Age structure, blood-feeding behavior, and Leishmania chagasi infection in Lutzomyia longipalpis (Diptera: Psychodidae) at an endemic focus of visceral leishmaniasis in Colombia

Ecological studies on the sand fly Lutzomyia longipalpis (Lutz & Neiva) were conducted during 1990-1992 in a small rural community in Colombia where American visceral leishmaniasis (AVL) is endemic. Subsamples of sand flies collected weekly from pigpens, the interior of houses, and natural outdoor resting sites were dissected to determine physiological age and Leishmania chagasi Cunha & Chagas infection rates. Eleven female L. longipalpis had flagellates in their gut, 2 of which were successfully cultured and identified as Leishmania chagasi. The reproductive status, stage of ovarian development, and trophic history of female sand flies varied among sites, habitats, and time of collection. The percentage of parous females ranged from about one-third to two-thirds overall and varied seasonally. Of most relevance to AVL transmission was the finding that 8% of L. longipalpis females were multiparous. In addition, our data suggest that L. longipalpis rest inside houses after blood-feeding outdoors, and that this species can blood-feed more than once during a single gonotrophic cycle.

Comparison of recovery rates for mycobacteria from BACTEC 12B vials, Middlebrook 7H11-selective 7H11 biplates, and Lowenstein Jensen slants in a public health mycobacteriology laboratory

Recovery rates from Middlebrook 7H11-selective 7H11 biplates and Lowenstein-Jensen slants (LJ) used with BACTEC 12B vials were compared for 5,399 specimens. For 578 specimens that were inoculated onto three media, 580 mycobacteria were isolated, including 277 (48%) Mycobacterium avium complex isolates, 230 (40%) Mycobacterium tuberculosis isolates, and 73 (12%) other mycobacteria. For BACTEC 12B vials, 506 (87%) cultures were positive, 45 (8%) were negative, and 29 (5%) were lost to contamination; for 7H11-7H11-selective biplates, 469 (81%) cultures were positive, 95 (16%) were negative, and 16 (3%) were lost to contamination; for LJ, 230 (40%) cultures were positive, 111 (19%) were negative, and 239 (41%) were lost to contamination. For routine cultures, use of plate media is superior to use of LJ.

Controlled evaluation of BacT/alert standard anaerobic and FAN anaerobic blood culture bottles for the detection of bacteremia and fungemia

FAN medium was formulated to improve microbial recovery, particularly for fastidious microorganisms and for microorganisms causing sepsis in patients receiving antimicrobial therapy. In a controlled clinical evaluation performed at four university-affiliated hospitals, FAN anaerobic bottles were compared with standard anaerobic bottles for yield, speed of detection of microbial growth, and detection of septic episodes. A total of 10,431 blood culture sets were received; both anaerobic bottles of 7,694 blood culture sets were adequately filled with blood. Altogether, 925 isolates were recovered: 557 that were the cause of sepsis, 99 that were indeterminate as the cause of sepsis, and 269 contaminants. More Staphylococcus aureus (P < 0.001), coagulase-negative staphylococci (P < 0.001), Escherichia coli (P < 0.02), and all microorganisms combined (P < 0.005) were recovered from FAN bottles; more nonfermentative gram-negative bacilli (P < 0.05), Torulopsis glabrata (P < 0.001), and other yeasts (P < 0.01) were recovered from standard bottles. Growth of S. aureus (P < 0.001), coagulase-negative staphylococci (P < 0.001), Enterococcus faecalis (P < 0.025), streptococci other than Streptococcus pneumoniae (P < 0.01), and all microorganisms combined (P < 0.001) was detected earlier in standard bottles; growth of more isolates of E. coli (P < 0.05) and anaerobic bacteria (P < 0.01) was detected earlier in FAN bottles. The mean times to detection were 14.2 and 16.1 h for standard and FAN bottles, respectively. More septic episodes caused by S. aureus (P < 0.001), coagulase-negative staphylococci (P < 0.005), members of the family Enterobacteriaceae (P < 0.02), and all microorganisms combined (P < 0.02) were detected in FAN bottles; more septic episodes caused by nonfermentative gram-negative bacilli (P < 0.025) and yeasts (P < 0.005) were detected in standard bottles. In summary, more isolates (except for strict aerobes) were recovered from FAN bottles than from standard anaerobic bottles. Similarly, significant more septic episodes (except for those caused by strict aerobes) were detected with FAN bottles than with standard anaerobic bottles. With the exception of E. coli and anaerobic bacteria, growth of more isolates was detected earlier in standard anaerobic bottles.

