Identification of clinical coagulase-negative staphylococci, isolated in microbiology laboratories, by matrix-assisted laser desorption/ionization-time of flight mass spectrometry and two automated systems

A study was performed to compare matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), linked to a recently engineered microbial identification database, and two rapid identification (ID) automated systems, BD Phoenix (Becton Dickinson Diagnostic Systems, France) and VITEK-2 (bioMérieux, Marcy L'Etoile, France), for the ID of coagulase-negative staphylococci (CoNS). Two hundred and thirty-four clinical isolates of CoNS representing 20 species were analyzed. All CoNS isolates were characterized by sodA gene sequencing, allowing interpretation of the ID results obtained using the respective database of each apparatus. Overall correct ID results were obtained in 93.2%, 75.6% and 75.2% of the cases with the MALDI-TOF-MS, Phoenix and VITEK-2 systems, respectively. Mis-ID and absence of results occurred in 1.7% and 5.1% of the cases with MALDI-TOF-MS, in 23.1% and 1.3% with the Phoenix, and in 13.7% and 0.9% with the VITEK-2 systems, respectively. In addition, with the latter automate, 10.3% of the IDs were proposed with remote possibility. When excluding the CoNS species not included in the databases of at least one of the three systems, the final percentage of correct results, Mis-ID and absence of ID were 97.4%, 1.3% and 1.3% with MALDI-TOF-MS, 79%, 21% and 0% with the Phoenix, and 78.6%, 10.3% and 0.9% with the VITEK-2 system, respectively. The present study demonstrates the robustness and high sensitivity of our microbial identification database used with MALDI-TOF-MS technology. This approach represents a powerful tool for the fast ID of clinical CoNS isolates.

Genetic environment of acquired bla(ACC-1) beta-lactamase gene in Enterobacteriaceae isolates

We studied the genetic organization of bla(ACC-1) in 14 isolates of Enterobacteriaceae from France, Tunisia, and Germany. In a common ancestor, ISEcp1 was likely involved in the mobilization of this gene from the Hafnia alvei chromosome to a plasmid. Other genetic events involving insertion sequences (particularly IS26), transposons (particularly Tn1696), or sulI-type integrons have occurred, leading to complex genetic environments.

Control of an ACC-1-producing Klebsiella pneumoniae outbreak in a physical medicine and rehabilitation unit

This article describes an outbreak of ACC-1-producing Klebsiella pneumoniae involving 40 patients. These were mainly men under 40 years old with a spinal cord injury, in a physical medicine and rehabilitation unit. The main risk factors were prolonged hospital stay, multiple-bed rooms, tracheostomy care and assisted defaecation. The outbreak was only controlled after the introduction of rigorous patient placement (i.e. single rooms or cohorting in the same room), while allowing the patients to have free access to the various technical services (e.g. physiotherapy and occupational therapy) and living spaces necessary for re-education.

Intérêt du dépistage actif des bactéries multirésistantes dans les services de médecine physique et réadaptation

OBJECTIVES

The objective of this study was to evaluate the epidemiology of antibiotic-resistant bacteria among motor impaired patients admitted to an acute rehabilitation unit.

METHODS

From January 2000 to December 2002, the acute rehabilitation units of R. Poincare Hospital have screened patients for methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase enterobacteria (ESBL-EB) carriage by nasal and rectal swab at admission, every month and exit.

RESULTS

Finally, MRSA was isolated form screening or diagnosis samples of 360 patients and ESBL-EB from screening or diagnosis samples of 170 patients, corresponding respectively to an incidence of 3.6 for 1000 days of hospitalization (DH) and 1.7 for 1000 DH. 66% (236/360) of MRSA carriers and 58% of ESBL-EB carriers were identified only by screening samples. Carriage origin was identified for year 2002: Cases were imported for 40% (26/65) of MRSA carriers and 43% (18/42) of ESBL-EB carriers. The median acquisition delays were of 31 days [3-154] for MRSA and 19 days [3-317] for ESBL-EB.

CONCLUSION

This allowed to set up contact precautions for more than 2 fold patients that would have allowed diagnosis samples alone.

