Mucormycosis in children with cancer and hematopoietic cell transplant-A single center cohort study

Although mucormycosis is an important cause of morbidity and mortality in children with cancer, our understanding of the typical characteristics of these infections is incomplete. We reviewed all cases of mucormycosis diagnosed at a single pediatric cancer center over 5 decades to identify the clinical features of mucormycosis in pediatric oncology patients and to identify risk factors for mortality. There were 44 cases of mucormycosis diagnosed between 1970-2019. Most patients (89%) had hematological malignancies and a history of prolonged and severe neutropenia (91%). In this series, hyperglycemia and exposure to corticosteroids were common. Pulmonary (36%) and disseminated infections (32%) were most common; rhino-orbital-cerebral infections were relatively infrequent (11%). Rhizopus spp. was the most common etiological agent (40%) followed by Mucor spp. (31%), and Cunninghamella spp. (19%). Overall mortality was 44% and 51% and attributable mortality was 39% and 41% at the end of antifungal therapy and end of follow up, respectively. Attributable mortality fell to 18% in 2010-2019, from 58-60% in previous decades; adjunctive surgery was associated with decreased mortality. Mortality remains unacceptably high despite aggressive antifungal therapy and adjunctive surgery, suggesting novel therapeutic strategies are needed.

Pediatric Infectious Diseases Milestones: A Step in the Right Direction to Evaluate Subspecialty Learners

We share the work of the ACGME Pediatric Infectious Diseases Working Group in creating the Pediatric Infectious Diseases-Specific Milestones and discuss key considerations that lead to the reformation of competencies to better assess learners in Pediatric Infectious Diseases.

Healthcare-Associated Infections Caused by Mycolicibacterium neoaurum

Mycolicibacterium neoaurum is a rapidly growing mycobacterium and an emerging cause of human infections. M. neoaurum infections are uncommon but likely underreported, and our understanding of the disease spectrum and optimum management is incomplete. We summarize demographic and clinical characteristics of a case of catheter-related M. neoaurum bacteremia in a child with leukemia and those of 36 previously reported episodes of M. neoaurum infection. Most infections occurred in young to middle-aged adults with serious underlying medical conditions and commonly involved medical devices. Overall, infections were not associated with severe illness or death. In contrast to other mycobacteria species, M. neoaurum was generally susceptible to multiple antimicrobial drugs and responded promptly to treatment, and infections were associated with good outcomes after relatively short therapy duration and device removal. Delays in identification and susceptibility testing were common. We recommend using combination antimicrobial drug therapy and removal of infected devices to eradicate infection.

A quality improvement initiative to increase Tdap (tetanus, diphtheria, acellular pertussis) vaccination coverage among direct health care providers at a children's hospital

OBJECTIVES

Health care providers (HCP) are at high risk of acquiring and transmitting pertussis to susceptible family members, co-workers, and patients. Public health authorities recommend administering a single dose of Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis) vaccine to all adults, including HCP, to increase adult immunity to pertussis. We set a quality improvement goal to increase Tdap vaccination coverage among HCP who provided direct patient care at a children's hospital from 58% to 90% over 18 months.

DESIGN

A multidisciplinary working group comprised of Occupational Health Program (OHP) staff and representatives of various medical services drew from a variety of qualitative methods and previous studies of vaccination programs in the healthcare system to understand barriers to Tdap vaccination within the institution and to develop interventions to increase vaccination rates.

INTERVENTIONS

Interventions included changes to OHP processes, a general education campaign, improved access to vaccine, and personal engagement of HCP by task force members.

RESULTS

Overall vaccination rates increased to 90% over 15 months, a rate that has been sustained by systematically assessing new employees' vaccination status and vaccinating those without documentation of previous Tdap vaccination.

CONCLUSIONS

Tdap vaccination coverage in our institution was significantly increased by an intensive, multipronged educational campaign, and by improving processes of screening and vaccination of HCP. The use of direct engagement of vaccine hesitant populations to increase vaccination rates warrants further study.

The Effectiveness of Trivalent Inactivated Influenza Vaccine in Children with Acute Leukemia

OBJECTIVE

The objective of this study was to determine the effectiveness of trivalent inactivated influenza vaccine (TIV) for the prevention of laboratory-confirmed influenza and influenza-like illnesses (ILI) among children and adolescents receiving therapy for acute leukemia.

STUDY DESIGN

A retrospective review of the demographic and clinical characteristics of 498 patients at a pediatric cancer center who received therapy for acute leukemia during 3 successive influenza seasons (2010-2011 through 2012-2013).

RESULTS

In 498 patient seasons with a known immunization history (median age, 6 years; range, 1-21), 354 patients (71.1%) were immunized with TIV and 98 (19.7%) received a booster dose of vaccine. Vaccinated and unvaccinated patients had generally similar demographic characteristics. There were no differences in the overall rates of influenza or ILI between vaccinated and unvaccinated patients overall, or in any individual season. There was no difference in the rates of influenza or ILI between patients who received 1 dose of vaccine and those who received 2 doses. Time to first influenza infection and time to first ILI in vaccinated and unvaccinated patients were not different.

CONCLUSION

TIV did not protect children and adolescents with acute leukemia against laboratory-confirmed influenza or ILI. Future prospective studies should assess TIV effectiveness in high-risk subpopulations and alternative strategies to prevent influenza should be considered in this population.

Epidemiology of Diarrheal Illness in Pediatric Oncology Patients

BACKGROUND

Diarrhea is common in children with cancer, but this has not been systematically studied to date.

METHODS

Remnant stool samples collected between January 2010 and June 2011 from pediatric oncology patients with diarrhea were tested for bacterial, viral, and parasitic enteropathogens using a combination of standard-of-care (SOC) diagnostic tests, including broad-range, real-time polymerase chain reaction (PCR) assays for adenoviruses, astroviruses, and sapoviruses and 2 commercially available multiplexed PCR assays. Corresponding demographic and clinical data were abstracted from patients' medical records.

RESULTS

One hundred fourteen episodes of diarrhea in 93 patients (median age, 3.7 years; range, 0.2-18.8) were included in the study. No patients died, but morbidity was significant. A total of 158 potential pathogens were detected in 114 diarrhea episodes, with >1 organism in one third of these; the most common were Clostridium difficile, noroviruses, adenoviruses, and astroviruses. Clostridium difficile, in combination with norovirus or adenovirus, was most common when >1 pathogen was detected. When both studies were obtained, SOC and broadly multiplexed PCR tests were concordant in 64 episodes (56%). Forty-five pathogens (28%) were identified retrospectively by broadly multiplexed PCR assays only. A total of 19 (13%) were detected by SOC real-time PCR assays but not by either commercially available multiplexed PCR assay.

CONCLUSIONS

Most pediatric oncology patients in this study had 1 or more potential infectious causes for their diarrhea. Additional studies are warranted to understand the natural history of gastroenteritis in this patient population. Although broadly multiplexed PCR assays offer some advantages over conventional testing, there may be disadvantages to their use for the diagnosis of infectious gastroenteritis that are unique to pediatric oncology patients.