Nocturnal activity patterns of Lutzomyia longipalpis (Diptera: Psychodidae) at an endemic focus of visceral leishmaniasis in Colombia

Nocturnal activity of the sand fly Lutzomyia longipalpis (Lutz & Neiva) was studied from August 1991 to July 1992 in a small rural community in Colombia where American visceral leishmaniasis is endemic. During 2 or 3 nights each month, sand flies were collected with hand-held aspirators each hour between 1730 and 0630 hours, from a pigpen and a cattle corral located 30 m apart. Host-seeking activity of L. longipalpis adults was characterized by 2 general patterns: (1) adult sand fly activity increased shortly after sunset and continued until just after sunrise, and (2) peak sand fly activity was greatest early in the evening (1830-2330 hours) and then declined steadily toward morning. Female L. longipalpis activity generally increased after 2030 hours, whereas that of males remained constant or declined as the evening progressed. There were seasonal differences in sand fly abundance between the 2 sites: peak abundance in the cattle corral occurred during hot, dry periods, whereas maximum abundance in the pigpen occurred when relative humidity was higher. Influence of relative humidity on activity varied with season. Sand fly activity tended to decrease at temperatures below 24 degrees C and increase in the presence of moonlight.

Species composition and relative abundance of sand flies of the genus Lutzomyia (Diptera: Psychodidae) at an endemic focus of visceral leishmaniasis in Colombia

Ecological studies on the sand fly Lutzomyia longipalpis (Lutz & Neiva) were conducted during 1990-1993 at a small rural community in Colombia where American visceral leishmaniasis is endemic. Weekly sand fly collections were made from pigpens, houses, and natural resting sites, using hand-held aspirators, sticky (oiled) paper traps, and opossum-baited Disney traps. In total, 263,094 sand flies were collected; L. longipalpis predominated (86.1%), followed by L. trinidadensis (11.0%), L. cayennensis (2.7%), and 8 other Lutzomyia species. The species composition and sex ratio of these sand flies varied among sites and by collection method. L. longipalpis were captured most efficiently by direct aspiration from animal bait. Conversely, sticky paper traps, especially inside houses and at rock resting sites, collected a greater diversity of species, but a lower relative abundance of L. longipalpis.

Seasonal abundance of Lutzomyia longipalpis (Diptera: Psychodidae) at an endemic focus of visceral leishmaniasis in Colombia

Ecological studies on the sand fly Lutzomyia longipalpis (Lutz & Neiva) were conducted during 1990-1993 in a small rural community in Colombia where American visceral leishmaniasis is endemic. Standardized weekly sand fly collections made from pigpens and natural resting sites displayed a bimodal annual abundance cycle, with a small peak occurring in October-November and a larger one in April-May. Time series analysis was employed to quantify the associations between sand fly abundance and weather factors (temperature, relative humidity, and rainfall). In addition to a prominent 6-mo cycle. Fourier analysis of the collection data demonstrated that the L. longipalpis population also exhibited a 5- to 8-wk cycle that may represent the length of larval development. Autoregressive moving average models were fit to weekly collection data and their residuals were regressed against rainfall, temperature, and relative humidity. A significant positive association between female L. longipalpis abundance and the relative humidity and rainfall recorded 3 wk earlier was found, indicating that these factors may be of value in predicting sand fly abundance. Additionally, these data indicated that L. longipalpis larvae may become quiescent during adverse conditions.

