Pneumococcus can spread via hand-to-nose contact
The pneumonia-causing bacteria, Streptococcus pneumoniae (pneumococcus), can be spread through nose picking and rubbing after exposure of the hands to the bacteria — in addition to the conventionally known route of inhalation of airborne droplets, a study reveals.
“Our current understanding of the transmission of pneumococcus is poor … Having a clearer understanding of how the bacteria is spread will allow for better advice on how transmission can be reduced, so that there is greater prevention of pneumococcal infections,” said lead author Dr Victoria Connor of the Liverpool School of Tropical Medicine and Royal Liverpool Hospital, Liverpool, UK.
The study included 63 healthy adult participants (mean age 22.6 years) who applied water containing Streptococcus pneumoniae serotype 6B (3.2x106 colony-forming units [CFU]) onto their hands. One group of participants were asked to sniff the bacterial residue or pick their nose immediately after exposure (wet sniff/poke); while another group was asked to do either action when the bacterial residue became visibly dry (dry sniff/poke). After exposure, nasal washes were collected on days 2, 6, and 9 to assess for nasopharyngeal colonization. None of the participants had viral infections based on throat swabs before pneumococcal exposure.
The researchers found that nasopharyngeal colonization occurred regardless of whether bacterial residue was “wet” or “dry”. Even after the bacterial residue had dried up, one of the 10 participants in the “dry sniff” group still showed colonization by culture method and seven out of 10 by the more sensitive qPCR testing. [Eur Respir J 2018;doi:10.1183/13993003.00599-2018]
Although both “wet” and “dry” pneumococcus residue resulted in colonization, the density of bacteria transmitted was higher if the residue was “wet”: colonization densities were 5.6×101 and 4.7 CFU/mL nasal wash in the “wet sniff” and “wet poke” groups, respectively vs 2.4 CFU/mL nasal wash in the “dry sniff” group. No colonization was detected in the “dry sniff” group by culture testing.
Also, significantly more participants in the “wet” group had bacterial colonization than the “dry” group (n=7/20 vs 1/20; p=0.04).
Nose picking (“poke” group) was similarly likely as nose rubbing (“sniff” group) to spread pneumococcus in both the “wet” (n=4/10 vs 3/10) and “dry” cohorts (n=0/10 vs 1/10).
“This pilot study is the first to confirm that pneumococcus bacteria can be spread through direct contact, rather than just through breathing in airborne bacteria,” said ERS* President Professor Tobias Welte from Hannover University in Hannover, Germany, who was unaffiliated with the study.
“For clinicians, the findings reinforce the message that we must promote rigorous hand hygiene and basic infection control measures such as avoidance of sharing food, drink and mobile phones, in order to potentially reduce the transmission of respiratory bacterial pathogens such as pneumococcus,” he advised.
Nonetheless, whether reducing pneumococcal exposure is beneficial for overall health in healthy adults and children remains unclear, as early exposure may elicit immune response which can reduce chances of carrying the disease later in life, the researchers pointed out. [Am J Respir Crit Care Med 2013;187:855-864; PLoS Pathog 2013;9:e1003274]
“But for parents, as this research shows that hands are likely to spread pneumococcus, this may be important when children are in contact with elderly relatives or relatives with reduced immune systems. In these situations, ensuring good hand hygiene and cleaning of toys or surfaces would likely reduce transmission, and reduce the risk of developing pneumococcal infection such as pneumonia,” Connor suggested.