Difficult-to-treat (DTR) Pseudomonas aeruginosa harboring Verona-Integron metallo-β-lactamase (blaVIM): infection management and molecular analysis

Pseudomonas aeruginosa harboring Verona Integron-encoded metallo-β-lactamase enzymes (VIM-CRPA) have been associated with infection outbreaks in several parts of the world. In the US, however, VIM-CRPA remain rare. Starting in December 2018, we identified a cluster of cases in our institution. Herein, we present our epidemiological investigation and strategies to control/manage these challenging infections. This study was conducted in a large academic healthcare system in Miami, FL, between December 2018 and January 2022. Patients were prospectively identified via rapid molecular diagnostics when cultures revealed carbapenem-resistant P. aeruginosa. Alerts were received in real time by the antimicrobial stewardship program and infection prevention teams. Upon alert recognition, a series of interventions were performed as a coordinated effort. A retrospective chart review was conducted to collect patient demographics, antimicrobial therapy, and clinical outcomes. Thirty-nine VIM-CRPA isolates led to infection in 21 patients. The majority were male (76.2%); the median age was 52 years. The majority were mechanically ventilated (n = 15/21; 71.4%); 47.6% (n = 10/21) received renal replacement therapy at the time of index culture. Respiratory (n = 20/39; 51.3%) or bloodstream (n = 13/39; 33.3%) were the most common sources. Most infections (n = 23/37; 62.2%) were treated with an aztreonam-avibactam regimen. Six patients (28.6%) expired within 30 days of index VIM-CRPA infection. Fourteen isolates were selected for whole genome sequencing. Most of them belonged to ST111 (12/14), and they all carried blaVIM-2 chromosomally. This report describes the clinical experience treating serious VIM-CRPA infections with either aztreonam-ceftazidime/avibactam or cefiderocol in combination with other agents. The importance of implementing infection prevention strategies to curb VIM-CRPA outbreaks is also demonstrated.

Comparative Study of Serum Zinc Level in Between Preeclamptic Patients and Normal Pregnancy in Bangladesh

Globally preeclampsia is a major cause of maternal & perinatal morbidity & mortality. Zinc is an important trace element which is essential in pregnancy for fetal growth. Essentiality of zinc during pregnancy is evident. The cross sectional study was performed to estimate the comparison of serum zinc level in between preeclamptic patient and normal pregnancy. This study was conducted from July 2016 to June 2017 in the Department of Biochemistry, Mymensingh Medical College, Mymensingh, Bangladesh. Total 100 pregnant women were included as study population. Out of 100 subjects 50 were preeclamptic patients as case group and another 50 were normal pregnant women as control group. Serum zinc was determined by colorimetric method. The statistical analysis was done by SPSS windows package version 21.0. The mean±SD of case group was 59.30±5.22 and control group was 65.26±5.99mg/dl. Statistical difference was calculated by Student's unpaired 't' test. After analysis it showed that the mean±SD of serum zinc level was highly significantly (p<0.001) decreased in case group that in comparison to control group.

Utilizing Ceftazidime/Avibactam Therapeutic Drug Monitoring in the Treatment of Neurosurgical Meningitis Caused by Difficult-to-Treat Resistant Pseudomonas aeruginosa and KPC-Producing Enterobacterales

Background

Central nervous system (CNS) infections caused by Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacterales and difficult-to-treat resistant (DTR) Pseudomonas aeruginosa represent a formidable clinical challenge. Antimicrobial regimens that efficiently penetrate the cerebrospinal fluid (CSF) and achieve sufficient concentrations associated with microbiologic and clinical cure are limited. We evaluated therapy with ceftazidime-avibactam (CAZ-AVI) in order to guide precise dosing in the treatment of CNS infections.

Methods

Therapeutic drug monitoring (TDM) was performed in 3 patients with health care-associated ventriculitis and meningitis (HAVM) using CAZ-AVI 2.5 g infused intravenously every 8 hours as standard and extended infusion. Simultaneous CSF and plasma samples were obtained throughout the dosing interval in each patient. Concentrations of CAZ and AVI were determined by liquid chromatography/mass spectrometry.

Results

Bacterial identification revealed KPC-producing Klebsiella pneumoniae (KPC-Kp), DTR Pseudomonas aeruginosa, and KPC-producing Enterobacter cloacae (KPC-Ent.c). All isolates were resistant to carbapenems. The minimum inhibitory concentrations (MICs) of CAZ-AVI were 0.25/4, 4/4, and 0.25/4 μg/mL, respectively. CAZ and AVI concentrations were determined in CSF samples ranging from 29.0 to 15.0 µg/mL (CAZ component) and 4.20 to 0.92 µg/mL (AVI component), respectively. AVI achieved concentrations ≥1 µg/mL in 11 out of 12 CSF samples collected throughout the dosing interval. Clinical and microbiologic cure were attained in all patients.

Conclusions

Postinfusion concentrations of CAZ-AVI were measured in plasma and CSF samples obtained from 3 patients with complicated CNS infections caused by antimicrobial-resistant isolates. The measured concentrations revealed that standard CAZ and AVI exposures sufficiently attained values correlating to 50% fT > MIC, which are associated with efficient bacterial killing.

Investigating and Treating a Corneal Ulcer Due to Extensively Drug-Resistant Pseudomonas aeruginosa

Resistant Gram-negative bacteria are a growing concern in the United States, leading to significant morbidity and mortality. We identified a 72-year-old female patient who presented with unilateral vision loss. She was found to have a large corneal ulcer with hypopyon. Culture of corneal scrapings grew extensively drug-resistant Pseudomonas aeruginosa. Treatment involved a combination of systemic and topical antibiotics. Whole genome sequencing revealed the presence of blaVIM-80, blaGES-9, and other resistance determinants. This distinctive organism was linked to an over-the-counter artificial tears product.

Characterization of a Novel Pathogen in Immunocompromised Patients: Elizabethkingia anophelis-Exploring the Scope of Resistance to Contemporary Antimicrobial Agents and β-lactamase Inhibitors

Background

Elizabethkingia anophelis is an emerging Gram-negative nonlactose fermenter in the health care setting, where it causes life-threatening infections in immunocompromised patients. We aimed to characterize the molecular mechanisms of antimicrobial resistance and evaluate the utility of contemporary antibiotics with the intent to offer targeted therapy against an uncommonly encountered pathogen.

Methods

Whole-genome sequencing (WGS) was conducted to accurately identify isolate species and elucidate the determinants of β-lactam resistance. Antimicrobial susceptibility testing was performed using broth microdilution and disk diffusion assays. To assess the functional contribution of the major metallo-β-lactamase (MBL) encoding genes to the resistance profile, bla _BlaB was cloned into pBCSK(-) phagemid vector and transformed into Escherichia coli DH10B.

Results

WGS identified the organism as E. anophelis. MBL genes bla _BlaB-1 and bla _GOB-26 were identified, in addition to bla _CME-2, which encodes for an extended-spectrum β-lactamase (ESBL). Plasmids were not detected. The isolate was nonsusceptible to all commonly available β-lactams, carbapenems, newer β-lactam β-lactamase inhibitor combinations, and to the combination of aztreonam (ATM) with ceftazidime-avibactam (CAZ-AVI). Susceptibility to the novel siderophore cephalosporin cefiderocol was determined. A BlaB-1 transformant E. coli DH10B isolate was obtained and demonstrated increased minimum inhibitory concentrations to cephalosporins, carbapenems, and CAZ-AVI, but not ATM.

Conclusions

Using WGS, we accurately identified and characterized an extensively drug-resistant E. anophelis in an immunocompromised patient. Rapid evaluation of the genetic background can guide accurate susceptibility testing to better inform antimicrobial therapy selection.

