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Ixodes pacificus ticks maintain embryogenesis and egg hatching after antibiotic treatment of Rickettsia endosymbiont.

Kurlovs AH, Li J, Cheng D, Zhong J - PLoS ONE (2014)

Bottom Line: Ampicillin did not significantly affect the number of Rickettsia per tick cell in adults or eggs compared to the water-injected control ticks.We also demonstrated that Rickettsia-free eggs could successfully develop into larvae without any significant decrease in hatching compared to eggs containing Rickettsia.We concluded that Rickettsia species phylotype G021 does not have an apparent effect on embryogenesis, oviposition, and egg hatching of I. pacificus.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America.

ABSTRACT
Rickettsia is a genus of intracellular bacteria that causes a variety of diseases in humans and other mammals and associates with a diverse group of arthropods. Although Rickettsia appears to be common in ticks, most Rickettsia-tick relationships remain generally uncharacterized. The most intimate of these associations is Rickettsia species phylotype G021, a maternally and transstadially transmitted endosymbiont that resides in 100% of I. pacificus in California. We investigated the effects of this Rickettsia phylotype on I. pacificus reproductive fitness using selective antibiotic treatment. Ciprofloxacin was 10-fold more effective than tetracycline in eliminating Rickettsia from I. pacificus, and quantitative PCR results showed that eggs from the ciprofloxacin-treated ticks contained an average of 0.02 Rickettsia per egg cell as opposed to the average of 0.2 in the tetracycline-treated ticks. Ampicillin did not significantly affect the number of Rickettsia per tick cell in adults or eggs compared to the water-injected control ticks. We found no relationship between tick embryogenesis and rickettsial density in engorged I. pacificus females. Tetracycline treatment significantly delayed oviposition of I. pacificus ticks, but the antibiotic's effect was unlikely related to Rickettsia. We also demonstrated that Rickettsia-free eggs could successfully develop into larvae without any significant decrease in hatching compared to eggs containing Rickettsia. No significant differences in the incubation period, egg hatching rate, and the number of larvae were found between any of the antibiotic-treated groups and the water-injected tick control. We concluded that Rickettsia species phylotype G021 does not have an apparent effect on embryogenesis, oviposition, and egg hatching of I. pacificus.

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Kaplan-Meier (time-to-event) plots of the preoviposition period and the incubation periods, and boxplots representing egg hatching rate, and the number of larvae from engorged Ixodes pacificus females.2A) A Kaplan-Meier plot where each colored line corresponds to the fraction of adult female ticks that had not started laying eggs on a particular day after the ticks were injected with antibiotics or water (control). Vertical dashes on the colored lines represent censorship, where a tick that had not started to lay eggs died and was dropped from the study. The tetracycline group (red) took significantly longer to start laying eggs compared to the rest (P<0.05) 2B) A Kaplan-Meier plot where the colored lines represent the proportion of egg samples laid by individual ticks whose eggs had not finished hatching into larvae a certain number of days after oviposition began. 2C) A boxplot showing the hatching rate, or the fraction of tick eggs that successfully hatched into larvae, in the four treatment groups. Each individually colored box represents the hatching rate distribution of eggs laid by each female tick in the group. 2D) A boxplot specifying the distribution of the total number of larvae each female yielded. No significant difference in (C) hatching rate or (D) the number of larvae was present between treatment groups (P<0.05). Circles outside the boxes in (C) and (D) represent outliers. The colors in all the plots in the figure correspond to specific treatment groups: blue - ampicillin, yellow - ciprofloxacin, red - tetracycline, green - injection with water (control).
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pone-0104815-g002: Kaplan-Meier (time-to-event) plots of the preoviposition period and the incubation periods, and boxplots representing egg hatching rate, and the number of larvae from engorged Ixodes pacificus females.2A) A Kaplan-Meier plot where each colored line corresponds to the fraction of adult female ticks that had not started laying eggs on a particular day after the ticks were injected with antibiotics or water (control). Vertical dashes on the colored lines represent censorship, where a tick that had not started to lay eggs died and was dropped from the study. The tetracycline group (red) took significantly longer to start laying eggs compared to the rest (P<0.05) 2B) A Kaplan-Meier plot where the colored lines represent the proportion of egg samples laid by individual ticks whose eggs had not finished hatching into larvae a certain number of days after oviposition began. 2C) A boxplot showing the hatching rate, or the fraction of tick eggs that successfully hatched into larvae, in the four treatment groups. Each individually colored box represents the hatching rate distribution of eggs laid by each female tick in the group. 2D) A boxplot specifying the distribution of the total number of larvae each female yielded. No significant difference in (C) hatching rate or (D) the number of larvae was present between treatment groups (P<0.05). Circles outside the boxes in (C) and (D) represent outliers. The colors in all the plots in the figure correspond to specific treatment groups: blue - ampicillin, yellow - ciprofloxacin, red - tetracycline, green - injection with water (control).

Mentions: Ticks in the tetracycline group took a median (95% CI) of 13 (10–16) days after injection treatment to start laying eggs. Ciprofloxacin, water control and ampicillin groups each spent a median of 9 (8–10) days after injection before commencing oviposition, (Figure 2A). Tetracycline treatment significantly delayed I. pacificus oviposition compared to all other treatment groups (Log-Rank test, P<0.05). The preoviposition periods of the ampicillin, ciprofloxacin, and control groups were not significantly different from each other (Log-Rank test, P>0.05).


