Saying the word “meningitis” is a sure-fire way to scare parents of young children or college students. Invasive infections caused by Neisseria meningitidis are rare but serious. Mortality rates can run around 15%; complications include amputations due to tissue necrosis and hearing loss. In short, N. meningitidis infections are nothing to mess around with.
In order to avoid death and extremity loss, the infection needs to be diagnosed early. Trouble is, the early symptoms can be similar to those of a run-of-the-mill viral infection. Some patients do not exhibit the elevated white blood cell count so common in bacterial infections. Without clear signposts to guide the way, how can clinicians catch this fast-moving infection early in its course? A handful of esoteric hematology parameters might hold the key.
Demissie et al recently published this paper in The Pediatric Infectious Disease Journal about using neutrophil counts to diagnose meningococcal infection in children. It’s behind a paywall, but here’s the gist:
-Your automated hematology analyzer needs to report immature white blood cells.
-Using total white blood cell (WBC) counts or total neutrophil counts alone is insufficient.
-The parameters to check are absolute neutrophil count (ANC), immature neutrophil count (INC), and immature-to-total neutrophil ratio (ITR).
-Patients with invasive meningococcal infection (or, the authors also say, a serious bacterial infection) display abnormalities in at least one of the three parameters.
What do you think about these guidelines? Do you think they’d be effective in diagnosing invasive meningococcal infections?
Using light scattering technology to identify bacteria has been around for a few years (as evidenced by this paper from 2009 and this article from 2006. The methodology described in these articles use actual bacterial colony growth on conventional media for identification. This only shaves a day off turnaround time. This is handy, but can we do any better?
Enter Alifax SPA. They claim to have an automated analyzer capable detecting the presence of pathogenic bacteria, quantifying (in CFU/ml) that bacteria, and measuring the drug resistance of that organism in a few hours by using light scattering technology. Those techs that have worked in hematology or urinalysis are no stranger to this type of analyzer, but how well does it translate to the world of microbiology?
Does anyone have any experience with the HB&L or the Alfred 60? How do you feel about these analyzer? Do you like this much automation in the microbiology laboratory? Let us know in the comments.
Recently officials determined the cause of death of a young mother in Las Vegas: tuberculosis. The family Mycobacteriaceae contains several pathogenic species, including the most famous, M. tuberculosis. While none of the articles I read mention the species, they do mention the patient consumed unpasteurized dairy products, which leads me to believe she died of the zoonotic organism M. bovis.
Since these organisms are recovered infrequently, clinical microbiologists should brush up on the basics of these organisms on occasion. The CDC has some general information on Tuberculosis; the illustrious contributors at Wikipedia go a bit more in depth. The best sources for information are reference textbooks such as the Manual of Microbiology. It’s important to remember that mycobacteria can infect any region of the body, not just the respiratory system, so it’s important to keep an open mind. It’s also helpful to know that some species are rapid growers and may present on blood agar in a routine culture.
The shutdown has far-reaching implications for your health.
The government-funded Centers for Disease Control employs detectives that investigate foodborne illnesses, infectious disease outbreaks, and influenza viral patterns. They work hard to keep us healthy and productive. You know what happens when the government shuts down? They stop detecting. Development of next year’s flu vaccine gets delayed. Flu outbreaks aren’t tracked. Right now, there’s a Salmonella outbreak that isn’t being investigated as thoroughly as it would be if the CDC were open for business. (If you’re interested in the CDC’s role in outbreak investigation, that link is here.)
The Superbug blog has a great post about the government shutdown and your health.
Nanosphere’s motto is “advancing diagnostics through the power of nanotechnology.” While I’ve read enough science fiction to quibble with the “nanotechnology” designation, Nanosphere does seem to have a handle on rapid molecular testing. The Verigene System can analyze samples for respiratory viruses (Influenza A, Influenza B, RSV, and 2009 H1N1, to name a few), C. difficle, and gram-negative or gram-positive organisms in positive blood culture bottles.
While other rapid molecular analyzers exist for C. difficle and respiratory viruses, I’m intrigued by the blood culture analysis. Literature from the company claims that analyzing one sample using one cartridge can give you identification and resistance information for organisms commonly implicated in septicemia. With the rising prevalence of multidrug resistant bacteria such as MRSA, CRE, and Acinetobacter baumanii, getting these results almost two days faster than current methodologies would have a positive impact on patient care.
A recent study suggests that this system does what it claims to do–rapidly identify organisms and resistance patterns in positive blood cultures.
Have any of you tried this system? If so, what are your thoughts?
While I was out of the office last week, Maryn McKenna wrote up a few informative blog posts about the CDC’s threat report.
The first summarizes the lengthy report (114 pages) by highlighting the top three “urgent” threats–CRE, N. gonorrhoeae, and C. difficle. She also mentions that CDC’s director Dr. Tom Frieden states “If we are not careful, we will soon be in a post-antibiotic era. And for some patients and for some microbes, we are already there.”
Another post discusses the connection between agricultural antibiotic use and bacterial resistance in humans.
As an aside, if you’re as much of an emerging disease junkie as I am, check out McKenna’s blog on a regular basis. She’s also written a book on MRSA that should be required reading for all clinical microbiologists. It’s one part history, one part science lesson, and one part cautionary tale about this bacterium.