142. Evaluation of Meropenem-Vaborbactam Susceptibility and Underlying Resistance Mechanisms among Clinical KPC-producing Klebsiella pneumoniae

Background

Meropenem-vaborbactam (MV) is the first carbapenem/β-lactamase inhibitor combination developed to restore meropenem susceptibility against KPC-producing carbapenem-resistant Enterobacterales(CRE). Vaborbactam (VAB) potently inhibits Ambler class A and C β-lactamases by reversible covalent binding of boronate to serine side chains of β-lactamases. Resistance to MV in non-metallo-β-lactamase (MBL) producing Klebsiella pneumoniae (KP) isolates has been described but remains rare. We sought to identify the major molecular mechanisms associated with MV resistance in KPC-producing KP (KPC-KP) isolates.

Methods

Clinical isolates with elevated MV MICs were identified by the consult service. Additional clinical isolates with mutations in ompK35 or ompK36 genes were selected from a historic database. Isolates with MBL or OXA-48-like genes were excluded. Controls were comprised of MV susceptible KPC-KP isolates. MICs determination was done using Sensititre automated broth microdilution (BMD) according to CLSI. VAB and avibactam concentrations were held at 8 µg/ml and 4 µg/ml, respectively. Whole genome sequencing (WGS) was performed on all isolates. Genome libraries were prepared using Illumina Nextera XT and sequencing was performed on MiSeq and MinION.

Results

A total 119 KPC-KP isolates were included in the study. All isolates were resistant to meropenem. Twenty-one KPC-KP with elevated MV MICs were identified. All MV resistant isolates harbored mutations in ompK36 genes. Glycine/aspartate (GD 134-135) insertion, premature stop codon in ompK36 genes, and concomitantly elevated blaKPC copy number were predominant among MV resistant isolates. No insertion elements in ompK36 gene promoter region were found. Two MV resistant isolates exhibited unique mutations in blaKPC and envZ genes. See table for WGS and MIC results. Table 1.Whole genome sequencing and MICs of MV resistant KPC-KP isolatesα: Truncated at nodes 14 and 76, partial genotype consistent with blaSHV-12WT: Wild type*: Premature stop codonGD: Duplication of Glycine (G134) and Aspartate (D135)FS: Frameshift mutationins: insertionMEM: meropenemMVB: meropenem-vaborbactamCZA: ceftazidime-avibactamCFD: cefiderocolN/A: not availableTable 2.Whole genome sequencing and MICs of MV susceptible KPC-KP isolates

Conclusion

MV resistant KPC-KP isolates were reliably analyzed using WGS to reveal the contribution of omp gene mutations and blaKPC copy number to this phenotype. Elevated MV MICs were additionally recognized among clinical isolates from a historic database preceding MV availability. In the absence of MBL production, caution remains warranted with the use of MV empirically against KPC-KP due to non-β-lactamase mediated resistance mechanisms.

Disclosures

Daniel D. Rhoads, M.D. PhD, Luminex: Advisor/Consultant|Talis Biomedical: Advisor/Consultant|Thermo Fisher: Advisor/Consultant Federico Perez, M.D., Accelerate: Grant/Research Support|Merck: Grant/Research Support|Pfizer: Grant/Research Support Robert A. Bonomo, MD, NIH VA: Grant/Research Support|VenatoRx Merck Wockhardt Cystic Fibrosis Foundation: Grant/Research Support.

Genomic heterogeneity underlies multidrug resistance in Pseudomonas aeruginosa: A population-level analysis beyond susceptibility testing

Background

Pseudomonas aeruginosa is a persistent and difficult-to-treat pathogen in many patients, especially those with Cystic Fibrosis (CF). Herein, we describe a longitudinal analysis of a series of multidrug resistant (MDR) P. aeruginosa isolates recovered in a 17-month period, from a young female CF patient who underwent double lung transplantation. Our goal was to understand the genetic basis of the observed resistance phenotypes, establish the genomic population diversity, and define the nature of sequence evolution over time.

Methods

Twenty-two sequential P. aeruginosa isolates were obtained within a 17-month period, before and after a double-lung transplant. At the end of the study period, antimicrobial susceptibility testing, whole genome sequencing (WGS), phylogenetic analyses and RNAseq were performed in order to understand the genetic basis of the observed resistance phenotypes, establish the genomic population diversity, and define the nature of sequence changes over time.

Results

The majority of isolates were resistant to almost all tested antibiotics. A phylogenetic reconstruction revealed 3 major clades representing a genotypically and phenotypically heterogeneous population. The pattern of mutation accumulation and variation of gene expression suggested that a group of closely related strains was present in the patient prior to transplantation and continued to change throughout the course of treatment. A trend toward accumulation of mutations over time was observed. Different mutations in the DNA mismatch repair gene mutL consistent with a hypermutator phenotype were observed in two clades. RNAseq performed on 12 representative isolates revealed substantial differences in the expression of genes associated with antibiotic resistance and virulence traits.

Conclusions

The overwhelming current practice in the clinical laboratories setting relies on obtaining a pure culture and reporting the antibiogram from a few isolated colonies to inform therapy decisions. Our analyses revealed significant underlying genomic heterogeneity and unpredictable evolutionary patterns that were independent of prior antibiotic treatment, highlighting the need for comprehensive sampling and population-level analysis when gathering microbiological data in the context of CF P. aeruginosa chronic infection. Our findings challenge the applicability of antimicrobial stewardship programs based on single-isolate resistance profiles for the selection of antibiotic regimens in chronic infections such as CF.

66. Utilizing ceftazidime/avibactam therapeutic drug monitoring in the treatment of neurosurgical meningitis caused by Difficult-to-treat resistant (DTR)-Pseudomonas aeruginosa and KPC-producing Enterobacterales

Background

Central nervous system (CNS) infections caused by carbapenem-resistant Enterobacterales (CRE) and Difficult-to-treat resistant (DTR)-Pseudomonas aeruginosa (PA) are a therapeutic challenge. Data demonstrating the pharmacokinetic/pharmacodynamic (PK/PD) properties of newer beta-lactamase inhibitors remains scarce. A clinical challenge lies in selecting an antimicrobial regimen that diffuses across the blood brain barrier and maintains concentrations to achieve PD targets associated with bacterial killing. These complexities compelled us to quantify the pharmacological properties of ceftazidime/avibactam (CZA). Utilizing therapeutic drug monitoring (TDM), we evaluated the adequacy of therapy and aimed to guide precise CNS dosing in the treatment of three patients with neurosurgical meningitis.

Methods

Bacterial identification and susceptibility testing were performed using MicroScan. TDM of CZA was implemented using a dose of 2.5 g infused intravenously over 2-hours, every 8 hours. The concentrations of ceftazidime and avibactam were determined by liquid chromatography/mass spectrometry. For patients 2 and 3, four unique CSF and plasma samples spanning the dosing interval were obtained; including trough values. (See table)

Results

Bacterial identification and CZA MICs for patients 1, 2, and 3 revealed blaKPCKp (0.25μg/mL), DTR PA (4 μg/mL), and blaKPCE. cloacae (0.25 μg/mL), respectively. Measured plasma and CSF concentrations of avibactam (AVI) and ceftazidime (CAZ) are shown in Table 1.

