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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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Related in: MedlinePlus

Illustration of the experimental design and the antibiotic injection results.1A) Experimental design outline, represented as a flow chart. 1B) Tick injection apparatus. Solution is loaded into the microinjection needle using the capillary pipette tip until the needle is full. The tip is then left inside the glass needle and the syringe with a 23-gauge needle is fitted into the capillary pipette tip. 1C) and 1D) Box-whisker plots of rickettsial densities (gene copy ratios of Rickettsia ompA to Ixodes pacificus actin) detected by qPCR in (C) spent females and (D) eggs from the four treatment groups. In both (C) and (D), the same letter next to two plots informs of statistically insignificant difference between the treatment groups (P>0.05), meaning that lack of identical letters stipulates significance (P<0.05).
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pone-0104815-g001: Illustration of the experimental design and the antibiotic injection results.1A) Experimental design outline, represented as a flow chart. 1B) Tick injection apparatus. Solution is loaded into the microinjection needle using the capillary pipette tip until the needle is full. The tip is then left inside the glass needle and the syringe with a 23-gauge needle is fitted into the capillary pipette tip. 1C) and 1D) Box-whisker plots of rickettsial densities (gene copy ratios of Rickettsia ompA to Ixodes pacificus actin) detected by qPCR in (C) spent females and (D) eggs from the four treatment groups. In both (C) and (D), the same letter next to two plots informs of statistically insignificant difference between the treatment groups (P>0.05), meaning that lack of identical letters stipulates significance (P<0.05).

Mentions: Adult I. pacificus were fed on five male New Zealand white rabbits (Oryctolagus cuniculus (Figure 1A). All procedures followed protocols approved by the Institutional Animal Care and Use Committee at Humboldt State University (IACUC protocol 10/11.B.45-A), and all efforts were made to minimize discomfort. Four tin cans with seamless lids (Freund Containers, Lisle, IL) were glued to shaved spots on each rabbit’s back using cyanoacrylate glue. Up to five male and five female ticks were put in each tin can. The ticks were allowed to mate on the rabbits until engorgement.


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)

Illustration of the experimental design and the antibiotic injection results.1A) Experimental design outline, represented as a flow chart. 1B) Tick injection apparatus. Solution is loaded into the microinjection needle using the capillary pipette tip until the needle is full. The tip is then left inside the glass needle and the syringe with a 23-gauge needle is fitted into the capillary pipette tip. 1C) and 1D) Box-whisker plots of rickettsial densities (gene copy ratios of Rickettsia ompA to Ixodes pacificus actin) detected by qPCR in (C) spent females and (D) eggs from the four treatment groups. In both (C) and (D), the same letter next to two plots informs of statistically insignificant difference between the treatment groups (P>0.05), meaning that lack of identical letters stipulates significance (P<0.05).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0104815-g001: Illustration of the experimental design and the antibiotic injection results.1A) Experimental design outline, represented as a flow chart. 1B) Tick injection apparatus. Solution is loaded into the microinjection needle using the capillary pipette tip until the needle is full. The tip is then left inside the glass needle and the syringe with a 23-gauge needle is fitted into the capillary pipette tip. 1C) and 1D) Box-whisker plots of rickettsial densities (gene copy ratios of Rickettsia ompA to Ixodes pacificus actin) detected by qPCR in (C) spent females and (D) eggs from the four treatment groups. In both (C) and (D), the same letter next to two plots informs of statistically insignificant difference between the treatment groups (P>0.05), meaning that lack of identical letters stipulates significance (P<0.05).
Mentions: Adult I. pacificus were fed on five male New Zealand white rabbits (Oryctolagus cuniculus (Figure 1A). All procedures followed protocols approved by the Institutional Animal Care and Use Committee at Humboldt State University (IACUC protocol 10/11.B.45-A), and all efforts were made to minimize discomfort. Four tin cans with seamless lids (Freund Containers, Lisle, IL) were glued to shaved spots on each rabbit’s back using cyanoacrylate glue. Up to five male and five female ticks were put in each tin can. The ticks were allowed to mate on the rabbits until engorgement.

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