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Anaplasma phagocytophilum (AP) is the causative agent of human granulocytic anaplasmosis (HGA), a tick-borne illness with highest incidence in north-eastern regions of the United States. This condition presents with vague constitutional symptoms and has been associated with laboratory derangements such as leukopenia, thrombocytopenia and transaminitis1. Rhabdomyolysis, however, is not one of these associations. We report a case of confirmed HGA associated with severe rhabdomyolysis, where no other cause was identified. The etiology of rhabdomyolysis secondary to AP infection is still unknown. A presumptive diagnosis of HGA can be made in the presence of fever, non-specific symptoms such as myalgias, laboratory derangements such as leukopenia and thrombocytopenia in an individual residing in an endemic area3. Serological confirmation should not delay treatment, given the rapid progression of this dangerous infection. Rhabdomyolysis should also be considered as part of supporting data in the diagnostic consideration for HGA., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Bone marrow suppression is an adverse effect associated with many antibiotics, especially when administered for prolonged treatment courses. Recent advances in our understanding of steady-state hematopoiesis have allowed us to explore the effects of antibiotics on hematopoietic progenitors in detail using a murine model. Antibiotic-treated mice exhibited anemia, thrombocytosis, and leukopenia, with pronounced pan-lymphopenia as demonstrated by flow cytometric analysis of peripheral blood. Bone marrow progenitor analysis revealed depletion of hematopoietic stem cells and multipotent progenitors across all subtypes. Granulocytes and B cells were also diminished in the bone marrow, whereas the number of CD8 + T cells increased. Reductions in progenitor activity were not observed when cells were directly incubated with antibiotics, suggesting that these effects are indirect. Hematopoietic changes were associated with a significant contraction of the fecal microbiome and were partially rescued by fecal microbiota transfer. Further, mice raised in germ-free conditions had hematopoietic abnormalities similar to those seen in antibiotic-treated mice, and antibiotic therapy of germ-free mice caused no additional abnormalities. The effects of antibiotics were phenocopied in Stat1-deficient mice, with no additional suppression by antibiotics in these mice. We conclude that microbiome depletion as a result of broad-spectrum antibiotic treatment disrupts basal Stat1 signaling and alters T-cell homeostasis, leading to impaired progenitor maintenance and granulocyte maturation. Methods to preserve the microbiome may reduce the incidence of antibiotic-associated bone marrow suppression., (© 2017 by The American Society of Hematology.)

Background: Stroke-induced immunodeficiency increases the risk of infectious complications, which adversely affects neurological outcome. Among those, pneumonia affects as many as one third of stroke patients and is the main contributor to mortality in the post-acute phase of stroke. Experimental findings on post-stroke susceptibility to spontaneous pneumonia in mice are contradictory. Here, we established a mouse model inducing standardized bacterial pneumonia and characterized the impaired pulmonary cellular and humoral immune responses after experimental stroke., Methods: Bacterial pneumonia was induced by intra-tracheal inoculation with Streptococcus pneumoniae at different time points after transient middle cerebral artery occlusion (MCAO). Bacterial counts in lungs and blood, histological changes, and cytokine production in the lungs were assessed. Furthermore, we investigated the effect of pneumonia on stroke outcome., Results: Intra-tracheal inoculation resulted in reproducible pneumonia and bacteraemia, and demonstrated post-stroke susceptibility to streptococcal pneumonia developing with a delay of at least 24 h after MCAO. Higher bacterial counts in mice infected 3 days after stroke induction correlated with reduced neutrophil and macrophage infiltration in the lungs and lower levels of pro-inflammatory cytokines in the broncho-alveolar lavage compared to sham-operated animals. Pneumonia increased mortality without affecting brain-infiltrating leukocytes., Conclusions: In this standardized mouse model of post-stroke pneumonia, we describe attenuated leukocyte infiltration and cytokine production in response to bacterial infection in the lungs that has a profound effect on outcome., (© 2017 S. Karger AG, Basel.)

Although liver involvement is frequently seen in brucellosis, acute hepatitis is a rare clinical entity. In its progress, haematological findings are non-specific and vary in respect to severity. In this paper, we present a case of brucellosis with acute hepatitis and bicytopenia without anaemia. A 19-year-old man presented with a 2-week history of fever, sweating, low back and leg pain, lassitude, loss appetite, nausea and vomiting. He gave a history of raw milk ingestion and animal contact. Physical examination showed signs of icteric skin and sclera, tenderness in the right hypochondriac region and hepatosplenomegaly. On admission to hospital, laboratory tests showed WBC 3500/mmc (polymorphs 63% and lymphocytes 33%), haemoglobin 13.8 g/dL, platelet 89000/mmc, erythrocyte sedimentation rate 19 mm/h, and C-reactive protein 21.7 mg/dL (N<0.8 mg/dL). Biochemical tests were as follows: AST 771 U/L, ALT 471 U/L, ALP 355 U/L, GGT 432 U/L, total bilirubin 2.61 mg/dL, direct bilirubin 1.45 mg/dL and albumin 3.7 g/dL. Viral hepatitis markers were found to be negative (HBsAg, anti-HBc total, anti-HBc IgM, anti-HAV IgM, and anti-HCV). Blood culture grew Brucella melitensis. Leukopenia and thrombocytopenia returned to normal levels at the 7th and 14th day of his admission, respectively. Liver function tests improved at the 28th day. Treatment of the brucellosis was performed with antibiotics (tetracycline 500 mg orally four times daily for 6 weeks and streptomycin 1 g IM once daily for 21 days). Finally, a case of brucellosis with acute hepatitis and bicytopenia was treated with a successful outcome. In conclusion, we suggest that due consideration be taken of bicytopenia/pancytopenia and acute hepatitis in brucellosis cases in Turkey, an endemic region.

