Salmonella Infection (Salmonellosis)

Most salmonellosis is a self-limiting gastroenteritis, and the patient who lands in trouble is the one who gets dry. Your priority is fluids and electrolytes, watching the very young and the elderly hardest, and good hand hygiene so it stops with this patient. Reserve antibiotics for invasive disease.

Salmonella are gram-negative motile, non-sporulating, straight-rod bacteria that cause upset stomach, diarrhea, fever, and abdominal cramps. The illness they cause is salmonellosis. The bacteria were named after the American scientist Dr. Daniel E. Salmon, who described it in 1885.

What Is Salmonellosis?

Salmonellosis, the illness caused by Salmonella, usually produces a mild to severe diarrheal illness known as acute gastroenteritis.

Salmonellae are gram-negative motile, nonsporulating, straight-rod bacteria. The genus is named after Daniel E. Salmon, an American veterinarian who first isolated Salmonella choleraesuis from pigs with hog cholera in 1884. The two species are Salmonella enterica and Salmonella bongori. They threaten the food industry because they adapt to environments far different from where they normally grow. When infection becomes invasive, it can reach the bloodstream, bone, joints, brain, nervous system, or other internal organs.

Pathophysiology

The genus Salmonella belongs to the family Enterobacteriaceae.

The cycle starts after the microbes are ingested. The bacteria pass through the stomach to the small intestine and attach by fimbriae or pili to cells lining the intestinal lumen, selectively targeting the specialized M cells of the Peyer patches. Receptor-mediated endocytosis internalizes them and transports them in phagosomes to the lamina propria, where they are released and induce an influx of macrophages (typhoidal strains) or neutrophils (nontyphoidal strains). Through cytokine release and mononuclear cell migration, S typhi spreads through the reticuloendothelial system, mainly to the liver, spleen, and bone marrow. Within 14 days, the bacteria reach the bloodstream and seed secondary foci such as splenic abscess and endocarditis. Nontyphoidal salmonellae generally provoke a localized response, while S typhi and other virulent strains invade deeper tissue via lymphatics and capillaries and trigger a major immune response.

Classification

Salmonella are classified as typhoidal or nontyphoidal by serotype. Typhoidal serotypes cause typhoid or paratyphoid fever and include Typhi, Paratyphi A, Paratyphi B, and Paratyphi C. Nontyphoidal covers all other serotypes.

Causes

Salmonellosis is caused by all nontyphoid serotypes of the genus except S typhi and Salmonella paratyphi A, B, and C.

Contaminated food or water spreads it; Salmonella usually reaches humans through foods contaminated with small amounts of animal feces, and food handlers can transfer it from raw meat or poultry to other foods if they do not wash their hands between steps. Contact with infected animals also spreads it; Salmonella lives in the intestinal tracts of humans and other animals, including poultry and other birds, amphibians, and reptiles, and people can be infected after contact with animals or their feces without washing their hands.

Statistics and Incidences

CDC estimates approximately 1.35 million illnesses and 420 deaths from non-typhoidal Salmonella annually in the United States.

FoodNet reported an annual incidence of 15.2 illnesses per 100,000 individuals. Compared to 2010-2012, non-typhoidal Salmonella infection fell 9% in 2013. Infection is more common in summer (June, July, and August) than winter. Children under 5 years old are the most likely to get infected; children 5 years and younger, adults over 65, and people with weakened immune systems are the most likely to have severe infection. Salmonella accounted for the most hospitalizations (64%) in outbreaks with a confirmed cause. The mortality rate for S enteritidis outbreaks in the United States from 1985-1991 was 0.4%, and case-fatality rates were 70 times higher in nursing homes and hospitals.

Clinical Manifestations

Most people with a Salmonella infection have diarrhea, fever, and stomach cramps.

Diarrhea may last several days and lead to severe dehydration, especially in infants and children under 2 years old and adults over 65. Fever often comes with prostration and an apathetic-lethargic state (the tuphos of the ancient Greeks). Abdominal tenderness (approximately 50%), mild hepatosplenomegaly (approximately 50%), and a coated tongue are common in typhoid fever.

Assessment and Diagnostic Findings

Infection is diagnosed when a lab detects Salmonella in a person's stool, body tissue, or fluids.

