Tsigereda Tekle

The Use of Cefepime for Treating AmpC β-lactamase Producing Enterobacteriaceae

BACKGROUND  AmpC β-lactamase-producing organisms are associated with significant morbidity and mortality. Induction of resistance to third-generation cephalosporins after exposure to these agents complicates treatment options and carbapenems are considered optimal therapy. The role of cefepime, however, remains unclear. Our objective was to compare clinical outcomes for patients receiving cefepime compared with meropenem for invasive infections caused by organisms expressing AmpC β-lactamases. METHODS  Hospitalized patients with blood, bronchoalveolar lavage, or intra-abdominal fluid cultures growing Enterobacter spp, Serratia spp, or Citrobacter spp were evaluated using the cefotetan-boronic acid disk test and the cefotetan-cloxacillin Etest to identify organisms with AmpC β-lactamase production from February 2010 to January 2011. In patients with organisms hyperproducing AmpC β-lactamases (positive by both methods), clinical outcomes for patients receiving cefepime or meropenem therapy were compared. To minimize the possibility of treatment selection bias, 1:1 nearest neighbor propensity score matching was performed prior to regression analysis. RESULTS  Of 399 patients meeting eligibility criteria, 96 (24%) had confirmed infections with AmpC β-lactamase-producing organisms. Propensity score matching of patients infected with AmpC β-lactamase-positive organisms treated with cefepime or meropenem yielded 32 well-balanced patient pairs with no difference in 30-day mortality (odds ratio, 0.63; 95% confidence interval [CI], .23-2.11; P = .36) or length of hospital stay after infection (relative risk, 0.96; 95% CI, .79-1.26; P = .56) between the 2 groups. CONCLUSIONS  Cefepime may be a reasonable option for the treatment of invasive infections due to AmpC β-lactamase-producing organisms, particularly when adequate source control is achieved.

First NDM-Positive Salmonella sp. Strain Identified in the United States

Antimicrobial resistance among Enterobacteriaceae is growing, largely due to β-lactamase production.…

Comparing the Outcomes of Patients With Carbapenemase-Producing and Non-Carbapenemase-Producing Carbapenem-Resistant Enterobacteriaceae Bacteremia

Background. Carbapenem-resistant Enterobacteriaceae (CRE) are associated with considerable mortality. As mechanisms of carbapenem resistance are heterogeneous, it is unclear if mortality differs based on resistance mechanisms. We sought to determine whether CRE resistance mechanism determination is prognostically informative. Methods. We conducted an observational study comparing 14-day mortality between patients with carbapenemase-producing (CP)-CRE compared with non-CP-CRE bacteremia. Clinical data were collected on all patients. A comprehensive DNA microarray-based assay was performed on all isolates to identify &bgr;-lactamase-encoding genes. Results. There were 83 unique episodes of monomicrobial CRE bacteremia during the study period: 37 (45%) CP-CRE and 46 (55%) non-CP-CRE. The majority of CP-CRE isolates were bla KPC (92%), followed by bla NDM (5%) and bla OXA-48-type (3%). CP-CRE isolates were more likely to have meropenem minimum inhibitory concentrations (MICs) ≥16 µg/mL, while non-CP-CRE isolates were more likely to have meropenem MICs ⩽1 µg/mL (P value < .001). A total of 18 (22%) patients died within 14 days, including 12 (32%) in the CP-CRE group and 6 (13%) in the non-CP-CRE group. Adjusting for severity of illness on day 1 of bacteremia, underlying medical conditions, and differences in antibiotic treatment administered, the odds of dying within 14 days were more than 4 times greater for CP-CRE compared with non-CP-CRE bacteremic patients (adjusted odds ratio, 4.92; 95% confidence interval, 1.01–24.81). Conclusion. Our findings suggest that CP-CRE may be more virulent than non-CP-CRE and are associated with poorer outcomes. This underscores the added importance of delineating underlying resistance mechanisms of CRE to direct antibiotic treatment decisions.

High Prevalence of Reduced Chlorhexidine Susceptibility in Organisms Causing Central Line- Associated Bloodstream Infections

In units that bathe patients daily with chlorhexidine gluconate (CHG), organisms causing central line-associated bloodstream infections (CLABSIs) were more likely to have reduced CHG susceptibility than organisms causing CLABSIs in units that do not bathe patients daily with CHG (86% vs 64%; P = .028). Surveillance is needed to detect reduced CHG susceptibility with widespread CHG use.

Livestock-Associated, Antibiotic-Resistant Staphylococcus aureus Nasal Carriage and Recent Skin and Soft Tissue Infection among Industrial Hog Operation Workers.