Background and Objectives: Carboxypeptidase B2 (CPB2) is a basic carboxypeptidase with fibrin and complement C3a and C5a as physiological substrates. We hypothesized that in polymicrobial sepsis, CPB2-deficient mice would have sustained C5a activity, leading to disease exacerbation., Methods: Polymicrobial sepsis was induced by cecal ligation and puncture (CLP)., Results: Contrary to our hypothesis, Cpb2(-/-) mice had significantly improved survival, with reduced lung edema, less liver and kidney damage, and less disseminated intravascular coagulation. Hepatic pro-CPB2 was induced by CLP, leading to increased pro-CPB2 levels. Thrombomodulin present on mesothelium supported thrombin activation of pro-CPB2. Both wild-type and Cpb2(-/-) animals treated with a C5a receptor antagonist had improved survival, demonstrating that C5a was detrimental in this model. Treatment with a fibrinolysis inhibitor, tranexamic acid, caused a decrease in survival in both genotypes; however, the Cpb2(-/-) animals retained their survival advantage. Administration of a C3a receptor antagonist exacerbated the disease in both wild-type and Cpb2(-/-) mice and eliminated the survival advantage of Cpb2(-/-) mice. C5a receptor is expressed in both peritoneal macrophages and neutrophils; in contrast, C3a receptor expression is restricted to peritoneal macrophages, and C3a induced signaling in macrophages but not neutrophils., Conclusions: While C5a exacerbates the peritonitis, resulting in a deleterious generalized inflammatory state, C3a activation of peritoneal macrophages may limit the initial infection following CLP, thereby playing a diametrically opposing protective role in this polymicrobial sepsis model., (© 2015 International Society on Thrombosis and Haemostasis.)

Background: The diagnosis of ventilator-associated pneumonia (VAP) in our institution has followed an established diagnostic threshold (DT) of equal to or greater than 10 colony-forming units (CFU) per milliliter on bronchoalveolar lavage (BAL) based on our previous study (PS). Because mortality from VAP is related to treatment delay, some have advocated a lower DT. The purpose of the current study (CS) was to evaluate the impact of adherence to this DT for VAP on false-negative (FN) rates and mortality in trauma patients., Methods: Consecutive patients over 9 years with VAP (defined as ≥10 CFU/mL in the BAL effluent) subsequent to the PS were identified. Data regarding each BAL performed and the colony counts of each organism identified were recorded. An FN BAL result was defined as any patient who had less than 10 CFU/mL and developed VAP with the same organism up to 7 days after the previous culture. The CS was then compared with the PS., Results: Over 9 years, 1,679 patients underwent 3,202 BALs. Of these, 79% were male, 88% experienced blunt injury, mean age and Injury Severity Score (ISS) were 44 years and 31, respectively. Overall, there were 73 FN BAL results (2.3%) in the CS compared with 3% in the PS (p = 0.092). In those patients with 10 organisms, the FN rate was reduced (7.5% vs. 11%, p = 0.045), and mortality was unchanged (5.4% vs. 8.3%, p = 0.361) in the CS compared with the PS. The use of the threshold equal to or greater than 10 resulted in a cumulative reduction in antibiotic charges of $1.57 million., Conclusion: Continued adherence to the diagnostic threshold of equal to or greater than 10 for quantitative BAL in trauma patients has maintained a low incidence of FN BALs and reduced patient charges without impacting mortality. The purported benefit of a lower threshold is not supported. In addition, the potential sequelae of increased resistant organisms, antibiotic-related complications, and costs associated with prolonged unnecessary antibiotic exposure are minimized., Level of Evidence: Prognostic study, level III.

Background: Necrotizing pneumonia attributed to Panton-Valentine leukocidin-positive Staphylococcus aureus has mainly been reported in otherwise healthy children and young adults, with a high mortality rate. Erythroderma, airway bleeding, and leukopenia have been shown to be predictive of mortality. The objectives of this study were to define the characteristics of patients with severe leukopenia at 48-h hospitalization and to update our data regarding mortality predicting factors in a larger population than we had previously described., Methods: It was designed as a case-case study nested in a cohort study. A total of 148 cases of community-acquired, necrotizing pneumonia were included. The following data were collected: basic demographic information, medical history, signs and symptoms, radiological findings and laboratory results during the first 48 h of hospitalization. The study population was divided into 2 groups: (1) with severe leukopenia (leukocyte count ≤3,000 leukocytes/mL, n=62) and (2) without severe leukopenia (>3,000 leukocytes/mL, n=86)., Results: Median age was 22 years, and the male-to-female gender ratio was 1.5. The overall in-hospital mortality rate was 41.2%. Death occurred in 75.8% of severe leukopenia cases with median survival time of 4 days, and in 16.3% of cases with leukocyte count >3,000/mL (P<0.001). Multivariate analysis indicated that the factors associated with severe leukopenia were influenza-like illness (adjusted odds ratio (aOR) 4.45, 95% CI (95% confidence interval) 1.67-11.88, P=0.003), airway bleeding (aOR 4.53, 95% CI 1.85-11.13, P=0.001) and age over 30 years (aOR 2.69, 95% CI 1.08-6.68, P=0.033). A personal history of furuncles appeared to be protective (OR 0.11, 95% CI 0.01-0.96, P=0.046)., Conclusion: S. aureus-necrotizing pneumonia is still an extremely severe disease in patients with severe leukopenia. Some factors could distinguish these patients, allowing better initial identification to initiate adapted, rapid administration of appropriate therapy.

Objective: To describe clinical findings and the use of a tick-associated pathogen panel in a series of patients with human granulocytic anaplasmosis (HGA) at a suburban Boston hospital., Patients and Methods: Medical records were reviewed for inpatients and outpatients at Newton-Wellesley Hospital with a positive polymerase chain reaction (PCR) result for Anaplasma phagocytophilum during the study period March 1 through November 30, 2009. A PCR panel was used to test for tick-borne pathogens. Postal ZIP code data from the patients' areas of residence were used to estimate the area of disease transmission., Results: Thirty-three cases were confirmed during the 2009 transmission season, and 14 of these patients (42%) required hospitalization. Thrombocytopenia and/or leukopenia were observed at the time of presentation in 25 of 30 patients (86%) in whom both white blood cell and platelet counts were determined, and 28 of 33 patients (85%) reported fever. Rash occurred in only 2 of the 33 patients (6%), and 25 (76%) reported one or more respiratory or gastrointestinal symptom. Cases were geographically distributed diffusely throughout the hospital catchment area, with one possible focus of infection identified in Weston, MA. Due to a lack of clinical data reporting to the Massachusetts Department of Public Health, only 20 of 32 HGA cases (63%) fulfilled the case confirmation criteria., Conclusion: Diagnosis of HGA requires a high suspicion for infection even in endemic areas. Use of a tick-associated pathogen panel that includes PCR assays for several organisms could improve detection of underrecognized tick-borne diseases in endemic areas. Lack of epidemiological follow-up to confirm corroborating clinical findings prevents accurate case reporting and assessment of the true HGA burden., (Copyright © 2012 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.)

