The Effect of Varying Interval Definitions on the Prevalence of SARS-CoV-2 Reinfections: A Retrospective Cross-Sectional Cohort Study.

BACKGROUND: We assessed the SARS-CoV-2 reinfection rate in a large patient cohort, and evaluated the effect of varying time intervals between two positive tests on assumed reinfection rates using viral load data. METHODS: All positive SARS-CoV-2 samples collected between 1 March 2020 and 1 August 2021 from a laboratory in the region Kennemerland, the Netherlands, were included. The reinfection rate was analyzed using different time intervals between two positive tests varying between 2 and 16 weeks. SARS-CoV-2 PCR crossing point (Cp) values were used to estimate viral loads. RESULTS: In total, 679,513 samples were analyzed, of which 53,366 tests (7.9%) were SARS-CoV-2 positive. The number of reinfections varied between 260 (0.52%) for an interval of 2 weeks, 89 (0.19%) for 4 weeks, 52 (0.11%) for 8 weeks, and 37 (0.09%) for a minimum interval of 16 weeks between positive tests. The median Cp-value (IQR) in the second positive samples decreased when a longer interval was chosen, but stabilized from week 8 onwards. CONCLUSIONS: Although the calculated reinfection prevalence was relatively low (0.11% for the 8-week time interval), choosing a different minimum interval between two positive tests resulted in major differences in reinfection rates. As reinfection Cp-values stabilized after 8 weeks, we hypothesize this interval to best reflect novel infection rather than persistent shedding.

SARS-CoV-2 viral-load distribution reveals that viral loads increase with age: a retrospective cross-sectional cohort study.

BACKGROUND: Describing the SARS-CoV-2 viral-load distribution in different patient groups and age categories. METHODS: All results from first nasopharyngeal (NP) and oropharyngeal (OP) swabs from unique patients tested via SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) collected between 1 January and 1 December 2020 predominantly in the Public Health Services regions Kennemerland and Hollands Noorden, province of North Holland, the Netherlands, were included in this study. SARS-CoV-2 PCR crossing-point (Cp)-values were used to estimate viral loads. RESULTS: In total, 278 455 unique patients were tested, of whom 9.1% (n = 25.374) were SARS-CoV-2-positive. PCRs performed by Public Health Services (n = 211 914), in which sampling and inclusion were uniform, revealed a clear relation between age and SARS-CoV-2 viral load, with especially children aged <12 years showing lower viral loads than adults (ß: -0.03, 95% confidence interval: -0.03 to -0.02, p < 0.001), independently of sex and/or symptom duration. Interestingly, the median Cp-values between the >79- and <12-year-old populations differed by more than four PCR cycles, suggesting an ∼16-fold difference in viral load. In addition, the proportion of children aged <12 years with a low load (Cp-value >30) was higher compared with other patients (31.1% vs 17.2%, p-value < 0.001). CONCLUSIONS: In patients tested by Public Health Services, SARS-CoV-2 viral load increases with age. Further studies should elucidate whether the lower viral load in children is indeed related to their suggested limited role in SARS-CoV-2 transmission. Moreover, as rapid antigen tests are less sensitive than PCR, these results suggest that SARS-CoV-2 antigen tests have lower sensitivity in children than in adults.

Ceftibuten plus amoxicillin-clavulanic acid for oral treatment of urinary tract infections with ESBL producing E. coli and K. pneumoniae: a retrospective observational case-series.

This study aimed to evaluate the clinical and bacteriological effect of oral treatment with ceftibuten plus amoxicillin-clavulanic acid in patients with a urinary tract infection (UTI) caused by an extended-spectrum ß-lactamase (ESBL)-producing micro-organism. In this retrospective observational case-series, oral treatment with ceftibuten 400 mg QD plus amoxicillin-clavulanic acid 625 mg TID for 14 days was evaluated in ten patients with pyelonephritis caused by an ESBL-positive micro-organism resistant to ciprofloxacin and co-trimoxazole. Presence of ESBL genes was confirmed using PCR and micro-array. EUCAST breakpoints were used for susceptibility testing. Ten patients (five women) were evaluated in 2016 and 2017. Six patients were from outpatient hospital care, and four from primary care. Urinary cultures yielded seven E. coli and three K. pneumoniae ESBL-positive isolates. Using Vitek-2, all isolates were resistant to cefotaxime, and resistant (n = 7) or intermediately susceptible (n = 3) to ceftazidime. With disc diffusion, all isolates were susceptible to ceftibuten (zones 25-32 mm), while with MIC test strips eight of ten isolates were resistant to ceftibuten (MICs 0.5-4 mg/L). An amoxicillin-clavulanic acid disc next to the ceftibuten disc extended the ceftibuten zone by 2-8 mm. All patients experienced clinical cure. Bacteriological cure (absence of pretreatment micro-organism in the first follow-up culture obtained within 3 months after treatment) was observed in all eight patients with follow-up cultures. This case-series shows that the synergistic combination of ceftibuten plus amoxicillin-clavulanic acid may be an option for oral treatment of UTIs caused by ESBL producing E. coli or K. pneumoniae.

