Point prevalence audit surveys of respiratory tract infection consultations and antibiotic prescribing in primary care before and during the COVID-19 pandemic in Ireland.

BACKGROUND: Respiratory tract infections (RTIs) are the most common reason for prescribing antibiotics in general practice. The COVID-19 pandemic has impacted on antibiotic prescribing and delivery of primary care in Ireland. OBJECTIVES: To assess the quality of antibiotic prescribing, the impact of the COVID-19 pandemic and identify opportunities for antimicrobial stewardship (AMS) in Ireland. METHODS: Point prevalence audit surveys for RTI consultations were conducted as part of a European study at three time periods: January-February 2020, March-May 2020 and March-May 2021. Antibiotic prescribing was assessed and comparisons made between the three time periods. RESULTS: In total, 765 consultations were recorded, which were mainly face to face before the pandemic, but changed to predominantly remote consultations during the pandemic surveys in 2020 and 2021 (82% and 75%). Antibiotics were prescribed in 54% of RTI consultations before the pandemic. During pandemic surveys, this dropped to 23% in 2020 and 21% in 2021. There was a decrease in prescribing of Red (reserve) agents in 2021. Assessment against indication-specific quality indicators showed a high proportion of consultations for bronchitis and tonsillitis resulting in an antibiotic prescription (67% and 85%). Point-of-care testing (POCT) to aid diagnosis of RTIs were utilized in less than 1% of consultations. CONCLUSIONS: During the COVID-19 pandemic, there was a reduction in antibiotic prescribing. Opportunities identified to support AMS in primary care in Ireland are targeted initiatives to reduce antibiotic prescribing for bronchitis and tonsillitis and introducing POCT to support appropriate antibiotic prescribing.

[Prevalence of microbiologically-confirmed influenza in patients with influenza-like illness in primary care and clinical and epidemiological characteristics]. / Prevalencia de gripe confirmada microbiológicamente en pacientes con síntomas gripales en atención primaria y características clínico-epidemiológicas.

OBJECTIVE: We evaluated the prevalence of microbiologically-confirmed influenza infection among patients with influenza-like symptoms and compared the clinical and epidemiological characteristics of patients with and without influenza infection. METHODS: Retrospective study of a cohort of patients with influenza-like symptoms from 2016 to 2018 who participated in a clinical trial in thirteen urban primary centres in Catalonia. Different epidemiological data were collected. Patients rated the different symptoms and signs on a Likert scale (absent, little problem, moderate problem and severe problem) and self-reported the measure of health status with the EuroQol visual analogue scale. A nasopharyngeal swab was taken for microbiological isolation of influenza and other microorganisms. RESULTS: A total of 427 patients were included. Microbiologically confirmed influenza was found in 240 patients (56.2%). The percentage of patients with moderate-to-severe cough, muscle aches, tiredness and dizziness was greater among patients with microbiologically confirmed influenza. The self-reported health status was significantly lower among patients with true flu infection (mean of 36.3 ± 18.2 vs 41.7 ± 17.8 in patients without influenza; p<0.001). CONCLUSIONS: Clinical findings are not particularly useful for confirming or excluding the diagnosis of influenza when intensity is not considered. However, the presence of moderate-to-severe cough, myalgias, tiredness and dizziness along with a poor health status is more common in patients with confirmed flu infection.

Burden of disease in children with respiratory tract infections in primary care: diary-based cohort study.

BACKGROUND: Respiratory tract infections (RTIs) are a common reason for children to consult in general practice. Antibiotics are often prescribed, in part due to miscommunication between parents and GPs. The duration of specific respiratory symptoms has been widely studied. Less is known about illness-related symptoms and the impact of these symptoms on family life, including parental production loss. Better understanding of the natural course of illness-related symptoms in RTI in children and impact on family life may improve GP-parent communication during RTI consultations. OBJECTIVE: To describe the general impact of RTI on children and parents regarding illness-related symptoms, absenteeism from childcare, school and work, use of health care facilities, and the use of over-the-counter (OTC) medication. METHODS: Prospectively collected diary data from two randomized clinical trials in children with RTI in primary care (n = 149). Duration of symptoms was analysed using survival analysis. RESULTS: Disturbed sleep, decreased intake of food and/or fluid, feeling ill and/or disturbance at play or other daily activities are very common during RTI episodes, with disturbed sleep lasting longest. Fifty-two percent of the children were absent for one or more days from childcare or school, and 28% of mothers and 20% of fathers reported absence from work the first week after GP consultation. Re-consultation occurred in 48% of the children. OTC medication was given frequently, particularly paracetamol and nasal sprays. CONCLUSION: Appreciation of, and communication about the general burden of disease on children and their parents, may improve understanding between GPs and parents consulting with their child.

