334
a NICU in France30 as well as 18 isolates in a study at Seattle Children’s Hospital.31 We sought to determine the frequency of carriage of smr and qacA/B among bloodstream isolates of CoNS and enterococci compared to that of S. aureus at TCH. In addition, we examined the relationship between the presence/ absence of these genes and clinical factors in affected patients.
Methods Microbiology and molecular biology
Blood culture isolates of S. aureus,CoNS,and Enterococcus spp obtained in the routine course of care from October 1, 2016, to October 1, 2017, were procured fromtheTCHclinicalmicrobiology laboratory. TCH is a freestanding children’s hospital and tertiary- care referral center in Houston, Texas, with 592 licensed inpatient beds and >20,000 admissions annually. All bloodstream isolates identified by the clinical microbiology laboratory are subcultured, frozen at −80°C, and banked for at least 1 calendar year. Isolates for this study were subcultured and transferred to the Edward O Mason, Jr., Infectious Diseases Research Laboratory (IDRL) where they were assigned a strain number and additional analyses were performed. A portion of all isolates immediately underwent whole-DNA extraction using QIAcube (Qiagen, Valencia, CA). For this study, only 1 bacterial isolate per episode of bacteremia was included; no colonization isolates were used in this study. CoNS and enterococci were identified to the species level in the clinical microbiology laboratory using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI- TOF MS, Vitek MS, bioMerieux USA, Durham, NC). Only blood cultures obtained from patients <19 years old were included in this study. All isolates were subjected to polymerase chain reaction
(PCR) assay for the qacA/B and smr genes using previously pub- lished primers.20 A subset of PCR products from CoNS and Enterococcus isolates performed during the first PCR run under- went sequencing, were subjected to basic local alignment search tool (BLAST) algorithms, and were compared against published gene sequences (Genebank JF817385 and JF817387) to confirm the identities of the PCR products. Laboratory personnel perform- ing these studies were blinded to clinical data. Antimicrobial susceptibility was performed by theTCHclinical
microbiology laboratory in the routine course of care using Vitek-2 (bioMerieux USA). In total, 60 CoNS isolates were selected for CHGMIC determinations in the IDRL using the macrobroth dilu- tion method.20 Every sixth sequential isolate was chosen, and this process was repeated until a total of 60 isolates were selected for MIC determinations. Corresponding medical records were reviewed for all patients
with attention to underlying conditions, preceding CHG use,21 recent surgery or hospitalization, site of acquisition of infection, and infectious diagnosis. Investigators reviewing medical records and abstracting clinical data were blinded to the results of the molecular analyses, which were performed in tandem with medical record review. The Institutional Review Board of Baylor College of Medicine approved this study.
Infection control practices
Products containingCHGare utilized in a number of infection con- trol practices at our institution.20 At TCH, CHG is included in cen- tral venous line (CVL) insertion and maintenance bundles. Daily CHG baths are employed at TCH for all hospitalized patients
Lauren M. Sommer et al
with a CVL. All patients undergoing elective surgery at TCH are encouraged to take a CHG bath the night prior to operation, and this agent is the skin cleanser of choice in our operating rooms immediately prior to incision. Additionally, daily CHG mouth- washes are routinely prescribed at TCH for hematopoietic stem cell transplant (HSCT) recipients and those with acute myeloid leukemia (AML). Notable exceptions to these rules include patients cared for in the NICU in which procedural CHG is only used in infants who are (1) at least 28 weeks old (corrected gestational age), (2) at least 7 days old, and (3) weigh at least 1,000 g. Iodophor preparations are used for procedural disinfection in infants not meeting these criteria. CHG baths are only used in infants ≥48 weeks old (corrected gestational age). Quaternary ammoniumcom- pound antiseptics are used for the cleaning of rooms and inanimate surfaces at TCH.
Definitions
Sites of acquisition of infection were considered as follows: commu- nity-acquired, community-onset healthcare-associated (CO-HCA), and nosocomial. Community-acquired infections were those occur- ring in otherwise healthy children with onset of signs and symptoms of infection in the community. CO-HCA infections were considered those inwhich signs and symptoms of infection developed in the out- patient setting in children with underlying medical conditions,21,33 excluding well-controlled asthma, eczema and allergic rhinitis. This definition was used to capture patients with underlying conditions that place them at higher risk for infection who may not develop infection in the hospital per se. Previous studies in S. aureus con- ducted by our group and others have shown thatCO-HCAinfections are distinct from community-acquired and hospital-acquired infec- tions in terms of molecular features and antimicrobial susceptibil- ity.33,34 Nosocomial infections were those in which the patient developed signs/symptoms of infection ≥ 72 hours after hospital admission.35 Patients were considered to have had CHG exposure in the
prior 3 months if they had documented use of any CHG prepara- tion, surgery orCVLplacement atTCH(with the exception of neo- nates not meeting criteria as specified above) in the preceding 3 months, or diagnosis of AML or HSCT.21 Patients who underwent surgery but did not have other indications for CHG use were con- sidered to have one-timeCHGuse; others were considered to have had recurrent CHG use. CLABSI was defined in accordance with national guidelines,36 and endocarditis was defined using the modified Duke criteria. For purposes of this study, CoNS isolates were regarded as true infections if isolated in >1 blood culture or if considered as a true infection by the treating physician. Length of stay was defined as time in calendar days from date of positive blood culture to hospital discharge. Recurrent infection was con- sidered culture proven recurrence of infection due to an organism of the same species within 30 days of completing treatment.
Statistical analysis
With regard to CoNS infections, only true infections were included in our analyses. Categorical variables were compared using the Fisher exact test and continuous variables were com- pared using the Wilcoxon rank-sum or Kruskal-Wallis test as appropriate. Two-tailed P values <.05 considered statistically significant. Clinical variables associated with the presence of antiseptic tolerance genes at the P < .10 level were included in amultivariable logistic regression analysis. All statistical analyses
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132