Distinguishing Benign Mediastinal Masses from Malignancy in a Histoplasmosis-Endemic Region

OBJECTIVE

To describe the characteristics of benign and malignant mediastinal masses, which may predict their etiology and facilitate the safe and timely management of patients, especially those residing in histoplasmosis-endemic regions.

STUDY DESIGN

We conducted a retrospective review of the health records of 131 patients aged <19 years who were referred to 2 tertiary care children's hospitals between 2005 and 2010 for evaluation of mediastinal masses.

RESULTS

Most patients (79%) had benign masses, including 98 with confirmed or suspected histoplasmosis. Overall, compared with patients with malignant masses, patients with benign masses were younger and more likely to be African American, to complain of cough, and to have pulmonary nodules by chest computed tomography. In addition, patients with malignant disease were more likely to complain of malaise and to have neck swelling, abnormal extrathoracic lymphadenopathy, lymphopenia, anterior mediastinal involvement, and/or pleural effusion. Positive histoplasmosis serologic tests were specific but insensitive for a benign etiology. No single clinical, laboratory, or radiologic feature was sufficiently sensitive and specific for distinguishing between benign and malignant masses; however, the presence of lymphopenia, anterior mediastinal involvement, or enlarged cervical lymph nodes on computed tomography had a sensitivity of 93%, specificity of 95%, positive predictive value of 86%, and negative predictive value of 97% for cancer. Sixty-four patients (49%) underwent invasive testing, including 37 (36%) of those with benign masses.

CONCLUSION

Patients in this series who had involvement of the anterior mediastinum, lymphopenia, or enlarged cervical lymph nodes had a high likelihood of cancer. Expectant management of patients lacking these characteristics may be safe and reduce unnecessary invasive testing.

The Impact of Vaccine Concerns on Racial/Ethnic Disparities in Influenza Vaccine Uptake Among Health Care Workers

OBJECTIVES

We explored whether collective concerns about the safety, effectiveness, and necessity of influenza vaccines mediate racial/ethnic disparities in vaccine uptake among health care workers (HCWs).

METHODS

We used a self-administered Web-based survey to assess race/ethnicity (exposure), concerns about influenza vaccination (mediator; categorized through latent class analysis), and influenza vaccine uptake (outcome) for the 2012 to 2013 influenza season among HCWs at St. Jude Children's Research Hospital in Memphis, Tennessee. We used mediation analysis to estimate prevalence ratios (PRs) and 95% confidence intervals (CIs) for the total, direct, and indirect effects of race/ethnicity on influenza vaccine uptake.

RESULTS

Non-Hispanic Blacks had lower influenza vaccine uptake than non-Hispanic Whites (total effect: PR = 0.87; 95% CI = 0.75, 0.99), largely mediated by high concern about influenza vaccines (natural indirect effect: PR = 0.89; 95% CI = 0.84, 0.94; controlled direct effect: PR = 0.98; 95% CI = 0.85, 1.1). Hispanic and Asian HCWs had modestly lower uptake than non-Hispanic Whites, also mediated by high concern about influenza vaccines.

CONCLUSIONS

Racial/ethnic disparities among HCWs could be attenuated if concerns about the safety, effectiveness, and necessity of influenza vaccines were reduced.

Infections Caused by Rapidly Growing Mycobacteria spp in Children and Adolescents With Cancer

BACKGROUND

Rapidly growing mycobacteria (RGM) infections in pediatric oncology patients have not been completely characterized.

METHODS

We reviewed medical records of oncology patients at St. Jude Children's Research Hospital (St. Jude) from 1990 to 2010 with RGM infections and summarized the results of previously published cases.

RESULTS

Twenty-five St. Jude patients had 27 episodes of infection. Approximately half of the cases occurred in patients with hematological malignancies and in males; infections were more common in white patients. Most patients were not neutropenic or lymphopenic. The most common causative species were Mycobacterium chelonae, Mycobacterium abscessus, and Mycobacterium fortuitum. Most isolates were susceptible to amikacin and clarithromycin; all were susceptible to at least 1 of these. Treatment regimens varied considerably, particularly with respect to the duration of antimicrobial chemotherapy. Two St. Jude patients died; both had pulmonary infections. The literature search identified an additional 58 cases of infection. Localized catheter-associated infections were more common than bloodstream infections in the current series than in previous reports, and outbreaks were not recognized. Otherwise, the demographic and clinical characteristics of patients were similar.

CONCLUSIONS

Localized catheter-associated infections were most common in this largest reported single center experience reported to date. Pulmonary infection is uncommon in children but, as in adults, has a high mortality rate. Relatively short-term antimicrobial treatment and surgical debridement of infected tissue, if present, may be as effective for catheter-associated infections as prolonged antimicrobial use and may reduce adverse drug effects in these patients, who are vulnerable to drug-drug interactions and toxicity.

The safety of cefepime and ceftazidime in pediatric oncology patients

BACKGROUND

Concern has been raised about possible increased mortality associated with the use of cefepime. There are limited data available on the pragmatic use of beta-lactam antibiotics, especially in children.

PROCEDURE

This retrospective study included 532 pediatric oncology patients. The outcomes of patients treated with cefepime for suspected serious bacterial infections were compared to those of patients treated with ceftazidime. Primary outcomes included 30- and 90-day all-cause mortality.

RESULTS

The demographic and clinical characteristics of 337 patients treated with ceftazidime were similar to those of 195 patients receiving cefepime. Thirty-day and 90-day all cause mortality rates were comparable (30-day OR for cefepime: 3.48, 95% CI 0.31-38.84, P = 0.3; 90-day OR: 0.99, 95% CI 0.29-3.42, P = 1.0). There were also no differences in infection-related mortality rates, secondary infections, or adverse drug events. Deaths occurring within 30 days of hospitalization were judged to be attributable to infection, but not the result of treatment failure or adverse drug events. Deaths occurring between 30 and 90 days were associated with progressive or new malignancy. Secondary infection was significantly associated with mortality.

CONCLUSIONS

The use of cefepime in pediatric oncology patients is not associated with increased mortality when compared to ceftazidime, however the small number of deaths in this study limits the strength of this conclusion. Previous associations between antimicrobial therapy and increased all-cause mortality may have been confounded by patients' demographic characteristics and co-morbid conditions. All-cause mortality may be an insensitive outcome for studies examining the efficacy and safety of these agents.

Priming the immune system for heart disease: a perspective on group A streptococci

Although immune responses against group A streptococci and the heart have been correlated with antibodies and T cell responses against cardiac myosin, there is no unifying hypothesis about carditis caused globally by many different serotypes. Our study identified disease-specific epitopes of human cardiac myosin in the development of rheumatic carditis in humans. We found that immune responses to cardiac myosin were similar in rheumatic carditis among a small sample of worldwide populations, in which immunoglobulin G targeted human cardiac myosin epitopes in the S2 subfragment hinge region within S2 peptides containing amino acid residues 842-992 and 1164-1272. An analysis of rheumatic carditis in a Pacific Islander family confirmed the presence of potential rheumatogenic epitopes in the S2 region of human cardiac myosin. Our report suggests that cardiac myosin epitopes in rheumatic carditis target the S2 region of cardiac myosin and are similar among populations with rheumatic carditis worldwide, regardless of the infecting group A streptococcal M serotype.

