An organism is isolated from the endotracheal tube of a patient receiving chemotherapy. The gram-negative bacillus grows on BAP and produces clear, colorless colonies on MacConkey. The isolate is non-motile, oxidase-negative, and biochemically inactive. Which of the following is the most likely organism?

Anaerobic Gram negative rods are isolated from a decubitus ulcer (bed sore) of a 70 year old patient in a nursing home facility. Below are the results on Kanamycin/Vancomycin agar (left) and BBE agar (right). Based on the information and culture results, which organism would be the likely cause of infection? KV_BBE.jpg 

Gram negative, intracellular, dipolococci are observed from a gram-stained smear taken from red papules on a 15-year-old girl who presents with fever, nausea, vomiting, and stiff neck. She later becomes lethargic and comatose. Which of the following organisms should be suspected?

 A 3  month old infant presented with persistent symptoms that include paroxysmal cough, breathing difficulty, fever and vomiting after a spasm of coughing. Cyanosis (lack of oxygen causing blue skin coloration) and intercostal retractions were noted.  The infant also had a temperature. Nasophyrngeal secretions were collected and analyzed. The image below shows the colonies recovered after 5 days from the selective medium. The organism is biochemically inert. Based on this information, the suspected agent is most likely B pertussis colonies mercury drops.jpg

Match each of the following organisms, with the situation listed below. Each agent may be selected once, more than once, or not at all.

A patient came to the ER with a severe infection of the foot. When examined, the wound emitted a strong, foul odor and there was a considerable amount of gas in the tissue. The wound was cultured and the following organism, which was gram positive, grew under anaerobic conditions an anaerobic blood agar. What organism should be suspected? DZ hemolysis.jpg

This image shows an organism isolated from a post-surgical wound infection on 5% blood agar grown in the CO(2) incubator. Based on this finding, which of the following tests would you perform to identify which organism? Colony Morphology DB4(1).jpg

A rancher shows some characteristic lesions on his face. The organisms produce aerobic, non-hemolytic, non-motile colonies. The microscopic morphology from the isolated colonies is shown below.Which of the following should be suspected? Bacillus_anthracis2Gram.jpg

Catalase negative, beta-hemolytic colonies were isolated from a wound culture taken from a 2 year-old child who presented with fluid-filled vesicles on her face. Which of the following combination of tests will identify the organism?

BONUS: List the ways in which DNA and RNA differ.