Ampicillin-sensitive Strains Research Articles

2803. The Medical Trends and Economic Burden of XDR Typhoid Compared to Non-XDR Typhoid: A Single Center Retrospective Study from Karachi, Pakistan

Abstract Background In 2016, Pakistan reported the first outbreak of an Extensively Drug Resistant (XDR) typhoid showing susceptibility only to Meropenem and Azithromycin which created a treatment dilemma and raised concerns not only in developing countries but also globally. In this study, we compared the medical trends and economic burden of XDR typhoid with non-XDR typhoid at a tertiary care hospital of Karachi, Pakistan. Methods A retrospective study was conducted at the Sindh Infectious Diseases Hospital & Research Centre Karachi, Pakistan from June 2022 to April 2023. All hospitalized patients 14 years and above with confirmed Salmonella typhi on blood culture were included. Medical records were reviewed for clinical data and antibiotic cost. Statistical analysis was done using SPSS. Results Thirty-five patients were included of which 23 (65.7%) had XDR typhoid while 12 (34.3%) patients had non-XDR typhoid. Of the 12 non-XDR typhoid cases, nine were MDR (Multi Drug Resistant) while three had ampicillin sensitive strain. The mean age was 21.14 years with 27 (77.1%) males. Compared to non-XDR, majority of the XDR typhoid patients had diarrhea (60.9% vs. 16.7%, p-value= 0.02, OR 7.7, 95% CI: 1.3-44.0). XDR typhoid was treated with either Meropenem alone or Meropenem and Azithromycin combination while MDR typhoid was treated with Ceftriaxone. The time to defervescence was prolonged in XDR typhoid compared to non-XDR typhoid (7.95 days vs. 4.67 days, p-value= 0.007, OR 1.6, 95% CI: 1.14-2.3), with higher per day cost of antibiotics and total inpatient-antibiotic cost (US$20.3 vs. US$11, p-value= 0.006, OR 1.4, 95%CI 1.1-1.9) and (US$193 vs. US$139, p-value= 0.048] respectively. Within XDR group, the mean defervescence time was more in patients who received combined Meropenem and Azithromycin compared to Meropenem alone group (10.1 days vs 6.4 days, p-value=< 0.001) with a consequent higher per day in-patient antibiotic cost (USD$22 vs USD$ 18.8, p-value= < 0.001) and total in-patient cost (USD$ 235 vs. USD$ 158K, p-value= 0.009). Conclusion XDR typhoid has emerged not only as a heath care but also as an economic challenge owing to its prolonged defervescence time and increased per day/ total in-patient antibiotic cost. Disclosures All Authors: No reported disclosures

Ampicillin-controlled glucose metabolism manipulates the transition from tolerance to resistance in bacteria

The mechanism(s) of how bacteria acquire tolerance and then resistance to antibiotics remains poorly understood. Here, we show that glucose abundance decreases progressively as ampicillin-sensitive strains acquire resistance to ampicillin. The mechanism involves that ampicillin initiates this event via targeting pts promoter and pyruvate dehydrogenase (PDH) to promote glucose transport and inhibit glycolysis, respectively. Thus, glucose fluxes into pentose phosphate pathway to generate reactive oxygen species (ROS) causing genetic mutations. Meanwhile, PDH activity is gradually restored due to the competitive binding of accumulated pyruvate and ampicillin, which lowers glucose level, and activates cyclic adenosine monophosphate (cAMP)/cAMP receptor protein (CRP) complex. cAMP/CRP negatively regulates glucose transport and ROS but enhances DNA repair, leading to ampicillin resistance. Glucose and Mn2+ delay the acquisition, providing an effective approach to control the resistance. The same effect is also determined in the intracellular pathogen Edwardsiella tarda. Thus, glucose metabolism represents a promising target to stop/delay the transition of tolerance to resistance.

Real-time monitoring of extracellular ATP in bacterial cultures using thermostable luciferase.

