Invasive Non-typhoidal Salmonella (iNTS) Infections.

Salmonella enterica invade the host via the intestinal tract. There are ~2 thousand distinct serovars of non-typhoidal Salmonella (NTS) that can cause gastroenteritis in normal hosts, but bacteremia is an uncommon complication of gastroenteritis except at the extremes of age (in Graham et al. Nontyphoidal Salmonella infections of children in tropical Africa. Pediatr Infect Dis J 2000; 19:1189-96). In contrast, enteric fever and invasive NTS infections (iNTS) are each caused by only a few serovars of S. enterica (Table 1), and bacteremia not gastroenteritis is their principal manifestation.

Controversies in the Management of Central Nervous System Coccidioidomycosis.

Central nervous system infection with Coccidioides spp. is fatal if untreated and complications occur even when therapy is directed by experienced clinicians. We convened a panel of clinicians experienced in the management of coccidioidal meningitis to summarize current controversies and provide consensus for the management of this difficult infection.

Antimicrobial-Resistant Shigella spp. in San Diego, California, USA, 2017-2020.

Annually, Shigella spp. cause ≈188 million cases of diarrheal disease globally, including 500,000 cases in the United States; rates of antimicrobial resistance are increasing. To determine antimicrobial resistance and risk factors in San Diego, California, USA, we retrospectively reviewed cases of diarrheal disease caused by Shigella flexneri and S. sonnei diagnosed during 2017-2020. Of 128 evaluable cases, S. flexneri was slightly more common than S. sonnei; most cases were in persons who were gay or bisexual cisgender men, were living with HIV, were unhoused, or used methamphetamines. Overall, rates of resistance to azithromycin, fluoroquinolones, ampicillin, and trimethoprim/sulfamethoxazole (TMP/SMX) were comparable to the most recent national data reported from the Centers for Disease Control and Prevention; 55% of isolates were resistant to azithromycin, 23% to fluoroquinolones, 70% to ampicillin, and 83% to TMP/SMX. The rates that we found for TMP/SMX were slightly higher than those in national data.

Interleukin-8 Receptor 2 (IL-8R2)-Deficient Mice Are More Resistant to Pulmonary Coccidioidomycosis than Control Mice.

The pathology of human coccidioidomycosis is granulomatous inflammation with many neutrophils surrounding ruptured spherules, but the chemotactic pathways that draw neutrophils into the infected tissues are not known. We previously showed that formalin-killed spherules (FKS) stimulate mouse macrophages to secret macrophage inflammatory protein 2 (MIP-2), which suggested that CXC ELR+ chemokines might be involved in neutrophil recruitment in vivo To test that hypothesis, we intranasally infected interleukin-8R2 (IL-8R2) (Cxcr2)-deficient mice on a BALB/c background with Coccidioides immitis RS. IL-8R2-deficient mice had fewer neutrophils in infected lungs than controls, but unexpectedly the IL-8R2-deficient mice had fewer organisms in their lungs than the control mice. Infected IL-8R2-deficient mouse lungs had higher expression of genes associated with lymphocyte activation, including the Th1 and Th17-related cytokines Ifnγ and Il17a and the transcription factors Stat1 and Rorc Additionally, bronchial alveolar lavage fluid from infected IL-8R2-deficient mice contained more IL-17A and interferon-γ (IFN-γ). We postulate that neutrophils in the lung directly or indirectly interfere with the development of a protective Th1/Th17 immune response to C. immitis at the site of infection.

APX001 and Other Gwt1 Inhibitor Prodrugs Are Effective in Experimental Coccidioides immitis Pneumonia.

