Hospital-acquired Isolates Research Articles

Characterization and genetic analysis of extensively drug-resistant hospital acquired Pseudomonas aeruginosa isolates

BackgroundThe incidence of hospital-acquired infections in extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) has been increasing worldwide and is frequently associated with an increase in mortality and morbidity rates. The aim of this study was to characterize clinical XDR-PA isolates recovered during six months at three different hospitals in Egypt.ResultsSeventy hospital-acquired clinical isolates of P. aeruginosa were classified into multidrug-resistant (MDR), extensively drug-resistant (XDR) and pandrug-resistant (PDR), according to their antimicrobial resistance profile. In addition, the possession of genes associated with mobile genetic elements and genes encoding antimicrobial resistance determinants among isolates were detected using polymerase chain reaction. As a result, a significant percentage of the isolates (75.7%) were XDR, while 18.5% were MDR, however only 5.7% of the isolates were non-MDR. The phenotypic detection of carbapenemases, extended-spectrum β-lactamases (ESBLs) and metallo β-lactamase (MBL) enzymes showed that 73.6% of XDR-PA isolates were carbapenemases producers, whereas 75.5% and 88.7% of XDR-PA isolates produced ESBLs and MBL respectively. In addition, PCR screening showed that oxa gene was the most frequently detected gene of carbapenemases (91.4%), while aac(6ʹ)-lb gene was mostly detected (84.3%) among the screened aminoglycosides-resistance genes. Furthermore, the molecular detection of the colistin resistance gene showed that 12.9% of isolates harbored mcr-1 gene. Concerning mobile genetic element markers (intI, traA, tnp513, and merA), intI was the highest detected gene as it was amplified in 67 isolates (95.7%). Finally, phylogenetic and molecular typing of the isolates via ERIC-PCR analysis revealed 10 different ERIC fingerprints.ConclusionThe present study revealed a high prevalence of XDR-PA in hospital settings which were resistant to a variety of antibiotics due to several mechanisms. In addition, 98% of the XDR-PA clinical isolates contained at least one gene associated with movable genetic elements, which could have aided the evolution of these XDR-PA strains. To reduce spread of drug resistance, judicious use of antimicrobial agents and strict infection control measures are therefore essential.

Integron distribution and relationship to antimicrobial resistance in E. coli isolated from blood culture

PurposeThe aim of this study was to evaluate the distribution of integrons in strains of E. coli isolated from blood culture and the relationship between integrons and antimicrobial resistance. MethodsThe study included 100 E. coli strains sent to the Medical Microbiology Laboratory from different clinics between September 2022 and June 2023. Antibiotic susceptibility was evaluated according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST). The presence of integrons was determined by the inhouse polymerase chain reaction (PCR). ResultsIntegron positivity was detected in 45 (45%) of isolates, and class 1 integrons were found in 41 (41%), class 2 integrons in 2 (2%), and both class 1 integrons and class 2 integrons in 2 (2%). Class 3 integron positivity was not detected. In total, 63 cases of community origin and 37 cases of hospital origin were identified. When antibiotic resistance was evaluated, the highest sensitivity was noted for amikacin (1%), meropenem (5%), imipenem (6%), and the highest resistant antibiotics were ampicillin (82%), cepfuroxime sodium (65%), and amoxicillin/clavulanate (62%), respectively. Of the 16 antimicrobial substances evaluated, 10 had an antibiotic resistance rate of over 45%. In class 1 integron-positive samples, ampicillin resistance and trimethoprim/sulfamethoxazole resistance were higher than in negative samples (p = 0.02, p = 0.0001, respectively). Fifty-one (51%) samples were found to have multiple drug resistance (MDR). In total, 59.5% of hospital-acquired isolates and 46% of community-acquired isolates were considered to be MDR. The class 1 integron positivity in MDR samples was high (p = 0.038). ConclusionThe high MDR rates in both hospital-acquired and community-acquired isolates are alarming. In particular, class 1 integron monitoring is very important to prevent the spread of MDR isolates.

Molecular Characteristics of Community-Acquired Methicillin-Resistant Staphylococcus aureus, Hospital-Acquired MRSA Isolates, and PVL in one of the Indian hospitals

Molecular Characteristics of Community-Acquired Methicillin-Resistant Staphylococcus aureus, Hospital-Acquired MRSA Isolates, and PVL in one of the Indian hospitals

Recombination-mediated dissemination of Methicillin-resistant S. aureus clonal complex 1 in the Egyptian health care settings

