Enterobacteriae continued.

Shigella genus lab tests

Clear colonies on MacConkey/EMB; Green clear on HE. Suspect if there’s a lactose - and biochemically inert. All produce enterotoxin that cause dysentery

Shigella subgroups + serotypes

A = 15 dysenteriae (type 1 = shiga toxin), B = 8 flexneri, C= 19 boydii D = 1 Sonni

shigellosis/Bacillary dysentary

most spreadable bacterial diarrheas, spread fecal-oral (human natural host). 200 organisms all it takes; Sonni = highest % of US cases

S. dysenteriae

Most virulent species (neurotoxin), least common species isolated in US (found in developing countries

Klebsiella characteristics

lactose +, nonmotile, urase + (weak), produces large gas in TSI

K. pneumoniae

most isolated species of K; causes nosocomial + opportunistic infections, Causes severe/fatal pneuomonia (necrosis, hemorrhage) and UTIs + septicemia (meningitis in newborns)

K. Pneumoniae morphology

capsulated; large mucoid colonies w red pigment on MacConkey, resistant to antibiotics (BL enzymes).

Enterobacter Genus

16 species (cloacae, aerogenes common); found in soil, water/sewage, veggies and gut microbes.

enterobacter infections and morphology

opportunistic (UTIs, resp tract, wounds + uncommon septicemia + meningitis); like klebsiella except motile and ornithine decarboxylase +

Serratia Genus

• 7 out of 10 species matter (Marcescens, nosocomial + opportunistic), all produce Lipase, gelatinase, and DNAse (hydrolytic enzymes).

• Causes pneumo and sept in chemo patients, produces red/orange pigment

Salmonella genus charcteristics

• lactose and sucrose -; suspect if H2S+ colonies that are lactose - on Hektoen enteric Agar

• 2400 + serotypes via Kaufmann-White Scheme

Salmonella clinical syndromes

• Gastroenteritis (most frequent; mild to severe diarrhea, low grade fever w vomit)

• bacteremia/septicemia (S. Choleraesuis invasive, + blood cultures and no gastro signs w high fever)

• Enteric Fevers like S. typhi’s typhoid fever: 1-2 weeks = fever + constipation, + blood, - stool. diarrheal phase = - blood, + stool

• carrier state = spread up to one year after symptoms

Salmonella isolation media

• hektoen, enteric, XLD, Salmonella-Shigella (SS?)

• more selective = Bismuth sulfite and Novobiocin green glucose agar ( is smooth, large and black due to H2S production; red w a zone of clearing)

S. typhi indentification

typhi only one that can be recognized w biochem: trace (curved wedge) H2S in TSI, less biochem active than other serotypes; widal tests fir S typhi O + H antigens

Salmonellosis incidences

• Humans only reservoir for typhi, 400 cases of typhoid fever/year in US.

• Half of all salmonella occur in contaminated chicken

• S. typhimurium 20%, S. enteritidis 18%, S. newport 10%

• water, veggies, fruits, eggs, ice cream, PB, meat; reptiles are colonized, in thier feces

S. enterica arizonae charcteristics

Used to be genus Arizonae. ONPG + (other salmonella -), Malonate +, Dulcitol -; found in reptiles + poultry and causes gastroenteritis and enteric fever

Proteus genus

• found is soil water, fecal contaminated stuff; motile swarming in sheep blood agar; causes UTI’s and wound ifnections

• P. Mirabilis = most common; indole -, suspetible to ampicillin and cephalopods

• P. Vulgaris = indole +; resistant to those

Citrobacter

• resemble salmonella but ONPG + and LDC -;

• C. freundii (complex with other species) and C. diversus = most common

• causes UTIs and resp. tract, wound, gastro and meningitis

Edwardsiella

• found in cold + warm bloods and environment

• main species = E. tarda

• infections = wound in aquatic environment, abscesses to gangrene and gastroenteritis

• resembles E. coli but lactose - and H2S + (similar to salmonella + citrobacter; found in reptiles and freshwater fish)

Yersinia morphology + lab stuff

• small + coccobacilli; grows at 25-32 C; suspect if TSI yellow/orange in 24 hrs

• all species nonmotile at 37C; Y. pestis motile 25-30 C

Yersinia species

• Y. pseudotuberculosis, entreocolitica, pestis (plauge); flea-rodent-flea life cycle. 5-6, 8-14, 19-21st centuries

bubonic Plague

• causes swelling of cervical, axillary, inguinal lymph nodes; Hematogenous spread to organs and tissues => DIC, endotoxic shock, dark discoloration of extremities

• bacteria multiply at site (flea bite, lung or blood)

Bubonic/ Y. pestis diagnosis (lab)

• suspect if febrile patients exposed to rodents/mammals in endemic areas

• gram stains = bi-polar w safety pin appearance; wright stained blood smears

• grows slowly on ordenary media, beaten copper under stereoscope

• TSI = weak acid in slant; no change in deep (yellow/red)

Y. enteroclitica

• endemic in aquatic + animal reservoirs; pigs = human infection

• infections = acute enterocolilits, septicemia (only those w extra iron like sickle cell and thalassemia); blood transfusions

Y. enterocolitica lab

• small lactose - colonies on MacConkey/EMB; cold enrichment of stools enhances recovery (CIN media)