Modern blood culture systems are 80-100% accurate at detecting bacteremia; as disease duration increases, blood culture sensitivity falls while stool isolation sensitivity rises. Freshly passed stool is the preferred specimen for nontyphoidal species; because S typhi stool carriage can be prolonged, interpret positive results cautiously and diagnose only with typical clinical findings. Bone marrow aspirate and culture beats blood culture because the bacterial concentration in bone marrow is 10 times that of peripheral blood.

Medical Management

Salmonella gastroenteritis is usually self-limiting.

Replace fluid and electrolytes in severe cases, and have patients drink extra fluids as long as diarrhea lasts. Consult an infectious disease specialist for bacteremia, endovascular or CNS infection, strong suspicion of typhoid fever, or suspected or documented antimicrobial resistance.

Pharmacological Management

The goals are to eradicate infection, reduce morbidity, and prevent complications. Empiric antimicrobial therapy must be comprehensive and cover all likely pathogens in the clinical setting.

Nursing Management

Nursing Assessment

History. Salmonella typically produces one of three syndromes: nontyphoidal enterocolitis, nontyphoidal focal disease, or typhoid (enteric) fever.

Physical exam. Nontyphoidal gastroenteritis usually shows non-bloody loose stool or watery diarrhea; typhoid fever may bring pink, blanchable, slightly raised macules (rose spots) on the chest and abdomen.

Nursing Diagnosis

Based on assessment, the major diagnoses are: Diarrhea related to bacterial infection; Deficient Knowledge related to a new disorder, treatment, and unfamiliarity with information resources; Risk for Fluid Volume Deficit; and Imbalanced Nutrition: Less Than Body Requirements related to nausea and vomiting.

Nursing Care Planning and Goals

The client has a negative stool culture, passes soft, formed stool no more than 3 times a day, and verbalizes understanding of the causes, transmission, and symptom management of salmonellosis. The client stays normovolemic (systolic BP 90 mm Hg or greater, no orthostasis, HR 60 to 100 beats per minute, urine output greater than 30 ml per hour, normal skin turgor) and has improved nutritional intake without nausea and vomiting.

Nursing Interventions

Relieve diarrhea. Teach hand washing after each bowel movement and before preparing food for others. Encourage fluid intake of 1.5 to 2.5 liters per 24 hours plus 200 ml for each loose stool in adults unless contraindicated, encourage potassium-rich foods, and give antidiarrheals as prescribed.

Educate patient and family. Assess their knowledge of salmonellosis, its transmission, and treatment. Teach the causes and treatments, the importance of hand washing after toileting and perianal hygiene and before preparing food for others, and food preparation and storage methods that reduce contamination.

Prevent fluid volume deficit. Assess skin turgor and mucous membranes for dehydration, monitor BP for orthostatic changes when moving from supine to standing, have the client weigh daily on the same scale at the same time in the same clothing, and give antiemetics as ordered.

Improve nutrition. Measure weight, record vomiting amount and frequency, monitor food intake, provide a diverse diet to meet needs, and give parenteral fluids as ordered.

Evaluation

Goals are met when the client has a negative stool culture, passes soft, formed stool no more than 3 times a day, verbalizes understanding of the causes, transmission, and management, stays normovolemic (systolic BP 90 mm Hg or greater, no orthostasis, HR 60 to 100 beats per minute, urine output greater than 30 ml per hour, normal skin turgor), and has improved nutritional intake without nausea and vomiting.

Documentation Guidelines

Document individual findings and behaviors, cultural and religious beliefs and expectations, the plan of care, the teaching plan, responses to interventions and teaching, and progress toward outcomes.

Key Points

Salmonellosis usually produces a mild to severe diarrheal illness, acute gastroenteritis. The bacteria adapt to environments far different from where they normally grow, threatening the food industry. They are classified as typhoidal or nontyphoidal by serotype. Transmission is usually through foods contaminated with small amounts of animal feces, and through contact with animals or their feces without hand washing. CDC estimates approximately 1.35 million illnesses and 420 deaths from non-typhoidal Salmonella annually in the United States. Most patients have diarrhea, fever, and stomach cramps. Diagnosis comes from detecting Salmonella in stool, tissue, or fluids. Replace fluid and electrolytes in severe cases and keep extra fluids going as long as diarrhea lasts. Pharmacotherapy aims to eradicate infection, reduce morbidity, and prevent complications.