Michael Bolaris

Diabetic murine models for Acinetobacter baumannii infection

OBJECTIVES Extremely drug-resistant (XDR; i.e. resistant to all antibiotics except colistin or tigecycline) Acinetobacter baumannii has emerged as one of the most common and highly antibiotic-resistant causes of infection. Diabetes is a risk factor for acquisition of and worse outcomes from A. baumannii infection. We sought to develop diabetic mouse models of A. baumannii bacteraemia and pneumonia and validate these models by comparing the efficacy of antibiotic treatment in these models with the established neutropenic mouse models. METHODS Diabetic or neutropenic mice were infected via intravenous inoculation or inhalation in an aerosol chamber with an XDR A. baumannii. Treatment with colistin started 24 h after infection and continued daily for 7 days. Survival served as the primary endpoint while tissue bacterial burden and histopathological examination served as secondary endpoints. RESULTS Lethal infection was achieved for the neutropenic and diabetic mice when infected intravenously or via inhalation. Neutropenic mice were more susceptible to infection than diabetic mice in the pneumonia model and equally susceptible in the bacteraemia model. Both models of bacteraemia were sensitive enough to detect virulence differences among different clinical strains of A. baumannii. In the pneumonia model, colistin treatment was effective in improving survival, reducing lung bacterial burden and histologically resolving the infection compared with placebo only in diabetic mice. CONCLUSIONS We developed novel models of A. baumannii bacteraemia and pneumonia in diabetic mice. These models can be used to study mechanisms of infection, develop immunotherapeutic strategies and evaluate drug efficacies against highly lethal A. baumannii infections.

Molecular epidemiology and characterization of multiple drug-resistant (MDR) clinical isolates of Acinetobacter baumannii

OBJECTIVES The aim of this study was to identify the genetic relatedness of multiple drug-resistant (MDR) Acinetobacter baumannii clinical isolates recovered from a hospital in Los Angeles. METHODS Twenty-one MDR A. baumannii isolates were collected and their antibiotic susceptibilities determined according to Clinical and Laboratory Standards Institute guidelines. Genes coding for antibiotic resistance were identified by PCR, and their identities were confirmed by DNA sequencing. Clonal relationships were studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). RESULTS MDR consistently correlated with the presence of oxacillinases, mostly in the form of the plasmid-mediated OXA-23 enzyme, which was detected in 12 (57.1%) isolates. GES-type carbapenemases were found in 20 (95.2%) strains, AAC in all 21 (100%) strains, and PER in seven (33.3%) strains, and ISAba1 was detected in 16 (76.2%) isolates. The association between ISAba1 and resistance genes confirms insertion elements as a source of β-lactamase production. Of the 21 clinical isolates, five were found to be related to sequence type 1 (ST1) and 16 to ST2, as analyzed by MLST. PFGE demonstrated that the majority of clinical isolates were highly related (>85%). CONCLUSIONS This study supports a more complete understanding of genotyping of antibiotic resistance for better assessment of MDR strain transmission.

Pharmacokinetics of Rilpivirine in HIV-Infected Pregnant Women.

Background:Rilpivirine pharmacokinetics is defined by its absorption, distribution, metabolism, and excretion. Pregnancy can affect these factors by changes in cardiac output, protein binding, volume of distribution, and cytochrome P450 (CYP) 3A4 activity. Rilpivirine is metabolized by CYP3A4. The impact of pregnancy on rilpivirine pharmacokinetics is largely unknown. Methods:International Maternal Pediatric Adolescent AIDS Clinical Trials P1026s is a multicenter, nonblinded, prospective study evaluating antiretroviral pharmacokinetics in HIV-infected pregnant women that included a cohort receiving rilpivirine 25 mg once daily as part of their combination antiretrovirals for clinical care. Thirty-two women were enrolled in this study. Intensive pharmacokinetic sampling was performed at steady state during the second trimester, the third trimester, and postpartum. Maternal and umbilical cord blood samples were obtained at delivery. Plasma rilpivirine concentration was measured using liquid chromatography–mass spectrometry; lower limit of quantitation was 10 ng/mL. Results:Median (range) AUC0–24 were 1969 (867–4987, n = 15), 1669 (556–4312, n = 28), and 2387 (188–6736, n = 28) ng·h/mL in the second trimester, the third trimester, and postpartum, respectively (P < 0.05 for either trimester vs postpartum). Median (range) C24 were 63 (37–225, n = 17), 56 (<10–181, n = 30), and 81 (<10–299, n = 28) ng/mL (P < 0.05 for either trimester vs postpartum). High variability in pharmacokinetic parameters was observed between subjects. Median (range) cord blood/maternal concentration ratio was 0.55 (0.3–0.8, n = 21). Delivery HIV-1 RNA was ⩽50 copies per milliliter in 70% and ⩽400 copies per milliliter in 90% of women. Cmin were significantly lower at 15 visits with detectable HIV-1 RNA compared with 61 visits with undetectable HIV-1 RNA, 29 (<10–93) vs 63 (15–200) ng/mL (P = 0.0001). Cmin was below the protein binding–adjusted EC90 concentration (12.2 ng/mL) at 4 visits in 3 of 31 women (10%). Conclusions:Rilpivirine exposure is lower during pregnancy compared with postpartum and highly variable. Ninety percent of women had minimum concentrations above the protein binding–adjusted EC90 for rilpivirine.