Table 1a. Therapeutic Drug Monitoring of CAZ-AVI depicting dosing, time of samples, and measured concentrations in CSF and Human Plasma (HP)

Conclusion

Measuring CZA concentration levels in CSF was achieved in 3 patients with complicated CNS infections. Post-infusion concentrations indicated that adequate CAZ and AVI exposures were attained in the CSF. Notably, avibactam was shown to achieve concentrations ≥1 µg/ml in the CSF throughout the dosing interval. For avibactam and ceftazidime, the PK/PD target correlated with bacterial killing is ~50% fT &gt;MIC. In 2 out of 3 patients, concentrations were determined to be above the respective MICs throughout the entire dosing interval in the CSF. All patients attained clinical and microbiological cure. A novel CZA TDM method was successfully employed to establish that CZA maintains therapeutic CSF concentrations that exceed the MIC throughout the dosing interval.

Disclosures

Robert A. Bonomo, MD, entasis (Research Grant or Support)Merck (Grant/Research Support)NIH (Grant/Research Support)VA Merit Award (Grant/Research Support)VenatoRx (Grant/Research Support)

576. Determinants of COVID-19 Vaccine Hesitancy: A Cross-Sectional Study in 3 Communities in the United States and Lebanon

Background

The ongoing COVID-19 pandemic has thus far resulted in substantial worldwide mortality. As of November 2020, COVID-19 vaccines became available following Emergency Use Authorization (EUA) issued by the FDA. Recent longitudinal studies published as of March 2021 demonstrated that vaccine hesitancy remains high despite improvements compared to 2020. This study sought to explore the perceptions, beliefs, attitudes, and knowledge surrounding COVID-19 and identify determinants uniquely associated with vaccine hesitancy.

Methods

A cross-sectional electronic survey was created based on CDC & IDSA recommendations. The survey was distributed from March 2021 until June 2021 randomly to faculty members, healthcare workers, and students (≥18 years old) across 3 major academic centers (Case Western Reserve University, Spectrum Health, and the American University of Beirut Medical Center [AUBMC]). Data collected included socio-economic characteristics, demographics, knowledge, and attitudes pertaining to COVID-19 and vaccination. A multivariable regression model was utilized to evaluate for independent associations between variables and vaccination willingness/hesitancy as the primary outcome.

Results

In total, 7,197 participants completed the survey with an overall response rate of 94%. Females constituted 75.7% of the study population. Overall, 87.8% of the study cohort indicated willingness to get vaccinated. Factors associated independently with vaccination hesitancy included: younger age, lower attained education, lower knowledge score, physician recommendation against vaccination, not receiving the influenza vaccine annually, and other beliefs and attitudes as reported in table 1.

Table 1. Independent predictors of COVID-19 vaccine hesitancy among study respondents

Conclusion

Most survey respondents indicated willingness to receive COVID-19 vaccination. The perception or belief that vaccination is more harmful than COVID-19 disease represented an especially robust barrier against vaccination. Since recommendations made by healthcare providers were strongly associated with either vaccination hesitancy or willingness to get vaccinated, developing educational strategies at this level could enhance vaccine acceptance in an effort to curb the pandemic.

Disclosures

Robert A. Bonomo, MD, entasis (Research Grant or Support)Merck (Grant/Research Support)NIH (Grant/Research Support)VA Merit Award (Grant/Research Support)VenatoRx (Grant/Research Support)

1111. Therapeutic Drug Monitoring of Colistin in Cerebrospinal Fluid in the Treatment of Neurosurgical Meningitis caused by Pseudomonas aeruginosa and KPC-producing Enterobacterales

Background

Central nervous system (CNS) infections caused by carbapenem-resistant Enterobacterales (CRE) and Difficult-to-treat resistant (DTR)-P. aeruginosa (PA) present a therapeutic dilemma. Therapies are limited due to antibiotic resistance and inadequate CNS diffusion. Intraventricular polymyxins are utilized in this setting despite a lack in pharmacokinetic data after CNS injection. We describe the utilization of intravenous and intrathecal polymyxin E [colistimethate (CMS)] therapeutic drug monitoring (TDM) in 3 cases of post-neurosurgical meningitis.

Methods

Bacterial identification and susceptibility testing were performed using MicroScan. TDM was employed by dosing CMS at 125,000 IU (i.e., 4.1 mg CBA or 10 mg) administered via external ventricular drain twice daily and 4.5 MIU (133.2 CBA or 360 mg) CMS administered over 30 minutes IV twice daily. Four pairs of CSF and blood samples were collected for each patient (Table 1). Samples were placed on ice to minimize in-vitro conversion of CMS to Colistin. Colistin binding in plasma and CSF was measured using ultracentrifugation. Concentrations of CMS and Colistin in CSF and human plasma were determined by liquid chromatography/mass spectrometry. Patients A, B and C received 20, 15, and 12 doses of CMS, respectively, prior to TDM.

Results

Bacterial cultures revealed DTR PA, bla_KPCE. cloacae and bla_OXA-48K. pneumoniae for patients A, B and C, respectively. Colistin minimum inhibitory concentrations (MIC) were 0.5 µg/ml, 0.125 µg/ml, and 0.125 µg/ml, respectively. The measured CSF and plasma concentrations of CMS, Colistin, and binding are shown in Table 1. Clinical resolution and microbiological cure were attained in all patients.

Therapeutic Drug Monitoring of Unchanged CMS and Formed Colistin in CSF samples for patient A, B, and C

Therapeutic Drug Monitoring of Unchanged CMS and Formed Colistin in Plasma Samples for patient A, B, and C

Conclusion

Favorable concentrations of formed Colistin and CMS in CSF were achieved in 3 patients with complicated CNS infection. To the best of our knowledge, this is the first study to report the binding of Colistin in CSF in humans. A TDM method was effectively applied to demonstrate that Colistin achieves and maintains the PK/PD target (fAUC/MIC) [ratio of area under the plasma concentration curve of unbound drug to MIC] that best correlates with killing activity. Overall, our results support intraventricular polymyxins for treating DTR Gram-negative CNS infections.

Disclosures

Robert A. Bonomo, MD, entasis (Research Grant or Support)Merck (Grant/Research Support)NIH (Grant/Research Support)VA Merit Award (Grant/Research Support)VenatoRx (Grant/Research Support)

Orthopedic Implant-Associated and Central Venous Catheter-Associated Infections Caused by Microbacterium spp. in the Veterans Affairs Healthcare System from 2000 to 2020

Background: A 72-year-old male developed a late-onset infection of an internal fixation device caused by Microbacterium oxydans. Although often considered contaminants, bacteria from the genus Microbacterium may also be pathogens. We also summarize cases from the Veteran Health Administration (VHA) from which Microbacterium isolates were recovered and review the relevant literature. Patients and Methods: Using the national VHA database, we identified patients with cultures that grew Microbacterium spp. We also review published clinical reports describing Microbacterium spp. as a cause of infections. Results: Between January 2000 and September 2020, 18 cases had Microbacterium spp. Of those, Microbacterium isolates were regarded as pathogens for seven cases; all involved prosthetic material that was consequently removed. Two patients had internal fixation devices whereas the remaining five were patients with a central venous catheter. Conclusions: For patients with prosthetic material, recovery of Microbacterium spp. from device-related clinical cultures should prompt consideration of device removal when possible.

Monitoring Ceftazidime-Avibactam and Aztreonam Concentrations in the Treatment of a Bloodstream Infection Caused by a Multidrug-Resistant Enterobacter sp. Carrying Both Klebsiella pneumoniae Carbapenemase-4 and New Delhi Metallo-β-Lactamase-1

In an infection with an Enterobacter sp. isolate producing Klebsiella pneumoniae Carbapenemase-4 and New Delhi Metallo-β-Lactamase-1 in the United States, recognition of the molecular basis of carbapenem resistance allowed for successful treatment by combining ceftazidime-avibactam and aztreonam. Antimicrobial synergy testing and therapeutic drug monitoring assessed treatment adequacy.

