Bacterial infections

Nanomaterials based on phase change materials for antibacterial application

This review presented the applications of PCM-based nanomaterials in bacterial infections. Firstly, the composition and biotoxicity were outlined. Secondly, various antibacterial tactics were highlighted. Lastly, the perspectives were discussed.

Invasive non-typhoidal Salmonella infections in sub-Saharan Africa: a systematic review on antimicrobial resistance and treatment

BACKGROUND

Non-typhoidal Salmonella (NTS) are a frequent cause of invasive infections in sub-Saharan Africa. They are frequently multidrug resistant (co-resistant to ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol), and resistance to third-generation cephalosporin and fluoroquinolone non-susceptibility have been reported. Third-generation cephalosporins and fluoroquinolones are often used to treat invasive NTS infections, but azithromycin might be an alternative. However, data on antibiotic treatment efficacy in invasive NTS infections are lacking. In this study, we aimed to assess the spatiotemporal distribution of antimicrobial resistance in invasive NTS infections in sub-Saharan Africa and to describe the available evidence and recommendations on antimicrobial treatment.

METHODS

We conducted a systematic review of all available literature on antimicrobial resistance and treatment in invasive NTS infections. We performed a random effects meta-analysis to assess the temporal distribution of multidrug resistance, third-generation cephalosporin resistance, and fluoroquinolone non-susceptibility. We mapped these data to assess the spatial distribution. We provided a narrative synthesis of the available evidence and recommendations on antimicrobial treatment.

RESULTS

Since 2001, multidrug resistance was observed in 75% of NTS isolates from all sub-Saharan African regions (95% confidence interval, 70-80% and 65-84%). Third-generation cephalosporin resistance emerged in all sub-Saharan African regions and was present in 5% (95% confidence interval, 1-10%) after 2010. Fluoroquinolone non-susceptibility emerged in all sub-Saharan African regions but did not increase over time. Azithromycin resistance was reported in DR Congo. There were no reports on carbapenem resistance. We did not find high-quality evidence on the efficacy of antimicrobial treatment. There were no supranational guidelines. The "Access group" antibiotics ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol and "Watch group" antibiotics ceftriaxone, cefotaxime, and ciprofloxacin were recommended as the first-choice antibiotics in national guidelines or reviews. These also recommended (a switch to) oral fluoroquinolones or azithromycin.

CONCLUSIONS

In addition to the widespread multidrug resistance in invasive NTS infections in sub-Saharan Africa, resistance to third-generation cephalosporins and fluoroquinolone non-susceptibility was present in all regions. There was a lack of data on the efficacy of antimicrobial treatment in these infections, and supranational evidence-based guidelines were absent.

Serological Assessment of 18 Pathogens and Risk of AIDS-Associated Non-Hodgkin Lymphoma

BACKGROUND

HIV infection is associated with increased susceptibility to common pathogens, which may trigger chronic antigenic stimulation and hyperactivation of B cells, events known to precede the development of AIDS-associated non-Hodgkin lymphoma (AIDS-NHL).

METHODS

To explore whether cumulative exposure to infectious agents contributes to AIDS-NHL risk, we tested sera from 199 AIDS-NHL patients (pre-NHL, average lead time 3.9 years) and 199 matched HIV-infected controls from the Multicenter AIDS Cohort Study, for anti-IgG responses to 18 pathogens using multiplex serology. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression models.

RESULTS

We found no association between cumulative exposure to infectious agents and AIDS-NHL risk (OR 1.01, 95% CI: 0.91 to 1.12). However, seropositivity for trichodysplasia spinulosa polyomavirus (TSPyV), defined as presence of antibodies to TSPyV capsid protein VP1, was significantly associated with a 1.6-fold increase in AIDS-NHL risk (OR 1.62, 95% CI: 1.02 to 2.57). High Epstein-Barr virus (EBV) anti-VCA p18 antibody levels closer to the time of AIDS-NHL diagnosis (<4 years) were associated with a 2.6-fold increase in AIDS-NHL risk (OR 2.59, 95% CI: 1.17 to 5.74). In addition, high EBV anti-EBNA-1 and anti-ZEBRA antibody levels were associated with 2.1-fold (OR 0.47, 95% CI: 0.26 to 0.85) and 1.6-fold (OR 0.57, 95% CI: 0.35 to 0.93) decreased risk of AIDS-NHL, respectively.

