Emergence of Haemophilus influenzae with low susceptibility to quinolones isolated from pediatric patients in Japan

IntroductionIn 2010, oral fluoroquinolone tosufloxacin (TFX) granules were released as the first oral respiratory quinolone for children in Japan.MethodsTo investigate the recent trend of H. influenzae strains with low susceptibility to quinolones in children, we analyzed the gene sequences of quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC, and parE of 23 clinical isolates from 15 patients aged <15 years with an MIC of ≥0.5 μg/mL for TFX from 2010 to 2018.ResultsAmino acid substitutions were observed in both GyrA and ParC in 13 strains (81%, 13/16), except two strains with a TFX MIC of 0.5 μg/mL with amino acid substitution in only GyrA and one strain with a TFX MIC of 1 μg/mL with no amino acid substitution. Four ST422 strains were observed in 2018, the detection age range was wide (0–7 years), and the residential city was varied. A total of 3/15 patients had a clear history of TFX treatment.ConclusionsEven for the strain with an MIC of 0.5 μg/mL for TFX, it is highly possible that it harbors a mutation in gyrA, which is the first step toward quinolone resistance, and it may also harbor mutations in both gyrA and parC. Furthermore, several specific sequence type quinolone-resistant H. influenzae strains, particularly ST422, may be widespread among children in Japan. It is necessary to investigate changes in resistance both at the MIC and gene levels. The continuous monitoring of strains and the use of antimicrobial drugs in treatment should be carefully observed.     

Characterization of the inoculum effect with Haemophilus influenzae and β-lactams

An inoculum effect is defined as a four-fold or greater increase in MIC with an increase in bacterial inocula. Haemophilus influenzae was tested for an inoculum effect with ampicillin, cefuroxime, and amoxicillin/clavulanate using the standard initial inocula (5 × 10⁵ CFU/mL) and a higher initial inocula (1 × 10⁷ CFU/mL). An inoculum effect was observed with both β-lactamase (TEM-1, ROB-1) positive and β-lactamase negative strains of H. influenzae when MICs were determined based on turbidity. MICs based on viable cell counts however, demonstrated that only β-lactamase positive strains of H. influenzae produced an inoculum effect. These observations suggest that MICs determined based on turbidity, using high initial inocula, are not reliable when examining the inoculum effect in H. influenzae. The magnitude of the inoculum effect with β-lactamase positive strains was β-lactam dependent (ampicillin > amoxicillin/clavulanate > cefuroxime). β-lactam kill-curves confirmed the aforementioned results. Addition of the β-lactamase inhibitor clavulanate completely reversed the inoculum effect in β-lactamase (TEM-1 and ROB-1) positive strains of H. influenzae with all β-lactams tested. Introduction of the β-lactamase gene TEM-1 on plasmid vector pLS88 into a β-lactamase negative strain of H. influenzae (Rd) produced an inoculum effect based on viable cell counts. In conclusion, our results suggest that the β-lactam inoculum effect demonstrated by H. influenzae is the result of β-lactamase production and is poorly assessed by turbidity.     

Nosocomial infections caused by vancomycin-resistant Enterococcus in a Japanese general hospital and molecular genetic analysis

IntroductionVancomycin-resistant Enterococcus (VRE) is a rare bacterium in Japan, but an outbreak due to nosocomial transmission in medical facilities has been reported in recent years. Here, we report the outbreak of vanA vancomycin-resistant Enterococcus faecium (VREfm) in multiple wards of Nara Prefectural General Medical Center in 2019 and results of the molecular epidemiology analysis.MethodsAn aggressive screening program was conducted after the first VREfm was detected in a patient in the A ward. During the outbreak, 6000 rectal swab samples were screened for VRE by culture. Isolates from 60 patients with VREfm detected were clustered using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).ResultsPFGE revealed a cluster consisting of three major clusters and four multi-strains. The first major cluster consisted of 26 isolates, the second consisted of 10 isolates, the third consisted of 6 isolates, and the remaining 4 clusters consisted of 2 isolates. MLST identified an allele profile (ST80) in most clusters of clone types P01–P06 but an allele profile (ST992) in cluster P07.ConclusionBased on the PFGE pattern, this case was considered to be a nosocomial infection due to multiple clones. Later, in addition to screening, sharing of hospital information, cohorting of patients and staff, and strengthening of environmental cleanup were carried out, and horizontal infection was suppressed.     

