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A total of 1,116 clinically isolated strains belonging to Staphylococcus aureus (200), Staphylococcus epidermidis (200), Streptococcus pneumoniae (20), Escherchia coli (200), Klebsiella spp. (177), Serratia marcescens (22), Pseudomonas aeruginosa (224), Haemophilus influenzae (35) and Salmonella (38) from the Department of Infectious Diseases, La Sapienza University in Rome (Italy) were tested against three fluoroquinolones (ofloxacin, ciprofloxacin and levofloxacin) and 10 other antibiotics (augmentin, ampicillin, cefaclor, cefixime, cefotaxime, cotrimoxazole, gentamicin, minocycline, oxacillin and vancomycin). Fluoroquinolones inhibited essentially about 100% of H. influenzae, Salmonella and S. pneumoniae, more than 75% of Staphylococcus including methicillin-resistant strains, and about 90% of Enterobacteriaceae and 50% of P. aeruginosa. Minimal inhibitory concentration values ranged from0.015 to32 micrograms/ml for Klebsiella, S. aureus and epidermidis, E. coli and P. aeruginosa; from0.015 to 2 micrograms/ml for Salmonella; from 0.03 to 16 micrograms/ml for Serratia; from0.015 to 1 microgram/ml for Haemophilus; and from 0.5 to 2 micrograms/ml for S. pneumoniae. Levofloxacin and to a lesser extent ofloxacin and ciprofloxacin, generally exhibited a greater activity than the other agents against both Gram-positive and Gram-negative bacteria. Regarding the distribution of resistant strains in Italy, we found a peculiar pattern of resistance as far as E. coli and P. aeruginosa were concerned. Quality control parameters are also summarized. S. epidermidis resulted as a new emergent pathogen especially in immunocompromised patients and its level of sensitivity has been modified over the last few years. In fact, the percentage of resistant strains to antibiotics or the percentage of methicillin-resistant isolates (in our study 35%), has gradually increased. Levofloxacin and ofloxacin showed good activity against staphylococcal strains compared with the majority of other antibiotics. These results suggest that the newer quinolones are promising antimicrobial agents for various infections.

To evaluate the incidence of bacterial colonization in the throat and in urines of children admitted to a paediatric ward in the year 1994. To test the sensitivity of isolates on the most common antibiotics used in therapy.The investigation was carried out on a group of 270 children (125 male and 145 female), aged between 3 months and 12 years, hospitalized with feverish infectious pathology in the department of infectious and Tropical Diseases of the University "La Sapienza" of Rome. The cultures of the throat swabs and on urines were performed on the admission of the children before the beginning of the therapy.The throat-swab cultures showed pathogenous microrganisms in 232 samples (85.9%) with a slight prevalence of Gram-negative bacteria (122) with respect to Gram-positive (110) and saprophytic microbial flora (38). The urine cultures proved to be positive in 81 cases (30%) with a prevalence of Gram-negative (56) above Gram-positive isolates (25).The two/thirds of paediatric patients hospitalized in an Infectious Diseases Department appeared to be colonized in the upper respiratory tract, whereas in about 10% of them a marked bacteriuria was clearly evident, often in the absence of specific symptoms. A few isolates either from the throat or from urines, showed resistance to the common antibacterial agents.

Forty-four Mycobacterium-spp. were isolated in 33 patients from an infectious diseases ward. All patients were HIV-positive and most of them were drug-abusers. M. avium-intracellulare was the most common type of MOTT (Mycobacteria other than tuberculosis) detected and the only microorganism isolated in patients with mycobacteriaemia. The radiometric method performed by the Bactec system enhanced the isolation rate of mycobacteria, especially from the bloodstream. The Gen-probe DNA hybridization system proved to be rapid diagnostic tool for the identification of strains.

The in vitro antibacterial activity of zidovudine alone and in combination with ciprofloxacin was investigated. Zidovudine showed a good activity against Escherichia coli and Salmonella (MIC range 0.5-8 micrograms/ml and 1.5-62 micrograms/ml respectively) isolated from biological samples of HIV-infected patients. These strains proved to be extremely susceptible to ciprofloxacin alone. The interaction between zidovudine and ciprofloxacin ranged from additive activity to indifference. No antagonism was observed: the FIC index for every combination resultedor = 1.5. The addition of AZT 1 mg/l (clinically achievable plasma concentration after therapeutic doses of 1200 mg/day) did not affect the bactericidal activity of ciprofloxacin; on the contrary, in some cases we observed an increase of bactericidal effect of the quinolone. These data have to be considered in patients with AIDS who can be treated concomitantly with zidovudine and ciprofloxacin.