1444. Characterization of a Novel Pathogen in Immunocompromised Patients: Elizabethkingia Anopheles

Background

A 60-year-old woman with acute myeloid leukemia developed fever and cough post induction chemotherapy. Meropenem and vancomycin were administered as empiric therapy. A bloodstream infection due to resistant E. meningoseptica was initially identified. Ceftazidime-avibactam and aztreonam (ATM) were next administered. Minocycline and trimethoprim/sulfamethoxazole (TMP/SMX) were added as the patient deteriorated and died ten days later.

Methods

MIC testing /disc diffusion assays were done according to CLSI guidelines. Whole genome sequencing (WGS) was performed, assembled, and annotated using PATRIC.org and compared to Institute Pasteur cgMLST instance of the BIGSdb database tool. Resistant genes and plasmids were identified by the Center for Genomic epidemiology.

Results

Core genome MLST and average nucleotide identity of 99.46% revealed the organism as E. anophelis, not E. meningoseptica. The WGS assembly resulted in 118 contigs with a chromosome of 4,110,726 bp. Plasmids were not identified. Resistance genes bla_B11, bla_GOB-13 (a metallo beta-lactamase) and bla_CME-1 were detected. E. anophelis was resistant to multiple drug classes including aminoglycosides, vancomycin, cephalosporins, and carbapenems. Mechanism based susceptibility testing using double-disc diffusion assays demonstrated susceptibility to cefiderocol (MIC 1 µg/ml), minocycline, TMP/SMX, linezolid, and modestly wider zones of inhibition with the addition of ATM. Susceptibility results are shown in Table 1.

Antimicrobial susceptibility testing using various BLIs and combinations with Aztreonam

Conclusion

This is one of the first reports describing E. anophelis in immunocompromised hosts. More thorough testing methods are needed for distinguishing between species in the Elizabethkingia genus in hospital settings as there is concern that this may represent a novel opportunistic infection. Per CDC, E. anophelis outbreaks have occurred in three Midwestern states in 2016. Vigilance is warranted to the role of this pathogen in immunocompromised hosts.

Disclosures

Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)

1458. Uncharted territories: applying “precision medicine” to understand the treacherous landscape of extensively and multidrug resistant (XDR and MDR) Pseudomonas aeruginosa in a patient with cystic fibrosis and lung transplantation

Background

Pseudomonas aeruginosa is a persistent and difficult-to-treat pathogen in many patients, especially those with cystic fibrosis (CF). Herein, we describe our experience managing a young woman suffering from CF with XDR P. aeruginosa who underwent lung transplantation. We highlight the contemporary difficulties reconciling the clinical, microbiological, and genetic information.

Methods

Mechanism-based-susceptibility disk diffusion synergy testing with double and triple antibiotic combinations aided in choosing tailored antimicrobial combinations to control the infection in the pre-transplant period, create an effective perioperative prophylaxis regimen, and manage recurrent infections in the post-transplant period. Thirty-six sequential XDR and PDR P. aeruginosa isolates obtained from the patient within a 17-month period, before and after a double-lung transplant were analyzed by whole genome sequencing (WGS) and RNAseq in order to understand the genetic basis of the observed resistance phenotypes, establish the genomic population diversity, and define the nature of sequence changes over time

Results

Our phylogenetic reconstruction demonstrates that these isolates represent a genotypically and phenotypically heterogeneous population. The pattern of mutation accumulation and variation of gene expression suggests that a group of closely related strains was present in the patient prior to transplantation and continued to evolve throughout the course of treatment regardless of antibiotic usage.Our findings challenge antimicrobial stewardship programs that assist with the selection and duration of antibiotic regimens in critically ill and immunocompromised patients based on single-isolate laboratory-derived resistant profiles. We propose that an approach sampling the population of pathogens present in a clinical sample instead of single colonies be applied instead when dealing with XDR P. aeruginosa, especially in patients with CF.

Conclusion

In complex cases such as this, real-time combination testing and genomic/transcriptomic data could lead to the application of true “precision medicine” by helping clinicians choose the combination antimicrobial therapy most likely to be successful against a population of MDR pathogens present.

Disclosures

Federico Perez, MD, MS, Accelerate (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support) Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)

Assessment of Indications and Complications of Caesarean Section in A Private Medical College Hospital of Bangladesh

Caesarean section (CS) is the most frequently performed major operation in obstetrics. Its frequency is gradually increasing because of extended indications. Now-a-days, caesarean section is also being performed at patient's request in absence of a medical indication. It is necessary to assess the risk and benefits to take a judicious decision to select cases for caesarean section. The cross sectional descriptive type of observational study was carried out among purposively selected 100 pregnant women admitted to the department of Obstetrics and Gynaecology of Community Based Medical College Hospital, Mymensingh, Bangladesh during the period of August 2011 to January 2012 to identify elective and emergency indications of caesarean section, to identify the common complications to identify the risk factors associated with complications and to establish a comparison between complications of elective and emergency caesarean section. The median age group of patients being operated was 20 to 25 years and operation were carried out on patients due to various indications. Principal indications were faetal distress (26%), PROM (15%), failed progress of labour and breech presentation were 8% each, other indications were eclampsia (4%), obstructed labour (5%), scar tenderness (4%), history of previous 2 caesarian section 5%. The rate of elective caesarean section was 21% while emergency operations were done in 79% of cases. Among the 100 patients 19% patients developed complications. Among the complications wound infection was most common (37%), then post partum haemorrhage and urinary tract infection 26% and 11% respectively. Other complications were abdominal distension, Puerperal sepsis, anaemic heart failure, wound dehiscence and Wound haematoma 5% each. We should try to keep the rate of caesarean section within optimum ranges (10%) as recommended by World Health Organization.

Knowledge, Perception, Attitudes and Behavior on Influenza Immunization and the Determinants of Vaccination

Background: We sought to determine the knowledge of, perception, attitudes, and behaviors toward influenza virus and immunization, and the determinants of vaccination among students, patients, and Healthcare Workers (HCWs) at the American University of Beirut and its affiliated Medical Center.

Methods: We conducted a cross-sectional study between October 2016 and January 2017 utilizing a self-administered questionnaire that was provided to 247 randomly selected adult participants. Data collected included socio-demographic characteristics, prior vaccination against influenza, knowledge, perception, attitudes, and behaviors toward influenza and influenza immunization. A multivariable regression model was used to evaluate for independent associations between the different variables and regular or yearly vaccination as a primary outcome.

Results: The overall survey response rate was 77%. A substantial proportion of respondents (47.4%) had never received the influenza vaccine. Only 10.2% of students, 19.1% of patients, and 35.6% of HCWs reported regular or yearly influenza vaccine uptake. HCWs had the lowest knowledge score about influenza and its vaccine despite high self-reported levels of knowledge. Barriers to vaccinations included lack of information (31%), fear of adverse effects (29%), and a perception of not being at risk (23%). Several factors were independently associated with regular or yearly vaccination uptake including having children (adjusted OR = 3.8; 95% CI 1.2–12.5), a “very good” self-reported level of knowledge (OR = 16.3; 95% CI 1.4–194.2) and being afraid of the consequences of influenza (OR = 0.2; 95% CI 0.1–0.6).

Conclusion: Adherence rates with regular or yearly vaccination against influenza remain low across all study groups. We were able to identify predictors as well as barriers to vaccination. Future awareness and vaccination campaigns should specifically aim at correcting misconceptions about vaccination, particularly among HCWs, along with addressing the barriers to vaccination. Predictors of vaccination should be integrated in the design of future campaigns.