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is a rapidly evolving pathogen that is frequently associated with outbreaks and sustained epidemics. This study investigated the population structure, resistome, virulome, and the correlation between antimicrobial resistance determinants with phenotypic resistance profiles of 36 representative hospital-acquired MRSA isolates recovered from hospital settings in Egypt.ResultsThe community-acquired MRSA lineage, clonal complex 1 (CC1) was the most frequently detected clone, followed by three other globally disseminated clones, CC121, CC8, and CC22. Most isolates carried SCCmec type V and more than half of isolates demonstrated multi-drug resistant phenotypes. Resistance to linezolid, a last resort antibiotic for treating multidrug resistant MRSA, was observed in 11.11% of the isolates belonging to different genetic backgrounds. Virulome analysis indicated that most isolates harboured a large pool of virulence factors and toxins. Genes encoding aureolysin, gamma hemolysins, and serine proteases were the most frequently detected virulence encoding genes. CC1 was observed to have a high pool of AMR resistance determinants including cfr, qacA, and qacB genes, which are involved in linezolid and quaternary ammonium compounds resistance, as well as high content of virulence-related genes, including both of the PVL toxin genes. Molecular clock analysis revealed that CC1 had the greatest frequency of recombination (compared to mutation) among the four major clones, supporting the role of horizontal gene transfer in modulating AMR and hypervirulence in this clone.ConclusionsThis pilot study provided evidence on the dissemination success of CA-MRSA clone CC1 among Egyptian hospitals. Co-detection of multiple AMR and virulence genes in this lineage pose a broad public health risk, with implications for successful treatment. The results of this study, together with other surveillance studies in Egypt, should be used to develop strategies for controlling MRSA infections in Egyptian health-care settings.

Phenotypic and Genotypic Characterization of Macrolide, Lincosamide and Streptogramin B Resistance among Clinical Methicillin-Resistant Staphylococcus aureus Isolates in Chile.

Macrolides, lincosamides, and type B streptogramins (MLSB) are important therapeutic options to treat methicillin-resistant Staphylococcus aureus (MRSA) infections; however, resistance to these antibiotics has been emerging. In Chile, data on the MLSB resistance phenotypes are scarce in both community-(CA) and hospital-acquired (HA) MRSA isolates. Antimicrobial susceptibility to MLSB was determined for sixty-eight non-repetitive isolates of each HA-(32) and CA-MRSA (36). Detection of SCCmec elements, ermA, ermB, ermC, and msrA genes was performed by PCR. The predominant clones were SCCmec I-ST5 (HA-MRSA) and type IVc-ST8 (CA-MRSA). Most of the HA-MRSA isolates (97%) showed resistance to clindamycin, erythromycin, azithromycin, and clarithromycin. Among CA-MRSA isolates, 28% were resistant to erythromycin, azithromycin, and 25% to clarithromycin. All isolates were susceptible to linezolid, vancomycin, daptomycin and trimethoprim/sulfamethoxazole, and over 97% to rifampicin. The ermA gene was amplified in 88% of HA-MRSA and 17% of CA-MRSA isolates (p < 0.001). The ermC gene was detected in 6% of HA-SARM and none of CA-SARM isolates, whereas the msrA gene was only amplified in 22% of CA-MRSA (p < 0.005). Our results demonstrate the prevalence of the cMLSB resistance phenotype in all HA-MRSA isolates in Chile, with the ermA being the predominant gene identified among these isolates.

Human enterococcal isolates as reservoirs for macrolide-lincosamide-streptogramin and other resistance genes.

According to recent studies, the importance of MLS (macrolide-lincosamide-streptogramin) resistance phenotypes and genes in enterococci are reflected in the fact that they represent reservoirs of MLS resistance genes. The aim of this study was to investigate distribution of MLS resistance genes and phenotypes in community- and hospital-acquired enterococcal isolates and to determine their prevalence. The MLS resistance phenotypes (cMLSb, iMLSb, M/MSb, and L/LSa) were determined in 245 enterococcal isolates were characterized using the double-disc diffusion method. Specific primers were chosen from database sequences for detection of the MLS resistance genes (ermA, ermB, ermC, msrA/B, lnuA, lnuB, and lsaA) in 60 isolates of enterococci by end-point PCR. There was no linezolid-resistant enterococcal isolate. Only one vancomycin-resistant (0.6%) isolate was found and it occurred in a community-acquired enterococcal isolate. The most frequent MLS resistance phenotype among enterococcal isolates was cMLSb (79.7% community- and 67.9% hospital-acquired). The most common identified MLS resistance genes among enterococcal isolates were lsaA (52.9% community- and 33.3% hospital-acquired) and ermB (17.6% community- and 33.3% hospital-acquired). The most prevalent MLS gene combination was lnuA + lsaA (five enterococcal isolates). The ermB gene encoded cMLSb phenotype, and it was identified in only one isolate that displayed iMLSb resistance phenotype. Based on the results obtained, we can conclude that the most frequent MLS resistance phenotype among enterococcal isolates was cMLSb. Surprisingly, a vancomycin-resistant enterococcal isolate was identified in a community-acquired enterococcal isolate. This study shows that enterococci may represent a major reservoir of ermB, lsaA, and lnuA genes.

