VOLUME XXIII NUMBER 1 July 2008 CONTAGIOUS COMMENTS Department of Epidemiology Bugs and Drugs Elaine Dowell, SM (ASCP), Marti Roe SM (ASCP), Ann-Christine Nyquist MD, MSPH Are the bugs winning? The 2007 TCH annual antibiogram again shows an increase in resistant organisms that are not easily detected by standard testing methodologies. This requires clinical laboratories to develop new testing methods and staff expertise to recognize them. Although we have added MRSA to our daily vocabulary, both gram negative and gram positive organisms have shown increasing rates of new mechanisms of resistance. MRSA continues to increase in both our emergency departments (including Network of Care, Urgent Care and the Child Health Clinic) and our inpatient population. Because of the implications of the spread of this resistant organism, TCH s Microbiology laboratory is validating a new PCR assay on our GeneXpert that will allow faster screening of high risk patients. This faster screening will allow isolation precautions to be shortened for MRSA negative patients. The D test has been used for several years to detect the erm gene that confers inducible clindamycin resistance to Staphylococcus aureus. The D test is performed prior to reporting clindamycin susceptibility for S. aureus. The erm gene is also found in Group A streptococcus and is automatically tested in our lab prior to reporting susceptibilities. In 2007, 22 Group A strep isolates were tested with none showing the inducible erm gene that would indicate clindamycin resistance. Our number of VRE (Vancomycin Resistant Enterococcus) isolates, although low, has increased from one in 2006 to five in 2007. VRE has been isolated from significant sources and we reported our first blood culture isolate this year. Gram negative bacteria also continue to mutate and acquire new resistance enzymes that are not easily detected by standard susceptibility testing. Perhaps the most challenging for the laboratory has been Extended-Spectrum Beta Lactamases (ESBLs). Typically, ESBLs are mutant, plasmid-mediated beta-lactamases derived from older broad spectrum beta-lactamases which have extended substrate profiles that permit hydrolysis of all cephalosporins, penicillins, and aztreonam. The production of AmpC beta-lactamases by gram negative bacteria further complicates susceptibility testing. AmpC beta lactamases differ from ESBLs in that they are cephalosporinases and confer resistance to beta lactamase inhibitors. AmpC is normally produced in low levels by many gram negative organisms and is not associated with resistance. When AmpC is produced at high levels there is resistance to all beta-lactams except carbapenems and 4 th generation cephalosporins (e.g. Cefipime). ESBL (Extended-Spectrum Beta Lactamase) isolates this year have showed a significant increase from 3 to 13. The majority of these isolates were from urine specimens, but one isolate was from a blood culture. In Table 1, Enterobacter cloacae urine isolates showed a marked decrease in susceptibility and differed from the non-urine isolates. This phenomenon of decreased susceptibility of this organism in non-icu units has been reported at other institutions and is making an impact on patient care. (see page 2 for Table 1.)
TABLE 1. Antimicrobial Susceptibilities at The Children s Hospital 2007 Gram Negative Organisms (% susceptible) NUMBER OF ISOLATES Ampicillin / Amoxicillin Cefazolin / cephalexin Cefuroxime Cefotaxime/ ceftriaxone Gentamicin Tobramycin Trimethoprim / sulfa Ciprofloxaci 1 Haemophilus species 32 34 100 75 E. coli (urine) 751 50 95 98 99 97 98 69 96 E. coli (non-urine) 61 57 93 95 98 97 97 72 92 Enterobacter cloacae (urine) (21) R R 14 38 86 86 62 86 Enterobacter cloacae (non-urine) 45 R R 51 51 98 98 91 91 Klebsiella pneumoniae 69 R 87 91 94 98 98 81 98 Klebsiella oxytoca (28) R 44 69 81 81 88 88 100 Proteus mirabilis (24) 80 80 100 100 100 100 80 100 Salmonella species (20) 74 91 91 Serratia marcescens (20) R R 0 100 93 80 93 87 Shigella species (6) 0 100 40 Testing by Microscan panels (except Haemophilus by E-test) 1 Ciprofloxacin is FDA approved for children greater than 1 year of age for complicated UTIs. 13 Isolates identified as ESBL.- includes one stool surveillance culture R = Resistant (Intrinsic) ( ) Small number of isolates MRSA Rates for TCH Patients 60% 50% Rate 40% 30% 20% MRSA Rate ED Rate Non-ED Rate 10% 0% 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year VOLUME XXIII NUMBER 1 July/August 2008 Page 2