Routine CSF Analysis in Coccidioidomycosis Is Not Required

Although routinely done, there has been no evaluation of the utility of performing routine cerebrospinal fluid (CSF) examination in patients with active coccidioidomycosis and high complement fixation (IgG) antibody titers or other risk factors for disseminated infection. In our review 100% of patients diagnosed with coccidioidal meningitis had at least one sign or symptom consistent with infection of the central nervous system, headache was present in 100% of those with meningitis, while no patients without signs/symptoms of CNS infection were found to have coccidioidal meningitis, irrespective of antibody titers or other risk factors. Thus routine lumbar puncture may be unnecessary for patients with coccidioidomycosis who lack suggestive clinical symptoms.

Body Site Staphylococcus aureus Colonization among Maintenance Hemodialysis Patients

Background: Patients on maintenance hemodialysis therapy are at high risk for health care-associated infections. Staphylococcus aureus is a common cause of health care-associated infections among maintenance hemodialysis patients. It is established that S. aureus colonization is associated with an increased risk for subsequent infection in this population. There is an increasing number of reports that extranasal S. aureus colonization is more common than previously believed and in certain body sites even more common than nasal colonization. There are few data describing extranasal colonization among maintenance hemodialysis patients. Methods: We surveyed 100 patients at 3 body sites (anterior nares, oropharynx, and inguinal region) for S. aureus colonization. Participants were also administered a standardized survey to assess risk factors for S. aureus colonization. Results: We found that 42% (95% CI 32-52) of patients were S. aureus colonized in >1 body site. Extranasal colonization was found among 32% (95% CI 23-41). There were trends suggestive of an association between S. aureus colonization and younger age (OR 0.97, 95% CI 0.94-1.001, p = 0.06) and not having been hospitalized in the previous 12 months (OR 0.44, 95% CI 0.19-1.06, p = 0.14). Conclusion: Extranasal S. aureus colonization is common among maintenance hemodialysis patients with a prevalence of approximately one third. Future S. aureus decolonization efforts may need to consider not just nasal decolonization but also decolonization of the skin and oropharynx.

Adjunctive Corticosteroid Therapy in the Treatment of Coccidioidal Meningitis

Coccidioidal meningitis (CM) has high morbidity, and adjunctive measures to improve outcomes are needed. Using an established multicenter retrospective cohort study of CM (N = 221), we found that patients receiving adjunctive corticosteroids had a significant reduction in secondary cerebrovascular events (P = .0049). Those with CM-associated cerebrovascular events (8%) may benefit from short-term corticosteroids.

Nevirapine Plasma Concentrations in Human Immunodeficiency Virus-Exposed Neonates Receiving High-Dose Nevirapine Prophylaxis as Part of 3-Drug Regimen

We recently provided care for 3 human immunodeficiency virus (HIV)-exposed babies at high risk for perinatal acquisition of HIV. Since the first report of possible functional cure of 1 baby in Mississippi [1] with early triple-drug therapy of the newborn and the possible clearance of HIV from the peripheral blood of another infant [2], optimal management of high-risk, HIV-exposed infants is being reconsidered. Early initiation can suppress viremia and leads to a smaller number of infected cells as a reservoir for continued infection [3]. The International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) network is conducting a study to examine the potential utility of this approach for newborns exposed to HIV. Despite the recent information that the “Mississippi baby” has relapsed, there remains a need to evaluate the safety and effectiveness of high-dose nevirapine in neonates. Lack of such data for treatment doses of nevirapine in neonates complicates the potential enthusiasm for this approach. In this study, we present unique pharmacokinetic data on nevirapine plasma concentrations obtained in 3 newborns.

