Katherine Sprunt

Evidence Suggesting Importance of Role of Interbacterial Inhibition in Maintaining Balance of Normal Flora

Abstract Evidence presented in support of the hypothesis that interrelationships among organisms in the pharynx provide one of the mechanisms that maintain the bacterial status quo. Many organisms ...

Abnormal colonization of neonates in an intensive care unit: means of identifying neonates at risk of infection.

Summary: The current investigation was designed to select infants in the neonatal intensive care unit (ICU) at highest risk of infection. The data, derived from a prospective study of 223 neonates, indicate that neonates in an ICU develop their initial aerobic pharyngeal flora according to one of the three patterns shown in Table 1, one of which (low titer or no growth) is dependent on antibiotic therapy. Of particular importance is the finding that infants with normal flora (a-streptococci predominating) or cultures showing low titers (<104 colony-forming units (cfu)/ml) or no growth did not become infected. All infections occurred in the group of infants with abnormal pharyngeal colonization (18 infections in 115 abnormally colonized infants): with a single exception the infecting organism showed the cultural characteristics of the colonizing organism. Consequently one can pinpoint the relatively small number of infants at particular risk of infection and predict what the infecting organism will be if infection occurs.Speculation: These findings indicate indirectly that normal bacterial flora provides a significant host defense mechanism against infection. It seems reasonable that artificial development of “normal” flora by implantation of key constituents (e.g., α-streptococci) in the pharynx should increase the resistance of abnormally colonized high risk infants to infection.

Production of poliomyelitis virus with combined antigenic characteristics of type I and type II

Abstract Evidence is presented indicating that a “combined” poliomyelitis particle which can be neutralized by type I as well as by type II antiserum has been produced in tissue cultures after simultaneous infection of monkey kidney cells with type I and type II poliomyelitis viruses. Serial passage of the “combined particles” suggests that they are capable of reproducing as such but are not stable.

Infectious Ribonucleic Acid Derived from Enteroviruses.

Summary 1) RNA-containing fractions have been prepared from crude tissue culture virus suspensions of 6 varieties of enterovirus by the method of Gierer and Schramm. Each RNA preparation has produced plaques on human cell monolayers. The plaque-forming agent is completely inactivated by RNAase but not by DNAase. RNA is, therefore, an essential component for the infectivity of the preparation. 2) The plaques formed by RNA fraction contain intact virus from which RNA is prepared. The RNA directs the cell to replicate not only the specific RNA but also a new highly specific protein needed for synthesis of intact original virus.

Sensitivity of populations of clonal lines of HeLa cells to polioviruses.

Summary Propagation of HeLa cell populations from single clones isolated by the Puck technic provides cells which are more stable in growth potential and virus sensitivity than “farm” populations from which they were selected. Populations from 6 clones have been studied; 4 were of predominant cell type by microscopic examination (clones 1, 2, 3 and 6) and 2 differed from the predominant type (clones 4 and 5). Clone 5 was the most sensitive and clone 4 the most resistant to types 1 and 2 polio viruses. Although clone 5, as a generalization, maintained its characteristic morphology and sensitivity to poliovirus for 2 years, it was not possible to correlate morphology with sensitivity to the polioviruses. Selection and propagation of this most susceptible of the 6 clonal populations isolated provided a stable tool for studies of polioviruses. Since line 5 maintained its greater sensitivity for at least 2 years, a heritable factor (or factors) is probably responsible for the greater sensitivity.

Haemophilus influenzae Susceptibility Testing Within Four Hours by a Modification of the Autobac I System

By adding an XV strip to the eugonic broth or substituting Levinthal broth, the standard Autobac I susceptibility testing system may be used to determine susceptibility of Haemophilus influenzae to antimicrobial agents. Complete concordance was attained in testing 30 strains (5 resistant) by Autobac I, disk diffusion, and broth dilution methods. Autobac I results were available within 4 h after isolation of the organism.

Reaction of infectious RNA with mammalian cells. I. Attachment to cells.

Summary Infectious polio virus RNA enters mammalian cells in tissue culture in a 2-step process: 1) “attachment” which is independent of time, temperature, osmolarity, pH or other factors in the ranges known to influence infectivity of RNA, and 2) “uptake” which is markedly influenced by these factors. An average of 75% of plaque producing RNA units exposed to cells in monolayers becomes attached to them in less than 1 minute.

Factors Influencing the Infectivity of Poliovirus Ribonucleic Acid.

Summary Evidence presented shows that the influence of salt concentration of the environment on RNA infectivity for mammalian cells is due at least in part to alteration of the state of susceptibility of the host cell. The 3 different cell lines tested simultaneously responded differently when exposed to the same RNA preparation diluted in varying salt concentrations. Other factors which alter host cell susceptibility, sucrose concentration, age of host cell, nutritional environment of host cell and temperature during the adsorption interval, emphasize the importance of the physiological state of the cell at time of exposure to RNA to the degree of infectivity expressed.

PHARYNGEAL IMPLANTATION OF ALPHA HEMOLYTIC STREPTOCOCCI (STREP) IN NEONATES IN AN ICU

Pharyngeal implantation of a carefully selected strain of α-strep (#215) was attempted in 14 neonates with high titer abnormal colonization of the pharynx with potential pathogens (e.g., conforms, pseudomonads, staphylocccci) to convert the flora to “normal” (m-strep predominant). Serial semi-quantitative culture samples from 346 neonates in an ICU showed strong positive correlation between high titer abnormal colonization of the pharynx and infection. To date, no demonstrable systemic infection occurred in those infants with “normal” pharyngeal flora. All but one of the 14 infants received a single dose, approxinately 106 colony forming units (CFU), of strain 215. The youngest was 8 and the oldest 64 days old when given the strain. The pharyngeal flora of 10 of the infants became “normal” within 2-3 days. In 5, implantation is considered responsible for the change because only the implant type was recovered initially. In the other 5 infants a low (4% or less) to moderate (5-15%) proportion of their strep initially resembled the implant. The strain was not recovered from 4 infants. Included in the 4 is the first infant given the strain who received too low an inoculum (102-204 CFU). Another was given cholamphenicol within 24 hrs of the implant. The data show 1) Implantation can be carried cut in high titer abnormally colonized infants 2) “Normal” flora is attained in 2-3 days 3) The implant strain can be identified in mixed strep populations 4) No adverse effect of the implant strain has been noted.

750 DISCREPANCY BETWEEN MINIMUM INHIBITORY CONCENTRATION (MIC) AND MINIMUM BACTERICIDAL CONCENTRATION (MBC) OF PENICILLIN DEMONSTRATED IN GROUP A (GAS) AND GROUP B |[beta]|- HEMOLYTIC STREPTOCOCCI (GBS)

A discrepancy between the MIC and the MBC of penicillin (pen) against GBS has been reported, suggesting that the relapses of GBS disease after treatment with conventional doses of pen may be a result of this discrepancy. In this study, we measured pen MIC and MBC levels against GBS and compared them with levels obtained for GAS, an organism that has been successfully treated for years with conventional doses of pen without evidence of relapse in normal hosts. These experiments confirmed the reports that a large MIC/MBC discrepancy exists in GBS(10 fold); however, a larger discrepancy exists for GAS(25 fold). These findings diminish the likelihood of clinical significance of the MIC/MBC ratio alone in accounting for the relative difficulty in treating GBS. Other factors, such as the lower absolute sensitivity of GBS to pen compared to that of GAS, must be playing a role: both the MIC and the MBC values were significantly higher for GBS than for GAS.