TCH s microbiology laboratory will be validating new susceptibility testing panels that will detect ESBLs in CLSI recommended organisms including: E. coli, Klebsiella species, and Proteus mirabilis. Having the confirmatory assay within the panel will shorten the turnaround time to a final report by a day and will also allow us to screen for ESBLs in Enterobacter cloacae. The bugs continue to put up a good fight as the antibiotic arsenal is decreasing. What can you do? 1. Obtain good specimens to send to the microbiology lab for culture. This translates to fluid samples where a gram stain may be done and avoiding the use of swabs for culture. 2. Check microbiology culture results and susceptibility patterns so that you can make sure you are treating with an appropriate antibiotic. 3. Use a narrow spectrum antibiotic when possible to decrease antibiotic pressure and development of resistance. 4. Prevent infection by practicing tried and true good infection control practices: protect yourself and your patient by adhering to isolation precautions and by all means wash your hands. VOLUME XXIII NUMBER 1 July/August 2008 Page 3
Additional graphs from: ANTIBIOTIC SUSCEPTIBILITY OF BACTERIA & YEAST Elaine Dowell, SM (ASCP) Technical Supervisor of Microbiology Marti Roe, SM (ASCP) Technical Consultant for Microbiology James K. Todd, MD Clinical Director of Microbiology Ann-Christine Nyquist, MD, MSPH January 1, 2007 December 31, 2007 TABLE 2. Antimicrobial Susceptibilities at The Children s Hospital 2007 Non-Enterobacteriaceae (% susceptible) NUMBER OF ISOLATES Ticarcillin/clav Timentin Piperacillin Ceftazidime Aztreonam Imipenem / Cilastatin Ciprofloxacin 3 Gentamicin Tobramycin Meropenem Piperacillin / Taz Minocycline Trimeth / Sulfa *Acinetobacter species 1 (22) 77 86 82 91 Pseudomonas aeruginosa Non CF 2 117 91 97 96 80 97 87 87 97 97 99 CF-mucoid 1 55 65 69 76 58 38 65 78 CF-nonmucoid 1 56 46 63 61 59 49 46 64 *A. xylosoxidans 1 (29) 76 76 17 69 Stenotrophomonas maltophilia 1 30 13 16 100 87 1 2 3 Cystic fibrosis isolates by E-test. May include >1 isolate/patient. Testing by Microscan Ciprofloxacin is FDA approved for children greater than 1 year of age for complicated UTIs. * 2006 and 2007 data combined ( ) Small number of isolates TABLE 3. Antimicrobial Susceptibilities at The Children s Hospital 2007 Staphylococcus (% susceptible) NUMBER OF ISOLATES TESTED Penicillin Oxa-/ Naf-/ Dicloxacillin Cefazolin Cephalexin Trimethoprim / Sulfa Erythromycin Clindamycin Vancomycin Staph aureus Staph aureus (MSSA) 299 100 100 99 84 86 100 Staph aureus (MRSA) 291 0 0 0 97 10 70 100 Staph epidermidis 133 5 17 17 63 26 100 Testing by Microscan panels Confirmation of MRSA by PBP2 testing and Chromagar VOLUME XXIII NUMBER 1 July/August 2008 Page 4
TABLE 4. Antimicrobial Susceptibilities at The Children s Hospital 2007 Streptococcus (% susceptible) Penicillin Cefotaxime NUMBER OF ISOLATES S < 0.06 I = 0.12-1 R > 2 S < 0.5 I = 1 R > 2 Erythromycin Clindamycin Trimethoprim/ Sulfa Cefotaxime Ampicillin/ Amoxicillin Vancomycin S. pneumoniae 1 Invasive S. pneumoniae 1 Localized (resp.) (22) 54 32 14 91 4 4 95 95 82 100 50 44 20 36 78 18 4 50 66 46 100 Viridans Strep 1 Invasive Strep. anginosus 1 Group Invasive Enterococcus 2 faecalis Enterococcus 2 faecium 1 Testing by E-test. 2 Testing by Microscan panel. 30 57 23 20 57 90 83 100 (21) 81 19 86 86 100 100 66 100 100 45* 51 82 Gentamicin Synergy Screen E. faecalis = 76% Susceptible Gentamicin Synergy Screen E. faecium = 91% Susceptible * 5 VRE patients * 2006-2007 data combined Table 5. Antimicrobial Susceptibilities at The Children s Hospital 2007 Candida albicans (# of isolates susceptible) Streptococcus (% susceptible) Fluconazole NUMBER OF ISOLATES S < 8 I = 16-32 R > 64 Candida albicans (21) 21 Testing by UTHSC (at San Antonio) 2006-2007 combined VOLUME XXIII NUMBER 1 July/August 2008 Page 5
CONTAGIOUS COMMENTS Department of Epidemiology EDITOR: Kelly DeStefano, Staff Assistant III The Children s Hospital, Dept. of Epidemiology, B-276 th 13123 E. 16 Avenue, Aurora, CO 80045 Phone: 720-777-6072; FAX: 720-777-7293 DeStefano.Kelly@tchden.org http://www.thechildrenshospital.org **We Recycle!** The Department of Epidemiology at The Children s Hospital We are modifying our distribution process for Bug Watch and Contagious Comments. Below are the methods of distribution that we will be using. Please provide us with your preferred method of distribution. Name: E-mail (please provide your Email address): Fax (please provide us with your fax number and who the fax should be directed to): ( ) Both of these publications are always posted on The Children s Hospital website at: http://www.thechildrenshospital.org/news/publications/index.aspx Please return your preference to: Carolyn Brock, The Children s Hospital, Epidemiology Box B276, 13123 E. 16 th Avenue, Aurora, CO 80045 or E-mail address: brock.carolyn@tchden.org. Thank you for your interest in our publication.