1264. In Vitro Activity of Ceftazidime-Avibactam and Comparator Agents Against Enterobacterales and Pseudomonas aeruginosa Collected &amp;lt; 48 Hours and ≥48 Hours Post-Admission from Pediatric Patients, ATLAS Surveillance Program 2016-2019

BackgroundCeftazidime-avibactam (CAZ-AVI) is a β-lactam/non-β-lactam β-lactamase inhibitor combination with in vitro activity against Enterobacterales (Ent) and Pseudomonas aeruginosa (Psa) carrying Class A, C and some Class D β-lactamases. We examined the in vitro activity of CAZ-AVI and comparators against presumed community-acquired (CA; cultured < 48 h after hospital admission) and hospital-acquired (HA; cultured ≥48 h post-admission) isolates collected from pediatric patients as part of the ATLAS surveillance program.Methods6654 non-duplicate isolates were collected in 52 countries in Europe (n=3423), Latin America (n=1323), Middle East/Africa (n=1177), and Asia/Pacific (excluding China; n=731) from patients (newborn to 17 y) with lower respiratory tract (LRTI; n=1687), urinary tract (UTI; n=1631), bloodstream (BSI; n=1149), skin and soft tissue (SSTI; n=1122), and intra-abdominal (IAI; n=981) infections. Susceptibility testing was performed by CLSI broth microdilution and values were interpreted using CLSI 2021 breakpoints. CAZ-AVI was tested at a fixed concentration of 4 µg/mL AVI. Isolates with CAZ or aztreonam MICs ≥2 µg/mL (Escherichia coli, Klebsiella spp., Proteus mirabilis) or meropenem MICs ≥2 µg/mL (all Ent species) or ≥4 µg/mL (Psa) were screened for β-lactamase genes.ResultsThe in vitro activity of CAZ-AVI exceeded that of meropenem and other tested β-lactams against Ent (97.8% susceptible (S)) and Psa (92.1% S) collected globally from pediatric patients (Table). Percentages of susceptibility to CAZ-AVI ranged from 95.4-99.2% among CA Ent from different infection types and were reduced 0.6-1.3% among HA isolates from LRTI, UTI, SSTI, and IAI. Susceptibility to CAZ-AVI was also similar (92.6-95.8% S) among CA Psa from different infection types and was reduced 1.2-7.0% among HA isolates. Larger differences in susceptibility were typically seen for the tested comparator β-lactams. For Ent, the lowest percentages of susceptibility to the tested β-lactams were observed among isolates from BSI, while the pattern was less clear for Psa.Results Table ConclusionCAZ-AVI could provide a valuable therapeutic option for treatment of CA and HA infections caused by Ent and Psa in pediatric patients.Disclosures Krystyna Kazmierczak, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Sibylle Lob, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Gregory Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)

Impact of antibiotic usage on extended-spectrum \u03b2-lactamase producing Escherichia coli prevalence

An increase in antibiotic usage is considered to contribute to the emergence of antimicrobial resistance. Although experts are counting on the antimicrobial stewardship programs to reduce antibiotic usage, their effect remains uncertain. In this study, we aimed to evaluate the impact of antibiotic usage and forecast the prevalence of hospital-acquired extended spectrum β-lactamase (ESBL)—producing Escherichia coli (E. coli) using time-series analysis. Antimicrobial culture information of E. coli was obtained using a text processing technique that helped extract free-text electronic health records from standardized data. The antimicrobial use density (AUD) of antibiotics of interest was used to estimate the quarterly antibiotic usage. Transfer function model was applied to forecast relationship between antibiotic usage and ESBL-producing E. coli. Of the 1938 hospital-acquired isolates, 831 isolates (42.9%) were ESBL-producing E. coli. Both the proportion of ESBL-producing E. coli and AUD increased over time. The transfer model predicted that ciprofloxacin AUD is related to the proportion of ESBL-producing E. coli two quarters later. In conclusion, excessive use of antibiotics was shown to affect the prevalence of resistant organisms in the future. Therefore, the control of antibiotics with antimicrobial stewardship programs should be considered to restrict antimicrobial resistance.

1568. In Vitro Activity of Ceftazidime-Avibactam and Comparator Agents Against Enterobacterales and Pseudomonas aeruginosa Collected &amp;lt; 48 Hours and ≥48 Hours Post-Admission from Pediatric Patients, ATLAS Surveillance Program 2015-2018