Characterization of Class 1 integrons from Pseudomonas aeruginosa that contain the bla(VIM-2) carbapenem-hydrolyzing beta-lactamase gene and of two novel aminoglycoside resistance gene cassettes

Two clonally unrelated Pseudomonas aeruginosa clinical strains, RON-1 and RON-2, were isolated in 1997 and 1998 from patients hospitalized in a suburb of Paris, France. Both isolates expressed the class B carbapenem-hydrolyzing beta-lactamase VIM-2 previously identified in Marseilles in the French Riviera. In both isolates, the bla(VIM-2) cassette was part of a class 1 integron that also encoded aminoglycoside-modifying enzymes. In one case, two novel aminoglycoside resistance gene cassettes, aacA29a and aacA29b, were located at the 5' and 3' end of the bla(VIM-2) gene cassette, respectively. The aacA29a and aacA29b gene cassettes were fused upstream with a 101-bp part of the 5' end of the qacE cassette. The deduced amino acid sequence AAC(6')-29a protein shared 96% identity with AAC(6')-29b but only 34% identity with the aacA7-encoded AAC(6')-I1, the closest relative of the AAC(6')-I family enzymes. These aminoglycoside acetyltransferases had amino acid sequences much shorter (131 amino acids) than the other AAC(6')-I enzymes (144 to 153 amino acids). They conferred resistance to amikacin, isepamicin, kanamycin, and tobramycin but not to gentamicin, netilmicin, and sisomicin.

An SHV-derived extended-spectrum beta-lactamase in Pseudomonas aeruginosa

A clinical isolate of Pseudomonas aeruginosa RP-1 produced the extended-spectrum beta-lactamase (ESBL) SHV-2a. Its gene was expressed from a composite promoter made of the -35 region derived from the left inverted repeat of IS26 and the -10 region from the blaSHV-2a promoter itself. The DNA sequences immediately surrounding blaSHV-2a were homologous to plasmid pMPA2a from Klebsiella pneumoniae KpZU-3, while further away and 3' to the blaSHV-2a gene, a sequence corresponding to the left end of Tn1721 was detected, thus indicating a likely enterobacterial origin of this ESBL gene.

[Comparative activity of cefepime, ceftazidime and imipenem in a mouse infection caused by Klebsiella pneumoniae producing a broad spectrum beta-lactamase]

Mice experimentally infected with extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strains were injected twice daily for three days with ceftazidime, cefepime, or imipenem (25, 50, or 100 mg/kg/injection). Treatment efficacy was based on five-day survival and on the spleen viable bacteria count 16 hours after the last treatment dose. Under these experimental conditions, ceftazidime showed some activity on strains with low levels of resistance to ceftazidime. Cefepime used in a dose of 50 or 100 mg per injection demonstrated good activity but was slightly less effective than imipenem.

The first clinical isolate of Legionella parisiensis, from a liver transplant patient with pneumonia

A bluish white autofluorescent strain of Legionella was isolated from the tracheal aspirate of a female liver transplant patient who developed hospital-acquired pneumonia. This strain had biochemical characteristics compatible with those of L. cherrii, L. anisa, and L. parisiensis and could not be differentiated from L. bozemanii and L. parisiensis by the direct fluorescent-antibody assay. Phylogenetic analysis of partial 16S rRNA gene sequences of this strain (ATCC 700174) revealed the closest homology to the species L. parisiensis (99.5%). An L. parisiensis species-specific profile was also identified by a random amplified polymorphic DNA technique. This is the first report of L. parisiensis isolation from humans.

[Legionnaires' disease in the Paris area: epidemiology and mortality. Apropos of a series of 81 culture-positive cases]

OBJECTIVES

Evaluate etiological circumstances and prognosis in Legionnaires' disease.

METHODS

A series of 81 culture-proven cases of Legionnaires' disease was collected in the Paris area between 1989 and 1994.

RESULTS

Direct immunofluorescence assay was positive for Legionella pneumophilia in 48% of the cases. Serogroup 1 was isolated in 88% of the cases. The median age of the patients was 51 years and 74% were males. Infection was nosocomial in 28% of the cases. Immunosuppression was present in 45% of the patients (transplantation, cancer, leukemia). Among the immunosuppressed patients, 7 were HIV-infected. Mortality due to legionellosis reached 27%. This high mortality was probably related to patient selection criteria.

CONCLUSION

Mortality from Legionnaires' disease remains high as confirmed in this series.

