M45: INFREQUENTLY ISOLATED OR FASTIDIOUS BACTERIA Romney Humphries, PhD D(ABMM) UCLA Clinical Microbiology
Under Revision!
ORGANISMS INCLUDED IN M45 VS. M100 M100 Enterobacteriaceae Pseudomonas aeruginosa Acinetobacter spp M45 Abiotrophia / Granulicatella Aeromonas / Pleisiomonas Bacillus spp. (not B. anthracis) Burkholderia cepacia Campylobacter jejuni / coli Pediococcus S. maltophilia Corynebacterium spp. Vibrio spp Other Non-Enterobacteriaceae Erysipelothrix rhusiopathiae Agents of Bioterrorism Staphylococcus spp. Enterococcus H.influenzae / parainfluenzae Streptococcus spp, β hemolytic Streptococcus spp, viridans group Neisseria meningitidis Anaerobes HACEK group Helicobacter pylori Lactobacillus Leuconostoc Listeria monocytogenes Moraxella catarrhalis Pasteurella spp. Don t test these!!
M100 VS. M45 Breakpoints Established from: Microbiological data Clinical data Pharmacodynamic data Method described in M23 Standard Many breakpoints Adapted from M100 breakpoints. Breakpoints based on: Literature search Clinical experience Does not follow M23 process Guideline
FASTIDIOUS ORGANISMS? Require media supplemented with blood or blood components Possibly need an atmosphere other than ambient air (eg, 5% CO2) NOTE: CO 2 lowers the ph of media: - aminoglycoside MICs high - quinolone MICs high - clindamycin MICs high - penicillin MICs low - macrolide MIC low
ORGANISMS THAT USE STANDARD TEST METHODS Enterobacteriaceae methods (MIC / DD) Aeromonas / Pleisiomonas Streptococcus methods (MIC only) Streptococcus methods Streptococcus methods (no CO2, if requires CO2, don t use DD) Vibrio spp. Corynebacterium spp E. rhusiopathiae HACEK group Lactobacillus Leuconostoc Listeria monocytogenes Pediococcus Moraxella catarrhalis Pasteurella spp.
ORGANISMS THAT USE SPECIAL TEST METHODS Abiotrophia / Granulicatella* Campylobacter CAMHB with LHB + 0.0015 pyridoxal CAMHB with LHB or BMHA, but microaerobic conditions / 42C H. pylori** Agar dilution with MHA and aged sheep blood *These should be sent to a reference laboratory / only performed by those with experience with AST for these organisms ** Send to a reference laboratory, if testing indicated!
SUMMARY OF TEST CONDITIONS
WHEN DO I TEST THESE ORGANISMS? Only if: Infection that warrants antimicrobial therapy Susceptibility cannot be reliably predicted Many of the organisms in M45 are: Part of the normal human microbiota: Corynebacterium Abiotrophia Lactobacillus Pediococcus Leuconostoc Environmental: Bacillus spp. Have a controversial need for AST: Vibrio spp (from stool) Aeromonas (from stool) Campylobacter (from stool) H. pylori Don t test routinely; Don t test if isolated from nonsterile / superficial sites Don t test if not in pure culture Test with ID / physician consultation
CASE 1 69 year old woman with fever, nausea, vomiting and diarrhea. Diarrhea started 5 days ago, vomiting 4 days ago Stool Culture: No salmonella, shigella or campylobacter isolated. Aeromonas hydrophila Is susceptibility testing warranted for the A. hydrophila?
CASE 2 9 year old with otocephalic mandibular syndrome undergoes reconstructive surgery Venous congestion is observed after the surgery Leeches are applied + ciprofloxacin prophylaxis Presents 3 days later with purulent drainage from surgical site Wound cultures collected: Anaerobe Culture Aerobe Culture Prevotella Morganella morganii B. fragilis Aeromonas hydrophila Is susceptibility testing warranted for the A. hydrophila? And if so, how do we approach this?
M45 GUIDANCE The need for susceptibility testing of Aeromonas and Vibrio spp. isolates recovered from feces is controversial. Testing should only be undertaken in consultation with an infectious disease-trained physician or other expert clinicians who can assist in determining if susceptibility testing is needed in the management of a specific patient, and in the interpretation of any results generated. Generally, testing of these organisms should be limited to isolates recovered from normally sterile sites, [or] serious wound infections
TESTING GUIDANCE FOR AEROMONAS SPP. 1. Perform AST just like for Enterobacteriaceae (DD, MIC) 2. Interpretive criteria are based on those from M100 S20 3. QC strains are the same as in M100 S20 Note: Interpretive breakpoints for cefazolin, carbapenems for the Enterobacteriaceae were change AFTER publication of M45 S2. These will likely be harmonized with next M45 edition (2015).
