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Factors influencing persistence of Legionella pneumophila serogroup 1 in laboratory cocultures.

Solimini AG, Cottarelli A, Marinelli L, De Giusti M - BMC Microbiol. (2014)

Bottom Line: Multiplication and persistence of Legionella may dependent also upon planktonic growth in alternative to sessile growth.In contrast in co-cultures without P. aeruginosa, HPC but not iron were significant factors in explaining the pattern of L. pneumophila, although the HPC effect was different according to the incubation time (HPC x time interaction, p < 0.01).Our results highlight the need of controlling for both HPC and metal constituents of the water systems of buildings used by individuals at particular risk to the effects of Legionella exposure.

View Article: PubMed Central - PubMed

Affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazza A, Moro 5, Rome, 00185, Italy. angelo.solimini@uniroma1.it.

ABSTRACT

Background: Risk for infections from Legionella pneumophila for immunocompromised individuals increases greatly when this species is present within the biofilm of the water distribution systems of hospitals or other health facilities. Multiplication and persistence of Legionella may dependent also upon planktonic growth in alternative to sessile growth. Here we compared the persistence of L. pneumophila serogroup 1 in experimental planktonic co-cultures subsided with iron, Pseudomonas aeruginosa and other non Legionella bacteria (quantified as Heterotrophic Plate Count, HPC at 37°C), isolated from drinking water sources of a large hospital.

Results: Concentrations of L. pneumophila showed a decreasing pattern with incubation time in all co-cultures, the degree of reduction depending on the experimental treatment. In co-cultures with added P. aeruginosa, no L. pneumophila was detectable already after 4 days of incubation. In contrast in co-cultures without P. aeruginosa, HPC but not iron were significant factors in explaining the pattern of L. pneumophila, although the HPC effect was different according to the incubation time (HPC x time interaction, p < 0.01).

Conclusions: Our results highlight the need of controlling for both HPC and metal constituents of the water systems of buildings used by individuals at particular risk to the effects of Legionella exposure.

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Related in: MedlinePlus

Persistence ofL. pneumophilasrg 1 in co-cultures with different initial heterotrophic plate counts at 37°C (HPC) and iron (Fe) subsidy in absence ofP. aeruginosa. Bars show mean and 1 standard error.
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Fig1: Persistence ofL. pneumophilasrg 1 in co-cultures with different initial heterotrophic plate counts at 37°C (HPC) and iron (Fe) subsidy in absence ofP. aeruginosa. Bars show mean and 1 standard error.

Mentions: Concentrations of L. pneumophila showed a decreasing pattern with incubation time in all co-cultures (Figure 1 and 2), the degree of reduction in concentrations depending on the experimental treatment. In the co-cultures with added P. aeruginosa, at time 0 L. pneumophila concentrations were not different between co-cultures supplemented with different initial iron (p = 0.10) and HPC concentrations (p = 0.15) but no L. pneumophila was detectable already after 4 days of incubation (Figure 2). In contrast, in co-cultures without P. aeruginosa (Figure 1), HPC but not iron treatments were significant factors in explaining the pattern of L. pneumophila (Table 2). The HPC effect was different according to the incubation time (HPC × time factor, p < 0.01, Table 2). After 4 days of incubation, L. pneumophila concentrations were higher than controls only in co-cultures supplemented with HPC at initial concentration of 100 CFU/ml (Table 3, mean difference = −0.39 CFU/ml, p < 0.05) while starting from day 8 L. pneumophila concentration was higher than controls in all HPC level treatments (Table 3, all differences p < 0.05).Figure 1


Factors influencing persistence of Legionella pneumophila serogroup 1 in laboratory cocultures.

Solimini AG, Cottarelli A, Marinelli L, De Giusti M - BMC Microbiol. (2014)

Persistence ofL. pneumophilasrg 1 in co-cultures with different initial heterotrophic plate counts at 37°C (HPC) and iron (Fe) subsidy in absence ofP. aeruginosa. Bars show mean and 1 standard error.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4195868&req=5

Fig1: Persistence ofL. pneumophilasrg 1 in co-cultures with different initial heterotrophic plate counts at 37°C (HPC) and iron (Fe) subsidy in absence ofP. aeruginosa. Bars show mean and 1 standard error.
Mentions: Concentrations of L. pneumophila showed a decreasing pattern with incubation time in all co-cultures (Figure 1 and 2), the degree of reduction in concentrations depending on the experimental treatment. In the co-cultures with added P. aeruginosa, at time 0 L. pneumophila concentrations were not different between co-cultures supplemented with different initial iron (p = 0.10) and HPC concentrations (p = 0.15) but no L. pneumophila was detectable already after 4 days of incubation (Figure 2). In contrast, in co-cultures without P. aeruginosa (Figure 1), HPC but not iron treatments were significant factors in explaining the pattern of L. pneumophila (Table 2). The HPC effect was different according to the incubation time (HPC × time factor, p < 0.01, Table 2). After 4 days of incubation, L. pneumophila concentrations were higher than controls only in co-cultures supplemented with HPC at initial concentration of 100 CFU/ml (Table 3, mean difference = −0.39 CFU/ml, p < 0.05) while starting from day 8 L. pneumophila concentration was higher than controls in all HPC level treatments (Table 3, all differences p < 0.05).Figure 1

Bottom Line: Multiplication and persistence of Legionella may dependent also upon planktonic growth in alternative to sessile growth.In contrast in co-cultures without P. aeruginosa, HPC but not iron were significant factors in explaining the pattern of L. pneumophila, although the HPC effect was different according to the incubation time (HPC x time interaction, p < 0.01).Our results highlight the need of controlling for both HPC and metal constituents of the water systems of buildings used by individuals at particular risk to the effects of Legionella exposure.

View Article: PubMed Central - PubMed

Affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazza A, Moro 5, Rome, 00185, Italy. angelo.solimini@uniroma1.it.

ABSTRACT

Background: Risk for infections from Legionella pneumophila for immunocompromised individuals increases greatly when this species is present within the biofilm of the water distribution systems of hospitals or other health facilities. Multiplication and persistence of Legionella may dependent also upon planktonic growth in alternative to sessile growth. Here we compared the persistence of L. pneumophila serogroup 1 in experimental planktonic co-cultures subsided with iron, Pseudomonas aeruginosa and other non Legionella bacteria (quantified as Heterotrophic Plate Count, HPC at 37°C), isolated from drinking water sources of a large hospital.

Results: Concentrations of L. pneumophila showed a decreasing pattern with incubation time in all co-cultures, the degree of reduction depending on the experimental treatment. In co-cultures with added P. aeruginosa, no L. pneumophila was detectable already after 4 days of incubation. In contrast in co-cultures without P. aeruginosa, HPC but not iron were significant factors in explaining the pattern of L. pneumophila, although the HPC effect was different according to the incubation time (HPC x time interaction, p < 0.01).

Conclusions: Our results highlight the need of controlling for both HPC and metal constituents of the water systems of buildings used by individuals at particular risk to the effects of Legionella exposure.

Show MeSH
Related in: MedlinePlus