

The standard culture findings for detecting and identifying bacterial pathogens in patients with lower respiratory tract infections (LRTIs) are usually not available for two to three days, which delays the initiation of appropriate antibiotic therapies. We aimed to develop a faster method of identification of bacterial pathogens in LRTIs which would offer a timelier guide to initial antibiotic choices. The developed PCR-pyrosequencing-based method was defined as mask PCR-pyrosequencing (MPP). This method uses primer pairs deliberately designed to mask the interference of colonised bacteria in sputum to detect and identify bacterial pathogens directly from LRTI patient sputum samples within 5 h. Accordingly, the standard PCR-pyrosequencing method was defined as normal PCR-pyrosequencing (NPP) here. The clinical performance of the novel system was evaluated by comparing with traditional semi-quantitative culture and identification results. The coincidence for culture and MPP was 91.3 %. Compared with the semi-quantitative culture results, NPP identified 89.9 % strains of grade 3+ (corresponding to 1.0×106 c.f.u ml-1) and 100 % of grade 4+ (corresponding to 1.0×107 c.f.u ml-1), both of which were considered to be the presumptive pathogens in the clinics. MPP identified 98.9 % strains of grade 3+ and 100 % of grade 4+. Additionally, PCR-pyrosequencing could detect a minimum concentration of 1.0×106 c.f.u ml-1 of bacteria in sputum, with no significant difference between NPP and MPP. The PCR-pyrosequencing technique developed in this study is an accurate, fast, and high throughput method for the direct detection and identification of bacterial pathogens from sputum.

Clinical significance of the radiological severity score in Mycobacterium avium complex lung disease patients

Practical methods for assessing the radiographic findings of Mycobacterium avium complex lung disease (MAC-LD) have not been established. To identify a correlation between the radiological score and semi-quantitative culture results of respiratory samples, and to assess the prognostic impact of this radiological score in MAC-LD patients. We retrospectively studied 218 MAC-LD patients. Radiographic findings were classified as nodule (N), infiltration shadow (I), cavity (C) and bronchiectasis (E), scored individually according to the area occupied on six lung field divisions, and added to give the radiological severity score. The radiological score positively correlated with the semi-quantitative culture score (P = 0.003). In univariate analysis, the radiological score was a significant negative prognostic factor for overall survival. On multivariate analysis, factors I, C and E were independent negative prognostic factors for overall survival. We compared the prognostic value of the total score of all four factors and the three significant factors (I, C and E) using receiver operating characteristic curve analysis; the corresponding areas under the curves were respectively 0.628 and 0.763 (P < 0.001). The radiological score correlates with prognosis. The combined score of factors I, C and E may more accurately predict prognosis in MAC-LD patients.

Evaluation of the Xpert Carba-R (Cepheid) Assay Using Contrived Bronchial Specimens from Patients with Suspicion of Ventilator-Associated Pneumonia for the Detection of Prevalent Carbapenemases.

There is a critical need for rapid diagnostic methods for multidrug-resistant (MDR) pathogens in patients with a suspicion of ventilator-associated pneumonia (VAP). The Xpert Carba-R detects 5 targets for carbapenemase-producing organisms (blaKPC, blaNDM, blaVIM, blaOXA-48, and blaIMP-1). Our objective was to evaluate the performance of this assay directly on bronchial aspirates and to correlate the cycle number for a positive result (Ct) with the bacterial count. Bronchial aspirates from patients with a suspicion of VAP were spiked with a dilution of 1 of 4 MDR organisms carrying the resistance genes detected by the test prepared to a final concentration of 102−105 cfu/mL. We used a ROC curve and provided areas under the curve (AUC) with their 95% confidence intervals (CI). A point of maximum sensitivity (Se) and specificity (Sp) was derived and validity indices were calculated. One hundred contrived tests were performed. Se and Sp were 100% for all bacterial counts. A positive sample with a Ct ≤24.7 corresponded to a count ≥105 cfu/mL; if the Ct was within the range >24.7-≤26.9, this corresponded to a count ≥104 cfu/mL. When the Ct was >26.9, this corresponded to a count <104 cfu/mL. The Xpert Carba-R detects carbapenemase-producing organisms directly in contrived bronchial aspirates. Still, an important issue to consider is that the number of gene copies may vary according to many factors in vivo. If confirmed in further studies, the strong correlation observed between Ct values and the results of semiquantitative cultures suggests this test could serve to differentiate between infection and colonization in routine clinical practice.

