Question

sunny skies and a lurking microscope case study

Part III – The Physician
June 5th
Th ree weeks had passed. Th e swelling was still present and it had become even more diffi cult for Margo to move
her fi nger. In addition, the amount of fl uid oozing from the wound had increased, suggesting that the medication
hadn’t worked. It was now time to visit a local physician. Following the advice of a neighbor, Margo set up an offi ce
appointment with Dr. Chan, an internist. After the usual battery of questions, Dr. Chan sent in the nurse to collect
a specimen from Margo’s fi nger. Dr. Chan mentioned to Margo that the specimen would be sent off to the regional
hospital laboratory for analysis and that he would provide her with another prescription for Kefl ex, which she should
continue to take until test results came back.
June 15th
Th e test results arrived in Dr. Chan’s offi ce on June 15th and were as follows:
• No yeast or fungal elements were noted
• Gram-stain reaction: no organisms seen
• Culture of anaerobes and aerobes @48 hours yielded no growth
• Enrichment culture results: moderate growth on day 5 of an acid-fast bacterium (AFB).
o Growth identifi ed as Mycobacterium fortuitum by the Florida State Laboratory.
Armed with a microbial identifi cation, Dr. Chan prescribed Doxycycline and Bactrim to be taken for four months. Dr.
Chan also mentioned that the isolated organism was known to be found in tap water. Consequently, Margo planned
to ask her condo community why an organism that could cause so much pain would be living in the water that was
coming out of her faucets. And although she was annoyed to learn of the source of the organism, at least she could
take some comfort in the fact that she fi nally had an accurate diagnosis and that by taking her medicine she could fully
recover from her injury and start to enjoy her new home.
Questions
1. Compare and contrast aerobes and anaerobes. Why were no microbes noted upon aerobic and anaerobic
culture?
2. Investigate the properties and characteristics of M. fortuitum. Where is this organism typically found
(reservoirs)?
3. Why must the acid fast stain be performed to identify organisms of the genus Mycobacterium?
4. Why did Dr. Chan prescribe two antibiotics rather than only one?
5. How does doxycycline kill bacteria (cellular target)?
6. Why were the antibiotics prescribed for an extended period (4 months)?
7. No organisms were noted upon Gram staining, yet the enrichment culture yielded M. fortuitum after several days. Provide an explanation.

Answer 1