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Peera Hemarajata

Peera Hemarajata
County of Los Angeles · Department of Public Health

M.D., Ph.D., D(ABMM)

About

68
Publications
28,535
Reads
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2,557
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Introduction
A physician and clinical microbiologist with extensive background both clinical medicine and molecular microbiology. Specialized in rapid molecular assay development for infectious diseases diagnostics, and next-generation sequencing, whole genome sequencing, and microbial genomics. Research interests in mechanisms and prediction of antimicrobial resistance, and antimicrobial susceptibility testing.
Additional affiliations
July 2016 - present
University of California, Los Angeles
Position
  • Instructor
July 2014 - June 2016
University of California, Los Angeles
Position
  • Clinical Microbiology Fellow
April 2013 - June 2014
Texas Children's Hospital
Position
  • Therapeutic Microbiology Fellow
Education
July 2007 - April 2013
Baylor College of Medicine
Field of study
  • Molecular Virology and Microbiology
June 2000 - May 2006
Chulalongkorn University
Field of study
  • Medicine

Publications

Publications (68)
Article
Objectives This study aimed to assess whether the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Epsilon variant (B.1.429/427) is more virulent, leading to more hospitalization and more severe disease requiring intensive care unit (ICU) admission. Methods SARS-CoV-2 genomic surveillance was performed on respiratory samples from 231 u...
Article
A suspected outbreak of influenza A and SARS-CoV-2 at a long-term care facility in Los Angeles County was months later, determined to not involve influenza. To prevent inadvertent transmission of infections, facilities should use highly specific influenza diagnostics and follow CDC guidelines that specifically address infection control challenges.
Article
We identified an emerging SARS-CoV-2 variant by viral whole-genome sequencing of 2,172 nasal/nasopharyngeal swab samples from 44 counties in California, a state in the Western United States. Named B.1.427/B.1.429 to denote its 2 lineages, the variant emerged in May 2020 and increased from 0% to >50% of sequenced cases from September 2020 to January...
Preprint
Full-text available
We identified a novel SARS-CoV-2 variant by viral whole-genome sequencing of 2,172 remnant nasal/nasopharyngeal swab samples from 44 counties in California. Named B.1.427/B.1.429 or 20C/L452R, the variant emerged around May 2020 and increased from 0% to >50% of sequenced cases from September 1, 2020 to January 29, 2021, exhibiting an estimated 18.6...
Article
On August 24, 2020, the Centers for Disease Control and Prevention (CDC) updated its website to highlight that asymptomatic individuals, even those with exposure to a COVID-19 positive contact, do not necessarily need to be tested unless they have medical conditions associated with increased risk of severe illness from COVID-19. The CDC subsequentl...
Article
Los Angeles County comprises 4,058 square miles and is home to approximately 10 million residents (1), an estimated 59,000 (0.6%) of whom experience homelessness on a given night (2). In late 2018, Los Angeles County Department of Public Health (LAC DPH) was notified of a case of hepatitis A virus (HAV) infection in a person experiencing homelessne...
Article
Full-text available
Background Historically, endemic Klebsiella pneumoniae carbapenemase (KPC) has accounted for the majority of carbapenem-resistant Enterobacteriaceae (CRE) in Los Angeles County (LAC). The LAC Department of Public Health (DPH) initiated enhanced CRE surveillance in 2016 to determine CRE prevalence and track emerging non-KPC resistance mechanisms (IM...
Article
Full-text available
There are no commercially available Food and Drug Administration–cleared rapid tests for Neisseria gonorrhoeae antimicrobial susceptibility testing. This study evaluated the performance of a laboratory-developed real-time polymerase chain reaction assay for genotyping the gyrA gene to determine antimicrobial susceptibility to ciprofloxacin. Validat...
Article
Objectives: Ceftazidime/avibactam resistance due to mutation in the omega loop of KPC-2 has been documented in vitro and in vivo. This study evaluated the mechanism of ceftazidime/avibactam resistance in a KPC-2-expressing Klebsiella pneumoniae isolated from a patient following ceftazidime/avibactam combination therapy with gentamicin for the trea...
