Point-of-care lung ultrasound in detecting pneumonia: A systematic review.

Purpose: Limited evidence exists to assess the sensitivity, specificity, and accuracy of point-of-care lung ultrasound (LUS) across all age groups. This review aimed to investigate the benefits of point-of-care LUS for the early diagnosis of pneumonia compared to traditional chest X-rays (CXR) in a subgroup analysis including pediatric, adult, and geriatric populations. Material and Methods: This systematic review examined systematic reviews, meta-analyses, and original research from 2017 to 2021, comparing point-of-care LUS and CXR in diagnosing pneumonia among adults, pediatrics and geriatrics. Studies lacking direct comparison or exploring diseases other than pneumonia, case reports, and those examining pneumonia secondary to COVID-19 variants were excluded. The search utilized PubMed, Google Scholar, and Cochrane databases with specific search strings. The study selection, conducted by two independent investigators, demonstrated an agreement by the Kappa index, ensuring reliable article selection. The QUADAS-2 tool assessed the selected studies for quality, highlighting risk of bias and applicability concerns across key domains. Statistical analysis using Stata Version 16 determined pooled sensitivity and specificity via a bivariate model, emphasizing LUS and CXR diagnostic capabilities. Additionally, RevMan 5.4.1 facilitated the calculation of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), offering insights into diagnostic accuracy. Results: The search, conducted across PubMed, Google Scholar, and Cochrane Library databases by two independent investigators, initially identified 1045 articles. Following screening processes, 12 studies comprised a sample size of 2897. LUS demonstrated a likelihood ratio of 5.09, a specificity of 81.91%, and a sensitivity of 92.13% in detecting pneumonia in pediatric, adult, and geriatric patients, with a p-value of 0.0002 and a 95% confidence interval, indicating diagnostic accuracy ranging from 84.07% to 96.29% when compared directly to CXR. Conclusion: Our review supports that LUS can play a valuable role in detecting pneumonia early with high sensitivity, specificity, and diagnostic accuracy across diverse patient demographics, including pediatric, adult, and geriatric populations. Since it overcomes most of the limitations of CXR and other diagnostic modalities, it can be utilized as a diagnostic tool for pneumonia for all age groups as it is a safe, readily available, and cost-effective modality that can be utilized in an emergency department, intensive care units, wards, and clinics by trained respiratory care professionals.

The role of the plasmid-mediated fluoroquinolone resistance genes as resistance mechanisms in pediatric infections due to Enterobacterales.

Introduction: Fluoroquinolones (FQs) are not commonly prescribed in children, yet the increasing incidence of multidrug-resistant (MDR) Enterobacterales (Ent) infections in this population often reveals FQ resistance. We sought to define the role of FQ resistance in the epidemiology of MDR Ent in children, with an overall goal to devise treatment and prevention strategies. Methods: A case-control study of children (0-18 years) at three Chicago hospitals was performed. Cases had infections by FQ-susceptible, ß-lactamase-producing (bla) Ent harboring a non- or low-level expression of PMFQR genes (PMFQS Ent). Controls had FQR infections due to bla Ent with expressed PMFQR genes (PMFQR Ent). We sought bla genes by PCR or DNA (BD Max Check-Points assay®) and PMFQR genes by PCR. We performed rep-PCR, MLST, and E. coli phylogenetic grouping. Whole genome sequencing was additionally performed on PMFQS Ent positive isolates. Demographics, comorbidities, and device, antibiotic, and healthcare exposures were evaluated. Predictors of infection were assessed. Results: Of 170 ß-lactamase-producing Ent isolates, 85 (50%) were FQS; 23 (27%) had PMFQR genes (PMFQS cases). Eighty-five (50%) were FQR; 53 (62%) had PMFQR genes (PMFQR controls). The median age for children with PMFQS Ent and PMFQR Ent was 4.3 and 6.2 years, respectively (p = NS). Of 23 PMFQS Ent, 56% were Klebsiella spp., and of 53 PMFQR Ent, 76% were E. coli. The most common bla and PMFQR genes detected in PMFQS Ent were bla SHV ESBL (44%) and oqxAB (57%), and the corresponding genes detected in PMFQR Ent were bla CTX-M-1-group ESBL (79%) and aac(6')-Ib-cr (83%). Whole genome sequencing of PMFQS Ent revealed the additional presence of mcr-9, a transferable polymyxin resistance gene, in 47% of isolates, along with multiple plasmids and mobile genetic elements propagating drug resistance. Multivariable regression analysis showed that children with PMFQS Ent infections were more likely to have hospital onset infection (OR 5.7, 95% CI 1.6-22) and isolates containing multiple bla genes (OR 3.8, 95% CI 1.1-14.5). The presence of invasive devices mediated the effects of healthcare setting in the final model. Differences in demographics, comorbidities, or antibiotic use were not found. Conclusions: Paradoxically, PMFQS Ent infections were often hospital onset and PMFQR Ent infections were community onset. PMFQS Ent commonly co-harbored multiple bla and PMFQR genes, and additional silent, yet transferrable antibiotic resistance genes such as mcr-9, affecting therapeutic options and suggesting the need to address infection prevention strategies to control spread. Control of PMFQS Ent infections will require validating community and healthcare-based sources and risk factors associated with acquisition.