Clonality investigation of clinical Escherichia coli isolates by polymerase chain reaction-based open-reading frame typing method

Escherichia coli (E. coli) causes urinary tract infections, pneumonia, surgical site infections, and bloodstream infections and is the important pathogen for both community-acquired and healthcare-associated infections. To investigate the clonality of E. coli is important for infection control and prevention. We aimed to investigate the clonality of clinical E. coli isolates using Cica Geneus E. coli polymerase chain reaction (PCR)-based open-reading frame typing (POT) KIT and clarify the clinical usefulness of this kit. About 124 E. coli isolates obtained from inpatients at Sapporo Medical University Hospital were used. The POT method was used to classify 124 clinical isolates into 87 POT numbers. In addition to the clonality, it was possible to obtain additional information that 20 of the 124 isolates were extended-spectrum β-lactamase (ESBL) producing E. coli (5 isolates of CTX-M-1 group and 15 isolates of CTX-M-9 group) and 13 were sequence type (ST) 131 clone. Furthermore, when these ESBL-producing 20 isolates were compared with pulsed-field gel electrophoresis (PFGE) or multilocus sequence typing (MLST), Simpson's index of diversity was 0.968 in POT method, 0.979 in PFGE, and 0.584 in MLST. POT method had an analytical power similar to that of PFGE. In conclusion, attention should be paid to the difference in the interpretation of the results between the POT method and the PFGE, but POT method may be useful to timely monitor the spread of E. coli in medical facilities.     

Nationwide surveillance of bacterial respiratory pathogens conducted by the surveillance committee of japanese society of chemotherapy,the japanese association for infectious diseases,and the japanese society for clinical microbiology in 2016: General view of the pathogens’ antibacterial susceptibility

The nationwide surveillance on antimicrobial susceptibility of bacterial respiratory pathogens from the patients in Japan was conducted by the Japanese Society of Chemotherapy, the Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology in 2016.The isolates were collected from clinical specimens obtained from well-diagnosed adult patients with respiratory tract infections during the period between February 2016 and August 2016 by three societies. Antimicrobial susceptibility testing was conducted at the central reference laboratory according to the method recommended by Clinical Laboratory Standards Institute.Susceptibility testing was evaluated in 1062 strains (143 Staphylococcus aureus, 210 Streptococcus pneumoniae, 17 Streptococcus pyogenes, 248 Haemophilus influenzae, 151 Moraxella catarrhalis, 134 Klebsiella pneumoniae, and 159 Pseudomonas aeruginosa). Ratio of methicillin-resistant S. aureus was 48.3%, and those of penicillin-susceptible S. pneumoniae was 99.5%. Among H. influenzae, 14.1% of them were found to be β-lactamase-producing ampicillin-resistant strains, and 41.1% to be β-lactamase-non-producing ampicillin-resistant strains. Extended spectrum β-lactamase-producing K. pneumoniae and multi-drug resistant P. aeruginosa with metallo β-lactamase were 4.5% and 0.6%, respectively.     

A survey of β-lactamase-producing Haemophilus influenzae an evaluation of 5750 isolates

Previous studies have reported that 15%–34% of Haemophilus influenzae produce β-lactamase. A surveillance program was developed by SmithKline Beecham Clinical Laboratories to determine the current percentage of β-lactamase-producing H. influenzae from five selected geographic locations in the United States. In 1993, results of 5750 isolates from specimens submitted to five reference clinical laboratories were evaluated. Data were collected from 29 states and the District of Columbia. The percentages of β-lactamase-producing H. influenzae was 33% and ranged from 22%–40% for the individual states.     

Highlights of the French antimicrobial resistance surveillance project

Thirty-three French laboratories took part in a study to determine the frequency of antibiotic resistance to S. pneumoniae, H. influenzae and M. catarrhalis in different regions of the country. A total of 1317 bacterial isolates were studied. The level of resistance to penicillin among isolates of S. pneumoniae was high particularly in children with otitis media or upper respiratory tract infections. In H. influenzae isolates the level of β-lactamase production was over 30% in all groups of patients and specimen types and in M. catarrhalis the level of β-lactamase production was in excess of 90%. Multidrug resistance was found often among the macrolides, tetracyclines, and trimethoprim/sulfamethoxazole, and these antimicrobials should not be regarded as therapeutic alternatives to the β-lactams.     