Efficacy and safety of cefepime in pediatric patients: a systematic review and meta-analysis

OBJECTIVES

We systematically reviewed clinical trials on the safety and efficacy of cefepime in pediatric patients in view of recent reports, which suggested that cefepime is associated with increased 30-day all-cause mortality rates.

STUDY DESIGN

We searched the Cochrane Central Registry of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and other published and unpublished sources. Randomized clinical trials of cefepime in patients<19 years of age were selected.

RESULTS

Sixteen clinical trials were included. All-cause mortality rates did not differ between cefepime and comparator groups (risk difference, 0.00; 95% CI, -0.01-0.02). The risks of overall clinical failure (relative risk, 0.93; 95% CI, 0.82-1.04; P>.05) and failure in microbiologically confirmed infections (relative risk, 0.91; 95% CI, 0.68-1.22; P>.05) were not greater in subjects treated with cefepime. Rates of adverse events were similar in each group in all trials except 1. All studies had significant methodological flaws.

CONCLUSIONS

Comparisons of the safety and efficacy of cefepime relative with other antimicrobial agents in pediatric patients are limited by small numbers of trials and enrolled subjects and poor study methodology. This review, however, suggests that cefepime therapy in pediatric patients is not associated with an increased risk of adverse outcomes.

Zygomycosis originating from an odontogenic infection in a pediatric oncology patient

The Zygomyces are an increasingly frequent cause of invasive mold infection in immunocompromised patients. Here we describe the first well-documented case of Rhizopus infection of odontogenic origin, which presented as a rapidly progressive soft tissue infection in a neutropenic child. The infection resolved with limited surgical debridement and antifungal therapy.

Association between nutritional status and severity of dengue infection in children in El Salvador

Clinical observations and some studies suggest that dengue virus infection is more severe among children with better nutritional status. We examined the nutritional status of children in El Salvador and its relationship between this and the severity of dengue infection. Z-scores for weight-for-age, height-for-age, and body mass index (BMI)-for-age of children with dengue fever (66), dengue hemorrhagic fever (62), and healthy controls (74) were compared. There were no differences in weight-for-age or BMI-for-age Z-scores between the three groups. Children with dengue fever had a greater height-for-age than healthy controls but no significant differences in rates of stunting. There was no difference in height between children with dengue fever and dengue hemorrhagic fever. Excess nutrition does not appear to be a risk factor for severe forms of dengue infection in El Salvador, nor does malnutrition appear to be predictive of good outcomes.

L-Ficolin/mannose-binding lectin-associated serine protease complexes bind to group B streptococci primarily through N-acetylneuraminic acid of capsular polysaccharide and activate the complement pathway

Group B streptococci (GBS) are the most common cause of neonatal sepsis and meningitis. Most infants who are colonized with GBS at birth do not develop invasive disease, although many of these uninfected infants lack protective levels of capsular polysaccharide (CPS)-specific antibody. The lectin pathway of complement is a potential mechanism for initiating opsonization of GBS with CPS-specific antibody-deficient serum. In this study, we determined whether mannose-binding lectin (MBL)/MBL-associated serine protease (MASP) complexes and L-ficolin/MASP complexes bind to different strains of GBS to activate the lectin pathway, and we identified the molecules recognized by lectins on the GBS surface. We found that MBL did not bind to any GBS examined, whereas L-ficolin bound to GBS cells of many serotypes. L-ficolin binding to GBS cells correlated with the CPS content in serotypes Ib, III (restriction digestion pattern types III-2 and III-3), and V but not with the group B-specific polysaccharide (GBPS) content or with the lipoteichoic acid (LTA) content. L-ficolin bound to purified CPS and GBPS in a concentration-dependent manner but not to purified LTA. All strains to which L-ficolin/MASP complexes bound consumed C4. When N-acetylneuraminic acid (NeuNAc) was selectively removed from GBS cells by treatment with neuraminidase, the reduction in L-ficolin binding was correlated with the amount of NeuNAc removed. Additionally, L-ficolin was able to bind to wild-type strains but was able to bind only weakly to unencapsulated mutants and a mutant strain in which the CPS lacks NeuNAc. We concluded that L-ficolin/MASP complexes bind to GBS primarily through an interaction with NeuNAc of CPS.

Failure of viridans group streptococci causing bacteremia in pediatric oncology patients to express superantigens

Group A Streptococcus pyogenes causes a distinctive clinical disorder, streptococcal toxic shock syndrome, mediated by superantigenic bacterial exotoxins. Oncology patients with viridans group streptococcal sepsis frequently present with a streptococcal toxic shocklike syndrome of unclear pathogenesis. Viridans group streptococci isolated from pediatric oncology patients with streptococcal toxic shocklike illnesses do not possess homologs of known superantigen genes. Supernatants from cultures of these bacteria also fail to stimulate T-cell proliferation, suggesting these bacteria do not commonly elaborate superantigens. Adjunctive treatment with intravenous immunoglobulin, which is advantageous in streptococcal toxic shock syndrome, may not benefit these patients.

A unique serine-rich repeat protein (Srr-2) and novel surface antigen (epsilon) associated with a virulent lineage of serotype III Streptococcus agalactiae

Group B streptococci (GBS) are pathogens of both neonates and adults, with serotype III strains in particular being associated with invasive disease and meningitis. In this study, a novel GBS surface antigen, epsilon, was found to be co-expressed with the previously reported delta antigen on an identical subset of serotype III GBS. Expression of delta/epsilon on the surface of serotype III GBS was shown to distinguish the restriction digest pattern (RDP) III-3 and multilocus sequence typing (ST)-17 lineage. epsilon-Specific antibodies were reactive with a unique, high-molecular-mass, serine-rich repeat protein (Srr-2) found exclusively in RDP III-3 strains. The gene encoding Srr-2 was located within a putative accessory secretory locus that included secY2 and secA2 homologues and had a genetic organization similar to that of the secY2/A2 locus of staphylococci. In contrast, serotype III delta/epsilon-negative strains and strains representative of serotypes Ia, Ib, Ic and II shared a common Srr-encoding gene, srr-1, and an organization of the secY2/A2 locus similar to that of previously reported serotype Ic, delta/epsilon-negative serotype III and serotype V GBS strains. Representative serotype III delta/epsilon-positive strains had LD(90) values 3-4 logs less than those of serotype III delta/epsilon-negative strains in a neonatal mouse model of infection. These results indicate that the RDP III-3/ST-17 lineage expresses Srr-2 and is highly virulent in an in vivo model of neonatal sepsis.