Adenosine triphosphate (ATP) is one of the most important indicators of cell viability. Extracellular ATP (eATP) is commonly detected in cultures of both eukaryotic and prokaryotic cells but is not the focus of current scientific research. Although ATP release has traditionally been considered to mainly occur as a consequence of cell destruction, current evidence indicates that ATP leakage also occurs during the growth phase of diverse bacterial species and may play an important role in bacterial physiology. ATP can be conveniently measured with high sensitivity in luciferase-based bioluminescence assays. However, wild-type luciferases suffer from low stability, which limit their use. Here we demonstrate that an engineered, thermostable luciferase is suitable for real-time monitoring of ATP release by bacteria, both in broth culture and on agar surfaces. Different bacterial species show distinct patterns of eATP accumulation and decline. Real-time monitoring of eATP allows for the estimation of viable cell number by relating luminescence onset time to initial cell concentration. Furthermore, the method is able to rapidly detect the effect of antibiotics on bacterial cultures as Ampicillin sensitive strains challenged with beta lactam antibiotics showed strongly increased accumulation of eATP even in the absence of growth, as determined by optical density. Patterns of eATP determined by real-time luminescence measurement could be used to infer the minimal inhibitory concentration of Ampicillin. Compared to conventional antibiotic susceptibility testing, the method presented here is faster and more sensitive, which is essential for better treatment outcomes and reducing the risk of inducing antibiotic resistance. Real-time eATP bioluminescence assays are suitable for different cell types, either prokaryotic or eukaryotic, thus, permitting their application in diverse fields of research. It can be used for example in the study of the role of eATP in physiology and pathophysiology, for monitoring microbial contamination or for antimicrobial susceptibility testing in clinical diagnostics.

Detection of beta-lactamase-negative ampicillin resistance in Haemophilus influenzae in Belgium

Haemophilus influenzae, a frequent colonizer of the respiratory tract, is the causative agent of several clinically important infections. In cases that require therapeutic intervention, laboratory susceptibility testing can detect beta-lactam antibiotic resistance and guide the best treatment course. In the absence of a beta-lactamase, beta-lactam resistance may be due to an altered form of the PBP3 protein, encoded by the ftsI gene. While these so-called beta-lactamase-negative ampicillin-resistant (BLNAR) strains are of serious clinical interest, identification in the clinical laboratory is not always straightforward. In the current study, the ftsI genes of a set of phenotypic BLNAR H. influenzae isolates taken from samples collected in the UZ Brussel hospital in Belgium were sequenced and re-tested at the National Reference Laboratory (NRC). Non-silent mutations in the ftsI gene were found in 100% of the isolates. Although 30% of the isolates were classified by the NRC as beta-lactamase-negative ampicillin-sensitive (BLNAS) strains based on the EUCAST guidelines on ampicillin minimal inhibitory concentration (MIC), all isolates showed MIC values ≥1 mg/L. These relatively high MIC values indicate a decreased susceptibility to ampicillin, and suggest that sequencing of the ftsI gene should be used as part of an antibiotic susceptibility testing (AST) algorithm in the clinical laboratory. This would allow clinicians to make better informed decisions regarding patient treatment.

Expression and Extracellular Secretion of Endo-glucanase and Xylanase by Zymomonas mobilis.

Recombinant Zymomonas mobilis (pGEX-4T-3 BI 120-2) was constructed to encode endo-glucanase (CelA) and endo-xylanase (Xyn11) from Z. mobilis ZM4 (ATCC 31821) and an uncultured bacterium. The recombinant was genetically engineered with the N-terminus of a predicted SecB-dependent (type II) secretion signal from phoC of Z. mobilis to translocate the enzymes extracellularly. Both the enzymes were characterized regarding their functional optimum pH and temperature, with the highest multi-enzyme activities at pH6.0 and a temperature of 30°C, which approximates the optimum conditions for ethanol production by Z. mobilis. The crude intracellular and extracellular fractions of the recombinant were characterized in terms of substrate specificity using carboxymethyl cellulose (CMC), beechwood xylan, filter paper, Avicel, and pretreated rice straw. The crude extracellular and intracellular enzymes with cellulolytic and xylanolytic activities were more robustly produced and secreted from the recombinant strain compared to the wild-type and ampicillin-sensitive strains, using CMC and beechwood xylan as the substrates. Ethanol production by the recombinant strain was greater than the production by the wild-type strain when pretreated rice straw was used as a sole carbon source.