Using Therapeutic Drug Monitoring to Treat KPC-Producing Klebsiella pneumoniae Central Nervous System Infection With Ceftazidime/Avibactam

This report describes the treatment of Klebsiella pneumoniae carbapenemase (KPC)–3–producing multidrug-resistant K. pneumoniae with ceftazidime/avibactam (CAZ-AVI) in a patient who developed postneurosurgical meningitis and bacteremia. Therapeutic drug monitoring of cerebrospinal fluid and blood samples demonstrated CAZ-AVI concentration levels 20-fold greater than the minimum inhibitory concentration in the first 60 minutes postinfusion, providing evidence for the utility of CAZ-AVI in treating KPC–Klebsiella pneumoniae central nervous system infections.

Beta-Hemolytic Streptococcal Infective Endocarditis: Characteristics and Outcomes From a Large, Multinational Cohort

Background

Beta-hemolytic streptococci (BHS) are an uncommon cause of infective endocarditis (IE). The aim of this study was to describe the clinical features and outcomes of patients with BHS IE in a large multinational cohort and compare them with patients with viridans streptococcal IE.

Methods

The International Collaboration on Endocarditis Prospective Cohort Study (ICE-PCS) is a large multinational database that recruited patients with IE prospectively using a standardized data set. Sixty-four sites in 28 countries reported patients prospectively using a standard case report form developed by ICE collaborators.

Results

Among 1336 definite cases of streptococcal IE, 823 were caused by VGS and 147 by BHS. Patients with BHS IE had a lower prevalence of native valve (P < .005) and congenital heart disease predisposition (P = .002), but higher prevalence of implantable cardiac device predisposition (P < .005). Clinically, they were more likely to present acutely (P < .005) and with fever (P = .024). BHS IE was more likely to be complicated by stroke and other systemic emboli (P < .005). The overall in-hospital mortality of BHS IE was significantly higher than that of VGS IE (P = .001). In univariate analysis, variables associated with in-hospital mortality for BHS IE were age (odds ratio [OR], 1.044; P = .004), prosthetic valve IE (OR, 3.029; P = .022), congestive heart failure (OR, 2.513; P = .034), and stroke (OR, 3.198; P = .009).

Conclusions

BHS IE is characterized by an acute presentation and higher rate of stroke, systemic emboli, and in-hospital mortality than VGS IE. Implantable cardiac devices as a predisposing factor were more often found in BHS IE compared with VGS IE.

635. Genomic Evolution and Progression of Antimicrobial Resistance in a Series of Extensively Drug-Resistant Pseudomonas aeruginosa (XDR-Pa) Isolates from a Cystic Fibrosis Lung Transplant Recipient

Background

Chronic respiratory infection due to extensively drug-resistant Pseudomonas aeruginosa (XDR-Pa) is a significant cause of mortality in cystic fibrosis (CF) patients. The CF respiratory anatomy, chronic antibiotic use, and PA colonization creates a milieu for high evolutionary pressure and genetic diversity. We sought to explore the progression of antibiotic resistance and genome evolution of XDR-Pa in a longitudinal series of isolates collected from an18-year-old CF patient who underwent lung transplantation.

Methods

Consecutive respiratory isolates were collected from December 2016 to March 2018. Standard disk diffusion methods were used to evaluate antimicrobial susceptibility. Whole-genome sequencing (WGS) data were obtained on an Illumina NextSeq and assembled. Variants were identified using the GATK HaplotypeCaller and their functional impact was determined using snpEff. Maximum likelihood phylogenetic trees were constructed using MEGA and BEAST. Panther was used to test for enrichment of Gene Ontology functional categories among mutated genes.

Results

Phylogenetic analysis of complete genome sequences showed that 18 isolates formed a monophyletic group. Analysis using BEAST showed that genomes shared a common ancestor that was present prior to transplant. Over 300 single nucleotide variants and small insertion-deletion mutations were found, in comparison with a reconstruction of the ancestral sequence (Figure 1). Shared patterns of antibiotic susceptibility profiles were largely concordant with phylogenetic clustering and trended toward a decrease in susceptibility over time. Two different frameshift mutations in the DNA mismatch repair gene mutL were found in 15 genomes and these exhibited an increased rate of transition to transversion mutations, consistent with a hypermutator phenotype.

Conclusion

WGS of XDR-Pa identified variations in antibiotic resistance and virulence genes. Changes in mutL likely accelerated the accumulation of mutations. Multiple related sub-groups of strains appear to have been circulating prior to transplant and continued to diverge during the treatment period. Correlating antibiotic pressure, susceptibility profiles, and WGS in XDR-Pa from a single patient reveals the clinical impact of genomic evolution in CF.

Disclosures

All authors: No reported disclosures.

610. Meropenem-vaborbactam (MV) In Vitro Activity Against Carbapenem-Resistant Klebsiella pneumoniae (CRKP) Isolates with Outer Membrane Porin Gene Mutations

Background

Vaborbactam is a cyclic boronic acid β-lactamase inhibitor (BLI) developed to potently inhibit Ambler class A&C enzymes, including KPC carbapenemases. Metallo-β-lactamases (MBL) and some Class D oxacillinases (OXA) are not inactivated by vaborbactam. Meropenem-vaborbactam (MV) was recently approved for the treatment of carbapenem-resistant Enterobacteriaceae complicated urinary tract infections. Recent studies have identified outer membrane porin (Ompk35 and -36) mutations in Klebsiella pneumoniae (KP) as a mechanism of decreased susceptibility to MV. We evaluated the activity of MV against a historical cohort of KP clinical isolates with these porin gene mutations.

Methods

WGS of carbapenem-resistant KP clinical isolates was performed and those harboring mutations in Ompk35 or Ompk36 were selected for testing. Strain KP ATCC BAA-1705 was used as a positive control. Meropenem and MV minimum inhibitory concentrations (MIC) were determined by broth microdilution (BMD) in custom 96-well plates (ThermoFisher Scientific) with a constant 8 µg/mL vaborbactam concentration. The MIC of ceftazidime–avibactam (CZA) was determined by standard BMD reference methods and interpreted according to CLSI criteria.

Results

A total of 105 KP isolates with either partial or complete mutations in outer membrane porin genes were included in the analysis. All isolates were resistant to Meropenem. The median MV MIC was 0.03 µg/mL (range, 0.015 to >16 µg/mL). Eleven isolates (10.4%) were resistant to MV. Sixteen additional isolates (16.1%) demonstrated higher than expected MV MICs ranging from 1 to 4 µg/mL. Only 1/11 resistant isolates harbored a gene for MBL production. Gene mutations in bla_KPC were not detected. See Table 1 for characteristics of resistant isolates.

Conclusion

Resistance and decreased susceptibility to MV is demonstrated in a historical cohort of KP clinical isolates dating back to 2013. WGS reliably identifies porin variants secondary to gene mutations in Ompk35 and Ompk36 as the underlying mechanism of decreased susceptibility. CZA appears to retain activity against these isolates. Caution should be exercised regarding the empiric use of MV against increasingly resistant KP as a result of non-β-lactamase-mediated mechanisms.

Disclosures

All authors: No reported disclosures.

234. Reversal of Carbapenem and Amikacin Susceptibilities in Isogenic Klebsiella pneumoniae From a Patient with Persistent Bacteriuria

Background

Genomic tools permit a detailed analysis of antibiotic resistance determinants in bacteria, or resistome. Here we discuss variations in antibiotic resistance in K. pneumoniae (Kp) not explained by changes in the resistome

Methods

We compared Kp strains with divergent carbapenem and aminoglycoside susceptibilities. After identification of bacteria, antibiotic susceptibility testing was performed according to CLSI guidelines. Draft genome sequences were generated using Illumina MiSeq (Nextera paired-end library) and assembled using CLC Genomics Workbench (CLC bio, Cambridge, MA). Resistome, plasmid types and MLST were investigated using the CGE platform (http://cge.cbs.dtu.dk), while capsular type and virulence genes were investigated using the Pasteur BIGsDB database (https://bigsdb.pasteur.fr).

