Gram negative rods. There is one Salmonella that is subdivided into S. typhii and S. paratyphi, the cause of typhoid fever, and all the other salmonella of which there are over 2300 serotypes, causes of bacillary gastroenteritis aka the Hershey squirts.
Salmonella has 2 species, bongori and enterica; the latter species is divided into 6 subspecies: enterica (I), salamae (II), arizonae (IIIa), diarizonae (IIIb), houtenae (IV), and indica (VI). S. bongori and Salmonella subsp. II-IV have a marked increase in invasive disease compared with I (PubMed).
S. typhii is spread human to human, often from water sources or chronic carriers (esp in the gallbladder). The majority of S. typhii in the US is acquired from the Indian subcontinent (PubMed) and increasingly from Aisa although about 25% of US cases are due to importation of contaminated food (PubMed).
Salmonella Paratyphi A is associated with travel to South and Southeast Asia, and nalidixic acid–resistant infection is associated with travel to South Asia.
Salmonella Paratyphi B infection is associated with travel to the Andean region of South America.
Salmonella Paratyphi C infection is associated with travel to Africa (PubMed).
The other salmonella are commonly found in eggs, chickens, turkeys, frogs, turtles (Pubmed), and reptiles of all kinds. It is rampant in the Congress. There have been outbreaks due to handling animal meat based pet treats (MMWR) and tomatoes (PubMed). Also there was an outbreak associated with raw fish, but it was tuna, not salmon. When I was a kid I though you got Salmonella from eating salmon. Everything, and I mean everything, has a fine layer of human or animal poo on it. Bon appetite.
Playing in sandboxes. Playgrounds are a mixture of children and wildlife, a perfect mix for infectons.
Acid suppression is a risk (PubMed).
Increasingly, outbreaks are associated with raw produce. It is why I only eat deep fried food. And one outbreak with kids eating sand in the playground where wildlife were crapping in. Mmmmm. Sand containing crap.
S. typhii and S. paratyphi: typhoid fever fevers, pulse temperature disassociation, leukopenia, abdominal pain, increased LFT's. A late complication of typhoid fever is perforation of the GI peyers patches.
In sub Saharan Africa, bacteremic non-typhoidal Salmonella is common in kids, esp S. typhimurium and S. enterititis which predominate and have a 25% case fatality rate.
Other salmonella: gastroenteritis with and without fever and bacteremia in the elderly or the immunoincompetent (full text), osteomyelitis in sickle cell patients, infections of aneurisms (it has a propensity for the clot), chronic/relapsing bacteremia in HIV (rarely seen in the era of HAART, requires chronic suppression), acute cystitis, chronic cystitis in Schistosomiasis, a hodgepodge of extra-intestinal infections.
Risk factors for vascular infection are male sex, hypertension, coronary arterial disease, and serogroup C1 infections, and the more you have, the greater the risk (PubMed).
Resistance is increasing to common antibiotics, so susceptibility testing is important. No antibiotic can be expected to be effective anymore (Pubmed). Quinolones (meta analysis suggests quinolones are the best therapy) and third generation cephalosporins are still reliable for most forms of Salmonella infections. BUT. S. typhi in India has a 90% resistant rate to quinolones, but as amoxicillin, trimethoprim/sulfamethoxazole, and chloramphenicol resistance rates have fallen (PubMed). Gatifloxacin (10 mg/kg) dd for 7 days has same cure rates, but has fewer side effects, than chloramphenicol (75 mg/kg per day) qid x 14 days (PubMed).
In Asia quinolone resistance for enteric fever is common (PubMed).
In the West, Salmonella enterica strains have decreased susceptibility to ciprofloxacin; 103 (20.9%) of 492 isolates. The lower susceptibility was associated with ciprofloxacin treatment failures and with serovars and phage types acquired from foreign travel (PubMed).
As in most bacillary diarrhea, treatment for mild to moderate disease probably not indicated. If you decide to treat diarrhea, levofloxacin, 500 mg (or other quinolones) once a day for 7–10 days; or azithromycin, 500 mg once a day for 7 days; treat immunocompromised patients for 14 days (PubMed).
Cystitis, while rare, has a high relapse rate and perhaps should be treated for weeks (PubMed).