Community-acquired pneumonia (CAP) is a common and potentially serious illness with significant human and economic costs to society. The recent collaborative statement from the Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) represents the most up-to-date evidence-based guidelines from North America, incorporating important advances in the management of patients with CAP. The cases presented in this review highlight many of the recent recommendations from the IDSA/ATS guidelines., (Copyright 2010 Elsevier Inc. All rights reserved.)

Pathology data from the anthrax animal models show evidence of significant increases in vascular permeability coincident with hemostatic imbalances manifested by thrombocytopenia, transient leucopenia, and aggressive disseminated intravascular coagulation. In this study we hypothesized that anthrax infection modulates the activity of von Willebrand factor (VWF) and its endogenous regulator ADAMTS13, which play important roles in hemostasis and thrombosis, including interaction of endothelial cells with platelets. We previously demonstrated that purified anthrax neutral metalloproteases Npr599 and InhA are capable of cleaving a variety of host structural and regulatory proteins. Incubation of human plasma with these proteases at 37 degrees C in the presence of urea as a mild denaturant results in proteolysis of VWF. Also in these conditions, InhA directly cleaves plasma ADAMTS13 protein. Npr599 and InhA digest synthetic VWF substrate FRETS-VWF73. Amino acid sequencing of VWF fragments produced by InhA suggests that one of the cleavage sites of VWF is located at domain A2, the target domain of ADAMTS13. Proteolysis of VWF by InhA impairs its collagen binding activity (VWF:CBA) and ristocetin-induced platelet aggregation activity. In plasma from anthrax spore-challenged DBA/2 mice, VWF antigen levels increase up to 2-fold at day 3 post-infection with toxigenic Sterne 34F(2) strain, whereas VWF:CBA levels drop in a time-dependent manner, suggesting dysfunction of VWF instead of its quantitative deficiency. This conclusion is further supported by significant reduction in the amount of VWF circulating in blood in the ultra-large forms. In addition, Western blot analysis shows proteolytic depletion of ADAMTS13 from plasma of spore-challenged mice despite its increased expression in the liver. Our results suggest a new mechanism of anthrax coagulopathy affecting the levels and functional activities of both VWF and its natural regulator ADAMTS13. This mechanism may contribute to hemorrhage and thrombosis typical in anthrax.

Background: The use of quantitative cultures of the bronchoalveolar lavage (BAL) effluent to distinguish between posttraumatic inflammatory response and ventilator-associated pneumonia (VAP) is becoming more common. However, the diagnostic threshold of either 10 or 10 colonies/mL remains debatable. Because mortality from VAP is related to treatment delay, some have chosen a lower diagnostic threshold (>10 colonies/mL). This may result in unnecessary antibiotic use with its sequelae: increased resistant organisms, antibiotic-related complications, and increased costs. The purpose of this study is to determine the optimal diagnostic threshold for VAP diagnosis using quantitative cultures of the BAL effluent., Methods: Data on patients with fiberoptic bronchoscopy with BAL are maintained in a prospectively collected database at our Level I trauma center. This database was reviewed for timing and frequency of BAL and the colony counts of each organism identified. Indication for bronchoscopy was clinical evidence of VAP. VAP was defined as >10 colonies/mL in the BAL effluent. A false-negative BAL was defined as any patient who had <10 colonies/mL and developed VAP with the same organism up to 7 days after the previous culture., Results: Over a 46-month period, 526 patients underwent 1,372 fiberoptic bronchoscopy procedures with BAL. Of these, 72% were male patients, 91% followed blunt injury, and mean age and Injury Severity Score were 43 years and 30, respectively. Overall mortality was 14%. There were 1,898 organisms identified (42% were gram-positive and 58% were gram-negative). VAP was diagnosed in 38% of BAL. Overall, there were 43 episodes in 38 patients defined as false-negative (3%). The false-negative rate was 9% in patients with 10 organisms. The most common false-negative organisms were Pseudomonas and Acinetobacter species., Conclusion: The VAP diagnostic threshold for quantitative BAL in trauma patients should be >10 colonies/mL. One may consider a threshold of >10 colonies/mL in severely injured patients with Pseudomonas or Acinetobacter species.

We evaluated the virulence of Pseudomonas aeruginosa carrying bla(IMP), a metallo-beta-lactamase gene, and the efficacy of ceftazidime, imipenem-cilastatin, and ciprofloxacin in the endogenous bacteremia model. The presence of bla(IMP) did not practically change the virulence of the parent strain, and ciprofloxacin was effective against infection with P. aeruginosa carrying bla(IMP).

BAL5788 is a water-soluble prodrug of BAL9141, a new broad-spectrum cephalosporin with high levels of in vitro activity against methicillin- and vancomycin-resistant staphylococci and penicillin-resistant streptococci. In plasma BAL5788 is rapidly converted to BAL9141. We studied the activity of BAL5788 in a mouse model of acute pneumococcal pneumonia. Leukopenic female Swiss albino mice were challenged intratracheally with 10(7) CFU of clinical Streptococcus pneumoniae strains P-52181 (Pen(s) Cro(s) Ctx(s)), P-15986 (Pen(r) Cro(s) Ctx(s)), P-40422 (Pen(r) Cro(r) Ctx(r)), and P-40984 (Pen(r) Cro(r) Ctx(r)). Infected mice received subcutaneous (s.c.) injections of BAL5788 or ceftriaxone starting 3 h after pneumococcal challenge. Uninfected nonleukopenic mice received single s.c. doses of BAL5788 to determine the BAL9141 concentration-time profiles in serum and lungs. Untreated control mice died within 5 days postinfection. Ten-day cumulative survival rates for infected mice receiving BAL5788 (total daily doses of BAL9141 equivalents, 2.1 to 75 mg/kg of body weight) ranged from 57 to 100%, whereas with ceftriaxone (total daily doses, 10 to 400 mg/kg), the survival rates varied between 13 and 100%. In mice infected with P-15986, the survival rates achieved with BAL5788 (BAL9141 equivalent, 8.4 mg/kg) and those achieved with ceftriaxone (50 mg/kg) were significantly different (93 versus 13%; P < 0.0001) in favor of BAL5788; the outcomes of the trials with all other strains were not significantly different between the two antibiotics, but markedly lower doses of BAL5788 than ceftriaxone were required to obtain similar survival rates. Pharmacokinetic data showed that BAL9141 was effective against the four pneumococcal strains tested at very low values of the time above the MIC (T > MIC), which ranged from 9 to 18% of the dosing interval, whereas the values of T > MICs for ceftriaxone ranged from 30 to 50% of the dosing interval.