Results

While receiving amoxicillin-clavulanate, a 44-year old man with diabetes mellitus and paraplegia with neurogenic bladder grewKp resistant to carbapenems and amikacin from urine. He was treated with fosfomycin and amikacin, followed by imipenem and plazomicin, prior to lithotripsy. Three months later, while off antibiotics, urine cultures grew Kp susceptible to carbapenems and amikacin (figure). Genetic comparison between resistant (November 20, 2018) and susceptible (January 30, 2019) strains revealed they were isogenic, only differing by 559 SNPs (table). Both were ST14, presented capsular type 16, and shared cehalosporinase (bla_SHV-28, bla_CTX-M-15, bla_TEM-1B, bla_OXA-1) and aminoglycoside modifying enzyme (AME) (aph(3’’)-Ib, aph(6)-Id, aac(6’)-Ib-cr) genes. Although both had mutations in the outer membrane porin OmpK36, these differed (stop AA125 and frameshift AA183, respectively)

Conclusion

Carbapenem resistance in the initial Kp is likely explained by overexpression of cephalosporinases in combination with changes in membrane permeability, while amikacin resistance is likely due to AMEs. Since no significant gene variation was observed in the susceptible Kp, reversal of resistance was likely due to decreased expression of cephalosporinases and AMEs after antibiotics were stopped. Incorporation of antibiotic history and host factors can explain clinically important changes in antibiotic resistance

Disclosures

All authors: No reported disclosures.

Polymyxins: To Combine or Not to Combine?

Polymyxins have been a mainstay for the treatment of extensively drug resistant (XDR) Gram-negative bacteria for the past two decades. Many questions regarding the clinical use of polymyxins have been answered, but whether the administration of polymyxins in combination with other antibiotics leads to better outcomes remains unknown. This review discusses the limitations of observational studies that suggest a benefit of combinations of colistin and carbapenems to treat infections caused by carbapenem-resistant Enterobacteriaceae (CRE), especially Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae, and summarizes the results of randomized controlled trials in which treatment with colistin in combination with meropenem or rifampin does not lead to better clinical outcomes than colisitn monotherapy in infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB). Although the introduction of new antibiotics makes it possible to treat certain strains of CRE and carbapenem-resistant P. aeruginosa (CRPA) with polymyxin-sparing regimens, the use of polymyxins is, for now, still necessary in CRAB and in CRE and CRPA harboring metallo-beta-lactamases. Therefore, strategies must be developed to optimize polymyxin-based treatments, informed by in vitro hollow fiber models, careful clinical observations, and high-quality evidence from appropriately designed trials.

700. Identification and Whole-Genome Sequencing (WGS) of Meropenem-Vaborbactam (MV) Resistant Klebsiella pneumoniae (MVRKP) Among Patients Without Prior Exposure to MV: Collateral Damage

Background

Methods

Results

Conclusion

Disclosures

2395. Mechanism-Based-Susceptibility Testing (MBST) Using Disc Diffusion Assays (DDA) to Guide Treatment of Multidrug- and Extensively Drug-Resistant Pseudomonas aeruginosa (MDR-XDR-Pa) in a Cystic Fibrosis (CF) Lung Transplant Recipient; Are We Ready for Combination Therapy vs. MDR-XDR-Pa?

Background

Lung infections with MDR-XDR-Pa in patients with CF are challenging due to the emergence of antibiotic resistance. We applied MBST with DDA to guide combination antibiotic therapy in an 18-year-old woman with CF. We investigated if this approach can assist in choosing effective regimens.

Methods

Consecutive Pa respiratory isolates were collected between 12/16 and 3/18 and typed with MLST. After automated antibiotic susceptibility (AST) and Kirby-Bauer testing, we performed double or triple DDAs. Combinations were based on mechanisms (MBST) of anti-pseudomonal antibiotics (e.g., targeting of penicillin-binding proteins, β-lactamase inhibition, and cell membrane disruption).

Results

During therapy, 1859 antibiotic-days were administered. Fifteen Pa isolates, (9 sequence type (ST) 2100 and 1 ST463) with varying AST patterns were found (figure). MBST with DDA revealed active combinations for isolates resistant to individual antibiotics (table). These combinations led to a microbiological response permitting lung transplantation. Antibiotic regimens were also informed by allergies, clinical and radiologic findings.

Conclusion

Strains with evolving resistance profiles recapitulate the dynamic nature of respiratory infections in CF. Double or triple DDAs identified potential treatment options, e.g., vs. MDR-XDR Pa. MBST can support the management of challenging infections.

Table: Antimicrobial combinations reflecting zones of inhibition by strain and date.

CZA: ceftazidime–avibactam; C/T: ceftolozane-tazobactam; TOB: tobramycin; PMB: polymyxin B; FOF: fosfomycin; TZP: piperacillin–tazobactam; CIP: ciprofloxacin; IPM: imipenem; MEM: meropenem.

Bold: largest zone

Disclosures

L. M. Abbo, Roche Diagnostics: Scientific Advisor, Consulting fee. M. I. Morris, Chimerix: Investigator and Scientific Advisor, Consulting fee and Research support. Merck: Investigator, Research grant.

Therapies for multidrug resistant and extensively drug-resistant non-fermenting gram-negative bacteria causing nosocomial infections: a perilous journey toward 'molecularly targeted' therapy

INTRODUCTION

Non-fermenting Gram-negative bacilli are at the center of the antimicrobial resistance epidemic. Acinetobacter baumannii and Pseudomonas aeruginosa are both designated with a threat level to human health of 'serious' by the Centers for Disease Control and Prevention. Two other major non-fermenting Gram-negative bacilli, Stenotrophomonas maltophilia and Burkholderia cepacia complex, while not as prevalent, have devastating effects on vulnerable populations, such as those with cystic fibrosis, as well as immunosuppressed or hospitalized patients. Areas covered: In this review, we summarize the clinical impact, presentations, and mechanisms of resistance of these four major groups of non-fermenting Gram-negative bacilli. We also describe available and promising novel therapeutic options and strategies, particularly combination antibiotic strategies, with a focus on multidrug resistant variants. Expert commentary: We finally advocate for a therapeutic approach that incorporates in vitro antibiotic susceptibility testing with molecular and genotypic characterization of mechanisms of resistance, as well as pharmacokinetics and pharmacodynamics (PK/PD) parameters. The goal is to begin to formulate a precision medicine approach to antimicrobial therapy: a clinical-decision making model that integrates bacterial phenotype, genotype and patient's PK/PD to arrive at rationally-optimized combination antibiotic chemotherapy regimens tailored to individual clinical scenarios.

