Infectious Disease Compendium

Escherichia

Microbiology

Gram negative rod, it will grow anaerobically so technically it is microaerophilic. There is E. coli, E. albertii, E. blattae, E. fergusonii, E. hermannii, and E. vulneris.

Epidemiologic Risks

Part of the human colonic flora.

O157:H7 is found in cattle stool, which coats your food. The last thing all creatures do as they die is release their bowels. Also outbreaks with spinach (PubMed),  strawberries contaminated with deer poo and swimming in poo filled lakes (any lake a child swim in) (PubMed). And there was an outbreak where the cattle infected rabbits, the rabbits went to a local wildlife park where they infected humans (PubMed). So like Because a Little Bug Went Ka-Choo (Rosetta Stone). And an outbreak due to exposure to cow and horse manure where " Certain behaviors in the patients with primary cases might have contributed to initiation of the outbreak, such as lack of awareness of the risk for disease, inadequate hand washing, and hand-to-mouth behaviors. Ick (PubMed)."

Now people, for reasons that elude me, think drinking raw milk (SBM) is a good thing. There is an underground raw milk trade that functions like a speakeasy during prohibition. The password to get the raw milk is likely 'Swordfish' (YouTube). People also treat cows like condos and own a share of the animal so they can get raw milk legally. And they get the associated infections as well (CDC).

Shiga producing E. coli is also found in venison (PubMed).

About 40% of ESBL E. coli are community acquired with no risk factors (PubMed). This will likely only get worse and makes empiric therapy for serious E. coli infections problematic: go straight to a carbapenem (PubMed)? Not yet.

Healthy Chinese medical students will carry ESBL E. coli for over 4 months (PubMed).

Surfers and body boarders had 3 x the risk of cefotaxime resistant E. coli, likely because they swallow water downstream from sewage treatment plants (PubMed). Not the first time beaches are the source of resistant bacteria from upstream sewage.

ESBL E. coli likely passed back and forth from humans and pet dogs (PubMed). Soooo glad we have pet therapy in the hospital.

Syndromes

1) Focal infections: urologic infections, any intra-abdominal infection, sepsis, pyomyositis in the neutropenic (PubMed).

2) Diarrhea: travelers diarrhea, O157:H7 and O111 can make shiga toxin and are associated with Hemolytic-Uremic Syndrome (HUS), the former in children, the latter in adults. The 2011 outbreak in Europe was O104:H4. HUS may be preventable with daily intestinal lavage with polyethylene glycol (PubMed).

How long are they potentially infective? Patients with HUS had a shorter shedding duration (median, 13–14 days) compared to non-HUS patients (median, 33–34 days). Antimicrobial treatment also significantly reduced shedding duration (PubMed).

Some E. albertii can be enterohemorrhagic or enteropathogenic and misidentified by the lab as E. coli (PubMed), can cause outbreaks (PubMed), and is almost certainly missed by your lab.

Treatment

Depends on the disease and the local resistance patterns. The most reliable agents are aminoglycosides, carbapenems, quinolones and third generation cephalosporins. As a rule, all forms of penicillin as well as tmp/sulfa have too much resistance to use empirically.

In the US, 25% of urine isolates are resistant to tmp/sulfa, 17% to ciprofloxacin (PubMed). And resistance will only increase with time.

And consider cyloserine for resistant E. coli UTI's. Yes, it's a TB drug, but it is effective against gram negative rods (PubMed).

Be wary. ESBL (extended spectrum beta lactamase that hydrolyse most beta-lactams (sparing only cephamycins and carbapenems) carrying E. coli are increasing in frequency and the only reliable antibiotic are carbapenems, including ertapenem (PubMed). Risks for ESBL include health care, urinary catheters and prior antibiotics and if you choose wrong there is increased mortality (PubMed).  If the MIC for an ESBL E. coli to piperacillin/tazobactam is <= 2 the patient will do fine but if higher MICs expect death (PubMed). For bacteremia (or suspected) from an ESBL, carbepenams have less mortality than piperacillin/tazobactam (PubMed). Maybe (PubMed).

For E. coli or K. pneumoniae bloodstream infection with ceftriaxone resistance, INCREASED mortality with piperacillin-tazobactam compared to meropenem (PubMed).

If the organism is an ESBL, DO NOT use cefepime even if susceptible. Won't work as well as carbapenems (PubMed) and avoid piperacillin/tazobactam. Remember that sensitive in the lab does not always mean effective in the patient.

A post hoc analysis (PubMed) suggests the beta lactamase inhibitor combinations (if MIC < 2) are better than carbapenems for treating ESBL producing E. coli (PubMed), but, as the Xigris debacle reminds us, post hoc analysis are often crap and not to be believed.

There is also the New Delhi metallo-beta-lactamase, which inactivates all beta-lactams including carbapenems aka CRE (PubMed); often these are only sensitive to colistin and tigecycline. Ceftazadime-avibactam has a high failure rate with CRE.

There is also meropenem/vaborbactam for some strains, depending on the beta-lactamse.

CRE are perhaps more virulent as well as hard to kill (PubMed).

Travelers diarrhea: ciprofloxacin, 750 mg qd for 1–3 days; azithromycin, 1000 mg in a single dose; or rifaximin, 200 mg tid for 3 days.

Treatment of O157:H7. DON'T. Antibiotics may help precipitate HUS (PubMed). Long term O157:H7 associated with an increased risk for hypertension, renal impairment, and self reported cardiovascular disease (PubMed). About 11% of family members will acquire infection from the index case (PubMed).  Azithromycin will decrease shedding, but whether to treat is uncertain (PubMed).

If you suspect E. coli O157:H7 and its brethren, avoid quinolones as it markedly up regulates toxin in comparison to other antibiotics, including azithromycin with down regulates toxin (PubMed).

Notes

If there is an MDRO, ID consultation is associated with decreased mortality (PubMed). What a concept. Involving physicians who know what they are doing benefits patients.

How long will ESBL carraige last? At least 8 months in a third of patients (PubMed). However, another 12% acquired ESBL in the study. Can't do much about the ebb and flow of normal flora except wash your damn hands before touching patients.

Curious Cases

Relevant links to my Medscape blog

A Bad Two Fer

Playing the Odds

Common and Not So Rare?

True?

Pictures are worth 1000 words

Did Not Believe it at First

Last Update: 09/15/18.