Objectives: The efficacy of intravenous injections of a liposomal formulation of amphotericin B (AmBisome) and amphotericin B deoxycholate (Fungizone) was evaluated in immunocompetent and temporarily leucopenic mouse models of disseminated aspergillosis using seven isolates of Aspergillus., Methods: Mice were infected with the organisms via tail veins. At 4 h after infection, antifungals were administered intravenously. For 30 days the number of mice surviving was recorded., Results: AmBisome at 1 mg/kg or higher significantly prolonged the survival time of mice infected with five out of seven isolates of Aspergillus compared with the control group. There was no difference in in vivo activity between AmBisome and Fungizone at 1 mg/kg in six isolates of Aspergillus. At the maximum tolerated dose of antifungals, however, AmBisome (10 mg/kg) showed greater efficacy than Fungizone (1 mg/kg)., Conclusions: These results suggest that the overall protective activity of AmBisome against disseminated aspergillosis is superior to that of Fungizone.

Severe illness with acute renal failure, leukopenia, thrombocytopenia, and coagulopathy frequently occurs with hemolytic uremic syndrome/thrombotic thrombocytopenic purpura, hematological malignancies, sepsis, and collagen-vascular diseases. We present a 16-year-old male fast-food worker with underlying chronic renal insufficiency who manifested these abnormalities as a result of Ehrlichia chaffeensis sepsis. Doxycycline therapy and aggressive supportive care led to complete recovery.

The agent of human granulocytic ehrlichiosis (aoHGE) is a tick-borne, obligate intracellular, granulocytotropic bacterium able to infect numerous host species. Given its unique niche and the leukopenia often noted with infection, we investigated the effect of acute aoHGE infection on neutrophil activation by evaluating surface expression of the beta 2 integrin CD11b/CD18 in a mouse model using FACS analysis. Infection resulted in neutrophil activation with up-regulation of CD11b/CD18 in multiple strains of mice, however, hematologic analysis showed no apparent role for CD11b/CD18 in mediating peripheral leukopenia. Because IFN-gamma is an important cytokine during granulocytic ehrlichiosis and is known to activate leukocytes, we investigated the potential role of IFN-gamma in CD11b/CD18 up-regulation. Neutrophils from IFN-gamma knock-out mice became activated during aoHGE infection, however, the kinetics of activation differed from wild-type mice. In addition, activation correlated directly with the presence of bacteria because neutrophils with large intracytoplasmic morula also expressed higher levels of CD11b/CD18. CD11b/CD18 seemed to be critical to early bacterial clearance and killing in vivo because infection of mice with targeted genetic disruption of CD11b/CD18 resulted in an initial increase in bacterial burden compared with wild-type mice. Similarly, in vitro culture of neutrophils from infected CD11b/CD18 knock-out mice resulted in a marked increase in bacterial proliferation compared with congenic controls. The data support crucial roles of CD11b/CD18 and IFN-gamma-mediated cell activation as mechanisms that limit bacterial replication.

Procalcitonin (PCT) has proven to be a very sensitive marker of sepsis for non-leucopenic patients. Little is known about its relevance in immunosuppressed and leucopenic adults. Four hundred and seventy-five PCT determinations were carried out in 73 haematological patients: on 221 occasions the white blood cell (WBC) count was < 1.0 x 10(9)/l and on 239 occasions it was > 1.0 x 10(9)/l leucocytes. Patients were classified as: non-systemic infected controls (n = 280), patients with bacteraemia (n = 32), sepsis (n = 30), severe sepsis (n = 3), septic shock (n = 3) and systemic inflammatory response syndrome (SIRS) (n = 62). When the WBC count was > 1.0 x 10(9)/l, gram-negative bacteria induced higher PCT levels (median 9.4 ng/ml) than gram-positives (median 1.4 ng/ml). In cases with a WBC < 1.0 x 10(9)/l, PCT levels were similar for gram-negative and gram-positive bacteria (1.1 ng/ml versus 0.85 ng/ml). Regardless of the leucocyte count, the median PCT level in bacteraemia cases always remained < 0.5 ng/ml. In heavily leucopenic situations, PCT levels were never > 2 ng/ml even in the sepsis and severe sepsis/septic shock groups, whereas a WBC count > 1.0 x 10(9)/l resulted in median PCT values of 4.1 ng/ml and 45 ng/ml respectively. The positive predictive value for sepsis (cut-off 2 ng/ml) was 93% in cases of WBC count > 1.0 x 10(9)/l, but only 66% in leucopenic conditions. The negative predictive value (cut-off 0.5 ng/ml) was 90% when the WBC count was > 1.0 x 10(9)/l and 63% in leucopenic conditions. Procalcitonin is an excellent sepsis marker with a high positive- and negative-predictive value in patients with WBC count > 1.0 x 10(9)/l, but it does not work satisfactorily below this leucocyte count.

It can be foreseen that in the years to come major improvements in neutropenic host infections will be achieved regarding the exact identification of risk factors, allowing better patient stratification; the application of molecular techniques to recognize pathogens; the development of effective new oral antimicrobials allowing home therapy or abbreviated hospitalization; the development of new antifungals; and the development of new effective immunomodulators and cytokines to ameliorate chemotherapy-induced neutropenia. In the years to come the threat of nosocomial infections unfortunately will not be eliminated, while the development of major new parenteral antibiotics cannot be foreseen. It is therefore the caregiver/physician himself who, by applying rational antibiotic policies and strict handwashing rules, will probably escape, for his neutropenic patient's sake, the imminent threat of multiresistant pathogens.