A molecular analysis of quinolone-resistant Haemophilus influenzae: Validation of the mutations in Quinolone Resistance-Determining Regions

The mechanism of quinolone-resistance is considered to be amino acid mutations in the type II topoisomerase. We validated the genetic mechanisms of quinolone resistance in Haemophilus influenzae.We obtained 29 H. influenzae strains from a nationwide surveillance program in Japan (including 11 quinolone-resistant strains [moxifloxacin: MFLX or levofloxacin MIC ≥2 μg/ml]). We analyzed the sequences of the Quinolone Resistance-Determining Regions (QRDRs) in GyrA, GyrB, ParC and ParE. Furthermore, we induced resistance in susceptible strains by exposing them to quinolone, and investigated the relationship between mutations in the QRDRs and the MICs.Five amino acid substitutions in GyrA (at Ser84 and Asp88) and ParC (at Gly82, Ser84 and Glu88) were found to be closely related to the MICs. The strains with a MFLX MIC of 0.125–1 and 2–4 μg/ml had one and two mutations, respectively. The strains with a MFLX MIC of ≥8 μg/ml had three or more mutations. The strains with induced resistance with MFLX MICs of 0.5–1 and ≥2 μg/ml also had one and two mutations, respectively.We confirmed that these five mutations strongly contribute to quinolone resistance and found that the degree of resistance is related to the number of the mutations. In addition, the three strains of 18 susceptible strains (16.7%) also had a single mutation. These strains may therefore be in the initial stage of quinolone resistance. Currently, the frequency of quinolone-resistant H. influenzae is still low. However, as has occurred with β-lactams, an increase in quinolone use may lead to more quinolone-resistant strains.     

Genetic characteristics of Haemophilus influenzae and Streptococcus pneumoniae isolated from children with conjunctivitis-otitis media syndrome

Acute conjunctivitis is the most common ocular disorders among children and frequently concomitant with acute otitis media (AOM) as conjunctivitis-otitis syndrome. In this study, we evaluated prevalence of causative pathogens and PCR-based genotypes of Haemophilus influenzae and Streptococcus pneumoniae among children with conjunctivitis-otitis media syndrome. Nontypeable H. influenzae (NTHi) is identified most often at 61.8% in conjunctiva exudates followed by S. pneumoniae at 28.2% and Moraxella catarrhalis at 19.1%. Genetic β-lactamase nonproducing ampicillin resistant (gBLNAR) strains of NTHi and genetic penicillin resistant S. pneumoniae (gPRSP) were identified at 72.1% and at 74.2% among conjunctiva isolates by polymerase chain reaction (PCR), respectively. Pneumococcal strains having either ermB or mefE genes were identified at 93.5% among conjunctiva isolates. The restriction fragment of patterns of 89.7% pairs of H. influenzae isolates and 100% pairs of pneumococcal isolates from conjunctiva exudates, middle ear fluids (MEFs) and nasopharyngeal swabs were identical.In contrast to the previous reports, most prevalent strains from conjunctivitis-otitis media syndrome was BLNAR H. influenzae in this study. The causative pathogen responsible for acute conjunctivitis will be originated from the nasopharynx. In the absence of MEFs one can possibly rely on the nasopharyngeal culture to guide an appropriate treatment.     

Iodometric Detection of Haemophilus influenzae Beta-Lactamase: Rapid Presumptive Test for Ampicillin Resistance

Strains of Haemophilus influenzae type b sporadically isolated from clinical specimens are ampicillin resistant due to production of a β-lactamase. This enzyme which inactivates ampicillin and penicillin G is not produced by ampicillin-susceptible strains. Various characteristics of β-lactamase production and ampicillin resistance of three H. influenzae type b isolates were investigated. A sensitive iodometric test was employed to detect β-lactamase; positive results were obtained in 5 min with 10⁹ bacteria taken from cultures on a nutritionally adequate agar medium. This simple chemical test will enable the hospital laboratory to obtain presumptive evidence of ampicillin resistance on the same day that H. influenzae is isolated.     

Nationwide surveillance of bacterial respiratory pathogens conducted by the surveillance committee of Japanese Society of Chemotherapy,the Japanese Association for Infectious Diseases,and the Japanese Society for clinical microbiology in 2014: General view of the pathogens' antibacterial susceptibility

