play an important role in HAIs . Although dehydrated , DSBs can still be characterized by the presence of EPS . At maturity , bacterial cells in P . aeruginosa and S . aureus wet surface biofilms become motile , allowing for easy dispersal and re-attachment on other surfaces .”
Notably , compared to wet surface biofilms and planktonic bacteria , DSBs are more tolerant to disinfection , Nkemngong , et al . ( 2020 ) and other researchers report .
As Alfa , et al . ( 2019 ) observe , “ The concept of dry surface biofilm was first introduced by Almatroudi , et al . to identify that hard and soft environmental surfaces within healthcare facilities are not void of organisms , but rather represent a heterogenous accumulation of organisms and other material in a dry matrix . The in vitro dry surface biofilm model that they developed mimics the characteristics of surfaces within healthcare facilities .” They explain further , “ The presence of dry surface biofilm formed on high-touch healthcare surfaces raises the question regarding its role in transmission of pathogens that ultimately cause hospital-acquired infections . It also raises questions regarding the efficacy of removal and inactivation of microbes within dry surface biofilm by currently used cleaning-disinfection methods routinely used in healthcare .”
In her IPAC presentation , Alfa alluded to her associate , Karen Vickery , who developed with colleagues a dry surface biofilm model . “ I thought , ‘ This is something else we must now consider when we ’ re looking at cleaning and disinfection in healthcare .’ I ’ m hoping that today you will leave feeling a little more able to understand what the challenges are .”
Alfa reviewed the basics of planktonic microorganisms , which she described as the simplest form of microorganisms , vegetative forms that can also be mixed with spores .
“ Interestingly , many of the original cleaning and disinfection requirements in healthcare were based on the assumption that it was really only planktonic organisms on surfaces needed to be eradicated ,” Alfa said , adding that , “ The idea being if you had a patient in a room and the organisms and their secretions got on these surfaces , you would be fine as long as you cleaned and disinfected those surfaces . We ’ re now finding that it is more complex than that .”
Alfa explored planktonic organisms ’ ability to survive in the environment , noting that this depends on the individual characteristics of the microorganism . She pointed to slides depicting Acinetobacter baumannii . “ Different microorganisms have differing ability to survive in planktonic form on environmental surfaces . If you leave it as a planktonic form on a surface , how long it can actually survive ? You ’ ll see here we start off with 1,200 colony-forming units ( CFUs ) over 36 days it decreases to be undetectable . If I had taken Pseudomonas aeruginosa and done the same thing with it , within 24 hours you would not have seen any
viable organisms because it actually dies very quickly . And then there ’ s other organisms like Bacillus subtilis , which is an environmental organism , and even the vegetative form of it can survive much longer than Acinetobacter baumannii can survive .”
Alfa introduced the audience to the concept of viable but non-culturable organisms ( VBNC ).
“ We ’ re used to the idea that if I clean and disinfect a surface , I expect to be able to kill planktonic bacteria in all the vegetative forms . But in actuality , the organisms are like us – if you are confronted with a challenge , you become defensive . The organisms do the same thing ; if they are exposed to dehydration , they shut down their metabolism and they go into hunker-down mode . It depends on the type of organism , but the idea that the organism — if you try to culture it on media — it won ’ t grow because it ’ s in this hunker-down mode , it ’ s shut down its metabolism and often it needs special triggers , much like if you ’ re in the desert and you see no vegetation whatsoever and then as soon as it rains , you see all kinds of things pop up ,” she explained . “ VBNC organisms are something we need to pay attention to because they can revive themselves and they can infect patients . When challenging the organisms with either dehydration or disinfectants , they go into their protective mode to try to survive .”
Alfa also emphasized the spore form of some organisms that exist in biofilms . “ Some of them can survive for many years . I have seen Clostridium difficile spores that have been stored in alcohol for years and years and years , and they will actually live again .”
She continued , “ We ’ ve talked about planktonic bacteria . If you look at traditional biofilm , usually the whole surface is bathed in fluid and there is flow . So , picture any drain in your healthcare facility and if you were to go into that drain , you would find that there ’ s traditional biofilm that forms in pretty much all drains . And with the bathing of fluid , the organisms , once there is a matrix that starts to form around the organisms and adhere to the surface , that ’ s the attachment phase . The initial replication in terms of adhesion is reversible , but as soon as you get more mature biofilm forming , it ’ s literally irreversible . So , if you have any hope of getting rid of traditional biofilm , you need to catch it at this stage to eliminate it ; after the adhesion , there is excretion of extracellular polymeric substances ( EPS ), a fancy name for the goo that the pathogens produce to protect themselves . So , it could be cellular material , it could be protein , it could be DNA , but it accumulates around the organisms and it protects them from the stressors in their environment .”
Alfa added that once the biofilms reach full maturity , there are organisms within that biofilm matrix that are called persisters . “ This means the same thing as viable but non-culturable – these are organisms that persist and they ’ re not metabolically active , but they can be at some point in time . And as the maturation occurs , they get to the point where they deplete all
Environmental surfaces ( e . g ., food trolleys , hospital commodes , bed rails ) and mobile patient care equipment such as blood pressure cuffs and intravenous poles support the formation of biofilms by providing a platform for the attachment of planktonic bacterial cells … Once formed , biofilms are capable of growing on dry surfaces in healthcare facilities for protracted periods , surviving for as long as one year .” — Michelle Alfa , PhD , FCCM
www . healthcarehygienemagazine . com • july 2023
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