Polymerase chain reaction and culture confirmation of disseminated Encephalitozoon cuniculi in a patient with AIDS: successful therapy with albendazole

Infections due to microsporidia are being recognized increasingly, especially in AIDS patients. A patient with disseminated microsporidiosis with advanced renal failure due to Encephalitozoon cuniculi (confirmed by culture and polymerase chain reaction [PCR]) is described. The organism from urine and sputum was characterized by culture, Weber's chromotrope-based staining, transmission electron microscopy, and indirect immunofluorescence (IIF) tests. PCR was done on DNA extracted from the infected cell cultures. Treatment with albendazole resulted in improvement in serum creatinine levels, complete disappearance of spores from sputum, a negative urine culture, and a 3-log decline in the number of spores in the urine, as evidenced by chromotrope-based staining. IIF and PCR were used to confirm E. cuniculi as the etiologic agent. Our findings indicate that disseminated microsporidiosis with renal failure in AIDS is treatable.

Controlled evaluation of BacT/Alert standard aerobic and FAN aerobic blood culture bottles for detection of bacteremia and fungemia

A new medium, FAN, designed to enhance the recovery of microorganisms, has been developed for the BacT/Alert blood culture system (Organon Teknika Corp., Durham, N.C.). We compared the yield and speed of detection of microorganisms in 6,847 adequately filled paired aerobic standard and FAN bottles at four university hospitals. Of 499 clinically significant microorganisms isolated from one or both bottles, significantly more Staphylococcus aureus isolates (P < 0.001), coagulase-negative staphylococci (P < 0.001), yeasts (P < 0.01), and all microorganisms combined (P < 0.001) were recovered from the FAN bottles. Overall, the speeds of detection of positive cultures did not differ between the two medium formulations; mean times to detection in the standard and FAN bottles were 16.1 and 16.0 h, respectively. When a subset of patients on antimicrobial therapy was evaluated, significantly enhanced yield from the FAN bottle was evident for staphylococci. Overall, the FAN bottle outperformed the standard aerobic BacT/Alert bottle.

Laboratory and clinical evaluation of Mycobacterium xenopi isolates

Mycobacterium xenopi and Mycobacterium avium complex (MAC) are biochemically similar. To define the laboratory characteristics of M. xenopi that distinguish it from MAC, 53 M. xenopi isolates from different areas in the United States and 47 isolates recovered at one hospital were evaluated by 13 biochemical tests, AccuProbe MAC (Gen-Probe, Inc., San Diego, CA, USA), colony morphology, formation of X-colonies, pigmentation in response to light, growth on MacConkey agar without crystal violet, and relative growth rates at 25 degrees C, 36 degrees C, and 45 degrees C on solid media. Relative growth rates of 10 M. xenopi and 11 MAC isolates were measured at 25 degrees C, 36 degrees C, and 42 degrees C in Middlebrook broth processed using the BACTEC TB System. Ten M. xenopi were tested for p-nitro-alpha-acetylamino-beta-hydroxypropiophenone inhibition at 36 degrees C and 42 degrees C. Reevaluation of 81 isolates previously identified as MAC by biochemical tests alone revealed that two were M. xenopi. The most reliable characteristics distinguishing M. xenopi from MAC were the presence of X-colonies (M. xenopi 97% vs MAC 1%), positive 3-day arylsulfatase (M. xenopi 88% vs MAC 1%), growth at 25 degrees C (M. xenopi 0% vs MAC 100%), and AccuProbe MAC test results (M. xenopi 0% hybridized). Retrospective chart review of 37 patients using American Thoracic Society criteria revealed that six (16%) patients had clinically important isolates. At one of our hospitals M. xenopi was the second most common mycobacterial species isolated for 1990-1992, accounting for 27% of all isolates, whereas at our other hospital it accounted for 1% of isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

Host-passage-induced phenotypic changes in crimean-congo haemorrhagic fever virus

