AST - Urine| AST - Urine |
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| Disclaimer: Please consult most recent CLSI guidelines and SOPs for your laboratory. See CLSI information page. See E. coli AST Canada Survey 2008 | ||
| YEAR | CRITIQUE | SUMMARY |
| 2010 | M101-1 | Midstream urine sample from 82 year old patient from long term facility care: > 100 x 106 cfu/L Streptococcus constellatus.
It was anticipated that thelaboratories would recognize this organism as an unlikely pathogen in this patient and report the growth with a comment about the clinical relevance. In the elderly, contamination with streptococci in the labia or urogenital folds may lead to “flase-positive” urine cultures in those with asymptomatic bacteriuria. These should not be treated as uropathogens, unless the isolate is repeated and the patient is symptomatic. |
| 2010 | M094-1 | Catheter Urine sample from patient with neurogenic bladder: > 100 x 106 cfu/L Proteus penneri and > 100 x 106 cfu/L Enterococcus faecalis.
Susceptibility testing should be performed in both organisms. Vancomycin resistance screening is desired for Enterococus species given the increased risk of these patients carrying VRE. |
| 2009 | M092-1 | MSU: > 100 x 106 cfu/L Morganella morganii |
| 2009 | M084-1 | MSU Enterococcus faecalis With the increasing prevalence of resistance in enterococci susceptibility testing is necessary. The CMPT Microbiology Advisory Committee endorses susceptibility testing of enterococci. Reporting an AST comment only is no longer an acceptable practice. |
| 2008 | M082-1 | Midstream urine: > 100 x 106 cfu/L coagulase-negative staphylococcus (Staphylococcus epidermidis)(ungraded) Reference laboratory consensus was not attained, therefore this component of the challenge was not acceptable for grading. Of the laboratories that performed and reported AST results, all of them reported oxacillin as resistant (n=60 laboratories), and nitrofurantoin (n=61), trimethoprim-sulfamethoxazole (n=71), and vancomycin as susceptible (n=36). |
| 2007 | M072-1 | Enterococcus faecalis One participant reported results for penicillin, and not ampicillin
or amoxicillin, and received a grade of 1. Ampicillin is the penicillin
of choice for treating E. faecalis and ampicillin urinary levels are high even in the presence of markedly reduced renal function. Ampicillin/amoxicillin are 2-10 times more active than penicillin against E. faecalis. . Because of cost and ease of use, oral ampicillin or amoxicillin are clearly superior to oral penicillin for treatment of UTI |
| M071-2 | MRSA
(community acquired MRSA) Although S. aureus represents
only 2% of the etiologic agents for positive cultures for urines
evaluated from outpatients, it is critical that when the strain
is an MRSA that it is accurately identified and reported.It is not
uncommon for S. aureus isolates from urines to be MRSA.
This sample was acceptable for grading as out of 15 reference laboratories
all reported oxacillin resistant, 13 reported vancomycin susceptible,
and 14 reported trimethoprim-sulfamethoxazole susceptible. |
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| M064-3 | MSU E. coli The E. coli in this challenge was
broadly resistant but was not an ESBL producer. Six of 15 reference
laboratories made no comment and the remainder were split fairly evenly
with the reporting of “ESBL positive” (4 laboratories),
ESBL negative (3 laboratories), and AmpC positive (2 laboratories),
all with/without further clarifying comments. The reported results
received from all category A and B laboratories also reflects the
reporting of the reference laboratories. No comment was received from
25% (15 A, 13 B) of laboratories, isolates were referred for further
testing by 29% (16 A, 17 B) of laboratories, and the remaining 46%
reported ESBL positive (28 laboratories [22 A, 6B]), ESBL negative
(20 laboratories [16 A, 4B]), and AmpC positive (5 laboratories [4A,
1B]), 1 also reporting ESBL positive) with or without additional comments”.
A variety of comments with reference to the possibility of different
mechanisms of resistance (e.g., ESBL, beta-lactamase hyperproducer)
were also appended by many laboratories. Guidelines and procedural details can be found in the 2007 CLSI document M100-S17 page 37 (disk diffusion) and p. 99 (MIC Testing) and CMPT critique M024-3, February 2003 . These describe both preliminary screening tests and phenotypic confirmation tests. CLSI also states “The decision to perform ESBL screening tests on all urine isolates should be made on an institutional basis, considering prevalence, therapy, and infection control issues.” There are no CLSI guidelines that detail screening or confirmatory methods that can be used to detect AmpC beta-lactamases or other mechanisms of resistance. The presence of AmpC mediated resistance is usually inferred when the organism is resistant to cefoxitin and when the resistance to 3rd-generation cephalosporins is not inactivated by clavulanic acid, but there are no clear criteria on how to define this. The reporting of susceptibility or resistance to 3rd-generation cephalosporins in the absence of ESBLs is unclear. |
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| 2006 | M063-1 | MSU Proteus mirabilis: Historically, the indole-negative Proteus mirabilis strains were generally more susceptible
than the indole-positive Proteus vulgaris strains. Proteus species are intrinsically resistant to nitrofurantoin and tetracycline,
but were usually susceptible to the ß-lactams, aminoglycosides,
trimethoprim-sulfamethoxazole, and ciprofloxacin; however, this pattern
is changing. Acquired resistance to ß-lactams is usually enzyme
mediated. The most common plasmid mediated ß-lactamases are
the TEM penicillinases. Mutants of the TEM penicillinases are associated
with extended-spectrum beta-lactamase production (ESBL). Co-resistance
to aminoglycosides, fluoroquinolones and trimethoprim sulfamethoxazole
have been reported in ESBL strains, making treatment more challenging