Ethnicity, Social Determinants of Health, and Pediatric Primary Care During the COVID-19 Pandemic.

This study assessed the relationship between ethnicity, social determinants of health (SDH), and measures of health outcomes for children during the COVID-19 pandemic. This retrospective study reviewed electronic medical records of 1234 in-person well child visits (WCVs for age <18 years) at a single academic primary care clinic in a Chicago suburb for the results of SDH screening in the domains of food, financial, and transportation insecurity. The association between ethnicity, unmet SDH domains, routine medical care delay, vaccine delays, and utilization of acute and emergency department (ED) visits were evaluated. Patients with unmet SDH were more likely to be non-White (P < .001), ≥3 years of age (P < .001) and have Medicaid coverage (P < .001). Unmet social needs were also associated with more acute visits (P < .001), ED visits (P < .001), and WCV delays (P < .001). The results suggest that the COVID-19 pandemic has disproportionately affected patients with unmet SDH in obtaining routine pediatric well child care.

Social Determinants of Health Screening at Well Child Visits: A Pilot Program Implemented During the COVID-19 Pandemic.

This study demonstrates the challenges of establishing social determinants of health (SDH) screening at well child visits (WCVs) during the COVID-19 pandemic. We conducted a 6-month pre-intervention retrospective chart review (2/2020-8/2020) and 6-month post-intervention prospective chart review (8/2020-2/2021) of an SDH screening and referral protocol at a single suburban academic pediatric clinic. WCVs were screened for food, financial, and transportation needs. With the new protocol, 46% of eligible WCVs (n = 1253/2729) had documented screening results. Self-report of screened visits found 34.6% with financial strain, 32% with worry about food insecurity, 25.1% with food insecurity, 5.3% with medical transportation difficulties, and 6% with daily living transportation difficulties. There was an increase in resources offered during the post-intervention period (OR = 11.5 [7.1-18.6], P < .001). There was also an increase in resident physician self-reported knowledge in providing referrals (P = .04).

Breast Cancer in the Elderly: An Observational Study Investigating Compliance of Screening Mammography in an Underserved Community.

BACKGROUND: The incidence of breast cancer increases with age. Individuals living in higher socioeconomic communities also have higher incidence secondary to early detection of breast cancer from increased accessibility to mammograms. This retrospective study studied the percentage of new breast cancer cases in the elderly between 2010 and 2019, and investigated the compliance of screening mammography in some of the medically underserved suburbs of southern Chicago. METHODS: The parameters used to power this study include "age greater than 70" and "2010 to present" at the time the study was first initiated. The final data set contained 381 electronic health records (EMRs) that met the parameters of interest. We specifically looked at method of diagnosis, stage at diagnosis, date of last normal screening mammogram, hormone status, histology, race, and smoking history. RESULTS: Thirty percent of the breast cancer patients diagnosed at our institution were over 70 years of age between 2010 and 2019. Of the 381 patients included in the overall sample, 45% were diagnosed with breast cancer by screening mammogram, and 52% of individuals in the 70 - 75 age group were diagnosed with breast cancer by screening mammography. Only 40% of individuals in the 75+ age group were diagnosed with breast cancer by screening mammogram (P = 0.0234). Furthermore, in the overall sample, 63% had a normal screening mammogram at some time prior to their breast cancer diagnosis. In the 70 - 75 age group, 76% had a normal screening mammogram at some time prior to their breast cancer diagnosis. In the 75+ age group, only 54% had a normal screening mammogram at some time prior to their breast cancer diagnosis (P < 0.0001). Individuals in both age groups were more likely to have early-stage breast cancers and luminal A hormone expression. CONCLUSIONS: Decreased compliance to screening mammography is observed in the elderly living in underserved communities. Since the elderly are underrepresented in research, organizations do not have sufficient information to recommend screening mammography in the elderly. With increasing life expectancy, observational studies have demonstrated a mortality benefit with screening mammography by early detection of breast cancer, favorable breast cancer characteristics and potentially higher cure rates. Socioeconomic factors also affect screening compliance and likely influenced the results of our study. Future studies should investigate how individual factors influence screening mammography compliance in the elderly in underserved communities.