Regulation of Apoptosis by Gram-Positive Bacteria: Mechanistic Diversity and Consequences for Immunity

Apoptosis, or programmed cell death (PCD), is an important physiological mechanism, through which the human immune system regulates homeostasis and responds to diverse forms of cellular damage. PCD may also be involved in immune counteraction to microbial infection. Over the past decade, the amount of research on bacteria-induced PCD has grown tremendously, and the implications of this mechanism on immunity are being elucidated. Some pathogenic bacteria actively trigger the suicide response in critical lineages of leukocytes that orchestrate both the innate and adaptive immune responses; other bacteria proactively prevent PCD to benefit their own survival and persistence. Currently, the microbial virulence factors, which represent the keys to unlocking the suicide response in host cells, are a primary focus of this field. In this review, we discuss these bacterial "apoptosis regulatory molecules" and the apoptotic events they either trigger or prevent, the host target cells of this regulatory activity, and the possible ramifications for immunity to infection. Gram-positive pathogens including Staphylococcus, Streptococcus, Bacillus, Listeria, and Clostridia species are discussed as important agents of human infection that modulate PCD pathways in eukaryotic cells.

Respiratory viruses augment the adhesion of bacterial pathogens to respiratory epithelium in a viral species- and cell type-dependent manner

Secondary bacterial infections often complicate respiratory viral infections, but the mechanisms whereby viruses predispose to bacterial disease are not completely understood. We determined the effects of infection with respiratory syncytial virus (RSV), human parainfluenza virus 3 (HPIV-3), and influenza virus on the abilities of nontypeable Haemophilus influenzae and Streptococcus pneumoniae to adhere to respiratory epithelial cells and how these viruses alter the expression of known receptors for these bacteria. All viruses enhanced bacterial adhesion to primary and immortalized cell lines. RSV and HPIV-3 infection increased the expression of several known receptors for pathogenic bacteria by primary bronchial epithelial cells and A549 cells but not by primary small airway epithelial cells. Influenza virus infection did not alter receptor expression. Paramyxoviruses augmented bacterial adherence to primary bronchial epithelial cells and immortalized cell lines by up-regulating eukaryotic cell receptors for these pathogens, whereas this mechanism was less significant in primary small airway epithelial cells and in influenza virus infections. Respiratory viruses promote bacterial adhesion to respiratory epithelial cells, a process that may increase bacterial colonization and contribute to disease. These studies highlight the distinct responses of different cell types to viral infection and the need to consider this variation when interpreting studies of the interactions between respiratory cells and viral pathogens.

Nontypeable Haemophilus influenzae adheres to intercellular adhesion molecule 1 (ICAM-1) on respiratory epithelial cells and upregulates ICAM-1 expression

Nontypeable Haemophilus influenzae (NTHI) is an important respiratory pathogen. NTHI initiates infection by adhering to the airway epithelium. Here, we report that NTHI interacts with intracellular adhesion molecule 1 (ICAM-1) expressed by respiratory epithelial cells. A fourfold-higher number of NTHI bacteria adhered to Chinese hamster ovary (CHO) cells transfected with human ICAM-1 (CHO-ICAM-1) than to control CHO cells (P < or = 0.005). Blocking cell surface ICAM-1 with specific antibody reduced the adhesion of NTHI to A549 respiratory epithelial cells by 37% (P = 0.001) and to CHO-ICAM-1 cells by 69% (P = 0.005). Preincubating the bacteria with recombinant ICAM-1 reduced adhesion by 69% (P = 0.003). The adherence to CHO-ICAM-1 cells of NTHI strains deficient in the adhesins P5, P2, HMW1/2, and Hap or expressing a truncated lipooligosaccharide was compared to that of parental strains. Only strain 1128f-, which lacks the outer membrane protein (OMP) P5-homologous adhesin (P5 fimbriae), adhered less well than its parental strain. The numbers of NTHI cells adhering to CHO-ICAM-1 cells were reduced by 67% (P = 0.009) following preincubation with anti-P5 antisera. Furthermore, recombinant ICAM bound to an OMP preparation from strain 1128f+, which expresses P5, but not to that from its P5-deficient mutant, confirming a specific interaction between ICAM-1 and P5 fimbriae. Incubation of respiratory epithelial cells with NTHI increased ICAM-1 expression fourfold (P=0.001). Adhesion of NTHI to the respiratory epithelium, therefore, upregulates the expression of its own receptor. Blocking interactions between NTHI P5 fimbriae and ICAM-1 may reduce respiratory colonization by NTHI and limit the frequency and severity of NTHI infection.

Mechanisms of group B streptococcal-induced apoptosis of murine macrophages

Apoptosis of murine and human macrophages induced by group B Streptococcus agalactiae (GBS) is likely an important virulence mechanism that is used by the bacteria to suppress the host immune response and to persist at sites of infection. The mechanisms by which GBS induces apoptosis are, however, largely unknown. In this study, we report that in murine macrophages GBS induces unique changes in the regulation and localization of the apoptotic regulators Bad, 14-3-3, and Omi/high-temperature requirement A2 and leads to the release of cytochrome c and the activation of caspase-9 and caspase-3. Furthermore, inhibition of caspase-3 impaired GBS-induced apoptosis of macrophages. The ability to modulate the activity of effector caspases may therefore represent an unexploited avenue for therapeutic intervention in GBS infections.

Infections in children and young adults with bone malignancies undergoing limb-sparing surgery

BACKGROUND

The epidemiology, risk factors, and efficacy of therapy for infections complicating limb-sparing surgery (LSS) are not understood completely.

METHODS

The authors conducted a retrospective review of children and adolescents with bone malignancies who underwent LSS.

RESULTS

One hundred three patients underwent 104 LSS procedures. Patients experienced a median of 4 infections (range, 0-13 infections), including focal bacterial infections in 67% of patients and bacteremia in 21% of patients. Infections at the LSS site occurred in 26% of patients, and 21% of patients developed orthopedic device infections (ODIs). Compared with patients without ODIs, patients who developed ODIs were more likely to be African American and to have wound infections, and they were less likely to have tumors of the femur than the tibia. In a multivariate analysis, only African-American race and local infection at the LSS site retained a significant association with ODIs. Among survivors, patients who developed ODIs were more likely to undergo amputation (odds ratio [OR], 24.0; 95% confidence interval [95%CI], 5.1-114.0; P < 0.001) and were less likely to have good functional outcomes (OR, 0.02; 95%CI, 0.002-0.15; P < 0.001) compared with patients who did not have an ODI. Overall, only 1 of 22 patients with an ODI was treated successfully without removal of the orthopedic device or amputation.

CONCLUSIONS

Current treatment for bone malignancies is complicated by an unexpectedly high incidence of infection. ODI was the most common reason for amputation and poor functional outcomes. The identification of risk factors for ODI may allow modifications of therapy that reduce the incidence and severity of infection, but prevention of all ODIs will require novel strategies.