Clinical Characteristics of Haemophilus influenzae at General Hospital in the Central Region of Japan

Haemophilus influenzae is an important pathogen that caused several infection diseases, such as sinusitis, otitis media, sepsis, and meningitis. This study was conducted to find out the prevalence and antimicrobial susceptibility pattern of Haemophilus influenzae isolates at general hospital in the central region of Japan from December 2015 to January 2016. Haemophilus influenzae was identified by standard laboratory procedure. Antimicrobial susceptibility testing was performed by micro dilution assay according to CLSI recommendation. One hundred ninety-one Haemophilus influenzae were isolated, among which 95 (49.7%) were from male and 96 (50.3%) were from female. The age incidence of (0) years, (≤2) years, (≤5) years, and (6≤) years groups were 22(11.5%), 92(48.2%), 61(31.9%), and 16(8.4%), respectively. Positive samples were received mostly from the nasal discharge (177/92.7%), sputum (6/3.1%), tonsillar (6/3.1%), and pharynx (2/1.0%). Ceftriaxone was the most active antibiotics with 100% susceptible rates, followed by ciprofloxacin (99.5%) and minocycline (99%) in our study. Furthermore, we categorized four patterns: beta lactamase-negative ampicillin-sensitive strain (BLNAS), beta lactamase-negative ampicillin-re- sistant strain (BLNAR), beta lactamase-positive ampicillin resistant strain (BLPAR), and beta lactamase-positive amoxicillin-clavulanic acid-resistant strain (BLPACR) from those ampicillin susceptible results. The numbers of female were significant greater than those of male in BLPAR (p = 0.0336). With respect to antimicrobial susceptible pattern, there was no minocycline and piperacillin resistant strain in both BLNAS and BLNAR (p

Safety and technological characterization of Staphylococcus equorum isolates from jeotgal, a Korean high-salt-fermented seafood, for starter development

To select starters for jeotgal, a traditional Korean high-salt-fermented seafood, the safety and technological properties of its predominant bacteria isolates, which were identified as Staphylococcus equorum, were assessed. Among the 185 S. equorum isolates from jeotgal, 126 ampicillin-sensitive strains were subjected to assessments for antibiotic susceptibility and safety hazards. Sixty-six out of the 126 S. equorum strains exhibited phenotypic resistances to at least one antibiotic, and their prevailing resistances were to penicillin G (34.1%), erythromycin (9.5%) and trimethoprim (9.5%). Twenty-four S. equorum strains expressed resistance to at least two antibiotics. The lnuA for lincomycin (four strains) and pbp for β-lactam (three strains) were amplified by PCR. α-Hemolytic activity was not detected from the 126 strains, and 87 strains presented δ-hemolytic activity. Among the 87 strains, three strains exhibited β-hemolytic activity. Thirty-seven strains formed a biofilm. A hemolysin gene homologous to that of Staphylococcus epidermidis was amplified from an S. equorum strain with β-hemolytic activity by PCR; however, no PCR product homologous to the previously known staphylococcal enterotoxin genes was amplified. Thirty-nine S. equorum strains cleared all of the tested safety hazards and were adopted for technological property assessments. Among these strains, 16 strains exhibited protease, lipase and nitrate reductase activities, and seven strains did not produce four types of biogenic amines. Five biogenic amine non-producers exhibited three enzyme activities. Most of the strains could grow on the agar with 20% NaCl, and 13 strains maintained growth at the 25% NaCl condition. S. equorum KS1039, which is the most applicable strain that covers the safety and technological requirements for jeotgal, can grow at the 25% NaCl condition. Through this research study, we reconfirmed the necessity of characterization in the functionality and safety of S. equorum for starter development because all of the tested phenotypic characteristics were expressed in strain-specific manners.

