David F. Welch

A Newly Recognized Fastidious Gram-Negative Pathogen as a Cause of Fever and Bacteremia

BACKGROUND We identified a motile, curved, gram-negative bacillus as the cause of persistent fever and bacteremia in two patients with symptomatic human immunodeficiency virus infection. The same organism was subsequently recovered from a bone marrow-transplant recipient with septicemia and from two immunocompetent persons with week-long febrile illnesses. All the patients recovered after antimicrobial therapy. METHODS AND RESULTS Primary cultures of blood processed by centrifugation after blood-cell lysis yielded adherent, white, iridescent, morphologically heterogeneous colonies in 5 to 15 days. Subcultures grew in four days on chocolate, charcoal-yeast extract, or blood agar. The organisms stained weakly with safranin and were not acid-fast. Fluorescent-antibody tests for legionella and francisella were negative. Biochemical reactivity was minimal and difficult to ascertain. Agar-dilution testing revealed in vitro susceptibility to most antimicrobial agents tested. The cellular fatty acid composition of the isolates was similar, resembling that of Rochalimaea quintana or brucella species, but not Helicobacter pylori or species of campylobacter or legionella. As resolved by gel electrophoresis, cell-membrane preparations of all isolates contained similar proteins, with patterns that differed from that of R. quintana. Patterns of digestion of DNA from all isolates by EcoRV restriction endonuclease were virtually identical and also differed from that of R. quintana. On immunodiffusion, serum from one convalescent patient produced a line of identity with sonicates of all five isolates. CONCLUSIONS This pathogen may have been unidentified until now because of its slow growth, broad susceptibility to antimicrobial agents, and possible requirement of blood-cell lysis for recovery in culture. It should be sought as a cause of unexplained fever, especially in persons with defective cell-mediated immunity.

Experimental Infection of Young Specific Pathogen-Free Cats with Bartonella henselae

Eighteen 12-week-old specific pathogen-free cats, blood culture- and serum antibody-negative for Bartonella henselae, were randomly allocated to groups and were intravenously inoculated with 10(10) (group 1), 10(8) (group 2), or 10(6) (group 3) B. henselae or with saline (group 4) or were not inoculated (group 5). Cats were humanely killed at 2, 4, 8, 16, and 32 weeks after inoculation. All B. henselae-inoculated cats were bacteremic by 2 weeks after infection. Bacteremia persisted until 32 weeks after infection in 1 cat. Cats in groups 1 and 2 had fever (>39.7 degrees C) and partial anorexia by 2 weeks after infection that lasted 2-7 days. All infected cats had Bartonella-specific IgM and IgG serum antibodies and lymphocyte blastogenic responses. Histopathologic lesions were observed in multiple organs of infected cats through 8 weeks after infection. Cats were readily infected with B. henselae by intravenous inoculation, developed histopathologic lesions that apparently resolved, and developed B and T lymphocyte responses to infection.

Evidence of reproductive failure and lack of perinatal transmission of Bartonella henselae in experimentally, infected cats

Five female specific pathogen-free (SPF) cats inoculated intradermally with B. henselae and bacteremic for 4 weeks, and one cat inoculated with 0.9% NaCl, were bred with uninfected SPF male cats. The uninfected female became pregnant with one breeding, while three infected cats became pregnant 1-12 weeks later, after repeated breedings. Two infected females either did not become pregnant or maintain pregnancies despite repeated breedings. Infected cats produced anti-B. henselae IgM and IgG antibodies. Fetuses and kittens of infected cats were not infected and did not produce anti-B. henselae antibodies. Male cats bred with infected females did not become infected or seroconvert. Maternal anti-B. henselae IgG antibodies detected in sera of kittens 2 weeks post-partum were no longer detectable 10 weeks post-partum. These findings suggest that B. henselae causes reproductive failure in female cats, but is not transmitted transplacentally, in colostrum or milk, or venereally. Infected cats immunosuppressed with methylprednisolone acetate after their kittens were weaned had no detectable bacteria in tissues, suggesting that they were no longer infected.