The standardised mortality ratio: the proper quality indicator in acute leukaemia?

BACKGROUND: The standardised mortality ratio (SMR) is a quality indicator used to measure quality of care in the Netherlands. It is subject to much criticism, which was the reason to study the value of the SMR as a quality indicator for the treatment of acute leukaemia. METHODS: A retrospective analysis was performed in patients with acute leukaemia admitted to a Santeon hospital during the period 2005-2009. SMR values were calculated and compared with the overall survival (OS). RESULTS: During the study period, 455 unique patients were admitted with acute leukaemia. SMR calculation was based on 992 admissions. SMR analysis yielded a high mortality ratio in hospital 1, 2, 3 and 4 in comparison with the national average (100), significant for hospital 1 and 4 (180 [CI 95% 126-257] and 187 [CI 95% 134-261], respectively) OS analysis also showed a significantly different outcome between hospitals. However, using OS as outcome parameter, hospital 2 and 6 showed the lowest performance as compared with hospital 1 and 4 using SMR as parameter. After multivariate analysis, age (HR 1.04; CI 95% 1.03-1.05; p < 0.001) and hospital (hospital 5 compared with 6: HR 0.54; CI 95% 0.30- .98; p = 0.043; hospital 2 compared with 1: HR 1.51; CI 95% 1.02-2.23; p = 0.039) were the only significant variables that influenced OS. CONCLUSION: Outcome according to SMR is not equivalent to outcome according to OS. This study shows that the use of the SMR as a quality indicator for the treatment of acute leukaemia does not appear to be justified.

Sore throat: effective communication delivers improved diagnosis, enhanced self-care and more rational use of antibiotics.

The majority of throat infections are of viral origin and resolve without antibiotic treatment. Despite this, antibiotic use for sore throat infections remains high, partly because it is difficult to determine when antibiotics may be useful, on the basis of physical findings alone. Antibiotics may be beneficial in bacterial throat infections under certain clinical and epidemiological circumstances; however, even many of those infections in which bacteria play a role do resolve just as quickly without antibiotics. Furthermore, non-medical factors such as patient expectations and patient pressure are also important drivers of antibiotic use. To address these issues, a behavioural change is required that can be facilitated by improved communication between primary healthcare providers and patients. In this article, we provide doctors, nurses and pharmacy staff, working in primary care or in the community, with a structured approach to sore throat management, with the aim of educating and empowering patients to self-manage their condition. The first component of this approach involves identifying and addressing patients' expectations and concerns with regard to their sore throat and eliciting their opinion on antibiotics. The second part is dedicated to a pragmatic assessment of the severity of the condition, with attention to red-flag symptoms and risk factors for serious complications. Rather than just focusing on the cause (bacterial or viral) of the upper respiratory tract infections as a rationale for antibiotic use, healthcare providers should instead consider the severity of the patient's condition and whether they are at high risk of complications. The third part involves counselling patients on effective self-management options and providing information on the expected clinical course. Such a structured approach to sore throat management, using empathetic, non-paternalistic language, combined with written patient information, will help to drive patient confidence in self-care and encourage them to accept the self-limiting character of the illness - important steps towards improving antibiotic stewardship in acute throat infections.

Serum antibody response to influenza virus vaccination during chemotherapy treatment in adult patients with solid tumours.