BackgroundCeftazidime-avibactam (CAZ-AVI) is a β-lactam/non-β-lactam β-lactamase inhibitor combination with in vitro activity against Enterobacterales (Ent) and Pseudomonas aeruginosa (Psa) carrying Class A, C and some Class D β-lactamases. We examined the in vitro activity of CAZ-AVI and comparators against presumed community-acquired (CA; cultured < 48 h after hospital admission) and hospital-acquired (HA; cultured ≥48 h post-admission) isolates collected from pediatric patients as part of the ATLAS surveillance program.Methods6023 non-duplicate isolates were collected in 50 countries in Europe (n=3122), Latin America (n=1220), Middle East/Africa (n=1007), and Asia/Pacific (excluding China; n=674) from patients (newborn to 17 y) with lower respiratory tract (LRTI; n=1641), urinary tract (UTI; n=1595), skin and soft tissue (SSTI; n=1027), intra-abdominal (IAI; n=949), and bloodstream (BSI; n=811) infections. Susceptibility testing was performed by CLSI broth microdilution and values were interpreted using CLSI 2020 breakpoints. CAZ-AVI was tested at a fixed concentration of 4 µg/mL AVI. Isolates with CAZ or aztreonam MICs ≥2 µg/mL (Escherichia coli, Klebsiella spp., Proteus mirabilis) or meropenem MICs ≥2 µg/mL (all Ent species) or ≥4 µg/mL (Psa) were screened for β-lactamase genes.ResultsThe in vitro activity of CAZ-AVI exceeded that of meropenem and other tested β-lactams against Ent (98.5% susceptible (S)) and Psa (93.1% S) collected globally from pediatric patients (Table). Percentages of susceptibility to CAZ-AVI ranged from 96.8-99.3% among CA Ent from different infection types and were reduced 0.4-1.0% among HA isolates from SSTI, IAI and BSI. Susceptibility to CAZ-AVI was also similar (92.7-95.4% S) among CA Psa from different infection types and was reduced 0.1-4.4% among HA isolates. For both Ent and Psa, the lowest percentages of susceptibility to the tested β-lactams were observed among isolates from BSI, which included a higher proportion of isolates carrying extended-spectrum β-lactamases and/or carbapenemases than isolates from other infection types.Table ConclusionCAZ-AVI could provide a valuable therapeutic option for treatment of CA and HA infections caused by Ent and Psa in pediatric patients.DisclosuresKrystyna Kazmierczak, PhD, IHMA (Employee)Pfizer, Inc. (Consultant) Greg Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor)

CRISPR-cas system in the acquisition of virulence genes in dental-root canal and hospital-acquired isolates of Enterococcus faecalis

ABSTRACT Enterococcus faecalis is one of the important causative agents of nosocomial and life-threatening infections in human. Several studies have demonstrated that the presence of CRISPR-cas is associated with antibiotic susceptibility and lack of virulence traits. In this study, we aimed to assess the phenotypic and genotypic virulence determinants in relation to CRISPR elements from the dental-root canals and hospital-acquired isolates of E. faecalis. Eighty-eight hospital-acquired and 73 dental-root canal isolates of E. faecalis were assessed in this study. Phenotypic screening of the isolates included biofilm formation, and gelatinase and hemolysis activities. Genotypical screening using PCR was further used to evaluate the presence of CRISPR elements and different virulence-associated genes such as efaA, esp, cylA, hyl, gelE, ace, ebpR, and asa1. Biofilm formation, gelatinase, and hemolysis activities were detected in 93.8%, 29.2%, and 19.2% of the isolates, respectively. The most prevalent virulence-associated gene was ace, which was followed by efaA, whereas cylA was the least identified. The presence of CRISPR1-cas, orphan CRISPR2, and CRISPR3-cas was determined in 13%, 55.3%, and 17.4% of the isolates, respectively. CRISPR elements were significantly more prevalent in the dental-root canal isolates. An inverse significant correlation was found between CRISPR-cas loci, esp, and gelE, while direct correlations were observed in the case of cylA, hyl, gelE (among CRISPR-loci 1 and 3), asa1, ace, biofilm formation, and hemolysis activity. Findings, therefore, indicate that CRISPR-cas might prevent the acquisition of some respective pathogenicity factors in some isolates, though not all; so selective forces could not influence pathogenic traits. Abbreviations: BHI: brain-heart infusion agar; CRISPRs: Clustered regularly interspaced short palindromic repeats; Esp: Cell wall-associated protein; ENT: ear-nose-throat; ICU: intensive care units; OD: optical densities; PCR: polymerase chain reaction; SDS: sodium dodecyl sulfate; UTI: urinary tract infection

Epidemiologic and Molecular Characteristics of Staphylococcus aureus Strains Isolated From Hospitalized Pediatric Patients.