Interaction of virulent and non-virulent Rhodococcus equi human isolates with phagocytes, fibroblast- and epithelial-derived cells

Rhodococcus equi is a facultative, intracellular, Gram-positive coccobacillus, increasingly reported in pneumonia of AIDS-infected patients. We investigated killing resistance properties of human R. equi virulent and avirulent human strains. Avirulent beta-lactam-susceptible strains had lower intracellular colony forming units after 45 min incubation in murine macrophages J774 and human monocyte-macrophage TPH-1 than those of virulent strains. Only virulent beta-lactam-resistant strains persisted within macrophages for at least 18 min only. A beta-lactam-resistant mutant was obtained from a beta-lactam-susceptible strain after selection in a penicillin G-containing culture medium. This mutant strain, like the natural virulent strains, persisted within macrophages, harboured cell-associated appendages, produced phage-like particles and induced, after its intravenous inoculation, a chronic infection in BALB/c nude mice. Supernatant culture of virulent strains transferred partial macrophage-killing resistance properties to avirulent strains. The same supernatant was toxic for L-929, HeLa and Vero cell cultures. These supernatant effects were heat-inactivated, trypsin-inactivated and did not seem to be linked to phage-like particle presence. These data argue that virulence, beta-lactam-resistance, and macrophage-killing resistance are associated in human R. equi isolates. Moreover, only virulent strains produced uncharacterized toxic factors.

Correlation between antibiotic resistance, phage-like particle presence, and virulence in Rhodococcus equi human isolates

Rhodococcus equi is a gram-positive coccobacillus that appears to be emerging as a pulmonary pathogen in AIDS patients. In four human clinical isolates, two antibiotic resistance phenotypes were found to coexist: one beta-lactam resistant and the other beta-lactam susceptible. In vitro, beta-lactam-resistant mutants were obtained at a frequency of 1 x 10(-5) to 5 x 10(-5) from beta-lactam-susceptible strains on cephalothin-containing plates. Neither beta-lactamase nor plasmid DNA was detected in beta-lactam-resistant or -susceptible strains. The penicillin-binding protein patterns for the two types of strains were identical. Electron microscopy revealed that the beta-lactam-resistant strains possessed cell-surface-associated appendages and produced phage-like particles. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total cell protein showed at least three additional bands of 42, 39, and 30 kDa found only in the beta-lactam-resistant strains. Testing for virulence in Swiss mice revealed that (i) phage-like-particle-producing strains had lower 50% lethal doses when injected intravenously in euthymic and nude mice than the non-phage-like-particle-producing strains did and (ii) intravenous inoculation of a sublethal dose (5 x 10(6) CFU) in nude mice led to chronic infection by the phage-like-particle-producing bacteria only. Finally, in vitro growth curves indicated that the phage-like-particle-producing strains possessed an ecological selection advantage. These results suggest that, among R. equi human isolates, the antibiotic resistance phenotype is associated with virulence and may be phage mediated.

Involvement of interferon-gamma and tumor necrosis factor-alpha in host defense against Rhodococcus equi

Rhodococcus equi is a facultative, intracellular, gram-positive coccobacillus increasingly reported as an opportunistic pathogen in AIDS patients. In vitro, splenic cells of noninfected euthymic mice produced tumor necrosis factor-alpha (TNF alpha) in greater amounts when incubated with live R. equi rather than with killed bacteria. In vivo, interferon-gamma (IFN-gamma) and TNF alpha serum levels of infected euthymic mice remained below the level of detectability. Treatment of infected nude mice, which developed chronic infection, with discontinuous injections of IFN-gamma, TNF alpha, or both did not decrease bacterial colony-forming units in liver, spleen, or lungs. However, treatment of infected euthymic mice, which cured a R. equi inoculum within 3 weeks, with anti-IFN-gamma or anti-TNF alpha antibodies (or both) significantly increased tissue colony counts. These data argue that, in this murine model, endogenous IFN-gamma and TNF alpha are involved in the cell-mediated immunologic response against R. equi infection.