Long-circulating liposomes (LCL) may be used as targeted antimicrobial drug carriers as they localize at sites of infection. As a result, LCL-encapsulated gentamicin (LE-GEN) has demonstrated superior antibacterial activity over the free drug in a single-dose study of immunocompetent rats with Klebsiella pneumoniae pneumonia. In the present study, the therapeutic efficacy of LE-GEN was evaluated by monitoring rat survival and bacterial counts in blood and lung tissue in clinically relevant models, addressing the issue of impaired host defense and low bacterial antibiotic susceptibility. The results show that in immunocompetent rats infected with the high-GEN-susceptibility K. pneumoniae strain, a single dose of LE-GEN is clearly superior to an equivalent dose of free GEN. Yet complete survival can also be obtained with multiple doses of free GEN. In leukopenic rats infected with the high-GEN-susceptible K. pneumoniae strain, free GEN at the maximum tolerated dose (MTD) was needed to obtain survival. However, with the addition of a single dose of LE-GEN to free-GEN treatment, complete survival can be obtained using a sevenfold-lower cumulative amount of GEN than with free-GEN treatment alone. In leukopenic rats infected with low-GEN-susceptible K. pneumoniae cells, free GEN at the MTD did not result in survival. The use of LE-GEN is needed for therapeutic success. Increasing LE-GEN bilayer fluidity resulted in an increased GEN release from the liposomes and hence improved rat survival, thus showing the importance of the liposome lipid composition for therapeutic efficacy. These results warrant further clinical studies of liposomal formulations of aminoglycosides in immunocompromised patients with severe infections.

Typhoid fever, a systemic infectious disease caused by Salmonella typhi, is classically characterized by fever, paradoxical bradycardia, abdominal pain, and a rose colored rash. This was a retrospective review of 21 confirmed cases over a 5-year period. Mean age was 32.6 years (range 2-60 years), and Mexico (7/21) and El Salvador (3/21) represented the most common countries of origin. Recent travel to an endemic area was noted in 14 patients. The most common complaints were fever (15/21), headache (10/21), abdominal pain (9/21), and diarrhea (6/21). Average duration of symptoms before presentation to the Emergency Department (ED) was 7.9 days. High fever associated with bradycardia was noted in 12 patients. Leukopenia was present in 7 patients. Blood culture was the most sensitive confirmatory test while the Widal test was positive in 7 out of 11 cases. Fever of unknown origin (12/21), followed by presumed typhoid fever (3/21) were the most common ED diagnoses. It is important to recognize that patients with typhoid fever may present to EDs in the US and this disease should be included in the differential diagnosis of febrile patients from Latin America or those with a history of recent travel to endemic countries.

Retrospectively we evaluated the records of 68 children with brucellosis. We found 58.2% had consumed unpasteurized milk and dairy products. Nonspecific manifestations included: arthralgia (78%), fever (75%) and sweating (60%). Localized manifestations included limping (75%) and arthritis (54%). Leukopenia was found in 51% of children and anaemia in 24%. Brucella species was cultured for blood of 16 (23.5%) patients. Combination therapy containing streptomycin was more effective than gentamicin combinations.

Pseudomonas aeruginosa orbital infections have been described very rarely in patients with neutropenia after chemotherapy. We report the case of a woman with the unusual association of Sjögren's disease and myelodysplasia, who suffered from a Pseudomonas aeruginosa orbital phlegmon after chemotherapy for her myelodysplastic syndrome. Partial intestinal antibiotic decontamination with ciprofloxacine did not prevent the infection. She was treated successfully with intravenous ceftazidime, netilmicin and granulocyte-colony stimulating factor (G-CSF). The normalization of the granulocyte count seems to play a crucial role for recovery. We present the clinical and radiological findings, discuss the therapy and review the literature concerning ocular infections due to Pseudomonas. Other infections due to this germ in immunocompromised hosts are briefly reviewed.

Forty five positive blood culture acute typhoid cases were studied during a 2 years period (1997-1999) in Abbassia Fever hospital, Cairo, Egypt. Their ages ranged between 4-23 (12 +/- 2.5) years. Male: Female ratio was 1:1. Three of the 4 classical signs namely: toxic look (84%), bronchitic chest (47%), tumid tympanitic abdomen (84%) and just palpable receding spleen (69%) were found in almost all cases and offer a good bed side clinical diagnostic test. Blood picture revealed anaemia, within normal white blood count and thrombocytopenia. Liver function tests showed within normal total serum bilirubin, two or more folds increase of ALT and within normal serum alkaline phosphatase. Comparing the 3 tests, namely significant Widal titre (56%), modified Widal test (89%) and bright spleen (78%), it was found that modified Widal test is the most sensitive serological test. Ultrasonographic finding of bright spleen is an easy, safe, noninvasive and sensitive technique which is relatively cheap. Each of the 3 drugs in our study namely chloramphenicol, quinolones and ceftriaxone resulted in improvement of general condition, drop of fever, increase in haemoglobin, white blood count and platelet count. Also, there was a significant improvement of liver function tests by either of the 3 drugs. Ceftriaxone is the best drug from the clinical and laboratory points of view followed by quinolones in multidrug resistant (MDR) acute typhoid cases. Chloramphenicol is still the drug of choice in chloramphenicol sensitive salmonellae.

The increasing emergence of penicillin-resistant and multidrug-resistant strains of Streptococcus pneumoniae will create a serious therapeutic problem in coming years. Trovafloxacin is a novel naphthyridone quinolone with promising activity against S. pneumoniae, including penicillin-resistant strains (MIC for 90% of the isolates tested, 0.25 microg/ml). We compared its in vivo efficacy with that of other fluoroquinolones (ciprofloxacin, temafloxacin, and sparfloxacin) and a reference beta-lactam (amoxicillin) in a model of acute experimental pneumonia. Immunocompetent Swiss mice were infected by peroral tracheal delivery of a virulent, penicillin-susceptible strain (MIC, 0.03 microg/ml); leukopenic Swiss mice were infected with three poorly virulent, penicillin-resistant strains (MICs, 4 to 8 microg/ml) and a ciprofloxacin-resistant strain (MIC, 32 microg/ml). Treatments were started 6 h (immunocompetent mice) or 3 h (leukopenic mice) after infection. Doses ranging from 12.5 to 300 mg/kg were given at 12- or 8-h intervals for 3 days. Trovafloxacin (25 mg/kg) was the most effective agent in vivo against penicillin-susceptible and -resistant strains. Corresponding survival rates were 2- to 4-fold higher than with 50-mg/kg sparfloxacin or temafloxacin and 8- to 16-fold higher than with 100-mg/kg ciprofloxacin. The ratios of the area under the concentration-time curve to the MIC in serum and lung tissue were more favorable with trovafloxacin than with the other quinolones. Efficacy in vivo correlated with pharmacokinetic parameters. Trovafloxacin shows potential for the treatment of infections due to penicillin-susceptible and -resistant S. pneumoniae but appears to be ineffective against a ciprofloxacin-resistant strain.

