Martin G. Ottolini

Utility of complete blood count and blood culture screening to diagnose neonatal sepsis in the asymptomatic at risk newborn.

Background. In May 1996, the CDC recommended obtaining a complete blood count and blood culture (BC) from all asymptomatic “at risk” newborns; those ≥35 weeks gestation born to mothers with group B streptococcal vaginal colonization or those with maternal fever, premature rupture of membranes or previous infant with group B streptococcal disease; who did not receive adequate intrapartum antibiotic prophylaxis. Design/methods. During the study period (May 1996 to July 1999), a complete blood count and BC were obtained within 4 h from all asymptomatic at risk newborns of ≥35 weeks gestation. White blood cell count (WBC) and BC results and prevalence of clinical or culture-proven sepsis were obtained by chart review. We determined the sensitivity/specificity and likelihood ratios of an abnormal WBC (total >30 000 or <5000/mm3; absolute neutrophil count <1500/mm3, or a band form-polymorphonuclear cell ratio of >0.2) to distinguish between clinically septic vs. nonseptic term at risk newborns. Results. Of 20 554 deliveries 1665 were initially asymptomatic at risk newborns; 17 (1.0%) developed early onset sepsis, all within 48 h. WBC was abnormal in 7 of 17 (41%) and in 447 of 1648 (27%) who remained nonseptic. None of the 1665 term at risk newborns had a positive BC. The sensitivity and specificity of an abnormal WBC in predicting which at risk newborns would develop sepsis were 41 and 73%, respectively. The positive likelihood ratio was 1.52, whereas the negative likelihood ratio was 0.81, with an odds ratio of 1.88. Conclusions. Since the implementation of the CDC guidelines for maternal intrapartum antibiotic prophylaxis, culture-proved sepsis has become rare at our institution. Although BC did not aid in the diagnosis of sepsis among asymptomatic at risk newborns, close observation in the first 24 h remained critically important.

Increasing clindamycin resistance among methicillin-resistant Staphylococcus aureus in 57 northeast United States military treatment facilities.

Background: Increasing community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has led many to use clindamycin for CA-MRSA disease, whereas others suggest caution because of inducible clindamycin resistance and rely on drugs such as trimethoprim-sulfamethoxazole (TMP-SMX). Aim: To analyze the change in antibiotic susceptibility pattern of S. aureus isolates from 2001 to 2004 in a closed health care system, a period during which clindamycin and TMP-SMX use increased 99 and 62%, respectively. Methods: S. aureus cultures from 57 military hospitals and clinics from 2001–2002 and 2003–2004 were compared for body site and antibiotic sensitivity, particularly the potentially inducible clindamycin-susceptible erythromycin-resistant pattern. A portion was evaluated by a double disk diffusion test (D test). Results: Numbers of S. aureus-positive cultures obtained from “wound” sites rose significantly in both pediatric (138 to 215, P < 0.001) and adult (715 to 972, P < 0.001) isolates, with a rise in MRSA in children (6 of 138 to 60 of 215, P < 0.001) and in adults (161 of 715 to 324 of 972, P < 0.001). Clindamycin resistance increased among pediatric S. aureus isolates (1 of 207 to 13 of 327, P < 0.05), whereas >96% remained TMP-SMX-susceptible. Five methicillin-susceptible S. aureus (MSSA), 2 MRSA of 41 pediatric and 36 MSSA, 43 MRSA of 437 adult S. aureus specimens were D test-positive. Conclusions: In late 2004, most S. aureus from our region are still β-lactam-susceptible. Most of the MRSA are still susceptible to clindamycin and do not appear to have inducible resistance. We must closely monitor the rates of constitutive and inducible clindamycin resistance as well as consider treatment alternatives that may slow the rate of clindamycin resistance.

Respiratory Syncytial Virus (RSV) Infection Induces Cyclooxygenase 2: A Potential Target for RSV Therapy

Cyclooxygenases (COXs) are rate-limiting enzymes that initiate the conversion of arachidonic acid to prostanoids. COX-2 is the inducible isoform that is up-regulated by proinflammatory agents, initiating many prostanoid-mediated pathological aspects of inflammation. The roles of cyclooxygenases and their products, PGs, have not been evaluated during respiratory syncytial virus (RSV) infection. In this study we demonstrate that COX-2 is induced by RSV infection of human lung alveolar epithelial cells with the concomitant production of PGs. COX-2 induction was dependent on the dose of virus and the time postinfection. PG production was inhibited preferentially by NS-398, a COX-2-specific inhibitor, and indomethacin, a pan-COX inhibitor, but not by SC-560, a COX-1-specific inhibitor. In vivo, COX-2 mRNA expression and protein production were strongly induced in the lungs and cells derived from bronchioalveolar lavage of cotton rats infected with RSV. The pattern of COX-2 expression in vivo in lungs is cyclical, with a final peak on day 5 that correlates with maximal histopathology. Treatment of cotton rats with indomethacin significantly mitigated lung histopathology produced by RSV. The studies described in this study provide the first evidence that COX-2 is a potential therapeutic target in RSV-induced disease.