Characterization of a novel extended-spectrum beta-lactamase from Pseudomonas aeruginosa

A clinical isolate of Pseudomonas aeruginosa RNL-1 showed resistance to extended-spectrum cephalosporins which was inhibited by clavulanic acid. Although this strain contained three plasmids ca. 80, 20, and 4 kb long, the resistance could not be transferred by mating-out assays with P. aeruginosa or Escherichia coli. Cloning of a 2.1-kb Sau3A fragment from P. aeruginosa RNL-1 into plasmid pACYC184 produced pPZ1, a recombinant plasmid that encodes a beta-lactamase. This beta-lactamase (PER-1) had a relative molecular mass of 29 kDa and a pI of 5.4 and was biosynthesized by P. aeruginosa RNL-1 along with a likely cephalosporinase with a pI of 8.7. PER-1 showed a broad substrate profile by hydrolyzing benzylpenicillin, amoxicillin, ticarcillin cephalothin, cefoperazone, cefuroxime, HR 221, ceftriaxone, ceftazidime, and (moderately) aztreonam but not oxacillin, imipenem, or cephamycins. Vmax values for extended-spectrum cephalosporins were uncommonly high, and the affinity of the enzyme for most compounds was relatively low (i.e., high Km). PER-1 activity was inhibited by clavulanic acid, sulbactam, imipenem, and cephamycins but not by EDTA. A 1.1-kb SnaBI fragment from pPZ1 failed to hybridize with plasmids that encode TEM-, SHV-, OXA-, or CARB/PSE-type beta-lactamase or with the ampC gene of P. aeruginosa. However, the same probe appeared to hybridize with chromosomal but not plasmid DNA from P. aeruginosa RNL-1. This study reports the properties of a novel extended-spectrum beta-lactamase in P. aeruginosa which may not be derived by point mutations from previously known enzymes of this species.

Role of T-lymphocyte subsets in Rhodococcus equi infection

Rhodococcus equi, a facultative intracellular gram-positive bacterium, can induce life-threatening infections in immunocompromised patients, especially those with AIDS. We have studied the mechanism of acquired immunity to this pathogen in a murine model. Protective immunity was induced by live but not killed bacteria. Adoptive transfer of resistance was obtained with spleen cells but not immune serum from mice immunized intravenously 30 days earlier with live bacteria. In normal mice, an intravenous challenge of 5 x 10(6) CFU of R. equi was cleared from the spleen, liver, and lungs within 3 weeks, whereas athymic nude mice were unable to clear the bacteria. In vivo depletion with monoclonal antibodies showed that both CD4+ and CD8+ T-cell subsets participate in the clearance of bacteria and that CD8+ T cells play the major role.

Therapy of Rhodococcus equi disseminated infections in nude mice

Rhodococcus equi is a facultative, intracellular, gram-positive coccobacillus increasingly reported as an opportunistic pathogen in human immunodeficiency virus-positive patients. However, the optimal drug regimen for treating R. equi pulmonary or systemic infections is not yet known. Therefore, a model of intravenously infected nude mice with disseminated infection was created to study the efficacy of antibiotics alone or in combination as determined by the reduction of bacterial CFU per gram in the lungs and spleen after 4 and 11 days of treatment. The studied antibiotics possessing low MICs against R. equi strains were amikacin, ciprofloxacin, erythromycin, imipenem, minocycline, rifampin, and vancomycin. Vancomycin, imipenem, and rifampin were the most effective agents in monotherapy. On the other hand, amikacin, ciprofloxacin, erythromycin, and minocycline alone were not active in this model. The most active drug combinations were those including vancomycin. No antibiotic-resistant mutants were selected in vivo with treatment involving any drugs used alone or in combination. Although the treatment recommended until now for R. equi infections is rifampin plus erythromycin, this study suggests that antibiotic combinations which include vancomycin may be the most effective in vivo.