BACKGROUND: Higher rates of hospitalization and mortality are described in oncology patients with influenza virus infection compared to the general population. Yearly influenza vaccination is recommended for patients treated with chemotherapy. The optimal moment to administer the vaccine during a treatment cycle has not been studied extensively. PATIENTS AND METHODS: During the influenza season 2011-2012 we conducted a multicenter randomized controlled trial (OFLUVAC, NTR2858, no sponsoring) in the Netherlands. Patients receiving adjuvant chemotherapy for breast or colorectal cancer were randomized between early (day 5 after chemotherapy) and late (day 16 after chemotherapy) vaccination with the influenza virus vaccine (Influvac(®) 2011/2012-Vaxigrip(®) 2011/2012). Influenza virus-specific antibody titres were determined before, 3 and 12 weeks after vaccination by haemagglutination inhibition. RESULTS: Thirty-eight breast cancer patients (early=21; late=17) and 18 colorectal cancer patients (early=8; late=10) were analyzed. In breast cancer patients overall serologic responses were adequate. A statistically significant higher response in patients who received early compared to late vaccination in the chemotherapy cycle was observed. Geometric mean titres post vaccination on day 5 versus day 16 were 69.3 versus 27.4 (H3N2), 76.4 versus 17.5 (H1N1) and 34.4 versus 26.0 (B/Brisbane), respectively. In colorectal cancer patients overall serologic responses were adequate, no significant difference was found between early and late vaccination. Geometric mean titres post vaccination on day 5 versus day 16 were 170.1 versus 192.4 (H3N2), 233.0 versus 280.8 (H1N1) and 62.6 versus 75.9 (B/Brisbane), respectively. CONCLUSION: Overall antibody response to the influenza virus vaccine in patients treated with chemotherapy for breast or colorectal cancer patients is adequate. Breast cancer patients seem to mount the best antibody response when vaccinated early after a chemotherapy cycle (≤day 5). No difference was found between early and late vaccination in colorectal cancer patients.

Influenza vaccination coverage in patients treated with chemotherapy: current clinical practice.

BACKGROUND: Influenza virus vaccination is recommended for patients treated with chemotherapy. Little is known about vaccination coverage in these patients. METHODS: Vaccination coverage in the Netherlands was analysed by questionnaires completed by general practitioners, within a catchment area of 1.3 million people, in the period 2010-2011. RESULTS: Of 433 eligible adult patients treated with chemotherapy for breast or colorectal cancer, 144 patients gave permission for us to approach their general practitioner with a questionnaire. General practitioners were asked about vaccination coverage, awareness of recommendations and their opinion about the responsibility for vaccination. We received 114 (79%) completed questionnaires. Sixty-seven out of 114 patients (59%) were vaccinated against influenza. Forty-four (66%) of these patients also had an indication for vaccination based on age (age ≥60 years). According to 48% of the general practitioners, the responsibility for vaccination belongs to the competence of the treating medical oncologist. CONCLUSION: Influenza vaccination coverage is limited to 59% of patients treated with chemotherapy. Guidelines for responsibility (general practitioner or medical oncologist) may increase the vaccination rate of cancer patients.

Response to influenza virus vaccination during chemotherapy in patients with breast cancer.

BACKGROUND: Patients receiving chemotherapy are at increased risk for influenza virus infection. Little is known about the preferred moment of vaccination during chemotherapy. PATIENTS AND METHODS: Breast cancer patients received influenza vaccination during FEC (5-fluorouracil, epirubicin and cyclophosphamide)-containing chemotherapy regimens. Patients were randomised for early (day 4) or late (day 16) vaccination during the chemotherapy cycle. Influenza virus-specific antibody titres were determined before and 3 weeks after vaccination by haemagglutination inhibition. RESULTS: We included 38 breast cancer patients (20 in the early and 18 in the late group) and 21 healthy controls. The overall patient group had significant lower responses to the vaccine compared with healthy controls. Patients vaccinated at day 4 tended to have higher antibody titres as compared with patients vaccinated at day 16, although the difference in post-vaccination titres is not statistically significant. Geometric mean titres post-vaccination for day 4 versus day 16 were 63.7 versus 29.5 (H3N2), 28.2 versus 19.6 (H1N1) and 29.8 versus 16.0 (B/Brisbane), respectively. CONCLUSIONS: Patients on chemotherapy have significantly lower responses to influenza virus vaccination compared with healthy controls. Vaccination early during the chemotherapy cycle induces better responses than does vaccination at day 16 of the cycle. Follow-up studies are needed to confirm this effect.

Intravascular lymphoma as an unusual cause of multifocal cerebral infarctions discovered on FDG-PET/CT.

Intravascular large B-cell lymphoma (IVLBCL) is a rare and aggressive variant of diffuse large B-cell lymphoma with frequent involvement of the central nervous system. Its atypical presentation often delays the diagnosis and due to its aggressive behaviour, the diagnosis is made post-mortem in half of the cases. We report a case of a 67-year-old male patient presenting with speech difficulties and balance disturbances in whom a magnetic resonance imaging (MRI) scan showed multiple lesions of the white matter, denoted as embolic infarctions. He was treated for a suspected endocarditis with antibiotics, but deteriorated neurologically with persistent fever. A consecutive FDG -PET /CT revealed an increased uptake in the adrenals, of which a biopsy showed IVLB CL. The patient was successfully treated with systemic R-CHOP with intrathecal methotrexate and achieved complete remission after six cycles of chemotherapy. The potential role of FDG-PET/CT is illustrated by this case leading to an exceptional diagnosis of IVLBCL.

