Transcript

Lee Tetreault:

Hello and welcome to frequently asked questions from cases and infectious diseases, how the recent medical literature might influence your practice. We are joined today by Dr. Richard Hamil. Doctor, before we begin, can you provide a few key pointers for our audience from today's session?

Dr. Hamill:  

Well, a thorough review of the recent infectious disease literature can reveal a number of published studies that will have a significant impact on your clinical practice. Many of these studies fall in the category of choosing wisely, that is, doing less is better and reviewing the literature is a good exercise in having a clinician reevaluate what they are considering as standard practices.

Lee Tetreault:

Thank you Doctor. Let's now get into some of these frequently asked questions. First, what is the optimal therapy for Trichomonas vaginitis?

Dr. Hamill:  

Well, a recent study compared the Centers for Disease Control recommended one time 2g dose of Metronidazole to a seven-day course of Metronidazole of 500mg BID and it demonstrated that a seven-day course was approximately 45% more effective. Adherence to this therapy was slightly lower than a one-dose regimen by 3%. However, there was no significant differences between the two regimens in terms of adverse effects despite the longer course. Because it was significantly more effective, the seven-day course should probably be the preferred therapy.

Lee Tetreault:

What is the role of urine testing in preoperative risk assessment of patients undergoing cardiovascular, orthopedic or vascular surgical procedures?

Dr. Hamill:  

Well, there was a recently published study in JAMA Surgery in December of 2018 that evaluated this. This was a retrospective cohort study that included 68,265 male veterans who underwent surgical procedures at 109 different VA medical centers. The study did demonstrate that pre-operatives asymptomatic bacteriuria was associated with higher rates of positive urine cultures post-operatively in patients who had undergone orthopedic vascular or cardiovascular surgical procedures. However, neither preoperative antibiotic prophylaxis directed against those pathogens nor post-operative antibiotics directed against the pre-operative uropathogens prevented wound infections, UTIs or skin soft tissue infections.

This finding that asymptomatic bacteriuria should not be treated is consistent with the Choosing Wisely recommendations from the Infectious Diseases Society of America in clinical practice guidelines that were just printed a couple of months ago. Therefore, it is prudent and cost-effective to refrain from obtaining pre-operative urine analyses or cultures in patients undergoing major surgical procedures.

Lee Tetreault:

Is pre-exposure prophylaxis for HIV appropriate in patients with substance abuse?

Dr. Hamill:  

Well, people have always worried that it wouldn't be effective because these patients would not take their PrEP. However, a study that was published in 2018 in Emerging Infectious Diseases, studied whether or not pre-exposure prophylaxis with daily TRUVADA, that is Tenofovir and Emtricitabine would be effective.

We know that this drug combination has been exceptionally effective in preventing the acquisition of HIV in uninfected individuals who have sex with HIV infected persons. There is concern however, that these individuals who use illicit substance may not be as adherent to therapy as other patients and PrEP then in that situation may not be effective. This study was performed in a high risk cohort of patients in four centers in Southern California.

Baseline and ongoing substance abuse was monitored by AUDIT and DAST10 scores and tenofovir levels were assessed through levels measured by dried blood blot tests. The study showed that tenofovir levels were equivalent regardless of the amount of substance abuse by the patient. The study did show a higher level of sexually transmitted infections in substance abusers driven mostly by the use of poppers. The study did not assess acquisition of HIV infection.

The authors concluded that individuals who abuse substances are still good candidates for PrEP but should be monitored for sexually transmitted diseases on a regular basis.

Lee Tetreault:

Do immunosuppressive opioids pre-dispose to community-acquired pneumonia?

Dr. Hamill:  

Well, some opioids for instance, morphine are thought to be more immunosuppressive than others, such as oxycodone. They impair innate and adaptive immune responses to bacterial pathogens, they suppress cough and respiratory function, they inhibit mucus secretion and they impair alveolar PMN responses to bacteria. In order to study this, the authors performed a nested case-controlled study using data from patients enrolled with the veterans aging cohort study from January 2000 to December 2012.

They matched these patients with community-acquired pneumonia to patients without community-acquired pneumonia. The doses of prescribed opioids were assessed. The authors found that immunosuppressive opioids were more likely to be associated with community-acquired pneumonia than non-immunosuppressive opioids and higher doses were more than three times likelier to be associated with community-acquired pneumonia. This relationship held for both HIV infected and non-HIV infected patients.

