This week in lab I was given cultures from several types of infections including an eye and a burn. The eye specimen was plated on SBA and Chocolate agar. There were 2 isolates growing on the chocolate plate however only 1 isolate growing on SBA. The isolate that grew on both plates was white, opaque and non hemolytic and after performing a catalase and staphaurex test it was confirmed as coagulase negative Staphylococcus. Because one of the isolates only grew on chocolate, I suspected Haemophilus sp. I performed a Haemophilus ID plate and there was growth only in the quadrant that had both X and V factors and in the quadrant with horse blood. This confirmed the pathogen as Haemophilus influenzae. H. influenzae is a common cause of conjunctivitis, especially in children.
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| Haemophilus influenzae on chocolate agar |
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| Conjunctivitis |
The burn specimen was plated on Mac and SBA as well as grown in thio broth. I preformed a gram stain of the thio broth and there were numerous gram negative straight rods as well as gram positive cocci in chains. Only one isolate grew as clear colonies on Mac which means the gram negative rod is a non lactose fermenter. This same isolate on SBA showed typical colony morphology of Pseudomonas aeruginosa so I performed a spot indole and oxidase. Both were positive which confirmed the isolate as Pseudomonas aeruginosa. The second isolate only grew white opaque beta hemolytic colonies on SBA. The catalase test was negative so I performed a PathoDx strep grouping test. The organism agglutinated with the Streptococcal group C antigen which confirmed the identity of the isolate as Streptococcus dysgalactiae subsp. equisimilis. Streptococcus spp and Pseudomonas are both common causes of infections seen in burn victims. For all of you with weak stomachs who scream at Mrs. Jeff for her pictures, I'll spare you a picture of a Pseudomonas infection in a burn victim.
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| Typical colony morphology of Pseudomonas aeruginosa on SBA |
Not that finding any of these bugs on anyone is a good thing, but my favorite by far is Pseudomonas aeruginosa! :) It's always so pretty and smells so good. It makes me think of Dimetap that I used to take when I was little. It's definitely one of the easiest ones to identify, too.
ReplyDeleteI know we were warned coming into this program we were going to start thinking we had every organism/illness we talk about in class but I think I just realized I had conjunctivitis and wrote it off. I need to be more careful about just dismissing symptoms, especially since we have the opportunity to culture it for ourselves.
ReplyDeleteWhat a coincidence, we both had the same specimens for our burn and eye specimens.
ReplyDeleteWe also did an abscess culture which was plated on Mac, SBA, BBE (ANA), PEA (ANA), BAP (ANA), and THIO. Based on colony description from my media and Gram-stain results from the THIO, my presumptive ID was Staphylococcus sp., NLF GNB, and Bacteroides fragilis group. For isolate 1, the results of the tests were Catalase-positive and Staphaurex-positve, which the organism turned out to be Staphylococcus aureus. For isolate 2, the test results turned out to be Oxidase-negative, Spot indole-negative, and Crystal E/NF results were on an attached sheet. Isolate 2 was identified as Acinetobacter baumannii. For isolate 3, the test results for this organism were Catalase-positive, Indole-negative, and the Gram-stain was pleomorphic Gram-Negative rods. The final identification for isolate 3 was Bacteriodes fragilis.