Prevalence of Metallo-β-lactamase Producing Non-fermentative Pseudomonas Species from Clinical Isolates in Dhaka, Bangladesh

Antimicrobial drug resistance, a global concern, has been increasing unpredictably in microorganism causing human infections specially among Gram negative non-fermenting Pseudomonas spp. Carbapenems, a beta lactam antibiotics, are the most potent and effective drug usually kept reserved for treating the multi-drug resistant Psedomonas spp and other infections caused by organisms producing Extended Spectrum Beta Lactamase (ESBL) and AmpC. Clinical utility of carbapenem will reduce when resistant bacteria evolve due to production of carbapenem hydrolyzing Metallo-β-lactamase (MBL) which confers high-level resistance to all beta-lactam antibiotics except aztreonam. The various reports on the prevalence of MBLs are available from many countries but few from Bangladesh. We investigated the prevalence of MBL production in these Pseudomonads obtained from clinical sources in an uraban setting in Dhaka, Bangladesh. A total of 29,136 specimens were processed for culture from January 2011 and December 2015 from non duplicated patients attending diagnostic unit of icddr,b from different settings of Bangladesh. The specimens included urine 14,323; blood 11,378; other body fluid 2,487; sputum 535 and tracheal aspirate 413. All specimens were processed for culture following standard bacteriological methods and the Pseudomonas spp were identified following defined standard biochemical procedures. Metallo-β-lactamase (MBL) was determined by EDTA disk synergy (EDS) test. Antimicrobial susceptibility test was performed by disk diffusion method and susceptibility pattern was interpreted and reported following Clinical Laboratory Standard Institute (CLSI) guideline. From 29,136 specimens a total of 2,340(8%) were isolated and identified as Pseudomonas spp. Of the identified Pseudomonas spp, 238(57.6%) were from tracheal aspirate, 216(40.4%) from sputum, 902(36.7%) from other body fluids, 463(4.1%) from blood and 521(3.6%) from urine samples. From 2,340 Pseudomonas spp, by selective sampling, imipenem-meropenem resistant and intermediate susceptible 100 strains were tested for MBL production and 92 were found positive. Tracheal aspirate showed 38%, other body fluids 30%, Urine 17%, sputum 4% and blood 3% MBL production respectively. Irrespective of the sources of specimens, Pseudomonas spp showed 71% resistance to cefixime, 70% to ceftriaxone, 64% to gentamicin, 56% to piperecillin+tazobactam, 50% to ciprofloxacin, 49% to amikacin, 46% to netilmicin, 45% to ceftazidime, 30% to meropenem, 26% to imipenem and 19% to polymyxin B. As multi-drug resistant Pseudomonas showed high level of (92%) MBL production, so MBL detection testing facility may be a useful battery to determine MDR producing Pseudomonas from clinical isolates.

Microbiology of Chronic Suppurative Otitis Media in a Tertiary Care Hospital in Bangladesh

This cross sectional prospective study was carried out in the Department of Otolaryngology-Head & Neck Surgery, Bangabandhu Sheikh Mujib Medical University (BSMMU) and Department of Microbiology, University of Dhaka from July 2012 to June 2013. The objectives of this study were to identify the common microorganisms involved and the antibiograms of chronic suppurative otitis media (CSOM) patients in this tertiary care hospital in Bangladesh. A total of 117 patients clinically diagnosed of CSOM were enrolled in the study. They had chronic ear discharge & had not received any topical or systemic antibiotics for the previous five days. Swabs was taken and cultured for bacteria. The standard of isolation and identification was followed. Antimicrobial susceptibility of all aerobic bacterial isolates was performed by using modified Kirby Bauer Disk diffusion method. There were 186 positive cultures for organism from 117 patients. The most common causal organisms isolated were S. aureus (47.30%) and Pseudomonas spp. (27.40%) followed by S. epidermidis (16.10%), Klebsiella spp. (8.10%) and Escherichia coli. (1.10%). Gentamicin showed the highest sensitivity (89.8%) to S. aureus whereas erythromycin showed the lowest sensitivity (14.8%) with highest resistance (67%) to S. aureus. Pseudomonas spp. showed highest sensitivity against ciprofloxacin (78.4%) and highest resistance against cloxacillin (96.1%). Novobiocin showed the highest sensitivity (100%) followed by chloram phenicol (94.1%) to S. epidermidis. Klebsiella spp. and E. coli showed highest sensitivity against chloram phenicol. This study suggests that Staphylococcus aureus and Pseudomonas are the commonest bacteria involved in CSOM in Bangladesh and Ciprofloxacin is an important tool in the management of active CSOM.

Sites of colonization in hospitalized patients with infections caused by extended-spectrum beta-lactamase organisms: a prospective cohort study

Background

The objective of this study was to determine whether patients infected with extended-spectrum beta-lactamase (ESBL)-producing organisms are colonized at multiple body sites.

Methods

This was a prospective cohort study at a tertiary care center in Beirut, Lebanon. Hospitalized patients with infections caused by ESBL-producing organisms were included. Cultures were obtained from the primary site of infection as well as from other sites (skin, nasopharynx, urine, rectum). Molecular analysis was performed on isolates to determine clonal relatedness.

Results

One hundred patients were included in the study. Only 22 patients had positive cultures from sites other than the primary site of infection. The most common ESBL gene was CTX-M-15 followed by TEM-1. In 11 of 22 patients, isolates collected from the same patient were 100% genetically related, while in the remaining patients, genomic relatedness ranged from 42.9% to 97.1%.

Conclusions

Colonization at sites other than the primary site of infection was not common among our patient population infected with ESBL-producing organisms. The dynamics of transmission of these bacterial strains should be studied in further prospective studies to determine the value of routine active surveillance and the need for expanded precautions in infected and colonized patients.

Evaluation of efficiency of nested multiplex allele-specific PCR assay for detection of multidrug resistant tuberculosis directly from sputum samples

For an effective control of tuberculosis, rapid detection of multidrug resistant tuberculosis (MDR-TB) is necessary. Therefore, we developed a modified nested multiplex allele-specific polymerase chain reaction (MAS-PCR) method that enables rapid MDR-TB detection directly from sputum samples. The efficacy of this method was evaluated using 79 sputum samples collected from suspected tuberculosis patients. The performance of nested MAS-PCR method was compared with other MDR-TB detection methods like drug susceptibility testing (DST) and DNA sequencing. As rifampicin (RIF) resistance conforms to MDR-TB in greater than 90% cases, only the presence of RIF-associated mutations in rpoB gene was determined by DNA sequencing and nested MAS-PCR to detect MDR-TB. The concordance between nested MAS-PCR and DNA sequencing results was found to be 96·3%. When compared with DST, the sensitivity and specificity of nested MAS-PCR for RIF-resistance detection were determined to be 92·9 and 100% respectively.

SIGNIFICANCE AND IMPACT OF THE STUDY

For developing- and high-TB burden countries, molecular-based tests have been recommended by the World Health Organization for rapid detection of MDR-TB. The results of this study indicate that, nested MAS-PCR assay might be a practical and relatively cost effective molecular method for rapid detection of MDR-TB from suspected sputum samples in developing countries with resource poor settings.

Epidemiology of bloodstream infections caused by methicillin-resistant Staphylococcus aureus at a tertiary care hospital in New York

BACKGROUND

In the United States, bloodstream infections (BSIs) are predominated by Staphylococcus aureus. The proportion of community-acquired methicillin-resistant S aureus (MRSA) BSI is on the rise. The goal of this study is to explore the epidemiology of BSI caused by S aureus within Staten Island, New York.

METHODS

This is a case-case-control study from April 2012-October 2014. Cases were comprised of patients with BSI secondary to MRSA and methicillin-sensitive S aureus (MSSA). The control group contained patients who were hospitalized during the same time period as cases but did not develop infections during their stay. Two multivariable models compared each group of cases with the uninfected controls.

RESULTS

A total of 354 patients were analyzed. Infections were community acquired in 76% of cases. The major source of BSI was skin-related infections (n = 76). The first multivariable model showed that recent central venous catheter placement was an independent infection risk factor (odds ratio [OR] = 80.7; 95% confidence interval [CI], 2.2-3,014.1). In the second model, prior hospital stay >3 days (OR = 4.1; 95% CI, 1.5-5.7) and chronic kidney disease (OR = 3.0; 95% CI, 1.01-9.2) were uniquely associated with MSSA. Persistent bacteremia, recurrence, and other hospital-acquired infections were more likely with MRSA BSI than MSSA BSI.