Prevention and treatment recommendations for respiratory syncytial virus infection. Background and clinical experience 40 years after discovery.

SummaryThough 40 years have passed since its discovery, respiratory syncytial virus (RSV), one of the most ubiquitous viruses known, continues to evade most of our efforts to prevent or treat the clinical disease it causes. Long recognised as the most common cause of lower respiratory tract infections in virtually all children in the first 2 years of life, it has been increasingly recognised as a cause of more serious disease in several ‘high risk’ populations. These populations include infants with cardiac or pulmonary disease and infants and adults with immunodeficiencies, particularly those undergoing bone marrow transplantation.Early attempts to immunise children with a simple formalin-inactivated vaccine led to severe disease in vaccinated children who subsequently were infected with RSV from the community. Other vaccine constructs have failed for a variety of reasons, although surface glycoprotein subunit vaccines may hold promise. For years, ribavirin, a synthetic nucleoside analogue administered by constant aerosol, has been felt by many to lead to more rapid improvement in clinical disease caused by RSV, but it is still unclear whether its benefits are truly significant.An intravenous immunoglobulin product prepared from donors screened for the presence of high titres of RSV neutralising antibody (known as RSVIG) appears to be well tolerated and relatively effective in protecting high-risk infants against serious RSV disease, although therapeutic use has proven less dramatic. At least one monoclonal antibody undergoing current testing may prove easier to use in similar immunoprophylactic use. Results on the use of corticosteroids as supportive therapy have not been conclusive.In short, RSV will continue to be a challenge for clinicians and researchers well into the next century.

Antibody contributes to heterosubtypic protection against influenza A-induced tachypnea in cotton rats

BackgroundInfluenza virus infection or vaccination evokes an antibody response to viral hemagglutinin (HA) and neuraminidase (NA) surface glycoproteins, which results in immunity against influenza A viruses of the same HA and NA subtype. A heterosubtypic immune response that offers some protection against different influenza A subtypes has been suggested from epidemiologic studies in human influenza outbreaks, and has been induced in experimental animal models. Original studies of such cross-protection showed that cytotoxic T lymphocytes (CTL) protect H3N2-immune mice from a lethal H1N1 infection. More recent studies in mice demonstrate that antibodies also contribute to heterosubtypic immunity (HSI). We previously demonstrated that HSI in cotton rats (Sigmodon hispidus) is characterized by protection of H3N2-immune animals from influenza H1N1-induced increase in respiratory rate (tachypnea). Alternatively, H1N1-immune animals are protected from H3N2-induced tachypnea. The experiments described in this report were designed to elucidate the immune mechanism that prevents this very early sign of disease.ResultsOur results show that cotton rats provided with H1N1-immune serum prior to challenge with an H3N2 virus were protected from influenza-associated tachypnea, with the degree of protection correlating with the antibody titer transferred. Immunization with an inactivated preparation of virus delivered intramuscularly also provided some protection suggesting that CTL and/or mucosal antibody responses are not required for protection. Antibodies specific for conserved epitopes present on the virus exterior are likely to facilitate this protection since prophylactic treatment of cotton rats with anti-M2e (the extracellular domain of M2) but not anti-nucleoprotein (NP) reduced virus-induced tachypnea.ConclusionIn the cotton rat model of heterosubtypic immunity, humoral immunity plays a role in protecting animals from influenza-induced tachypea. Partial protection against respiratory disease caused by different influenza A subtypes can be attained with either live virus administered intranasally or inactivated virus delivered intramuscularly suggesting that either vaccine regimen may provide some protection against potential pandemic outbreaks in humans.

Delayed–type hypersensitivity skin testing in human immunodeficiency virus–infected pediatric patients