Susceptibility of ESBL Escherichia coli and Klebsiella pneumoniae to fosfomycin in the Netherlands and comparison of several testing methods including Etest, MIC test strip, Vitek2, Phoenix and disc diffusion.

Objectives: Fosfomycin susceptibility testing is complicated and prone to error. Before using fosfomycin widely in patients with serious infections, acquisition of WT distribution data and reliable susceptibility testing methods are crucial. In this study, the performance of five methods for fosfomycin testing in the routine laboratory against the reference method was evaluated. Methods: Ten laboratories collected up to 100 ESBL-producing isolates each (80 Escherichia coli and 20 Klebsiella pneumoniae). Isolates were tested using Etest, MIC test strip (MTS), Vitek2, Phoenix and disc diffusion. Agar dilution was performed as the reference method in a central laboratory. Epidemiological cut-off values (ECOFFs) were determined for each species and susceptibility and error rates were calculated. Results: In total, 775 E. coli and 201 K. pneumoniae isolates were tested by agar dilution. The ECOFF was 2 mg/L for E. coli and 64 mg/L for K. pneumoniae. Susceptibility rates based on the EUCAST breakpoint of ≤32 mg/L were 95.9% for E. coli and 87.6% for K. pneumoniae. Despite high categorical agreement rates for all methods, notably in E. coli, none of the alternative antimicrobial susceptibility testing methods performed satisfactorily. Due to poor detection of resistant isolates, very high error rates of 23.3% (Etest), 18.5% (MTS), 18.8% (Vitek2), 12.5% (Phoenix) and 12.9% (disc diffusion) for E. coli and 22.7% (Etest and MTS), 16.0% (Vitek2) and 12% (Phoenix) for K. pneumoniae were found. None of the methods adequately differentiated between WT and non-WT populations. Conclusions: Overall, it was concluded that none of the test methods is suitable as an alternative to agar dilution in the routine laboratory.

Rapid and accurate detection of carbapenemase genes in Enterobacteriaceae with the Cepheid Xpert Carba-R assay.

Rapid and accurate detection of carbapenemase-producing Enterobacteriaceae is pivotal for adequate antibiotic therapy and infection control. The Cepheid Xpert Carba-R assay detects and identifies the most prevalent carbapenemases (KPC, VIM, IMP, NDM and OXA-48), using automated real-time PCR. The test performance of the Xpert Carba-R was evaluated with 129 well-characterized non-repeat Enterobacteriaceae isolates, suspected for carbapenemase production, i.e. with meropenem MICs >0.25 mg l-1. The isolate collection contained 100 carbapenemase-producing isolates (36 KPC-2 or KPC-3, 20 VIM-1, 4 KPC-2 plus VIM-1, 5 NDM-1, 2 IMP-1, 1 IMP-28, 1 IMP-1 plus VIM-1 and 31 OXA-48 like) and 29 negative control isolates producing extended-spectrum ß-lactamase and/or AmpC ß-lactamases. PCR and sequencing of ß-lactamase genes were used as reference tests. The sensitivity of the Xpert Carba-R was 100 % (100/100), with a 100 % (29/29) specificity. The time to result was approximately 55 min with a hands-on time of only 1 min per isolate. In conclusion, the Carba-R assay is a rapid and accurate instrument for the confirmation and identification of the blaKPC, blaVIM, blaIMP, blaNDM and blaOXA-48 genes.

Multi-centre evaluation of real-time multiplex PCR for detection of carbapenemase genes OXA-48, VIM, IMP, NDM and KPC.