We aimed to determine molecular characteristics of Staphylococcus aureus isolates cultured from hospitalized pediatric patients. All accessible S. aureus isolates cultured from hospitalized pediatric patients were analyzed for staphylococcal cassette chromosome mec (SCCmec) types, Panton-Valentine Leukocidin (PVL) encoding genes and antibiotic resistance patterns. A total of 132 S. aureus isolates, 102 methicillin-susceptible S. aureus (MSSA) (81.8%), 30 methicillin-resistant S. aureus (MRSA) (18.2%) were included in the study. Sixty of 132 (45.5%) S. aureus isolates were cultured from skin and soft tissue infections (SSTIs), 50 (37.9%) from bloodstream infections, 11 (8.3%) from bone infections and 11 (8.3%) from other sterile sites. Fifty-three of 102 (52%) MSSA isolates were cultured from SSTI, 35 (34.3%) from bloodstream infections, 7 (6.9%) from bone infections and 7 (6.9%) from other sterile sites (P = 0.083). Fifteen MRSA isolates (50%) were cultured from blood culture, 7 from (23.3%) SSTI, 4 (13.3%) from bone infections and 4 from (13.3%) other sterile sites. Nine PVL gene harboring S. aureus isolates were isolated from SSTI (75%), 2 from blood culture (16.7%) and 1 from other sterile site (8.3%). Three MRSA (6.7%) isolates were found to be positive for SCCmec type III and 16 MRSA isolates (53.3%) were found to be positive for SCCmec type IV. Three MRSA isolates harboring SCCmec type III was isolated from blood culture, 11 of 16 MRSA isolates harboring SCCmec type IV was isolated from blood culture, 3 isolates were isolated from bone infections and 2 isolates were isolated from SSTI (P < 0.001). Five of 72 (6.9%) hospital-acquired S. aureus isolates and 7 of 60 (11.7%) community-acquired S. aureus isolates were PVL gene positive. Twenty-two of 72 (30.6%) hospital-acquired S. aureus infections and 8 of 60 (13.3%) community-acquired S. aureus isolates were MRSA (P = 0.015). All of the 3 SCCmec III harboring MRSA isolates and 11 of 16 SCCmec IV carrying MRSA isolates were hospital acquired. Hospitalization in the past 1 year was found to increase MRSA infections 3.95 times (P = 0.038, 95% confidence interval: 1.078-14.48). As distribution of virulence genes differs among S. aureus isolates from different regions, it is necessary to monitor the emergence of genes encoding PVL, SCCmec in both MRSA and MSSA throughout the world. Our results show a high prevalence of PVL in community-onset S. aureus infections in children. SCCmec type IV was more commonly isolated in hospital-acquired MRSA isolates, and PVL gene was more commonly isolated in community-acquired S. aureus infections.

Discordance of vancomycin minimum inhibitory concentration for methicillin-resistant Staphylococcus aureus at 2μg/mL between Vitek II, E-test, and Broth Microdilution.

BackgroundVancomycin, the first line antibiotic for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, is often administered inappropriately when MIC is greater than 2 µg/mL, including ‘susceptible’ strains. This study assessed the discordance of vancomycin minimum inhibitory concentration (MIC) for methicillin-resistant Staphylococcus aureus (MRSA).MethodsIn total, 229 MRSA isolates from blood cultures collected between 2009 and 2015 at a tertiary hospital in Taiwan were examined. The MICs of vancomycin were measured using Vitek 2, E-test, and standard broth microdilution at the level of 2 µg/mL.ResultsThe geometric mean of the MICs of hospital-acquired MRSA was higher than that of community-acquired MRSA (P < 0.001), with the exact agreement rates (with broth microdilution) at 2 µg/mL being 53.6% in Vitek 2 and 86.7% in E-test. Overall, E-test (98.1%) had more categorical accordance than did Vitek 2 (94.0%; P = 0.026). Vitek 2 had a tendency to overestimate MRSA in high-MIC isolates, whereas E-test inclined underestimation in low-MIC isolates. Surprisingly, the discordance rates of MRSA vancomycin MICs were higher in hospital-acquired isolates (13.3%–17.0%) than in community-acquired isolates (6.2%–7.0%).ConclusionThe Infectious Diseases Society of America recommends the use of alternative antimicrobial agents when vancomycin MIC is ≥ 2 µg/mL; in this study, only 53.6% of the isolates tested using Vitek 2 showed a high MIC in the broth microdilution method. Accurate identification of the resistance profile is a key component of antimicrobial stewardship programs. Therefore, to reduce inappropriate antibiotic use and mitigate the emergence of resistant strains, we recommend using complementary tests such as E-test or Broth microdilution to verify the MIC before administering second-line antibiotics.Strengths(1) We compared the categorical agreement between different methods measuring MRSA MICs level. (2) Physicians should incorporate this information and consider a complementary test to verify the appropriateness of the decision of shifting vancomycin to second-line antibiotic treatment to improve patients’ prognosis. (3) MRSA-vancomycin MICs at a cutoff of 2 µg/mL obtained using Vitek II exhibited a higher sensitivity level and negative predictive value than those obtained using E-test in the prediction of categorical agreement with standard broth microdilution.Limitation(1) Our research was based on a single hospital-based study. (2) The MRSA strains in this study were stored for more than 12 months after isolation. (3) We did not collect information on clinical prognosis.

