AST- Wounds, Biopsies, Abscesses, Genital
HOME      CONTACT US      EQA PROGRAMS      RESULTS     CRITIQUES      NEWSLETTER      SITE MAP  
Click on the drop-down button for links to critiques from other sources

Contact us to obtain critiques older than 5 years.
Scroll down to find Critique number of older challenges and a brief description.
Some older archived critiques are included in this list, but CMPT advises visitors to also consult recent literature.
Disclaimer: Please consult most recent CLSI guidelines and SOPs for your laboratory. See CLSI information page.
YEAR CRITIQUE SUMMARY See revised ID Table 7 (Jan 2007)
2010 M101-5 Stenotrophomonas maltophilia - Foot (wound) swab: CLSI does have interpretive guidelines for testing S. maltophilia.  In M043-3 it was decided that it was important and necessary to do susceptibility testing of SXT in serious infections because of the possibility of resistance. 
2010 M101-2 Pseudomonas aeruginosa - Ear swab: Whether performing antimicrobial susceptibility testing by Kirby Bauer disc diffusion or by MIC, both are designed to help guide therapy based on achievable blood and tissue levels for systemic treatment. There is no value in performing AST in cases of non-malignant otitis externa as it is generally treated with topical antibiotics resulting in little systemic absorption. 
2010 M094-2

Cervical swab – GC requested:  Clinical relevancy challenge. No GC isolated.
The clinically relevant information reported to the physician should convey that the specimen was specifically investigated for Neisseria gonorrhoeae.

Neisseria gonorrhoeae and Chlamydia trachomatis are the major pathogens causing cervicitis. Normal flora, including yeast, BV and Group B streptococcus should not be worked up or reported.
2009 M093-2

Aeromonas veronii biovar sobria — leg wound
Extra intestinal isolates of Aeromonas veronii bv. sobria must be tested for antimicrobial susceptibility; methods and breakpoints are addressed in the CLSI document M45-A.
The clinically relevant Aeromonas spp. are uniformly resistant to penicillin and ampicillin; are often resistant to cefazolin and ticarcillin; and are often susceptible to third-generation cephalosporins aztreonam, and carbapenems.

2009 M092-3 Group B streptococcus from a vag/rectal swab
2008 M081-3 Acinetobacter baumannii Increasing antibiotic resistance has been reported. Treatments of choice include imipenem, meropenem, piperacillin-tazobactam, quinolones, ceftazidime, aminoglycosides, colistin, polymyxin B and trimethoprim-sulfamethoxazole (SXT). Laboratory testing for imipenem is not reliable. Some reports indicate an increasing resistance to tobramycin and amikacin1. Ertapenem has no activity against Acinetobacter. Combination therapy of a carbapenem (imipenem or meropenem) or quinolone or β-lactam/β-lactamase inhibitor with an aminoglycoside may result in bactericidal synergy for serious infections. Resistance patterns vary according to species and geographic areas, and susceptibility testing must be performed for clinically significant isolates.
  M081-4 Propionibacterium acnes CSF shunt When organisms are isolated from sterile sites, such as CSF and blood cultures, susceptibility testing needs to be performed; laboratories not able to perform anaerobic susceptibilities need to refer the isolate. A susceptibility comment alone is not sufficient.P. acnes is usually susceptible to penicillin, tetracyclines, chloramphenicol, erythromycin, and vancomycin.  As with most other aerotolerant, anaerobic, gram-positive rods, propionibacteria are resistant to metronidazole.
  M081-5 Burkholderia cepacia bronchial alveolar lavage ICU patient, not cystic fibrosis patient
2007 M073-3
Male, urethritis,
treatment failure

Neisseria gonorrhoeae It tested beta-lactamase negative. As there can be wide geographical variations in susceptibility patterns, treatment of individuals is based on regional and national guidelines based on susceptibility patterns of a series of isolates. It is important to submit isolates to reference laboratories in order that this data can be collected. N. gonorrhoeae resistance occurs both as chromosomally mediated resistance to a variety of antimicrobials and plasmid-mediated resistance to penicillin (BLT +) and to tetracycline 8. CLSI has guidelines for both disk diffusion and agar dilution methodology.  
Read AST information CCDR weekly Feb 2009 The study findings underscore the current recommendations in Canada not to use quinolones for treatment of N. gonorrhoeae infections.
  M073-5
Pancreatic Abscesss		 Enterobacter cloacae (ampC) and C. tertium.
Enterobacter: For those species known to have potential for inducible beta-lactamase resistance, laboratories should be careful to report antimicrobial resistance when it occurs to agents commonly used for treatment of specific infections, and to warn physicians that these species may develop resistance during therapy with some beta-lactam agents. C. tertium:Amongst Clostridium sp., C. tertium has an unusual susceptibility pattern as it is resistant to clindamycin, metronidazole, and  β-lactam antibiotics.
  M072-2
Infected finger 		Staphylococcus aureus Cloxacillin or a first-generation cephalosporin is the drug of choice for most S. aureus infections.  However, where MRSA is a possibility, or the patient has a history of allergy to penicillin other agents such as clindamycin or trimethoprim–sulfamethoxazole may be used.  Clindamycin has good bone and tissue penetration and is therefore often the drug used in these situations.  A concern with the use of clindamycin is the induction of resistance that may occur during treatment. See D zone test
  M064-4
Wound - cat bite

Pasteurella multocida Susceptibility testing was not required for this challenge.
CLSI recently published a laboratory guideline (2006 M45-A) for the antimicrobial susceptibility testing of fastidious or rarely encountered bacteria.
CLSI recommends that isolates be tested for ß-lactamase activity using a chromogenic, cephalosporin-based method such as nitrocefin.