In-vitro antimicrobial susceptibility of Rhodococcus equi

Rhodococcus equi is an intracellular facultative, Gram-positive cocco-bacillary organism of increasing importance as a pulmonary pathogen in HIV-positive patients. This study was carried out to evaluate the optimal antibiotic combinations for treating such infections. Four human R. equi isolates and one reference strain were tested for their susceptibilities to 36 antibiotics. In-vitro the most active antibiotics were amikacin, gentamicin, netilmicin, erythromycin, clarithromycin, roxithromycin, ciprofloxacin, sparfloxacin, rifampicin, vancomycin, teicoplanin, doxycycline, minocycline, imipenem, meropenem and trimethoprim/sulphamethoxazole. The only bactericidal antibiotics were the aminoglycosides, ciprofloxacin, sparfloxacin and vancomycin. As determined by FIC indices, four combinations were synergistic: rifampicin-erythromycin, rifampicin-minocycline, erythromycin-minocycline and imipenem-amikacin. However, no antibiotic combinations were synergistic with the time-kill kinetic method at achievable serum concentrations or at ten-fold and half-fold the MICs. Frequencies of selection of antibiotic-resistant mutants determined at concentrations of five- and ten-fold the MICs ranged from less than 1 x 10(-8) for erythromycin and trimethoprim/sulphamethoxazole to 5 x 10(-4) for amikacin. These results may be of help in selecting the antibiotics for treating infected HIV-positive patients.

[Detection of extended broad-spectrum beta-lactamases with the ATB MIC system]

The Enterobacteriaceae producing extended broad-spectrum beta-lactamases (ESB) must be detected even when their MIC to oxyiminocephalosporins are low. We tested 164 isolates (133 ESB, 31 non ESB) on two experimental ATB MIC plates containing cefotaxime or ceftazidime (0.06-128 mg/l) alone or associated with sulbactam (4 mg/l). Fifty four per cent of the ESB isolates are sensitive to cefotaxime, and 30% to ceftazidime. Respectively 95% and 94% of these bacteria have a synergism index (MIC CIII alone/MIC CIIII + sulbactam) greater than or equal to 4 with cefotaxime and ceftazidime. The isolates that do not produce ESB have all a rate less than 4. The ATB system can detect the extended broad spectrum beta-lactamases when low concentrations of cephalosporins are used, alone and in association with an inhibitor of beta-lactamases.

[In vitro activity of 4 fluoroquinolones against Klebsiella pneumoniae. Distribution according to phenotype resistance to aminoglycosides or beta-lactams]

Minimal inhibitory concentrations (MIC) of pefloxacin (PEF), norfloxacin (NOR), ofloxacin (OFL) and ciprofloxacin (CIP) are evaluated by agar dilution against 100 Klebsiella pneumoniae strains isolated in hospital. MIC 50 and 90%, micrograms/ml, are respectively: CIP (0.25/8), OFL (1/16), NOR (1/32), PEF (2/64). We determined the phenotypes PEF/NOR/OFL/CIP by taking into account the critic concentrations of the French Committee for Antibiogram. The results are: SSSS = 45%, RI/RI/RI/RI = 20%, RI/SSS = 19%, RI/RI/RI/S = 8%, RI/RI/SS = 7%. When a strain is resistant to pefloxacin alone, the MICs of the other fluoroquinolones are higher than those of the sensitive strains. The resistance to fluoroquinolones is most frequent in strains that have acquired resistance to aminoglycosides or betalactams, but exists also in strains that have no acquired resistance to these antibiotics.

Influence of different regions of the H-2 complex on the rate of clearance of Salmonella typhimurium

The rate of clearance of Salmonella typhimurium from the mouse spleen is under H-2 linked genetic control. The results of the present study, with H-2 recombinant mice on a C57BL/10 background, suggest the involvement of at least two loci, one in the D region and the other in the K-A alpha chromosomal segment.

[Broad spectrum beta-lactamases and the API ATB 244 system: the need for detection]

API ATB 24H is an automated system designed to test the sensitivity of bacteria to antibiotics. Using this system we found that it was not fully able to detect acquired resistance to oxy-iminocephalosporins in enterobacteriaceae producing extended broad spectrum betalactamase (CTX-1, SHV-3, SHV-4). However, the frequency of detection varied with the type of API SYSTEM (ATB G-, ATB PSE), the nature of beta lactam antibiotic (cefotaxime, ceftazidime) and the type of beta lactamase produced. Considering the fact that this new mechanism of resistance must be taken into account, we suggest that the most simple method for the detection of oxy-imini beta lactamases is a double disk test of synergy between Augmentin (acid clavulanic + amoxycillin) and 1 disk of oxy-iminocephalosporin.