The nationwide surveillance on antimicrobial susceptibility of bacterial respiratory pathogens from the patients in Japan was conducted by Japanese Society of Chemotherapy, the Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology in 2014.The isolates were collected from clinical specimens obtained from well-diagnosed adult patients with respiratory tract infections during the period between January 2014 and April 2015 by three societies. Antimicrobial susceptibility testing was conducted at the central reference laboratory according to the method recommended by Clinical Laboratory Standards Institute.Susceptibility testing was evaluated in 1534 strains (335 Staphylococcus aureus, 264 Streptococcus pneumoniae, 29 Streptococcus pyogenes, 281 Haemophilus influenzae, 164 Moraxella catarrhalis, 207 Klebsiella pneumoniae, and 254 Pseudomonas aeruginosa). Ratio of methicillin-resistant S. aureus was 43.6%, and those of penicillin-susceptible S. pneumoniae was 100%. Among H. influenzae, 8.2% of them were found to be β-lactamase-producing ampicillin-resistant strains, and 49.1% to be β-lactamase-non-producing ampicillin-resistant strains. Extended spectrum β-lactamase-producing K. pneumoniae and multi-drug resistant P. aeruginosa with metallo β-lactamase were 9.2% and 0.4%, respectively.     

Identification of a novel Acinetobacter baumannii clone in a US hospital outbreak by multilocus polymerase chain reaction/electrospray-ionization mass spectrometry

We investigated the relatedness of multidrug-resistant Acinetobacter baumannii isolates from a burn intensive care unit (BICU) outbreak, control isolates, and isolates from a previous 2007 outbreak by 3 molecular typing methods (repetitive sequence-based polymerase chain reaction [rep-PCR], broad-range PCR and electrospray ionization mass spectrometry [PCR/ESI-MS], and pulsed-field gel electrophoresis [PFGE]). Partial rpoB gene sequencing confirmed all tested isolates as A. baumannii. Molecular typing analysis showed that 17 of 19 outbreak isolates were indistinguishable or closely related to each other. Three of 4 non-BICU outbreak control isolates and 5 of 6 isolates from the previous outbreak closely matched the BICU outbreak genotype. The outbreak strain represented a novel strain type, ST96, on PCR/ESI-MS with a new combination of alleles not previously seen in the United States. The ST96 strain also represented a novel rpoB Seqtype. Results of PCR/ESI-MS and PFGE genotyping were most closely correlated, while rep-PCR and PCR/ESI-MS systems generated rapid results.     

Increase in Quinolone Resistance in a Haemophilus influenzae Strain Isolated from a Patient with Recurrent Respiratory Infections Treated with Ofloxacin

The increase in the level of quinolone resistance of Haemophilus influenzae clinical isolates during ofloxacin therapy of a patient with recurrent respiratory infections was investigated. The first isolate (MIC of ciprofloxacin of 2 μg/ml) and the second isolate (MIC of 32 μg/ml) belonged to the same clone, as shown by pulsed-field gel electrophoresis, and the increase in the resistance level was associated with a substitution in Ser-84 to Arg in the ParC protein. These results emphasize the potential risk of development of quinolone-resistant H. influenzae during fluoroquinolone therapy in patients with recurrent respiratory infection.     

Nontypeable Haemophilus influenzae susceptibility: Effect of inoculum size and β-lactamase production

The activities of cefixime, cefpodoxime, cefprozil, cefuroxime, loracarbef, and amoxicillin/clavulanate against 72 clinical isolates of nontypeable Haemophilus influenzae were determined by using an agar dilution method. The effects of β-lactamase production and bacterial inoculum size were investigated. All antimicrobials exhibited a significant inoculum effect, demonstrating the importance of accurately determining inoculum size in the performance of antimicrobial susceptibility testing of H. influenzae.     

Nationwide surveillance of bacterial pathogens isolated from children conducted by the surveillance committee of Japanese Society of Chemotherapy,the Japanese Association for Infectious Diseases,and the Japanese Society for Clinical Microbiology in 2017: General overview of pathogenic antimicrobial susceptibility

A nationwide surveillance of the antimicrobial susceptibility of pediatric patients to bacterial pathogens was conducted by Japanese Society of Chemotherapy, the Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology in Japan in 2017. The isolates were collected from 18 medical facilities between March 2017 and May 2018 by the three societies. Antimicrobial susceptibility testing was conducted at the central laboratory (Infection Control Research Center, Kitasato University, Tokyo) according to the methods recommended by the Clinical Laboratory Standards Institute. Susceptibility testing was evaluated in 926 strains (331 Streptococcus pneumoniae, 360 Haemophilus influenzae, 216 Moraxella catarrhalis, 5 Streptococcus agalactiae, and 14 Escherichia coli). The ratio of penicillin-resistant S. pneumoniae was 0% based on CLSI M100-ED29 criteria. However, three meropenem or tosufloxacin resistant S. pneumoniae isolates were obtained. Among H. influenzae, 13.1% of them were found to be β-lactamase-producing ampicillin resistant strains, while 20.8% were β-lactamase non-producing ampicillin-resistant strains. No capsular type b strains were detected. In M. catarrhalis, 99.5% of the isolates were β-lactamase-producing strains. All S. agalactiae and E. coli strains were isolated from sterile body sites (blood or cerebrospinal fluid). The ratio of penicillin-resistant S. agalactiae was 0%, while that of extended spectrum β-lactamase-producing E. coli was 14.3%.     

