Suck It: The Ins and Outs of Mouth Pipetting


If you ever find yourself working in an infectious disease laboratory, whether it’s of the diagnostic or research variety, the overarching goal is not to put any microbes in your eye, an open wound or your mouth. Easy enough, right? Wear gloves, maybe goggles, work in fume hoods and don’t mouth pipette. When working with pathogenic bacteria and viruses, priority number one is Do Not Self-Inoculate.

This is obvious for anyone who has worked in a shiny biology or chemistry lab or seen an episode of CSI: Crime Scene Investigation (we’re all friends here, just admit it), but one of the most commonly used pieces of equipment in labs prior to the 1970s was the leading cause of laboratory-derived infections: the honorable pipette. How could that be possible, you ask? By using one’s oral cavity with the pipette to measure and transfer liquids.

Today our manual pipettes are rather sophisticated, plastic-y devices perfectly calibrated for moving precisely exact milliliters, microliters and picoliters of valuable solution from one vessel to another, whether it’s of a urine sample, some spare radioactive material you have lying about or toxic solvents. But before the development of cheap mechanical pipettes in the ’70s, using your mouth to pipette solutions was more than a common sight, it was a way of the lab.

Former Centers for Disease Control (CDC) parasitologist, Dr. Mae Melvin (Lt), examines a collection of test tubes while her laboratory assistant mouth pipettes a culture to be added to these test tubes. Source: David Senser/CDC.

Don’t worry, reader, I heard you tentatively whisper, “just what exactly is mouth pipetting, dare I ask?”

Like so: insert an open-ended glass capillary tube into your mouth. Place the opposite, tapered end of the tube into a solution of your choice. Microbial stews, blood, cell culture, it is totally your call. With a method that carefully mimics the sucking of a straw, draw a solution upwards through your man-made pipette to your desired volume using the tension created by the reduced air pressure – yes, suction! Maintain the tension with your mouth. Do not suck too hard and inadvertently slurp the solution into your mouth. Careful now. Gently move the pipette end from one vessel and release your precious cargo into yet another vessel.

That is mouth pipetting.

A wonderful demonstration of mouth pipetting by Dr. Armand Frappier, a microbiologist and expert on tuberculosis. Look closely: you can see him draw a dark liquid slowly towards his mouth. What could it be? Soda, a culture of TB, serum for cell cultures? You can watch the entire video clip that this GIF is based upon here. Source: Musée Armand Frapper.

The sparsity of history on pipetting techniques (itself a shocking shortcoming, I’m sure you’ll agree), forbids us from generalizing the prevalence of this phenomena. But we do know that it was the source of a ridiculous number of accidents, whether swallowing a corrosive or toxic substance or an infection with one’s research material  (1). A survey of 57 labs in 1915 found that 47 infections  were associated with workplace practices and more than 40% of those were attributed to the practice of mouth pipetting. A longitudinal study of 921 workplace laboratory infections from 1893 and 1950 found that 17% were due to “oral aspiration through pipettes or to splashes of culture fluids into the mouth (2).”

Infection through the use of one’s oral cavity was such an occupational hazard that it warranted an article, “The Hazards of Mouth Pipetting,” from two gentleman working for the U.S. Army Biological Laboratories. In 1966 they wrote,

although the use of pipettes in the early chemistry laboratories undoubtedly led to accidental aspiration of undesirable toxic and poisonous substances, the first recorded laboratory infection due to mouth pipetting occurred in 1893 … [with] the case of a physician who accidentally sucked a culture of typhoid bacilli into his mouth …

compared with the equipment and procedures required to avoid other types of microbiological laboratory hazards, the method of avoiding pipetting hazards is so elementary, so simple, and so well-recognized that it seems redundant to mention it [emphasis added by author]. However, continued accidents and infections in laboratories illustrate, even today, that there is a lack of acceptance of the simple precautionary measured needed (2).