[In vitro and in vivo activity of a combination of clavulanic acid and amoxicillin against Klebsiella pneumoniae producing extended broad-spectrum betalactamase (CTX-1, SHV-3, SHV-4)]

In vitro activity of an aminopenicillin (amoxicillin or ampicillin) combined with a betalactamase inhibitor (clavulanic acid or sulbactam, 2 mg/l) was examined against 39 strains of K. pneumoniae producing 3 types of extended broad spectrum betalactamases (CTX-1, SHV-3, SHV-4). Clavulanic acid produces the best synergistic effect. The in vivo activity of Augmentin (amoxicillin + clavulanic acid), 1 g once or twice a day, during 10 +/- 3 days was evaluated on 10 cases urinary tract infections in paraplegic patients. After 3 days, no leucocyturia was observed and bacteria were no more detected. The inhibitory effect of clavulanic acid for the extended broad-spectrum betalactamases shows that such an association could be probably chosen as well for treatment urinary infection.

Role of H-2 and non-H-2 genes in control of bacterial clearance from the spleen in Salmonella typhimurium-infected mice

The ability of mice to clear Salmonella typhimurium from their spleens in the late phase of infection was studied after inoculation with a temperature-sensitive mutant. Clearance of bacteria was delayed in C57BL/6 mice compared with BALB/c, C3H/HeJ, DBA/2, A/J, and CBA mice. The responses of F1 hybrids, backcrosses, and recombinant inbred strains derived from C57BL/6 and BALB/c (both Itys) and of H-2 congenic mice were analyzed. The results showed that the low rate of bacterial clearance was recessive, that the rate of clearance was under polygenic control, and that an H-2-linked gene(s) plays a major role. Among H-2 congenic mice with a C57BL/10 background, three phenotypes of bacterial clearance could be distinguished: high (H-2j, H-2q, and H-2u), intermediate (H-2d, H-2f, H-2k, H-2p, H-2r, H-2s, and H-2v), and low (H-2b) rates. The effect of the H-2 complex was apparent with different genetic backgrounds (Itys and Ityr). In recombinant inbred strains derived from C57BL/6 (Itys) and A/J (Ityr) mice, the effect of the H-2b haplotype on bacterial clearance appeared to be fully expressed only in strains carrying the Itys allele.

[Current status of aminoglycoside resistance in hospital Enterobacteriaceae]

We studied the susceptibility of Enterobacteriaceae to four aminoglycosides (gentamicin, tobramycin, netilmicin et amikacin). We determined their phenotypes of resistance by taking into account both the critic concentrations of the CFA (french committee for antibiogram) and the MIC of the main susceptible population of each species. The most frequent phenotypes were GTNt, TNtA and GTNtA. Amikacin resistance including phenotypes were essentially found in Klebsiella and Serratia (35% and 53% of the strains, respectively); with respect to amikacin, the phenotype expression may be insufficient to exceed the sensitive critic concentration of the CFA. Amikacin resistant strains were isolated from chronically infected patients with devices, such as urinary catheters or tracheal cannula. These results suggest a strains or plasmids outbreak.

Genetic control of Salmonella typhimurium-induced depression of delayed-type hypersensitivity to sheep erythrocytes in mice

Infection of mice with a temperature-sensitive mutant of Salmonella typhimurium C5TS allowed the survival of genetically susceptible mice. The ability to mount a delayed-type hypersensitivity (DTH) response to sheep erythrocytes during infection with C5TS was studied in various inbred mouse strains, recombinant inbred strains derived from C57BL/6 (susceptible) and A/J (resistant) mice, and C3H congenic mice. Suppression of the DTH response to sheep erythrocytes was found in mice that carried the Itys allele, the H-2b haplotype, or both. These genes are known to increase susceptibility to S. typhimurium infection. In contrast, no DTH response suppression was observed in mouse strains that carried other genes that increased susceptibility to S. typhimurium, e.g., DBA/2 and C3H/HeJ. Apart from a transient suppression in A/J mice, the DTH responses of resistant mice (A/J and CBA) were normal or increased. The DTH response to sheep erythrocytes could be restored in immunodepressed mice by increasing the immunizing dose, suggesting the possible role of activated macrophages in depression of the DTH response.