Nitric Oxide Is a Key Determinant of Group B Streptococcus–Induced Murine Macrophage Apoptosis

Group B streptococcus (GBS; Streptococcus agalactiae) induces apoptosis of macrophages, and this may be an important mechanism GBS uses to suppress immune responses. The mechanisms whereby GBS induces apoptosis have not been identified. We studied GBS infection in murine macrophage-like J774A.1 cells and analyzed gene expression before apoptosis. Tumor necrosis factor (TNF)-alpha , interleukin (IL)-1, and inducible nitric oxide synthase (iNOS) gene expression coincided with apoptosis. Inhibition of iNOS gene expression by use of N(G)-monomethyl-L-arginine (NMMA) inhibited apoptosis, whereas inhibition of TNF-alpha and IL-1 biological activity did not. Macrophages from congenic iNOS-deficient mice were less susceptible to apoptosis than were macrophages from C57BL/6 mice. The NO donor S-nitroso-N-acetylpenicillamine (SNAP) induced apoptosis without infection, confirming its proapoptotic effect. NMMA did not impair the microbicidal activity of macrophages, however, and SNAP was not bactericidal against GBS in vitro. In human monocyte-derived macrophages (HMDMs), NO production was minimal, even after costimulation with IFN-gamma and lipopolysaccharide. Dose-dependent apoptosis of HMDMs occurred without a significant NO response. Thus, NO is an important mediator of GBS-induced murine macrophage apoptosis but does not contribute to antimicrobial activity or cytotoxicity in HMDMs. HMDMs and murine macrophages are killed by GBS by alternative, NO-independent mechanisms. Future studies of host-cell machinery commandeered by GBS to bring about apoptosis will be important for understanding the role played by apoptosis in defense against this important human pathogen.

Myositis complicating viridans streptococcal sepsis in childhood leukemia

Hematogenous focal infections are a rare complication of bacteremia or sepsis caused by viridans-group streptococci. We describe two patients with acute leukemia who developed myositis during alpha-hemolytic streptococcal bacteremia. Children complaining of severe muscle pain associated with viridans streptococcal infections should be carefully evaluated for the presence of focal pyogenic complications and rhabdomyolysis. The severity of infectious myositis is highly variable, depending on the etiologic organism and host immunity, making individualized treatment the most effective approach.

Role of L-ficolin/mannose-binding lectin-associated serine protease complexes in the opsonophagocytosis of type III group B streptococci

Serotype III group B streptococci (GBS) are a common cause of neonatal sepsis and meningitis. Although deficiency in maternal capsular polysaccharide (CPS)-specific IgG correlates with susceptibility of neonates to the GBS infection, serum deficient in CPS-specific IgG mediates significant opsonophagocytosis. This IgG-independent opsonophagocytosis requires activation of the complement pathway, a process requiring the presence of both Ca(2+) and Mg(2+), and is significantly reduced by chelating Ca(2+) with EGTA. In these studies, we defined a role of L-ficolin/mannose-binding lectin-associated serine protease (MASP) complexes in Ca(2+)-dependent, Ab-independent opsonophagocytosis of serotype III GBS. Incubation of GBS with affinity-purified L-ficolin/MASP complexes and C1q-depleted serum deficient in CPS-specific Ab supported opsonophagocytic killing, and this killing was inhibited by fluid-phase N-acetylglucosamine, the ligand for L-ficolin. Binding of L-ficolin was proportional to the CPS content of individual strains, and opsonophagocytic killing and C4 activation were inhibited by fluid-phase CPS, suggesting that L-ficolin binds to CPS. Sialic acid is known to inhibit alternative complement pathway activation, and, as expected, the bactericidal index (percentage of bacteria killed) for individual strains was inversely proportional to the sialic acid content of the CPS, and L-ficolin-initiated opsonophagocytic killing was significantly increased by addition of CPS-specific IgG2, which increased activation of the alternative pathway. We conclude that binding of L-ficolin/MASP complexes to the CPS generates C3 convertase C4b2a, which deposits C3b on GBS. C3b deposited by this lectin pathway forms alternative pathway C3 convertase C3bBb whose activity is enhanced by CPS-specific IgG2, leading to increased opsonophagocytic killing by further deposition of C3b on the GBS.

Serotype III Streptococcus agalactiae from bovine milk and human neonatal infections

Although largely unrelated, many bovine type III GBS appear to share a common ancestor with an important human clone.

Streptococcus agalactiae (group B streptococcus [GBS]) causes invasive human infections and bovine mastitis. This study examined the genetic relationship between bovine and human serotype III GBS by using molecular techniques that classify human serotype III GBS into four distinct phylogenetic lineages. Bovine serotype III GBS were largely contained in two lineages, which are distinct from the two major lineages (restriction digest types III-2 and III-3) that infect human neonates. One of the bovine lineages closely resembles the human III-1 lineage, whose members occasionally cause human neonatal infections. The bovine strains in the other lineage characteristically have an initiation factor IF2 gene (infB) H allele and multilocus sequence types that are not found in human GBS strains. Evidence suggests that this “H allele” lineage is related to the human III-3 lineage. These results support the assertion that human and bovine GBS are largely unrelated and provide further insight into the genetic relation between human and bovine GBS.

Equivalence of high-virulence clonotypes of serotype III group B Streptococcus agalactiae (GBS)

Analysis of growth characteristics, multilocus enzyme electrophoresis, restriction digest pattern (RDP) typing and multilocus sequence typing have identified clonotypes of serotype III group B Streptococcus agalactiae (GBS) associated with invasive infection in neonates. This study sought to unify phenotypic and genotypic classifications of type III GBS strains associated with increased virulence in newborns. High-virulence clonotype (HVC) strains possessed the translation initiation factor 2 (infB) C allele, found in RDP type III-3 strains, and hybridized with the RDP type III-3-specific probe AA3.6, whereas non-HVC strains shared the infB A allele and genomic DNA from these strains did not hybridize with the AA3.6 probe. The characteristic growth lag of HVC GBS at 40 degrees C has been attributed to the presence of a heat-labile fructose-1,6-bisphosphate aldolase (Fba) enzyme in these strains. The deduced amino acid sequence of fba genes of both HVC and non-HVC strains, however, were identical. HVC and RDP type III-3 represent the same genetically related group of bacteria. The characteristic growth differences of virulent strains of type III GBS, however, are not directly attributable to differences in fba.

Subtractive hybridization identifies a novel predicted protein mediating epithelial cell invasion by virulent serotype III group B Streptococcus agalactiae

Group B Streptococcus agalactiae bacteria (group B streptococci [GBS]) are the most common cause of serious bacterial infection in newborn infants. The majority of serotype III-related cases of neonatal disease are caused by a genetically related subgroup of bacteria, restriction fragment digest pattern (RDP) type III-3, suggesting that these strains possess unique genes contributing to virulence. We used genomic subtractive hybridization to identify regions of genomic DNA unique to virulent RDP type III-3 GBS strains. Within one of these III-3-specific regions is a 1,506-bp open reading frame, spb1 (surface protein of group B streptococcus 1). A mutant type III GBS strain lacking Spb1 was constructed in virulent RDP type III-3 strain 874391, and the interactions of the wild-type and spb1 isogenic mutant with a variety of epithelial cells important to GBS colonization and infection were compared. While adherence of the spb1 isogenic mutant to A549 respiratory, C2Bbe1 colonic, and HeLa cervical epithelial cells was slightly lower than that of the 874391 strain, invasion of the Spb1(-) mutant was significantly reduced with these cell lines compared to what was seen with 874391. The defect in epithelial invasion was corrected by supplying spb1 in trans. These observations suggest that Spb1 contributes to the pathogenesis of neonatal GBS infection by mediating internalization of virulent serotype III GBS and confirm that understanding of the population structure of bacteria may lead to insights into the pathogenesis of human infections.