By the 1970s, mouth pipetting had fallen out of favor as swanky, mechanically adjustable and cheap pipettes flooded the market (3). They were not only infinitely safer but also far more accurate. Instead of drawing a semi-approximate volume of solution with the imperfect measuring device that is your mouth, standardized and calibrated pipettes were available that could zip up a solution to one’s desired volume. More precision. Better experimental results. Less contamination. More ergonomic. Fewer infections. Nowadays, mouth pipetting is explicitly banned from laboratories.

A woman mouth pipetting to select specimens of ectoparasites. Source: National Library of Medicine

And, indeed, you might think that this old school technique is thankfully old news and good for a giggle but mouth pipetting is still practiced in some countries. A study looking at the lab practices and biosafety measures of Pakistani lab technicians found that mouth pipetting was reported by 28.3% technicians (4). This paper was published just last year, in August of 2012. Another study in 2008 found that Nigerian technicians working in clinical laboratories were not only improperly vaccinated against many of the preventable diseases that they were testing for (!) as well as eating and drinking in the lab but 1 in 10 also reported mouth pipetting (5).

Lest you think this is just happening in developing countries, be rest assured that American teenagers and young adults will always find a creative way to  jeopardize their health. In 1998, a 19-year-old nursing student in Pennsylvania was  hospitalized for several days following infection with a unique strain of Salmonella paratyphi she was working with in a lab; the case report strongly suggests that mouth pipetting was the culprit behind this particular microbial misadventure (6).

Another article from 1995 assessing lab accidents found that 13% of laboratory-acquired infections were a result of mouth pipetting. That’s 92 accidents attributed to someone in a lab deliberately putting a pipette or capillary tube into their mouth and sucking up some solution laden with microbes (7). Clearly, we still have a way to go in dissuading people to stop using pipettes as straws.

A techician mouth-pipetitng environmental water samples in Malta. Image: E Mandelmann. Source: History of Medicine

A technician mouth pipetting environmental water samples in Malta. Image: E Mandelmann. Source: History of Medicine

Mechanical manual pipettes have been a godsend to technology and the sciences, saving researchers time and resources in measuring and transferring liquids. Pipettes now serve as an icon of the scientific pursuit of knowledge – we’re all familiar with the close up of the gloved hand and pipette tip hovering over some glowing liquid. It’s banal, efficient and ubiquitous. It’s the dogged, unsung hero of the lab but there were several decades when our method of pipetting was also a microbial misadventure in the waiting.


“There are reports of laboratory infections by means of the pipette with quite a variety of microorganisms. In the intestinal group: typhoid, Shigella, salmonella, cholera; among others, anthrax, brucella, diphtheria, hemophilus iniluenzae, leptothrix, meningococcus, Streptococcus, syphilis, tularemia; among viruses, mumps, Coxsackie virus, viral hepatitis, Venezuelan equine encephalitis, chikungunya, and scrub typhus.” Download this neat article on the history and epidemiology of lab-acquired infections here.

Want to see more pictures of mouth pipetting? Of course you do! I’ve been collecting them on the Body Horrors tumblr here, here, here, here and here. Here’s a sign. And here’s a riff on a meme.


1) AG Wedum. (1997) History and epidemiology of laboratory-acquired infections. J Am Bio Safety Assc. 2(1): 12-29

2) Phillips GB &Bailey SP (1966) Hazards of mouth pipetting. Am J Med Technol. 32(2): 127-9

3) JA Martin (April 13, 2001) The Art of the Pipette BiomedNet Magazine100

4) S Nasim et al (2012) Biosafety perspective of clinical laboratory workers: a profile of Pakistan. J Infect Dev Ctries. 6(8): 611-9

5) FO Omokhodion (1998) Health and safety in clinical laboratory practice in Ibadan, Nigeria. Afr J Med Med Sci. 27(3-4): 201-4

6)B Boyer et al (1998) The microbiology “unknown” misadventure. Am J Infect Control. 26(3):355-8

7) DL Sewel (1995) Laboratory-Associated Infections and Biosafety. Clin Micro Rev. 8(3): 389-405
HILL, N. (1999). Laboratory-acquired Infections: History, Incidence, Causes and Preventions, 4th edition. Eds. C. H. Collins and D. A. Kennedy. Butterworth Heinemann, Oxford 1999. Pp. 324. ISBN 0 7506 4023 5. Epidemiology and Infection, 123 (1), 181-181 DOI: 10.1017/S0950268899002514

Meet Your Mites


Just two months ago, I had the distinct pleasure of acting not as a science scholar but as a research participant. Instead of having my face in a book, I willingly offered it to a woman who diligently scraped my forehead in search of Demodex mites. I know that it’s everyone’s humble dream to contribute their own exquisite arachnological flora to Science with an S and so, yes Reader, I can feel your oozing envy.

