Role of Antibiotic Penetration Limitation in Klebsiella pneumoniae Biofilm Resistance to Ampicillin and Ciprofloxacin
01 Jul 2000-Antimicrobial Agents and Chemotherapy (American Society for Microbiology)-Vol. 44, Iss: 7, pp 1818-1824
TL;DR: The results suggest that some other resistance mechanism is involved for both agents and contributed to wild-type biofilm resistance to ampicillin but not to ciprofloxacin.
Abstract: The penetration of two antibiotics, ampicillin and ciprofloxacin, through biofilms developed in an in vitro model system was investigated. The susceptibilities of biofilms and corresponding freely suspended bacteria to killing by the antibiotics were also measured. Biofilms of Klebsiella pneumoniae were developed on microporous membranes resting on agar nutrient medium. The susceptibilities of planktonic cultures and biofilms to 10 times the MIC were determined. Antibiotic penetration through biofilms was measured by assaying the concentration of antibiotic that diffused through the biofilm to an overlying filter disk. Parallel experiments were performed with a mutant K. pneumoniae strain in which beta-lactamase activity was eliminated. For wild-type K. pneumoniae grown in suspension culture, ampicillin and ciprofloxacin MICs were 500 and 0.18 microgram/ml, respectively. The log reductions in the number of CFU of planktonic wild-type bacteria after 4 h of treatment at 10 times the MIC were 4.43 +/- 0.33 and 4.14 +/- 0.33 for ampicillin and ciprofloxacin, respectively. Biofilms of the same strain were much less susceptible, yielding log reductions in the number of CFU of -0.06 +/- 0.06 and 1.02 +/- 0.04 for ampicillin and ciprofloxacin, respectively, for the same treatment. The number of CFU in the biofilms after 24 h of antibiotic exposure was not statistically different from the number after 4 h of treatment. Ampicillin did not penetrate wild-type K. pneumoniae biofilms, whereas ciprofloxacin and a nonreactive tracer (chloride ion) penetrated the biofilms quickly. The concentration of ciprofloxacin reached the MIC throughout the biofilm within 20 min. Ampicillin penetrated biofilms formed by a beta-lactamase-deficient mutant. However, the biofilms formed by this mutant were resistant to ampicillin treatment, exhibiting a 0.18 +/- 0.07 log reduction in the number of CFU after 4 h of exposure and a 1.64 +/- 0.33 log reduction in the number of CFU after 24 h of exposure. Poor penetration contributed to wild-type biofilm resistance to ampicillin but not to ciprofloxacin. The increased resistance of the wild-type strain to ciprofloxacin and the mutant strain to ampicillin and ciprofloxacin could not be accounted for by antibiotic inactivation or slow diffusion since these antibiotics fully penetrated the biofilms. These results suggest that some other resistance mechanism is involved for both agents.
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TL;DR: The features of biofilm infections are summarized, the emerging mechanisms of resistance are reviewed, and potential therapies are discussed.
4,116 citations
TL;DR: Owing to the heterogeneous nature of the biofilm, it is likely that there are multiple resistance mechanisms at work within a single community.
3,578 citations
TL;DR: The mechanisms that underlie biofilm resistance to antimicrobial chemotherapy will be examined, with particular attention being given to potential avenues for the effective treatment of biofilms.
Abstract: According to a public announcement by the US National Institutes of Health
, “Biofilms are medically important, accounting for over 80% of microbial infections in the body”. Yet bacterial biofilms remain poorly understood and strategies for their control remain underdeveloped. Standard antimicrobial treatments typically fail to eradicate biofilms, which can result in chronic infection and the need for surgical removal of afflicted areas. The need to create effective therapies to counter biofilm infections presents one of the most pressing challenges in anti-bacterial drug development. In this article, the mechanisms that underlie biofilm resistance to antimicrobial chemotherapy will be examined, with particular attention being given to potential avenues for the effective treatment of biofilms.
2,302 citations
TL;DR: The nature of bacterial biofilm resistance to antimicrobials is the subject of the present minireview and describes an increased resistance of cells to killing.
Abstract: A biofilm is a population of cells growing on a surface and enclosed in an exopolysaccharide matrix. Biofilms are notoriously difficult to eradicate and are a source of many recalcitrant infections. The nature of bacterial biofilm resistance to antimicrobials is the subject of the present minireview. Pathogenic yeast such as Candida albicans also form recalcitrant biofilms, and this topic has recently been reviewed (5). Resistance is an ability of a microorganism to grow in the presence of an elevated level of an antimicrobial. In short, a strain for which the MIC is increased is resistant. By this conventional criterion, biofilm cells do not necessarily show increased resistance. With some exceptions, biofilm cells do not grow better than planktonic cells in the presence of a broad range of antimicrobials. This is evident from examination of susceptibility data in the biofilm literature (33). However, in most biofilm susceptibility studies, only survival of cells in a preformed biofilm rather than the ability of a biofilm to grow is recorded. Accordingly, the reported “resistance” describes an increased resistance of cells to killing. This is indeed what biofilms are good at: they are not easily eradicated by cidal antimicrobials. The ability of antimicrobials to inhibit biofilm growth indicates that they are able to diffuse through the biofilm and act normally against their targets. Why, then, do biofilm cells not die? This is the crux of the problem and the riddle that needs to be solved.
1,830 citations
TL;DR: Disabling biofilm resistance may enhance the ability of existing antibiotics to clear infections involving biofilms that are refractory to current treatments.
1,202 citations
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11,162 citations
"Role of Antibiotic Penetration Limi..." refers background in this paper
...Bacterial biofilms are frequently observed on the surfaces of tissues (12, 30, 31) and biomaterials (5, 10, 39, 42, 47) at the site of persistent infections (8)....
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...Once in the biofilm, extracellular polymeric substances shield bacteria from opsonization and phagocytosis (8, 23)....
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...Often, the only solution is mechanical removal of the biofilm or implant, which is costly and traumatic to the patient (8)....
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...Treatment of an infection after the biofilm is established is frequently futile with current remedies (8)....
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3,200 citations
"Role of Antibiotic Penetration Limi..." refers background in this paper
...The second hypothesis for reduced biofilm susceptibility, which could be termed physiological limitation, proposes that some microorganisms within the biofilm exist in a more recalcitrant phenotypic state (6, 9 , 34)....
[...]
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TL;DR: The sticky conglomerations of bacteria known as biofilms are being linked to common human diseases ranging from tooth decay to prostatitis and kidney infections, and a new program at the National Institutes of Health is working to understand how and why they form.
Abstract: The sticky conglomerations of bacteria known as biofilms are being linked to common human diseases ranging from tooth decay to prostatitis and kidney infections. Aided by support from a new program at the National Institutes of Health, researchers are now working to understand how and why biofilms form. The goal is to identify their Achilles9 heel and devise better treatments, which are badly needed, because bacteria sequestered in biofilms are shielded from attack by the host9s immune system and are often much harder to kill with antibiotics than their free-floating counterparts.
550 citations
"Role of Antibiotic Penetration Limi..." refers background in this paper
...Bacterial biofilms are frequently observed on the surfaces of tissues (12, 30, 31) and biomaterials (5, 10, 39, 42, 47) at the site of persistent infections (8)....
[...]