Article
Background: In Pseudomonas aeruginosa, fluoroquinolone exposure promotes resistance to carbapenems through up-regulation of efflux pumps and transcriptional down-regulation of the porin OprD. Evidence of this effect among hematologic malignancy (HM) patients or hematopoietic-cell transplant (HCT) recipients receiving fluoroquinolone prophylaxis fo...
Article
Full-text available
Gyrase A genotyping reliably predicts Neisseria gonorrhoeae susceptibility to ciprofloxacin. It is unknown whether concurrent infections at different anatomic sites harbor different susceptibility profiles. We found a 3.2% frequency of discordant gyrase A genotypes among concurrent but anatomically separate N. gonorrhoeae infections diagnosed at 2...
Article
Daptomycin has become a mainstay therapy for the treatment of serious vancomycin-resistant Enterococcus faecium infections. However, concern exists that current testing methods do not accurately predict clinical success of daptomycin therapy. We evaluated a collection of 40 isolates of E. faecium across 3 centers by reference broth microdilution (B...
Article
Objectives: Antibiotic selective pressure may result in changes to antimicrobial susceptibility throughout the course of infection, especially for organisms that harbour chromosomally encoded AmpC β-lactamases, notably Enterobacter spp., in which hyperexpression of ampC may be induced following treatment with cephalosporins. In this study, we docu...
Article
Full-text available
A carbapenem resistant but ceftriaxone and cefepime susceptible Klebsiella oxytoca was isolated from the blood of a patient with polymicrobial bacteremia after 2 weeks of ertapenem treatment. Whole-genome sequencing identified no carbapenemase gene nor plasmid, but only blaOXY-2-8 gene with a mutation in the promoter that’s been reported to increas...
Article
Full-text available
Background Antimicrobial-resistant Neisseria gonorrheae (NG) is a global public health problem, resulting in limited empirical treatment options. Due to increasing minimum inhibitory concentrations (MICs) of ESCs against NG in the US, it is critical that susceptibility to ESCs be monitored. Since few laboratories routinely perform culture and susce...
Article
Full-text available
Background A wild-type gyrase A (gyrA) genotype of N. gonorrheae reliably predicts susceptibility to ciprofloxacin, which can reduce selection pressure for ceftriaxone-resistant infections, an urgent public health threat. In November 2015, UCLA Health began gyrA genotyping all N. gonorrheae positive specimens. In May 2016, we began sending reminder...
Article
Background: Carbapenem-resistant Klebsiella pneumoniae infections are increasingly prevalent in North American hospitals. We describe an outbreak of carbapenem-resistant K. pneumoniae containing the blaOXA-232 gene transmitted by contaminated duodenoscopes during endoscopic retrograde cholangiopancreatography (ERCP) procedures. Methods: An outbr...
Article
Background/objectives: Herpes zoster (HZ) is caused by reactivation of the varicella zoster virus (VZV), and typically causes a painful, vesicular, dermatomal rash in adults over the age of fifty. However, HZ has been known to present in immunocompetent pediatric patients, which account for under 1% of total cases. Pediatric cases are typically ca...
Article
Full-text available
We investigated the epidemiology of the mutant gyrase A gene, a reliable predictor of ciprofloxacin resistance, in Neisseria gonorrhoeae infections at UCLA Health in Los Angeles, California, USA, during November 1, 2015–August 31, 2016. Among 110 patients with N. gonorrhoeae infections, 48 (44%) had the mutant gyrase A gene.
Article
Background: Novel approaches to combating drug-resistant Neisseria gonorrhoeae infections are urgently needed. Targeted therapy with ciprofloxacin has been made possible by a rapid assay for genotyping the gyrase A (gyrA) gene; a nonmutated gene reliably predicts susceptibility to ciprofloxacin. Methods: We determined the costs of running the gy...
Article
N. gonorrhoeae with decreased susceptibility to extended-spectrum cephalosporins (ESCs) are increasing. We developed an assay to predict N. gonorrhoeae susceptibility to ESCs by targeting penA mosaic XXXIV, an allele prevalent among U.S. isolates with elevated ESC MICs. The assay was 97% sensitive and 100% specific in predicting at least one ESC mi...
