Mycoplasma pneumoniae as a cofactor in severe respiratory infections. Clin. Infect. Dis

We report the clinical events associated with severe bacterial or viral infections in four patients whose illnesses followed or coincided with acute Mycoplasma pneumoniae respiratory infection. We propose that M. pneumoniae has the ability to act as a cofactor in severe respiratory disease by facilitating alterations in local respiratory immunity or structure and function. Mycoplasma pneumoniae is recognized as an important and frequent cause of community-acquired respiratory illness in children The role of M. pneumoniae as a cofactor in severe pulmonary infections is not well understood; neither are the details of the pulmonary immunologic events that occur during the course and after the resolution of M. pneumoniae infection in humans. We report the clinical events that occurred in four patients who had severe bacterial or viral infections that appear to have either followed or coincided with M. pneumoniae respiratory infection. Case Reports Clinical and laboratory data for our patients are summarized in table 1. Patient I. A 14-year-old male with respiratory failure was transferred to our hospital. He had previously been well except for recurrent ear infections in early childhood. His respiratory illness began 5 weeks earlier with the onset of a sore throat and an earache. A primary care practitioner found evidence of suppurative pharyngitis and bilateral otitis, and oral penicillin was prescribed. The patient's illness progressed to include a persistent cough that did not abate despite courses of co-trimoxazole and cefaclor. Four days before his transfer, the patient became nauseated and anorexic. The severity of his cough increased, and he was noted to be febrile. He complained of left-upper-quadrant pain, and his cough precipitated both frontal chest pain and back pain. Two days before transfer, he was admitted to another hospital with the diagnosis of left-lower-lobe pneumonia. Intravenous ampicillin was administered. Over the next 24 hours, he became grossly dyspneic and was found to have a Po e of 30 mm Hg while breathing room air. The patient underwent bronchoscopy, and he was intubated and transferred to our hospital, where clinical and radiological evidence of bilateral lower-lobe bronchopneumonia was found. He was ventilated. Vital signs included the following: temperature, 38.2°C; pulse, 120/min; and blood pressure, 120/60 mm Hg. There were no other signs of infection in areas other than the respiratory tract. Radiographs of the chest also revealed small bilateral pleural effusions. The patient's WBC cell count was 9.3 X 109/L (74% polymorphonuclear cells). Blood cultures were negative. Routine cultures of bronchial washings did not yield pathogenic bacteria. Special studies for legionellae and chlamydiae were unrevealing. Respiratory syncytial virus was evident in these washings on both direct immunofluorescence staining and tissue culture. An IgM anti-P1 M. pneumoniae immunoblot assay was strongly positive Intravenous erythromicin and cefuroxime were administered, as was aerosolized ribavirin. The patient was ventilated for 7 days, and although his high fever (temperature, 38°-40°C) started to remit by day 4 after admission, he had mild pyrexia for 12 days. He was transferred back to his referring hospital in considerably improved clinical condition. Patient 2. A 10-year-old male was admitted to the hospital with fever and cough. He had been well until 3 weeks before admission, when he developed a nonproductive cough, fever, and night sweats. Within the first week of his illness, his cough became productive and he complained of mild exercise intolerance. The patient defervesced after 2 weeks, but he experienced episodic right shoulder and subscapular pain during episodes of cough. Three days before admission, he became febrile again and his cough became more productive. The patient was admitted to our hospital. Vital signs included the following: temperature, 38.7°C; pulse, 100/min; respiraat Penn State Universit

Effects of simulated light regimes on gene expression in Antarctic krill (Euphausia superba Dana)

A change in photoperiod has been implicated in triggering a transition from an active to a quiescent state in Antarctic krill. We examined this process at the molecular level, to identify processes that are affected when passing a photoperiodic threshold. Antarctic krill captured in the austral autumn were divided into two groups and immediately incubated either under a photoperiod of 12 h light:12 h darkness (LD), simulating the natural light cycle, or in continuous darkness (DD), simulating winter. All other conditions were kept identical between incubations. After 7 days of adaptation, krill were sampled every 4 h over a 24 h period and frozen. Total RNA was extracted from the heads and pooled to construct a suppression subtractive hybridisation library. Differentially expressed sequences were identified and annotated into functional categories through database sequence matching. We found a difference in gene expression between LD and DD krill, with LD krill expressing more genes involved in functions such as metabolism, motor activity, protein binding and various other cellular activities. Eleven of these genes were examined further with quantitative polymerase chain reaction analyses, which revealed that expression levels were significantly higher in LD krill. The genes affected by simulated photoperiodic change are consistent with known features of quiescence, such as a slowing of moult rate, a lowering of activity levels and a reduction in metabolic rate. The expression of proteases involved in apolysis, where the old cuticle separates from the epidermis, showed particular sensitivity to photoperiod and point to the mechanism by which moult rate is adjusted seasonally. Our results show that key processes are already responding at the molecular level after just 7 days of exposure to a changed photoperiodic cycle. We propose that krill switch rapidly between active and quiescent states and that the photoperiodic cycle plays a key role in this process