Microbial etiology of acute pneumonia in hospitalized patients.

The purpose of this study was to determine the microbial etiology of pneumonia by using strict criteria among a group of hospitalized patients. Patients with acute community-acquired or hospital-acquired pneumonia were studied in a systematic and comprehensive manner for bacterial, viral, chlamydial, mycobacterial, and fungal pathogens. A total of 198 patients with 204 episodes of pneumonia were evaluated. Despite 100 percent follow-up of all surviving patients, a specific etiologic agent could be found in only 103 episodes. Among 154 episodes of community-acquired pneumonia, a diagnosis was made in 79; the most common pathogen was from the genus Legionella, followed by various Gram-negative enteric bacteria, Gram-positive cocci, influenza A virus, and Mycoplasma pneumoniae. The etiologic agent was found in 24 of the 50 patients with hospital-acquired pneumonia; no pathogen predominated. We conclude that even when elaborate diagnostic studies are done, including many invasive procedures, the etiology can be determined in only about half of the patients with acute pneumonia. The pathogens of pneumonia in this study are not markedly different between community-acquired and hospital-acquired infection.

Influenza type A virus infection of suckling mice pre-exposed to insecticide carrier.

Suckling CD-1 outbred mice exposed topically to insecticide carrier (IC), a mixture of emulsifiers and solvent, were rendered less sensitive to infection with lethal doses of influenza type A/PR8/34 (H0N1) virus than untreated and mock-treated control mice. Decreased sensitivity to influenza type A/PR8/34 virus infection was evidenced by a significant increase in the mean percent survival of the mice. In addition, a 10- to 100-fold reduction in the 50% lethal titer of the stock virus was observed in IC-treated mice relative to untreated mice. Decreased sensitivity was virus dose related and occurred within a dose range of 2 to 8 X LD50. No decrease in mortality rate was observed as a function of exposure to IC.

Electron microscopic observations concerning the in vivo uptake and release of the agent of guinea-pig inclusion conjunctivitis (Chlamydia psittaci) in guinea-pig exocervix.

This report details electron-microscopical observations concerning C. psittaci infection in vivo. The model employed was that of the guinea-pig infected at the exocervical region with the agent of guinea-pig inclusion conjunctivitis (GPIC). Our observations indicate that chlamydial particles gain access to their target cells by the mechanism of endocytosis. Single GPIC elementary bodies were seen to be positioned within individual endosomes. The observations reported here provide evidence that chlamydial particles that had undergone their developmental cycle within the exocervical epithelial cells may leave the epithelium in 2 ways; within entire infected cells that had been shed into the lumen of the cervix and by means of the liberation of chlamydial particles from disrupted cells. The mechanism of cell disruption and shedding is thought to involve the large number of PMNs observed to be present within the enlarged intercellular spaces of the infected epithelium.

Plaque formation by mumps virus and inhibition by antiserum.

Boston and ABC strains of mumps virus produced plaques approximately 1.0 mm in diameter in monolayers of BGM cells. The plaques were circular and either clear or target-like in form. Ricki strain virus produced plaques of similar size and form but, in addition, a red plaque was observed with this agent. The vaccine strain of mumps virus, Jeryl Lynn, produced minute clear plaques approximately 0.3 mm in diameter. Incorporation of diethylaminoethyl (DEAE)-dextran into the overlay medium did not affect the size difference between Jeryl Lynn plaques and those of the other strains. However plaques of the Jeryl Lynn and Ricki strains were more easily visualized when the overlay medium contained 400 mug/ml of DEAE-dextran. Simultaneous titration by plaque formation and roller tube infectivity showed that these two methods were of equal sensitivity. Virus neutralization by antibody was demonstrated by plaque reduction. Rise in antibody titer was observed in sera from human and animal infection, human vaccination, and rabbit immunization.

Inactivation of herpes simplex virus by concanavalin A.