Aqueous Two-Phase System-Derived Biofilms for Bacterial Interaction Studies

We describe patterning of bacterial biofilms using polymer-based aqueous two-phase system (ATPS) microprinting protocols. The fully aqueous but selectively bacteria-partitioning nature of the ATPS allows spatially distinct localization of suspensions of bacteria such as Pseudomonas aeruginosa and Escherichia coli with high precision. The ATPS patterned bacterial suspensions form spatially distinct biofilms over time. Due to the fully aqueous and gentle noncontact printing procedures employed, coculture biofilms composed of multiple types of bacteria could be printed not only adjacent to each other but also directly over another layer of existing biofilm. In addition, the ATPS environment also allows free diffusion of small molecules between spatially distinct and localized bacterial suspensions and biofilms. This enables biofilms to chemically affect or be affected by neighboring biofilms or planktonic cells, even if they consist of different strains or species. We show that a β-lactamase producing biofilm confers ampicillin resistance to neighboring nonresistant planktonic cells, as seen by a 3,600-fold increase in survival of the ampicillin-sensitive strain. These examples demonstrate the ability of ATPS-based biofilm patterning methods to enable unique studies on commensalistic effects between bacterial species.

The action of ampicillin on Aerobacter (Klebsiella) aerogenes.

Abstract The action of ampicillin (α-aminobenzylpenicillin) on Aerobacter (Klebsiella) aerogenes (NCTC 418, Bact. aerogenes no. 240) has been investigated. Enzymatic destruction of the drug, although a necessary prelude to the growth of the sensitive strain, does not precede growth of resistant strains at concentrations to which they have been “conditioned”. Instead a gradual inactivation occurs throughout the growth cycle. It is concluded that other factors are also involved in resistance. Cloxacillin, which was not destroyed by the cells, had little action on the ampicillin-sensitive strain and did not induce any ampicillin-destroying activity. The results are discussed in terms of the modes of action of penicillins and the origin of the resistance is examined.

Antimicrobial Resistance in Haemophilus influenzae Respiratory Tract Isolates in Korea: Results of a Nationwide Acute Respiratory Infections Surveillance

Antimicrobial susceptibility patterns and beta-lactam resistance mechanisms of 544 Haemophilus influenzae isolates through the nationwide Acute Respiratory Infections Surveillance (ARIS) network in Korea during 2005 and 2006 were determined. Resistance to ampicillin was 58.5%, followed by resistance to cefuroxime (23.3%), clarithromycin (18.7%), cefaclor (17.0%), amoxicillin-clavulanate (10.4%), and chloramphenicol (8.1%). Levofloxacin and cefotaxime were the most active agents tested in this study. beta-Lactamase production (52.4%) was the main mechanism of ampicillin resistance, affecting 96.1% of TEM-1-type beta-lactamase. According to their beta-lactam resistance mechanisms, all isolates were classified into the following groups: beta-lactamase-negative, ampicillin-sensitive (BLNAS) strains (n = 224; 41.5%); beta-lactamase-positive, ampicillin-resistant (BLPAR) strains (n = 255; 47.2%); beta-lactamase-negative, ampicillin-resistant (BLNAR) strains (n = 33; 6.1%); and beta-lactamase-positive, amoxicillin-clavulanate-resistant (BLPACR) strains (n = 28; 5.2%). Among the BLNAR and BLPACR strains, there were various patterns of multiple-amino-acid substitutions in penicillin-binding protein 3. Particularly, among BLNAR, group III isolates, which had three simultaneous substitutions (Met377Ile, Ser385Thr, and Leu389Phe), were identified for the first time in Korea. Three group III strains displayed the highest MIC of cefotaxime (1 to 2 mug/ml). The results indicate the importance of monitoring a changing situation pertaining to the increase and spread of BLNAR and BLPACR strains of H. influenzae for appropriate antibiotic therapy for patients with respiratory tract infections in Korea.