I spent the last weekend of January in Raleigh, North Carolina attending the incredible Science Online 2013 conference and one of the events at the opening reception included an opportunity to “Meet Your Mites” from the Your Wild Life team. As you can imagine, I quite literally squealed for joy. Demodex is one of my favorite parasites and I was eager to contribute my own special brand of commensal to a subject that is little studied. While waiting impatiently in line, my fellow participants and I gazed at a video of a squirming captive mite recently scraped with spatula from a very lucky individual and excitedly wondered if we too would see our own Demodex under the microscope.

You can see a Youtube video below of a mite that yielded to the executioner’s spatula from the Science Online event below!

Your Wild Life is a “team of scientists, science communicators, students, and citizens who are passionate about exploring the ecological frontiers that exist right under our noses.” Thus far they’ve ventured into some amazing, uncharted territory – looking at the bacterial biodiversity of belly buttons and armpits, the spectrum of arthropod species in human households, among other fact-finding missions that seek to illuminate the underlying richness that lives within and around us.

Meet Your Mites is their very latest biological mission on this little known buggie. In fact, the most that we know of Demodex mites is that … well, that they can be found on people’s faces. We don’t know much of anything about their evolutionary history, their geographical distribution and prevalence, or their preference for cosmetics. Just what are these little guys (and girls) up to? Why are they nesting in our eyebrows, crawling over our eyelids and eating our sebaceous goo? What kind of awful cosmological practical joke is this?

Megan Thoemmes is a research assistant affiliated with the this endeavour and she kindly enlightened me on this very fun project.

What is the goal of the Meet Your Mites project? 

The purpose of this study is to map the evolutionary history of Demodex mites with the expansion of human populations through time and space. Despite their intimate, parasitic relationship with human hosts, Demodex mites have not been extensively studied. We will trace the evolutionary history and  diversification of Demodex mites, and in doing so, gain new insights about the radiation of human populations.

Why now? 

This is the age of personal science, where we are learning about the similarities and differences between people and their own individual biomes. Understanding our association with these organisms is an important piece of the picture when figuring out the relationships we have with the species that live on, in and around our bodies. This project also serves as an opportunity to reach out and engage the public in both interesting and significant research. What have you guys found so far?

The project is still in its infancy, so we don’t have a large sample size or any solid results yet. We have just had our first round of sampling events, and we are trying to figure out our methods for getting the best possible DNA sequences from the mites, but we do seem to have a good method for sample collection. We’re also working out a new way of getting mite DNA from an individual’s face that would allow the participant to easily sample themselves, while allowing us to get a large number of samples from around the world.
Even though we are still in the early stages of the project, I suppose that one of the most interesting observations we have had is that there is a lot of morphological variation across the individual mites, and we think it is possible we could be seeing more than the two previously described species of human specific mites. 
A captured Demodex brevis,  a rare species that the Meet Your Mites has only found with certainty twice. Image: Your Wild Life.

Under the microcope, a captured Demodex brevis, one of two species of Demodex mites found on humans. Image: Your Wild Life.

The Meet Your Mites project hopes to shed light on the ancient history of one of our most ancient and overlooked commensals. I’m eager to hear what they discover and to see if one of my own little mite sidekicks has yielded any of my precious bodily secrets. And if you’re in the Raleigh-Durham area, you can contribute to this form of citizen-science too, as the project is hosting various “face sampling events” over the year. You can sign up here to be notified of upcoming events and check out their website on the project here. Face sampling, ya’ll, face sampling! How can you resist?