The authors have compared the antimicrobial resistance patterns and plasmid profiles of Gram-negative isolates in an intensive care unit over a 7-month period in order to identify epidemiologically related isolates. Bacterial plasmids were found to be valuable markers for the comparison of strains of nosocomial Gram-negative bacilli. Thirty-nine mechanically ventilated patients in an ICU were included. From bronchoaspiratus, the authors isolated 58 strains of Gram-negative bacilli (24 Ps. aeruginosa and 34 Enterobacteria). Common plasmids were found in most Enterobacteria. The interspecies plasmid exchange suggests that interstate spread of these strains may have occurred. Twenty-six Enterobacteria carried plasmids, 11 of which proved transmissible. The R-factors were transferred to other genera that were isolated in the hospital, thereby adding to the pool of multiresistant nosocomial isolates. Larger plasmids transferred ampicillin and carbenicillin resistance, while gentamycin and cephalotin resistance was carried by smaller plasmids. Only 4 Ps. aeruginosa carried plasmids, one of which was transmissible. Pseudomonas plasmid DNA is extracted with difficulty by the simple lysis method, due to the roughness of the colonies. All Pseudomonas isolates belonged to the same biotype which can be regarded as an epidemiological marker. Therefore, plasmid profiling is a useful tool for epidemiological surveillance of Enterobacteria and is a good method for determining the relatedness of isolates in a nosocomial environment.

HIV infection is thought to exacerbate the virulence of normal saprophytic vaginal microflora. We studied the vaginal ecosystem of HIV patients to detect the quantitative and qualitative variation of vaginal microorganisms. 15 patients (5 with AIDS and 10 with ARC) were investigated. Vaginal candidiasis was more frequent in this group than in the control groups. Gardnerella was present in 60% of patients generally in association with anaerobic bacteria and Mycoplasma. Among anaerobia, Bacteroides sp and other Gram-negative rods were the most common bacteria. Neisseria gonorrhoeae was absent in all patients tested. Chlamydia trachomatis was recovered in two out of the 15 HIV-positive patients. Aerobic Gram-negative flora was 100-fold that of the control group and anaerobic Gram-negative flora 10-fold.

Clavulanic acid was tested for in vitro synergistic activity with Ampicillin and Amoxycillin against 41 Gram-negative strains beta-lactamase positive or negative. Clavulanic acid provides progressive inhibition of the beta-lactamases of many bacteria. The better protective effect of CA on AM or AMX is at concentration of 100 mcg. Some synergy was seen against E. coli, Klebsiella and Proteus. Enterobacter and Pseudomonas remained resistant to the combination of AMX and AM with clavulanic acid. We have seen no synergistic effect when non beta-lactamase producing organisms were tested. Although CA alone has a broad antibacterial spectrum, the degree of activity is generally rather poor.

In this work, the sensitivity in vitro of cefoxitin, cefuroxime, cefotaxime, cefoperazone and cephalothin have been examined. Test of sensitivity in vitro have been performed as by Kirby-Bauer method as by measurement of MIC and MBC. Then the regression lines have been determined. Cefotaxime and cefoperazone provided nearly complete coverage of all Enterobacteriaceae; 80% were inhibited at less than or equal to 2 mcg./ml. This value is far below therapeutically attainable serum concentrations. Cefotaxime has MIC lower than cefoperazone. It has a significant spectrum of activity against Pseudomonas aeruginosa, nonenterococcal Streptococcus sp, non Enterobacteriaceae Gram-negative bacilli. Only enterococci and Acinetobacter species were relatively resistant to cefoperazone and cefotaxime. The cephalothin and the cefoxitin included excellent antimicrobial coverage of the staphylococci and the anaerobic bacteria respectively.