Coccidioidomycosis is a systemic fungal infection caused by the inhalation of the arthroconidia of either of two closely related dimorphic fungi, Coccidioides immitis and C. posadasii, that are endemic in the southwestern United States and other areas in the Western Hemisphere. Chronic cavitary pulmonary infections and extrapulmonary sites of infection are very difficult to treat and often require lifelong azole therapy. APX001A is the first in a new class of broad-spectrum antifungal agents that inhibit Gwt1, an enzyme which is required for cell wall localization of glycosylphosphatidylinositol (GPI)-anchored mannoproteins in fungi. APX001A and several analogs were highly active against clinical isolates of Coccidioides, inhibiting hyphal growth at low nanogram/ml concentrations. APX001 is the N-phosphonooxymethyl prodrug of APX001A, currently in clinical trials for the treatment of invasive fungal infections. Mice were treated orally once daily with 26 mg/kg/day of APX001 and the prodrug analog APX2097, 2 h after administration of the pan-cytochrome P450 inhibitor 1-aminobenzotriazole, which was used to enhance drug half-life and exposures to more closely mimic human pharmacokinetics of APX001A. Five days of treatment reduced lung colony counts by nearly 3 logs and prevented dissemination, similar to the efficacy of fluconazole dosed orally at 25 mg/kg twice daily. In a survival experiment, both APX001- and APX2097-treated mice survived significantly longer than control and fluconazole-treated mice. APX001 and other members of this new class of antifungal agents may offer great promise as effective therapies for coccidioidomycosis.

A review of innate and adaptive immunity to coccidioidomycosis.

Coccidioidomycosis is a human fungal disease cause by inhalation of aerosol spores produced by Coccidioides posadasii or Coccidioides immitis. This disease is a common cause of community-acquired pneumonia in the endemic areas of the Southwestern United States. It also can present as a life-threatening disease as the fungal cells disseminate to skin, bone, and central nervous system. The outcome of coccidioidomycosis is largely determined by the nature of host immune response to the infection. Escalation of symptomatic infections and increased cost of long-term antifungal treatment warrant a concerted effort to better understand the innate and adaptive immune responses and the genetics associated with coccidioidomycosis susceptibility. This knowledge can be harnessed for development of a human vaccine against Coccidioides and advance clinic management of this disease. This review discusses recently reported studies on innate and adaptive immunity to Coccidioides infection, Mendelian susceptibility to disseminated disease and progress toward a human vaccine against this formidable disease.

Myeloid Differentiation Factor 88 and Interleukin-1R1 Signaling Contribute to Resistance to Coccidioides immitis.

Rodents are a natural host for the dimorphic pathogenic fungi Coccidioides immitis and Coccidioides posadasii, and mice are a good model for human infection. Humans and rodents both express Dectin-1 and Toll-like receptor 2 (TLR2) on myeloid cells, and those receptors collaborate to maximize the cytokine/chemokine responses to spherules (the tissue form of the fungi) and to formalin-killed spherules (FKS). We showed that Dectin-1 is necessary for resistance to pulmonary coccidioidomycosis, but the importance of TLR2 in vivo is uncertain. Myeloid differentiation factor 88 (MyD88) is the adapter protein for TLR2 and -4, interleukin-1R1 (IL-1R1), and IL-18R1. MyD88/TRIF-/- and MyD88-/- mice were equally susceptible to C. immitis infection, in contrast to C57BL/6 (B6) controls. Of the four surface receptors, only IL-1R1 was required for resistance to C. immitis, partially explaining the susceptibility of MyD88-/- mice. We also found that FKS stimulated production of IL-1Ra by bone marrow-derived dendritic cells (BMDCs), independent of MyD88 and Dectin-1. There also was a very high concentration of IL-1Ra in the lungs of infected B6 mice, supporting the potential importance of this regulatory IL-1 family protein in the largely ineffective response of B6 mice to coccidioidomycosis. These results suggest that IL-1R1 signaling is important for defense against C. immitis infection.

Salmonella-induced Diarrhea Occurs in the Absence of IL-8 Receptor (CXCR2)-Dependent Neutrophilic Inflammation.

BACKGROUND: Gastroenteritis is the most common manifestation of nontyphoidal Salmonella enterica infections, but little is known about the pathogenesis of diarrhea in this infection METHODS: To determine whether polymorphonuclear neutrophils (PMNs) are required for diarrhea for Salmonella colitis, we infected kanamycin-pretreated interleukin 8R (IL-8R) mutant mice and controls, both with nonmutant Slc11a1 (Nramp1, ItyR). We compared the 2 mouse strains for increases in fecal water content (diarrhea) 3 days after infection, changes in expression of ion transporters in colonic epithelial cells, proliferation of epithelial cells, and severity of infection as measured by colony-forming units (CFUs). RESULTS: The IL-8R knockout mice had fewer PMNs in the colon but the other variables we measured were unaffected except for an increase in CFUs in the colon. The pathologic changes in the cecum were similar in both groups except for the lack of PMNs in the IL-8R knockout mice. There was minimal damage to the colon more distally. CONCLUSIONS: In the early stage of Salmonella colitis, PMNs are not required for diarrhea or for the decrease in expression of colonic epithelial cell apical ion transporters. They contribute to defense against infection in the cecum but not extracolonically at this stage of Salmonella colitis.