CONCLUSIONS

Our results do not support the hypothesis that cumulative exposure to infectious agents contributes to AIDS-NHL development. However, the observed associations with respect to TSPyV seropositivity and EBV antigen antibody levels offer additional insights into the pathogenesis of AIDS-NHL.

Purification and characterization of a 630 kDa bacterial killing metalloprotease (KilC) isolated from plaice Pleuronectes platessa (L.), epidermal mucus

Antibacterial chemicals in the mucus of fish such as lysozyme, lectins, peptides and proteases provide an efficient first line of defence against pathogens. This study shows that there are at least three antibacterial proteins in plaice skin mucus in addition to lysozyme. One of these proteins is responsible for approximately 74% of the antibacterial activity and is a 630 kDa protease complex designated KilC (bacterial killing metalloprotease C). Purified KilC kills the bacteria Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa efficiently. The protease activity of KilC is dependent upon the divalent cation Mg(2+) and shows pH dual optima of 5.0 and 8.0. The enzyme has a temperature optimum of 25 degrees C and is made up of at least five different sized peptides. Studies with protease inhibitors show that the catalytic site of KilC may be cysteine- or serine protease-like. KilC may kill bacterial cells by acting directly upon the bacteria or by producing low molecular weight bioactive compounds such as peptides.

Epidemiology and microbiology of cellulitis and bacterial soft tissue infection during HIV disease: a 10-year survey

BACKGROUND

Cellulitis and soft tissue infection are underestimated complications of HIV disease.

PATIENTS AND METHODS

Sixty-seven bacteriologically proven consecutive episodes were identified among 2221 HIV-infected patients hospitalized in a 10-year period, and assessed according to several epidemiological, microbiological and clinical variables.

RESULTS

Staphylococcus aureus was the most frequently cultured pathogen (50% of 92 isolates), followed by Pseudomonas spp., Escherichia coli and Streptococcus pyogenes; a polymicrobial infection was present in 38.1% of episodes. Drug addiction (p < 0.003) and male gender (p < 0.04) were significantly associated with the occurrence of these complications, which were community-acquired in 83.6% of cases. While a remarkable variation in the severity of underlying immunodeficiency was shown, hematogenous dissemination occurred in 25.4% of episodes, and proved significantly related to a low CD4+ lymphocyte count, and neutropenia. A 21.7% methicillin-resistance rate was shown among S. aureus isolates. All episodes were favorably treated in 5-16 days, in over 60% of cases with associated beta-lactam-aminglycoside antibiotics; a recurrence of staphylococcal cellulitis occurred in four patients only.

CONCLUSION

Skin and soft tissue infections are continuing causes of morbidity in HIV-infected patients, even in the highly active antiretroviral therapy era.

Bacteremia in hospitalized patients with human immunodeficiency virus: A prospective, cohort study

BACKGROUND

Bacterial infections complicate the course of patients with human immunodeficiency virus infection. The purpose of this study was to describe the bacterial pathogens causing blood stream infection, identify the risk factors for the development of blood stream infection and determine the impact of blood stream infection on the outcome of patients infected with human immunodeficiency virus.

METHODS

The incidence, etiology, risk factors and outcome of bacterial blood stream infection were prospectively determined in 1,225 consecutive hospitalizations of adults with human immunodeficiency virus infection.

RESULTS

Blood stream infection occurred in 88 hospitalizations (7%); 73 of 89 infections (82%) were community acquired. The most commonly isolated gram-positive organism was Streptococcus pneumoniae (21); gram-negative, Escherichia coli (14). Blood stream infection was detected in 8% of African Americans and 22% of Hispanics compared with 2% of whites (P = 0.0013). Patients with blood stream infection had higher white blood cell counts (median, 6.5 vs. 4.9 x 109/L; P = 0.0002) and mortality (18% vs. 4%; P < 0.0001) than patients without infection.