Autoimmune Thyroid Disease and Psoriasis Vulgaris after COVID-19 in a Male Teenager.

COVID-19 is implicated in triggering autoimmune, dermatologic, and thyroid diseases. We present a first known case of development of Graves' disease and psoriasis vulgaris in a previously healthy male teenager without any family history, diagnosed after COVID-19 infection. Evaluation of "long COVID syndrome" should include thorough history and thyroid evaluation.

A Multicentered Study of the Clinical and Molecular Epidemiology of TEM- and SHV-type Extended-Spectrum Beta-Lactamase Producing Enterobacterales Infections in Children.

BACKGROUND: Extended-spectrum ß-lactamase (ESBL)-producing Enterobacterales-(Ent) infections are increasing in pediatrics. Before CTX-M ESBL emerged, the most common infection-associated ESBL genes were TEM and SHV-type ESBLs. We sought to define the current epidemiology of Ent infections in children due to blaTEM and blaSHV (TEM-SHV-Ent). METHODS: A retrospective case-control analysis of children with TEM-SHV-Ent infections at 3 Chicago-area hospitals was performed. Cases had extended-spectrum-cephalosporin (ESC)-resistant infections due to blaTEM or blaSHV. DNA analysis assessed ß-lactamase (bla) genes, multilocus sequence types, and E. coli phylogenetic grouping. Controls had ESC-susceptible Ent infections, matched 3:1 to cases by age, source, and hospital. Clinical-epidemiologic infection predictors were assessed. RESULTS: Of 356 ESC-R-Ent isolates from children (median 4.3 years), 38 (10.7%) were positive solely for blaTEM-ESBL (26%) or blaSHV-ESBL genes (74%). Predominant organisms were Klebsiella (34.2%) and E. coli (31.6%); 67% of E. coli were phylogroup B2. Multilocus sequence types revealed multiple strains, 58% resistant to ≥3 antibiotic classes. On multivariable analysis, children with TEM-SHV-Ent infections more often had recent inpatient care (OR, 8.2), yet were diagnosed mostly as outpatients (OR, 25.6) and less in Neonatal Intensive Care Units (OR, 0.036) than controls. TEM-SHV-Ent patients had more gastrointestinal (OR, 23.7) and renal comorbidities (OR, 4.2). Differences in demographics, antibiotic exposure, and foreign bodies were not found. CONCLUSION: TEM-SHV-Ent are commonly linked to inpatient exposures in children with chronic conditions but most often present in outpatient settings. Clinicians should be aware of the potential increased risk for TEM-SHV-Ent infections in outpatients with gastrointestinal and renal comorbidities and histories of prolonged hospital stays.

A neurotoxin that specifically targets Anopheles mosquitoes.

Clostridial neurotoxins, including tetanus and botulinum neurotoxins, generally target vertebrates. We show here that this family of toxins has a much broader host spectrum, by identifying PMP1, a clostridial-like neurotoxin that selectively targets anopheline mosquitoes. Isolation of PMP1 from Paraclostridium bifermentans strains collected in anopheline endemic areas on two continents indicates it is widely distributed. The toxin likely evolved from an ancestral form that targets the nervous system of similar organisms, using a common mechanism that disrupts SNARE-mediated exocytosis. It cleaves the mosquito syntaxin and employs a unique receptor recognition strategy. Our research has an important impact on the study of the evolution of clostridial neurotoxins and provides the basis for the use of P. bifermentans strains and PMP1 as innovative, environmentally friendly approaches to reduce malaria through anopheline control.

The Clinical and Molecular Epidemiology of CTX-M-9 Group Producing Enterobacteriaceae Infections in Children.