The Hyr1 protein from the fungus Candida albicans is a cross kingdom immunotherapeutic target for Acinetobacter bacterial infection

Different pathogens share similar medical settings and rely on similar virulence strategies to cause infections. We have previously applied 3-D computational modeling and bioinformatics to discover novel antigens that target more than one human pathogen. Active and passive immunization with the recombinant N-terminus of Candida albicans Hyr1 (rHyr1p-N) protect mice against lethal candidemia. Here we determine that Hyr1p shares homology with cell surface proteins of the multidrug resistant Gram negative bacterium, Acinetobacter baumannii including hemagglutinin (FhaB) and outer membrane protein A (OmpA). The A. baumannii OmpA binds to C. albicans Hyr1p, leading to a mixed species biofilm. Deletion of HYR1, or blocking of Hyr1p using polyclonal antibodies, significantly reduce A. baumannii binding to C. albicans hyphae. Furthermore, active vaccination with rHyr1p-N or passive immunization with polyclonal antibodies raised against specific peptide motifs of rHyr1p-N markedly improve survival of diabetic or neutropenic mice infected with A. baumannii bacteremia or pneumonia. Antibody raised against one particular peptide of the rHyr1p-N sequence (peptide 5) confers majority of the protection through blocking A. baumannii invasion of host cells and inducing death of the bacterium by a putative iron starvation mechanism. Anti-Hyr1 peptide 5 antibodies also mitigate A. baumannii /C. albicans mixed biofilm formation in vitro. Consistent with our bioinformatic analysis and structural modeling of Hyr1p, anti-Hyr1p peptide 5 antibodies bound to A. baumannii FhaB, OmpA, and an outer membrane siderophore binding protein. Our studies highlight the concept of cross-kingdom vaccine protection against high priority human pathogens such as A. baumannii and C. albicans that share similar ecological niches in immunocompromised patients.

