Joshua T. Freeman

Escherichia coli Bloodstream Infection After Transrectal Ultrasound–Guided Prostate Biopsy: Implications of Fluoroquinolone-Resistant Sequence Type 131 as a Major Causative Pathogen

BACKGROUND Transrectal ultrasound-guided (TRUS) prostate biopsy is a commonly performed procedure, and fluoroquinolones are the most frequently given prophylactic antimicrobials. In the context of increasing fluoroquinolone resistance, and the international emergence of fluoroquinolone-resistant sequence type 131 (ST131) Escherichia coli, we describe a large series of E. coli bacteremia after TRUS biopsy. METHODS All male patients admitted with community-onset (CO) E. coli bacteremia from January 2006 through December 2010 were included. Patient characteristics, treatment outcomes, and rates of antimicrobial resistance were compared between patients with TRUS biopsy-related bacteremia and other male patients with CO E. coli bacteremia. Molecular typing was performed on E. coli isolates to determine phylogenetic group. RESULTS A total of 258 male patients were admitted with CO E. coli bacteremia. Of these, 47 patients (18%) were admitted after TRUS biopsy. Patients who had undergone TRUS biopsy were twice as likely to require intensive care admission (25% vs 12%) and had significantly higher rates of resistance to gentamicin (43%), trimethoprim-sulphamethoxazole (60%), and ciprofloxacin (62%) as well as all 3 agents in combination (19%). Thirty-six percent of post-TRUS biopsy patients did not receive active empirical antibiotic therapy. The ST131 clone accounted for 41% of all E. coli isolates after TRUS biopsy. CONCLUSIONS E. coli bacteremia can be a life-threatening complication of TRUS biopsy. Infecting strains are frequently multidrug-resistant and resistant to common empirical antibiotic agents. E. coli ST131 is an important cause of sepsis after TRUS biopsy. Further studies should evaluate colonization with fluoroquinolone-resistant E. coli as a risk factor for postbiopsy sepsis.

Infectious Complications Following Transrectal Ultrasound–Guided Prostate Biopsy: New Challenges in the Era of Multidrug-Resistant Escherichia coli

Transrectal ultrasound (TRUS)-guided prostate biopsy is currently considered the standard technique for obtaining tissue to make a histological diagnosis of prostatic carcinoma. Infectious complications following TRUS-guided prostate biopsy are well described, and are reportedly increasing in incidence. The role of antibiotic prophylaxis in reducing post-TRUS biopsy infections is now established, and many guidelines suggest that fluoroquinolone antimicrobials are the prophylactic agents of choice. Of note, however, recent reports suggest an emerging association between TRUS biopsy and subsequent infection with fluoroquinolone-resistant Escherichia coli. Against this background, we provide an overview of the epidemiology, prevention, and treatment of infectious complications following TRUS biopsy, in the wider context of increasing global antimicrobial resistance.

Identification and molecular characterisation of New Delhi metallo-β-lactamase-1 (NDM-1)- and NDM-6-producing Enterobacteriaceae from New Zealand hospitals

The global spread of New Delhi metallo-β-lactamase (NDM) is of significant public health concern. This study sought to determine whether bla(NDM) was present in Enterobacteriaceae isolates displaying resistance to carbapenems that were submitted to the National Antibiotic Reference Laboratory, Institute of Environmental Science and Research (Porirua, New Zealand) during 2009 and 2010. Isolates were tested for the presence of β-lactamase genes and 16S rRNA methylase genes by polymerase chain reaction (PCR) and sequencing. Plasmid transfer studies were undertaken on isolates found to be harbouring bla(NDM). Molecular typing was performed by multilocus sequence typing (MLST). The bla(NDM-1) gene was identified in four Enterobacteriaceae isolates (two Escherichia coli, one Klebsiella pneumoniae and one Proteus mirabilis) from four patients in New Zealand hospitals in 2009 and 2010. In addition, the bla(NDM-6) gene, which differed from bla(NDM-1) by a point mutation at position 698 (C→T), was also identified in an E. coli isolate from the same patient who harboured the bla(NDM-1)-positive P. mirabilis. All four patients had recently been hospitalised or received health care in India. Four of the isolates also produced a CTX-M-15 extended-spectrum β-lactamase and/or plasmid-mediated AmpC β-lactamase, and all five isolates harboured the plasmid-mediated 16S rRNA methylase rmtC gene. The E. coli types were diverse by MLST, and the K. pneumoniae isolate belonged to the internationally disseminated sequence type 11 (ST11) clone. These findings further illustrate the diversity of phenotypic and genotypic features found in association with bla(NDM), in addition to documenting the international spread of this resistance mechanism, notably into a country with historically low rates of antimicrobial resistance.

Clinical failures associated with rpoB mutations in phenotypically occult multidrug-resistant Mycobacterium tuberculosis.