Pharmacological dependency in chronic treatment of gastroesophageal reflux disease: a randomized controlled clinical trial.

BACKGROUND: Despite evidence of the overuse of acid suppressive medication for gastroesophageal reflux disease (GERD), a transfer to noncontinuous therapy after long-term treatment proves difficult. AIM: To quantify the effect of blinded dosage reduction after long-term therapy on symptom control and quality of life while assessing pharmacological and placebo needs. METHODS: Primary care patients with a history of GERD and long-term treatment were randomized to daily placebo with pantoprazole rescue (n = 141) or daily pantoprazole with placebo rescue (n = 62) upon relief after 4 weeks pantoprazole 20 mg. The number of rescue tablets, symptom control and generic quality of life were analyzed. RESULTS: Measured from the daily placebo arm, 19% of the patients terminated treatment, 33% managed with 2-6 tablets/week, 38% needed a daily dosage and 10% needed more than a daily dosage in the long run. At these final dosages, symptom control and quality of life were dosage-independent and, furthermore, equal to values of patients on fixed daily pantoprazole. A temporal decrease in well-being was seen in 24% of the patients. CONCLUSION: A significant placebo response is apparent in long-term users of acid suppressive medication and pharmacological dependency is overestimated. Despite their history of long-term treatment, the majority of GERD patients can be switched from daily to on-demand treatment without impairing symptom control and quality of life.

Early onset of renal cancer in a family with Birt-Hogg-Dubé syndrome.

Birt-Hogg-Dubé syndrome is a hereditary syndrome characterized by benign disease of skin and lungs and a risk of malignant renal tumors. We describe a clinical and genetic study of a large Dutch family with a novel mutation in the FLCN gene. Renal cancer at very young age occurred in one branch of this family, while in other branches, cutaneous and pulmonary symptoms predominated. A variety of congenital anomalies and connective tissue abnormalities were observed, possibly associated with the gene mutation.

Maintenance treatment for GERD: residual symptoms are associated with psychological distress.

AIM: The aim of this study was to explore determinants of residual reflux symptoms among patients with gastroesophageal reflux disease (GERD) despite maintenance treatment with acid suppressive medication (ASM). METHODS: Primary care GERD patients on chronic ASM were classified as symptom-free (55%) or symptomatic (45%) according to the impact of their residual reflux symptoms (QolRad). They were compared with respect to lifestyle (BMI, alcohol, smoking, physical exercise), compliance (daily ASM dosage), disease history, psychological factors (SCL-90) and quality of life (SF-36). RESULTS: None of the investigated lifestyle factors, nor dosage and disease history were related to residual symptoms. However, symptomatic patients differed from patients with relief on all psychological and quality of life dimensions. In a multiple logistic regression model somatization, hostility, mental health, body pain, as well as gender were independently associated with residual symptoms; the derived ROC curve had an AUC of 0.78. CONCLUSIONS: The majority of GERD patients is symptom-free on chronic ASM; they display a healthy psychological state and high quality of life. Residual symptoms however, are associated with psychological distress and lower quality of life. Recognition of this subgroup might hold the key to improving long-term management of gastroesophageal reflux.

Frequent loss of the AXIN1 locus but absence of AXIN1 gene mutations in adenocarcinomas of the gastro-oesophageal junction with nuclear beta-catenin expression.