INTRODUCTION: The pandemic of extended-spectrum beta-lactamase-(ESBL)-producing Enterobacteriaceae (Ent) is strongly linked to the dissemination of CTX-M-type-ESBL-Ent. We sought to define the epidemiology of infections in children due to an emerging resistance type, CTX-M-9-group-producing-Ent (CTX-M-9-grp-Ent). METHODS: A retrospective matched case-control analysis of children with CTX-M-9-grp-Ent infections who received medical care at three Chicago area hospitals was performed. Cases were defined as children possessing extended-spectrum cephalosporin-resistant (ESC-R) infections due to blaCTX-M-9. PCR and DNA analysis assessed beta-lactamase (bla) genes, multi-locus sequence types (MLST) and phylogenetic grouping of E. coli. Controls were children with ESC-susceptible (ESC-S)-Ent infections matched one case to three controls by age, source, and hospital. The clinical-epidemiologic predictors of CTX-M-9-grp-Ent infection were assessed. RESULTS: Of 356 ESC-R-Ent isolates from children (median age 4.1 years), the CTX-M-9-group was the solely detected bla gene in 44 (12.4%). The predominant species was E. coli (91%) of virulent phylogroups D (60%) and B2 (40%). MLST revealed multiple strain types. On multivariable analysis, CTX-M-9-grp-Ent occurred more often in E. coli than other Ent genera (OR 7.4, 95% CI 2.4, 27.2), children of non-Black-White-Hispanic race (OR 7.4, 95% CI 2.4, 28.2), and outpatients (OR 4.5, 95% CI 1.7, 12.3), which was a very unexpected finding for infections due to antibiotic-resistant bacteria. Residents of South Chicago had a 6.7 times higher odds of having CTX-M-9-grp-Ent infections than those in the reference region (West), while residence in Northwestern Chicago was associated with an 81% decreased odds of infection. Other demographic, comorbidity, invasive-device, and antibiotic use differences were not found. CONCLUSION: CTX-M-9-grp-Ent infection may be associated with patient residence and is occurring in children without traditional in-patient exposure risk factors. This suggests that among children, the community environment may be a key contributor in the spread of these resistant pathogens.

Community Origins and Regional Differences Highlight Risk of Plasmid-mediated Fluoroquinolone Resistant Enterobacteriaceae Infections in Children.

BACKGROUND: Fluoroquinolones are uncommonly prescribed in children, yet pediatric multidrug resistant (MDR) enterobacteriaceae (Ent) infections often reveal fluoroquinolone resistance (FQR). We sought to define the molecular epidemiology of FQR and MDR-Ent in children. METHODS: A case-control analysis of children with MDR-Ent infections at 3 Chicago hospitals was performed. Cases were children with third-generation cephalosporin-resistant and/or carbapenem-resistant Ent infections. Polymerase chain reaction and DNA analysis assessed bla and plasmid-mediated FQR (PMFQR) genes. Controls were children with third-generation cephalosporin, fluoroquinolone, and carbapenem-susceptible Ent infections matched by age, source and hospital. We assessed clinical-epidemiologic predictors of PMFQR Ent infection. RESULTS: Of 169 third-generation cephalosporin-resistant and/or carbapenem-resistant Ent isolates from children (median age, 4.8 years), 85 were FQR; 56 (66%) contained PMFQR genes. The predominant organism was Escherichia coli, and most common bla gene blaCTX-M-1 group. In FQR isolates, PMFQR gene mutations included aac6'1bcr, oqxA/B, qepA and qnrA/B/D/S in 83%, 15%, 13% and 11% of isolates, respectively. FQR E. coli was often associated with phylogroup B2, ST43/ST131. On multivariable analysis, PMFQR Ent infections occurred mostly in outpatients (odds ratio, 33.1) of non-black-white-Hispanic race (odds ratio, 6.5). Residents of Southwest Chicago were >5 times more likely to have PMFQR Ent infections than those in the reference region, while residence in Central Chicago was associated with a 97% decreased risk. Other demographic, comorbidity, invasive-device, antibiotic use or healthcare differences were not found. CONCLUSIONS: The strong association of infection with MDR organisms showing FQR with patient residence rather than with traditional risk factors suggests that the community environment is a major contributor to spread of these pathogens in children.

A Multi-Centered Case-Case-Control Study of Factors Associated With Klebsiella pneumoniae Carbapenemase-Producing Enterobacteriaceae Infections in Children and Young Adults.

