End of Semester

Well everyone, it certainly has been an enjoyable semester studying various infectious diseases. I know I have learned a lot, and I hope that everyone has learned a lot from reading my blogs. This has been a very fun project to keep up with over the summer. It allowed for me to have fun with learning more about what I found interesting in the class. I feel like I have a better understanding and now will enjoy learning more about diseases. Now that the semester is over, I will be graduating and will discontinue my blog postings. I am moving to Nashville, TN for a job at Vanderbilt University Hospital. I look forward to my career as a Medical Technologist! :)

Bite Wound Case History

 This is a case history that I wrote during clinicals on a cat bite wound. I found it very interesting and thought I would share it again. Enjoy!!!

The patient presents to the doctor with a cat bite wound to the hand with a small amount of pus accumulating from the area. There is minimal localized swelling and pain. The patient is otherwise a healthy white female. A culture is taken from wound and plated onto 5% sheep blood agar, chocolate agar, and MacConkey agar; a gram stain is performed. The gram stain results showed small gram negative bacilli. There was growth on the 5% sheep blood agar and chocolate agar but no growth on MacConkey agar. [need more information on the actual investigation/workup] The final diagnosis was an infection of Pasteurella multocida. The patient did not experience some of the typical signs such as rapid development of pain, erythema, welling, cellulitis with or without a forming abscess, and purulent drainage at wound location. The patient was prescribed Augmentin and therapeutic advice of cleaning and irrigating the wound regularly until the wound healed. The prognosis for the patient was excellent as long as the medication was completed as prescribed.

 Pasteurella multocida are small gram negative bacilli that are present in normal animal flora and is the most frequently recovered Pasteurella species. This organism can be transmitted to humans during close contact, most often an animal scratch or bite. It is estimated to infect 20-50% of the 1 to 2 million Americans bitten or scratched by cats and dogs each year. The reservior of P. multocida includes the nasopharnyx and gastrointestinal tract of wild and domestic animals. It can also be found in the upper respiratory tract normal flora in humans who are animal handlers. The infection that can occur with P. multocida is often a soft tissue wound from an animal scratch or bite but it can cause more serious problems in patients who are immunocompromised. Other problems include respiratory tract infections, endocarditis, meningitis, brain absess, eye infections, sepsis, and bacteremia. The virulence factors caused by P. multocida are an endotoxin and antiphagocytic capsule. It is designated into groups A, B, D, E, and F then divided further into somatic serotypes 1 to 16. Most isolates of P. multocida fall into group A or D, and the toxin gene, toxA, is located in a conserved region of the P. multocida chromosome. The role however of the dermonecrotic toxin in human disease is unknown. These isolates are also known to produce lipases which can also be a virulent factor to this organism.

 Although there is no specific requirements for detection of Pasteurella multocida, a gram stain of the patient specimen would be the place to start. The gram stain would show small gram negative bacilli resembling a "safety-pin" under the microscope. Wright stains and Geimsa stains can also be performed to enhance the bipolar staining of the organism. On 5% sheep blood agar, the organism appears convex, smooth, shiny, gray, and nonhymolytic with a "musty" odor. On chocolate agar, the organism appears the same only slightly larger colonies. It does not grow on MacConkey agar because it does not ferment lactose. P. multiocida is also oxidase positive and sometimes can be a weak reaction. To compensate, the oxidase reagent can be flooded on the 5% sheep blood agar or chocolate agar the organism is growing best on and wait to observe the purple color indicating a positive reaction. This organism also produces acid but no gas from glucose, sucrose, and mannitol but not from maltose or lactose. A few other tests include catalase, indole, ornithine decarboxylase, urease and nitrate reduction. P. multocida is catalase, indole, and ornithine decardoxylase positive, urease negative, and reduces nitrates to nitrites.

An unusual characteristic of Pasteurella multocida is that most are susceptible to penicillin even though gram negative rods are intrinsically resistant to penicillin. Amoxicillin/clavulanate (a beta-lactamase inhibitor/penicillin) or Augmentin is the drug of choice for an animal bite wound to provide broad-spectrum coverage due to bite infections to be polymicrobial.

Fun link! So one of my favorite shows was Friends. I found this video and reminded me of Pheobe and her famous song "Smelly Cat." Listen to this Parody!

Camp jejuni, we hold you in our ....

The Facts about Campylobacter jejuni:

Where can you find it?

You can find it in animals such as chickens (poultry), birds, cattle and household pets including dogs and cats.

What are the suspecting symptoms?

The suspecting symptoms are diarrhea (which may contain blood or mucus), fever, stomach cramps, nausea and vomiting.

How can you catch it?

After the bacteria are taken in by mouth, it usually takes between two and five days before you become ill. To trace the cause of the illness, it is necessary to know where you were and what you ate and drank in the week before you became ill.

Prevention?

The single most important step especially poultry, and avoid cross-contamination via cutting boards and utensils of raw foods such as fresh produce.  Consuming unpasteurized dairy products such as milk and cheese is a known risk factor for Campylobacter infection and should be avoided to reduce the risk of exposure to foodborne pathogens.

The Laboratory:

What does it look like?

Campylobacter jejuni is a faint gram negative rod that is curved or seagull shaped with polar flagella.

Presumptive ID?

If Campylobacter is suspected, it is grown on CAMPY agar in a microaerophilic environment at 42^oC. It is oxidase and catalase positive and under a wet prep, it shows darting motility.

Confirmatory ID?

For confirmation, a hippurate hydrolysis test will be positive for Campylobacter jejuni. To separate Campylobacter and Helicobacter, a urease test is performed which will be negative for Campylobacter. To speciate Campylobacter jejuni, it will be resistant to Cephalothin and sensitive to Nalidixic acid.

My Fun Memory Clue! --> Hope it helps!!!

At Camp jejuni, we will see purple hippos and pink seagulls darting into the foamy sea.

Funny song about bacteria and preventing some food-borne illnesses