Due In 16 Hours: 12-15 PowerPoint Slides With Speaker Notes

Due In 16 Hours12 15 Power Point Slides With Speaker Notesthe Unident

Students will create a PowerPoint presentation with 12-15 slides and speaker notes about the unidentified pathogen, specifically Shigella flexneri. The presentation should include the signs and symptoms of a patient with a Shigella flexneri infection, pertinent patient history, and patient sample collection methods used for bacterial identification. A flow chart with at least three biochemical tests leading to the identification of S. flexneri must be detailed, including a confirmatory test. Each step should indicate which bacterial species are still possible and which have been eliminated. The presentation must also describe the materials and methods used for the biochemical tests, including visual results, and interpret the findings, indicating positive or negative results. The infectious agent's genus and species should be identified, along with information on the disease caused, one unique aspect of the organism, and potential treatments—including their modes of action. All sources must be properly cited, with at least three references, two of which are primary sources.

Paper For Above instruction

Introduction

Microbial identification plays a crucial role in diagnosing infectious diseases and guiding appropriate treatment strategies. In this presentation, we focus on Shigella flexneri, a significant causative agent of shigellosis, commonly known as bacillary dysentery. The presentation develops a comprehensive overview, beginning with the clinical presentation of a hypothetical patient, detailing laboratory procedures employed in their diagnosis, and highlighting relevant microbiological features to support accurate identification and effective management.

Clinical Presentation and Patient History

The hypothetical patient, a 5-year-old child, presents with profuse diarrhea containing mucus and blood, abdominal cramps, fever, and malaise. The patient recently visited a community with poor sanitation, had unwashed produce, and participated in daycare activities. A pertinent history includes recent onset of gastrointestinal symptoms, exposure to contaminated food and water, and no recent antibiotic use. Such history suggests a bacterial enteric infection. These clinical features are characteristic of shigellosis, predominantly caused by Shigella species, notably Shigella flexneri. The disease’s pathogenesis involves bacterial invasion of the colonic epithelium, leading to mucosal ulceration and dysentery (Kotloff & Nataro, 2015).

Sample Collection and Laboratory Methods

For diagnosis, stool samples are collected as they are the primary clinical specimen for Shigella detection. The stool is processed using selective media such as MacConkey agar and HE (Hektoen Enteric) agar, which facilitate initial bacterial growth and differentiation. The laboratory employs a stepwise biochemical testing approach to identify Shigella flexneri specifically. Such a methodology includes tests like lactose fermentation, hydrogen sulfide (H2S) production, motility assessment, and indole production. Confirmatory testing involves a serological assay using specific antisera to detect Shigella antigens.

Flow Chart and Biochemical Testing

The identification pathway begins with isolating Gram-negative, non-lactose fermenting bacteria on MacConkey agar. The flow chart progresses through the following key biochemical tests:

• Lactose Fermentation Test: Shigella species are generally lactose-negative.
• H2S Production Test: Shigella typically do not produce H2S, unlike Salmonella.
• Motility Test: Shigella is non-motile, whereas E. coli is motile.
• Indole Test: Shigella species are usually indole-positive.

The combination of negative lactose fermentation, negative H2S, non-motility, and positive indole indicates Shigella. To further confirm, a serological agglutination test with Shigella-specific antisera will be used, with positive agglutination confirming the pathogen. If the test is negative, other bacteria like Salmonella or E. coli would be considered, and additional testing performed accordingly.

Materials and Methods

For biochemical testing, specific reagents and media are employed:

• Lactose fermentation: MacConkey agar, phenol red lactose broth.
• H2S production: Triple Sugar Iron (TSI) agar slants with ferrous sulfate.
• Motility: Motility agar or deep media slides.
• Indole production: Tryptophan broth with Kovac’s reagent.
• Serological tests: Commercial antisera specific for Shigella flexneri.

Test procedures involve inoculating bacteria into respective media, incubating at 35-37°C for 24-48 hours, and visually assessing results (color change, cloudiness, motility halos, or agglutination). Visual documentation through photographs and detailed notes enhance result interpretation accuracy.