Ixodes pacificus ticks maintain embryogenesis and egg hatching after antibiotic treatment of Rickettsia endosymbiont.

Kurlovs AH, Li J, Cheng D, Zhong J - PLoS ONE (2014)

Kaplan-Meier (time-to-event) plots of the preoviposition period and the incubation periods, and boxplots representing egg hatching rate, and the number of larvae from engorged Ixodes pacificus females.2A) A Kaplan-Meier plot where each colored line corresponds to the fraction of adult female ticks that had not started laying eggs on a particular day after the ticks were injected with antibiotics or water (control). Vertical dashes on the colored lines represent censorship, where a tick that had not started to lay eggs died and was dropped from the study. The tetracycline group (red) took significantly longer to start laying eggs compared to the rest (P<0.05) 2B) A Kaplan-Meier plot where the colored lines represent the proportion of egg samples laid by individual ticks whose eggs had not finished hatching into larvae a certain number of days after oviposition began. 2C) A boxplot showing the hatching rate, or the fraction of tick eggs that successfully hatched into larvae, in the four treatment groups. Each individually colored box represents the hatching rate distribution of eggs laid by each female tick in the group. 2D) A boxplot specifying the distribution of the total number of larvae each female yielded. No significant difference in (C) hatching rate or (D) the number of larvae was present between treatment groups (P<0.05). Circles outside the boxes in (C) and (D) represent outliers. The colors in all the plots in the figure correspond to specific treatment groups: blue - ampicillin, yellow - ciprofloxacin, red - tetracycline, green - injection with water (control).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126787&req=5

pone-0104815-g002: Kaplan-Meier (time-to-event) plots of the preoviposition period and the incubation periods, and boxplots representing egg hatching rate, and the number of larvae from engorged Ixodes pacificus females.2A) A Kaplan-Meier plot where each colored line corresponds to the fraction of adult female ticks that had not started laying eggs on a particular day after the ticks were injected with antibiotics or water (control). Vertical dashes on the colored lines represent censorship, where a tick that had not started to lay eggs died and was dropped from the study. The tetracycline group (red) took significantly longer to start laying eggs compared to the rest (P<0.05) 2B) A Kaplan-Meier plot where the colored lines represent the proportion of egg samples laid by individual ticks whose eggs had not finished hatching into larvae a certain number of days after oviposition began. 2C) A boxplot showing the hatching rate, or the fraction of tick eggs that successfully hatched into larvae, in the four treatment groups. Each individually colored box represents the hatching rate distribution of eggs laid by each female tick in the group. 2D) A boxplot specifying the distribution of the total number of larvae each female yielded. No significant difference in (C) hatching rate or (D) the number of larvae was present between treatment groups (P<0.05). Circles outside the boxes in (C) and (D) represent outliers. The colors in all the plots in the figure correspond to specific treatment groups: blue - ampicillin, yellow - ciprofloxacin, red - tetracycline, green - injection with water (control).
Mentions: Ticks in the tetracycline group took a median (95% CI) of 13 (10–16) days after injection treatment to start laying eggs. Ciprofloxacin, water control and ampicillin groups each spent a median of 9 (8–10) days after injection before commencing oviposition, (Figure 2A). Tetracycline treatment significantly delayed I. pacificus oviposition compared to all other treatment groups (Log-Rank test, P<0.05). The preoviposition periods of the ampicillin, ciprofloxacin, and control groups were not significantly different from each other (Log-Rank test, P>0.05).

Bottom Line: Ampicillin did not significantly affect the number of Rickettsia per tick cell in adults or eggs compared to the water-injected control ticks.We also demonstrated that Rickettsia-free eggs could successfully develop into larvae without any significant decrease in hatching compared to eggs containing Rickettsia.We concluded that Rickettsia species phylotype G021 does not have an apparent effect on embryogenesis, oviposition, and egg hatching of I. pacificus.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America.

ABSTRACT
Rickettsia is a genus of intracellular bacteria that causes a variety of diseases in humans and other mammals and associates with a diverse group of arthropods. Although Rickettsia appears to be common in ticks, most Rickettsia-tick relationships remain generally uncharacterized. The most intimate of these associations is Rickettsia species phylotype G021, a maternally and transstadially transmitted endosymbiont that resides in 100% of I. pacificus in California. We investigated the effects of this Rickettsia phylotype on I. pacificus reproductive fitness using selective antibiotic treatment. Ciprofloxacin was 10-fold more effective than tetracycline in eliminating Rickettsia from I. pacificus, and quantitative PCR results showed that eggs from the ciprofloxacin-treated ticks contained an average of 0.02 Rickettsia per egg cell as opposed to the average of 0.2 in the tetracycline-treated ticks. Ampicillin did not significantly affect the number of Rickettsia per tick cell in adults or eggs compared to the water-injected control ticks. We found no relationship between tick embryogenesis and rickettsial density in engorged I. pacificus females. Tetracycline treatment significantly delayed oviposition of I. pacificus ticks, but the antibiotic's effect was unlikely related to Rickettsia. We also demonstrated that Rickettsia-free eggs could successfully develop into larvae without any significant decrease in hatching compared to eggs containing Rickettsia. No significant differences in the incubation period, egg hatching rate, and the number of larvae were found between any of the antibiotic-treated groups and the water-injected tick control. We concluded that Rickettsia species phylotype G021 does not have an apparent effect on embryogenesis, oviposition, and egg hatching of I. pacificus.

Show MeSH
Related in: MedlinePlus