[Modulation by quinolones of the in vitro proliferative response of splenic cells of the mouse and IL 1 production]

Besides their antibacterial activity, antibiotics can modulate immune response. In this work, we studied the effects of 6 quinolones (nalidixic and pipemidic acid, pefloxacin, norfloxacin, ofloxacin, ciprofloxacin) on Con A or LPS induced mitogenic response in mice. Data presented here show that pefloxacin and ofloxacin enhanced Con A (1 microgram/ml) induced proliferative response when used at low concentrations (0.1 microgram/ml and 1 microgram/ml). In the same conditions LPS induced response was not modified. When used at high concentrations (greater than 25 micrograms/ml), inhibition of both LPS and Con A induced responses was observed. Con A induced response needs interaction between macrophages and T lymphocytes. So, we investigated whether quinolones could act on interleukin 1 (IL 1) production by macrophages. Our results showed that pefloxacin and ofloxacin, used at low concentrations, enhanced LPS induced IL 1 production by macrophages.

[In vitro sensitivity at 18 antibiotics of 192 strains of Pseudomonas aeruginosa isolated at Garches Hospital]

The in vitro activity of 18 antibiotic (beta-lactam agents, quinolones and aminoglycoside has been evaluated against 192 clinical isolates of Pseudomonas aeruginosa. Minimal inhibitor concentrations (MICs) were determined by the agar dilution technique. The 50% and 90% MICs were respectively: ticarcillin (32/greater than 1 024), azlocillin (16/512), piperacillin (8/512), cefsulodin (4/128), ceftazidime (2/8), aztreonam (4/16), imipenem (2/4), nalidixic acid (128/256), pefloxacin (1/8), norfloxacin (1/8), ofloxacin (2/8), ciprofloxacin (0.25/2), gentamicin (8/256), sisomicin (4/256), tobramycin (2/128) dibekacin (4/256), netilmicin (16/256), amikacin (8/16). The sensitivity to beta-lactam agents and to quinolones was usual. Resistance to aminoglycosides was frequently observed (59%): 35.7% of the resistant isolates were resistant to gentamicin-sisomicin-tobramycin-dibekacin-netilmicin, 30% to netilmicin alone, 17.8% to gentamicin-sisomicin-tobramycin-dibekacin-netilmicin-amikacin, 7% to gentamicin-netilmicin, 5.3% to gentamicin-sisomicin-tobramycin-dibekacin; we did not find any P. aeruginosa resistant only to gentamicin or gentamicin-sisomicin.

Impairment of lymphocyte proliferative responses and interleukin-2 production in susceptible (C57BL/6) mice infected with Salmonella typhimurium

C57BL/6 (susceptible) and A/J (resistant) mice were infected intravenously with a temperature-sensitive mutant of Salmonella typhimurium. In C57BL/6 mice a marked depression of the proliferative response of spleen cells to B and T mitogens occurred and was maximal at 2-3 weeks post-infection, whereas only minor changes were found in A/J mice. This immunodepression was mediated, at least in part, by adherent cells. Moreover, spleen cells from infected C57BL/6 mice did not produce interleukin-2 (IL-2) after concanavalin A stimulation. The impairment of IL-2 production was not related to a defect in IL-1 release. The addition of IL-2 to spleen cells did not restore their ability to respond to mitogens. The depression of mitogenic responses in infected C57BL/6 mice occurred at a time when increased resistance was present.

Host response to infection with a temperature-sensitive mutant of Salmonella typhimurium in a susceptible and a resistant strain of mice

The inoculation of a temperature-sensitive mutant of Salmonella typhimurium induced a long-lasting infection in susceptible (C57BL/6) and resistant (A/J) mice. During week 1 of infection, the number of bacteria in the spleens was similar in both mouse strains. Then, the decrease of bacteria was more rapid in the resistant strain. Splenomegaly and granulomatous hepatitis were more severe in the susceptible strain. The immune response induced by this infection was studied. In both mouse strains delayed-type hypersensitivity to Salmonella antigens was present, and resistance to reinfection with a virulent strain of S. typhimurium or with Listeria monocytogenes appeared with the same kinetics. Thus, it does not seem that the gene(s) controlling natural resistance to S. typhimurium act(s) on acquired immunity.

[Comparative in vitro antistaphylococcal effect of norfloxacin and pefloxacin on 312 hospital strains]

Antistaphylococcal activity of two new quinolones, norfloxacin and pefloxacin, was studied. Minimal inhibitory concentrations (MICs) were determined by the agar dilution technique for 312 staphylococcal strains, all of which were resistant to nalidixic acid. 50% and 90% MICs were respectively 1 and 4 micrograms/ml for norfloxacin and 0.5 and 1 micrograms/ml for pefloxacin. Activities of these two new quinolones proved similar on Staphylococcus aureus and non-coagulase-producing staphylococci, regardless of their response to methicillin. Cross resistance between the two drugs was demonstrated.