Histoplasmosis in a pediatric oncology center

OBJECTIVE

To understand the presentation and current management of histoplasmosis in a pediatric oncology center. Study design Retrospective review of clinical features of patients with histoplasmosis at a tertiary-care cancer center in an endemic area.

RESULTS

Between 1988 and 2001, 57 patients with cancer had 61 episodes of acute histoplasmosis. Of these, 76% were male, and 64% had acute lymphocytic leukemia (ALL). Most were not neutropenic and had nonspecific febrile illnesses. The most rapid and specific tests for histoplasmosis in patients with cancer were histopathologic examination of lung biopsy specimens in patients with localized pulmonary infection and Histoplasma sp. antigen detection in the urine of patients with disseminated histoplasmosis (DH). The mean times to diagnosis were 20.6+/-15.2 days (pulmonary) and 18.6+/-8.2 days (disseminated) after the onset of symptoms. Most patients were treated with amphotericin B (AmB) followed by azole drugs for a mean of 8.5+/-3.1 weeks (pulmonary) and 10.4+/-7.9 weeks (disseminated). No patient died of histoplasmosis, but cancer therapy often was modified because of the infection. Most received unnecessary antibacterial drugs.

CONCLUSIONS

Most readily available diagnostic tests for histoplasmosis lack sensitivity in these patients. Delay in diagnosis of histoplasmosis complicates care. No deaths were attributed to histoplasmosis; outcomes after treatment are good.

β‐Hemolysin–Independent Induction of Apoptosis of Macrophages Infected with Serotype III Group B Streptococcus

Group B streptococcus (GBS) induces apoptosis in macrophages. Growth conditions minimizing beta-hemolysin expression, such as high glucose, reduce apoptosis. We constructed an isogenic mutant strain of GBS 874391 lacking the beta-hemolysin structural gene cylE and investigated the role that beta-hemolysin plays in apoptosis of J774 macrophages. Viability of macrophages infected with wild-type or cylE GBS was similar and significantly less than that of macrophages infected with GBS grown in high-glucose media. Thus, apoptosis in GBS-infected macrophages is dependent not on beta-hemolysin but on a factor coregulated with beta-hemolysin by glucose.

Invasive disease due to nontypeable Haemophilus influenzae among children in Arkansas

In this study, we reviewed cases of invasive disease due to nontypeable Haemophilus influenzae among children hospitalized at Arkansas Children's Hospital from 1993 to 2001. A total of 28 cases were examined, including 21 associated with bacteremia and 4 associated with meningitis. Of the patients examined, 86% were Collapse

Key Words Collapse

MESH Headings

• Adolescent
• Arkansas/epidemiology
• Bacteremia/epidemiology
• Bacteremia/microbiology
• Bacterial Proteins/genetics
• Blotting, Southern
• Child
• Child, Preschool
• Electrophoresis, Gel, Pulsed-Field
• Female
• Genetic Variation
• Genotype
• Haemophilus Infections/epidemiology
• Haemophilus Infections/microbiology
• Haemophilus influenzae/classification
• Haemophilus influenzae/genetics
• Hospitalization
• Humans
• Infant
• Infant, Newborn
• Male
• Sequence Analysis, DNA

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Grants

• R01 AI049322 NIAID NIH HHS
• CA023944-20 NCI NIH HHS
• R01-AI44167 NIAID NIH HHS
• R25 CA023944 NCI NIH HHS
• R01 DC002873 NIDCD NIH HHS
• P30 CA21765 NCI NIH HHS
• R01-AI49322 NIAID NIH HHS
• P30 CA021765 NCI NIH HHS
• R01 AI044167 NIAID NIH HHS
• R01-DC02873 NIDCD NIH HHS

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Affiliation(s)

Joshua M O'Neill Department of Pediatrics, University of Arkansas for Medical Sciences/Arkansas Children's Hospital, Little Rock, Arkansas, USA.
Joseph W St Geme
David Cutter
Elisabeth E Adderson
Juliana Anyanwu
Richard F Jacobs
Gordon E Schutze

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Pgi genotyping is a surrogate for serotyping of encapsulated Haemophilus influenzae

Study of the epidemiology of invasive infections caused by encapsulated Haemophilus influenzae has been complicated by the poor sensitivity and specificity of the serologic assays used to identify specific capsular polysaccharides. The population structure of these bacteria is highly clonal, however, and serotype is highly correlated with other genetic characteristics. We sought to determine if alleles of the highly conserved phosphoglucose isomerase (pgi) gene correspond to the serotypes of encapsulated H. influenzae strains. pgi alleles of 52 well-characterized encapsulated H. influenzae isolates were amplified by PCR, sequenced, and compared to one another and to additional previously reported H. influenzae pgi alleles. Overall, 83% of the strains possessed pgi alleles associated with the major serotype a, b, e, and f clonotypes that cause the most invasive disease in the United States. Six strains (four type a and two type f) had unusual pgi alleles, which suggested that these strains belonged to less common clonotypes of encapsulated bacteria or were actually nontypeable strains. pgi genotyping may provide a simple and stable surrogate for capsular serotyping. Further studies correlating pgi typing with the expression of capsule are likely to increase our understanding of the epidemiology and pathogenesis of these infections.

Prevalence and distribution of adhesins in invasive non-type b encapsulated Haemophilus influenzae

Adhesion to the respiratory epithelium plays an important role in Haemophilus influenzae infection. The distribution of H. influenzae adhesins in type b and nontypeable strains has been characterized, but little is known about the prevalence of these factors in non-type b encapsulated strains. We analyzed 53 invasive type a, type e, and type f strains for the presence of hap, hia, hmw, and hif genes; Hap, Hia, and HMW1/2 adhesins; and hemagglutinating pili. The hap gene was ubiquitous, and homologs of hmw and hia were present in 7 of 53 (13.2%) and 45 of 53 (84.9%) strains, respectively. Hap was detected in 28 of 45 (62.2%) hap(+) strains, HMW1/2 was detected in 5 of 7 (71.4%) hmw(+) strains, and Hia was detected in 31 of 45 (68.8%) hia(+) strains. The hif gene cluster was present in 26 of 53 strains (49.1%), and 21 of 26 hif(+) strains (80.8%) agglutinated (HA) red blood cells. Nine isolates exhibited HA but lacked the hif gene cluster. The distribution of adhesin genes correlated with the genetic relatedness of the strains. Strains belonging to one type a clonotype and the major type e clonotype possessed hia but lacked the hif cluster. Strains belonging to the second type a clonotype possessed both hia and hif genes. All type f strains belonging to the major type f clonotype possessed hia and lacked hifB. Although the specific complement of adhesin genes in non-type b encapsulated H. influenzae varies, most invasive strains express Hap and Hia, suggesting these adhesins may be especially important to the virulence of these organisms.