Lee Tetreault:

How should you approach antibiotic therapy in a patient who reports a penicillin allergy?

Dr. Hamill:  

Well, about one-third of patients report some kind of a drug allergy, penicillin being the most frequent at 5%-16%. This affects future prescribing of sometimes life-saving antibiotic therapy. Following formal penicillin allergy testing by an allergist, approximately 95% of these patients do not have a true allergy. The study that addressed this was published in The British Medical Journal in June of 2018. This study was a population-based matched cohort study done in the United Kingdom general practices and it looked at the risk of incident methicillin-resistant Staphylococcus aureus or Clostridioides difficile acquisition in patients with reported penicillin allergy and compared to patients who did not report a penicillin allergy.

Patients who reported a penicillin allergy were 69% more likely to acquire MRSA and 26% more likely to acquire C.difficile. This result was driven by the more frequent use of alternative beta-lactam antibiotics such as clindamycin, which was 3.8 times more frequent, macrolides which were 4.15 times more frequent and fluoroquinolones, which were 2.1 times more frequent. The authors argue that patients who report a penicillin allergy might be considered for a more formal penicillin allergy assessment before prescribing non-beta-lactam antibiotics.

Lee Tetreault:

How should you treat and work up uncomplicated cellulitis?

Dr. Hamill:  

Well, multiple clinical entities can mimic cellulitis and the treatment differs among them. Two studies from the same dermatology group at The Massachusetts General Hospital examined optimal evaluation of patients with suspected cellulitis. In the first study, 175 participants were randomized to receive either standard care or early dermatology consultation. The primary outcomes were length of hospital stay and duration of IV antibiotic therapy. Overall, there was no difference in length of hospital stay. However, the duration of IV antibiotic therapy was significantly different between the two arms, with the consultation arm having a 13.9% shorter duration of IV therapy.

In addition, total duration of antibiotic therapy was significantly shorter and clinical improvement at two weeks was significantly better in the consultation group. The rate of misdiagnosis of cellulitis in the intervention group was 30.7%. Dermatology consultation can have a positive impact on therapy for patients with suspected cellulitis because up to one-third of them might not truly have cellulitis.

In the second study, they examined the role of radiographic imaging and blood cultures in the diagnosis of cellulitis. Out of 60 blood cultures obtained, only one was positive and it did not change therapy in the particular patient. 178 different radiographic imaging studies were performed, only eight of which resulted in the change of therapy, four for MRI, two for CAT scan and one for plain X-ray and one for ultrasound.

Blood cultures should not be done in patients with uncomplicated cellulitis. Radiographic studies can be helpful but should be used very judiciously, as they usually do not provide information that changes management. The Infectious Disease Society of America has suggested that blood cultures only be done in patients with neutropenic fever syndromes or who are immunosuppressed in some other situation.

Lee Tetreault:

And lastly, Doctor, when is the correct time to provide annual influenza immunization?

Dr. Hamill:  

Well, there is clear data that the effectiveness of annual influenza vaccination wanes over the influenza season, although the absolute impact of this waning is not known. The particular study under conversation here was published in Vaccine in 2018. It used mathematic modeling to study the effect of changing the timing of vaccination by estimating the percentage change to the current disease burden and calculated the estimated optimal week to begin vaccination during the flu season. The investigators made a couple of assumptions. The first was that vaccine effectiveness waned over 26 weeks or the second assumption was that vaccine effectiveness waned over 52 weeks.

Using data from all the influenza seasons from 2010, 2011 through 2015, 2016, they found that for the more rapid waning assumption, that was less than 26 weeks, the estimated optimal time to begin vaccination varied between early September to mid-November. Using the more conservative waning estimate over less than 52 weeks, the estimated optimal time to begin vaccinations varied between mid-August and mid to late October.

This strategy resulted in 0.44 to 5.11 additional disease burden prevented. Given the large number of at-risk patients, a strategy of delaying vaccination could result in a significant impact and disease burden. Clinicians have to weigh this data with the benefits of vaccinating individuals when you see them in the office and not delaying where there could be potential missed opportunities.

Lee Tetreault:

Thank you Doctor, this is great information, we appreciate your time today.