The infectivity of herpes simplex virus type 1 (HSV-1) was inactivated after treatment with either concanavalin A (ConA) or periodate. Phytohemagglutinin, wheat germ agglutinin, pokeweed mitogen, and neuraminidase failed to inactivate the virus. The effect of ConA could be specifically inhibited or reversed by the addition of alpha-methyl-d-glucoside or alpha-methyl-d-mannoside. Evidence was obtained that HSV-1 inactivated by ConA could adsorb to host cells. Viral aggregation was not a major mechanism in the inactivation of HSV-1 by ConA. Under the experimental conditions employed, inactivation of HSV-1 was faster by ConA than by antiserum and less temperature dependent. A ConA-resistant fraction was detected which appeared to adsorb less quickly than untreated virus, and penetration of ConA-resistant fraction was strikingly slow. The presence of aggregates in the virus preparation did not appear to account for the ConA-resistant fraction. Inactivation of viral infectivity by ConA was obtained only with enveloped viruses, since HSV-1, HSV-2, pseudorabies, and vesicular stomatitis virus were inactivated and vaccinia and echovirus type 6 were not.

Surface antigens produced by Herpesviruses Varicella-Zoster virus.

Surface antigen(s) was demonstrated by the mixed agglutination technique on cell cultures infected with varicella-zoster virus (V-Z). The reactions appeared to be specific for V-Z, and no cross-reaction was obtained with herpes simplex virus (HSV). V-Z surface antigen had similar physicochemical properties to that of HSV. It was stable to heating at 56 C and treatment with 1% Formalin, 2,4-dinitrophenol, and periodate, whereas it was undetectable after exposure to acetone or ethanol. Antibodies detecting surface antigen were present in high titer in sera from varicella or herpes zoster patients and paralleled titers obtained by the complement fixation test.

Humoral immune response in acquired immunity to chlamydial genital infection of female guinea pigs.

Immunity to reinfection in the genital tract of female guinea pigs with the agent of guinea pig inclusion conjunctivitis was found to be dependent upon an intact humoral immune response. Cell-mediated immunity in the absence of humoral immunity had no apparent role in resistance to challenge infection.

Effect of antithymocyte serum on the course of chlamydial genital infection in female guinea pigs.

The treatment of female guinea pigs, infected in the genital tract with the chlamydial agent of guinea pig inclusion conjunctivitis, with rabbit anti-guinea pig thymocyte serum extended the course of the infection by 20 to 30 days. The rabbit anti-guinea pig thymocyte serum was shown to suppress delayed hypersensitivity responses to the guinea pig inclusion conjunctivitis agent and the contact allergen oxazolone. The appearance of antibody in genital secretions was delayed, but the infection persisted at low levels even when normal serum and secretory antibody titers were attained, indicating that cell-mediated immunity may play a role in the resolution of chlamydial genital infections.

Specific effect of estradiol on the genital mucosal antibody response in chlamydial ocular and genital infections.

Estradiol treatment of female guinea pigs was found to alter the course of genital, but not ocular, infection with the chlamydial agent of guinea pig inclusion conjunctivitis. Immunoglobulin G (IgG) and IgA responses in genital secretions of genitally infected animals were delayed by estradiol treatment, but neither response in the eye resulting from either ocular or genital infection was affected. However, the appearance of IgG in the genital tract after ocular infection was markedly inhibited in estradiol-treated guinea pigs.

Enhancement by phytohaemagglutinin of inactivation of herpes simplex virus by concanavalin A.

Inactivation of herpes simplex virus (HSV) by concanavalin A (Con A) was enhanced by treatment with phytohaemagglutinin (PHA)-P using a two-stage reaction procedure. Treatment with PHA alone failed to inactivate HSV. Enhancement of inactivation was also effective when HSV was exposed to PHA first. Our results suggest that the envelope of HSV contains receptor sites for Con A which are important in the infectious process, as well as receptor sites for PHA which are not critical for infectivity. Direct interaction of Con A with PHA was demonstrated and the reaction was reversed by alpha-methyl-D-glucoside. The data indicate that PHA stabilized the binding of Con A to the virus since reversal of inactivation by alpha-methyl-D-glucoside was minimal following treatment with Con A and PHA. Con A inactivated only enveloped virions and enhancement by PHA was a general phenomenon.