2006 M062-2
Bartholin's abscess drain 		Haemophilus influenzae  Each laboratory should have an indication of the local prevalence of BLNAR strains if it is to rely on beta-lactamase testing to predict ampicillin susceptibility. The 65 category A laboratories and 19 category B laboratories that reported negative beta-lactamase testing results each received a grade of 4/4.; one category B laboratory received a grade of zero for reporting a positive beta-lactamase result.
2005 M054-2
Ear		 (malignant otitis externa): Pseudomonas aeruginosa
(AST maximum grade=16): Reporting a sensitive result for ceftazidime, gentamicin/tobramycin, ciprofloxacin, and piperacillin/piperacillin-tazobactam/ticarcillin/ticarcillin-clavulanic acid each received a grade of 4.
  M053-2
Leg (bullous cellulitis)		 group A streptococcus / Streptococcus pyogenes
S. pyogenes remains universally susceptible to beta-lactam antibiotics, and treatment of superficial infections with penicillin is still recommended. In the penicillin allergic patient, or in the event of treatment failure, erythromycin and clindamycin are alternative choices for treatment. In future challenges such as this, participants will be expected to report susceptibility results.
  M053-5
Wound - abdominal abscess		 Enterobacter aerogenes and Clostridium septicum
All 15 reference laboratories performed susceptibility testing for E. aerogenes and reported ampicillin/amoxicillin as resistant, 1st-generation cephalosporins as resistant and gentamicin, ciprofloxacin, and SXT (n=14) as sensitive. Twenty-four laboratories commented that “E. aerogenes exhibits an inducible beta-lactamase and should not be treated with cephalosporins as this will promote further resistance that may lead to clinical failure.” AST for C. septicum were not graded.
  M052-5
Lung abscess		 Streptococcus milleri group - Reports of decreased penicillin susceptibility amongst the viridans streptococci, including the ‘S. milleri’ group, dictate the importance of referring this isolate for antibiotic susceptibility testing if it cannot be done in-house. CLSI (formerly NCCLS) recommends penicillin susceptibility should be tested with an MIC method. S. milleri group isolates, regardless of species remain generally susceptible to cefotaxime, vancomycin, trimethoprim-sulfamethoxazole, and ciprofloxacin. Some strains may be resistant to erythromycin and clindamycin.
2004 M043-2 Wound (impetigo) MRSA and group A streptococci.
MRSA: In light of the recent literature it may be prudent for laboratories to either begin screening or refer their MRSA isolates for vancomycin resistance.
GAS: With increased beta-lactam allergies in the general population, and in the case of a multipathogen infection, importance has been placed on erythromycin susceptibility testing. Increased rates of erythromycin resistance among group A streptococci has been reported world-wide. In Canada, studies have uncovered rates of resistance of 14%, with some laboratories quoting rates even higher. An inducible or constitutive cross resistance to clindamycin may or may not be present, depending on the mechanism of resistance. Inducible clindamycin resistance can be detected using a disk approximation test using clindamycin and erythromycin, and looking for flattening of the clindamycin zone. Organisms that show this flattening are demonstrating inducible clindamycin resistance and should be re reported as ‘clindamycin resistant'. Macrolide resistance has been shown to be more frequently associated with strains of S. pyogenes isolated from invasive infections as opposed to pharyngitis.
2003 M033-2
Leg cellulitis		 Enterobacter sakazakii - Enterobacter sp. have a high likelihood of carrying a gene for chromosomally encoded beta-lactamase (AmpC), which is active primarily on antibiotics including ampicillin and 1st-generation cephalosporins.
  M033-2
Leg cellulitis		 Pasteurella multocida - Reports must include a comment indicating "Pasteurella sp. are usually resistant to 1st-generation cephalosporins."
  M032-4
Brain abscess		 S. milleri group and Peptostreptococcus magnus-Due to the mixed bacterial nature of brain abscess infections, two or more antibiotic agents must be used in combination for a minimum of 8-12 weeks in order to not have a relapse. Only report antibiotics that penetrate across the blood-brain barrier and that will be effective within the central nervous system.
2002 M023-2 human bite
Face wound-human bite Haemophilus influenzae - beta-lactamase positive
  M011-3 Abdominal wound S. aureus and Enterococcus gallinarum. S. aureus that are clearly sensitive to penicillin should have a beta-lactamase test performed and reported. With respect to the ambiguity of the significance of enterococci in superficial swab specimens, susceptibility testing was not graded. The isolate was susceptible to penicillin/ampicillin and had low level resistance to vancomycin. See VRE Screen critiques