Haemophilus species, as a urinary tract pathogen, is rarely encountered. Routine urine culture pathogens are well documented to include Enterobacteriaciae, Enterococcus spp., Staphylococcus spp., Pseudomonas spp., and Candida spp. Pathogens encountered rarely in this context may include Corynebacterium ureolyticus and nonfermenting gram negative bacilli. This case study involves the finding of Haemophilus influenzae in a urine culture performed on a 4-year-old Caucasian girl and Haemophilus parinfluenzae in a 60-year-old African American man with pyelonephritis. Visualization of satellite colonies on blood agar was a key factor in finding H. influenza. Awareness of the previous presence of Haemophilus spp. in a urine culture was instrumental in our finding of H. parainfluenzae 3 weeks later. These cases raise the question of how often Haemophilus spp. occur as urinary tract pathogens and under what circumstances one should actively perform cultures for them.
Haemophilus species, as a urinary tract pathogen, is rarely encountered.1‐3 Routine urine culture pathogens are well documented to include Enterobacteriaciae, Enterococcus spp., Staphylococcus spp., Pseudomonas spp., and Candida spp. Pathogens encountered rarely in this context may include Corynebacterium ureolyticus and nonfermenting gram negative bacilli. In this article, we present 2 case reports, one of Haemophilus influenzae in a 4-year-old Caucasian girl and the other of Haemophilus parinfluenzae in a 60-year-old African American man.
Case Reports
Satelliting colonies on BLD agar plate from 4 year old female.
After incubation, there was a small amount of additional growth adjacent to the Staphylococcus spp. streak. The original urine specimen had been discarded; as a result, direct plating to a CHOC for colony count was not possible. The CHOC grew colonies typical of Haemophilus spp. The colonies were identified as Haemophilus influenzae by the RapID NH kit (Thermo Fisher Scientific.) BBL Cefinase disc (Becton Dickinson and Company [BD]) testing yielded a negative result for beta lactamase production. A Kirby-Bauer susceptibility test was set up using BBL Haemophilus Test Media Agar (BD) and was incubated overnight in 5% CO2 at 35°C. The susceptibility test yielded the following results: the organism was susceptible to ampicillin, azithromycin, cefaclor, cefuroxime, and trimethoprim sulfamethoxazole.
The treating physician for this patient was informed of the unusual nature of this organism that was causing a UTI. This was the first known UTI experienced by the patient, and the physician stated that this patient had no known urinary tract abnormality.1,-3 No urinalysis results were available. The patient had not yet been prescribed antibiotics. We requested a new urine specimen so we could plate to CHOC for a colony count and reisolation of the organism; however, no additional specimen was received. A follow-up call to the physician yielded no response regarding the treatment that the patient had received or any recurrence of the UTI.
The second case involves a 60-year-old African American man with a history of kidney cancer.4 The urinalysis results showed greater than 182 white blood cells/low power field (WBC/LPF), a positive result for nitrates, and the presence of 1+ protein. The preliminary plate reading showed no growth on BLD, MacConkey's agar (MAC), and cysteine naladixic acid agar (CNA). The plates were returned to the incubator for further incubation.
Hemophilus parainfluenzae on BLD agar plate from 50 year old male.
The organism was then subcultured to CHOC and incubated in 5% CO2 at 35°C overnight. The CHOC grew colonies typical of Haemophilus spp. RapID NH kit testing was performed, and the organism was identified as Haemophilus parainfluenzae. Susceptibility testing was performed. The organism was susceptible to ampicillin, azithromycin, cefaclor, cefuroxime, and ciprofloxacin. It showed intermediate resistance to tetracycline and resistance to trimethoprim sulfamethoxazole. The patient was originally prescribed Bactrim but was switched to ciprofloxacin 500 mg twice daily for 20 days. At the next follow-up appointment, the infection had been resolved.
Discussion
Routine urine culture protocol at our laboratory includes a BLD/MAC split plate and a CNA agar inoculated with 1 µL of urine and incubated for a minimum of 18 hours. CHOC agar is not included in our protocol, although it provides the necessary nutrients to support the growth of Haemophilus spp. If pinpoint-sized colonies are observed on the plates, they will be incubated further to ensure the visualization of slower-growing pathogens, such as yeast, nonfermenting gram-negative bacilli, and Gardnerella vaginalis.
Urine specimens are held for 3 days in our laboratory so they are available for additional testing if necessary. This period of time proved to be inadequate because the identification was slowed by the lack of experience with this organism as extracted from urine. If we had still had the urine specimen, we would plate it on CHOC to get an accurate colony count.
H. influenzae requires X factor (hemin) and V factor (nicotinamide adenine dinucleotide [NAD]) for growth. H. influenzae obtains X factor from blood and NAD from Staphylococcus spp. metabolism byproducts and will exhibit satelliting where these substances are present. H. parainfluenzae requires NAD but not X factor.5
Satelliting colonies should be tested for Haemophilus spp. The incidence of Haemophilus spp. in UTIs may be underestimated in our laboratory due to the fact that our initial inoculation media does not include a CHOC that would enhance the isolation of that species.6‐9 Studies estimate the occurrence of Haemophilus spp. as a UTI pathogen to be less than 1%.1,3,4,7 Previous studies point to increase incidence of Haemophilus spp. urinary tract anomalies in children1‐3; men with epididymitis, prostatitis, urethritis, or renal calculi7‐8; and women with urogenital manipulation.10 The cases presented herein do not fall into these categories. This fact leads to the question of how to narrow our search criteria for Haemophilus spp. in urine cultures. Routine screening would be prohibitively expensive.4
We opine that in cases of a suspected and/or recurrent UTI with a negative urine culture result, with or without urinary tract abnormalities, further investigation may be indicated. If the urinalysis indicates a UTI (ie, leukocyturia and positive nitrates), plating the urine specimen to CHOC agar plate may increase the isolation of Haemophilus spp. and more accurately reflect the true incidence of this species in UTIs.4,7,9‐11
References
Abbreviations
- BLD
Blood agar plate
- C°
degrees Centigrade
- CFU
colony forming unit
- CHOC
chocolate agar plate
- CNA
cysteine naladixic acid agar plate
- CO2
carbon dioxide
- H. influenzae
Haemophilus influenzae
- H. parainfluenzae
Haemophilus parainfluenzae
- LPF
low power field
- MAC
MacConkey agar plate
- NAD
nicotinamide adenine dinucleotide
- UTI
urinary tract infection
- WBC
white blood cells