CONCLUSIONS

In patients with human immunodeficiency virus, blood stream infection is associated with an increased mortality rate. Recognition of the incidence, etiology, and risk factors of blood stream infection in patients with human immunodeficiency virus infection could lead to measures that reduce the increased mortality.

Disseminated nocardiosis in a patient with X-linked chronic granulomatous disease and human immunodeficiency virus infection

We report the first case of HIV infection in a patient with underlying X-linked chronic granulomatous disease (CGD) who presented with hepatopulmonary nocardiosis. Despite the coexistence of CGD and HIV, the response to therapy was normal, and no unusual sequelae were noted. The patient's high virus burden was successfully repressed with antiretroviral therapy, suggesting that the nicotinamide adenine dinucleotide phosphate oxidase system is not essential for active viral replication or response to antiretroviral agents.

Enterobacter spp. infections complicating the course of HIV disease

Through a retrospective review of clinical and laboratory data of 2517 consecutive patients with HIV disease hospitalized since 1991, 13 patients were identified (0.52%), who suffered from a confirmed Enterobacter spp. infection (urinary tract disease in 7 cases, sepsis in 4 patients, and pneumonia in 2 cases). A severe immunodeficiency was recognized in all cases, as expressed by a mean CD4+ lymphocyte count <60 cells/microL, and frequently, a prior diagnosis of AIDS. Bloodstream infection proved linked to a lower mean CD4+ cell count, a more frequent occurrence of leukopenia-neutropenia, and nosocomial origin of the infecting pathogen. Hospital-acquired Enterobacter spp. disease was more frequent than community-acquired, and was significantly associated with leukopenia-neutropenia, and a diagnosis of AIDS. Antibiotic susceptibility assays showed a resistance rate to ampicillin and cephalothin involving >90% of tested strains, and a higher (but varied) sensitivity to other beta-lactams, aminoglycosides, fluoroquinolones, and cotrimoxazole. Adequate chemotherapy provided clinical and bacteriological success in all evaluated patients, in the absence of mortality or relapses. Only 34 episodes of HIV-associated Enterobacter spp. infection have been reported to date in 11 different literature studies. Our data point out that also Enterobacter spp. organisms may have an appreciable pathogenic potential in patients with HIV disease, especially in those with a low CD4+ lymphocyte count, leukopenia-neutropenia, who are hospitalized. Despite the unpredictable antibiotic susceptibility profile of these organisms, HIV-related Enterobacter spp. disease may be properly managed through rapid identification and timely and appropriate antimicrobial treatment.

Moraxella catarrhalis pneumonia during HIV disease

To assess the role of Moraxella catarrhalis complications in the setting of HIV disease, and to evaluate their occurrence and outcome according to several epidemiological, clinical, and laboratory parameters, the clinical records of 2123 consecutive HIV-infected patients hospitalized in a 9-year period were retrospectively reviewed, and 4 cases of community-acquired M. catarrhalis pneumonia were identified. Three adult patients had a diagnosis of AIDS and severe concurrent immunodeficiency (with a CD4+ lymphocyte count below 60 cells/microL), while the fourth case involved a child with vertical HIV disease. Leukopenia and neutropenia were never present, but no patient received a potent antiretroviral regimen at the time of disease onset. A concurrent respiratory infection by Streptococcus pneumoniae and Mycobacterium tuberculosis was recognized in 2 of 4 patients. Isolated M. catarrhalis strains were susceptible to all tested antimicrobial compounds (save ampicillin in 2 cases), and appropriate antimicrobial treatment led to clinical and microbiological cure in all described episodes. Only 8 cases of HIV-associated Moraxella spp. disease have been reported to date in seven different literature reports (6 cases of pneumonia, and 1 of septicemia). According to our experience, M. catarrhalis may be responsible for appreciable morbidity among patients with advanced HIV infection, especially when a low CD4+ cell count or coexisting respiratory disease are present. Clinicians and microbiologists who care for HIV-infected patients should carefully consider the potential pathogenic role of Moraxella spp. organisms.