Differential quantitative blood cultures for the diagnosis of catheter-related bloodstream infections associated with short- and long-term catheters: A prospective study

We prospectively evaluated the value of two levels of differential quantitative blood culture (DQBC) ratio (≥2:1 or ≥5:1) in diagnosing catheter-related bloodstream infections (CRBSIs) in patients with malignancy that have short-term and long-term central venous catheters (CVCs) (<30 and ≥30 days of placement). Diagnosis of CRBSIs was based on results of semiquantitative cultures of removed catheters. For short-term CVCs a 5:1 or greater DQBC ratio had an 18% sensitivity, 67% specificity, 18% positive predictive value (PPV) and 67% negative predictive value (NPV), whereas a 2:1 or greater cut-off point for the DQBC was associated with a 45% sensitivity, 48% specificity, 26% PPV, and 68% NPV for the diagnosis of CRBSIs. For long-term CVCs, a cut-off point of 5:1 or greater of the DQBC had an 81% sensitivity, 40% specificity, 36% PPV, and 83% NPV for the diagnosis of CRBSIa, whereas a 2:1 or greater cut-off point had a 90% sensitivity, 30% specificity, 35% PPV, and 88% NPV for the diagnosis of CRBSIs. In conclusion, DQBCs are not diagnostic of CRBSIs for short-term CVCs. In long-term CVCs, DQBCs at 2:1 or greater or 5:1 or greater are sensitive but associated with low specificity and positive predictive value.

A Reappraisal of Blind Bronchial Sampling in the Microbiologic Diagnosis of Nosocomial Bronchopneumonia: A Comparative Study in Ventilated Patients

To assess the usefulness of fiberscopy for microbiologic diagnosis of nosocomial bronchopneumonia (NBP) in ventilated patients. Data were collected prospectively. We compared the results of semiquantitative cultures obtained by protected specimen brush (PSB), bronchoalveolar lavage (BAL) and blind bronchial sampling (BBS). Positive thresholds were 10(3) CFU ml-1 for PSB and BAL and 10(4) CFU ml-1 for BBS. We also evaluated the diagnostic performance of direct examination of samples obtained by BAL and BBS. We carried out this study in 64 ventilated patients admitted to a medico-surgical ICU. During the study, 85 sets of samplings were obtained. The concordance between the results of specimen cultures obtained with the three techniques was 87 percent. The concordance between BBS and PSB or between BBS and BAL was 91.8 percent. In two of seven patients with discordant results between BBS and PSB, the microorganisms isolated from blood cultures were found on BBS, but not on PSB samples. As for direct examination, the thresholds for the diagnosis of NBP using BBS were as follows: > or = 10 polymorphonuclear neutrophils (PMN)/high-power field (HPF), > or = 1 bacteria/oil immersion field (OIF), presence of intracellular bacterial inclusions. Using BAL, the thresholds were as follows: > or = 1 PMN/HPF, presence of bacteria/OIF, presence of intracellular bacterial inclusions. The specificity of the presence of bacterial inclusions was excellent regardless of the sampling technique, but the sensitivity of this criteria was mediocre (30.8 percent with BBS and 19.2 percent with BAL). Except for the number of PMN on BBS, all the other diagnostic criteria (PMN count on BAL, bacterial count, count of cells exhibiting inclusions) provide a similar prediction of NBP (correctly classified: 61.2 to 81.2 percent). No combination of criteria enabled significantly better classification regardless of the sampling technique. In view of these findings and the high cost and morbidity of fiberscopy, it is arguably better to use a simple, repeatable, and risk-free technique for obtaining culture specimens from mechanically ventilated patients. Obviously, protected brushing techniques remain the most effective for nonintubated patients.

The Clinical Impact of Culturing Central Venous Catheters

The semiquantitative culture technique is a standard procedure for the laboratory diagnosis of catheter-associated infections and catheter-associated bacteremia. In a prospective observational study, we evaluated the clinical impact of the semiquantitative culture results on the treatment of the patient. Clinical impact was defined as a change in diagnosis or therapy on the basis of the semiquantitative culture result. One hundred fifty-seven catheters consecutively submitted from the surgical intensive care unit to the laboratory were studied. In 96% of the episodes, no clinical impact was observed. In the other 4%, clinical decisions were guided mainly by the concurrent positive blood cultures. Newer laboratory techniques that do not require removal of the catheter are needed to guide therapeutic decisions.

