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Bacteriophages in clinical samples can interfere with microbiological diagnostic tools

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ABSTRACT

Bacteriophages are viruses that infect bacteria, and they are found everywhere their bacterial hosts are present, including the human body. To explore the presence of phages in clinical samples, we assessed 65 clinical samples (blood, ascitic fluid, urine, cerebrospinal fluid, and serum). Infectious tailed phages were detected in >45% of ascitic fluid and urine samples. Three examples of phage interference with bacterial isolation were observed. Phages prevented the confluent bacterial growth required for an antibiogram assay when the inoculum was taken from an agar plate containing lysis plaques, but not when taken from a single colony in a phage-free area. In addition, bacteria were isolated directly from ascitic fluid, but not after liquid enrichment culture of the same samples, since phage propagation lysed the bacteria. Lastly, Gram-negative bacilli observed in a urine sample did not grow on agar plates due to the high densities of infectious phages in the sample.

No MeSH data available.


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Interference of phages in antibiogram plates.(A) ChromID™ CPS® Elite plate of a urine sample; (B) antibiogram agar plate inoculated directly from a colony close to the inoculation zone of this urine sample (arrow 1 in Fig. 4A); (C) antibiogram from an isolated colony far from the inoculation zone of this urine sample (arrow 2 in Fig. 4A). (A,B) show areas of confluent bacterial growth with spots consistent with phage lysis plaques but no spots were observed in (C). Bacteriophage of Podoviridae morphology isolated from (A,B). Bar 100 nm.
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f4: Interference of phages in antibiogram plates.(A) ChromID™ CPS® Elite plate of a urine sample; (B) antibiogram agar plate inoculated directly from a colony close to the inoculation zone of this urine sample (arrow 1 in Fig. 4A); (C) antibiogram from an isolated colony far from the inoculation zone of this urine sample (arrow 2 in Fig. 4A). (A,B) show areas of confluent bacterial growth with spots consistent with phage lysis plaques but no spots were observed in (C). Bacteriophage of Podoviridae morphology isolated from (A,B). Bar 100 nm.

Mentions: The second example of interference was in a urine sample inoculated on chromID™ CPS® Elite plates (CPS plates). The confluent area showed lysis plaques consistent with the presence of phages (Fig. 4A). From this, an inoculum was taken from a colony close to the inoculation zone (Fig. 4A, arrow 1) to perform an antibiogram test. This culture was only 14 hours old and the colonies were small. The resulting antibiogram plate (Fig. 4B) showed a very poor growth of colonies, with an apparent confluent lysis. In a second test conducted 18 hours later, a single colony far from the inoculation zone (Fig. 4A, arrow 2) was taken from the CPS plate and used to inoculate a new plate, which this time yielded growth suitable for the antibiogram test (Fig. 4C). Podoviridae-type phages (Fig. 4D) were detected in the original urine sample and were also recovered from the surface of the first antibiogram plate (Fig. 4B), but not from the second (Fig. 4C).


Bacteriophages in clinical samples can interfere with microbiological diagnostic tools
Interference of phages in antibiogram plates.(A) ChromID™ CPS® Elite plate of a urine sample; (B) antibiogram agar plate inoculated directly from a colony close to the inoculation zone of this urine sample (arrow 1 in Fig. 4A); (C) antibiogram from an isolated colony far from the inoculation zone of this urine sample (arrow 2 in Fig. 4A). (A,B) show areas of confluent bacterial growth with spots consistent with phage lysis plaques but no spots were observed in (C). Bacteriophage of Podoviridae morphology isolated from (A,B). Bar 100 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016790&req=5

f4: Interference of phages in antibiogram plates.(A) ChromID™ CPS® Elite plate of a urine sample; (B) antibiogram agar plate inoculated directly from a colony close to the inoculation zone of this urine sample (arrow 1 in Fig. 4A); (C) antibiogram from an isolated colony far from the inoculation zone of this urine sample (arrow 2 in Fig. 4A). (A,B) show areas of confluent bacterial growth with spots consistent with phage lysis plaques but no spots were observed in (C). Bacteriophage of Podoviridae morphology isolated from (A,B). Bar 100 nm.
Mentions: The second example of interference was in a urine sample inoculated on chromID™ CPS® Elite plates (CPS plates). The confluent area showed lysis plaques consistent with the presence of phages (Fig. 4A). From this, an inoculum was taken from a colony close to the inoculation zone (Fig. 4A, arrow 1) to perform an antibiogram test. This culture was only 14 hours old and the colonies were small. The resulting antibiogram plate (Fig. 4B) showed a very poor growth of colonies, with an apparent confluent lysis. In a second test conducted 18 hours later, a single colony far from the inoculation zone (Fig. 4A, arrow 2) was taken from the CPS plate and used to inoculate a new plate, which this time yielded growth suitable for the antibiogram test (Fig. 4C). Podoviridae-type phages (Fig. 4D) were detected in the original urine sample and were also recovered from the surface of the first antibiogram plate (Fig. 4B), but not from the second (Fig. 4C).

View Article: PubMed Central - PubMed

ABSTRACT

Bacteriophages are viruses that infect bacteria, and they are found everywhere their bacterial hosts are present, including the human body. To explore the presence of phages in clinical samples, we assessed 65 clinical samples (blood, ascitic fluid, urine, cerebrospinal fluid, and serum). Infectious tailed phages were detected in >45% of ascitic fluid and urine samples. Three examples of phage interference with bacterial isolation were observed. Phages prevented the confluent bacterial growth required for an antibiogram assay when the inoculum was taken from an agar plate containing lysis plaques, but not when taken from a single colony in a phage-free area. In addition, bacteria were isolated directly from ascitic fluid, but not after liquid enrichment culture of the same samples, since phage propagation lysed the bacteria. Lastly, Gram-negative bacilli observed in a urine sample did not grow on agar plates due to the high densities of infectious phages in the sample.

No MeSH data available.


Related in: MedlinePlus