OBJECTIVE To evaluate whether pediatric patients infected with human immunodeficiency virus (HIV) can mount appropriate delayed-type hypersensitivity (DTH) skin responses to recall antigens and whether these responses can be correlated with clinical or immunologic parameters. DESIGN Prospective evaluation of DTH responses in HIV-infected children. Uninfected children born to HIV-infected mothers served as control subjects. Antigens used for yearly DTH testing included Candida albicans (1:100, 1:10); mumps virus; Trichophyton; purified protein derivative of tuberculin; and tetanus toxoid (1:100, 1:10). At the time of each DTH test, patients were staged according to two Centers for Disease Control and Prevention pediatric HIV classification systems, and T-cell subsets were obtained. RESULTS Twenty-seven HIV-infected patients with a median age at entry of 74.1 (range, 12 to 156) months were followed. Forty-four DTH skin tests in 21 symptom-free HIV-infected patients (PI) and 18 tests in 10 HIV-infected patients with symptoms (P2), as well as 43 DTH skin tests in 18 patients who had either mild or moderate clinical symptoms or immunosuppression and 19 tests in 13 patients with severe symptoms or immunosuppression, were evaluated. Sixteen DTH skin tests were performed in 14 uninfected patients. HIV-infected patients tended to have fewer DTH responses to antigens and of smaller size than did uninfected patients. When controlled for age, few differences in DTH responsiveness were seen between HIV-infected and uninfected patients. Anergy was associated with symptomatic disease, evidence of advanced clinical or immunologic disease, and low CD4+ percentages (p <0.05). CONCLUSIONS HIV-infected children are able to mount antigen-specific cell-mediated immune responses that are qualitatively similar to those of age-matched control subjects. Loss of DTH responsiveness correlates with both clinical and immunologic evidence of HIV disease progression.

The Role of Adenovirus in Respiratory Tract Infections

Adenovirus plays a significant role in respiratory tract disease in pediatric and adult patients. It has been linked to outbreaks and epidemics in various patient populations, resulting in considerable morbidity and mortality. In this article, we discuss the epidemiology, pathogenesis, respiratory tract illnesses and complications, and roles of potential treatment options. The role of the past oral adenovirus vaccine and the military implications of its withdrawal from routine use in military recruits is discussed as well.

Polymicrobial bloodstream infection in pediatric patients: risk factors, microbiology, and antimicrobial management.

Background: Few studies focus on polymicrobial bloodstream infections (PBSIs) in children. In previous reports, children with PBSI frequently had complex underlying medical conditions and a high incidence of specific microorganisms, but systematic evaluation with controls was not performed. We postulated that specific clinical risk factors are associated with an increased risk of PBSI, and that illness may be more severe with these infections. Additionally, we suspected that routine empiric antimicrobial therapy may frequently be inadequate to treat the variety of pathogens in PBSI. Methods: Positive blood cultures from 1998 to 2004 were reviewed. Patients whose cultures grew >1 organism were age-matched with monomicrobial bloodstream infection controls. Records were reviewed to compare their underlying medical conditions, organisms isolated, adequacy of therapy, and clinical characteristics of illness. Results: Twenty-nine episodes of PBSI were identified in 18 subjects. PBSI patients were more likely to have chronic medical conditions, chronic gastrointestinal pathology, central venous catheters, and to be receiving parenteral nutrition than controls. Pathogens found more commonly in PBSI episodes included Enterococcus spp., coagulase-negative staphylococci, and Candida spp. Empiric antimicrobial therapy was less likely to be adequate in patients with PBSI. PBSI patients were hospitalized longer, required longer intensive care and had prolonged bloodstream infection. Subjects with PBSI had prolonged duration of fever and had higher degrees of sepsis than controls. Conclusions: Chronic medical conditions, particularly gastrointestinal disease, are risk factors for PBSIs. Because clinical illness may be more severe, alteration of the empiric antimicrobial regimen should be considered in some of these patients.

A Cotton Rat Model of Human Parainfluenza 3 Laryngotracheitis: Virus Growth, Pathology, and Therapy

Parainfluenza virus type 3 (PIV3) infection led to laryngotracheitis in cotton rats. Laryngeal virus titers peaked at 10(5.0)-10(6.0) plaque-forming units (pfu)/g of tissue from days 2 through 5 after inoculation with 10(5.5) pfu of PIV3. Lymphocytic and neutrophilic inflammatory infiltrates were present in the subglottic and proximal tracheal regions, whereas respiratory epithelial cells were blunted with loss of cilia. Topical therapy with moderate doses of triamcinolone acetonide, an anti-inflammatory glucocorticoid, greatly reduced the extent of lesions. Interferon-gamma messenger RNA production was increased by infection and was suppressed by the highest dose of glucocorticoid. Topical glucocorticoid therapy, with or without concurrent topical immunotherapy with antibody to PIV3, did not lead to a rebound of viral replication.

Age-dependent replication of respiratory syncytial virus in the cotton rat.

Despite the documented disease burden of respiratory syncytial virus (RSV) in the elderly, little is known about the underlying risk factors or pathogenesis of RSV in a geriatric population. This report describes an age-dependent change of RSV clearance in the lung and nose of the cotton rat. Six days postinfection with RSV, lung and nose viral titers were significantly higher in all older age groups as compared with 4- to 6-week old cotton rats (P < 0.05). When comparing the 4- to 6-week old animals to the 15- to 16-month old animals 6 days postinfection, there was over an 800- and 100-fold increase in lung and nose viral titers, respectively. The cotton rat may prove to be a useful model in eliciting mechanisms of severe RSV disease in the elderly.