BACKGROUND: Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae (KPC-CRE) are multidrug-resistant organisms causing morbidity and mortality worldwide. KPC-CRE prevalence is increasing in pediatric populations, though multi-centered data are lacking. Identifying risk factors for KPC-CRE infection in children and classifying genotypes is a priority in this vulnerable population. METHODS: A case-case-control study of patients (0-22 years) at 3 tertiary-care Chicago-area medical centers, 2008-2015, was conducted. Case group 1 children possessed KPC-CRE infections; case group 2 harbored carbapenem-susceptible Enterobacteriaceae (CSE) infections; controls had negative cultures. Case-control matching was 1:1:3 by age, infection site and hospital. Statistical and molecular analyses were performed. RESULTS: Eighteen KPC-CRE infections were identified; median patient age was 16.5 years. Of 4 available KPC-CRE, 2 were unrelated, non-ST258 KP strains harboring blaKPC-2, one was a ST258 KP harboring blaKPC-3, and the last was an E. coli containing blaKPC-2. KPC-CRE and CSE-infected patients had more multidrug-resistant organisms infections, long-term care facility admissions and lengths of stay (LOS) > 7 days before culture. KPC-CRE and CSE patients had more gastrointestinal comorbidities (odds ratios [Ors], 28.0 and 6.4) and ≥ 3 comorbidities (Or 15.4 and 3.5) compared with controls; KPC-CRE patients had significantly more pulmonary and neurologic comorbidities (both ORs 4.4) or GI and pulmonary devices (ORs, 11.4 and 6.1). Compared with controls, CSE patients had more prior fluoroquinolone use (OR, 7.4); KPC-CRE patients had more carbapenem or aminoglycoside use (ORs, 10.0 and 8.0). Race, gender, LOS and mortality differences were insignificant. CONCLUSIONS: Pediatric patients with KPC-CRE infection suffer from high multi-system disease/device burdens and exposures to carbapenems and aminoglycosides. Different from adult reports, non-ST258 KP strains were more common, and LOS and mortality rates were similar in all groups. Pediatric CRE control in should focus on modifiable risk factors including antibiotic and device utilization.

Operation Homefront: Meeting Clerkship Competencies with Home Visits to Families of Children With Special Needs.

OBJECTIVE: We assessed how third-year medical students' written reflections on home visit experiences with families of children with special needs demonstrate evidence of exposure to 9 selected competencies for pediatric clerkships designated by the Council on Medical Student Education in Pediatrics. METHODS: We reviewed written reflections from 152 third-year medical students. For each competency (2 related to communication were combined), we tabulated the number of reflections in which a given competency was demonstrated. Within each competency, themes are described and presented with exemplary quotes to provide a more robust picture of students' exposure and experience. RESULTS: Of 152 reflections, 100% demonstrated at least 1 of the 8 expected competencies. Each reflection exhibited an average of 3 (3.1) competencies (range: 1-7). The competencies most frequently mentioned were demonstration of respect for patient, parent, and family attitudes, behaviors, and lifestyles (90%) and demonstration of positive attitude toward education (76%). Less frequently mentioned competencies included demonstration of behaviors and attitudes that promote patients' and families' best interests (41%), demonstration of effective verbal and nonverbal communication skills (a combination of 2 communication-related competencies) (33%), and description of barriers that prevent children from accessing health care (37%). The following competencies were least often mentioned: description of a pediatrician's role and responsibility in advocating for patients' needs (10%), description of the important role of patient education (8%), or description of the types of problems that benefit from a community approach (17%). CONCLUSIONS: Our analysis demonstrates that community-based home visits can provide medical students with opportunities to meet required pediatric clerkship competencies.

Aerococcus urinae as the Causative Agent in Infective Endocarditis of the Aortic Valve in a Pediatric Patient.

Aerococcus species were first described in 1953. They have been previously described as the causative agent of urinary tract infections in the elderly but rarely the causative agent for severe infections. However, there are very few cases reported in the pediatric population. To our knowledge, we report the first case of an adolescent with infective endocarditis caused by Aerococcus urinae.

Analysis of ß-Lactamase Resistance Determinants in Enterobacteriaceae from Chicago Children: a Multicenter Survey.

