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.

The added value of chlamydia screening between 2008-2010 in reaching young people in addition to chlamydia testing in regular care; an observational study

Background

Internet-based Chlamydia Screening Implementation (chlamydia screening programme) was introduced in the Netherlands in 2008-2010 to detect and treat asymptomatic infections and to limit ongoing transmission through annual testing and treatment of Chlamydia trachomatis in young people (16-29 years). This population-based screening may be less effective when addressing individuals who are already covered by regular care, instead of addressing a hidden key population without chlamydia testing experience in regular care. This study had two aims: (1) to assess the rate and determinants of newly reached (i.e. not previously tested in 2006-2010) participants in the chlamydia screening programme, and (2) to assess the chlamydia positivity in these newly reached participants.

Methods

This observational matching study included all chlamydia tests performed in subjects aged 16-29 years in eastern South Limburg in the Netherlands (population 16-29 years:41,000) between 2006-2010. Testing was conducted during the systematic chlamydia screening programme (2008-2010), at a sexually transmitted infections clinic (STI clinic), by general practitioners (GPs), and by medical specialists as reported by the medical laboratory serving the region. Data were matched between testing services on individual level. The study population included all participants who were tested at least once for chlamydia by the chlamydia screening programme. Participants were included at their first chlamydia screening participation.

Results

In the chlamydia screening programme, 80.7% (4298/5323) of participants were newly reached, others were previously tested by the STI clinic (5.7%, n=304), GPs (6.2%, n=328), medical specialists (3.5%, n=187) or a combination of providers (3.9%, n=206). Chlamydia prevalence was similar in newly reached participants (4.8%, 204/4298) and participants previously tested (4.5%, 46/1025, P=0.82). Independent determinants for being a newly reached participant were male gender (men OR 2.9; 95% CI 2.5-3.4) and young age <21 years (versus 25-29 years OR 1.8; 95% CI 1.5-2.2).

Conclusions

The majority of the chlamydia screening programme participants have not been tested by regular care, and show similar chlamydia prevalence as those previously tested. Thereby population-based chlamydia screening adds to the existing regular care by testing young individuals hidden to current regular care.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0612-2) contains supplementary material, which is available to authorized users.

Identification of hidden key hepatitis C populations: an evaluation of screening practices using mixed epidemiological methods

BACKGROUND

Hepatitis C virus (HCV) is a major cause of liver diseases worldwide. Due to its asymptomatic nature, screening is necessary for identification. Because screening of the total population is not cost effective, it is important to identify which risk factors for positivity characterize the key populations in which targeting of screening yields the highest numbers of HCV positives, and assess which of these key populations have remained hidden to current care.

METHODS

Laboratory registry data (2002-2008) were retrieved for all HCV tests (23,800) in the south of the Netherlands (adult population 500,000). Screening trends were tested using Poisson regression and chi-square tests. Risk factors for HCV positivity were assessed using a logistic regression. The hidden HCV-positive population was estimated by a capture-recapture approach.

RESULTS

The number of tests increased over time (2,388 to 4,149, p<.01). Nevertheless, the positivity rate among those screened decreased between 2002 and 2008 (6.3% to 2.1%, p<.01). The population prevalence was estimated to be 0.49% (95%CI 0.41-0.59). Of all HCV-positive patients, 66% were hidden to current screening practices. Risk factors associated with positivity were low socio-economic status, male sex, and age between 36-55. In future screening 48% (95%CI 37-63) of total patients and 47% (95%CI 32-70) of hidden patients can be identified by targeting 9% (men with low socio-economic status, between 36-55 years old) of the total population.

CONCLUSIONS

Although the current HCV screening policy increasingly addresses high-risk populations, it only reaches one third of positive patients. This study shows that combining easily identifiable demographic risk factors can be used to identify key populations as a likely target for effective HCV screening. We recommend strengthening screening among middle-aged man, living in low socio-economic neighborhoods.

The role of MHC class I expression in rat NK cell-mediated lysis of syngeneic tumor cells and virus-infected cells

In this study the role of MHC class I antigen expression in rat natural killer (NK) cell-mediated lysis was investigated. Various rat tumor cell lines and two Adenovirus (Ad)-transformed rat cell lines were tested for their expression levels of total MHC class I and two MHC class I alleles, RT1.A and RT1.C, by flow cytometry. Their susceptibility to NK cell-mediated lysis in relation to MHC class I expression was determined by 51Cr release assays. IFN-gamma is know to increase the expression of MHC class I. Therefore target cell with and without prior IFN-gamma treatment were examined for MHC class I expression and its effect on NK lysis. An significant inverse exponential relationship was found. To investigate the effect of virus infection on MHC class I expression and target cell lysis by NK cells, rat embryonal fibroblasts (REF) were infected with cytomegalovirus (CMV) and used as target cells for NK cell-mediated lysis. Results showed that these virus-infected cells were less susceptible to NK lysis than non-infected cells. Moreover, the non-infected cells expressed less MHC class I than the infected cells, indicating that also in this case, there was an inverse correlation between MHC class I expression and susceptibility to lysis by NK cells. Subsequently, we showed that sorted subsets of predominantly CD8-positive and CD8-negative NK cells lysed a MHC class I-positive tumor cell line at the same level. This suggests that CD8 is not likely to participate as a receptor for MHC class I in NK cell-mediated lysis in a syngeneic rat model.