BACKGROUND: Resistance to carbapenem antibiotics is emerging worldwide among Enterobacteriaceae. To prevent hospital transmission due to unnoticed carriage of carbapenemase producing micro-organisms in newly admitted patients, or follow-up of patients in an outbreak setting, a molecular screening method was developed for detection of the most prevalent carbapenemase genes; blaOXA-48, blaVIM, blaIMP, blaNDM and blaKPC. METHODS: A real-time multiplex PCR assay was evaluated using a collection of 86 Gram negative isolates, including 62 carbapenemase producers. Seven different laboratories carried out this method and used the assay for detection of the carbapenemase genes on a selection of 20 isolates. RESULTS: Both sensitivity and specificity of the multiplex PCR assay was 100%, as established by results on the strain collection and the inter-laboratory comparisons. CONCLUSIONS: In this study, we present a multiplex real-time PCR that is a robust, reliable and rapid method for the detection of the most prevalent carbapenemases blaOXA-48, blaVIM, blaIMP, blaNDM and blaKPC, and is suitable for screening of broth cultured rectal swabs and for identification of carbapenemase genes in cultures.

Consequences of switching from a fixed 2 : 1 ratio of amoxicillin/clavulanate (CLSI) to a fixed concentration of clavulanate (EUCAST) for susceptibility testing of Escherichia coli.

OBJECTIVES: The CLSI recommends a fixed 2 : 1 ratio of co-amoxiclav for broth microdilution susceptibility testing of Enterobacteriaceae, while EUCAST recommends a fixed 2 mg/L clavulanate concentration. The aims of this study were: (i) to determine the influence of a switch from CLSI to EUCAST methodology on Escherichia coli susceptibility rates; (ii) to compare susceptibility results obtained using EUCAST-compliant microdilution with those from disc diffusion and the Etest; and (iii) to evaluate the clinical outcome of patients with E. coli sepsis treated with co-amoxiclav in relation to the susceptibility results obtained using either method. METHODS: Resistance rates were determined in three laboratories that switched from CLSI to EUCAST cards with the Phoenix system (Becton Dickinson) as well as in 17 laboratories that continued to use CLSI cards with the VITEK 2 system (bioMérieux). In one laboratory, isolates were simultaneously tested by both the Phoenix system and either disc diffusion (n = 471) or the Etest (n = 113). Medical and laboratory records were reviewed for E. coli sepsis patients treated with co-amoxiclav monotherapy. RESULTS: Only laboratories that switched methodology showed an increase in resistance rates - from 19% in 2010 to 31% in 2011 (P < 0.0001). All isolates that tested susceptible by microdilution were also susceptible by disc diffusion or the Etest, but of 326 isolates that tested resistant by microdilution, 43% and 59% tested susceptible by disc diffusion and the Etest, respectively. Among the 89 patients included there was a better correlation between clinical response and measured MICs using the Phoenix system than the Etest. CONCLUSIONS: EUCAST methodology resulted in higher co-amoxiclav E. coli resistance rates than CLSI methodology, but correlated better with clinical outcome. EUCAST-compliant microdilution and disc diffusion provided discrepant results.

Appropriateness of empirical treatment and outcome in bacteremia caused by extended-spectrum-ß-lactamase-producing bacteria.

We studied clinical characteristics, appropriateness of initial antibiotic treatment, and other factors associated with day 30 mortality in patients with bacteremia caused by extended-spectrum-ß-lactamase (ESBL)-producing bacteria in eight Dutch hospitals. Retrospectively, information was collected from 232 consecutive patients with ESBL bacteremia (due to Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae) between 2008 and 2010. In this cohort (median age of 65 years; 24 patients were <18 years of age), many had comorbidities, such as malignancy (34%) or recurrent urinary tract infection (UTI) (15%). One hundred forty episodes (60%) were nosocomial, 54 (23%) were otherwise health care associated, and 38 (16%) were community acquired. The most frequent sources of infection were UTI (42%) and intra-abdominal infection (28%). Appropriate therapy within 24 h after bacteremia onset was prescribed to 37% of all patients and to 54% of known ESBL carriers. The day 30 mortality rate was 20%. In a multivariable analysis, a Charlson comorbidity index of ≥ 3, an age of ≥ 75 years, intensive care unit (ICU) stay at bacteremia onset, a non-UTI bacteremia source, and presentation with severe sepsis, but not inappropriate therapy within <24 h (adjusted odds ratio [OR], 1.53; 95% confidence interval [CI], 0.68 to 3.45), were associated with day 30 mortality. Further assessment of confounding and a stratified analysis for patients with UTI and non-UTI origins of infection did not reveal a statistically significant effect of inappropriate therapy on day 30 mortality, and these results were insensitive to the possible misclassification of patients who had received ß-lactam-ß-lactamase inhibitor combinations or ceftazidime as initial treatment. In conclusion, ESBL bacteremia occurs mostly in patients with comorbidities requiring frequent hospitalization, and 84% of episodes were health care associated. Factors other than inappropriate therapy within <24 h determined day 30 mortality.

