Correction: Two stable variants of Burkholderia pseudomallei strain MSHR5848 express broadly divergent in vitro phenotypes associated with their virulence differences.

[This corrects the article DOI: 10.1371/journal.pone.0171363.].

Two stable variants of Burkholderia pseudomallei strain MSHR5848 express broadly divergent in vitro phenotypes associated with their virulence differences.

Burkholderia pseudomallei (Bp), the agent of melioidosis, causes disease ranging from acute and rapidly fatal to protracted and chronic. Bp is highly infectious by aerosol, can cause severe disease with nonspecific symptoms, and is naturally resistant to multiple antibiotics. However, no vaccine exists. Unlike many Bp strains, which exhibit random variability in traits such as colony morphology, Bp strain MSHR5848 exhibited two distinct and relatively stable colony morphologies on sheep blood agar plates: a smooth, glossy, pale yellow colony and a flat, rough, white colony. Passage of the two variants, designated "Smooth" and "Rough", under standard laboratory conditions produced cultures composed of > 99.9% of the single corresponding type; however, both could switch to the other type at different frequencies when incubated in certain nutritionally stringent or stressful growth conditions. These MSHR5848 derivatives were extensively characterized to identify variant-associated differences. Microscopic and colony morphology differences on six differential media were observed and only the Rough variant metabolized sugars in selective agar. Antimicrobial susceptibilities and lipopolysaccharide (LPS) features were characterized and phenotype microarray profiles revealed distinct metabolic and susceptibility disparities between the variants. Results using the phenotype microarray system narrowed the 1,920 substrates to a subset which differentiated the two variants. Smooth grew more rapidly in vitro than Rough, yet the latter exhibited a nearly 10-fold lower lethal dose for mice than Smooth. Finally, the Smooth variant was phagocytosed and replicated to a greater extent and was more cytotoxic than Rough in macrophages. In contrast, multiple locus sequence type (MLST) analysis, ribotyping, and whole genome sequence analysis demonstrated the variants' genetic conservation; only a single consistent genetic difference between the two was identified for further study. These distinct differences shown by two variants of a Bp strain will be leveraged to better understand the mechanism of Bp phenotypic variability and to possibly identify in vitro markers of infection.

Institutional learning curve of surgeon-performed trauma ultrasound.

BACKGROUND: Sonography has become the primary mode for the initial evaluation of abdominal injury in many trauma centers. However, the rate at which nonradiologists become proficient in this technique remains controversial. OBJECTIVE: To assess the learning curve for this technique in a single institution. DESIGN: Retrospective review of sonographic examinations for trauma performed by senior surgical residents during a 24-month period at an American College of Surgeons-verified level I trauma center. SETTING: University-affiliated private hospital. PATIENTS AND METHODS: Before the initiation of a program of surgeon-performed trauma ultrasound, senior surgical residents (postgraduate years 4 and 5) received 11.5 hours of hands-on and didactic instruction in the focused ultrasound examination for trauma. This examination then became a standard component of the evaluation of injured patients. Subsequent groups of senior residents received 8 hours of instruction at the onset of new academic years, 6 and 18 months, respectively, after the initial course. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were then calculated for each 6-month period after the introduction of trauma sonography. RESULTS: During the 24-month study period, 902 sonographic examinations were performed. No statistically significant differences were noted in sensitivity, specificity, accuracy, positive predictive value, or negative predictive value for any 6-month period of study when compared with the other 6-month periods or with the values calculated for the entire study period. CONCLUSIONS: Senior surgical residents are capable of performing the focused ultrasound examination for trauma with a high level of skill after a concise introductory course. A learning curve was not apparent in our series. Criteria for being permitted to perform trauma sonography that include the requirement of a large number of examinations or extensive proctoring should be reassessed.

A comparison of sonographic examinations for trauma performed by surgeons and radiologists.