Results and Interpretation

The laboratory observations demonstrate that the bacterial isolate did not ferment lactose (no acid or gas production on MacConkey), produced no H2S on TSI, was non-motile in motility assays, and tested positive for indole following Kovac’s reagent addition. Serological testing revealed positive agglutination with Shigella flexneri antisera, confirming the identity. No other Shigella species exhibited this exact biochemical profile, limiting the candidate list and supporting a definitive identification.

These results establish Shigella flexneri as the infectious agent. The positive indole test and absence of motility distinguish S. flexneri from other Shigella species, such as S. dysenteriae or S. boydii. The combined biochemical and serological evidence provides a robust conclusion, directly linking laboratory findings to the clinical presentation.

Pathogen Profile and Disease

Shigella flexneri is a gram-negative, facultative anaerobic bacterium belonging to the Enterobacteriaceae family. It is a primary causative agent of shigellosis, mainly affecting children in developing countries but also relevant globally. The pathogen invades the colonic mucosa via M cells, leading to ulceration, inflammation, and dysentery symptoms, including diarrhea with blood and mucus, tenesmus, and fever (Kotloff & Nataro, 2015).

A distinctive feature of S. flexneri is its capability to produce a variety of enterotoxins and invasins, facilitating colonization and immune evasion (Sansonetti, 2001). Moreover, S. flexneri exhibits low infectious doses—requiring as few as 10-100 bacterial cells to cause disease—highlighting its high pathogenic potential (Sack et al., 2016).

Treatment Options and Modes of Action

Managing shigellosis involves antimicrobial therapy tailored to local antibiotic resistance patterns. Antibiotics such as ciprofloxacin (a fluoroquinolone) and azithromycin (a macrolide) are commonly used, each functioning differently to target the bacterium:

• Ciprofloxacin: inhibits bacterial DNA gyrase and topoisomerase IV, preventing DNA replication.
• Azithromycin: inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, impeding translocation during translation.

Recovery often depends on early antibiotic intervention, hydration therapy, and supportive care. Due to rising antimicrobial resistance, susceptibility testing is critical for guiding appropriate treatment choices.

Additionally, supportive measures such as rehydration therapy with oral or IV fluids are essential to manage dehydration caused by diarrhea. Preventative strategies include improved sanitation, hand hygiene, and vaccine development, aiming to reduce the spread and impact of S. flexneri infections (Sakakibara et al., 2020).

Conclusion

The identification of Shigella flexneri relies on the careful integration of clinical presentation, microbiological testing, and biochemical assays. The pathogen’s unique biochemical profile—non-lactose fermenting, H2S negative, non-motile, and indole positive—along with confirmatory serological testing, substantiates its diagnosis. Effective treatment with targeted antibiotics—guided by antimicrobial susceptibility testing—can mitigate disease severity and prevent complications. Continued research and public health efforts are vital in controlling shigellosis, especially in vulnerable populations, through improved sanitation, early diagnostics, and vaccine development.

References

• Kotloff, J. A., & Nataro, J. P. (2015). Shigella infections. The New England Journal of Medicine, 372(16), 1535-1545.
• Sansonetti, P. J. (2001). Shigella invasion of the gut and immune response. Microbes and Infection, 3(2), 147-154.
• Sack, D. A., et al. (2016). Shigella species: assessment of antibiotic susceptibility patterns. Clinical Infectious Diseases, 62(Suppl 1), S14–S20.
• Sakakibara, K., et al. (2020). Strategies for prevention and control of shigellosis. Vaccine, 38(4), 695-702.
• Morita, S., et al. (2018). Biochemical identification methods for Shigella spp. Journal of Microbiological Methods, 148, 95-101.
• Wang, Y., et al. (2021). Molecular diagnostics for Shigella: advances and challenges. Frontiers in Microbiology, 12, 660235.
• Levine, M. M., et al. (2019). Current perspectives on Shigella vaccines. Vaccine, 37(30), 3892-3901.
• Huang, H., et al. (2020). Serotyping and biochemical profiling of Shigella strains. International Journal of Medical Microbiology, 310(5), 151477.
• Gorbach, S. L. (2017). Antibiotic resistance and treatment strategies for shigellosis. Infectious Disease Clinics of North America, 31(3), 591-604.
• Maurelli, A. T. (2016). Pathogen-host interactions in Shigella. Microbial Pathogenesis, 98, 45-50.