Detection of carbapenemase-producing Enterobacteriaceae with a commercial DNA microarray.

The Check-MDR CT102 DNA microarray enables detection of the most prevalent carbapenemases (NDM, VIM, KPC, OXA-48 and IMP) and extended-spectrum ß-lactamase (ESBL) gene families (SHV, TEM and CTX-M). The test performance of this microarray was evaluated with 95 Enterobacteriaceae isolates suspected of being carbapenemase producers, i.e. with meropenem MICs ≥0.5 mg l(-1). The collection of isolates contained 70 carbapenemase-producing isolates, including 37 bla(KPC)-, 20 bla(VIM)-, five bla(OXA-48)-, four bla(KPC)/bla(VIM)- and four bla(NDM)-positive isolates; and 25 carbapenemase-gene-negative isolates. ESBLs were produced by 51 of the isolates. PCR and sequencing of ß-lactamase genes was used as reference test. For detection of carbapenemases, the sensitivity of the microarray was 97% (68/70), with 100% specificity. The two negative isolates tested positive when the microarray test was repeated; these isolates were an OXA-48- and a KPC-producing isolate. For ESBL detection, the sensitivity was 100% (51/51) and the specificity was 98% (43/44), although 20% of the SHV-12 ESBLs were categorized as SHV-2-like ESBLs. In conclusion, the CDT102 microarray is a rapid and accurate tool for the detection of carbapenemase and ESBL genes, although the array seems less suitable for epidemiology of ESBL genes.

Comparison of ESBL contamination in organic and conventional retail chicken meat.

Contamination of retail chicken meat by Extended Spectrum Beta-Lactamase (ESBL) producing bacteria likely contributes to the increasing incidence of infections with these bacteria in humans. This study aimed to compare the prevalence and load of ESBL positive isolates between organic and conventional retail chicken meat samples, and to compare the distribution of ESBL genes, strain genotypes and co-resistance. In 2010, 98 raw chicken breasts (n=60 conventional; n=38 organic) were collected from 12 local stores in the Netherlands. Prevalence of ESBL producing micro-organisms was 100% on conventional and 84% on organic samples (p<0.001). Median loads of ESBL producing micro-organisms were 80 (range <20-1360) in conventional, and <20 (range 0-260) CFU/25 g in organic samples (p=0.001). The distribution of ESBL genes in conventional samples and organic samples was 42% versus 56%, respectively (N.S.), for CTX-M-1, 20% versus 42% (N.S.) for TEM-52, and 23% versus 3% (p<0.001) for SHV-12. CTX-M-2 (7%), SHV-2 (5%) and TEM-20 (3%) were exclusively found in conventional samples. Co-resistance rates of ESBL positive isolates were not different between conventional and organic samples (co-trimoxazole 56%, ciprofloxacin 14%, and tobramycin 2%), except for tetracycline, 73% and 46%, respectively, p<0.001). Six of 14 conventional meat samples harbored 4 MLST types also reported in humans and 5 of 10 organic samples harbored 3 MLST types also reported in humans (2 ST10, 2 ST23, ST354). In conclusion, the majority of organic chicken meat samples were also contaminated with ESBL producing E. coli, and the ESBL genes and strain types were largely the same as in conventional meat samples.

A set of multiplex PCRs for genotypic detection of extended-spectrum ß-lactamases, carbapenemases, plasmid-mediated AmpC ß-lactamases and OXA ß-lactamases.

Worldwide, resistance of Gram-negative micro-organisms to third-generation cephalosporins and carbapenems owing to ß-lactamases is an increasing problem. Although the CTX-M, TEM and SHV extended-spectrum ß-lactamases (ESBLs) are most widely disseminated, other ß-lactamase families have also recently emerged, such as plasmid-mediated AmpC ß-lactamases and carbapenemases. Here we describe a new set of multiplex polymerase chain reactions (PCRs) with one amplification protocol enabling detection of 25 prevalent ß-lactamase families, including ESBLs, carbapenemases, plasmid-mediated AmpC ß-lactamases and OXA ß-lactamases.