BACKGROUND: It has been demonstrated that surgeons and surgery residents, trained in the focused abdominal sonographic examination, are able to accurately and reliably evaluate trauma patients. Despite this, radiologists have objected to surgeon-performed sonography for several reasons. We set out to compare the accuracy of sonographic examinations performed by surgery residents and radiologists. METHODS: A retrospective review of medical records of all trauma patients who received focused ultrasound examinations from January 1, 1995, through June 30, 1996, at one of two American College of Surgeons-verified Level I trauma centers in the same city was undertaken. Ultrasound examinations were performed by surgery residents at trauma center A (TCA) and by radiologists or radiology residents at trauma center B (TCB). Findings for each patient were compared with the results of computed tomography, diagnostic peritoneal lavage, operative exploration, or observation. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were calculated for each group of patients. Comparison of patient charges for the trauma ultrasound examinations at each of the trauma centers was also made. RESULTS: Patient populations at the two centers were similar except that the mean Injury Severity Score at TCB was higher than at TCA (11.74 vs. 9.6). Sensitivity, specificity, accuracy, or negative predictive value were not significantly different between the two cohorts. A significantly lower positive predictive value for examinations performed by surgery residents was noted and attributed to a lower threshold of the surgery residents to confirm their findings by computed tomography. Billing data revealed that the average charge for trauma sonography by radiologists (TCB) was $406.30. At TCA, trauma sonography did not generate a specific charge; however, a $20.00 sum was added to the trauma activation fee to cover ultrasound machine maintenance and supplies. CONCLUSION: Focused ultrasound examination in the trauma suite can be as safely and accurately performed by surgery residents as by radiologists and radiology residents and should be a routine part of the initial trauma evaluation process.

Sonographic examination of abdominal trauma by senior surgical residents.

The focused ultrasound examination is assuming an important role in the evaluation of abdominal trauma. We evaluated the ability of senior surgical residents to independently use this technique. We also evaluated the efficacy of a single sonographic examination instead of serial examinations. Senior surgical residents underwent sonography instruction by two attending surgeons certified in the technique. Once proficiency was attained, a single sonographic examination was performed on patients with abdominal trauma triaged to a Level I trauma center. Residents obtained additional diagnostic studies deemed appropriate. Ultrasound results were compared with other diagnostic studies and clinical course. Sonography was performed on 518 patients between January 10, 1995 and June 30, 1996. Mechanism of injury was blunt in 92 per cent of patients and penetrating in 8 per cent. There were 22 true positives, 12 false positives, 8 false negatives, and 476 true negatives. Five of the eight false negatives were secondary to limited hollow viscus injuries with minimal associated intraperitoneal fluid. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were 73.3, 97.5, 96.1, 64.7, and 98.3 per cent, respectively. The use of computed tomography and diagnostic peritoneal lavage decreased from 25 to 18 per cent and 3.2 to 0.2 per cent, respectively, as diagnostic tools. We conclude that surgical residents can competently perform trauma ultrasound. A single sonographic examination is effective and reliable. Sonography has essentially replaced diagnostic peritoneal lavage in our institution.

A new concept for implementation of a required general surgery clerkship.

BACKGROUND: Two years ago our institution abbreviated the junior internal medicine and general surgery clerkships to accommodate a 4-week family practice clerkship and a 4-week elective clerkship. As a consequence, 1-month mandatory internal medicine and general surgery clerkships were placed in the senior year. METHODS: The surgical disorders most commonly encountered by the generalist are discussed. The senior students spend 4 weeks with a community-based surgeon. All lectures are presented by full-time faculty and adhere to the student manual, which is designed to coincide with examination material. Three histories and physicals are reviewed by the course director to determine utilization of critical thinking skills. The development of healthy interpersonal and professional relationships is addressed by a 2-hour module on the essentials of integrity, compassion, humility, and self-knowledge. A faculty development seminar provides an awareness of course objectives and logistics. Student grades are determined by the preceptor's evaluation (50%), an in-house written examination (50%), and submission of adequate history and physicals. RESULTS: Subjective reviews by students (n = 115) reveal that although only 27% of the students care to pursue a surgical practice, 85% feel that their time was effectively spent and 83% feel that the clerkship should be offered to future fourth year medical students. Seventy percent of submitted history and physicals (n = 420) exhibit appropriate critical thinking skills. CONCLUSIONS: We are currently in the midst of our third year of implementation. The students are receiving insight into a surgical approach to common disease processes. History and physical examination skills and healthy interpersonal relationships are reinforced. Although change is often difficult to accomplish and accept, the positive response to the newly formatted senior curriculum has exceeded expectations.