[Enterobacter cloacae and E. aerogenes septicemia: emergence of resistant variants (derepressed cephalosporinase) during treatment with third-generation cephalosporins]

From three patients hospitalised in intensive care units with Enterobacter septicaemia (two cases with E. cloacae, and one with E. aerogenes), cefotaxime therapy, alone or in combination with an aminoglycoside, selected variants (R) with increased resistance to beta-lactam antibiotics. The cross-resistance extended to all the beta-lactam antibiotics tested, penicillins and cephalosporins, including third-generation cephalosporins. The crude extracts of uninduced cultures of R variants showed high beta-lactamase activity and of the cephalosporinase type. These variants were selected in vitro with a frequency of 10(-6) to 10(-7) and may result from a mutation involving the regulation of Enterobacter cephalosporinases, usually inducible. Data from the literature indicated that this new type of resistance is actually emerging and observed not only in Enterobacter sp. The problem of emergence of R variants exhibiting cross-resistance to beta-lactam antibiotics should be considered when third-generation cephalosporins are used.

Production and characterization of monoclonal antibodies against rat brush border antigens of the proximal convoluted tubule

In order to understand further the processes involved in immunological injury of the kidney, we have prepared monoclonal antibodies against brush border (BB) antigens of rat proximal tubule. The 27 antibodies which constitute the basis of this report have been cloned, characterized immunochemically, and classified in three specificity groups on the basis of tissue reactivity. The first group is made up of six antibodies reacting with antigens simultaneously present on BB and glomerulus: three are directed against a high molecular weight (MW) protein which migrates with an apparent MW of 330,000; two react with a 90,000 MW protein that is present diffusely on renal and intestinal BB as well as on endothelial cells; one recognizes an antigen exclusively present on superficial tubules and glomerular epithelial cells, which could not be chemically characterized. The second group is made up of eight antibodies present on renal and intestinal BB: five react with a 120,000 MW antigen, one with a 300,000 MW antigen. The third group comprises 13 antibodies. Two are directed against antigens present within the cytoplasm or the basolateral membranes of renal tubules. Eleven react with intracellular antigens probably related to the cytoskeleton. Since they have been identified through several fusions, some of the monoclonal antibodies described are probably directed against immunodominant proteins of the BB. They open new possibilities for purifying the corresponding antigens by affinity chromatography as well as for obtaining BB preparations selectively depleted of the strongest immunogens thus favouring antibody production to previously unrecognized antigens.

[Non-gonococcal urethritis and cervicitis. Isolation of Chlamydia trachomatis and detection of anti-Chlamydia antibodies by indirect immunofluorescence]

The responsibility of Chlamydia trachomatis in non-gonococcal urethritis and cervicitis was investigated in 267 patients of both sexes. It was confirmed in 36.3% of patients with urethritis and 20.9% of patients with cervicitis by isolating C. trachomatis on Hela 229 cells in the presence of cytochalasin B. No clinical feature specific of C. trachomatis infection could be elicited. The patients were tested for total IgM-type serum anti-chlamydia antibodies by indirect immunofluorescence (IF), using as antigen the inclusions formed in Hela 229 cells by an L2 serotype of C. trachomatis. The serological study was also performed in 86 blood-donors used as controls. The diagnostic value of IF serology is limited in lower genito-urinary infections; the presence of specific IgM's correlates well with the isolation of C. trachomatis, but these IgM's are not detected in protracted urethritis or cervicitis. In such cases, the aetiological diagnosis can only be made by isolation of C. trachomatis from the focus of infection.

[Isolation of Chlamydia trachomatis on Hela 229 cells treated with cytochalasin B in 330 cases of lower genital infections in men and women]

A technique of isolating Chlamydia trachomatis on Hela 229 cells treated with cytochalasine B after the inoculation is described. By this technique, Chlamydia trachomatis was isolated from 36,6% of 186 men with non-gonococcal urethritis and from 20,8% of 114 women with signs of cervicitis.