Twenty eight positive blood culture paratyphoid A fever cases were studied. Forty two positive blood culture typhoid cases were taken as controls. Cases and controls were subjected to: 1) careful history, 2) thorough clinical examination, 3) two blood cultures for salmonella, 4) Widal agglutination test, 5) total and differential white blood count, 6) urine and stool cultures following therapy. There was no significant difference in the clinical picture between acute paratyphoid A fever and acute typhoid fever except the significant decrease of anorexia (57%), toxic look (54%), coated tongue (64%) in acute paratyphoid A cases when compared to acute typhoid cases. The prevalence of extraintestinal symptoms in paratyphoid A cases may mimic viral infections. Three of the 4 classical signs namely; toxic look (54%), bronchitic chest (50%), splenomegaly (72%) and tympanitis (64%) were good bed side suggestive clinical diagnostic aids in paratyphoid A cases. Blood culture was the cornerstone of diagnosis of paratyphoid A cases. In 6 (21%), only the second blood sample was positive stressing the value of multiple cultures. Significant Widal antibody titre was elicited in only about half (57%) of paratyphoid A cases which was significantly lower than typhoid cases (83%). Leucopenia was found in only 25% of paratyphoid A cases. Eosinopenia was constant and is considered as a diagnostic and prognostic aid. No correlation was elicited between either the height of antibody titre or the height of leucocytic count and the severity of illness. There was no significant difference in the response to therapy or the occurrence of complications between paratyphoid A cases and typhoid cases. Up to the current knowledge, this is the first report on comparative study between acute paratyphoid A fever and acute typhoid fever in Egypt from clinical, diagnostic, therapeutic and prognostic points of view.

The cardiopulmonary response elicited by intravenous bacteria or endotoxin is well characterized in swine and has two major components. The first represents the acute pulmonary and broncho-constrictive phase (0-2 h) and the second phase (3-8 h) represents increased microvascular permeability, hypotension, and enhanced leukocyte-endothelial adhesion. The pulmonary vasoconstriction and bronchoconstriction of phase 1 results in acute pulmonary hypertension and airway dysfunction, which may result in rapid mortality. Because this acute pulmonary response may not mimic the development of human septic shock, we sought to block this early phase and examine the role of tumor necrosis factor in the latter septic phase (3-8 h). Employing a thromboxane A2 (TXA2) receptor antagonist (BAY U 3405) in the presence of LD100 Escherichia coli challenge, we blocked the acute pulmonary hypertensive phase and prevented early mortality, however, TXA2 blockade did not affect the latter development of septic shock and death. This latter lethal phase, characterized by prolonged leukopenia, was blocked in a dose-dependent manner by tumor necrosis factor monoclonal antibody. We conclude that the TXA2-blocked E. coli-challenged swine may provide a novel animal model in which to investigate the pathophysiology of acute septic shock.

The postantibiotic effect (PAE) is the persistent inhibition of bacterial growth after a brief exposure to an antibiotic. Most beta-lactams do not induce a PAE for Gram-negative bacteria, but PAEs have been reported for carbapenems and penems. This study investigated the effect of sequential doses of imipenem on the PAE for Pseudomonas aeruginosa and Escherichia coli cultures in a chemostat. The PAE for the bacterial population did not change even after six successive exposures to imipenem. Nevertheless, screening of colonies isolated after repeated drug exposure identified a single P. aeruginosa mutant whose imipenem PAE was shortened, although the MIC was unchanged. The PAEs for the parent and mutant were studied in vitro in batch culture by monitoring: (i) viable counts; (ii) electrical impedance of the culture medium; (iii) incorporation of radiolabelled N-acetyl-D-glucosamine and (iv) cell volume changes. PAEs for the parent and mutant were found to be significantly different by all in-vitro methods used. Moreover, the median cell volume in antibiotic-exposed cultures remained much smaller and less heterogeneous than in the control cultures, even though both cultures were growing at the same rate. The mutant was found to have a reduced expression of a 52 kDa outer membrane protein. These observations suggest that factors in addition to suppression of bacterial growth should be considered when studying the PAE. The PAEs of imipenem for the parent and mutant were studied in a thigh infection model in leucopenic mice. Similar PAEs were observed in vivo for both parent and mutant in one experiment and no PAEs for either organism were found in a second experiment. This study showed that although the PAE is a stable in-vitro phenomenon, the lack of correlation between the in-vitro and in-vivo results warrants caution in attributing clinical significance to the PAE of imipenem.

Acute, sublethal infection of mice with murine cytomegalovirus (MCMV) resulted in up to 80% decreases in the number of cells recoverable from the bone marrow, and a decrease in peripheral blood leucocyte counts during the first week of infection. Depopulation of the leucopoietic areas of the marrow was evident from examination of histological sections. The severity of bone marrow atrophy in MCMV-infected mice of different strains correlated with previously described genetically determined sensitivity to MCMV disease. Although the phenomenon only occurred when mice were inoculated with infectious virus preparations, fewer than one in 10(5) marrow cells were productively infected, suggesting that atrophy was not due to lytic infection of large numbers of bone marrow cells. Interestingly, increases in serum colony-stimulating activity were observed and these were proportional to the severity of bone marrow atrophy. After MCMV infection, we observed increases in the proportions of cells expressing some B-cell and myeloid cell markers and a decrease in the proportion of cells expressing an erythroid cell marker. There was no change in the frequency of marrow cells expressing mature T-cell markers. The numbers of myeloid lineage-committed progenitor cells (GM-CFU) in the marrow decreased 10- to 20-fold in BALB/c nu/+ mice, while there was a threefold decrease in their numbers in BALB/c nu/nu mice. In addition, increases in serum colony-stimulating activity were greater in BALB/c nu/+ mice than in BALB/c nu/nu mice. Our results suggest that growth factors produced after MCMV infection may accelerate the maturation and migration of cells from the marrow to sites of virus replication and inflammation, thus accounting for the depletion in numbers of marrow cells observed soon after MCMV infection.