Humoral immunity in the resolution of genital infection in female guinea pigs infected with the agent of guinea pig inclusion conjunctivitis.

Female guinea pigs infected in the genital tract with the chlamydial agent of guinea pig inclusion conjunctivitis were selectively immunosuppressed by varying regimens of cyclophosphamide (Cy) treatment. Temporary suppression of both humoral and cell-mediated immunity by daily treatment of Cy (25 mg/kg) for 13 days resulted in a prolonged infection, whereas daily treatment for the duration of the experiment totally prevented the development of humoral and cell-mediated responses and produced an intense and prolonged infection which did not resolve. When humoral immunity alone was suppressed by treatment with Cy (250 and 150 mg/kg) at 9-day intervals, the infection again did not resolve. Treatment with 100 mg of Cy per kg at 9-day intervals resulted in an extended infection which resolved concomitantly with the development of antibody to guinea pig inclusion conjunctivitis. These data indicate that humoral immunity is essential for the recovery of female guinea pigs from guinea pig inclusion conjunctivitis genital infection. A market weight loss was observed which could not be attributed to Cy treatment alone. Edematous and ulcerative changes of the external genitalia were also noted.

Experimental genital infection of male guinea pigs with the agent of guinea pig inclusion conjunctivitis and transmission to females.

Male guinea pigs were inoculated intraurethrally with the agent of guinea pig inclusion conjunctivitis (Gp-ic). Cytoplasmic inclusions were found in superficial epithelial cells of the urethra in smears and stained sections. Gp-ic antigen(s) was detected by immunofluorescent staining of sections. There was no marked urethral exudate, but many animals developed bullous lesions on the glans and the body of the penis and a severe inflammatory lesion of the hind leg. All males demonstrated an antibody response and most of them showed a positive skin test reaction. Venereal transmission to females of Gp-ic infection was shown to occur as determined by detection of inclusions in vaginal smears, antibody response, and positive skin tests.

Infection of genital tract and transmission of ocular infection to newborns by the agent of guinea pig inclusion conjunctivitis.

Female guinea pigs were inoculated intravaginally with the agent of guinea pig inclusion conjunctivitis (Gp-ic). Evidence for infection was obtained by demonstration of Gp-ic inclusions in epithelial cells of genital tract smears, histopathology, recovery of Gp-ic during infection, and antibody response. Infection of the genital tract was produced with low doses (20-200 median egg lethal doses) of the agent. The infection lasted about 3 weeks, and there was no marked clinical response. Ocular infection that could be detected as early as 3 days after birth in offspring of infected mothers was also demonstrated.

Immune response in mice infected in the genital tract with mouse pneumonitis agent (Chlamydia trachomatis biovar).

Female Swiss-Webster mice were inoculated intravaginally with mouse pneumonitis agent (MoPn), a Chlamydia trachomatis biovar. Inoculation with 3.5 X 10(5) egg lethal doses per mouse resulted in shedding of the agent from the genital tract for as long as 21 days. Immunoglobulin M antibodies to MoPn were detected in plasma by day 7 post-inoculation, and immunoglobulin G antibodies were detected by day 14. Antibodies were detected in genital secretions by day 20, and titers in plasma and secretions were still considerable on day 56. Delayed-type hypersensitivity tests, determined by footpad swelling, were not positive in appreciable numbers of animals until after day 25. Delayed-type hypersensitivity reactions were maximal 24 h after testing and were preceded by an Arthus-like reaction, which appeared within 3 h and declined by 12 h. Convalescent animals were rechallenged by intravaginal inoculation and were found to be solidly immune.