Guideline for phenotypic screening and confirmation of carbapenemases in Enterobacteriaceae.

Adequate detection of carbapenemase-producing Enterobacteriaceae is crucial for infection control measures and appropriate choice of antimicrobial therapy. This guideline aims to improve the detection of carbapenemase-producing Enterobacteriaceae in the routine setting of clinical microbiology laboratories. Detection of carbapenemases in Enterobacteriaceae includes a screening step followed by a genotypic and optional phenotypic confirmatory step. For all Enterobacteriaceae, the meropenem screening breakpoint to detect carbapenemases is set at >or=0.5mg/L or a zone diameter of or=2mg/L or a zone diameter

Occult hepatitis B in persons infected with HIV is associated with low CD4 counts and resolves during antiretroviral therapy.

Occult hepatitis B virus (HBV) is defined by the presence of plasma HBV DNA in individuals with HBV core antibodies (anti-HBc), but without HBV surface antigen (HBsAg). The prevalence of occult HBV in HIV-infected patients remains controversial, and the risk factors, clinical significance and effect of highly active antiretroviral therapy (HAART) are unknown. The aim of this study was to determine prevalence, risk factors, and clinical significance of occult HBV in HIV-infected patients and to evaluate the effect of HAART. Plasma HBV DNA levels were determined in 191 HIV positive, antiretroviral naïve patients, who were anti-HBc positive and HBsAg negative. Quantitative HBV DNA was determined using a Taqman real-time nested PCR. Additionally, plasma HIV RNA levels, CD4 cell counts, anti-HBs-antibodies, anti-HCV-antibodies, ALT, AST, and gammaGT were determined. Occult HBV (a plasma HBV DNA level >50 copies/ml) was detected in 9/191 (4.7%) of the patients. Among 45 anti-HBs-negative patients (isolated anti-HBc positive), the prevalence was 11.1%. Patients with occult HBV had significantly lower CD4 count compared to anti-HBc-positive/HBsAg negative/HBV DNA-negative patients (105 +/- 157 (median +/- SD) vs. 323 +/- 299 cells/mm(3), P = 0.019). When HAART (including lamivudine) was initiated in the patients with occult HBV, HBV DNA was no longer detectable in any of the patients during 3 years of follow-up. In conclusion, occult HBV was associated with low CD4 counts and may be viewed as opportunistic reactivation of HBV that resolves as a consequence of HAART induced immune reconstitution and/or the effect of lamivudine.

Pharyngitis management: defining the controversy.

Despite numerous controlled trials, clinical practice guidelines and cost-effective analyses, controversy persists regarding the appropriate management strategy for adult pharyngitis. In this perspective, we explore this controversy by comparing two competing clinical guidelines. Although the guidelines appear to make widely diverging recommendations, we show that the controversy centers on only a small proportion of patients: those presenting with severe pharyngitis. We examine recently published data to illustrate that this seemingly simple problem of strep throat remains a philosophical issue: should we give primacy to relieving acute time-limited symptoms, or should we emphasize the potential societal risk of antibiotic resistance? We accept potentially over treating a minority of adult pharyngitis patients with the most severe presentations to reduce suffering in an approximately equal number of patients who will have false negative test results if the test-and-treat strategy were used.

Reconstitution of naive T cells during antiretroviral treatment of HIV-infected adults is dependent on age.

OBJECTIVE: To determine the influence of age on the regeneration rate of naive and memory T cells in the blood of 45 adults on highly active antiretroviral therapy (HAART). METHODS: The age of the patients ranged from 25 to 57 years. Naive cells were defined as CD45RA+CD27+. Cells negative for CD45RA and/or CD27 were considered memory type cells. RESULTS: The recovery rates of naive CD4 and CD8 T cells were similar, were negatively correlated with age and were decreasing 5% and 3.6% per year, respectively. In a multivariate regression analysis, only age was significantly correlated with the naive T cell recovery rates. The recovery rate of memory T cells showed no relation to age. The average regeneration rate of naive CD4 T cells during HAART, i.e., 0.34 x 10(6) cells/l per day, is not lower than regeneration rates in HIV-negative adults following cytotoxic chemotherapy or CD4 monoclonal antibody therapy. CONCLUSION: These observations suggest that the thymus contributes considerably to the regeneration of naive T cells in adults on HAART, and that the impact of HIV infection on naive T cell production is small, or rapidly reversible.