Changes in virulence of Crimean-Congo haemorrhagic fever (CCHF) virus toward intracerebrally inoculated suckling mice (SM) were studied in relation to different host-passage histories. Two CCHF virus strains, one isolated from a human and the other from a tick, were passaged through various vertebrate and tick hosts and then reisolated and tested for their virulence toward SM. In various experiments, SM were inoculated with 12 different viral suspensions, each having a specific passage history. Survival curves of SM, which may reflect differences in viral strain characters, were established using an actuarial life table; differences were evaluated with the log-rank test. Regardless of the origin of the strain, CCHF viruses exhibited pathogenicity when passaged among SM. However, virulence, as measured by the proportion of deaths in SM, was altered following passage through another vertebrate host or tick. The final host seems to have a major influence on virulence. Because CCHF virus strains appear to vary little in their antigenic characters, it is hypothesized that hosts can induce phenotypic changes that modulate viral virulence.

Multifocal cellulitis and monoarticular arthritis as manifestations of Helicobacter cinaedi bacteremia

Helicobacter cinaedi (formerly Campylobacter cinaedi) was first detected in the fecal flora of homosexual men. Since 1984, 11 case reports of H. cinaedi bacteremia have been published; most cases have presented as a nonspecific febrile illness in homosexual men infected with the human immunodeficiency virus (HIV). We identified seven additional cases of H. cinaedi bacteremia in two Denver hospitals within a 5-year period, which suggests that this illness is not as rare as was previously thought. Six of these cases of H. cinaedi bacteremia occurred in homosexual men who were infected with HIV. Four patients presented with the distinctive cutaneous manifestation of multifocal cellulitis, and two patients had monoarticular arthritis. Microbiological diagnosis of this infection was delayed by the slow growth of the bacterium in nonradiometric blood culture bottles. Although the patients' bacteremia was prolonged, their response to treatment was excellent. In contrast to campylobacter infections in HIV-infected patients, H. cinaedi bacteremia did not relapse after a course of effective therapy. H. cinaedi bacteremia should be suspected in HIV-infected individuals who present with an indolent febrile illness, particularly in the presence of multifocal cellulitis and/or arthritis.

Clinical impact of bacteria and fungi recovered only from broth cultures

We prospectively evaluated 356 bacteria and fungi recovered from broth enrichment tubes from cultures with sterile direct plates to determine the clinical impact of isolates recovered only from broth cultures. These "broth only" isolates (BOI) were classified as contaminants or true on the basis of review of patient charts. True isolates were considered clinically relevant only if they altered or should have altered patient management. Of 356 BOI, 259 (73%) were considered contaminants (mostly coagulase-negative staphylococci and Propionibacterium spp.) and 97 (27%) were considered true. For individual microorganisms, 9 of 9 (100%) Staphylococcus aureus isolates, 13 of 13 (100%) members of the family Enterobacteriaceae, 10 of 12 (83%) fungi, 7 of 10 (70%) enterococci, 7 of 11 (64%) other gram-negative bacilli, 13 of 31 (45%) anaerobic bacteria, 10 of 24 (42%) streptococci, 22 of 140 (16%) coagulase-negative staphylococci, 6 of 92 (7%) Propionibacterium spp., and 0 of 14 (0%) diphtheroids and Bacillus spp. were classified as true. Eleven of 97 (11%) patients with true BOI had clinically relevant isolates. Fifty-nine of the 97 (61%) patients with true isolates already were on therapy, and no change was made because of the BOI. Six (6%) patients with contaminants received therapy for their BOI. We conclude that broth inoculated as an adjunct to direct plating seldom yields results that favorably alter patient management and could be omitted for most specimens without compromising patient care.

Controlled evaluation of 5 versus 10 milliliters of blood cultured in aerobic BacT/Alert blood culture bottles