Article
Ceftazidime-avibactam is an antibiotic with activity against serine beta-lactamases, including KPC. Recently, reports have emerged of KPC-producing isolates resistant to this antibiotic, including a report of a wild-type KPC-3 producing sequence type 258 Klebsiella pneumoniae that was resistant to ceftazidime-avibactam. We describe a detailed analy...
Conference Paper
Introduction Multidrug-resistant N. gonorrhoeae infections are a threat to public health. In November 2015, UCLA Health began routine gyrase A (gyrA) genotyping all N. gonorrhoeae positive specimens, and reporting genotype and treatment recommendations for wild-type infections. Physicians were educated about wild-type gyrA genotypes predicting cipr...
Conference Paper
Introduction Novel approaches to combating drug-resistant N. gonorrhoeae infections are urgently needed. Targeted therapy with ciprofloxacin for susceptible infections has been made possible by the development of a rapid molecular assay for the determination of mutation in the gyrase A gene of N. gonorrheoae, which reliably predicts susceptibility...
Article
Full-text available
We reported the first clinical case of a ceftazidime-avibactam resistant KPC-3-producing Klebsiella pneumoniae (1), from a patient with no prior history of ceftazidime-avibactam therapy.…
Article
Background: Whole-genome sequencing (WGS) is an emerging and powerful technique by which to perform epidemiological studies in outbreak situations. Methods: WGS was used to identify and evaluate an outbreak of OXA-232-expressing carbapenem-resistant Klebsiella pneumoniae (CRKP) transmitted to 16 patients over the course of 40 weeks via endoscopi...
Article
Multidrug-resistant Neisseria gonorrhoeae is a top threat to public health. In November 2015, UCLA Health introduced a rapid gyrase A (gyrA) genotypic assay for prediction of Neisseria gonorrhoeae susceptibility to ciprofloxacin. We found a significant reduction in ceftriaxone use with a concomitant increase in targeted therapy.
Article
Full-text available
Melioidosis is a potentially fatal infection caused by the bacterium Burkholderia pseudomallei . Clinical diagnosis of melioidosis can be challenging since there is no pathognomonic clinical syndrome and the organism is often misidentified by routine methods used in clinical laboratories. Although the disease is more prevalent in Thailand and North...
Article
Objective: There is a dearth of biospecimen repositories available to perinatal researchers. In order to address this need, here we describe the methodology used to establish such a resource. Study design: With the collaboration of MedSci.net, we generated an online perinatal database with 847 fields of clinical information. Simultaneously, we e...
Data
Table S2. Bacterial strains, vectors, and primers used in this study.
Data
Figure S1. FolC2 was necessary for suppression of TNF production at protein and mRNA levels. (A) L. reuteri cell‐free supernatants (normalized to an OD600 of 1.5) were tested for the ability to inhibit TNF production by TLR2‐activated THP‐1 cells. THP‐1 cells were treated with 100 ng/mL PCK (TLR2 agonist) in the presence of L. reuteri for 3.5 h an...
Data
Table S1. Final Gene Set of Interest – 125 genes potentially involved in immunomodulation by wild‐type 6475.
Article
Biological specimens for microbiological analysis are often collected in BD Vacutainers®, which are not specifically designed for microbial recovery. Bacterial and fungal recovery was analyzed for glass and plastic tubes with or without clot-activating silica. No significant impact was found for the recovery of most bacteria and yeasts tested, howe...
Article
Full-text available
Bacterial-derived compounds from the intestinal microbiome modulate host mucosal immunity. Identification and mechanistic studies of these compounds provide insights into host-microbial mutualism. Specific Lactobacillus reuteri strains suppress production of the proinflammatory cytokine, tumor necrosis factor (TNF), and are protective in a mouse mo...
Article
Background & aims: The duodenoscopes used to perform ERCP have been implicated in several outbreaks of carbapenem-resistant Enterobacteriaceae (CRE) infection. The risk factors for CRE transmission via contaminated duodenoscopes remain unclear. Methods: In this retrospective, single-center case-control study, all patients who underwent ERCP with...