CONCLUSION

Most infections were community acquired. The presence of a central venous catheter constituted a robust independent risk factor for MRSA BSI. Patients with MRSA BSI suffered worse outcomes than those with MSSA BSI.

Idiopathic Hemophagocytic Lymphohistiocytosis During Pregnancy Treated with Steroids

Hemophagocytic lymphohistiocytosis (HLH) is a rare and severe clinical syndrome characterized by a dysregulated hyperinflammatory immune response. The diagnosis of HLH during pregnancy is especially challenging due to the rarity of this condition. The highly variable clinical presentation, laboratory findings, and associated diagnoses accompanying this syndrome further complicate the problem. A pronounced hyperferritinemia in the setting of systemic signs and symptoms along with a negative infectious and rheumatological workup should raise suspicions for HLH. While treatment ideally consists of immunosuppressive chemotherapy and hematopoietic stem cell transplant, the potential toxicity to both the pregnant woman and the fetus poses a challenging decision. We report the first case of idiopathic HLH presenting as fever of unknown origin in a pregnant woman successfully treated with steroids.

Epidemiology of carbapenem resistant Klebsiella pneumoniae colonization in an intensive care unit

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged during recent years in several intensive care units. The objective of our study was to determine the incidence of CRKP and the risk factors associated with acquisition during intensive care unit (ICU) stay. This prospective cohort study was conducted between May 2007 and April 2008 in a medical-surgical ICU at a tertiary medical center. Rectal surveillance cultures were obtained from patients on admission and twice weekly. Of screened patients, 7.0% (21/299) were CRKP colonized on admission to the ICU. One hundred eighty (81%) patients were screened at least twice. Of these, 48 (27%) patients acquired CRKP during ICU stay. Of the 69 CRKP colonized patients (both imported and ICU acquired), 29% (20/69) were first identified by microbiologic cultures, while screening cultures identified 49 patients (71%). Of these, 23 (47%) subsequently developed clinical microbiological cultures. Independent risk factors for CRKP acquisition included recent surgery (OR 7.74; CI 3.42-17.45) and SOFA score on admission (OR 1.17; CI 1-1.22). In conclusion, active surveillance cultures detected a sizable proportion of CRKP colonized patients that were not identified by clinical cultures. Recent surgical procedures and patient severity were independently associated with CRKP acquisition.

Rapid detection of Haemophilus influenzae type b in Bangladeshi children with pneumonia and meningitis by PCR and analysis of antimicrobial resistance

A polymerase chain reaction (PCR) assay with primers from 'bexA' gene was compared with culture for the detection of Haemophilus influenzae type b (Hib) in clinical samples from children with pneumonia and meningitis. Of 200 sera (180 from pneumonia, 20 from non-pneumonia patients) tested by PCR (serum-PCR), Hib was detected in 15 of 16 blood culture-positive and in 6 blood culture-negative pneumonia cases. When compared with the results of blood culture, serum-PCR had sensitivity, specificity, and accuracy index of 93.7%, 96.7%, and 96.5% respectively. Of 120 cerebrospinal fluid (CSF) samples from meningitis patients tested by culture and PCR (CSF-PCR), the latter method could detect Hib in all 15 culture-positive and in 8 of 105 culture-negative cases, showing sensitivity, specificity, and accuracy index of 100%, 92.4%, and 94.4% respectively. The PCR result was available within a day. Antimicrobial susceptibility of Hib was determined by the disc-diffusion method. High rate of resistance to ampicillin (54.8%), chloramphenicol (48.4%), and co-trimoxazole (80.6%) was observed among 31 invasive Hib isolates with resistance to all 3 drugs (multiresistance) in 48.4% of the isolates. All the Hib isolates were susceptible to ceftriaxone. The study has shown that PCR is a rapid, sensitive and specific diagnostic test for Hib from clinical samples, and a combination of culture and PCR is necessary for the detection of Hib infections to the maximum extent for case management to reduce morbidity, mortality, and complications of the invasive Hib infections. A high prevalence of multiresistant Hib strains is a matter of concern.

Seroprevalence of hepatitis B, hepatitis C, CMV and HIV in multiply transfused thalassemia patients: results from a thalassemia day care center in Malaysia

Regular blood transfusions for patients with thalassemia have improved their overall survival although these transfusions carry a definite risk of the transmission of certain viruses. Infection with hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV) and human immunodeficiency virus (HIV) leads to complications which contribute to the morbidity and mortality of patients with thalassemia. We analyzed the blood samples taken from 85 transfusion dependent thalassemics receiving treatment at the day care center in Hospital Universiti Kebangsaan Malaysia and found that the seroprevalence rates for HBV, HCV and CMV were 2.4%, 22.4% and 91.8% respectively. None of the patients tested positive for HIV. Those positive for HBV and HCV will require further tests and treatment if chronic hepatitis is confirmed.

Development and evaluation of co-agglutination test to detect rotavirus antigens in stools of patients with diarrhoea

Rotavirus is the most common cause of acute diarrhoea in infants and children in both the developed and developing countries including Bangladesh. Information about rotavirus diarrhoea in Bangladesh is insufficient primarily due to the lack of diagnostic facilities due to the high cost of reagents and equipment and lack of skilled personnel. A simple, suitable and less costly technique of co-agglutination test using protein-A secreting staphylococci was developed and evaluated against a commercially available ELISA kit to detect rotavirus antigen in stools of patients with diarrhoea. Staphylococcus cowan strain 1 was grown and coated with rabbit antisera raised against RV5 and SA11 rotavirus strains. The antibody-coated staphylococci were agglutinated specifically by rotavirus present in faecal samples within one or two minutes. A total of 1332 stool specimens were tested by co-agglutination and ELISA, of which 210 (15.77%) were positive by ELISA and 276 (20.72%) by co-agglutination test. Compared to ELISA, sensitivity of co-agglutination test was 76.19%, specificity 89.66% and predictive values of a positive and a negative test were 57.97% and 95.26% respectively. The results indicate that the co-agglutination test is a simple and suitable technique for rapid screening of rotavirus infection which could be adopted in clinical practice.

Rapid identification of Vibrio cholerae serotype O1 from primary isolation plates by a coagglutination test

A coagglutination test was developed for identifying suspected colonies of Vibrio cholerae serotype O1 directly from primary isolation plates. Visible agglutination occurs when V. cholerae O1 antibody attached to cell-wall protein A of Staphylococcus aureus reacts with its homologous antigen. From 314 faecal samples from clinically suspected cases of cholera, 210 colonies from thiosulphate citrate bile salts sucrose (TCBS) agar and 222 colonies from taurocholate tellurite gelatin (TTG) agar were tested as suspect V. cholerae. In each case 204 isolates were identified as V. cholerae O1 by conventional methods and also gave positive results for V. cholerae O1 in the coagglutination test; with one partial exception, no other colonies tested gave positive results. The coagglutination test is simple and inexpensive and provides a result 24 h earlier than conventional methods.

Epidemiological study and comparison of pyrantel and levamisole in the treatment of roundworm and hookworm infestations

Stool examined for presence of nematodes from 467 school students in Dacca city showed 48% ova positive cases with 22% among them cases of mixed nematode infection. Highest prevalence of 58% was observed with roundworm and 5% was hookworm infestations. Among hookworm cases, Necator americana (68%) appears to be the predominant species. Two anthelmintics-pyrantel and levamisole achieved similar high cure rate (around 97%) and Egg reduction rate of 99% in roundworm infection. However, pyrantel was observed to be more effective in hookworm infestation (87% against 60%) particularly in Necator americana cases.