喀痰より分離されたβ-ラクタム系薬耐性インフルエンザ菌の起炎性に関する臨床的検討

Haemophlus influenzae persists in the respiratory tract and sometimes causes respiratory tract infections. To evaluate the pathogenesis of beta-lactam-resistant Haemophilus influenzae, we classified 193 Haemophilus influenzae strains isolated from sputum of patients with respiratory tract disease in 24 beta-lactamase positive (BLP) strains, 65 beta-lactamase negative ampicillin resistant (BLNAR) strains and 104 beta-lactamase negative ampicillin sensitive (BLNAS) strains and reviewed the pathogenesis of the strains. The pathogenesis of the strains was evaluated as definite pathogen, presumptive pathogen, colonization and contamination. It was judged to be the definite pathogen that many bacteria isolated from high quality sputum of the patients with respiratory tract infections. Presumptive pathogen was considered to be the bacteria provided from the patient with respiratory infections when the quality of the sputum or quantity of bacteria did not satisfy superscription basis. We considered the bacteria to be colonization or contamination isolated from patients without infections. The breakdown of definite pathogen/presumptive pathogen/colonization/contamination in each by groups was BLP (8/4/8/4), BLNAR (26/14/15/10), BLNAS (36/20/31/17). The ratio of definite or presumptive pathogen was 50% in BLP, 62% in BLNAR and 54% in BLNAS and the significant difference was not recognized in these. Pathogenesis of beta-lactam-resistant Haemophilus influenzae is estimated to be equal with beta-lactam-sensitive Haemophilus influenzae.

Current status of bacterial resistance in the otolaryngology field: results from the Second Nationwide Survey in Japan.

The study reported here was a nationwide assessment of otitis media (466 patients with acute suppurative otitis media and 476 with chronic suppurative otitis media), sinusitis (447 with acute sinusitis and 426 with chronic sinusitis), acute tonsillitis (724 patients), and peritonsillar abscess (141 patients) performed between November 1998 and March 1999. Eighty university hospitals, 79 affiliated hospitals, and 103 general practitioners participated. Methicillin-resistant Staphylococcus aureus(MRSA) comprised 15.6% of the 786 isolated strains of S. aureus. MRSA was frequently detected in patients with suppurative otitis media, but was uncommon in those with acute tonsillitis or peritonsillar abscess, and it was more common in those who had already been treated than in those who had not, with a significant difference between the groups. Vancomycin (VCM) showed the highest antimicrobial activity against MRSA and no VCM resistance was detected. Penicillin-sensitive Streptococcus pneumoniae(PSSP), penicillin-intermediate-resistant S. pneumoniae (PISP), and penicillin-resistant S. pneumoniae (PRSP) accounted for 49.6%, 28.5%, and 21.9% of the 228 isolated strains of S. pneumoniae, respectively. PISP and PRSP were frequently detected in children aged 5 years or younger. beta-Lactamase was produced by 96 of the 100 strains (96%) of Moraxella (Branhamella) catarrhalis. The 281 strains of Haemophilus influenzae isolated consisted of 199 beta-lactamase-negative, ampicillin-sensitive (BLNASe) strains (70.8%), 65 beta-lactamase-negative ampicillin-resistant (BLNAR) strains (23.1%), and 17 beta-lactamase-producing strains (6.0%). BLNAR strains were frequently detected in pretreated patients. Of these 281 strains of H. influenzae, 214 had nontypable capsules. In conclusion, the major bacterial species showed resistance to beta-lactams, indicating that care should be taken when selecting an appropriate antimicrobial agent.

Pharmacodynamics of ampicillin-sulbactam in an in vitro infection model against Escherichia coli strains with various levels of resistance.

The activity of ampicillin-sulbactam against beta-lactamase-producing Escherichia coli has been questioned. Therefore, in this study, the killing activity of ampicillin-sulbactam was investigated in an in vitro infection model which simulates human pharmacokinetics. One ampicillin-sensitive strain (E. coli ATCC 25922, ampicillin-sulbactam MIC = 4/2 microg/ml) and three ampicillin-resistant TEM-1-producing strains with various levels of ampicillin-sulbactam resistance (EC11, MIC = 4/2 microg/ml; TIM2, MIC = 12/6 microg/ml; and GB85, MIC > 128/64 microg/ml) were studied. The E. coli strains were exposed to ampicillin-sulbactam at a starting inoculum of 6 to 7 log10 CFU/ml. Ampicillin-sulbactam was infused over 30 min to simulate doses of 3 and 1.5 g every 6 h for 24 h. The 3-g ampicillin-sulbactam dose was bactericidal against E. coli ATCC 25922, EC11, and TIM2. The 1.5-g dose displayed bactericidal activity against ATCC 25922 and EC11 similar to that of the higher dose but failed to kill TIM2 due to inadequate time above the MIC and increased MICs over 24 h. GB85 was highly resistant and grew similarly to controls. Despite an MIC at 10(7) CFU/ml indicating resistance (20/10 microg/ml), TIM2 was killed by the 3-g dose of ampicillin-sulbactam. Current MIC breakpoints may not adequately portray the activity of ampicillin-sulbactam, considering both the activity in in vitro infection models and clinical data.