Bottles developed for use in the BacT/Alert automated blood culture system (Organon Teknika Corp., Durham, N.C.) can accept up to 10 ml of blood without falling below a 1:5 ratio of blood to broth. We compared the yield and speed of detection of microorganisms in 13,128 adequately filled, paired, aerobic bottles inoculated with 5 versus 10 ml of blood at three university hospitals. A total of 798 microorganisms causing sepsis grew in one or both bottles. The overall recovery of microorganisms from 10-ml samples exceeded that from 5-ml samples (P < 0.001); the increased yield attributed to the additional 5 ml in the samples was 7.2%. The increased yield from 10-ml inocula was most marked for Escherichia coli (P < 0.01) and other members of the family Enterobacteriaceae (P < 0.001). Ten-milliliter samples did not yield more gram-positive bacteria, nonfermentative gram-negative rods, or yeasts. When both bottles were positive, the bottles inoculated with 10 ml of blood showed growth sooner (P < 0.001). Earlier detection with 10-ml inocula was especially notable for coagulase-negative staphylococci (P < 0.001), streptococci (P < 0.001), E. coli (P < 0.025), and other members of the family Enterobacteriaceae (P < 0.025). We conclude that an increase in the volume of blood inoculated into BacT/Alert aerobic blood culture bottles from 5 to 10 ml will increase the overall yield and the speed of detection of clinically important blood pathogens.

Rift Valley fever in rural northern Senegal: human risk factors and potential vectors

To investigate past infection in and transmission of Rift Valley fever (RVF) virus to humans within an endemic focus, we undertook a retrospective cohort study of the seminomadic Peul people living in sub-Saharan northcentral Senegal. Residents of the rural settlement of Yonofere five years of age or older were studied during February-May 1989. Anti-RVF virus IgG was found in blood samples of 22.3% of 273 persons who responded to a standard questionnaire; none had IgM antibodies. Seropositivity was similar for males (25.4%) and females (21.1%), increased markedly with age for both sexes, and varied considerably among compounds (groups of huts) (0-37.5%). Risk factors for past RVF virus infection were nursing sick people, assisting animals during abortions/births, and treating sick animals. In all age groups, odds ratios (ORs) for RVF viral antibody among females who reported treating sick animals were three to six times greater than for those who did not. The ORs for males who reported assisting with animal births/abortions and nursing sick people were approximately five times those for males who did not. Serologic prevalence of RVF viral antibody among sheep averaged 30.1% overall (0.8% IgM), but varied among compounds (0-66.7%) in a manner different from that of humans. The seasonal abundance and relative density of potential mosquito vectors were estimated by monthly samples captured in Centers for Disease Control and Prevention-type traps. Mosquito abundance varied seasonally with rainfall (> 90% captures during four months). Species diversity was large (28 spp.), dominated by Aedes and Culex. Rift Valley fever virus was not isolated from 142 pools of 2,956 unengorged mosquitoes tested, although three other arboviruses were found. Results indicate that RVF is endemic in this region, people are at considerable risk of infection, and that a heretofore unrecognized mode of human infection under nonepizootic conditions may be transmission via contact with infected animals or humans.

Blood cultures. Introduction

Clinical microbiologists must be able to evaluate critically the blood culture literature for patient care purposes, for sound laboratory management, and for decision making in regards to purchase or lease of a new system. This skill has never been more important due to the many new commercially available blood culture products and technologies. Critical assessment of the literature requires familiarity with blood culture terminology and an understanding of those factors critical in designing scientifically valid clinical evaluations.

General principles in the laboratory detection of bacteremia and fungemia

Various factors are important in the laboratory detection of bacteremia and fungemia. These include clinical factors, the type of blood culture system, and laboratory processing of blood culture bottles. Most commercial blood culture products have been designed to take these factors into account and, thus, are relatively similar. There are differences, however, and it should not be assumed that these products have identical performance characteristics. To optimize microbial recovery, clinicians should order and collect the proper number of blood cultures at the earliest possible time and before the administration of antimicrobial agents. Clinical microbiologists should select a blood culture system that optimizes the recovery of common microbial pathogens and should use blood culture systems according to the manufacturers' recommendations.