Each water outlet is a unique ecological niche for Legionella pneumophila.

We determined the natural history of the colonization of our hospital's potable water by culturing water approximately biweekly from 20 sites throughout the hospital for 4 years. Overall, 545 (24.7%) of the 2200 samples grew Legionella pneumophila. During hyperchlorination, 11.7% of the samples were positive while 41.6% were positive in the absence of chlorination. There was no seasonal trend towards positivity, but there was marked inter-site variation in the semi-quantitative culture results. However, a single strain of legionella (as defined by plasmid profiling) tended to persist at a site. Such a site was a unique ecological niche in that different sites in the same wing were populated by distinct strains. The two wings of our hospital had a significantly different distribution of strains of legionella-plasmid profile type III predominated in the Victoria Wing while types II and VI predominated in Centennial Wing. Twenty-four of our 28 cases of nosocomial Legionnaires' disease occurred in the Centennial Wing. Three of the four cases in the Victoria Wing were caused by plasmid profile type III while 18 of the 24 isolates from patients who acquired their infection in the Centennial Wing were type II. We conclude that each water outlet serves as its own ecological niche of L. pneumophila.

Semiquantitative culture results and pathogenic significance of obligate anaerobes in peritonsillar abscesses.

We studied the bacteria in consecutive peritonsillar abscesses using semiquantitation of the primary culture findings and correlated the results to clinical parameters. Puncture-aspirated pus from 42 abscesses yielded 133 isolates. Group A streptococci were isolated 10 times and, unlike other bacteria, were isolated 4 times in pure culture; other beta-hemolytic streptococci were found in 8 abscesses, and anaerobes were found in 28. The infections were polymicrobial, with two to seven bacteria in 83%. Anaerobes were more abundant than nonanaerobes; members of the genera Streptococcus, Bacteroides, Peptostreptococcus, and Fusobacterium were the most important quantitatively, considering both frequency and abundance. In patients with ongoing antibiotic treatment, nonanaerobes (but not anaerobes) were less abundant than in untreated patients. The abundance of obligate anaerobes (specifically cocci and gram-positive rods) correlated to the severity of illness as defined by fever and short duration before hospitalization. With other groups of bacteria, no such correlation was found. The correlation was not explained by a difference between the antibiotic-treated and the untreated patients. The results indicate the value of the semiquantitation of culture data and the frequency and pathogenic significance of obligate anaerobes in peritonsillar abscesses.

Diagnosis and clinical manifestations of bacterial vaginosis

Among 640 randomly selected women who were attending a sexually transmitted disease clinic and did not have trichomoniasis, 33% had bacterial vaginosis as defined by a composite of four clinical criteria: (1) Vaginal discharge was homogeneous; (2) vaginal discharge had a pH ≥4.7; (3) vaginal discharge had an amine-like odor when mixed with 10% potassium hydroxide; (4) vaginal discharge contained clue cells representing ≥20% of vaginal epithelial cells. Previously published Gram stain criteria for bacterial vaginosis correlated better than results of semiquantitative cultures for Gardnerella vaginalis with presence or absence of clue cells and with composite clinical criteria. Of 293 women with bacterial vaginosis by Gram stain criteria, 65% had symptoms of increased vaginal discharge and/or vaginal malodor, while 74% had signs of characteristic homogeneous vaginal discharge or amine-like odor. Elevated vaginal pH was the least specific and amine-like odor the least sensitive sign of bacterial vaginosis. Gram stain criteria for bacterial vaginosis were not associated with the concentrations of endocervical or vaginal inflammatory cells but were significantly associated with a clinical diagnosis of pelvic inflammatory disease. After adjusting for coinfection, sexual behavior, and other variables, bacterial vaginosis remained associated with adnexal tendemess (odds ratio = 9.2, p = 0.04). Bacterial vaginosis, previously implicated as a risk factor for obstetric infections, may be a risk factor for pelvic inflammatory disease.