Characterization and transformation of plasmid pAA-1 found in an antarctic cryptoendolithic bacterium

Sixty-three bacterial isolates from antarctic sandstone samples (Linnaeus Terrace, Asgard Range, McMurdo Dry Valleys) were screened for the presence of plasmid DNA. Twenty-seven percent of all the isolates (mainly Gram-positives) harbored one or more plasmids of low molecular mass (1.1–16.3 kb). Strain AA-341 contained plasmid pAA-1 (2.9 kb), as demonstrated by agarose gel electrophoresis and restriction endonuclease digests. This plasmid conferred resistance to chromium and ampicillin. It was not conjugative, but it could be transferred by electroporation to chromium- and ampicillin-sensitive strains AA-330, AA-338, and E. coli HB101. A restriction map of pAA-1 was constructed with HindIII, SalI, ScaI, AvaII, EcoRI, PvuII, BamHI, and DraI. Electrotransfer of this plasmid from E. coli HB101(pAA-1) to strain AA-330 was demonstrated. By natural genetic transformation, plasmid pAA-1 could be transferred into the sensitive strain AA-334, which thereby became resistant to chromium and ampicillin. The importance of such processes for the colonization of stressed environments is discussed.Key words: Antarctica, cryptoendolithic bacteria, plasmids, resistance to chromium, natural transformation.

Antibiotic resistant gram-negative bacteria in rural groundwater supplies

More than 250 coliform and noncoliform bacteria, isolated by standard membrane filtration methods from rural, untreated groundwater supplies, were examined for resistance to 16 antibiotics. All of the noncoliforms and 87% of the coliforms were resistant to at least one antibiotic, with resistance most commonly directed toward novobiocin, cephalothin, and ampicillin. The frequency of multiple antibiotic resistance (MAR) within each species was also determined. Approximately 60% of the coliforms were MAR, including 14, 64, and 94% of Escherichia coli, Citrobacter freundii, and Enterobacter cloacae isolates, respectively. In comparison, MAR was demonstrated by more than 95% of the noncoliforms and included isolates of Acinetobacter calcoaceticus, Aeromonas hydrophila, and Serratia marcescens. Ampicillin-resistant environmental isolates were assayed for ability to transfer resistance to ampicillin-sensitive strains of E. coli and Salmonella typhimurium. Environmental E. coli isolates were capable of in vitro transfer to both recipients in a nutrient-rich environment (trypticase soy broth) at frequencies ranging from 1.1 × 10 −5 to 1.0 × 10 −4. Isolates of C. freundii and Klebsiella pneumoniae exhibited resistance transfer to the E. coli recipient under similar conditions at reduced rates. None of the environmental isolates demonstrated transfer of ampicillin resistance when placed in an environment containing filter-sterilized well water. The presence of antibiotic resistant bacteria, and particularly MAR bacteria, in rural groundwater supplies used as drinking water sources may have important public health implications.

The biologic activities of peptidoglycan in experimental Haemophilus influenzae meningitis.

While gram-positive bacterial cell walls are known to incite inflammation, the contribution of gram-negative peptidoglycan to disease has not been characterized. The ability of cell wall, purified peptidoglycan, and soluble peptidoglycan subcomponents from Haemophilus influenzae to provoke inflammation was determined in a rabbit model of meningitis. Haemophilus peptidoglycan, with or without associated proteins, produced brain edema at > or = 0.1 micrograms/mL of cerebrospinal fluid (CSF); leukocytosis and protein accumulation in CSF occurred only at > or = 10.0 micrograms/mL of CSF. Solubilized peptidoglycan was 10-fold more active than intact cell wall. The bioactivity of peptidoglycan from ampicillin-resistant H. influenzae was at least twofold greater than that of ampicillin-sensitive strains. Consistent with these pathologic effects of purified peptidoglycan, ampicillin-induced bacterial lysates in which endotoxin was neutralized induced brain edema and protein influx but little leukocytosis. Thus, peptidoglycan seems to contribute to the pathology of gram-negative meningitis, particularly brain edema.