Up to 60% of gastro-oesophageal junction (GEJ) adenocarcinomas show nuclear beta-catenin expression, pointing to activated T-cell factor (TCF)/beta-catenin-driven gene transcription. We demonstrate in five human GEJ adenocarcinoma cell lines that nuclear beta-catenin expression indeed correlates with enhanced TCF-mediated transcription of a reporter gene. In several tumour types, TCF/beta-catenin activation is caused by mutations in either adenomatous polyposis coli (APC), beta-catenin exon 3, AXIN1, AXIN2 or beta-transducin repeat-containing protein (beta-TrCP). In GEJ adenocarcinomas, very few APC and beta-catenin mutations have been found. Therefore, the mechanism of Wnt pathway activation remains unclear. In the present study, we did not find AXIN1 gene mutations in 17 GEJ tumours with nuclear beta-catenin expression (without beta-catenin exon 3 mutations). Six intragenic single nucleotide polymorphisms (SNPs) were identified. One of these, the AXIN1 gene T1942C SNP, has a frequency of 21% but is only very recently described despite numerous AXIN1 gene mutational studies. We provide evidence why this SNP was missed in single strand conformation polymorphism analyses. The AXIN1 gene G2063A variation was previously described as a gene mutation but we demonstrate that this is a polymorphism. With these six SNPs loss of heterozygosity (LOH) was found in 11 of 15 (73%) informative tumours. To investigate a possible AXIN1 gene dosage effect in GEJ tumours expressing nuclear beta-catenin, AXIN1 locus LOH was determined in 20 tumours expressing membranous and no nuclear beta-catenin. LOH was found in 10 of 13 (77%) informative cases. AXIN1 protein immunohistochemistry revealed cytoplasmic expression in all tumours irrespective of the presence of AXIN1 locus LOH. These data indicate that nuclear beta-catenin expression is indicative for activated Wnt signalling and that neither AXIN1 gene mutations nor AXIN1 locus LOH are involved in Wnt pathway activation in GEJ adenocarcinomas.

Vector design for optimal protein expression.

Many DNA constructs are generated for protein expression studies. Translational properties and mRNA stability are crucial aspects that have to be accounted for during DNA construction. An optimized vector for protein overexpression studies is described considering elements in the mature mRNA that influence translatability and stability. Recommendations regarding vector construction for Xenopus laevis embryo injection are provided, based on literature and experimental data. The 5'untranslated region (5'UTR) should be non-regulated, short, unstructured, and without AUG codons. The sequence around the start codon should match the initiation context of the species studied (ACCAUGG, for vertebrates), and the open reading frame should be cloned with its own stop codon, followed by a G or A residue. Furthermore, the 3'UTR should be non-regulated, and a strong polyadenylation signal must be included in DNA vectors. In RNA template vectors, the presence of a poly(A) or AC tail is essential for stability, as well as for translation efficiency in mRNA injection experiments. These aspects result in high-level expression of exactly the desired protein. Easily obtainable examples of the sequences [5'UTR, 3'UTR, and poly(A) signal] are suggested.

Salmonella pathogenicity island 1-independent induction of apoptosis in infected macrophages by Salmonella enterica serotype typhimurium.

The enteric pathogen Salmonella enterica serotype Typhimurium induces apoptosis in infected macrophages. This process is rapid, specific, and depends on the type III protein secretion system encoded within Salmonella pathogenicity island 1 (SPI1). Here, we demonstrate that serotype Typhimurium can activate programmed macrophage cell death independently of SPI1. SPI1 independent induction of apoptosis in infected macrophages is observed as early as 12 to 13 h postinfection, even in the absence of intracellular bacterial replication. Delayed activation of programmed macrophage cell death is not observed with serotype Typhimurium strains mutated in ompR or SPI2. Even though SPI2 mutants have a defect in intracellular proliferation, our results indicate that long-term intracellular survival and growth are not required for delayed macrophage killing per se, since Salmonella mutants that are severely defective in intracellular growth still induce delayed apoptosis. Inactivation of genes required for either rapid or delayed induction of apoptosis results in a conditional noncytotoxic phenotype, whereas simultaneous inactivation of genes required for both rapid and delayed induction of apoptosis renders serotype Typhimurium noncytotoxic under all conditions tested. Our hypothesis is that differential activation of programmed macrophage cell death by serotype Typhimurium occurs under discrete physiological conditions at distinct locations within an infected host.

Controlled translation initiation on insulin-like growth factor 2-leader 1 during Xenopus laevis embryogenesis.

A number of growth factors, whose spatio-temporal expression is essential for embryonic development, are encoded by mRNAs with a complex 5'UTR. Human insulin-like growth factor 2 mRNA contains a long (592 nucleotides) 5'UTR (IGFl1) with one upstream open reading frame and stable stem-loop structures, elements which might be important for controlled translation. To investigate whether these unusual features of IGFl1 can control translation initiation during embryogenesis, we examined the initiation efficiency on this 5'UTR during development of Xenopus laevis. The results demonstrate that IGFl1 strongly represses translation of a reporter in early embryos, compared with the Xenopus beta-globin 5'UTR. The inhibition is alleviated soon after the midblastula transition, suggesting a stimulatory effect of the transcription start. However, a similar stimulation of IGFl1-driven translation is seen in embryos in which de novo transcription was inhibited by actinomycin D. Furthermore, it is shown that up-regulation of IGFl1 activity is independent of eIF4E levels, and activity of IGFl1 is observed in all tissues of transgenic Xenopus embryos. These results indicate that post-translational modulation of a trans-acting factor enables efficient initiation on this complex 5'UTR after the midblastula transition.