Cryptococcus gattii Meningitis Complicated by Listeria monocytogenes Infection

LETTERS recommended breakpoint, we designed MHC1 with a colis- tin concentration of only 1 µg/mL to minimize false-nega- tive results. However, some colistin-susceptible organisms might grow on MHC1 (<5% in our study), resulting in the low PCR-positive rate for mcr-1 among isolates. Exact epidemiology of the mcr-1 gene is unknown, indicating a need to conduct accurate surveillance of the gene’s prevalence in humans. Additional mechanisms unique to the mcr-1 gene may contribute to colistin resis- tance, suggested by the wide variation in colistin MICs among mcr-1–carrying Enterobacteriaceae. This study was partially supported by the Health and Medical Research Fund, Food and Health Bureau, Hong Kong Special Administrative Region Government (reference nos. HKM-15-M10 and HKM-15-M12). References 1. Liu YY, Wang Y, Walsh TR, Yi LX, Zhang R, Spencer J, et al. Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study. Lancet Infect Dis. 2016;16:161–8. http://dx.doi.org/10.1016/S1473-3099(15)00424-7 2. Jorgensen JH, Pfaller MA, Carroll KC, Funke G, Landry ML, Richter SS, et al., editors. Manual of clinical microbiology, 11th ed. Washington: ASM Press; 2015. 3. Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. 25th edition. M100–S25. Wayne (PA): The Institute; 2015. 4. Cheng VC, Chan JF, Wong SC, Chen JH, Tai JW, Yan MK, et al. Proactive infection control measures to prevent nosocomial transmission of carbapenem-resistant Enterobacteriaceae in a non-endemic area. Chin Med J (Engl). 2013;126:4504–9. 5. Agriculture, Fisheries & Conservation Department. Hong Kong Special Administrative Region. Hong Kong: the facts. 2015 Feb [cited 2016 Jan 15]. http://www.gov.hk/en/about/abouthk/factsheets/ docs/agriculture.pdf 6. Census and Statistics Department. Hong Kong Special Administrative Region. Hong Kong merchandise trade statistics imports. 2015 Apr [cited 2016 Jan 15]. http://www.statistics.gov.hk/ pub/B10200012015MM04B0100.pdf 7. Falgenhauer L, Waezsada S-E, Yao Y, Imirzalioglu C, Kasbohrer A, Roesler U, et al.; RESET consortium. Colistin resistance gene mcr-1 in extended-spectrum β-lactamase-producing and carbapenemase- producing Gram-negative bacteria in Germany. Lancet Infect Dis. 2016;16:282–3. http://dx.doi.org/10.1016/S1473-3099(16)00009-8 8. Malhotra-Kumar S, Xavier BB, Das AJ, Lammens C, Butaye P, Goossens H. Colistin resistance gene mcr-1 harboured on a multidrug resistant plasmid. Lancet Infect Dis. 2016;16:283–4. http://dx.doi.org/10.1016/S1473-3099(16)00012-8 9. Tse H, Yuen KY. Dissemination of the mcr-1 colistin resistance gene. Lancet Infect Dis. 2016;16:145–6. http://dx.doi.org/10.1016/ S1473-3099(15)00532-0 10. European Committee on Antimicrobial Susceptibility Testing. Breakpoint tables for interpretation of MICs and zone diameters: version 6.0. 2016 Jan 1 [cited 2016 Mar 15]. http://www.eucast. org/fileadmin/src/media/PDFs/EUCAST_files/Breakpoint_ tables/v_6.0_Breakpoint_table.pdf Address for correspondence: Kwok-Yung Yuen, Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Pokfulam Rd, Pokfulam, Hong Kong, China; email: kyyuen@hku.hk Cryptococcus gattii Meningitis Complicated by Listeria monocytogenes Infection Robert G. Deiss, Michael Bolaris, Angel Wang, Scott G. Filler Author affiliations: Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA (R.G. Deiss); Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda (R.G. Deiss): Naval Medical Center of San Diego, San Diego, California, USA (R.G. Deiss); Harbor-UCLA Medical Center, Los Angeles, California, USA (M. Bolaris, A. Wang, S.G. Filler); David Geffen School of Medicine at UCLA, Los Angeles (S.G. Filler) DOI: http://dx.doi.org/10.3201/eid2209.160142 To the Editor: Among immunocompetent persons with cryptococcal disease, infection with a second organ- ism is rare; all reported cases have involved concomitant mycobacterial infections (1). Immunosuppression is not a necessary precondition for infection with Cryptococcus gattii (2), and among immunocompetent persons, C. gattii infection confers high mortality rates: up to 24% according to a large case series (3). In addition, cryptococcomas are frequently observed in patients with C. gattii, as opposed to C. neoformans, infection, commonly necessitating longer courses of treatment. We report a fatal case of C. gattii and Listeria monocytogenes co-infection in an immunocompe- tent woman with cryptococcomas. The patient was a previously healthy 23-year-old His- panic woman who was hospitalized in 2009 after weeks of headache and recent-onset diplopia. Lumbar puncture re- vealed elevated opening pressure of 52 cm H 2 O; elevated leukocytes (1,030 cells/μL: 31% neutrophils, 55% lym- phocytes, 14% monocytes); elevated protein concentra- tion (117 g/L); and decreased glucose concentration (30 mg/dL). Cerebrospinal fluid (CSF) cryptococcal antigen (CrAg) titer was 1:64, and culture grew C. gattii. HIV an- tibody test result was negative. Magnetic resonance imag- ing of the brain demonstrated scattered enhancing round lesions within the cerebrum and cerebellum, consistent with cryptococcomas. The patient was prescribed intrave- nous amphotericin B (1 mg/kg/d) and intravenous flucyto- sine (2 g/6 h) (Table); after 5 days of therapy, culture of a repeat lumbar puncture sample was negative. The patient was then given intravenous liposomal amphotericin at 7 mg/kg, and after a 14-day induction period she was dis- charged with instructions to take fluconazole orally (400 mg 2×/d) and to continue amphotericin B infusions (3×/ wk) (Table). Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 22, No. 9, September 2016