Clinical and microbiological determinants of infection after transrectal prostate biopsy.

BACKGROUND: Increasing numbers of infections following transrectal prostate biopsy (TPB) at our hospital led us to investigate clinical and bacterial risk factors to determine if the colonizing rectal Escherichia coli population is the source. METHODS: We performed an observational cohort study of men undergoing TPB (1 January 2010-6 February 2014) at the San Diego Veterans Affairs Medical Center. The primary outcome was clinically significant post-TPB infection. Rectal swabs were collected immediately before the biopsy and cultured selectively for fluoroquinolone-resistant gram-negative bacilli. Fluoroquinolone-resistant clinical and rectal E. coli isolates were compared using phylotyping, pulsed-field gel electrophoresis (PFGE) analysis, sequence typing, and virulence gene profiling. RESULTS: Rectal colonization with fluoroquinolone-resistant organisms (98% E. coli) was detected in 121 of 764 subjects (15.8%). Post-TPB infection was more common among fluoroquinolone-resistant-colonized subjects than noncolonized subjects (13/121 [10.7%] vs 8/649 [1.2%]; P < .001). Presence of fluoroquinolone-resistant colonizing E. coli was the most significant host characteristic associated with post-TPB infection (odds ratio, 4.5 [95% confidence interval, 1.2-18.2]; P = .03). Escherichia coli infection isolates (n = 18) did not differ from E. coli rectal culture isolates (n = 68) for any of 49 virulence genes or ST131 status (all P > .05). The rectal and clinical isolates of all 9 men with paired isolates had indistinguishable PFGE patterns and identical antimicrobial susceptibility profiles. CONCLUSIONS: The rectal colonizing E. coli population is the source for most fluoroquinolone-resistant post-TPB infections, regardless of clonal background or virulence traits. Screening cultures can identify nearly all patients at risk for fluoroquinolone-resistant post-TPB infection.

Neither dectin-2 nor the mannose receptor is required for resistance to Coccidioides immitis in mice.

We investigated the roles of the mannose receptor (MR) and Dectin-2 in resistance to pulmonary coccidioidomycosis in C57BL/6 (B6) mice and in the interaction of myeloid cells with spherules, using B6 mice with targeted mutations in Mrc1 and Clec4n. Spherules are the tissue form of Coccidioides, and we determined that the MR on bone marrow-derived dendritic cells (BMDC) was important for recognition of spherules (formalin-killed spherules [FKS]) and for secretion of interleukin 10 (IL-10) and proinflammatory cytokines in response to FKS by both elicited macrophages and BMDC. Infected MR knockout (KO) mice produced more IL-10 in their lungs than did B6 mice, and MR KO mice also made more protective Th-17 cytokines. In contrast to the MR, Dectin-2 was not required for recognition of FKS by BMDC or for the production of cytokines by BMDC in response to FKS. However, Dectin-2 KO was required for stimulation of elicited peritoneal macrophages. Despite that, lung cytokine levels were not significantly different in Dectin-2 KO mice and B6 mice 14 days after infection, except for IL-1ß, which was higher in Dectin-2 KO lungs. Although both Dectin-2(-/-) and MR(-/-) myeloid cells had reduced proinflammatory cytokine responses to FKS in vitro, neither MR nor Dectin-2 deficiency reduced the resistance of B6 mice to pulmonary coccidioidomycosis.

Altered expression and localization of ion transporters contribute to diarrhea in mice with Salmonella-induced enteritis.