Swine production work is a risk factor for nasal carriage of livestock-associated (LA-) Staphylococcus aureus and also for skin and soft tissue infection (SSTI). However, whether LA-S. aureus nasal carriage is associated with increased risk of SSTI remains unclear. We aimed to examine S. aureus nasal carriage and recent (≤3 months prior to enrollment) SSTI symptoms among industrial hog operation (IHO) workers and their household contacts. IHO workers and their household contacts provided a nasal swab and responded to a questionnaire assessing self-reported personal and occupational exposures and recent SSTI symptoms. Nasal swabs were analyzed for S. aureus, including methicillin-resistant S. aureus (MRSA), multidrug-resistant-S. aureus (MDRSA), absence of scn (livestock association), and spa type. S. aureus with at least one indicator of LA was observed among 19% of 103 IHO workers and 6% of 80 household members. Prevalence of recent SSTI was 6% among IHO workers and 11% among 54 minor household members (0/26 adult household members reported SSTI). Among IHO workers, nasal carriers of MDRSA and scn-negative S. aureus were 8.8 (95% CI: 1.8, 43.9) and 5.1 (95% CI: 1.2, 22.2) times as likely to report recent SSTI as non-carriers, respectively. In one household, both an IHO worker and child reported recent SSTI and carried the same S. aureus spa type (t4976) intranasally. Prevalence of scn-negative S. aureus (PR: 5.0, 95% CI: 1.2, 21.4) was elevated among IHO workers who reported never versus always wearing a face mask at work. Although few SSTI were reported, this study of IHO workers and their household contacts is the first to characterize a relation between nasal carriage of antibiotic-resistant LA-S. aureus and SSTI. The direction and temporality of this relation and IHO workers’ use of face masks to prevent nasal carriage of these bacteria warrant further investigation.

Outcomes of children with enterobacteriaceae bacteremia with reduced susceptibility to ceftriaxone: do the revised breakpoints translate to improved patient outcomes?

Background: In 2010, the Clinical and Laboratory Standards Institute (CLSI) revised and lowered the ceftriaxone minimum inhibitory concentration breakpoints for Enterobacteriaceae and removed the requisite extended spectrum &bgr;-lactamase phenotypic testing for organisms with elevated minimum inhibitory concentrations. The impact that these recommendations have on clinical outcomes of children have not been previously evaluated. Methods: We conducted a retrospective study to compare clinical outcomes between children treated with ceftriaxone and those treated with broader spectrum &bgr;-lactams for Enterobacteriaceae bacteremia with reduced susceptibility (minimum inhibitory concentrations 4–8 µg/mL) to ceftriaxone according to the new CLSI interpretive criteria. Mortality and microbiological relapse were evaluated using a multivariable logistic regression model. Results: There were a total of 783 unique children with Enterobacteriaceae bacteremia during the study period. Using the CLSI breakpoints before 2010, 76 children would have had clinical isolates resistant to ceftriaxone. With the revised breakpoints, 229 Enterobacteriaceae isolates would no longer be susceptible to ceftriaxone (>300% increase). Of the 136 children who met eligibility criteria, 63 children received ceftriaxone and 73 children received broader spectrum &bgr;-lactams. There was no difference in 30-day mortality (odds ratio 0.81, 95% confidence interval: 0.31–2.59) or microbiological relapse (odds ratio 0.97, 95% confidence interval: 0.36–2.66) between the groups. Conclusions: Our findings do not support the proposed clinical benefit of more conservative CLSI breakpoints. The revised breakpoints promote increased broad-spectrum &bgr;-lactam use. The need for lowered ceftriaxone breakpoints against Enterobacteriaceae in children needs to be reevaluated in larger prospective studies.

Low Prevalence of Mupirocin Resistance Among Hospital-Acquired Methicillin-Resistant Staphylococcus aureus Isolates in a Neonatal Intensive Care Unit with an Active Surveillance Cultures and Decolonization Program

How to cite this article: Nuntra Suwantarat, Karen C. Carroll, Tsigereda Tekle, Tracy Ross, Victor O. Popoola and Aaron M. Milstone (2015). Low Prevalence of Mupirocin Resistance Among Hospital-Acquired Methicillin-Resistant Staphylococcus aureus Isolates in a Neonatal Intensive Care Unit with an Active Surveillance Cultures and Decolonization Program. Infection Control & Hospital Epidemiology, 36, pp 232-234 doi:10.1017/ice.2014.17

Comparison of Commercial Antimicrobial Susceptibility Test Methods for Testing of Staphylococcus aureus and Enterococci against Vancomycin, Daptomycin, and Linezolid

ABSTRACT Three commercial antimicrobial susceptibility testing (AST) methods were compared to broth microdilution for testing of Staphylococcus aureus and enterococci against vancomycin, daptomycin, and linezolid. Despite high levels of categorical agreement and essential agreement, vancomycin MICs determined by MicroScan were often 1 log2 concentration higher and MICs determined by Phoenix 1 log2 concentration lower. Daptomycin MICs were 1 to 2 log2 concentrations higher by all AST methods, except Etest, potentially impacting definitive antimicrobial therapy for bloodstream infections due to these organisms.

Recognition of Streptococcus pseudoporcinus Colonization in Women as a Consequence of Using Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry for Group B Streptococcus Identification

ABSTRACT During a 14-month period of using matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) for group B streptococcus (GBS) identification, we recovered 32 (1%) Streptococcus pseudoporcinus isolates from 3,276 GBS screening cultures from female genital sources (25 isolates from pregnant women and 7 from nonpregnant women). An additional two S. pseudoporcinus isolates were identified from a urine culture and a posthysterectomy wound culture. These isolates were found to cross-react with three different GBS antigen agglutination kits, PathoDx (Remel) (93%), Prolex (Pro-Lab Diagnostics) (38%), and Streptex (Remel) (53%). New approaches to bacterial identification in routine clinical microbiology laboratories may affect the prevalence of S. pseudoporcinus.

Lack of antimicrobial activity by the antiretroviral drug nevirapine against common bacterial pathogens

The extended prophylactic use of the antiretroviral drug nevirapine in breastfeeding infants of human immunodeficiency virus (HIV)-infected mothers in developing countries has been shown to reduce HIV transmission ([2][1], [5][2]). Nevirapines use in this setting was also associated with a