Experimental subcutaneous Candida albicans infections in mice were used to examine the manner in which this pathogen is cleared in animals recovering from cyclophosphamide-induced leucopenia. In this system, infections at the inoculation sites progressed rapidly during a 6 day period of leucopenia to form arrays of parallel filamentous organisms that effectively isolated those in the interior from contact by neutrophils, even when the leucopenia had resolved. Dense collections of organisms also developed at sites of metastatic infection in the kidneys. A majority of the organisms were found to be viable when they were retrieved from the infected subcutaneous sites of animals that had recovered from leucopenia and whose abscesses had begun to drain spontaneously. Removal of the protective arrays of fungal cells appeared to be accomplished by drainage of abscess contents through the surface of the skin or into the collecting system of the kidney. Drainage of the subcutaneous abscesses did not occur in the cyclophosphamide-treated animals until after the neutrophilic infiltrates had developed, suggesting that this drainage process was mediated by neutrophils rather than by the organisms themselves. In summary, the above findings demonstrate that C. albicans infections in leucopenic hosts may progress to the extent that they would be very difficult to clear solely through the microbicidal processes of returning neutrophils. However, neutrophils also appear to promote the removal of masses of viable fungal cells to the exterior of the body.

To examine effects of pseudorabies virus (PrV) on immune cells, we investigated the ability of PrV to infect and replicate in porcine peripheral blood leukocytes (PBLs). Flow cytometric analysis revealed a leukopenia after challenge, with loss of 40% of circulating monocytes and 50% of circulating lymphocytes. Virus was isolated from PBLs of challenged pigs by cocultivation with porcine kidney cells, indicating that PBLs were infected in vivo. Presence of virus in PBLs coincided with the appearance of neurological signs 1 to 2 days prior to death. Lymphocytes stimulated with mitogens and infected in vitro sustained a low-level infection (10(5) median tissue culture infective dose per 2 x 10(6) cells). In vivo challenge perturbed the CD4/CD8 ratio of circulating lymphocytes. Survival was associated with low CD4/CD8 ratios and high levels of CD8+ cells. Mortality was associated with low levels of CD8+ cells and CD4/CD8 ratios greater than one. A maturational deficiency of CD8+ cells was found in young pigs. Our results support a mechanism of PrV immunosuppression through direct infection of circulating lymphocytes, with CD8+ T lymphocytes being important for survival.

The efficacy of SCH 39304 (SCH) against Aspergillus fumigatus was assessed with an immunosuppressed, temporarily leukopenic rabbit model of invasive aspergillosis. Therapy with SCH at 10 or 15 mg/kg of body weight per day was begun 24 h after lethal challenge and compared with therapy with amphotericin B at 1.5 mg/kg/day. Compared with untreated controls, SCH reduced mortality and also reduced the tissue burden of A. fumigatus 100- to 1,000-fold in liver, kidney, and lung tissues. SCH at 15 mg/kg/day and amphotericin B eliminated A. fumigatus in liver, kidney, and lung tissues. In addition, both dosages of SCH significantly eliminated the organism from brain tissues, compared with controls. Both SCH and amphotericin B decreased or eliminated circulating aspergillus antigen. These results show that new azoles can be as effective as amphotericin B in eradicating the organism from tissues and offer promise in improving the treatment of invasive aspergillosis.

The antibacterial activities of ciprofloxacin and ceftazidime against Klebsiella pneumoniae in vitro and in vivo were compared. Although there was only a minor difference between the MBCs of both drugs, the bacterial killing rate of ciprofloxacin in vitro was very fast in comparison with that of ceftazidime. Similarly, the intravenous administration of ciprofloxacin at 1 h after bacterial inoculation resulted in effective bacterial killing in the lungs of leukopenic rats. This killing was dose dependent, in contrast to the dose-independent bactericidal effect of ceftazidime. The high antibacterial activity of ciprofloxacin in the lungs as compared with that of ceftazidime was also reflected in its therapeutic efficacy in K. pneumoniae pneumonia and septicemia in leukopenic rats when these infections were treated at 6-h intervals over 4 days, starting at 5 h after bacterial inoculation. Concentrations of ciprofloxacin and ceftazidime in lung tissue were not significantly different. Regarding the antibacterial activity of both drugs against K. pneumoniae in relation to the bacterial growth rate in vitro and in the lungs of leukopenic rats, ciprofloxacin killed K. pneumoniae organisms that were not actively growing, whereas ceftazidime did not. In addition, it was demonstrated that when the intravenous administration of antibiotic was delayed from 1 h up to 24 h after bacterial inoculation, ceftazidime lost its antibacterial activity in the lungs and blood of leukopenic rats, whereas ciprofloxacin was still very effective. These data suggest that the capacity of an antibiotic to kill bacteria at a slow growth rate may be relevant for its therapeutic effect in established infections, in which slowly growing bacteria form a substantial part of the total bacterial population.

The efficacy of single agent and combination antibiotic therapy was evaluated in rats with severe granulocytopenia and Pseudomonas aeruginosa infection using animal survival, rates of bacteremia and the emergence of resistant organisms as criteria. In this model end points following single agent therapy with imipenem/cilastatin and the synergistic combination of moxalactam plus amikacin were comparable. At a high bacterial challenge dose, equivalent results were obtained using single agent therapy with either piperacillin or ticarcillin. Results were also similar following therapy with piperacillin or ticarcillin in synergistic combination with amikacin. At a lower bacterial challenge dose, aminoglycoside therapy was superior to therapy with the beta-lactams. Therapy with the in vitro synergistic double beta-lactam combination of ceftazidime plus piperacillin was no more effective than therapy with the individual compounds. Results from these studies in this discriminative animal model have in part been used to formulate prospective clinical antibiotic studies in granulocytopenic cancer patients.