BACKGROUND & AIMS: Salmonella enterica serovar Typhimurium is an enteropathogen that causes self-limiting diarrhea in healthy individuals, but poses a significant health threat to vulnerable populations. Our understanding of the pathogenesis of Salmonella-induced diarrhea has been hampered by the lack of a suitable mouse model. After a dose of oral kanamycin, Salmonella-infected congenic BALB/c.D2(NrampG169) mice, which carry a wild-type Nramp1 gene, develop clear manifestations of diarrhea. We used this model to elucidate the pathophysiology of Salmonella-induced diarrhea. METHODS: BALB /c.D2(NrampG169) mice were treated with kanamycin and then infected with wild-type or mutant Salmonella by oral gavage. Colon tissues were isolated and Ussing chambers, quantitative polymerase chain reaction, immunoblot, and confocal microscopy analyses were used to study function and expression of ion transporters and cell proliferation. RESULTS: Studies with Ussing chambers demonstrated reduced basal and/or adenosine 3',5'-cyclic monophosphate-mediated electrogenic ion transport in infected colonic tissues, attributable to changes in chloride or sodium transport, depending on the segment studied. The effects of infection were mediated, at least in part, by effector proteins secreted by the bacterial Salmonella pathogenicity island 1- and Salmonella pathogenicity island-2-encoded virulence systems. Infected tissue showed reduced expression of the chloride-bicarbonate exchanger down-regulated in adenoma in surface colonic epithelial cells. Cystic fibrosis transmembrane conductance regulator was internalized in colonic crypt epithelial cells without a change in overall expression levels. Confocal analyses, densitometry, and quantitative polymerase chain reaction revealed that expression of epithelial sodium channel ß was reduced in distal colons of Salmonella-infected mice. The changes in transporter expression, localization, and/or function were accompanied by crypt hyperplasia in Salmonella-infected mice. CONCLUSIONS: Salmonella infection induces diarrhea by altering expression and/or function of transporters that mediate water absorption in the colon, likely reflecting the fact that epithelial cells have less time to differentiate into surface cells when proliferation rates are increased by infection.

Fluoroquinolone resistant rectal colonization predicts risk of infectious complications after transrectal prostate biopsy.

PURPOSE: Infection after transrectal prostate biopsy has become an increasing concern due to fluoroquinolone resistant bacteria. We determined whether colonization identified by rectal culture can identify men at high risk for post-transrectal prostate biopsy infection. MATERIALS AND METHODS: Six institutions provided retrospective data through a standardized, web based data entry form on patients undergoing transrectal prostate biopsy who had rectal culture performed. The primary outcome was any post-transrectal prostate biopsy infection and the secondary outcome was hospital admission 30 days after transrectal prostate biopsy. We used chi-square and logistic regression statistical analysis. RESULTS: A total of 2,673 men underwent rectal culture before transrectal prostate biopsy from January 1, 2007 to September 12, 2013. The prevalence of fluoroquinolone resistance was 20.5% (549 of 2,673). Fluoroquinolone resistant positive rectal cultures were associated with post-biopsy infection (6.6% vs 1.6%, p <0.001) and hospitalization (4.4% vs 0.9%, p <0.001). Fluoroquinolone resistant positive rectal culture increased the risk of infection (OR 3.98, 95% CI 2.37-6.71, p <0.001) and subsequent hospital admission (OR 4.77, 95% CI 2.50-9.10, p <0.001). If men only received fluoroquinolone prophylaxis, the infection and hospitalization proportion increased to 8.2% (28 of 343) and 6.1% (21 of 343), with OR 4.77 (95% CI 2.50-9.10, p <0.001) and 5.67 (95% CI 3.00-10.90, p <0.001), respectively. The most common fluoroquinolone resistant bacteria isolates were Escherichia coli (83.7%). Limitations include the retrospective study design, nonstandardized culture and interpretation of resistance methods. CONCLUSIONS: Colonization of fluoroquinolone resistant organisms in the rectum identifies men at high risk for infection and subsequent hospitalization from prostate biopsy, especially in those with fluoroquinolone prophylaxis only.

Group B Streptococcus CovR regulation modulates host immune signalling pathways to promote vaginal colonization.

