Don’t Swim in the Pool<br />Patrick Racine<br />SiddarthSanthebennur<br />
Background <br />Several cases of skin rash infections reported at Hotel A in Bangor, Maine<br />Feb. 18-27, 2000<br />Infections related to low chlorine levels in the pool and hot tub<br />>1.0 mg/L, less than state required 1-3 mg/L<br />Sample of unknown pathogen taken from draining ear of 6 year old child and the pool filter<br />
Patient History<br />9 patients infected<br />Had rash for 7 days (or less) or an outer ear infection<br />All had spent time in either the pool or hot tub<br />7 spent time in both<br />
Possible Culprits<br />Originally there were 6 potential bacteria that could have caused the infections:<br />Escherichia coli<br />Pseudomonas aeruginosa<br />Salmonella enterica<br />Staphylococcus aureus<br />Streptococcus pyogenes<br />Haemophilusinfluenzae<br />
Gram Stain<br />A Gram stain differentiates bacteria based upon properties of their cell walls using a crystal violet stain<br />Separated into 2 categories: <br />Gram-positive (+) (dark blue/violet)<br />Gram-negative (-) (red/pink)<br />E. coli and S. aureus were Gram stained along with unknown bacteria for comparative reasons<br />
Results of Gram Stain<br />Gram stain showed that the unknown bacteria is Gram-negative<br />Due to its red/pink color<br />This eliminates 2 bacteria from being considered the cause of the outbreak<br />Staphylococcus aureus<br />Streptococcus pyogenes<br />Both are Gram positive<br />
Differential/Selective Media<br />Two types of growth media used to inhibit or isolate growth of a microorganism<br />Differential: Different microorganisms grown on the same media; distinguished by how each organism reacts to specific dyes and chemicals placed on media<br />Selective: Allows growth of specific organism, inhibits others<br />
Type of Growth Media Used<br />Two options:<br />MacConkey’s Agar<br />Mannitol Salt Agar<br />Because the suspect bacteria is Gram-negative, the best option was the MacConkey Agar<br />Allows for growth of Gram-negative bacteria and inhibits the growth of most Gram-positive bacteria<br />
Determining the Culprit Bacteria<br />At this point, there were still four potential culprits remaining:<br />Escherichia coli<br />Pseudomonas aeruginosa<br />Salmonella enterica<br />Haemophilusinfluenzae<br /><ul><li>By using the information from the results of the growth media and research into the 4 potential bacteria, it was concluded that the culprit bacteria is Pseudomonas aeruginosa</li></li></ul><li>Pseudomonas aeruginosa<br />Rod-shaped<br />Aerobic respiration<br />Due to production of arginine, undergoes anaerobic respiration as well<br />Found in various environments including soil, water and hospitals<br />Most abundant organism on Earth<br />Opportunistic<br />Rarely infects healthy individuals<br />Prefers individuals with unhealthy immune systems<br />Resistant to many antibiotics<br />
Reasons for Selecting Culprit Bacteria<br /><ul><li>The infections occurred on the skin and outer ear, so Escherichia coli and Salmonella enterica were immediately eliminated
Escherichia coli and Salmonella enterica both cause infection of the digestive system
Although Staphylococcus aureusdoes cause various skin infections, including folliculitis, it does not cause the outer ear infection that is also associated with the culprit bacteria
This leaves Pseudomonas aeruginosa as the only logical culprit</li></li></ul><li>Antimicrobial Susceptibility<br />In order to choose a proper antibiotic to treat the infected patients, an antimicrobial test was conducted<br />The effectiveness of 6 potential antibiotics were tested on the culprit bacteria <br />Chlorampheicol<br />Gentamycin<br />Penicillin<br />Streptomycin<br />Tetracycline<br />Vancomycin <br /> Based on the results it was determined that the culprit bacteria was most sensitive to Gentamycin, making that antibiotic the best option<br />
Antimicrobial Susceptibility Test<br />The antibiotic that creates the largest zone of inhibition would be considered the most effective.<br />
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