An A-protein positive strain of Staphylococcus aureus was grown in varying concentrations of erythromycin, clindamycin and miocamycin at sub-MIC levels and incubated in purified human polymorphonuclear leukocytes (PMNs). The presence of A-protein produced resistance of the above strain to phagocytosis and killing by PMNs and a slight resistance to opsonization by normal serum. The addition of antibiotics, which inhibit protein biosynthesis, caused significant changes in the ability of this bacterium to resist opsonization by serum complement. The antimicrobial agents produced a significant enhancement of bacterial killing and phagocytosis. In particular, clindamycin and erythromycin, at sub-MIC concentrations, modified the hair-like structure of S. aureus, which contains A-protein, and were able to affect the interaction of the strain with phagocytic cells.

We present the results of sensitivity of 191 Gram-negative bacteria towards the following antibiotics: aminoglycosides (amikacin, gentamicin, tobramycin, netilmicin), cephalosporines (moxalactam, cefotaxime, ceftazidime) and piperacilline obtained by agar diffusion method (Kirby-Bauer) versus automatic system MS 2 Abbott. Essential accord expressed in percentage is for amikacin 96%, for gentamicin 93%, for moxalactam 91%, for tobramycin 95%, for cefotaxime 92%, for piperacilline 89%, for netilmicin 90%, for ceftazidime 92. Full accord gives more discrepant results especially for cephalosporins. For aminoglycosides no significative differences were observed between the two methods. For cephalosporins the incidence of discordance was a little more high. A better sensitivity was obtained by Kirby-Bauer method versus automatic system, which can be considered a therapeutical tool as it furnishes rapidly (4 hours) MIC values, useful to establish antibiotic doses.

HR 756 is a new beta-lactamase resistant cephalosporin. The activity of HR 756 was compared in vitro to that of cefamandole, cefoxitine, cefuroxime and cephalothin. A concentration of 1 microgram/ml inhibited practically all isolates of E. coli, Salmonella, Shigella, Proteus indole + and indole --, Klebsiella, etc. A lower activity in vitro has been found regarding to Enterobacter, Serratia, Citrobacter and Pasteurella. The cefotaxime has some anti-Pseudomonas activity at concentrations of 7.5-15 micrograms/ml. For most Gram-negative organisms, HR 756 was most active. The cephalothin and the cefoxitine have resulted more active regard to Staph. aureus and Bacteroides fragilis, respectively.

The 4-Quinolones are known to induce the SOS response. This should also be the case with AZT (Zidovudine) which has the same bactericidal mechanism. SOS response might make the bacteria more sensitive or more resistant to subsequent doses of quinolones and AZT. NA (Nalidixic acid), the first quinolone of the early 1960s, sensitises a strain of E. coli isolated from the urine of patients with cystopyelitis and the E. coli AB1157 wild type strain which is a well-known SOS inducer. In this case, the SOS system is not involved but only the recombination repair mechanisms which make the bacteria more susceptible to further damage by NA. On the contrary, CPX (Ciprofloxacin) protects E. coli from further exposure to antibiotics. Therefore the SOS response induction assists the bacteria in recovering from the DNA damage caused by CPX. The SOS response induced by AZT in the tested E. coli strains does not seem to either contribute to the lethality of the drug or to be involved in protecting bacteria from the damage caused by AZT. In fact, the percentage of killing was the same for both pre-treated and non pre-treated bacteria (p = 0.5). On the contrary, it was found that in Salmonella typhimurium belonging to blood of a patient with recurrent bacteriaemia, the CPX added to pre-treated bacteria with AZT was less lethal than when it was added to non pre-treated bacteria. The SOS response, in this case, protects bacteria from the damage caused by AZT.

A comparative study of the in vitro activity of norfloxacin was performed versus that of aminoglycosides, pipemidic acid, tetracycline and chloramphenicol. These antibiotics are the most commonly used antimicrobial agents in the treatment of enteric and urinary tract infections. Results obtained with norfloxacin against Gram-negative isolates tested were very encouraging. MIC values for the Enterobacteriaceae were less than or equal to 0.47 mcg/ml, and for Pseudomonas and Acinetobacter less than or equal to 32.5 mcg/ml. The activity of norfloxacin against Pseudomonas was inferior to that of amikacin, but superior to that of gentamicin. In association with aminoglycosides, norfloxacin proved to be most useful in the treatment of urinary tract infections, while norfloxacin associated with tetracycline and chloramphenicol did not give satisfactory results in the treatment of enteric infections.