Multiple Drug Resistance Patterns in Various Phylogenetic Groups of Hospital-Acquired Uropathogenic E. coli Isolated from Cancer Patients

Cancer patients are more susceptible to several bacterial infections, particularly urinary tract infections caused by uropathogenic E. coli (UPEC). The objective of this work was detection and the phylogenetic characterization of hospital-acquired isolates of uropathogenic E. coli in cancer patients and the determination of its relation with antibiotic resistance. A total of 110 uropathogenic E. coli responsible for hospital-acquired urinary tract infections in cancer patients were included in this study. A triplex PCR was employed to segregate different isolates into four different phylogenetic groups (A, B1, B2 and D). Drug resistance was evaluated by the disc diffusion method. All of the isolates were multiple drug-resistant (MDR) and 38.18% of all UPEC isolates were extended-spectrum beta-lactamase (ESBL) producers from which 52% were positive for the blaCTX-M gene, 40% for the blaTEM gene, and 17% for the blaSHVgene. Among 42 ESBL-producing uropathogenic E. coli isolates, the majority belonged to phylogenetic group B2 (43%), followed by group D (36%), group A (19%) and group B1 (2%). Our results have shown the emergence of MDR isolates among uropathogenic E. coli with the dominance of phylogenetic group B2. Groups A and B1 were relatively less common. The most effective drug in all phylogenetic groups was imipenem.

185. Clinical Characterization of Staphylococcus aureus Bacteremia in Children at an Inner-City Community Hospital

Background Staphylococcus aureus bacteremia (SAB) is associated with high morbidity and mortality rates. Data on epidemiology and outcomes of SAB in children is not as well described as in adults. The primary objective of this study was to describe clinical and microbiological cure rates of SAB in hospitalized children. Secondary objectives included time to clinical and microbiological cure, mortality, proportions of methicillin-sensitive and resistant SA (MSSA, MRSA) bacteremia, and antibiotic usage pattern.MethodsThis was an electronic chart abstraction conducted at a community hospital in the South Bronx, NY, of all pediatric cases of SAB (<21 years of age) from January 1, 2010 to March 30, 2017. Demographic, clinical and microbiological data along with risk factors for bacteremia were collected. Clinical cure was defined as resolution of acute symptoms and signs of SAB and microbiological cure was defined as documentation of first negative blood culture after initiation of treatment. Standard definitions were used for hospital-acquired (HA) and community-acquired (CA) isolates of SA.ResultsOf 41 patients, neonates comprised 12%, 1- to 23-month-old infants 56% and 2- to 17-year-olds 31%. Overall, 76% of patients had bacteremia due to MSSA, and 24% MRSA. MRSA was isolated in 37% of HA SAB compared with 14% of CA SAB (P = 0.15). The two highest risk factors identified for SAB were peripherally inserted central catheters lines (PICC, 29%) and skin and soft-tissue infections (22%). SAB in the neonatal period was associated with PICC lines when compared with children outside the neonatal period (80% vs. 22%, P = 0.02). Using available data, clinical and microbiological cure rates were similar at 73%. The median time to clinical cure was 5 days (interquartile range [IQR] 2–10) and to microbiological cure, 2 days (IQR 1–4). A 2-month-old infant died (mortality 2.4%). Initial antibiotic selection was vancomycin (39%), clindamycin (39%), and nafcillin (7%). The proportion of SA resistant to clindamycin was 22%.ConclusionPediatric SAB was uncommon in this community hospital experience over 7 years and is associated with PICC lines in neonates. MSSA was more prevalent than MRSA. Initial antibiotic selection had anti-staphylococcal coverage in 85% of cases, while clindamycin resistance occurred in 22% of SA isolates.Disclosures All authors: No reported disclosures.

The potential of fosfomycin for multi-drug resistant sepsis: an analysis of in vitro activity against invasive paediatric Gram-negative bacteria.

Antimicrobial resistance (AMR) is of increasing global concern, threatening to undermine recent progress in reducing child and neonatal mortality. Repurposing older antimicrobials is a prominent strategy to combat multidrug-resistant sepsis. A potential agent is fosfomycin, however, there is scarce data regarding its in vitro activity and pharmacokinetics in the paediatric population. We analysed a contemporary, systematically collected archive of community-acquired (CA) and hospital-acquired (HA) paediatric Gram-negative bacteraemia isolates for their susceptibility to fosfomcyin. MICs were determined using agar serial dilution methods and validated by disk diffusion testing where breakpoints are available. Disk diffusion antimicrobial susceptibility testing was also conducted for current empirical therapies (ampicillin, gentamicin, ceftriaxone) and amikacin (proposed in the literature as a new combination empirical therapeutic option). Fosfomycin was highly active against invasive Gram-negative isolates, including 90 % (202/224) of Enterobacteriaceae and 96 % (22/23) of Pseudomonas spp. Fosfomycin showed high sensitivity against both CA isolates (94 %, 142/151) and HA isolates (81 %, 78/96; P =0.0015). CA isolates were significantly more likely to be susceptible to fosfomycin than the current first-line empirical therapy (96 % vs 59 %, P <0.0001). Extended spectrum β-lactamases (ESBL) production was detected in 34 % (85/247) of isolates with no significant difference in fosfomycin susceptibility between ESBL-positive or -negative isolates [73/85 (86 %) vs 147/162 (91 %) respectively, P =0.245]. All isolates were susceptible to a fosfomycin-amikacin combination. Gram-negative paediatric bacteraemia isolates are highly susceptible to fosfomycin, which could be combined with aminoglycosides as a new, carbapenem-sparing regimen to achieve excellent coverage to treat antimicrobial-resistant neonatal and paediatric sepsis.