Sequence and translation initiation properties of the xenopus TGFbeta5, PDGF-A, and PDGF-alpha receptor 5' untranslated regions.

The properties of the architecturally complex Xenopus laevis TGFbeta5, PDGF-A and PDGF-alpha receptor 5'UTRs were investigated. 5' extended cDNAs were obtained by 5'RACE, resulting in long 5'UTRs (478-710 nt) with multiple upstream AUGs (3-13), andthe potential to fold into stable structures. Injection studies suggested that the cloned PDGF-alphaR 5'UTR contains an intron. Splicing at potential 5' and 3' splice sites would result in a non-complex 5'UTR of 142 nt. The above mentioned 5'UTR characteristics are inhibitory for ribosomal scanning. Indeed, relative to the beta-globin 5'UTR, the complex 5'UTRs strongly repressed initiation of protein synthesis in pre-MBT Xenopus embryos. However, later in embryogenesis, the inhibition was partly relieved. The results show temporal translational control by these 5'UTRs. Transgenic embryos showed that the 5'UTRs allowed translation throughout the embryo; spatial control could not be observed. Interestingly, a fragment in the PDGF-A 5'UTR highly similar to an element in the human PDGF-A 5'UTR is complementary to Xenopus 18S ribosomal RNA. None of these Xenopus 5'UTRs contains an IRES, as determined by injecting bicistronic constructs.

The role of the 5' untranslated region of an mRNA in translation regulation during development.

Cap-dependent ribosomal scanning occurs on the majority of cellular 5' UTRs. This process is severely hampered on long 5' UTRs, containing AUGs and secondary structure. These characteristics are often found in mRNAs encoding regulatory proteins like proto-oncogenes, growth factors, their receptors, and homeodomain proteins. A number of these mRNAs use an alternative mechanism of translation initiation, involving an internal ribosomal entry site (IRES). Cellular mRNAs containing a complex 5' UTR or an IRES share an intriguing characteristic: their translational efficiency can be very specifically regulated by their 5' UTR, providing post-transcriptional regulation. During embryonic development, the 5' UTRs of Antp. Ubx RAR beta 2 c-mos and c-myc regulate protein expression in a spatio-temporal manner. Translation initiation on a number of growth factor RNAs (IGFII, PDGF2, TGF beta, FGF-2, and VEGF) is specifically regulated during differentiation, growth, and stress. Furthermore, 5' UTR activity, mutations in the 5' UTR, or the occurrence of alternative 5' UTRs have been implicated in the progression of various forms of cancer. The mechanisms involved in 5' UTR mediated control are not well understood. Binding of trans-acting factors could mediate translation stimulation or repression. Furthermore, the precise localization of upstream AUGs and the activity of the cap-binding initiation factor 4E are suggested to be important for translation regulation of these mRNAs. This review focuses on 5' UTRs whose activity is regulated, the processes during which this regulation occurs, and as far as known the mechanisms involved.

Multiple fimbrial adhesins are required for full virulence of Salmonella typhimurium in mice.

Adhesion is an important initial step during bacterial colonization of the intestinal mucosa. However, mutations in the Salmonella typhimurium fimbrial operons lpf, pef, or fim only moderately alter mouse virulence. The respective adhesins may thus play only a minor role during infection or S. typhimurium may encode alternative virulence factors that can functionally compensate for their loss. To address this question, we constructed mutations in all four known fimbrial operons of S. typhimurium: fim, lpf, pef, and agf. A mutation in the agfB gene resulted in a threefold increase in the oral 50% lethal dose (LD50) of S. typhimurium for mice. In contrast, an S. typhimurium strain carrying mutations in all four fimbrial operons (quadruple mutant) had a 26-fold increased oral LD50. The quadruple mutant, but not the agfB mutant, was recovered in reduced numbers from murine fecal pellets, suggesting that a reduced ability to colonize the intestinal lumen contributed to its attenuation. These data are evidence for a synergistic action of fimbrial operons during colonization of the mouse intestine and the development of murine typhoid fever.