The presence of cytomegalovirus antigens in karyotyped abortions

PROBLEM

About one out of six pregnancies ends in spontaneous abortion before the 17th week. In more than half of these a chromosome abnormality is present, which explains the abortion. The role of cytomegalovirus (CMV) infections in early pregnancy failure is unclear. If there is a role for CMV, a preponderance of infections would be expected in a chromosomally normal group.

METHOD

The significance of CMV in abortions has been studied by screening 80 spontaneous and nine induced abortions with known karyotype for the presence of phosphoprotein pp65, an early CMV antigen. Also, endometrial biopsies (n = 55) and menstruum (n = 10) were screened. In 11 patients more than one specimen was available for study.

RESULTS

The protein was present in the glandular epithelium of the decidua of spontaneous as well as induced abortions in 31 of 89 (35%) cases, irrespective of chromosomal constitution. Trophoblastic cells were pp65 positive in 6/89 cases. A total of 17 embryos could be studied, seven of which were positive. Positive staining of embryonic organs correlated strongly with the presence of the antigen in the decidua. The endometrial biopsies and menstrual discharges from women of comparable ages showed the same percentages of positive tests for pp65: 35 and 20%. Histologically positive and negative specimens could not be differentiated other than by the specific staining. In 10 of 11 patients with more than one specimen available, the results were consistent. One patient had two positive and one negative specimen.

CONCLUSION

The findings indicate that in early pregnancy cytomegalovirus is transmitted from the decidual glands to the foetus. However, we have not found indications that the presence of cytomegalovirus infection as shown by the presence of antigen is pathogenic for early pregnancy.

Activity of the anti-HIV agent 9-(2-phosphonyl-methoxyethyl)-2,6-diaminopurine against cytomegalovirus in vitro and in vivo

9-(2-phosphonylmethoxyethyl)-2,6-diaminopurine (PMEDAP), a potent inhibitor of human immunodeficiency virus (HIV) replication, was evaluated for its activity against human cytomegalovirus (HCMV) in vitro, and murine cytomegalovirus (MCMV) and rat CMV (RCMV) in vivo. PMEDAP strongly inhibited HCMV-induced cytopathicity in human embryonic lung (HEL) cell cultures (EC50 11 microM) and caused a concentration-dependent suppression of viral DNA synthesis (IC50 20 microM) [corrected]. PMEDAP had no effect on the expression of HCMV-specific immediate early antigens (IEA) as measured on day 1 post-infection, but inhibited the expression of HCMV late antigens as measured on day 6 post-infection (EC50 20 microM) [corrected]. The diphosphate derivative of PMEDAP (PMEDAPpp) selectively inhibited HCMV-induced DNA polymerase (IC50 0.1 microM). PMEDAP proved markedly effective in reducing the mortality rate of NMRI mice that had been infected intraperitoneally or intracerebrally with a lethal dose of MCMV. PMEDAP exhibited greater anti-MCMV activity when administered as a single dose immediately after infection than when this dose was divided over repeated administrations. 9-(2-phosphonylmethoxyethyl)-adenine (PMEA) also prevented MCMV-induced mortality, but only at a dose ten-fold higher than that of PMEDAP. PMEDAP also delayed death in severe combined immune deficiency (SCID) mice that had been infected with MCMV. The effect of PMEDAP on RCMV infections in rats was less pronounced.

Faecal and pharyngeal shedding of rotavirus and rotavirus IgA in children with diarrhoea

In 70 children 0-4 years of age with acute diarrhoea, the shedding of rotavirus and the excretion of rotavirus-specific IgA antibody in the stools were examined throughout the period of clinical symptoms. Quantitative detection of rotavirus and IgA was performed by an ELISA technique. The maximal rotavirus shedding was found between the second and fifth day and the maximal excretion of IgA antibody about the seventh day, which marked the clinical recovery of most children. Throat swabs were examined for both virus particles and specific IgA antibody to try to document the respiratory spread of rotavirus infection. Rotavirus antigen could not be demonstrated in the throat swabs, but specific IgA antibody was detected at levels comparable to the faecal specimens obtained at clinical recovery. The observations indicate that the presence of rotavirus secretory IgA limits the duration of diarrhoea and plays a major role in the intestinal resistance to infection.

Symptomatic and asymptomatic rotavirus infections in hospitalized children

During one year, 871 infants and children admitted to a Dutch paediatric ward were examined weekly for rotavirus. Rotavirus was detected in the stools of 64/129 (49.6%) children with diarrhoea and in 283/742 (38.1%) controls. The incidence of asymptomatic rotavirus excretors increased from 14.5% in infants 0 to 6 months of age to 65.8% in children of 6 years and over, a feature not yet reported. Possible explanations may be the methodology used, the age groups studied, the local hospital (and community) situation and the geographical location. Routine bacteriology revealed enteropathogens in 25.6% of the children with diarrhoea: Salmonellae in 20.9%, Campylobacter jejuni in 3.9%, Yersinia enterocolitica in 1.5%, Shigella sonnei in 0.8% and enteropathogenic E. coli in 0.8% of the patients.