Article
In the US, 19.2% of Neisseria gonorrhoeae isolates are resistant to ciprofloxacin. We evaluated a real-time PCR to predict ciprofloxacin susceptibility using residual DNA from the Roche COBAS® 4800 CT/NG assay. The assay was 100% concordant with agar dilution susceptibility test results for 100 clinical isolates. Among 76 clinical urine and swab sp...
Article
Whole genome sequencing (WGS) was compared to pulse field gel electrophoresis (PFGE) of XbaI digested genomic DNA, as methods by which to evaluate a potential transmission of carbapenem-resistant Klebsiella pneumoniae between two hospital inpatients. PFGE result demonstrated only one band difference between the isolates, suggesting probable related...
Article
Full-text available
Fungal infections in the central nervous system (CNS) are associated with significant morbidity and death. Transient fungemia in immunocompetent patients without any other risk factors for fungemia has been suggested as a possible mechanism that may lead to serious fungal ventriculoperitoneal (VP) shunt infections, but evidence is lacking. The clin...
Article
Introduction Increasing antimicrobial resistance in Neisseria gonorrhoeae has been a major problem worldwide, limiting effective empirical therapeutic options in patients infected with multi-drug resistant strains. Guidelines from U.S. CDC no longer recommend treatment with fluoroquinolones (FQs) due to emergence of resistance nationally. However,...
Article
Full-text available
Ceftazidime-avibactam is the first antimicrobial approved by the U.S. FDA for the treatment of carbapenem-resistant Enterobacteriaceae. Avibactam, a non-β-lactam β-lactamase inhibitor, inactivates class A serine carbapenemases, including Klebsiella pneumoniae carbapenemase (KPC). We report a KPC-producing K. pneumoniae isolate resistant to ceftazid...
Article
The rapid global spread of carbapenem-resistant Enterobacteriaceae (CRE) poses an urgent threat to public health. More than 250 Class D β-lactamases (OXAs) have been described in recent years with variation in β-lactam hydrolytic activity. The plasmid-borne OXA-48 β-lactamase and its variants, are only sporadically identified in the United States,...
Article
Fecal microbiome transplantation (FMT) is an emerging unconventional treatment for ulcerative colitis (UC). The disruption of healthy microbiota composition (dysbiosis) may be an important element of the disease and the restoration of normal microbiota structure may be therapeutic for this condition. In spite of encouraging outcomes in small cohort...
Article
Full-text available
The gut microbiome may modulate intestinal immunity by luminal conversion of dietary amino acids to biologically active signals. The model probiotic organism Lactobacillus reuteri ATCC PTA 6475 is indigenous to the human microbiome, and converts the amino acid L-histidine to the biogenic amine, histamine. Histamine suppresses tumor necrosis factor...
Article
Full-text available
Human microbiome-derived strains of Lactobacillus reuteri potently suppress proinflammatory cytokines like human tumor necrosis factor (TNF) by converting the amino acid l-histidine to the biogenic amine histamine. Histamine suppresses mitogen-activated protein (MAP) kinase activation and cytokine production by signaling via histamine receptor type...
Article
Obesity, metabolic syndrome, and type 2 diabetes are major public health challenges. Recently, interest has surged regarding the possible role of the intestinal microbiota as potential novel contributors to the increased prevalence of these 3 disorders. Recent advances in microbial DNA sequencing technologies have resulted in the widespread applica...
Article
Full-text available
Background: Obesity, metabolic syndrome, and type 2 diabetes are major public health challenges. Recently, interest has surged regarding the possible role of the intestinal microbiota as potential novel contributors to the increased prevalence of these 3 disorders. Content: Recent advances in microbial DNA sequencing technologies have resulted i...
Article
Full-text available
Recent explorations of the human gut microbiota suggest that perturbations of microbial communities may increase predisposition to different disease phenotypes. Dietary nutrients may be converted into metabolites by intestinal microbes that serve as biologically active molecules affecting regulatory functions in the host. Probiotics may restore the...