Visit the Your Wild Life website to learn more about their fun projects, the resarch team and read their blog.
Dr. Rob Dunn heads the Your Wild Life project with Dr. Holly Menninger and has written a book on the subject of our commensal comrades. You can purchase his book here and visit his website here.

A Mess in Texas: What Happened in Dallas with West Nile Virus?


That insistent buzzing drone you hear? It’s the sound of our burgeoning mosquito problem and the nasty diseases that they carry wreaking havoc throughout the world. 2012 was a prodigious year for mosquito-borne arboviral diseases, with West Nile virus, Japanese encephalitis, malaria, dengue and yellow fever outbreaks and epidemics raging in the United States, the Sudan, Puerto Rico, Malaysia,  IndonesiaIndiaPeruBrazil and many other nations besides.

“Don’t Mess With Texas,” the road sign warning drivers throughout the State to not litter Texan roadways. This year, Texas had a more insidious mess on their hands. Image: Anne Ward. Click for source.

If you live in the US, you might know that this year the country suffered the largest outbreak of West Nile virus (WNV) since 2003. As of December 11th, infections with the virus have been reported in humans, birds and mosquitos in all of the lower 48 states. In humans, there have been a reported  5,387 cases of WNV disease with 2,734 or 51% of these cases classified as West Nile neuroinvasive disease (WNND), a severe manifestation of the infection resulting in encephalitis, chronic mental sequelae and occasionally death, and there have been 243 deaths; 80% of these cases have occurred in 13 states with a third of all cases reported in Texas (1).

Though it’s unknown why 2012 proved to be a particularly noxious and geographically expansive year for WNV in the States, there were several environmental factors that precipitated the outbreak’s emergence in Texas that may have influenced its severity. A short, mild winter at the tail end of 2011 may have allowed for greater numbers of mosquitos to survive the winter, an occurrence known as “overwintering”. In the spring and summer that followed, bouts of rain provided standing water for mosquito breeding and egg laying while droughts and higher than average temperatures may have also accelerated the replication of the WNV in birds and increased its transmissibility to mosquitoes, thereby augmenting its spread across the country (2)(3)(4)(5).

Dallas county in Texas has disproportionately suffered the majority of WNV cases and fatalities – 405 total cases of WNV disease and 18 deaths (6). Aside from auspicious environmental conditions for the mosquito population and the virus, the scale and severity of the outbreak can partly be attributed to the county’s inadequate dedication to mosquito surveillance and control, which led to several challenges to WNV disease prevention within the local population.

West Nile virus (WNV) activity reported to the CDC’s arbovirus surveillance system ArboNET as of December 11, 2012, by county in the United States. Source: ArbnoNET. Click for more in-depth data and info.

Dallas county did not follow their own established protocols for mosquito surveillance or the recommendations of mosquito experts, and decided to test mosquitoes for arboviruses in May rather  than April despite the aforementioned environmental conditions. In doing so, the county failed to adequately evaluate the extent of WNV infection in the mosquito population (7)(8). As the outbreak crescendoed over the early summer, the county had only a scant four employees dedicated to mosquito surveillance and control for an area 871 square miles wide and with a population of 1.2 million residing in Dallas city alone (7).The county administered a woefully low number of mosquito traps – one trap for every 19 square miles and only 20 traps per week – once more failing to either assess the magnitude of the mosquito population or properly identify the cities most at risk for transmission of mosquito-borne diseases (7). Furthermore, Dallas county did not track and test deceased birds for the virus, a well-established and commonly used sentinel surveillance strategy for monitoring arboviral diseases in susceptible populations of wild and domestic animals (4)(8). Larvicide to treat egg-laden mosquito pools wasn’t purchased until July 30th, well into the beginning of the epidemic, “days after the CDC told the city’s health department that Dallas was already at the highest-possible risk level for West Nile virus.” (8)

Simply put, there were inadequate resources available for vector and viral monitoring in Dallas County and throughout the state oF Texas as a whole and, as a result, the mosquito population and the levels of WNV infection present in the population skyrocketed, all the while unbeknownst to local health officials. The outbreak only became apparent as escalating numbers of human infections were reported by local and state health officials to ArboNET, the CDC’s national database for monitoring arboviral infections in the populace, and the CDC  in turn notified Texan public health officials. In the end, extreme and expensive measures had to be taken in the form of aerial and land pesticide spraying to staunch the numbers of increasing WNV infections and infection-related deaths.