Pseudomonas spp. complications in patients with HIV disease: an eight-year clinical and microbiological survey

Two hundred and twenty-four episodes of Pseudomonas spp. complications that occurred in 179 consecutive patients with HIV infection were retrospectively reviewed. Pseudomonas spp. organisms were responsible for 11.6% of 1933 episodes of non-mycobacterial bacterial diseases (5.4% of 1072 episodes of sepsis), observed over an 8-year period; 20.7% of patients experienced disease relapses (45 episodes). These complications mostly involved lower airways (66 cases), urinary tract (53 episodes), and blood (34 cases), with Pseudomonas aeruginosa isolated in 161 episodes, and other Pseudomonas spp. in the remaining 63 cases. An advanced HIV disease was frequently present (as expressed by a prior diagnosis of AIDS, a low CD4+ lymphocyte count, and leukopenia-neutropenia). Indwelling intravascular and urinary catheters were often associated with bacteremia and urinary tract involvement, respectively. More than 60% of patients were given antibiotics and/or cotrimoxazole in the month preceding the onset of Pseudomonas spp. disease. Bacterial strains isolated from our HIV-infected patients showed a favorable sensitivity to piperacillin, ceftazidime, imipenem, amikacin, tobramycin, and ciprofloxacin. An adequate antimicrobial treatment led to clinical and microbiological cure in 73.2% of patients at the first episode, and in 22.3% more subjects after one or more relapses. A lethal outcome occurred in only eight patients of 179 (4.5%), suffering from a far advanced HIV disease; P. aeruginosa infection directly contributed to death in four cases (sepsis, and/or pneumonia). Nosocomial disease occurred in 46.4% of the 224 episodes, and was significantly related to a previous diagnosis of AIDS, concurrent neutropenia, the occurrence of sepsis or urinary tract infection, disease relapses, the involvement of non-aeruginosa Pseudomonas spp., and a lethal outcome, compared with community-acquired infection. Our experience (the largest reported to date) confirms that Pseudomonas spp. (including non-aeruginosa Pseudomonas spp. organisms) is responsible for remarkable morbidity and mortality among patients with HIV infection, and may pose relevant problems to clinicians and microbiologists involved in the care of HIV-infected patients.

Flavobacterium spp. organisms as opportunistic bacterial pathogens during advanced HIV disease

OBJECTIVE

To assess the role of Flavobacterium spp. infection in patients with HIV disease.

METHODS

Clinical charts of 2412 consecutive HIV-infected patients hospitalized in a 8-year period were retrospectively reviewed, to identify all cases of Flavobacterium spp. infections, and to evaluate their occurrence and outcome according to several epidemiological, clinical, and laboratory parameters.

RESULTS

Six patients out of 2412 (0.25%), developed Flavobacterium spp. complications: septicaemia in five cases, and pneumonia in the remaining patient, with F. meningosepticum and F. odoratum isolated in two cases and one case, respectively, and unnamed Flavobacterium spp. organisms in the remaining three cases. Flavobacterium spp. organisms were responsible for six out of 1939 overall episodes of non-mycobacterial bacterial diseases observed in our patient group (0.31%). All patients were severely immunocompromised, showing a prior diagnosis of AIDS, a mean CD4+ lymphocyte count of 64.2 (range 12-187) cells/microl, and a mean neutrophil count of 1.143 (range 700-1600) cells (range 700-1600) cells/microl. Antibiotic, corticosteriod, or cotrimoxazole treatment was carried out during the month preceding disease onset by three, two and five patients, respectively. Community-acquired and nosocomial Flavobacterium spp. disease were equally frequent, but the latter occurred with a significantly lower mean neutrophil and CD4+ cell count. Antimicrobial susceptibility assays showed complete sensitivity to ciprofloxacin, and variable resistance to ureidopenicillins, ceftazidime, imipenem, aztreonam, and aminoglycosides. An appropriate antimicrobial regimen obtained clinical and microbiological cure in all cases, in absence of related mortality or relapses.