Streptococcus agalactiae (Group B Streptococcus, GBS) is a frequent commensal organism of the vaginal tract of healthy women. However, GBS can transition to a pathogen in susceptible hosts, but host and microbial factors that contribute to this conversion are not well understood. GBS CovR/S (CsrR/S) is a two component regulatory system that regulates key virulence elements including adherence and toxin production. We performed global transcription profiling of human vaginal epithelial cells exposed to WT, CovR deficient, and toxin deficient strains, and observed that insufficient regulation by CovR and subsequent increased toxin production results in a drastic increase in host inflammatory responses, particularly in cytokine signalling pathways promoted by IL-8 and CXCL2. Additionally, we observed that CovR regulation impacts epithelial cell attachment and intracellular invasion. In our mouse model of GBS vaginal colonization, we further demonstrated that CovR regulation promotes vaginal persistence, as infection with a CovR deficient strainresulted in a heightened host immune response as measured by cytokine production and neutrophil activation. Using CXCr2 KO mice, we determined that this immune alteration occurs, at least in part, via signalling through the CXCL2 receptor. Taken together, we conclude that CovR is an important regulator of GBS vaginal colonization and loss of this regulatory function may contribute to the inflammatory havoc seen during the course of infection.

tPA Alu (I/D) polymorphism associates with bacterial osteomyelitis.

BACKGROUND: Coagulation and fibrinolysis are important in infections and systemic inflammatory response syndrome. Polymorphisms in plasminogen activator inhibitor-1 (PAI-1, SERPINE1) and tissue plasminogen activator (tPA, PLAT), such as PAI-1 (-675 4G/5G deletion/insertion) and tPA (Alu insertion/deletion [I/D]), are associated with strokes, myocardial infarctions, bacterial infections and septic shock severity, and trauma. Osteomyelitis is a mostly posttraumatic, Staphylococcal bone infection. PATIENTS AND METHODS: tPA Alu (I/D) (rs4646972) and PAI-1 (4G/5G) (rs1799889) polymorphisms were studied by DNA amplification with polymerase chain reaction in 261 patients with osteomyelitis and in 299 matched blood donors. Plasma PAI-1/tPA complex was assessed by enzyme-linked immuosorbent assay. RESULTS: II homozygotes (37.9% vs 19.1%) and I allele carriers (56.3% vs 46.3%) for the tPA Alu (I/D) polymorphism were significantly more frequent in osteomyelitis patients compared to controls (P < .001). II genotype carrier osteomyelitis patients had lower PAI-1/tPA complex levels compared to those with the D allele (P ≤ .04). There was no association between these genotypes and chronicity of osteomyelitis, post-traumatic etiology, or with a specific bacterial etiology. PAI-1 (4G/4G) homozygotes were not significantly different between osteomyelitis patients and controls (P = .1). CONCLUSIONS: We report for the first time to our knowledge an association between the tPA Alu (I/D) polymorphism and susceptibility to bacterial osteomyelitis, perhaps by fibrinolysis dysfunction.

The Host Response to Coccidioidomycosis.

Coccidioidomycosis is an important fungal disease that is found in many desert regions of the western hemisphere. The inhaled organisms are highly pathogenic, but only half of infected, immunologically intact people develop symptomatic pneumonia; most symptomatic infections resolve spontaneously, although some resolve very slowly. Furthermore, second infections are very rare and natural immunity after infection is robust. Therefore, the host response to this organism is very effective at resolving the infection in most cases and immunizing to prevent second infections. People who are immunocompromised are much more likely to develop disseminated infection. This is a comprehensive review of the innate and acquired immune responses to Coccidioides spp., the genetics of resistance to severe infection, and the search for an effective vaccine.

Rapid progression to decompensated cirrhosis, liver transplant, and death in HIV-infected men after primary hepatitis C virus infection.

