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Pierre-Loic Cornut, Sandrine BOISSET, Jérôme ETIENNE, Carole BURILLON, Yvonne BENITO, Max MAURIN, Christophe Chiquet, François VANDENESCH; Specific Pcr Detection Of Staphylococcus And Streptococcus In Endophthalmitis. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1688.
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Gram-positive cocci, mainly Staphylococcus and Streptococcus, are causal agents in the majority of endophthalmitis cases. The microbiological diagnostic yield of these infections, which has been improved by the use of molecular biology tools (mainly panbacterial PCR) in addition to conventional culture methods, remains imperfect. This study reports the contribution of specific conventional PCR of the Staphylococcus and Streptococcus genera followed by sequencing for the microbiological diagnosis of endophthalmitis.
Specific PCR assays targeting the tuf gene of the Staphylococcus and Streptococcus genera were performed in addition to the reference techniques (conventional culture and panbacterial PCR) on samples of aqueous humor and/or vitreous in patients with endophthalmitis when Staphylococcus or Streptococcus had been identified using reference methods or no identification had been possible.
Out of the 91 samples analyzed, the culture was positive in 38 cases (30 Staphylococcus and 8 Streptococcus) and panbacterial PCR was positive in 59 cases (42 Staphylococcus and 17 Streptococcus). Staphylococcus-specific PCR was positive in 49 cases. Staphylococcus PCR was positive while panbacterial PCR was negative in 7 cases (5 of which were also negative in culture). Conversely, in accordance with culture, panbacterial PCR found a Staphylococcus infection in 1 case, whereas the Staphylococcus PCR was negative. The Streptococcus-specific PCR was positive in 13 cases. The Streptococcus-specific PCR provided no additional diagnosis to the pan-bacterial PCR. Conversely, the pan-bacterial PCR found a Streptococcus infection in 4 cases, whereas the Streptococcus-specific PCR was negative (as was the culture). The specific PCR provided better identification of the species than pan-bacterial in sequencing. In 14 cases, all the analyses remained negative.
The Staphylococcus-specific PCR seemed more sensitive than panbacterial PCR in identifying Staphylococcus causing endophthalmitis. These superior results of the specific technique were not repeated for the identification of the Streptococcus in our experiment. The sensitivity tests performed on different bacterial dilutions confirmed these data. The Staphylococcus- and Streptococcus-specific techniques used in this study were complementary to the panbacterial PCR techniques and improved sensitivity in the identification of Staphylococcus and better identification of the species with sequencing.
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