The rabbit model of tuberculosis has been used historically to differentiate between Mycobacterium tuberculosis and Mycobacterium bovis based on their relative virulence in this animal host. M. tuberculosis infection in market rabbits is cleared over time, whereas infection with M. bovis results in chronic, progressive, cavitary disease leading to death. Because of the innate resistance of commercial rabbits to M. tuberculosis, 320 to 1,890 log-phase, actively growing inhaled bacilli were required to form one grossly visible pulmonary tubercle at 5 weeks. The range of inhaled doses required to make one tubercle allows us to determine the relative pathogenicities of different strains. Fewer inhaled organisms of the M. tuberculosis Erdman strain were required than of M. tuberculosis H37Rv to produce a visible lesion at 5 weeks. Furthermore, with the Erdman strain, only 7 of 15 rabbits had healed lesions at 16 to 18 weeks; among the other animals, two had chronic, progressive cavitary disease, a phenotype usually seen only with M. bovis infection. Genotypic investigation of the Erdman strain with an H37Rv-based microarray identified gene differences in the RD6 region. Southern blot and PCR structural genetic analysis showed significant differences between M. tuberculosis strains in this region. Correlation of the relative pathogenicity, including disease severity, in the rabbit model with the strain genotype may help identify stage-specific M. tuberculosis genes important in human disease.Tuberculosis continues to be a leading cause of infectious disease mortality. Because of the complex pathogenesis of the disease, the development of animal models for specific stages of disease such as latency and cavitation remains a priority. The murine model is the most widely used animal model because of its economy, the extensive characterization of inbred strains, and the commercial availability of immunologic reagents (31). The guinea pig is another well-researched model of tuberculosis and has the advantages of remarkable susceptibility to low doses of aerosolized Mycobacterium tuberculosis and the development of a strong delayed-type hypersensitivity response (11,36,37,40).The rabbit model offers certain advantages over both the murine and guinea pig models. First, when infected with M. tuberculosis or Mycobacterium bovis, rabbits have a spectrum of disease that represents many of the specific stages of human disease. In general, rabbits are able to contain disease caused by virulent M. tuberculosis. Over time, the number of pulmonary bacilli decline and the lesions regress (22). With M. bovis infection, rabbits form chronic fibrosing pulmonary cavities (8). Both of these are prominent features in human disease. Finally, rabbit lung granulomas, with their caseous centers, closely resemble the human granuloma. Lurie and colleagues have found a remarkable similarity between the spectrum of rabbit tuberculosis and that found in humans (23).In the era before genomics and before the biochemical property differences were elucid...

SeptiCyte LAB appears to be a promising diagnostic tool to complement physician assessment of infection likelihood in critically ill adult patients with systemic inflammation. Clinical trial registered with www.clinicaltrials.gov (NCT01905033 and NCT02127502).

Artificial airway suctioning is a key component of airway management and a core skill for clinicians charged with assuring airway patency. Suctioning of the artificial airway is a common procedure performed worldwide on a daily basis. As such, it is imperative that clinicians are familiar with the most-effective and efficient methods to perform the procedure. We conducted a systematic review to assist in the development of evidence-based recommendations that pertain to the care of patients with artificial airways. From our systematic review, we developed guidelines and recommendations that addressed questions related to the indications, complications, timing, duration, and methods of artificial airway suctioning. By using a modified version of the RAND/UCLA Appropriateness Method, the following recommendations for suctioning were developed for neonatal, pediatric, and adult patients with an artificial airway: (1) breath sounds, visual secretions in the artificial airway, and a sawtooth pattern on the ventilator waveform are indicators for suctioning pediatric and adult patients, and an acute increase in airway resistance may be an indicator for suctioning in neonates; (2) as-needed only, rather than scheduled, suctioning is sufficient for neonatal and pediatric patients; (3) both closed and open suction systems may be used to safely and effectively remove secretions from the artificial airway of adult patients; (4) preoxygenation should be performed before suctioning in pediatric and adult patients; (5) the use of normal saline solution should generally be avoided during suctioning; ( 6) during open suctioning, sterile technique should be used; (7) suction catheters should occlude < 70% of the endotracheal tube lumen in neonates and < 50% in pediatric and adult patients, and suction pressure should be kept below -120 mm Hg in neonatal and pediatric patients and -200 mm Hg in adult patients; (8) suction should be applied for a maximum of 15 s per suctioning procedure; 258RESPIRATORY CARE FEBRUARY 2022 VOL 67 NO 2(9) deep suctioning should only be used when shallow suctioning is ineffective; (10) routine bronchoscopy for secretion removal is not recommended; and (11) devices used to clear endotracheal tubes may be used when airway resistance is increased due to secretion accumulation.

PurposeAsthma is a chronic inflammatory disease of the airways, and is associated with upregulation of phospholipase A2 (PLA2), the enzyme that hydrolyzes phosphatidylcholine, producing lysophosphatidylcholine (LPC) and free fatty acids. LPC is a lipid mediator with known pro-inflammatory and pro-atherogenic properties, and is believed to be a critical factor in cardiovascular diseases. We postulate that asthmatic subjects have an elevated content of LPC in the lung lining fluids.MethodsEight non-asthmatic controls and seven asthmatic subjects were recruited for broncho-alveolar lavage fluids (BALF) collection for analysis of LPC by high performance liquid chromatography-tandem mass spectrometry.ResultsLPC16:0 and LPC18:0 were significantly elevated in the BALF of asthmatics with impaired lung function characteristic of moderate asthma, but not mild asthma. The increased LPC content in BALF was accompanied by increased PLA2 activity. Furthermore, qRT-PCR analysis of the BALF cell fraction indicated increased secretory PLA2-X (sPLA2-X).ConclusionsThe increased LPC content in the lung lining fluids is a potential critical lipid mediator in the initiation and/or progression of airway epithelial injury in asthma.

We developed a seven-analyte plasma biomarker panel able to identify benign nodules, otherwise deemed indeterminate, with a high degree of accuracy. This panel may have clinical utility in risk-stratifying screen-detected lung nodules, decrease unnecessary follow-up imaging or invasive procedures, and potentially avoid unnecessary morbidity, mortality, and health care costs.