Article
Full-text available
Beneficial microbes and probiotic species, such as Lactobacillus reuteri, produce biologically active compounds that can modulate host mucosal immunity. Previously, immunomodulatory factors secreted by L. reuteri ATCC PTA 6475 were unknown. A combined metabolomics and bacterial genetics strategy was utilized to identify small compound(s) produced b...
Data
Triple quadrupole mass spectrometry standard curve. Standard curve generated from deuterated histamine and used for the triple quadrupole MS quantification of histamine in HILIC-HPLC fractions and bacterial culture supernatant. Each sample was spiked with deuterated histamine as an internal standard. (TIF)
Data
THP-1 cells express the H1 and H2 receptors. Unstimulated THP-1 cells were examined for cell surface expression of the histamine H1 and H2 receptors. Cells were labeled with rabbit anti-human H1R or H2R pAb and FITC-conjugated goat anti-rabbit IgG pAb or FITC-conjugated goat anti-rabbit IgG pAb alone (IgG Control) and analyzed with FACS. Shown is o...
Data
Elevated cAMP inhibited TNF production from activated human monocytoid cells. Treatment of TLR2-stimulated THP-1 cells with a synthetic analog of cAMP, dcAMP, was sufficient to inhibit TNF production. Results represent the mean ± SD (n = 3), *p value<0.05 compared to medium control. (TIF)
Data
TNF-inhibitory phenotype was modified by the carbon source in the growth medium. Supplementing the growth medium with various simple sugars, such as glucose, glucose+fructose, and sucrose, altered the ability of TFA-treated cell pellets (CP) from L. reuteri 6475 to inhibit TNF production. Results represent the mean ± SD (n = 3), *p value<0.05 compa...
Data
A complete histidine decarboxylase gene cluster was found only in lactobacilli. Analysis of the HMP reference genomes (GI bacteria) for histidine decarboxylase gene homologs revealed that out of 349 reference genomes, only four bacterial strains contained the complete histidine decarboxylase gene cluster. The strains were L. reuteri JCM 112, L. reu...
Data
Genes in the histidine decarboxylase gene cluster were necessary for production of histamine. A. Quantitative real-time PCR demonstrated increased expression of all three hdc genes, hdcA, hdcB, and hdcP, when L. reuteri 6475 was grown in LDMIIIG medium supplemented with 4 mg/mL L-histidine compared to unsupplemented LDMIIIG. Gene expression data we...
Data
Inhibition of ERK1/2 activation suppressed TNF production from activated human monocytoid cells. Inhibition of the MEK/ERK signaling pathway with a MEK-specific inhibitor, U0126, was sufficient to block TNF production. Results represent the mean ± SD (n = 3), *p value<0.05 compared to RPMI medium control, #p value<0.05 compared to LDMIIIG medium co...
Data
TNF-inhibitory compounds were isolated in three distinct HILIC-HPLC fractions. Compounds from TFA-treated L. reuteri cell pellets were separated based on relative hydrophobicity. A. TNF-inhibitory compounds from L. reuteri 6475 grown in a glucose-containing medium were isolated in 3 fractions (B3, B5, and B6). Results represent the mean ± SD (n = 3...
Data
Pixel density analysis of MEK1/2 and ERK1/2 immunoblots. Immunoblots of MEK1/2 and ERK1/2 were quantified by pixel density analysis. A. MEK1/2. Results represent the mean ± SEM (n = 3), *p value<0.05 compared to medium control. B. ERK1/2. Results represent the mean ± SEM (n = 3), *p value<0.05 compared to medium control, #p value<0.05 compared to L...

Questions

Questions (2)
Question
Hi all. We performed HRM analysis on a LightCycler 480, but our Roche software doesn't have the Gene Scanning module enabled. We are not capable of purchasing a $5000 software right now and would like to know if any of you know of a software that would be able to help analyse high-res data in the meantime. We're pretty desperate! Thank you so much in advance!
Question
We are working with a species of Lactobacillus that is difficult to manipulate genetically. A mutant in a gene was made and we are trying to rescue the change in phenotype using complementation. We tried several expression vectors and none of them worked well in terms of level of gene expression. I was wondering if there is another way besides complementation to rule out polar effect and confirm that the change in phenotype is a result of a mutation in bacteria.

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