Correlation of phylogenetic lineages of group B Streptococci, identified by analysis of restriction-digestion patterns of genomic DNA, with infB alleles and mobile genetic elements

Phylogenetic lineages of pathogenic Streptococcus agalactiae (group B streptococci [GBS]) can be identified by analysis of restriction-digestion patterns (RDPs) of chromosomal DNA. The purpose of the present study was to correlate GBS RDP types and (1) alleles of the highly conserved gene encoding translation-initiation factor IF2, infB, and/or (2) the inserted elements IS1548 and GBSi1. Only 1 combination of serotype and infB allele was found within each RDP type. Strains within a particular RDP type also tend to have the same inserted elements in each of 3 loci examined. A novel insertion sequence, designated "IS1563," was found within all RDP type II-2 strains. Most RDP types could be identified by a combination of serotype, infB allele, and inserted elements at each of the loci. These molecular markers can be used to identify GBS populations and to correlate RDP types and phylogenetic lineages identified by different methods.

Limited genetic diversity of recent invasive isolates of non-serotype b encapsulated Haemophilus influenzae

Invasive infections caused by non-type b encapsulated Haemophilus influenzae have increased in frequency in the last decade. This change prompted us to characterize the genetic relationships of 48 recently isolated invasive H. influenzae type a (Hia), e (Hie), and f (Hif) strains by comparison of restriction digest patterns (RDPs). Recent Hia isolates exhibited moderate genetic diversity, with the majority segregating into two major clonotypes. Recent Hie and, especially, Hif strains displayed considerably restricted genetic diversity. In particular, all but one Hif strain segregated into a single clonotype, and half of these isolates had identical RDPs. These results are consistent with the hypothesis that the increased incidence of disease due to non-type b encapsulated H. influenzae reflects the emergence of hypervirulent clones, especially in the case of Hif. Alternatively, it is possible that non-type b encapsulated H. influenzae strains have limited overall genetic diversity.

Long-range mapping of the Streptococcus agalactiae phylogenetic lineage restriction digest pattern type III-3 reveals clustering of virulence genes

Human isolates of serotype III Streptococcus agalactiae (group B streptococcus [GBS]) can be divided into three separate phylogenetic lineages based on analysis of the restriction digest patterns (RDPs) of chromosomal DNA. Nine DNA sequences that are present in all isolates of the RDP III-3 phylogenetic lineage, but not in the other lineages, were identified by genomic subtractive hybridization. A complete physical map of a III-3 chromosome was constructed. Six of the nine III-3-specific sequences mapped to a 340-kb Sse8387I fragment which contains or is located close to known GBS virulence genes. One of the III-3-specific probes, AW-10, encodes part of GBSi1, a group II intron that is inserted at two sites within the GBS genome. The second chromosomal site for GBSi1 was isolated, sequenced, and mapped to a location near the locus responsible for hemolysin production. These findings suggest that the genetic variation that distinguishes the RDP type III-3 strains from other serotype III strains occurs largely within localized areas of the genome containing known or putative virulence genes.

Antibody repertoires in infants and adults: effects of T-independent and T-dependent immunizations

Polysaccharide(PS)-encapsulated bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis are among the most prevalent bacterial pathogens of humans. Infections caused by these organisms are both common (otitis media, sinusitis) and severe (meningitis, bacteremia). Antibodies directed against the capsular PS of encapsulated bacteria prevent infection by promoting opsonophagocytic killing. Most bacterial PS, however, are type II T-cell-independent (TI-2) antigens that are poorly immunogenic in young children at highest risk of developing disease. Conjugation of bacterial PS to a protein carrier converts the immune response to a T-cell-dependent (TD) form and significantly improves the immunogenicity of PS, especially in infants. H. influenzae type b (Hib) is a major cause of invasive infection in non-immune children. The medical importance of this pathogen and the availability of both TI-2 and TD Hib PS vaccine formulations have made the human anti-Hib-PS immune response an excellent model for the study of the biology of these B cell responses.

Capsulation loci of non-serotype b encapsulated Haemophilus influenzae

Invasive infections caused by non-type b encapsulated Haemophilus influenzae have increased recently. Because capsule is a major virulence factor, capsulation of 62 recently isolated non-serotype b encapsulated strains was examined. Repeated serotyping confirmed only 69.0% of isolates. The combination of slide agglutination and cap genotyping confirmed 78.9% of type a, 100% of type e, and 86.4% of type f strains. Seven nonencapsulated strains may have lost capsulation through homologous recombination. Three strains that could not be serotyped or genotyped failed to hybridize with any cap probe and are probably nontypeable H. influenzae. Of isolates that retained an intact cap locus, 62.2% had evidence of cap amplification. The epidemiology of non-type b encapsulated H. influenzae infections is complicated by the poor specificity of available serologic reagents and by spontaneous capsule loss. Recently isolated invasive non-type b encapsulated H. influenzae frequently have cap amplification, which may contribute to their virulence.

Invasive serotype a Haemophilus influenzae infections with a virulence genotype resembling Haemophilus influenzae type b: emerging pathogen in the vaccine era?

OBJECTIVE

Haemophilus influenzae type b causes severe disease in nonimmune infants and young children; other serotypes are uncommon pathogens and thought to have low virulence. Some have hypothesized that with the virtual elimination of H influenzae type b, other serotypes might acquire virulence traits and emerge as important pathogens of children. We describe the clinical, epidemiologic, and molecular biologic features of 5 cases of severe disease attributable to Haemophilus influenzae type a.

METHODS

After observing 4 cases of invasive disease caused by H influenzae type a, we reviewed microbiology records at 3 reference laboratories that perform all serotyping in Utah and surveillance databases. Strains of H influenzae type a and control strains were examined by Southern blotting with the use of the cap probe pUO38 and by pulsed-field gel electrophoresis. The putative virulence mutation, the IS1016-bexA deletion, was detected by polymerase chain reaction amplification and sequencing.

RESULTS

During a 10-month period, we observed 5 children with severe invasive disease caused by H influenzae type a. No isolates of H influenzae type a had been submitted to the reference laboratories between 1992 and 1998. The median age of patients was 12 months (range: 6-48 months). Four of 5 had meningitis and bacteremia; 1 had purpura fulminans. Three isolates, representing 1 of 2 pulsed-field gel electrophoresis patterns, contained the IS1016-bexA deletion and were associated with particularly severe disease.

CONCLUSIONS

We describe an unusual cluster of severe disease caused by H influenzae type a that resembles the clinical and epidemiologic features of H influenzae type b disease. Our data support the hypothesis that the IS1016-bexA deletion may identify more virulent strains of H influenzae. Haemophilus influenzae, epidemiology, virulence, serotyping, pathogenicity.