TESTING GUIDANCE FOR AEROMONAS SPP. Note: Should test P. aeruginosa ATCC 27853 for carbapenems to achieve on-scale endpoints (M100)
FURTHER GUIDANCE FOR AEROMONAS Aeromonas spp. are uniformly resistant to ampicillin; however, susceptibility to amoxicillin-clavulanic acid and cefazolin differs among species. Aeromonas strains may possess multiple, distinct inducible beta-lactamases, and like other genera with inducible beta-lactamases, resistance may emerge during therapy. i.e. consider more frequent re-testing of isolates if repeatedly recovered for patient on treatment (like Enterobacter spp.)
AEROMONAS HYDROPHILA FROM CASE 2 Ampicillin-sulbactam >32 R Cefepime 0.5 S Ciprofloxacin 4 R Trimethoprim sulfamethoxazole 1 S Patient treated with cefepime for 3 weeks Two additional surgeries performed for tissue debridement Discharged after 2 months in hospital Doing well! Note: Leeches were obtained from pharmacy, and from all ciprofloxacin resistant A. hydrophila were isolated change to hospital policy on prophylaxis.
CASE 3 28 YO male Diagnosis: HIV (on antiretroviral therapy, viral load = 590,000 copies; CD4 =585) Guillain Barre syndrome (lower extremity weakness, sensory abnormalities, rapid loss of reflexes) Blood cultures: 1 / 4 bottles grow a curved Gram negative rod Team discharges patient, with note likely contaminant
CASE 3 CONTINUED Microbiology laboratory calls ID team when it is realized patient has been discharged ID contacts Neurology service and has the patient re -admitted Repeat blood cultures also grow Campylobacter Patient treated with IV meropenem, which is transitioned to ciprofloxacin upon receipt of AST results % S among Campylobacter blood stream isolates Cipro Amox-Clav Cefotax SXT Imipenem 30% 92% 79% 75% 100% Fernandez-Cruz 2010 Medicine. 89:319
CAMPYLOBACTER IN BLOOD NEVER a contaminant Uncommon cause of BSI (0.24%) present with history of abdominal pain (35%); diarrhea (34%) Untreated, in HIV patients, is associated with mortality in ~50% of cases Even treated, in HIV+ patients is associated with high mortality (33% vs 9.8%, p=0.04) Patient s isolate S to ciprofloxacin de-escalate therapy & discharged
AST TESTING OF CAMPYLOBACTER You don t need to test isolates at both temperatures some do not grow well @ 37 C
CASE 4 5 year old girl Diagnosis: Acute Otitis Media Ear swab submitted for culture: Many M. catarrhalis Do we perform AST?
SANFORD GUIDE Initial empiric therapy: Amoxicillin Clavulanate, oral cephalosporin, SXT Note: up to 90% of patients infected with M. catarrhalis will have spontaneous resolution Might wait to treat / use analgesic if no fever & questionable exam M45: Testing is not recommended routinely. May be useful for management of patients with prolonged / severe infections Most M. catarrhalis are β-lactamase positive: Resistant to amoxicillin, ampicillin, penicillin Susceptible to amoxicillin-clavulanate (commonly prescribed)
UCLA APPROACH Perform β-lactamase testing using nitrocefin test Report β-lactamase positive (to remind physicians of common resistance to amoxicillin, which is also commonly prescribed empirically for otitis media)
WHAT WILL BE NEW WITH M45 A3? New organisms! Aerococcus spp. treated like viridans group streptococci Lactococcus treated like Staphylococcus Micrococcus spp. treated like Staphylococcus Rothia mucilaginosa treated like Staphylococcus HACEK group will be split in two: Aggregatibacter / Eikenella Cardiobacterium and Kingella spp.
CHALLENGES WITH TESTING HACEK Recommended media: CAMHB with LHB Some isolates require 48 h incubation Some isolates just won t grow in this media! Recent study of 174 HACEK isolates 59.5% failed to grow Aggregatibacter spp: 60 83% didn t grow Eikenella is also problematic Studies at UCLA suggest Brucella broth with hemin and lysed horse blood (5% v/v) might work better for these Further studies underway to confirm this
AEROCOCCUS SPP. 5 species of clinically relevant Aerococcus isolated from humans: Aerococcus urinae Aerococcus viridans Aerococcus sanguinicola Aerococcus urinaehominis very little data, not included in M45 Aerococcus christensenii A. urinae most common isolated from the urine of elderly women Clinical significance here is uncertain when isolated from urine (controversial!) Numerous reports of invasive infections caused by A. urinae and other species
KEY THINGS TO KNOW ABOUT AEROCOCCI A. urinae and Trimethoprim-sulfamethoxazole: When tested in LHB, will test with low MICs When tested on sheep blood, have high MICs (literature) Thymidine? Low in human urine, serum ( but depends on diet) High in sheep blood Low in horse blood Report as resistant to SXT Some suggest inherent resistance to sulfonamides like the enterococci A. urinae genome encodes a high -affinity folate transport binding protein FolT (but not other aerococci) A. sanguinocola and A. viridans and FQ Resistance more common vs. A.urinae Related to mutation to gyra or parc More information: Humphries and Hindler 2014 JCM 52:2177 100% 80% 60% 40% 20% 0% Levofloxacin Susceptibility A. sanguinocola A. urinae A. viridans 2 4 8