Therapy of multidrug resistant typhoid in 58 children.

Treatment of children with infections caused by Salmonella typhi strains resistant to the commonly used oral antimicrobials is a special problem. As children cannot be treated with quinolones, there is no form of oral therapy. Third generation cephalosporins, which have been shown to be effective against typhoid caused by ampicillin sensitive strains of S. typhi were effective against typhoid caused by ampicillin, chloramphenicol and sulfamethoxazole/trimethoprim-resistant strains. We treated 28 children with ceftriaxone and 8 with cefotaxime. We found ceftriaxone to be more effective than cefotaxime with significantly lower relapse rate. Antibiotic therapy of 19 other children, initially treated in a similar manner, was altered for ease of therapy or due to poor response to therapy. The high cost of this parenteral therapy and the problems in its delivery point to the need for safe, effective oral therapy.

Beta-lactamase types and beta-lactam resistance ofEscherichia coli strains with chromosomally mediated ampicillin resistance

On the basis of isoelectric focusing six beta-lactamase types could be distinguished in ampicillin-resistant and ampicillin-sensitive strains of Escherichia coli. More than 90% of the ampicillin-resistant strains produced the same beta-lactamase type. The serotypes found in a group of ampicillin-resistant urinary tract infection strains did not represent the distribution usually found in urinary tract isolates. Chromosomal ampicillin resistance was always associated with high cephalothin MIC values and increased resistance to other beta-lactam antibiotics of the cephalosporin group.

The efficacy of sulbactam-ampicillin in the therapy of respiratory disease associated with ampicillin resistant Pasteurella species in housed calves.

Sulbactam-ampicillin is a combination of sulbactam, a beta-lactamase inhibitor, and ampicillin, a broad spectrum beta-lactam antibiotic. The efficacy of sulbactam-ampicillin was evaluated in the treatment of calf respiratory disease associated with ampicillin-sensitive and ampicillin-resistant strains of Pasteurella haemolytica and Pasteurella multocida. Treatment with sulbactam-ampicillin was compared with treatment with ampicillin alone in 123 Friesian calves, between three and five weeks old, exhibiting clinical signs of respiratory disease. Seven of the 59 calves treated with ampicillin died whereas only one death occurred in the 64 calves treated with sulbactam-ampicillin. In the calves which survived, treatment with sulbactam-ampicillin resulted in a significantly better clinical response, as measured by the reduction in severity of clinical signs. The results of bacteriological examinations indicated that there was a marked increase in the proportion of ampicillin-resistant isolates of P haemolytica subsequent to treatment with ampicillin, whereas the proportion of ampicillin-resistant isolates of P. haemolytica recovered from calves treated with sulbactam-ampicillin had declined. The superior efficacy of sulbactam-ampicillin observed in this study is explained by the inhibitory effect of sulbactam on beta-lactamases produced by resistant bacteria, thus rendering them susceptible to the ampicillin.

Analysis of the relationship between ampicillin resistance and beta-lactamase production in Branhamella catarrhalis.

23 strains of Branhamella catarrhalis, mainly isolated from patients with acute exacerbations of chronic bronchitis, were studied. The strains were selected on the basis of a positive beta-lactamase reaction using the cefinase disc or the nitrocefin method. No bands were visible by isoelectric focusing of the crude enzyme extracts of strains showing a weak positive reaction with the cefinase method. In the 15 remaining strains, at least 6 different isoelectric focusing patterns could be detected. Four strains showed a pattern similar to that of the Ravasio strain, the most common type in a previous study. The most prevalent type in this study, present in 5 strains, demonstrated an isoelectric focusing pattern quite different from those described so far: a main band at pI 5.28 and 2 minor bands at pI 5.71 and 6.37. Two beta-lactamase-positive, but ampicillin-sensitive strains (MIC = 0.064 mg/L) showed different isoelectric focusing patterns, pI = 4.93 and 5.43, respectively, but similar substrate profiles.