Automated blood culture systems

For the first time, clinical microbiologists have the option of purchasing or leasing a variety of automated blood culture systems. Although the performance characteristics of the BACTEC radiometric and nonradiometric blood culture systems are well-documented, we are only beginning to learn the performance characteristics of CMBCS. Well-designed and executed controlled clinical trials are needed to establish performance characteristics and to address issues that are unique to CMBCS. In particular, controlled clinical comparisons of different CMBCS are needed. In terms of the impact on clinical microbiology laboratories, there are no published data to support claims that the use of these systems decreases laboratory workload, staffing, or costs. Although such an impact seems reasonable and even likely, unequivocal documentation of such savings would make it easier for many laboratorians to justify the cost of purchasing or leasing one of these systems. Similarly, there are no published data regarding the long-term reliability of these systems while in clinical use. A documented track record of mechanical and electrical reliability would be useful to clinical microbiologists contemplating the acquisition of a new blood culture system.

Utility of paired blood cultures and smears in diagnosis of disseminated Mycobacterium avium complex infections in AIDS patients

For 273 patients evaluated for disseminated Mycobacterium avium complex infection, a total of 1,047 mycobacterial blood cultures (MBCs) were submitted; the M. avium complex was recovered from 140 (13%) of the specimens. Results for the paired MBCs were highly concordant: in 392 of 462 (85%) culture sets, both MBCs were negative, in 53 of 462 (11%) sets, both MBCs were positive, and in only 17 of 462 (4%) sets was one culture positive and the other negative. Acid-fast smears were done on sediments from 671 specimens; smears were positive for 4 of 98 (4%) cultures that grew the M. avium complex. A single MBC should be obtained and then repeated if negative and disseminated M. avium complex infection is still clinically suspected. Use of direct acid-fast smears of sediments is not a reliable means of detecting mycobacteremia.

Recovery of select rare and fastidious microorganisms from blood cultures

Most, if not all, rare or fastidious microbial pathogens can be recovered from standard blood culture bottles and media using routine laboratory methods. Because they are only rarely recovered from blood cultures, relatively few data exist concerning the ability of different blood culture systems to recover these microorganisms. Thus, clinical microbiologists should take a conservative approach when processing blood cultures that may contain one of the microorganisms reviewed in this article, including the use of additional media, media supplements, blind and terminal subcultures, or prolonged incubation and testing.

Rapid detection and identification of microorganisms from blood cultures

In an era characterized by increasing emphasis on minimizing laboratory costs, reliable and cost-effective methods for rapidly identifying bacteria and fungi directly from blood cultures have a great deal of appeal to clinical microbiologists. A variety of methods have been evaluated and found to be useful under certain conditions, although none of the methods has been standardized and questions remain as to whether their use improves patient care or reduces hospital costs. Even if these methods do not improve patient care or reduce hospital costs, their use and expense could be justified if they improve laboratory work flow or decrease laboratory costs or both. Several issues remain unresolved, one of which is whether the use of rapid identification methods with a continuous-monitoring blood culture system might allow for a clinically important decrease in the time required to identify blood culture isolates. Another issue is whether subsequent isolation by culture is necessary for microorganisms with predictable antimicrobial susceptibility patterns. These and other issues need to be studied further before the exact clinical usefulness of rapid methods will be known. At this time, no commercial product has been cleared or approved by the Food and Drug Administration (FDA) for the direct detection or identification of both of pathogenic microorganisms from blood culture bottles (Sharon Hansen, PhD, personal communication, 1993). Consequently, laboratory directors should exercise caution in the use of commercial or other products for direct blood culture testing, because manufacturers assume no liability for products that are used for purposes other than that for which they have been approved. In addition, such use of commercial products may be in violation of the rules set forth in the Clinical Laboratory Improvement Act of 1988. Furthermore, as discussed previously, the clinical performance characteristics of many products typically have not been determined, and, therefore, test reference ranges, sensitivity, specificity, and positive and negative predictive values have not been established. Other issues, such as the effect of different blood culture media and additives, also have not been studied adequately, nor are specific controls defined. Therefore, laboratory staff who would like to use commercial products to test blood cultures directly must themselves establish the performance characteristics of the product (keeping in mind the issue of liability) or, preferably, persuade manufacturers to sponsor large-scale controlled clinical trials both to establish performance characteristics and to obtain FDA clearance or approval for such usage of the product.(ABSTRACT TRUNCATED AT 400 WORDS)