Multidrug-resistant (MDR) Enterobacteriaceae infections are increasing in U.S. children; however, there is a paucity of multicentered analyses of antibiotic resistance genes responsible for MDR phenotypes among pediatric Enterobacteriaceae isolates. In this study, 225 isolates phenotypically identified as extended-spectrum ß-lactamase (ESBL) or carbapenemase producers, recovered from children ages 0 to 18 years hospitalized between January 2011 and April 2015 at three Chicago area hospitals, were analyzed. We used DNA microarray platforms to detect ESBL, plasmid-mediated AmpC (pAmpC), and carbapenemase type ß-lactamase (bla) genes. Repetitive-sequence-based PCR and multilocus sequence typing (MLST) were performed to assess isolate similarity. Plasmid replicon typing was conducted to classify plasmids. The median patient age was 4.2 years, 56% were female, and 44% presented in the outpatient setting. The majority (60.9%) of isolates were Escherichia coli and from urinary sources (69.8%). Of 225 isolates exhibiting ESBL- or carbapenemase-producing phenotypes, 90.7% contained a bla gene. The most common genotype was the blaCTX-M-1 group (49.8%); 1.8% were carbapenem-resistant Enterobacteriaceae (three blaKPC and one blaIMP). Overall, pAmpC (blaACT/MIR and blaCMY) were present in 14.2%. The predominant E. coli phylogenetic group was the virulent B2 group (67.6%) associated with ST43/ST131 (Pasteur/Achtman MLST scheme) containing the blaCTX-M-1 group (84%), and plasmid replicon types FIA, FII, and FIB. K. pneumoniae harboring blaKPC were non-ST258 with replicon types I1 and A/C. Enterobacter spp. carrying blaACT/MIR contained plasmid replicon FIIA. We found that ß-lactam resistance in children is diverse and that certain resistance mechanisms differ from known circulating genotypes in adults in an endemic area. The potential impact of complex molecular types and the silent dissemination of MDR Enterobacteriaceae in a vulnerable population needs to be studied further.

The cry toxin operon of Clostridium bifermentans subsp. malaysia is highly toxic to Aedes Larval Mosquitoes.

The management and control of mosquito vectors of human disease currently rely primarily on chemical insecticides. However, larvicidal treatments can be effective, and if based on biological insecticides, they can also ameliorate the risk posed to human health by chemical insecticides. The aerobic bacteria Bacillus thuringiensis and Lysinibacillus sphaericus have been used for vector control for a number of decades. But a more cost-effective use would be an anaerobic bacterium because of the ease with which these can be cultured. More recently, the anaerobic bacterium Clostridium bifermentans subsp. malaysia has been reported to have high mosquitocidal activity, and a number of proteins were identified as potentially mosquitocidal. However, the cloned proteins showed no mosquitocidal activity. We show here that four toxins encoded by the Cry operon, Cry16A, Cry17A, Cbm17.1, and Cbm17.2, are all required for toxicity, and these toxins collectively show remarkable selectivity for Aedes rather than Anopheles mosquitoes, even though C. bifermentans subsp. malaysia is more toxic to Anopheles. Hence, toxins that target Anopheles are different from those expressed by the Cry operon.

Evolution of amoxicillin resistance of Helicobacter pylori in vitro: characterization of resistance mechanisms.

Helicobacter pylori is the major cause of peptic ulcers and gastric cancer in humans. Treatment involves a two or three drug cocktail, typically including amoxicillin. Increasing levels of resistance to amoxicillin contribute to treatment failures, and higher levels of resistance are believed to be due to multiple genetic mutations. In this study, we examined the progression of spontaneous genetic mutations that contribute to amoxicillin resistance in H. pylori when exposed to increasing concentrations of amoxicillin in vitro. During the selection process, we isolated five strains each of which had progressively higher levels of resistance. Using a whole genome sequencing approach, we identified mutations in a number of genes, notably pbp1, pbp2, hefC, hopC, and hofH, and by sequencing these genes in each isolate we were able to map the order and gradual accumulation of mutations in these isolates. These five isolates, each expressing multiple mutated genes and four transformed strains expressing individually mutated pbp1, hefC, or hofH, were characterized using minimum inhibitory concentrations, amoxicillin uptake, and efflux studies. Our results indicate that mutations in pbp1, hefC, hopC, hofH, and possibly pbp2 contribute to H. pylori high-level amoxicillin resistance. The data also provide evidence for the complexity of the evolution of amoxicillin resistance in H. pylori and indicate that certain families of genes might be more susceptible to amoxicillin resistance mutations than others.

