Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Example: Abstract: Some patients converted from ventricular fibrillation to organized rhythms by defibrillation - trained ambulance technicians(EMT - Ds) will refibrillate before hospital arrival.The authors analyzed 271 cases of ventricular fibrillation managed by EMT - Ds working without paramedic back - up.Of 111 patients initially converted to organized rhythms, 19(17 % ) refibrillated, 11(58 % ) of whom were reconverted to perfusing rhythms, including nine of 11(82 % ) who had spontaneous pulses prior to refibrillation.Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not(53 % versus 76 % , P = NS), although discharge rates were virtually identical(37 % and 35 % , respectively).Scene - to - hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome.Defibrillation - trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back - up is not available.
Example solution: Ventricular Fibrillation
Example explanation: This term is directly present in the abstract and it is one of the main topic in it. So can be chosen as the medical subject heading.

Problem: Abstract: Yersinia enterocolitica was cultured from feces of 122 symptomatic adults in a single facility using selective culture media; all isolates were confirmed in an independent reference laboratory. Of 128 isolates, multiple serotypes were defined and all were biochemically typical for Yersinia enterocolitica. Other agents were seen in 20 patients; of these, seven were Yersinia fredriksenii and six were Clostridium difficile. Diarrhea (80%) and abdominal pain (64%) were common, whereas other features such as fever (9%) and bloody stools (8%) were unusual. Use of antibiotics (24%) or opiates (28%) in the month before culture was common. The terminal ileum was seen radiographically in 20 patients, but only two barium studies showed abnormalities. Fiberoptic endoscopy and biopsy studies, done in greater than 50% of the cases, showed minimal or no changes in most patients. However, 3 patients had pseudomembranous colitis with concomitant Clostridium difficile cytotoxin and 7 had diffuse severe colitis. New culture techniques, and possibly geographic differences, have contributed to the high isolation rates of this organism. Yersinia enterocolitica occurs sporadically, involves a variety of serotypes, and is associated with a broader clinical spectrum than was formerly appreciated.
Solution: Adolescence