Role of Rapid Immunochromatographic Antigen Testing in Diagnosis of Influenza A Virus 2009 H1N1 Infection

ABSTRACT Rapid antigen testing using immunochromatographic devices has become a diagnostic mainstay for detection of influenza virus and respiratory syncytial virus, the two major viruses infecting the respiratory tract. Recent studies have indicated that poor performance in the detection of the novel influenza A virus 2009 H1N1 should preclude their use. A survey of influenza diagnostic methods available on ClinMicroNet and Division C, the two ASM list servers, revealed that, despite this reported poor performance, a majority of the laboratories surveyed intend to continue to offer this testing during the current influenza season. Our two experts have been asked to consider the following question: what is the role of rapid immunochromatographic antigen testing in the laboratory diagnosis of influenza A virus infection during the current 2009 H1N1 pandemic?

Activities of various beta-lactams and aminoglycosides, alone and in combination, against isolates of Pseudomonas aeruginosa from patients with cystic fibrosis.

The inhibitory and bactericidal activities of carbenicillin, ticarcillin, moxalactam, cefoperazone, azlocillin, piperacillin, ceftazidime, and three aminoglycosides, alone and in various combinations, were determined against 60 isolates of Pseudomonas aeruginosa from the sputum of patients with cystic fibrosis. Ceftazidime was the most active beta-lactam, with minimum inhibitory and bactericidal concentrations for 90% of isolates of 4 micrograms/ml. Moxalactam was the least active of the new beta-lactams, with activity equivalent to that of carbenicillin; each had a minimum inhibitory concentration for 90% of isolates of 64 micrograms/ml and a minimum bactericidal concentration for 90% of isolates of 128 microgram/ml. All combinations of an aminoglycoside plus a beta-lactam showed favorable inhibitory effects. Combinations of beta-lactams showed mostly addition or indifference. Although little antagonism was seen with combinations of beta-lactams or with aminoglycoside-beta-lactam combinations, no consistent advantage of beta-lactam combinations was demonstrated in vitro. These results suggest several single drugs and combinations that merit clinical evaluation in cystic fibrosis patients with Pseudomonas pulmonary infections.

Point-Counterpoint: The role of rapid immunochromatographic antigen testing in the diagnosis of influenza A 2009 H1N1.

ABSTRACT Rapid antigen testing using immunochromatographic devices has become a diagnostic mainstay for detection of influenza virus and respiratory syncytial virus, the two major viruses infecting the respiratory tract. Recent studies have indicated that poor performance in the detection of the novel influenza A virus 2009 H1N1 should preclude their use. A survey of influenza diagnostic methods available on ClinMicroNet and Division C, the two ASM list servers, revealed that, despite this reported poor performance, a majority of the laboratories surveyed intend to continue to offer this testing during the current influenza season. Our two experts have been asked to consider the following question: what is the role of rapid immunochromatographic antigen testing in the laboratory diagnosis of influenza A virus infection during the current 2009 H1N1 pandemic?

Susceptibility of group A beta-hemolytic Streptococcus isolates to penicillin and erythromycin.

We have reevaluated the antibiotic susceptibilities of group A beta-hemolytic streptococci in view of recent reports of a high prevalence of erythromycin resistance in Japan and of an increase in penicillin treatment failures in the United States. A total of 474 isolates recovered during a 2- to 3-month period in 1980 were tested. All were susceptible by microtiter broth dilution to a penicillin concentration of less than or equal to 0.03 micrograms/ml (minimal inhibitory concentration), and 473 were killed by less than or equal to 0.06 micrograms/ml (minimal inhibitory concentration). Erythromycin minimal inhibitory concentrations showed a bimodal distribution: 95% were less than or equal to 0.06 micrograms/ml, and 5% were greater than or equal to 1 microgram/ml. Of the minimal bactericidal concentrations, 21% were greater than or equal to 1 microgram/ml and 3% were greater than or equal to 16 micrograms/ml. Group A beta-hemolytic streptococci remain susceptible to the inhibitory and bactericidal actions of penicillin, thus providing no in vitro explanation for the bacteriological relapses reported in some clinical studies. Unlike the Japanese experience, only 5% of our isolates were resistant to erythromycin (minimal inhibitory concentration, greater than or equal to 1 microgram/ml); however, 22% were tolerant (ratio of minimal inhibitory/bactericidal concentrations, greater than or equal to 32).