BACKGROUND: We and others have shown that primary hepatitis C (HCV) infection in men infected with human immunodeficiency virus (HIV) causes early-onset liver fibrosis; however, little is known about the long-term natural history of the liver disease in these HIV-infected men. METHODS: We followed a cohort of HIV-infected men with primary HCV infection in New York City. RESULTS: Four men who were not cured after their primary HCV infection developed decompensated cirrhosis within 17 months to 6 years after primary HCV infection. Three died within 8 years of primary HCV infection, and 1 survived after liver transplant done 2 years after primary HCV infection. Three of the 4 men had AIDS at the time of primary HCV infection, and the most rapid progression occurred in the 2 men with the lowest CD4 counts at the time of HCV infection. Liver histopathology was most consistent with HCV-induced damage even though some had exposures to other potential hepatotoxins. CONCLUSIONS: Primary HCV infection resulted in decompensated cirrhosis and death within 2-8 years in 4 HIV-infected men. The rapid onset of fibrosis due to primary HCV infection in HIV-infected men cannot therefore be considered benign. The rate of continued progression to liver failure may be proportional to the degree of underlying immunocompromise caused by HIV infection. More research is needed to better define the mechanisms behind accelerated liver damage.

Gene expression in human fungal pathogen Coccidioides immitis changes as arthroconidia differentiate into spherules and mature.

BACKGROUND: Coccidioides immitis is a dimorphic fungus that causes disease in mammals, including human beings. It grows as a mycelium containing arthroconidia in the soil and in the host arthroconidia differentiates into a unique structure called a spherule. We used a custom open reading frame oligonucleotide microarray to compare the transcriptome of C. immitis mycelia with early (day 2) and late stage (day 8) spherules grown in vitro. All hybridizations were done in quadruplicate and stringent criteria were used to identify significantly differentially expressed genes. RESULTS: 22% of C. immitis genes were differentially expressed in either day 2 or day 8 spherules compared to mycelia, and about 12% of genes were differentially expressed comparing the two spherule time points. Oxireductases, including an extracellular superoxide dismutase, were upregulated in spherules and they may be important for defense against oxidative stress. Many signal transduction molecules, including pleckstrin domain proteins, protein kinases and transcription factors were downregulated in day 2 spherules. Several genes involved in sulfur metabolism were downregulated in day 8 spherules compared to day 2 spherules. Transcription of amylase and α (1,3) glucan synthase was upregulated in spherules; these genes have been found to be important for differentiation to yeast in Histoplasma. There were two homologs of 4-hydroxyphenylpyruvate dioxygenase (4-HPPD); transcription of one was up- and the other downregulated. We tested the effect of a 4-HPPD inhibitor, nitisinone, on mycelial and spherule growth and found that it inhibited mycelial but not spherule growth. CONCLUSIONS: Transcription of many genes was differentially expressed in the process of arthroconidia to spherule conversion and spherule maturation, as would be expected given the magnitude of the morphologic change. The transcription profile of early stage (day 2) spherules was different than late stage (day 8) endosporulating spherules. In addition, very few genes that are important for spore to yeast conversion in other dimorphic fungi are differentially expressed in C. immitis mycelia and spherules suggesting that dimorphic fungi may have evolved different mechanisms to differentiate from mycelia to tissue invasive forms.

The use of ceftaroline fosamil in methicillin-resistant Staphylococcus aureus endocarditis and deep-seated MRSA infections: a retrospective case series of 10 patients.

There are many limitations to the current antibiotics used for the treatment of severe methicillin-resistant Staphylococcus aureus (MRSA) infections. Ceftaroline is a new fifth-generation cephalosporin approved for the treatment of skin and soft tissue infections caused by MRSA and community-acquired pneumonia. We propose that ceftaroline can also be used successfully in more severe MRSA infections, including endocarditis. We conducted a retrospective chart review in a university-affiliated Department of Veterans Affairs hospital in San Diego, California (USA) of ten inpatients treated with ceftaroline for severe MRSA infection, including five cases of probable endocarditis (including two endocardial pacemaker infections), one case of pyomyositis with possible endocarditis, two cases of pneumonia (including one case of empyema), two cases of septic arthritis (including one case of prosthetic joint infection), and two cases of osteomyelitis. Seven of the 10 patients achieved microbiological cure. Six of the 10 patients achieved clinical cure. Seven patients were discharged from the hospital. Three patients were placed on comfort care and expired in the hospital; one achieved microbiological cure before death, and two remained bacteremic at time of death. In most patients, ceftaroline was effective for treatment of MRSA bacteremia and other severe MRSA infections. Adverse effects seen included rash, eosinophilia, pruritus, and Clostridium difficile infection. Ceftaroline can be a safe and effective drug for treatment of severe MRSA infections, and further comparative studies are warranted.