Mice rendered leukopenic with cyclophosphamide and then challenged with viable Pseudomonas aeruginosa were used to determine the protective efficacy of active immunization against exotoxin A and of passive immunization with human antiserum to Escherichia coli J5, a rough mutant of Escherichia coli O111:B4. Neither treatment alone provided a greater degree of protection than its respective control. However, the combination of these treatments produced a moderate, yet consistent, increase in the survival of infected immunosuppressed mice.

Fifty-six of 67 patients with antibody to cytomegalovirus before transplantation shed cytomegalovirus from urine and/or saliva postoperatively. Symptomatic reactivation occurred in 17 (25%) patients, five of whom had pneumonitis. The symptomatic patients were more likely to have received a cadaver kidney (P = 0.004) and high-dosage antithymocyte globulin (P = 0.003) and to be viremic (P < 0.0001), compared to patients with silent infection. Forty-eight of 49 patients treated with antithymocyte globulin received cadaver or parent donor kidneys. Twenty-four were given a low-dosage intramuscular regimen, and 25 received a higher dosage intravenously. In the latter group 48% experienced symptomatic reactivation adn 48% viremia, compared to 21% and 17%, respectively, in the former group (P < 0.05 for both comparisons). There were no symptomatic cytomegaloviral infections among 18 patients not treated with antithymocyte globulin, all of whom received related donor kidneys. Renal transplant patients who receive both a poorly matched graft and antithymocyte globulin are at increased risk of morbidity due to cytomegalovirus.

The in vitro and in vivo activity of carumonam was tested in comparison with that of aztreonam and other beta-lactam antibiotics. With the exception of a few isolates that were overproducers of cephalosporinase, Enterobacteriaceae were highly susceptible to carumonam, 90% of the isolates being inhibited at 0.5 micrograms/ml. Aztreonam, ceftriaxone and ceftazidime were overall slightly less active than carumonam against Enterobacteriaceae. Carumonam was intermediate between ceftazidime and aztreonam as to the activity against Pseudomonas aeruginosa. Staphylococci were resistant to the monocyclic beta-lactams. In accordance with the in vitro data, carumonam was effective against experimental septicemias and infections of the thigh and the kidney that were caused by gram-negative pathogens.

We report two cases of a T cell lymphoproliferative disease not previously described, with cytologic and clinical features similar to those associated with Galton's "prolymphocytic" leukemia (PL). Our patients, like those with Galton's PL, had massive splenomegaly and minimal or absent hepatomegaly and lymphadenopathy. In contrast, however, our patients had leukopenia, as well as low percentages of leukemic cells in the peripheral blood and in the bone marrow. In splenic imprints, the nuclear chromatin pattern of most of the leukemic cells was intermediate between those of mature lymphocytes and those of lymphoblasts, and the nuclei contained single, centrally located, conspicuous nucleoli. In sections of the spleen, the leukemic cells diffusely infiltrated the red pulp in a pattern strikingly similar to that of hairy cell leukemia; however, when the leukemic cells were studied cytochemically, the cytoplasmic acid phosphatase positivity was punctate and tartrate-sensitive. The leukemic cells were sheep erythrocyte rosette-positive and expressed T cell-associated antigens. Initially, both patients responded well to therapeutic splenectomy. One patient received combination chemotherapy after splenectomy and is alive and well 24 months after diagnosis. The other patient was in complete clinical remission for one year after splenectomy and received chemotherapy at relapse. He died, however, 23 months after splenectomy, with disseminated disease. IgG antibody titers against human T lymphotropic virus type I (HTLV-I) were detected in one patient and against HTLV-II in the other. The leukemia in these patients represents a distinct clinicopathologic entity within the spectrum of peripheral T cell lymphoproliferative diseases that includes Galton's PL of T cell derivation, T cell chronic lymphocytic leukemia, T cell hairy cell leukemia, and adult T cell leukemia/lymphoma.

The course of experimental cutaneous Candida albicans infections produced in mice made leucopenic by the administration of cyclophosphamide was compared to that in untreated animals. In the latter, neutrophils characteristically infiltrated the area of infection and the organisms were virtually always confined to the epidermis. However, even though many fewer foci of infection were associated with neutrophils in the cyclophosphamide-treated animals, a majority of these foci were also unable to penetrate past the epidermis. Although Candida yeast proliferated relatively poorly when cultured in homogenates of skin lacking the epidermis, Candida pseudohyphae could invade into the dermis if inoculated skin was isolated from normal animals and cultured in vitro, or if the epidermis was removed by gentle scraping prior to inoculation with Candida yeast onto the remaining skin of leucopenic animals. Therefore, in the absence of neutrophil contact and killing of Candida pseudohyphae in the epidermis, other cutaneous defense mechanisms appear to be capable of preventing invasion of a majority of the organisms into the dermis. These findings may help to explain why deep Candida infections are rare in patients who have extensive superficial candidiasis.

The influence of leukocytes and Haemophilus influenzae type b (Hib) capsule on blood brain barrier permeability (BBBP) to circulating 125I-albumin in normal and leukopenic rats was assessed after intracisternal inoculation of encapsulated (Rd-/b+/02) or unencapsulated (Rd-/b-/02) isogenic strains of Hib. Both normal and leukopenic animals had increased BBBP 18 h after inoculation, with normal rats demonstrating significantly increased BBBP after challenge with the encapsulated strain. Despite cerebrospinal fluid (CSF) pleocytosis in normal rats, CSF bacterial concentrations were not lower. Normal rats cleared unencapsulated Rd-/b-/02 more effectively than leukopenic rats, with BBBP correlating with CSF bacterial density and not leukocyte concentrations. Challenge with heat-killed Rd-/b+/02 resulted in increased BBBP in both normal and leukopenic rats, with greater BBBP at higher bacterial concentrations. The data suggest: (a) significant increases in BBBP occur in the near absence of CSF leukocytes; (b) CSF leukocytes can augment changes in BBBP; (c) type b capsule inhibits host clearance mechanisms within the CSF; and (d) BBBP appears to correlate with bacterial concentrations within the CSF.