Reducing the urine collection rate could prevent hospital-acquired horizontal transmission of multidrug-resistant Pseudomonas aeruginosa

IntroductionMultidrug-resistant Pseudomonas aeruginosa (MDRP) is a waterborne pathogen that occasionally causes hospital-acquired infection in immunocompromised or critically ill patients. Urine is frequently collected to evaluate renal function or to perform hormonal examinations, but the procedure involves risk due to the possibility of healthcare workers with contaminated hands. Our objective was to evaluate the association between the urine collection and hospital-acquired horizontal transmission of MDRP.MethodsWe monitored the urine collection rate from 2011 to 2017, as part of ongoing efforts to reduce the need to collect urine. The urine collection rate and the frequency of isolation of MDRP, Methicillin resistant S. aureus (MRSA) and extended spectrum β-lactamases (ESBL)-producing E. coli were analyzed during the same period. PFGE and MLST were also performed to analyze the identity of 5 MDRP strains detected on the same ward in 2014–2015.ResultsThe urine collection rate was dramatically decreased from 4.8% in 2011 to less than 0.5% in 2017, because the isolation rate of MDRP was significantly positively associated (RR = 1.72, 95%CI:1.03–2.85) with the urine collection rate. Isolations of MRSA and ESBL-producing E. coli showed no significant. Molecular typing showed the PFGE patterns of 3 of 5 MDRP strains were closely related as did MLST (ST17), and the remaining 2 MDRP strains had different PFGE and MLST patterns (ST14, ST655). Our data implicated the urine collection as one of the causes of hospital-acquired MDRP infections.ConclusionsWe concluded that a reducing the urine collection rate could contribute to preventing hospital-acquired horizontal transmission of MDRP.     

Prevalence of Haemophilus influenzae with resistant genes isolated from young children with acute lower respiratory tract infections in Nha Trang, Vietnam

Our study was undertaken to investigate the characteristics of Haemophilus influenzae in young children with acute lower respiratory tract infections in Nha Trang, Vietnam. The study population consisted of 116 children less than 5 years of age admitted to Khanh Hoa General Hospital due to acute lower respiratory tract infections between July 2004 and April 2005. Organisms could be detected from nasopharyngeal swabs (NP) in 72 (62.1%) of the 116 children. Haemophilus influenzae was the most common organism, and 39 strains were isolated from 39 children aged 2 to 60 months (mean age, 16 months). We examined 37 of these 39 H. influenzae strains. The serotypes of the 37 isolates were all nontypeable, and 22 strains (59.5%) were β-lactamase producing. Polymerase chain reaction (PCR) analysis to identify resistance genes revealed that 17 strains had the TEM-1-type β-lactamase gene alone, 6 strains had the ftsI gene with the same substitution as that in g low-β-lactamase-negative ampicillin-resistant (g low-BLNAR) strains, and 6 strains had both the TEM-1-type β-lactamase gene and the ftsI gene with the same substitution as that in g β-lactamase-producing amoxicillin clavulanic acid-resistant (g BLPACR I) strains, although no BLNAR strains were found. Molecular typing by pulsed-field gel electrophoresis (PFGE) showed that the 6 g low-BLNAR strains had five PFGE patterns and the 6 g BLPACR I strains had four PFGE patterns. Our results indicate that BLNAR strains are still not prevalent, but that g low-BLNAR and g BLPACR I strains are potentially spreading in Nha Trang, Vietnam.     