Phylogenetic classification of serotype III group B streptococci on the basis of hylB gene analysis and DNA sequences specific to restriction digest pattern type III-3

Previous work divided serotype III group B streptococci (GBS) into 3 major phylogenetic lineages (III-1, III-2, and III-3) on the basis of bacterial DNA restriction digest patterns (RDPs). Most neonatal invasive disease was caused by III-3 strains, which implies that III-3 strains are more virulent than III-2 or III-1 strains. In the current studies, all RDP III-3 and III-1 strains expressed hyaluronate lysase activity; however, all III-2 strains lack hyaluronate lysase activity, because the gene that encodes hyaluronate lysase, hylB, is inactivated by IS1548. Subtractive hybridization was used to identify 9 short DNA sequences that are present in all the III-3 strains but not in any of the III-2 or III-1 strains. With 1 exception, these III-3-specific sequences were not detected in nonserotype III GBS. These data further validate the RDP-based subclassification of GBS and suggest that lineage-specific genes will be identified, which account for the differences in virulence among the lineages.

Growth failure, intracranial calcifications, acquired pancytopenia, and unusual humoral immunodeficiency: a genetic syndrome?

We report on two children who may represent a novel syndrome consisting of a deficiency of immunoglobulin-bearing B lymphocytes and serum antibody, deficient intrauterine and/or postnatal growth, intracranial calcifications, and acquired pancytopenia. Poor growth, intracranial calcifications, developmental delay, and hematological abnormalities are common manifestations of congenital infection. However, humoral immunodeficiency is not characteristic in these infections, and no infection was found on extensive evaluation. Rare genetic syndromes may mimic intrauterine infections and may also include immunodeficiency. However the children reported here lack important characteristics or share distinctive manifestations not described in these disorders. Infants presenting with apparent congenital infections in whom a specific infectious cause cannot be identified should be followed carefully with immunological evaluations since this disorder may be progressive and considerable morbidity is attributable to hematological and immunological manifestations.

Molecular analysis of cross-reactive anti-myosin/anti-streptococcal mouse monoclonal antibodies

Nucleotide sequences of VH- and VL-genes of anti-myosin/anti-streptococcal monoclonal antibodies (mAbs) were analyzed and compared with their highly detailed antigen binding reactivities. Antigen-specificities of the cross-reactive mAbs included myosin, streptococcal M-protein, actin, keratin, N-acetyl-beta-D-glucosamine, vimentin, DNA, tropomyosin, troponin, and laminin as previously described. After nucleotide sequence analysis, homology indicated that some of the V gene sequences aligned with antibodies recognizing gangliosides and blood group antigens glycophorin M and N. Therefore, mAb reactivity with gangliosides and glycophorin M and N was identified. The cross-reactive mAbs utilized a heterogeneous group of germline V-heavy genes comprised of nine J558-, four 7183- and two Q52-family VH-genes. Germline V-light genes utilized by the mAbs included six Vkappa4/5-, three Vkappa8-, two Vkappa10-, three Vkappa19- and one Vkappa23-family VL-genes. No preferential VH/VL-chains correlated with any of the 12 different antigen reactivities, even for mAbs with nearly identical cross-reactivities. However, we did find that the cross-reactive mAb germline genes within a V gene family shared more homology among themselves than with other germline genes within their V gene families, suggesting convergent mutation. Cross-reactive mAbs with the highest relative avidity for myosin were found in the VH7183 family which contained two cytotoxic mAbs. Antibodies with V gene sequences most homologous to those of our cross-reactive anti-myosin/anti-streptococcal mAbs had specificities for laminin, DNA, carbohydrates, or blood group antigens and were reported to cause autoimmune disease in mice.

Bacterial genetics and human immunity to group B streptococci

Serotype III group B Streptococcus agalactiae (GBS) are the most common cause of neonatal sepsis and meningitis. We have classified type III GBS by restriction digest patterns of chromosomal DNA and demonstrated that a subgroup of genetically related strains (RDP type III-3) causes the majority of type III GBS neonatal infection. Genetic differences between type III GBS strains contribute significantly to differences in virulence and host immune responses. While 100% of less virulent RDP type III-1 and III-2 organisms express C5a-ase, an inhibitor of neutrophil chemotaxis, only 63% of virulent RDP type III-3 isolates have functional C5a-ase. Functional differences in type III GBS C5a-ase are attributable to a shared genetic polymorphism, supporting our genetic classification. The mean capsular sialic acid content of virulent RDP type III-3 strains is significantly higher than that of less virulent strains, suggesting that capsular sialylation is also genetically regulated. C5a-ase is not critical for all RDP type III-3 strains to be invasive because the higher capsular sialic acid content of III-3 strains limits complement activation. The identification of these and additional genetic differences between GBS strains has important implications for our understanding of the pathogenesis of these important human infections.

Genetic polymorphisms of group B streptococcus scpB alter functional activity of a cell-associated peptidase that inactivates C5a

Many group B Streptococcus agalactiae strains and other pathogenic streptococci express a cell-associated peptidase that inactivates C5a (C5a-ase), the major neutrophil chemoattractant produced by activation of the complement cascade. Type III group B streptococci (GBS) can be classified genotypically into three restriction digest pattern types. Functional C5a-ase activity of GBS correlates with this genetic typing; therefore, we sought to identify a genetic basis for this phenomenon. Southern hybridization confirms that all type III GBS contain scpB, the gene encoding GBS C5a-ase. GBS strains with high C5a-ase functional activity and those with no or very low activity both express immunoreactive C5a-ase. The scpB sequence of strain I30, which has high C5a-ase activity, is 98.2% homologous to the previously reported serotype II GBS scpB sequence. The scpB sequences of strains I25 and GW, which have low or no C5a-ase activity, are identical. The predicted I25 and GW C5a-ase proteins share a four-amino-acid deletion affecting the protease histidine active-site consensus motif. Recombinant I30 C5a-ase has good functional activity, whereas recombinant I25 C5a-ase has low activity. These data demonstrate that functional C5a-ase differences between type III GBS strains are attributable to a genetic polymorphism of scpB. The ubiquitous expression of C5a-ase, irrespective of functional activity, suggests that C5a-ase may have a second, as yet unidentified, function.

Bacillus cereus infections among oncology patients at a children's hospital

BACKGROUND

Bacillus cereus can cause severe infections in immunocompromised persons.

METHODS

We report 3 cases of bacteremia/septicemia (1 fatal) among oncology patients in a children's hospital. Because all cases occurred during a 10-day period, a common source outbreak was suspected. An epidemiologic investigation was performed. Molecular comparison of patient and environmental isolates was performed by using pulsed-field gel electrophoresis.

RESULTS

After an extensive investigation, no common hospital source could be found. Pulsed-field gel electrophoresis proved that the isolates were not related.

CONCLUSION

Sporadic infections in immunocompromised persons do occur and can be associated with significant morbidity.