CONCLUSIONS

Since only one episode of HIV-associated F. (Sphingobacterium) multivorum complication has been described to date, our series represents the largest one dealing with Flavobacterium spp. infection in the setting of HIV disease. Our experience suggests that Flavobacterium spp. organisms may play a pathogenic role in patients with advanced HIV disease, even when some commonly recognized risk factors are lacking (i.e. indwelling catheters, instrumentation, IV drug abuse), while a very low CD4+ lymphocyte count, leukopaenia-neutropaenia, and concurrent AIDS-related infectious complications may act as important predisposing factors. In view of the infrequent occurrence of these infections, early suspicion is essential for both clinicians and microbiologists facing immunocompromised patients at risk for invasive bacterial complications. Flavobacterium spp. organisms should be taken into consideration as nosocomial- or community-acquired opportunistic pathogens, due to their relationship with advanced immunodeficiency and their elevated resistance to many antimicrobial agents commonly used against Gram-negative bacterial pathogens.

Typhoid fever and HIV infection: a rare disease association in industrialized countries

Typhoid fever is still a global health problem, mainly in tropical and subtropical areas of the world and in developing countries, where relatively elevated morbidity and mortality rates still are present, mostly because of persisting poor hygienic conditions. In the majority of Mediterranean regions, including Italy, the disease is constantly present, though with a low prevalence rate, as a result of an endemic persistence of Salmonella typhi infection.1-4 On the other hand, in industrialized countries, most cases of S. typhi infection are related to foreign travel or prior residence in endemic countries.4-6 In the United States, 2445 cases of typhoid fever have been reported in the decade 1985 to 1994, and the annual number of cases remained relatively stable over time: over 70% of episodes were acquired in endemic countries (mostly Mexico and India).6 The persisting morbidity of S. typhi also may be supported by the increasing resistance rate of this pathogen against a number of commonly used antimicrobial compounds. For instance, 6% of 331 evaluable S. typhi strains were resistant to ampicillin, chloramphenicol, and cotrimoxazole, and 22% of isolates were resistant to at least one of these three agents in a recent survey performed in the United States.6 The spread of antibiotic resistance among S. typhi isolates is emerging in many countries, and multidrug-resistant strains have been isolated, as well as isolates with poor susceptibility to fluoroquinolones,3-5,7-9 so that in vitro susceptibility should be determined for all cultured strains, and antimicrobial treatment should be adjusted accordingly. Nevertheless, fluoroquinolones (e.g., ciprofloxacin and pefloxacin) or third-generation cephalosporins, still represent the best choice for empirical treatment,2,4,6-8,10 and mortality remains rare in Western countries (less than 1% of episodes), although it is expected to be greater in developing areas of the world. The aim of this report is to describe two cases of typhoid fever that occurred in patients with human immunodeficiency virus (HIV) infection, a rarely reported disease association in industrialized countries.

Bacteremia and respiratory involvement by Alcaligenes xylosoxidans in patients infected with the human immunodeficiency virus

Seven cases of Alcaligenes xylosoxidans bacteremia and/or respiratory disease in patients infected with the human immunodeficiency virus (HIV) are described. Reported only thrice previously in this setting, these bacterial complications occurred during different phases of HIV infection and were associated with leukopenia-neutropenia in four patients and a central vascular catheter in two. Although the majority of cases were diagnosed after day 3 of hospitalization, a distinct source of infection was never identified. In four patients with advanced underlying disease, a polymicrobial infection was present. In vitro resistance to aminoglycosides, first-generation cephalosporins, and aztreonam was identified, but treatment with fluoroquinolones, piperacillin, or an aminoglycoside in combination with either ceftazidime or pefloxacin was successful in all cases. The relevance of Alcaligenes xylosoxidans and related species of gram-negative non-glucose fermenting bacilli as opportunistic pathogens in the immunocompromised host and in the setting of HIV infection is briefly reviewed.