Nationwide surveillance of bacterial respiratory pathogens conducted by the surveillance committee of the Japanese Society of Chemotherapy,the Japanese Association for Infectious Diseases,and the Japanese Society for Clinical Microbiology in 2019–2020: General view of the pathogens' antibacterial susceptibility

The trends and prevalence of antimicrobial susceptibility of pathogens vary by country, region, and time. Long-term regular surveillance is required to investigate trends in the antimicrobial resistance of various isolated bacterial pathogens. We report the results of a nationwide surveillance on the antimicrobial susceptibility of bacterial respiratory pathogens in Japan conducted by the Japanese Society of Chemotherapy, the Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology. The isolates were collected from clinical specimens obtained from adult patients who visited a collaborating medical facility between June 2019 and December 2020 and were diagnosed with respiratory tract infections by a physician. Antimicrobial susceptibility testing was performed in a centralized laboratory according to the methods recommended by the Clinical and Laboratory Standards Institute.Susceptibility testing was performed for 932 strains (201 Staphylococcus aureus, 158 Streptococcus pneumoniae, 6 S. pyogenes, 136 Haemophilus influenzae, 127 Moraxella catarrhalis, 141 Klebsiella pneumoniae, and 163 Pseudomonas aeruginosa) collected from 32 facilities in Japan. The proportions of methicillin-resistant S. aureus and penicillin-resistant S. pneumoniae were 35.3% and 0%, respectively. In H. influenzae, 16.2% and 16.9% were β-lactamase-producing ampicillin resistant and β-lactamase-negative ampicillin resistant, respectively. Extended-spectrum β-lactamase-producing K. pneumoniae accounted for 5.0% of all K. pneumoniae infections. Carbapenemase-producing K. pneumoniae and multi-drug-resistant P. aeruginosa with metallo-β-lactamase were not detected in this study. This surveillance will be a useful reference for treating respiratory infections in Japan and will provide evidence to enhance the appropriate use of antimicrobial agents.     

Surveillance on susceptibility of strains isolated from pediatric infections

During the period from January to December 2015, 104 Streptococcus pneumoniae strains, 129 Haemophilus influenzae strains and 54 Moraxella catarrhalis strains isolated from clinical specimens of pediatric infections in the national 16 institutions, studied susceptibilities of total 28 antibiotics, the capsular serotype for S. pneumoniae, the capsular b type and β-lactamase production capability for H. influenzae, and the β-lactamase production capability for M. catarrhalis were measured.In S. pneumoniae, the results showed that 68 strains (65.4%) were PSSP, 32 (30.8%) were PISP, and 4 (3.8%) were PRSP. The susceptibilities of TBPM and GRNX among oral antibiotics, and PAPM among injectable antibiotics demonstrated the lowest value with MIC90 ≤ 0.06 μg/mL. The most frequent distribution of S. pneumoniae serotypes was seen in 15B, followed by 19A, and 35B. Serotype strains contained in 13-valent pneumococcal conjugate vaccine (PCV13) were 19 strains (18.3%).In H. influenzae, the results showed that BLNAS accounted for 40 strains (31.0%), BLNAI for 28 strains (21.7%), BLNAR for 47 strains (36.4%), β-lactamase producing for 14 strains (10.8%). The susceptibilities of quinolones demonstrated the lowest outcome among oral antibiotics with MIC90 ≤ 0.06 μg/mL, and CTRX and TAZ/PIPC (TAZ4 fixed) among injectable antibiotics with MIC of 0.25 μg/mL. There was no detection of capsular type b strains.In M. catarrhalis, all the isolates were β-lactamase producing strains. The susceptibilities of TBPM, CPFX, TFLX and GRNX among oral antibiotics, and TAZ/PIPC (TAZ4 fixed), PAPM, MEPM and DRPM among injectable antibiotics demonstrated the lowest outcome with MIC of ≤0.06 μg/mL.     

Haemophilus influenzae and Moraxella catarrhalis from Patients with Community-Acquired Respiratory Tract Infections: Antimicrobial Susceptibility Patterns from the SENTRY Antimicrobial Surveillance Program (United States and Canada, 1997)

Between February and June of 1997, a large number of community-acquired respiratory tract isolates of Haemophilus influenzae (n = 1,077) and Moraxella catarrhalis (n = 503) from 27 U.S. and 7 Canadian medical centers were characterized as part of the SENTRY Antimicrobial Surveillance Program. Overall prevalences of β-lactamase production were 33.5% in H. influenzae and 92.2% in M. catarrhalis with no differences noted between isolates recovered in the United States and those from Canada. Among a total of 21 different antimicrobial agents tested, including six cephalosporins, a β-lactamase inhibitor combination, three macrolides, tetracycline, trimethoprim-sulfamethoxazole (TMP-SMX), rifampin, chloramphenicol, five fluoroquinolones, and quinupristin-dalfopristin, resistance rates of >5% with H. influenzae were observed only with cefaclor (12.8%) and TMP-SMX (16.2%).