From Alzheimer’s to Zebrafish: Eclectic Science and Regulatory Stories 98
physical, chemical and biological interactions. In addition, they have none of the defense
mechanisms that protect mucosal surfaces from bacterial colonization.17 Further, the
surface irregularities common to these devices induce the passive entrapment of bacterial
cells. These foreign bodies are extremely vulnerable to colonization by any contaminating
microbes that might be in their vicinity. Catheters are one example. One researcher who
examined 57 catheters that had been in place for one to 14 days found that bacteria could
be recovered from the surface of 54% of the devices and that in over half of the cases,
two or more organisms were isolated. Some 21 species were recovered, with the most
commonly isolated being Endococcus faecalis, Pseudomonas aeruginosa and Staphylococcus epi-
dermidis.18 Biofilms are almost universally associated with infection of prosthetic material,
particularly in chronic cases, and require thorough debridement and prolonged treatment
with a combination of antibiotics.19
Antimicrobial Resistance and Possible Control
Infectious disease specialists have confirmed cases where persistent infections could not
be resolved with antibiotics, even when laboratory tests indicated these agents should
have been effective. Hundreds of papers have been published describing comparisons
of planktonic and biofilm susceptibility. Each of the papers illustrates resistance in the
biofilm state to diverse microbial species and all sorts of antimicrobial agents.20 Biofilm
susceptibility is influenced significantly by such factors as the thickness, age, species com-
position and genotype and areal cell density of the biofilm, as well as antimicrobial dose
concentration.21
Despite all the research, the protective mechanisms behind biofilm antimicrobial resis-
tance are still mostly unknown. Biologists do, however, now understand how bacterial
biofilms form, therefore controlling them with drugs able to target their unique proper-
ties should be attainable.22 According to Costerton,23 it should be possible to smother
the sticky appendages on the surface of the cells with a molecule that readily attaches to
them, thus reducing their ability to bind to surfaces and form a biofilm in the first place.
Another option is to interfere with the synthesis of the extracellular matrix, such as by
coating medical implants with chemicals that switch off the genes responsible for matrix
production. A third method might be to target the molecules used by biofilm bacteria to
communicate, thereby halting biofilm formation or suppressing toxin production or other
equally invidious activities.24 Studies continue to suggest a promising role for anti-quo-
rum-sensing drugs, possibly as adjuvants to standard antimicrobial therapy.25
References
1. Dixon B. “Mysterious biofilms.” BMJ.1989 298:1724.
2. Orient W. “Slime.” Discover Magazine. July/Aug 2009:60-65.
3. Hentzer M et al. ”Quorum sensing in biofilms.” In: Ghannoum M and O’Toole GA (eds). Microbial Biofilms.
Washington, DC:ASM Press 2004: 118-140.
4. Costerton W, Stewart PS. “Battling biofilms.” Sci Am. 2001 42:75-80.
5. Ibid.
6. Op cit 2.
7. Op cit 4.
8. Kolender PE. “Oral microbial communities: biofilms, interactions, and genetic systems.” Annu Rev Microbiol.
2000 54:412-37.
9. Branda SS, Kolter R. “Multicellularity and Biofilms.” In: Ghannoum M and O’Toole GA (eds). Microbial
Biofilms. Washington, DC:ASM Press 2004:20-29.
10. Op cit 3.
11. Ibid.
12. Op cit 2.
13. Op cit 4.
14. A bacterial cell consists of more than 300 million molecules (not counting water), and several thousand differ-
ent kinds of molecules, and requires some 2,000 genes for its specification.
15. Thomas JG et al. “Biofilms and implant infections.”In: Ghannoum M and O’Toole GA (eds). Microbial Biofilms.
Washington, DC:ASM Press 2004: 269-293.
16. Ibid.
physical, chemical and biological interactions. In addition, they have none of the defense
mechanisms that protect mucosal surfaces from bacterial colonization.17 Further, the
surface irregularities common to these devices induce the passive entrapment of bacterial
cells. These foreign bodies are extremely vulnerable to colonization by any contaminating
microbes that might be in their vicinity. Catheters are one example. One researcher who
examined 57 catheters that had been in place for one to 14 days found that bacteria could
be recovered from the surface of 54% of the devices and that in over half of the cases,
two or more organisms were isolated. Some 21 species were recovered, with the most
commonly isolated being Endococcus faecalis, Pseudomonas aeruginosa and Staphylococcus epi-
dermidis.18 Biofilms are almost universally associated with infection of prosthetic material,
particularly in chronic cases, and require thorough debridement and prolonged treatment
with a combination of antibiotics.19
Antimicrobial Resistance and Possible Control
Infectious disease specialists have confirmed cases where persistent infections could not
be resolved with antibiotics, even when laboratory tests indicated these agents should
have been effective. Hundreds of papers have been published describing comparisons
of planktonic and biofilm susceptibility. Each of the papers illustrates resistance in the
biofilm state to diverse microbial species and all sorts of antimicrobial agents.20 Biofilm
susceptibility is influenced significantly by such factors as the thickness, age, species com-
position and genotype and areal cell density of the biofilm, as well as antimicrobial dose
concentration.21
Despite all the research, the protective mechanisms behind biofilm antimicrobial resis-
tance are still mostly unknown. Biologists do, however, now understand how bacterial
biofilms form, therefore controlling them with drugs able to target their unique proper-
ties should be attainable.22 According to Costerton,23 it should be possible to smother
the sticky appendages on the surface of the cells with a molecule that readily attaches to
them, thus reducing their ability to bind to surfaces and form a biofilm in the first place.
Another option is to interfere with the synthesis of the extracellular matrix, such as by
coating medical implants with chemicals that switch off the genes responsible for matrix
production. A third method might be to target the molecules used by biofilm bacteria to
communicate, thereby halting biofilm formation or suppressing toxin production or other
equally invidious activities.24 Studies continue to suggest a promising role for anti-quo-
rum-sensing drugs, possibly as adjuvants to standard antimicrobial therapy.25
References
1. Dixon B. “Mysterious biofilms.” BMJ.1989 298:1724.
2. Orient W. “Slime.” Discover Magazine. July/Aug 2009:60-65.
3. Hentzer M et al. ”Quorum sensing in biofilms.” In: Ghannoum M and O’Toole GA (eds). Microbial Biofilms.
Washington, DC:ASM Press 2004: 118-140.
4. Costerton W, Stewart PS. “Battling biofilms.” Sci Am. 2001 42:75-80.
5. Ibid.
6. Op cit 2.
7. Op cit 4.
8. Kolender PE. “Oral microbial communities: biofilms, interactions, and genetic systems.” Annu Rev Microbiol.
2000 54:412-37.
9. Branda SS, Kolter R. “Multicellularity and Biofilms.” In: Ghannoum M and O’Toole GA (eds). Microbial
Biofilms. Washington, DC:ASM Press 2004:20-29.
10. Op cit 3.
11. Ibid.
12. Op cit 2.
13. Op cit 4.
14. A bacterial cell consists of more than 300 million molecules (not counting water), and several thousand differ-
ent kinds of molecules, and requires some 2,000 genes for its specification.
15. Thomas JG et al. “Biofilms and implant infections.”In: Ghannoum M and O’Toole GA (eds). Microbial Biofilms.
Washington, DC:ASM Press 2004: 269-293.
16. Ibid.