Antimicrobial Resistance in Invasive Bacterial Infections in Hospitalized Children, Cambodia, 2007-2016.

To determine trends, mortality rates, and costs of antimicrobial resistance in invasive bacterial infections in hospitalized children, we analyzed data from Angkor Hospital for Children, Siem Reap, Cambodia, for 2007–2016. A total of 39,050 cultures yielded 1,341 target pathogens. Resistance rates were high; 82% each of Escherichia coli and Klebsiella pneumoniae isolates were multidrug resistant. Hospital-acquired isolates were more often resistant than community-acquired isolates; resistance trends over time were heterogeneous. K. pneumoniae isolates from neonates were more likely than those from nonneonates to be resistant to ampicillin–gentamicin and third-generation cephalosporins. In patients with community-acquired gram-negative bacteremia, third-generation cephalosporin resistance was associated with increased mortality rates, increased intensive care unit admissions, and 2.26-fold increased healthcare costs among survivors. High antimicrobial resistance in this setting is a threat to human life and the economy. In similar low-resource settings, our methods could be reproduced as a robust surveillance model for antimicrobial resistance.

Implementation of global antimicrobial resistance surveillance system (GLASS) in patients with bacteremia.

The global antimicrobial resistance surveillance system (GLASS) was launched by the World Health Organization (WHO) in 2015. GLASS is a surveillance system for clinical specimens that are sent to microbiology laboratory for clinical purposes. The unique feature of GLASS is that clinical data is combined with microbiological data, and deduplication of the microbiological results is performed. The objective of the study was to determine feasibility and benefit of GLASS for surveillance of blood culture specimens. GLASS was implemented at Siriraj Hospital in Bangkok, Thailand using a locally developed web application program (app) to transfer blood culture specimen data, and to enter clinical data of patients with positive blood culture by infection control nurses and physicians via the app installed in their smart phones. The rate of positive blood culture specimens with true infection was 15.2%. Escherichia coli was the most common cause of bacteremia. Secondary bacteremia, primary bacteremia, and central line-associated blood stream infection was observed in 61.8%, 30.6%, and 12.6% of cases, respectively. Sepsis was observed in 56.9% of patients. E.coli was significantly more common in community-acquired bacteremia, whereas Klebsiella pneumoniae, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Acinetobacter baumannii were significantly more common in hospital-acquired bacteremia. Hospital-acquired isolates of E.coli, K.pneumoniae, A.baumannii, P.aeruginosa, S.aureus and Enterococcus faecium were more resistant to antibiotics than community-acquired isolates. In-hospital mortality was significantly higher in patients with antibiotic-resistant bacteremia than in patients with antibiotic non-resistant bacteremia (40.5% vs. 28.5%, p<0.001). The patients with antibiotic-resistant bacteremia consumed more resources than those with antibiotic non-resistant bacteremia. Blood culture results combined with patient clinical data were shown to have more benefit for surveillance of antimicrobial resistance, and to be more applicable for developing local antibiotic treatment guidelines for patients suspected of having bacteremia. However, GLASS consumed more time and more resources than the conventional laboratory-based surveillance system.

Prevalence of Genotypes That Determine Resistance of Staphylococci to Macrolides and Lincosamides in Serbia.

Macrolides, lincosamides, and streptogramins (MLS) resistance genes are responsible for resistance to these antibiotics in Staphylococcus infections. The purpose of the study was to analyze the distribution of the MLS resistance genes in community- and hospital-acquired Staphylococcus isolates. The MLS resistance phenotypes [constitutive resistance to macrolide–lincosamide–streptogramin B (cMLSb), inducible resistance to macrolide–lincosamide–streptogramin B (iMLSb), resistance to macrolide/macrolide–streptogramin B (M/MSb), and resistance to lincosamide–streptogramin A/streptogramin B (LSa/b)] were determined by double-disc diffusion method. The presence of the MLS resistance genes (ermA, ermB, ermC, msrA/B, lnuA, lnuB, and lsaA) were determined by end-point polymerase chain reaction in 179 isolates of staphylococci collected during 1-year period at the Center for Microbiology of Public Health Institute in Vranje. The most frequent MLS phenotype among staphylococcal isolates, both community-acquired and hospital-acquired, was iMLSb (33.4%). The second most frequent was M/MSb (17.6%) with statistically significantly higher number of hospital-acquired staphylococcal isolates (p < 0.05). MLS resistance was mostly determined by the presence of msrA/B (35.0%) and ermC (20.8%) genes. Examined phenotypes were mostly determined by the presence of one gene, especially by msrA/B (26.3%) and ermC (14.5%), but 15.6% was determined by a combination of two or more genes. M/MSb phenotype was the most frequently encoded by msrA/B (95.6%) gene, LSa/b phenotype by lnuA (56.3%) gene, and iMLSb phenotype by ermC (29.4%) and ermA (25.5%) genes. Although cMLSb phenotype was mostly determined by the presence of ermC (28.9%), combinations of two or more genes have been present too. This pattern was particularly recorded in methicillin-resistant Staphylococcus aureus (MRSA) (58.3%) and methicillin-resistant coagulase-negative staphylococci (MRCNS) (90.9%) isolates with cMLSB phenotype. The msrA/B gene and M/MSb phenotype were statistically significantly higher in hospital-acquired than community-acquired staphylococci strains (p < 0.05). There are no statistically significant differences between staphylococci harboring the rest of MLS resistance genes acquired in community and hospital settings (p > 0.05). The prevalence of iMLSb phenotypes may change over time, so it is necessary to perform periodic survey of MLS resistance phenotypes, particularly where the D-test is not performed routinely.