North Dallas neighborhoods sprayed in mid-July to kill mosquitoes carrying the West Nile virus. Image: Tom Fox at Dallas News. Click for source.

The WNV outbreak in Dallas county is a grim yet instructional example of the importance of active disease surveillance and institutionalized vector control programs. Surveillance – whether through monitoring the levels of tick populations or tracking the numbers of people reporting with flulike symptoms in emergency rooms – is the foundation of preventative public health. Without some truly simple and basic methods of tracking mosquitos and testing them for life-threatening diseases, we will again have outbreaks that can only be controlled by expensive, draconian measures that include using planes to shower urban cities with pesticide. Just a few short months after the outbreak that claimed 18 lives, Dallas county is now conducting year-round surveillance and testing of mosquitos to prevent another costly and deadly outbreak (10). Hopefully, the lessons learned in the 2012 outbreak will influence future public health efforts regarding mosquito and arbovirus surveillance in Texas in the years to come.

Full disclosure: This article is adapted and modified from an essay on the investigation of the WNV outbreak in 2012 from a class I took last semester on outbreak epidemiology.

Note: The information in this article is heavily reliant on the excellent investigational reporting by Scott Friedman at NBC 5. You can see an archive of his work for NBC, including his WNV investigative work, here.


A brief article in Emerging Infectious Diseases, “West Nile Virus Infection among Humans, Texas, USA, 2002–2011,” found that WNV has become endemic in the state and the number of reported cases of infection increased every three years though that doubtlessly has changed following this year.

An incredible close-up and personal view of the eyes of a mosquito.

“Over one million people worldwide die from mosquito-borne diseases every year.” Curious about what those are? Check out for their list of the nasty infections that mosquitos spread to humans, horses, birds and dogs.

The strange weather we’ve had this year – from droughts to monsoonal rainstorms to shocking heat waves – certainly played a role in the WNV outbreak in Dallas. The NYT talks about the new climatological reality in this superb article.


(1) CDC (December 11, 2012) “2012 West Nile virus update: November 20” CDC West Nile Virus Homepage. Accessed January 11, 2013 here.

(2) JE Soverow (2009) Infectious Disease in a Warming World: How Weather Influenced West Nile Virus in the United States (2001–2005). Environ Health Perspect. 117(7): 1049–1052

(3) RM Kinney (2006) Avian virulence and thermostable replication of the North American strain of West Nile virus. J Gen Virol. 87(12): 3611-3622

(4) R Jaslow (August 24, 2012) “What’s making the 2012 West Nile virus outbreak the worst ever?” CBS News [Online]. Accessed November 23, 2012 here.

(5) CDC (August 22, 2012) CDC Telebriefing on West Nile Virus Update. CDC Newsroom. Accessed November 23, 2012 here.

(6) Texas Department of State Health Services. (December 17, 2012) News Updates Webpage. Accessed January 11, 2013 here.

(7) S Friedman. (September 17, 2012) “Missed Opportunities in Fight Against West Nile Virus.” NBC Dallas-Forth Worth. Accessed November 22, 2012 here.

(8) S Friedman (September 13, 2012) “Dallas Revisits West Nile Virus Attack Plan.” NBC Dallas-Forth Worth [Online]. Accessed November 22, 2012 here.

(9) M Fernandez (August 16, 2012) “West Nile Hits Hard Around Dallas, With Fear of Its Spread.” The New York Times [Online]. Accessed November 22, 2012 here.

(10) J Stengle (December 26, 2012) “Health experts turn attention to learning lessons from historic West Nile outbreak.” The Republic [Online]. Accessed January 11, 2013 here.

ResearchBlogging.orgSoverow, J., Wellenius, G., Fisman, D., & Mittleman, M. (2009). Infectious Disease in a Warming World: How Weather Influenced West Nile Virus in the United States (2001-2005) Environmental Health Perspectives DOI: 10.1289/ehp.0800487