The Human Microbial Cloud- Infection Prevention Issue?

This intriguing article was recently forwarded to me.

It is generally accepted that the dissemination of microbes between humans and the inanimate environment can occur through direct contact with surfaces or through airborne release. This last mechanism is very poorly understood. 

The investigative team used 16S rRNA gene sequencing to characterize the airborne bacterial contribution of a single persons sitting in a sanitized custom experimental climate chamber. This was compared to air sampled in an adjacent, identical, unoccupied chamber (control room) as well as supply and exhaust air sources. 

Next, and this is where things really get clever, the microbial burden in settled particles surrounding each occupant was assessed and characterized. 

The results suggests that we shed particles and bacteria in our own distinct and unique way, almost like a bacterial fingerprint. Basically, an occupied space is different microbiologically from an unoccupied space and each participant had their own, distinct microbial cloud.

To me this underscores the dynamic yet still poorly understood mechanism in which we interact with the inanimate environment. Although the bacteria isolated were largely not pathogenic, we certainly cannot exclude that patients colonized or infected with a pathogen will not emit their own 'pathogenic' microbial cloud. The extent to which microbial clouds drive hospital acquired infections is largely unknown.

Until we know better, it may still come down to acknowledging that the inanimate environment is a potential reservoir of hospital pathogens and to employing common sense infection prevention mechanisms to minimize bioburden, such as washing our hands, chlorhexidine bathing patients and performing robust daily and terminal disinfection of hospital rooms.

UCI World Road Championships in Richmond, VA: At VCU Health

It is not often that the UCI Road World Championships are in the USA, let alone 50 feet in front of the VCU Health Infectious Diseases Clinic.

Below are a couple of snaps from yearly today.

Whoosh.

View from exam room- VCU ID Clinic, Broad Street, Richmond, VA

Lead riders turning the corner at Governor's Hill and Broad Street, Richmond, VA

Sprint to the finish line- Broad Street,  Richmond, VA

Front of the peloton,  Broad Street, Richmond, VA

The peloton arrives, Broad Street, Richmond, VA

Chlorhexidine Impregnated Dressings for Central Venous Catheters- Infection Prevention Benefit

Well, this one seems like old news. Regardless, it was nice to see this review published by the Cochrane Database. The citation is found here.

For the remaining laggards and naysayers, the data resoundingly supports the use of chlorhexidine impregnated dressings over central lines to prevent central line associated bloodstream infections.

Sadly, even with this data, medication impregnated dressings for central lines are not always the standard of care, particularly after patients are discharged on home IV therapy or to long term care / transitional care centers. I routinely see non-impregnated dressings on central lines at the time of outpatient follow up.

The message is clear. Request medication impregnated dressings for central lines and be vigilant and vocal for their continued use in patients with central venous catheters, particularly after hospital discharge.

Acute HIV Infection- Clinical Symptoms Are Not Reliable

If clinicians feel that they can rely on typical symptoms of acute HIV infection to trigger an HIV PCR test for diagnosis, think again.

Here is a intriguing read published in Clinical Infectious Diseases this month. The investigators review 290 patients (271 males) with primary HIV infection- seroconversion. The majority (70%) had typical symptoms of acute HIV infection, including fever. A significant chunk, 30%, manifested no fever and had atypical presentations, including non-specific neurologic ( encephalitis, prolonged vertigo, paresthesias) and gastrointestinal symptoms (diarrhea, tonsillitis, severe gastritis).  In the study cohort, only in 112 (38%) patients was HIV infection suspected during the first medical attendance. Opportunities to diagnose HIV were missed

The utility of a clinical evaluation to rule out acute HIV infection is limited. 

To me, the message is clear: have a low threshold to test for HIV.

The Richard P. Wenzel Academic Infectious Diseases Consult Service at VCU Medial Center

The ID service at VCU Medical Center has grown by leaps and bounds. 

We now have two general infectious diseases consult services, along with Orthopedic ID and Transplant ID.

Today we officially launched the The Richard P. Wenzel Academic Infectious Diseases Consult Service,  our primary general ID Consult Service, in honor of one of the profession's greatest, modern day infectious diseases specialist.

For more on Dr. Wenzel, click here.

More pictures from the event will be forthcoming.

Congratulations Dr. Wenzel!

Penicllin Allergy and MSSA Bacteremia- Time to (at least) Take a Proper Allergy History

At a recent infectious diseases case conference at Virginia Commonwealth University we were discussing the mislabeling of penicillin allergy for patients needing staphylococcal coverage. Many people claim  that they are penicillin allergic, commonly resulting in the reflexive prescription of vancomycin for the management of gram positive infections.

Fortuitously, this article popped up in the literature.


Using mathematical modeling the authors simulated 3 strategies: (1) no allergy evaluation, treat with vancomycin (2) allergy history-guided treatment: if history excludes anaphylactic features treat with cefazolin and (3) complete allergy evaluation with history-appropriate PCN skin testing: if skin test negative, treat with cefazolin . Model outcomes included 12-week MSSA cure, recurrence, and death; allergic reactions and adverse drug reactions.

The use of vancomycin results in the fewest patients achieving MSSA cure and the highest rate of recurrence. In brief- vancomycin yields the poorest outcomes. The exclusion of a true allergy either by history or skin testing is preferred over simply prescribing vancomycin for MSSA bacteremia.

At the very least, when managing invasive staphylococcal infections, when informed of a penicillin allergy, this should be further addressed and not simply accepted as true as it impacts both choice of therapy outcome. 

It all comes back to taking a good history, as were taught in Practice of Medicine 101.

Chlorhexidine Bathing- The Saga Continues

Here is an article on pre-surgical chlorhexidine bathing that it of interest. The abstract can be accessed here.

The authors conducted a randomized prospective analysis in 120 healthy volunteers was conducted using a standardized process of dose, duration, and timing of 4% chlorhexidine gluconate applied during preoperative showering. The volunteers were randomized to 2 chlorhexidine gluconate, 4%, showering groups (2 vs 3 showers), containing 60 participants each, and 3 subgroups (no pause, 1-minute pause, or 2-minute pause before rinsing), containing 20 participants each. Volunteers used 118 mL of chlorhexidine gluconate, 4%, for each shower. Skin surface concentrations of chlorhexidine gluconate were analyzed.

The findings? 

A standardized preadmission shower regimen that includes 118 mL of aqueous chlorhexidine gluconate, 4%, per shower, with a minimum of 2 sequential showers; and a 1-minute pause before rinsing results in maximal skin surface concentrations of chlorhexidine gluconate. This concentration  (16.5 µg/cm2) is sufficient to inhibit or kill potential surgical wound pathogens.

Although surgical infection outcomes were not assessed, the findings suggest that pre-operative chlorhexidine bathing must be formalized and clearly protocolized with easy to use instructions in order to result in adequate antibacterial effect. 

This remains a work in progress.