Immune response of neonatal specific pathogen-free cats to experimental infection with Bartonella henselae

The purpose of this study was to determine whether neonatal cats develop and maintain a persistent bacteremia for longer than do adult cats with a normal mature immune system, and whether neonatal cats are susceptible to infection with Bartonella henselae by oral inoculation. Neonatal specific pathogen-free (SPF) cats were inoculated with B. henselae intradermally (n = 4) or orally (n = 5) or with 0.9% NaCl (n = 2). Blood was collected periodically through 16 weeks post-inoculation (PI) for serology, bacteriology and complete blood count. Cats inoculated orally or intradermally at 3-5 days of age were bacteremic through 12-16 weeks PI, similar to what is documented for adult cats inoculated intradermally or intravenously. One cat inoculated at age 2 weeks was bacteremic through 10 weeks PI; the other was not bacteremic. Intradermally inoculated neonatal cats produced serum IgG antibodies to B. henselae but orally inoculated neonatal cats did not. Infected cats with and without serum IgG antibodies to B. henselae became blood-culture negative simultaneously, suggesting that IgG is not required to clear bacteremia.

In vitro antibacterial activities of antibiotics against Pseudomonas aeruginosa in peritoneal dialysis fluid.

Intraperitoneal antibiotics are used to treat Pseudomonas aeruginosa peritonitis, a serious complication of continuous ambulatory peritoneal dialysis. However, P. aeruginosa killing is often inefficient despite low MBCs. Broth dilution MIC/MBC and time kill curves of tobramycin, amikacin, netilmicin, azlocillin, piperacillin, ceftazidime, cefsulodin, and ciprofloxacin were determined in peritoneal dialysis fluid (PDF), buffered PDF, fluid recovered from patients on continuous ambulatory peritoneal dialysis (RPF), and cation-supplemented Mueller-Hinton broth. MBCs of all antibiotics were 8 to 16 times greater in PDF and RPF than in Mueller-Hinton broth or buffered PDF. Use of the time kill curve technique and Mueller-Hinton broth showed that aminoglycosides killed greater than or equal to 99.9% of P. aeruginosa at 1 h, ciprofloxacin killed greater than or equal to 99.9% at 2 h, and beta-lactams killed greater than or equal to 99.9% at 6 h. In contrast, killing was not demonstrated in PDF by any drug at 6 h and by aminoglycosides only at 24 h. Bactericidal activity was optimal in RPF for ciprofloxacin at 1 h and for aminoglycosides at 2 h; bactericidal activity was not demonstrated in RPF with any beta-lactam (no kill by penicillins; less than 99% kill by cephalosporins). Slow bacterial growth, increased protein binding, and glucose concentrations and other inhibitors may interfere with beta-lactam activity in RPF. These considerations and reported clinical failures and toxicity of aminoglycoside therapy warrant further study of quinolones and drug combinations in P. aeruginosa peritonitis.

In vitro antimicrobial activity of aztreonam alone and in combination against bacterial isolates from pediatric patients.

We examined 134 pediatric clinical isolates of Enterobacteriaceae, Pseudomonas aeruginosa, and gram-positive cocci for susceptibility to aztreonam alone and in combination with seven other antibiotics. All 98 gram-negative isolates were susceptible to aztreonam with similar inhibitory and bactericidal activity. Combinations of aztreonam with cefoxitin, ampicillin, or clindamycin were generally indifferent or additive. Synergism was occasionally seen against enteric organisms with aztreonam plus cefoxitin or clindamycin. Combinations of tobramycin and aztreonam were synergistic (62%) against P. aeruginosa; aztreonam plus piperacillin or ticarcillin was additive. Aztreonam did not affect the activity of nafcillin against Staphylococcus aureus, or of ampicillin against species of Streptococcus group B or D. Antagonism was seen only with aztreonam plus cefoxitin against Enterobacter species, but not at clinically significant concentrations. Several combinations of antibiotics with aztreonam should be appropriate for initial therapy of infections in children without major risks of antibacterial antagonism.