. Wenzel et al. presented data in 2003 which showed increasing resistance
to ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole independent
of ESBL production. Therapy for lower urinary tract infection includes short-term therapy with trimethoprim-sulfamethoxazole or ciprofloxacin. Long-term therapy includes amoxicillin, cephalexin, trimethoprim-sulfamethoxazole or trimethoprim. Susceptibility testing should be performed according to the CSLI guidelines which include the testing of fluoroquinolones for urinary isolates. Some laboratories may wish to suppress reporting of fluoroquinolone results in a effort to discourage the overuse of this group. However, it might be useful to report resistant fluoroquinolone results since this group is widely used in community acquired infections. Monitoring of susceptibility patterns can be a useful tool in aiding empiric therapy and detecting emerging resistance in these and other organisms. 2007 CLSI Guidelines M100-S17 p. 33 "Screening of Proteus mirabilis for ESBL production is recommended only when it is deemed cliniclly relevant (e.g., a bacteremic isolate)." |
| M062-3 | Catheter (in and out) urine: >100 x 106 cfu/L: Klebsiella pneumoniae with ESBL mediated resistance. Unfortunately, routine susceptibility testing may not detect the presence of ESBLs and this may result in the prevalence being underestimated in some jurisdictions | |
| M061-1 | MSU: >100 x 106 cfu/L Escherichia coli (resistant to ampicillin, susceptible to cephalothin and cefazolin) - see M24-1 and M011-1 comment. | |
| 2005 | M053-1 | ungraded- MSU-penicillin allergic patient: >100 x 106 cfu/L Group B Streptococci (S. agalactiae) The CMPT committee endorses the use of the following comment: “Group B streptococci can be considered as susceptible to ampicillin, amoxicillin, all cephalosporins, and vancomycin. For individuals with significant allergy to penicillins, less than 1% of Group B streptococci are resistant to fluoroquinolones” |
| M051-1 | Catheter
urine: >100 x 106 cfu/L Escherichia coli and Morganella morganii AST of M. morganii with nitrofurantoin may be problematic especially with small inocula on automated systems, and laboratories may overestimate susceptibility to nitrofurantoin. |
|
| 2004 | M042-1 | ungraded AST- Urine 22- year old female Staphylococcus saprophyticus |
| 2003 | M034-1 | Catheter urine Pseudomonas aeruginosa (resistant to ciprofloxacin; sensitive to gentamicin, ceftazidime, piperacillin and piperacillin-tazobactam) Inappropriate antimicrobial therapy could result if an incorrect identification (including reporting either Pseudomonas species or 'coliforms') was reported to the clinician. |
| M033-1 | MSU - Klebsiella pneumoniae with ESBL mediated resistance. | |
| M032-1 | Catheter urine - Candida tropicalis. If isolates of yeast are repeatedly isolated from clinical specimens while on therapy, it is important to consider speciation, and performing tests to determine the degree of susceptibility particularly to the triazole antifungal agents. | |
| 2002 | M024-3 | E. coli with ESBL mediated resistance - ESBL Screening is detailed in this critique. |
| M023-1 | Urine catheter E. coli & K. pneumoniae - mixed culture susceptibilities | |
| M022-4 | Enterobacter cloacae with an ampC chromosomal resistance | |
| M021-1 | Proteus mirabilis, CMPT recommends that every antimicrobial profile reported for clinically significant urine specimen isolates include a fluoroquinolone result. | |
| 2001 | M014-1 | Providencia stuartii - is generally considered one of the most naturally resistant of gram-negative bacilli that cause urinary infections. Laboratories should review their antibiotic cascades to reduce reporting of agents that are both expensive and may promote resistance development if used unwisely. |
| M012-1 | Group B streptococci (S. agalactiae) The CMPT committee endorses the use of the following comment: “Group B Streptococci can be considered as susceptible to ampicillin, amoxicillin, all cephalosporins, and vancomycin. For individuals with significant allergy to penicillins, Group B Streptococci are susceptible to all fluoroquinolones” . NCCLS M100 S11 January 2001 guidelines do not recommend routine testing for clinical purposes as resistant strains of Group B streptococcal isolates have not been recognized. Disc diffusion and dilution methods for susceptibility testing are available. |
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| M011-1 | E. coli, resistant to cephalothin, susceptible to cefazolin. In an outpatient setting the oral form of cephalothin (cephalexin [Keflex]), might be used based on a cefazolin result that is not entirely predictive of susceptibility of the other cephalosporin. CMPT strongly suggests that both agents are tested and reported in these clinical situations. | |
| 2000 | M24-1 | E. coli (resistant to ampicillin, susceptible to cephalothin and cefazolin) - see M011-1 comment. |
| M23-1 | E. coli - ESBL mediated resistance | |
| M22-1 | E. coli, resistant to cephalothin, susceptible to cefazolin | |
| M21-1 | E. coli - susceptible to ampicillin, cephalothin, cefazolin,, & SXT; resistant to gentamicin | |
| 1999 | M94-1 | Citrobacter koseri-
With respect to cefazolin or cephalothin susceptibilities, while it
is commonplace for other Citrobacter species to produce inducible
beta-lactamase, it is unusual in Citrobacter koseri. Recent (2000) query to the Surveillance Network (TSN™ ) Database indicates that approximately 5-10% of C. koseri strains are resistant. Strains that are sensitive to first-generation cephalosporins tend not to be cephalosporinase-producers. Reporting strategies—for those strains that test as sensitive to second-generation drugs but may be cephalosporinase-producers—are to: routinely report as resistant, to report as sensitive with a cautionary note, or to report as sensitive. The CMPT committee promotes reporting these isolates as sensitive with a cautionary note. |