Antimicrobial resistance profile and molecular characterization of methicillin-resistant staphylococcus isolates in Tripoli Central Hospital, Libya

Abstract Background: Nosocomial infections caused by methicillin-resistant Staphylococci could lead to increased morbidity and mortality, but little is known about the prevalence of infections with these organisms in healthcare facilities and in the community in Tripoli. This study investigated the in vitro susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase negative staphylococci (MRCNS) to antimicrobial agents, and determined the molecular characteristics of MRSA. Methods: This is a retrospective observational study aiming at determining the prevalence and antibiotic resistance pattern of (MRSA) and (MRCNS) isolated from non-duplicated clinical specimens in Tripoli Central Hospital (TCH) between June 2013 and June 2014. Isolates were identified using standard laboratory procedures. Antimicrobial susceptibility tests were carried out by disk diffusion method and automated systems. DNA of the MRSA isolates was used for PCR to determine the molecular analysis. Results: 218 isolates of Staphylococci were obtained, 71.6% were coagulase positive staphylococci (CPS) and 28.4% were coagulase negative staphylococci (CNS). 39.7% of CPS were MRSA, while 75.8% of CNS were MRCNS. The rates of hospital-acquired MRSA (HA-MRSA) and community-acquired MRSA (CA-MRSA) among MRSA isolates were 61.3% and 38.7% respectively. A similar trend was detected among MRCNS isolates, where 74.5% were HA-MRCNS and 25.5% were CA-MRCNS. All the MRSA and MRCNS isolates were susceptible (100%) to vancomycin, tigecycline, linezolid, quinupristin/dalfopristin, daptomycin and moxifloxacin. Generally, hospital-acquired strains showed higher resistance rates than community-acquired ones to the most commonly tested non-beta-lactam antibiotics. 35.5% of all staphylococcal isolates exhibited mecA+ gene and 12.9% expressed mecC+. Meanwhile, 38.7% of MRSA isolates harbored both mecA and mecC. However, 12.9% of MSSA isolates were negative for both mecA and mecC. The mecA gene was detectable in 59.1% and 40.9 % of HA-MRSA and CA-MRSA isolates respectively. Conclusion: Hospital-acquired MRSA and MRCNS isolates had higher resistance rates to non-beta lactam antimicrobial drugs than the respective community-acquired isolates. This was shown by early detection of mecC gene among MRSA isolates.

Evaluation of tigecycline activity on wound isolates of methicillinresistant Staphylococcus aureus from hospital and communityacquired infections in Cross River State, Nigeria

Background/Objective: Tigecycline belongs to the glycylcycline class of antibiotics with in-vitroactivity against most gram-positive bacteria, including multidrug-resistant pathogens. Methicillin-resistant Staphylococcus aureus (MRSA) is one of such pathogen, which has been associated with community and hospital-acquired infections. Tigecycline is considered to be a newer treatment option for emerging multidrug-resistant bacteria. This study aims to determine the in-vitro activity of tigecycline against community and hospital-acquired MRSA isolated from infected traumatic wounds in Cross River State. Material and Methods: A total of 60 MRSA were isolated from wound samples, 30 each from the community and hospital settings. These were tested for tigecycline susceptibility by the E-test method. Detection of methicillin resistance was performed using cefoxitin (30µg) disk. All strains were identified according to standard bacteriological methods. Results: Of the 60 isolates, 55 (91.7%) were sensitive to tigecycline with MIC50 and MIC90 values of 0.25 and 0.5μg/ml, respectively. Twenty-seven (90.0%) of the 30 community-acquired isolates were susceptible to tigecycline, while 28 (93.3%) of the 30 hospital-acquired isolates were susceptible. Conclusions: Tigecycline showed excellent in-vitro activity against MRSA wound isolates and, therefore may be a drug of choice for empirical therapy of skin and soft tissue infections in areas where MRSA is prevalent.