The role of the Staphylococcal VraTSR regulatory system on vancomycin resistance and vanA operon expression in vancomycin-resistant Staphylococcus aureus.

Vancomycin is often the preferred treatment for invasive methicillin-resistant Staphylococcus aureus (MRSA) infection. With the increase in incidence of MRSA infections, the use of vancomycin has increased and, as feared, isolates of vancomycin-resistant Staphylococcus aureus (VRSA) have emerged. VRSA isolates have acquired the entercoccal vanA operon contained on transposon (Tn) 1546 residing on a conjugal plasmid. VraTSR is a vancomycin and ß-lactam-inducible three-component regulatory system encoded on the S. aureus chromosome that modulates the cell-wall stress response to cell-wall acting antibiotics. Mutation in vraTSR has shown to increase susceptibility to ß-lactams and vancomycin in clinical VISA strains and in recombinant strain COLVA-200 which expresses a plasmid borne vanA operon. To date, the role of VraTSR in vanA operon expression in VRSA has not been demonstrated. In this study, the vraTSR operon was deleted from the first clinical VRSA strain (VRS1) by transduction with phage harvested from a USA300 vraTSR operon deletion strain. The absence of the vraTSR operon and presence of the vanA operon were confirmed in the transductant (VRS1Δvra) by PCR. Broth MIC determinations, demonstrated that the vancomycin MIC of VRS1Δvra (64 µg/ml) decreased by 16-fold compared with VRS1 (1024 µg/ml). The effect of the vraTSR operon deletion on expression of the van gene cluster (vanA, vanX and vanR) was examined by quantitative RT-PCR using relative quantification. A 2-5-fold decreased expression of the vanA operon genes occured in strain VRS1Δvra at stationary growth phase compared with the parent strain, VRS1. Both vancomycin resistance and vancomycin-induced expression of vanA and vanR were restored by complementation with a plasmid harboring the vraTSR operon. These findings demonstrate that expression in S. aureus of the horizontally acquired enterococcal vanA gene cluster is enhanced by the staphylococcal three-component cell wall stress regulatory system VraTSR, that is present in all S. aureus strains.

Contribution of specific amino acid changes in penicillin binding protein 1 to amoxicillin resistance in clinical Helicobacter pylori isolates.

Amoxicillin is commonly used to treat Helicobacter pylori, a major cause of peptic ulcers, stomach cancer, and B-cell mucosa-associated lymphoid tissue lymphoma. Amoxicillin resistance in H. pylori is increasing steadily, especially in developing countries, leading to treatment failures. In this study, we characterize the mechanism of amoxicillin resistance in the U.S. clinical isolate B258. Transformation of amoxicillin-susceptible strain 26695 with the penicillin binding protein 1 gene (pbp1) from B258 increased the amoxicillin resistance of 26695 to equal that of B258, while studies using biotinylated amoxicillin showed a decrease in the binding of amoxicillin to the PBP1 of B258. Transformation with 4 pbp1 fragments, each encompassing several amino acid substitutions, combined with site-directed mutagenesis studies, identified 3 amino acid substitutions in PBP1 of B258 which affected amoxicillin susceptibility (Val 469 Met, Phe 473 Leu, and Ser 543 Arg). Homology modeling showed the spatial orientation of these specific amino acid changes in PBP1 from 26695 and B258. The results of these studies demonstrate that amoxicillin resistance in the clinical U.S. isolate B258 is due solely to an altered PBP1 protein with a lower binding affinity for amoxicillin. Homology modeling analyses using previously identified amino acid substitutions of amoxicillin-resistant PBP1s demonstrate the importance of specific amino acid substitutions in PBP1 that affect the binding of amoxicillin in the putative binding cleft, defining those substitutions deemed most important in amoxicillin resistance.

Pediatric antiretroviral therapy.

The rate of perinatal HIV transmission has decreased significantly in developed countries. However, worldwide, it remains the main source of HIV infection within the pediatric population. Recent advances as a result of findings from clinical trials, viral resistance testing and the advent of new drugs have increased the options for initial treatment regimens. This article provides an overview of antiretroviral therapy in treatment-naive children, including recent pediatric data and updated guidelines from the NIH. It also provides information on new drugs approved for the pediatric age group, dosage information, drug resistance testing and monitoring suggestions for children and adolescents receiving antiretroviral therapy. Special issues pertaining to adherence, disclosure and contraception are also highlighted.