Influence of prgH on the Persistence of Ingested Salmonella enterica in the Leafhopper Macrosteles quadrilineatus

Abstract

Phytophagous insects can encounter Salmonella enterica on contaminated plant surfaces and transmit externally adhered and internalized bacteria on and among leaves. Excretion of ingested S. enterica by the leafhopper Macrosteles quadrilineatus has been previously reported; however, the sites of persistence of ingested bacteria remain undetermined. Fluorescence microscopy revealed the presence and persistence of S. enterica in various organs of M. quadrilineatus fed an inoculated diet for 12 h and then moved to two consecutive noninoculated diets for a total of 48 h. Ingested S. enterica was predominantly observed in the filter chamber, midgut, and Malpighian tubules of M. quadrilineatus dissected immediately after acquisition and at 24-and 48-h post-acquisition access periods (post-AAPs). Additionally, we examined the potential roles of the Salmonella pathogenicity island 1 (SPI-1) and SPI-2 type III secretion systems (T3SSs) in the persistence and excretion of ingested S. enterica. In competition assays, a prgH mutant lacking a functional SPI-1 T3SS was recovered at significantly lower levels than the WT in insect homogenates at 24 h post-AAP, and complementation with prgH restored S. enterica persistence in M. quadrilineatus. Moreover, expression of prgH inside M. quadrilineatus was observed up to 48 post-AAP. No differences were observed between the WT and an ssaK mutant lacking a functional SPI-2 T3SS in insect homogenates or between the WT and either mutant in insect excretions. This study provides novel insight into the presence and persistence of S. enterica inside M. quadrilineatus and demonstrates that the SPI-1 T3SS influences the persistence of the pathogen in the gut of a potential vector. Salmonella enterica is the leading cause of bacterial foodborne illness in the United States (1). In the last few decades, salmonellosis outbreaks attributed to S. enterica-contaminated fresh produce have increased, and produce is now considered the most likely vehicle of disease transmission (2). Plant contamination with S. enterica is thought to primarily occur in the field before harvest, and the pathogen has the ability to adhere, colonize, and persist in and on plant surfaces, in some cases for extended periods (3, 4). Domestic and wild animals represent one of the main entry routes for S. enterica to produce fields, where they can directly introduce the bacterial pathogens to plants or agricultural water through excretion of contaminated waste (3). Additionally, synanthropic and coprophagic insects can introduce human bacterial pathogens to produce fields by dispersing bacteria associated with their exoskeletons onto plant surfaces (5). These events increase the chances that phytophagous insects could encounter a human enteric pathogen as a result of feeding or wandering on contaminated plant surfaces. The abundance and distribution of phytophagous insects within agricultural fields suggest that their contamination could influence the dispersal of enteric pathogens in the field (6).The aster leafhopper, Macro...

Pectobacterium parvum sp. nov., having a Salmonella SPI-1-like Type III secretion system and low virulence

“…S1). Salmonella enterica has been shown to need SPI-1 T3SS to be able to persist inside leaf hopper [ 28 ], P. stewartii subsp. stewartii has been shown to use the SPI-1-like T3SS to colonize its insect vector [ 29 ], and also in other bacterial pathogens this type of T3SS has been linked to persistence in insects [ 30 ].…”

The gut microbiota induces melanin deposits that act as substrates for fimA -mediated aggregation of Salmonella Typhimurium and enhance infection of the German cockroach vector

“…Moreover, S . Typhimurium can actively colonize several other insects, such as house flies and leafhoppers ( 50 , 51 ), and it is of interest to determine the extent to which mechanisms are conserved across these hosts, as well as across other enteric pathogens that cockroaches may acquire in nature.…”

Salmonella enterica changes Macrosteles quadrilineatus feeding behaviors resulting in altered S. enterica distribution on leaves and increased populations

“…Despite S. enterica populations decreasing by 2 logs over a 13-day period upon tomato hosts, M. quadrilineatus enhances transmission of S. enterica from contaminated leaves to clean leaves or adjacent plants within an agriculturally-relevant context 8 , 13 . Furthermore, excretion of viable S. enterica from M. quadrilineatus has also been documented 27 . Yet, how phytophagous insects influence this increase of S. enterica persistence on leaves remains mostly unexamined.…”