SETTING Recently, Mycobacterium tuberculosis isolates have been described that test phenotypically susceptible to rifampicin (RMP) yet harbour genotypic rpoB mutations. OBJECTIVE 1) To investigate the impact of such mutations on clinical outcomes among RMP-susceptible isolates, and 2) to determine the prevalence of rpoB mutations among isoniazid (INH) monoresistant isolates at our laboratory and to describe the association between the presence of these mutations and clinical outcomes. METHODS M. tuberculosis isolates were screened for mutations in the rpoB gene using the Cepheid Gene-Xpert® MTB/RIF assay. Clinical correlation was made by reviewing patient case notes. RESULTS Isolates from 94 patients were found to have INH-resistant, RMP-susceptible profiles. Clinical information was available for 52 patients, including three whose isolates had rpoB mutations. All three of these patients had treatment failures, compared to two of 49 patients whose isolates did not have rpoB mutations (P = 0.0005). DISCUSSION We demonstrate a significant association between the presence of rpoB gene mutations that are not detected at the current RMP critical concentration and treatment failure. We suggest that a review of the current RMP critical concentration is warranted to ensure that RMP is not used inappropriately for the treatment of phenotypically occult multidrug-resistant tuberculosis.

Community-Onset Genitourinary Tract Infection due to CTX-M-15–Producing Escherichia coli among Travelers to the Indian Subcontinent in New Zealand

A series of patients are described who presented to a New Zealand hospital with genitourinary tract infection due to CTX-M-15-producing Escherichia coli. All had a history of travel to the Indian subcontinent and lacked traditional risk factors for urinary tract infection due to a multidrug-resistant organism.

An evaluation of the Xpert MTB/RIF assay and detection of false-positive rifampicin resistance in Mycobacterium tuberculosis.

Recent reports suggest that false-positive rifampicin resistance may be assigned by the Xpert MTB/RIF assay. We analysed 169 specimens using the MTB/RIF assay. Using culture as the gold standard, we found that the assay had 100% sensitivity and specificity for detecting M. tuberculosis. However, we found that the assay incorrectly assigned rifampicin resistance in 4/13 (31%) of cases.

Seasonal peaks in Escherichia coli infections: possible explanations and implications

Escherichia coli is a common cause of infections in all populations and countries of the world, causing an enormous burden of disease. In this issue of Clinical Microbiology and Infection, Al-Hasan et al. describe seasonal peaks in the incidence of E. coli bloodstream infection (BSI) during the summer for a population of 125 000 in Minnesota, USA. We discuss the probability that similar seasonal peaks in the incidence of E. coli BSI occur in other populations and geographical regions. Second, we discuss possible underlying explanations for these findings in terms of seasonal changes in human behaviour and the effect of temperature on the ability of E. coli to survive in the environment. Finally, we discuss some of the possible implications of E. coli BSI being a seasonal illness. More specifically, we discuss how better understanding the reasons for seasonality may potentially help us to better understand the dominant routes by which human populations are exposed to clonal groups of E. coli associated with urinary tract infection.

Widespread dissemination of CTX-M-15 genotype extended-spectrum-β-lactamase-producing enterobacteriaceae among patients presenting to community hospitals in the southeastern United States.

ABSTRACT Extended-spectrum-β-lactamase (ESBL)-producing organisms are increasingly prevalent. We determined the characteristics of 66 consecutive ESBL-producing isolates from six community hospitals in North Carolina and Virginia from 2010 to 2012. Fifty-three (80%) ESBL-producing isolates contained CTX-M enzymes; CTX-M-15 was found in 68% of Escherichia coli and 73% of Klebsiella isolates. Sequence type 131 (ST131) was the commonest type of E. coli, accounting for 48% of CTX-M-15-producing and 66% of CTX-M-14-producing isolates. In conclusion, the CTX-M genotype and ST131 E. coli were common among ESBL isolates from U.S. community hospitals.

Central Line–Associated Bloodstream Infections in Adult Hematology Patients with Febrile Neutropenia: An Evaluation of Surveillance Definitions Using Differential Time to Blood Culture Positivity

We used differential time to positivity between central and peripheral blood cultures to evaluate the positive predictive value (PPV) of the National Healthcare Safety Network central line-associated bloodstream infection (CLABSI) surveillance definition among hematology patients with febrile neutropenia. The PPV was 27.7%, which suggests that, when the definition is applied to this population, CLABSI rates will be substantially overestimated.

Bloodstream infection with extended-spectrum beta-lactamase-producing Enterobacteriaceae at a tertiary care hospital in New Zealand: risk factors and outcomes

OBJECTIVES To define local risk factors and outcomes for bacteremia with extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) at a tertiary hospital in New Zealand. METHODS Patients with ESBL-E bacteremia were compared to matched control patients with non-ESBL-producing Enterobacteriaceae bacteremia. Patients were matched by onset of bacteremia (community vs. hospital), site of blood culture collection (peripheral vs. via central line), and infecting organism species. RESULTS Forty-four cases with matched controls were included. Eight- and 30-day mortality was higher in cases than controls (27% vs. 7%; p=0.011 and 34% vs. 11%, p=0.011). Twenty-one cases (48%) were community-onset. Community-onset cases were associated with urinary tract infection, whereas hospital-onset cases were associated with central line infection, intensive care admission, and Enterobacter cloacae. Independent risk factors for ESBL-E bacteremia were fluoroquinolone exposure (odds ratio (OR) 6.56, 95% confidence interval (CI) 1.79-24), first-generation cephalosporin exposure (OR 12.3, 95% CI 1.01-148), and previously-known colonization with ESBL-E (OR 46.2, 95% CI 3.45-619). CONCLUSIONS The association with fluoroquinolone exposure suggests that measures to reduce unnecessary use may be an effective preventative strategy. Known colonization with ESBL-E is a strong risk factor for ESBL-E bacteremia, and colonization status should be taken into consideration when choosing empirical therapy.